2017-02-23 06:32:51 +08:00
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//===- StackProtector.cpp - Stack Protector Insertion ---------------------===//
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2008-11-04 10:10:20 +08:00
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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2008-11-05 05:53:09 +08:00
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// This pass inserts stack protectors into functions which need them. A variable
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// with a random value in it is stored onto the stack before the local variables
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// are allocated. Upon exiting the block, the stored value is checked. If it's
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2008-11-04 10:10:20 +08:00
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// changed, then there was some sort of violation and the program aborts.
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//
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//===----------------------------------------------------------------------===//
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2017-11-17 09:07:10 +08:00
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#include "llvm/CodeGen/StackProtector.h"
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2013-01-23 14:43:53 +08:00
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/ADT/Statistic.h"
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2014-12-01 12:27:03 +08:00
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#include "llvm/Analysis/BranchProbabilityInfo.h"
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[stack-protection] Add support for MSVC buffer security check
Summary:
This patch is adding support for the MSVC buffer security check implementation
The buffer security check is turned on with the '/GS' compiler switch.
* https://msdn.microsoft.com/en-us/library/8dbf701c.aspx
* To be added to clang here: http://reviews.llvm.org/D20347
Some overview of buffer security check feature and implementation:
* https://msdn.microsoft.com/en-us/library/aa290051(VS.71).aspx
* http://www.ksyash.com/2011/01/buffer-overflow-protection-3/
* http://blog.osom.info/2012/02/understanding-vs-c-compilers-buffer.html
For the following example:
```
int example(int offset, int index) {
char buffer[10];
memset(buffer, 0xCC, index);
return buffer[index];
}
```
The MSVC compiler is adding these instructions to perform stack integrity check:
```
push ebp
mov ebp,esp
sub esp,50h
[1] mov eax,dword ptr [__security_cookie (01068024h)]
[2] xor eax,ebp
[3] mov dword ptr [ebp-4],eax
push ebx
push esi
push edi
mov eax,dword ptr [index]
push eax
push 0CCh
lea ecx,[buffer]
push ecx
call _memset (010610B9h)
add esp,0Ch
mov eax,dword ptr [index]
movsx eax,byte ptr buffer[eax]
pop edi
pop esi
pop ebx
[4] mov ecx,dword ptr [ebp-4]
[5] xor ecx,ebp
[6] call @__security_check_cookie@4 (01061276h)
mov esp,ebp
pop ebp
ret
```
The instrumentation above is:
* [1] is loading the global security canary,
* [3] is storing the local computed ([2]) canary to the guard slot,
* [4] is loading the guard slot and ([5]) re-compute the global canary,
* [6] is validating the resulting canary with the '__security_check_cookie' and performs error handling.
Overview of the current stack-protection implementation:
* lib/CodeGen/StackProtector.cpp
* There is a default stack-protection implementation applied on intermediate representation.
* The target can overload 'getIRStackGuard' method if it has a standard location for the stack protector cookie.
* An intrinsic 'Intrinsic::stackprotector' is added to the prologue. It will be expanded by the instruction selection pass (DAG or Fast).
* Basic Blocks are added to every instrumented function to receive the code for handling stack guard validation and errors handling.
* Guard manipulation and comparison are added directly to the intermediate representation.
* lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
* lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
* There is an implementation that adds instrumentation during instruction selection (for better handling of sibbling calls).
* see long comment above 'class StackProtectorDescriptor' declaration.
* The target needs to override 'getSDagStackGuard' to activate SDAG stack protection generation. (note: getIRStackGuard MUST be nullptr).
* 'getSDagStackGuard' returns the appropriate stack guard (security cookie)
* The code is generated by 'SelectionDAGBuilder.cpp' and 'SelectionDAGISel.cpp'.
* include/llvm/Target/TargetLowering.h
* Contains function to retrieve the default Guard 'Value'; should be overriden by each target to select which implementation is used and provide Guard 'Value'.
* lib/Target/X86/X86ISelLowering.cpp
* Contains the x86 specialisation; Guard 'Value' used by the SelectionDAG algorithm.
Function-based Instrumentation:
* The MSVC doesn't inline the stack guard comparison in every function. Instead, a call to '__security_check_cookie' is added to the epilogue before every return instructions.
* To support function-based instrumentation, this patch is
* adding a function to get the function-based check (llvm 'Value', see include/llvm/Target/TargetLowering.h),
* If provided, the stack protection instrumentation won't be inlined and a call to that function will be added to the prologue.
* modifying (SelectionDAGISel.cpp) do avoid producing basic blocks used for inline instrumentation,
* generating the function-based instrumentation during the ISEL pass (SelectionDAGBuilder.cpp),
* if FastISEL (not SelectionDAG), using the fallback which rely on the same function-based implemented over intermediate representation (StackProtector.cpp).
Modifications
* adding support for MSVC (lib/Target/X86/X86ISelLowering.cpp)
* adding support function-based instrumentation (lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp, .h)
Results
* IR generated instrumentation:
```
clang-cl /GS test.cc /Od /c -mllvm -print-isel-input
```
```
*** Final LLVM Code input to ISel ***
; Function Attrs: nounwind sspstrong
define i32 @"\01?example@@YAHHH@Z"(i32 %offset, i32 %index) #0 {
entry:
%StackGuardSlot = alloca i8* <<<-- Allocated guard slot
%0 = call i8* @llvm.stackguard() <<<-- Loading Stack Guard value
call void @llvm.stackprotector(i8* %0, i8** %StackGuardSlot) <<<-- Prologue intrinsic call (store to Guard slot)
%index.addr = alloca i32, align 4
%offset.addr = alloca i32, align 4
%buffer = alloca [10 x i8], align 1
store i32 %index, i32* %index.addr, align 4
store i32 %offset, i32* %offset.addr, align 4
%arraydecay = getelementptr inbounds [10 x i8], [10 x i8]* %buffer, i32 0, i32 0
%1 = load i32, i32* %index.addr, align 4
call void @llvm.memset.p0i8.i32(i8* %arraydecay, i8 -52, i32 %1, i32 1, i1 false)
%2 = load i32, i32* %index.addr, align 4
%arrayidx = getelementptr inbounds [10 x i8], [10 x i8]* %buffer, i32 0, i32 %2
%3 = load i8, i8* %arrayidx, align 1
%conv = sext i8 %3 to i32
%4 = load volatile i8*, i8** %StackGuardSlot <<<-- Loading Guard slot
call void @__security_check_cookie(i8* %4) <<<-- Epilogue function-based check
ret i32 %conv
}
```
* SelectionDAG generated instrumentation:
```
clang-cl /GS test.cc /O1 /c /FA
```
```
"?example@@YAHHH@Z": # @"\01?example@@YAHHH@Z"
# BB#0: # %entry
pushl %esi
subl $16, %esp
movl ___security_cookie, %eax <<<-- Loading Stack Guard value
movl 28(%esp), %esi
movl %eax, 12(%esp) <<<-- Store to Guard slot
leal 2(%esp), %eax
pushl %esi
pushl $204
pushl %eax
calll _memset
addl $12, %esp
movsbl 2(%esp,%esi), %esi
movl 12(%esp), %ecx <<<-- Loading Guard slot
calll @__security_check_cookie@4 <<<-- Epilogue function-based check
movl %esi, %eax
addl $16, %esp
popl %esi
retl
```
Reviewers: kcc, pcc, eugenis, rnk
Subscribers: majnemer, llvm-commits, hans, thakis, rnk
Differential Revision: http://reviews.llvm.org/D20346
llvm-svn: 272053
2016-06-08 04:15:35 +08:00
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#include "llvm/Analysis/EHPersonalities.h"
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2017-10-10 07:19:02 +08:00
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#include "llvm/Analysis/OptimizationRemarkEmitter.h"
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2014-01-07 19:48:04 +08:00
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#include "llvm/CodeGen/Passes.h"
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2017-11-17 09:07:10 +08:00
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#include "llvm/CodeGen/TargetLowering.h"
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2017-06-06 06:59:21 +08:00
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#include "llvm/CodeGen/TargetPassConfig.h"
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2017-11-17 09:07:10 +08:00
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#include "llvm/CodeGen/TargetSubtargetInfo.h"
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2013-01-02 19:36:10 +08:00
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#include "llvm/IR/Attributes.h"
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2017-02-23 06:32:51 +08:00
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#include "llvm/IR/BasicBlock.h"
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2013-01-02 19:36:10 +08:00
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#include "llvm/IR/Constants.h"
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#include "llvm/IR/DataLayout.h"
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2016-07-01 02:49:04 +08:00
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#include "llvm/IR/DebugInfo.h"
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2017-02-23 06:32:51 +08:00
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#include "llvm/IR/DebugLoc.h"
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2013-01-02 19:36:10 +08:00
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#include "llvm/IR/DerivedTypes.h"
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2017-06-08 07:53:32 +08:00
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#include "llvm/IR/Dominators.h"
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2013-01-02 19:36:10 +08:00
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#include "llvm/IR/Function.h"
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2013-09-10 01:38:01 +08:00
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#include "llvm/IR/IRBuilder.h"
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2017-02-23 06:32:51 +08:00
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#include "llvm/IR/Instruction.h"
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2013-01-02 19:36:10 +08:00
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#include "llvm/IR/Instructions.h"
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[StackProtector] Ignore certain intrinsics when calculating sspstrong heuristic.
Summary:
The 'strong' StackProtector heuristic takes into consideration call instructions.
Certain intrinsics, such as lifetime.start, can cause the
StackProtector to protect functions that do not need to be protected.
Specifically, a volatile variable, (not optimized away), but belonging to a stack
allocation will encourage a llvm.lifetime.start to be inserted during
compilation. Because that intrinsic is a 'call' the strong StackProtector
will see that the alloca'd variable is being passed to a call instruction, and
insert a stack protector. In this case the intrinsic isn't really lowered to a
call. This can cause unnecessary stack checking, at the cost of additional
(wasted) CPU cycles.
In the future we should rely on TargetTransformInfo::isLoweredToCall, but as of
now that routine considers all intrinsics as not being lowerable. That needs
to be corrected, and such a change is on my list of things to get moving on.
As a side note, the updated stack-protector-dbginfo.ll test always seems to
pass. I never see the dbg.declare/dbg.value reaching the
StackProtector::HasAddressTaken, but I don't see any code excluding dbg
intrinsic calls either, so I think it's the safest thing to do.
Reviewers: void, timshen
Reviewed By: timshen
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D45331
llvm-svn: 329450
2018-04-07 04:14:13 +08:00
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#include "llvm/IR/IntrinsicInst.h"
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2013-01-02 19:36:10 +08:00
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#include "llvm/IR/Intrinsics.h"
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2014-12-01 12:27:03 +08:00
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#include "llvm/IR/MDBuilder.h"
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2013-01-02 19:36:10 +08:00
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#include "llvm/IR/Module.h"
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2017-02-23 06:32:51 +08:00
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#include "llvm/IR/Type.h"
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#include "llvm/IR/User.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/Casting.h"
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2008-11-04 10:10:20 +08:00
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#include "llvm/Support/CommandLine.h"
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2017-02-23 06:32:51 +08:00
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Target/TargetOptions.h"
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#include <utility>
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2008-11-04 10:10:20 +08:00
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using namespace llvm;
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2014-04-22 10:02:50 +08:00
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#define DEBUG_TYPE "stack-protector"
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2013-01-23 14:43:53 +08:00
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STATISTIC(NumFunProtected, "Number of functions protected");
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STATISTIC(NumAddrTaken, "Number of local variables that have their address"
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" taken.");
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2013-10-30 10:25:14 +08:00
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static cl::opt<bool> EnableSelectionDAGSP("enable-selectiondag-sp",
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cl::init(true), cl::Hidden);
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2013-08-20 16:36:53 +08:00
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2008-11-04 10:10:20 +08:00
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char StackProtector::ID = 0;
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2017-06-08 07:53:32 +08:00
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2017-05-26 05:26:32 +08:00
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INITIALIZE_PASS_BEGIN(StackProtector, DEBUG_TYPE,
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2017-05-19 01:21:13 +08:00
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"Insert stack protectors", false, true)
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INITIALIZE_PASS_DEPENDENCY(TargetPassConfig)
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2017-05-26 05:26:32 +08:00
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INITIALIZE_PASS_END(StackProtector, DEBUG_TYPE,
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2017-05-19 01:21:13 +08:00
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"Insert stack protectors", false, true)
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2008-11-04 10:10:20 +08:00
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2017-05-19 01:21:13 +08:00
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FunctionPass *llvm::createStackProtectorPass() { return new StackProtector(); }
|
2008-11-04 10:10:20 +08:00
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2017-06-06 06:59:21 +08:00
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void StackProtector::getAnalysisUsage(AnalysisUsage &AU) const {
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AU.addRequired<TargetPassConfig>();
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AU.addPreserved<DominatorTreeWrapperPass>();
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}
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2008-11-04 10:10:20 +08:00
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bool StackProtector::runOnFunction(Function &Fn) {
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F = &Fn;
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M = F->getParent();
|
2014-01-13 21:07:17 +08:00
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DominatorTreeWrapperPass *DTWP =
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getAnalysisIfAvailable<DominatorTreeWrapperPass>();
|
2014-04-14 08:51:57 +08:00
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DT = DTWP ? &DTWP->getDomTree() : nullptr;
|
2017-05-19 01:21:13 +08:00
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TM = &getAnalysis<TargetPassConfig>().getTM<TargetMachine>();
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Trip = TM->getTargetTriple();
|
2015-01-27 16:48:42 +08:00
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TLI = TM->getSubtargetImpl(Fn)->getTargetLowering();
|
2016-04-09 05:26:31 +08:00
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HasPrologue = false;
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HasIRCheck = false;
|
2008-11-04 10:10:20 +08:00
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2015-02-14 09:44:41 +08:00
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Attribute Attr = Fn.getFnAttribute("stack-protector-buffer-size");
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2014-01-21 18:24:35 +08:00
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if (Attr.isStringAttribute() &&
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Attr.getValueAsString().getAsInteger(10, SSPBufferSize))
|
[stack-protection] Add support for MSVC buffer security check
Summary:
This patch is adding support for the MSVC buffer security check implementation
The buffer security check is turned on with the '/GS' compiler switch.
* https://msdn.microsoft.com/en-us/library/8dbf701c.aspx
* To be added to clang here: http://reviews.llvm.org/D20347
Some overview of buffer security check feature and implementation:
* https://msdn.microsoft.com/en-us/library/aa290051(VS.71).aspx
* http://www.ksyash.com/2011/01/buffer-overflow-protection-3/
* http://blog.osom.info/2012/02/understanding-vs-c-compilers-buffer.html
For the following example:
```
int example(int offset, int index) {
char buffer[10];
memset(buffer, 0xCC, index);
return buffer[index];
}
```
The MSVC compiler is adding these instructions to perform stack integrity check:
```
push ebp
mov ebp,esp
sub esp,50h
[1] mov eax,dword ptr [__security_cookie (01068024h)]
[2] xor eax,ebp
[3] mov dword ptr [ebp-4],eax
push ebx
push esi
push edi
mov eax,dword ptr [index]
push eax
push 0CCh
lea ecx,[buffer]
push ecx
call _memset (010610B9h)
add esp,0Ch
mov eax,dword ptr [index]
movsx eax,byte ptr buffer[eax]
pop edi
pop esi
pop ebx
[4] mov ecx,dword ptr [ebp-4]
[5] xor ecx,ebp
[6] call @__security_check_cookie@4 (01061276h)
mov esp,ebp
pop ebp
ret
```
The instrumentation above is:
* [1] is loading the global security canary,
* [3] is storing the local computed ([2]) canary to the guard slot,
* [4] is loading the guard slot and ([5]) re-compute the global canary,
* [6] is validating the resulting canary with the '__security_check_cookie' and performs error handling.
Overview of the current stack-protection implementation:
* lib/CodeGen/StackProtector.cpp
* There is a default stack-protection implementation applied on intermediate representation.
* The target can overload 'getIRStackGuard' method if it has a standard location for the stack protector cookie.
* An intrinsic 'Intrinsic::stackprotector' is added to the prologue. It will be expanded by the instruction selection pass (DAG or Fast).
* Basic Blocks are added to every instrumented function to receive the code for handling stack guard validation and errors handling.
* Guard manipulation and comparison are added directly to the intermediate representation.
* lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
* lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
* There is an implementation that adds instrumentation during instruction selection (for better handling of sibbling calls).
* see long comment above 'class StackProtectorDescriptor' declaration.
* The target needs to override 'getSDagStackGuard' to activate SDAG stack protection generation. (note: getIRStackGuard MUST be nullptr).
* 'getSDagStackGuard' returns the appropriate stack guard (security cookie)
* The code is generated by 'SelectionDAGBuilder.cpp' and 'SelectionDAGISel.cpp'.
* include/llvm/Target/TargetLowering.h
* Contains function to retrieve the default Guard 'Value'; should be overriden by each target to select which implementation is used and provide Guard 'Value'.
* lib/Target/X86/X86ISelLowering.cpp
* Contains the x86 specialisation; Guard 'Value' used by the SelectionDAG algorithm.
Function-based Instrumentation:
* The MSVC doesn't inline the stack guard comparison in every function. Instead, a call to '__security_check_cookie' is added to the epilogue before every return instructions.
* To support function-based instrumentation, this patch is
* adding a function to get the function-based check (llvm 'Value', see include/llvm/Target/TargetLowering.h),
* If provided, the stack protection instrumentation won't be inlined and a call to that function will be added to the prologue.
* modifying (SelectionDAGISel.cpp) do avoid producing basic blocks used for inline instrumentation,
* generating the function-based instrumentation during the ISEL pass (SelectionDAGBuilder.cpp),
* if FastISEL (not SelectionDAG), using the fallback which rely on the same function-based implemented over intermediate representation (StackProtector.cpp).
Modifications
* adding support for MSVC (lib/Target/X86/X86ISelLowering.cpp)
* adding support function-based instrumentation (lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp, .h)
Results
* IR generated instrumentation:
```
clang-cl /GS test.cc /Od /c -mllvm -print-isel-input
```
```
*** Final LLVM Code input to ISel ***
; Function Attrs: nounwind sspstrong
define i32 @"\01?example@@YAHHH@Z"(i32 %offset, i32 %index) #0 {
entry:
%StackGuardSlot = alloca i8* <<<-- Allocated guard slot
%0 = call i8* @llvm.stackguard() <<<-- Loading Stack Guard value
call void @llvm.stackprotector(i8* %0, i8** %StackGuardSlot) <<<-- Prologue intrinsic call (store to Guard slot)
%index.addr = alloca i32, align 4
%offset.addr = alloca i32, align 4
%buffer = alloca [10 x i8], align 1
store i32 %index, i32* %index.addr, align 4
store i32 %offset, i32* %offset.addr, align 4
%arraydecay = getelementptr inbounds [10 x i8], [10 x i8]* %buffer, i32 0, i32 0
%1 = load i32, i32* %index.addr, align 4
call void @llvm.memset.p0i8.i32(i8* %arraydecay, i8 -52, i32 %1, i32 1, i1 false)
%2 = load i32, i32* %index.addr, align 4
%arrayidx = getelementptr inbounds [10 x i8], [10 x i8]* %buffer, i32 0, i32 %2
%3 = load i8, i8* %arrayidx, align 1
%conv = sext i8 %3 to i32
%4 = load volatile i8*, i8** %StackGuardSlot <<<-- Loading Guard slot
call void @__security_check_cookie(i8* %4) <<<-- Epilogue function-based check
ret i32 %conv
}
```
* SelectionDAG generated instrumentation:
```
clang-cl /GS test.cc /O1 /c /FA
```
```
"?example@@YAHHH@Z": # @"\01?example@@YAHHH@Z"
# BB#0: # %entry
pushl %esi
subl $16, %esp
movl ___security_cookie, %eax <<<-- Loading Stack Guard value
movl 28(%esp), %esi
movl %eax, 12(%esp) <<<-- Store to Guard slot
leal 2(%esp), %eax
pushl %esi
pushl $204
pushl %eax
calll _memset
addl $12, %esp
movsbl 2(%esp,%esi), %esi
movl 12(%esp), %ecx <<<-- Loading Guard slot
calll @__security_check_cookie@4 <<<-- Epilogue function-based check
movl %esi, %eax
addl $16, %esp
popl %esi
retl
```
Reviewers: kcc, pcc, eugenis, rnk
Subscribers: majnemer, llvm-commits, hans, thakis, rnk
Differential Revision: http://reviews.llvm.org/D20346
llvm-svn: 272053
2016-06-08 04:15:35 +08:00
|
|
|
return false; // Invalid integer string
|
2013-07-23 04:15:21 +08:00
|
|
|
|
2014-04-18 03:08:36 +08:00
|
|
|
if (!RequiresStackProtector())
|
|
|
|
return false;
|
|
|
|
|
[stack-protection] Add support for MSVC buffer security check
Summary:
This patch is adding support for the MSVC buffer security check implementation
The buffer security check is turned on with the '/GS' compiler switch.
* https://msdn.microsoft.com/en-us/library/8dbf701c.aspx
* To be added to clang here: http://reviews.llvm.org/D20347
Some overview of buffer security check feature and implementation:
* https://msdn.microsoft.com/en-us/library/aa290051(VS.71).aspx
* http://www.ksyash.com/2011/01/buffer-overflow-protection-3/
* http://blog.osom.info/2012/02/understanding-vs-c-compilers-buffer.html
For the following example:
```
int example(int offset, int index) {
char buffer[10];
memset(buffer, 0xCC, index);
return buffer[index];
}
```
The MSVC compiler is adding these instructions to perform stack integrity check:
```
push ebp
mov ebp,esp
sub esp,50h
[1] mov eax,dword ptr [__security_cookie (01068024h)]
[2] xor eax,ebp
[3] mov dword ptr [ebp-4],eax
push ebx
push esi
push edi
mov eax,dword ptr [index]
push eax
push 0CCh
lea ecx,[buffer]
push ecx
call _memset (010610B9h)
add esp,0Ch
mov eax,dword ptr [index]
movsx eax,byte ptr buffer[eax]
pop edi
pop esi
pop ebx
[4] mov ecx,dword ptr [ebp-4]
[5] xor ecx,ebp
[6] call @__security_check_cookie@4 (01061276h)
mov esp,ebp
pop ebp
ret
```
The instrumentation above is:
* [1] is loading the global security canary,
* [3] is storing the local computed ([2]) canary to the guard slot,
* [4] is loading the guard slot and ([5]) re-compute the global canary,
* [6] is validating the resulting canary with the '__security_check_cookie' and performs error handling.
Overview of the current stack-protection implementation:
* lib/CodeGen/StackProtector.cpp
* There is a default stack-protection implementation applied on intermediate representation.
* The target can overload 'getIRStackGuard' method if it has a standard location for the stack protector cookie.
* An intrinsic 'Intrinsic::stackprotector' is added to the prologue. It will be expanded by the instruction selection pass (DAG or Fast).
* Basic Blocks are added to every instrumented function to receive the code for handling stack guard validation and errors handling.
* Guard manipulation and comparison are added directly to the intermediate representation.
* lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
* lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
* There is an implementation that adds instrumentation during instruction selection (for better handling of sibbling calls).
* see long comment above 'class StackProtectorDescriptor' declaration.
* The target needs to override 'getSDagStackGuard' to activate SDAG stack protection generation. (note: getIRStackGuard MUST be nullptr).
* 'getSDagStackGuard' returns the appropriate stack guard (security cookie)
* The code is generated by 'SelectionDAGBuilder.cpp' and 'SelectionDAGISel.cpp'.
* include/llvm/Target/TargetLowering.h
* Contains function to retrieve the default Guard 'Value'; should be overriden by each target to select which implementation is used and provide Guard 'Value'.
* lib/Target/X86/X86ISelLowering.cpp
* Contains the x86 specialisation; Guard 'Value' used by the SelectionDAG algorithm.
Function-based Instrumentation:
* The MSVC doesn't inline the stack guard comparison in every function. Instead, a call to '__security_check_cookie' is added to the epilogue before every return instructions.
* To support function-based instrumentation, this patch is
* adding a function to get the function-based check (llvm 'Value', see include/llvm/Target/TargetLowering.h),
* If provided, the stack protection instrumentation won't be inlined and a call to that function will be added to the prologue.
* modifying (SelectionDAGISel.cpp) do avoid producing basic blocks used for inline instrumentation,
* generating the function-based instrumentation during the ISEL pass (SelectionDAGBuilder.cpp),
* if FastISEL (not SelectionDAG), using the fallback which rely on the same function-based implemented over intermediate representation (StackProtector.cpp).
Modifications
* adding support for MSVC (lib/Target/X86/X86ISelLowering.cpp)
* adding support function-based instrumentation (lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp, .h)
Results
* IR generated instrumentation:
```
clang-cl /GS test.cc /Od /c -mllvm -print-isel-input
```
```
*** Final LLVM Code input to ISel ***
; Function Attrs: nounwind sspstrong
define i32 @"\01?example@@YAHHH@Z"(i32 %offset, i32 %index) #0 {
entry:
%StackGuardSlot = alloca i8* <<<-- Allocated guard slot
%0 = call i8* @llvm.stackguard() <<<-- Loading Stack Guard value
call void @llvm.stackprotector(i8* %0, i8** %StackGuardSlot) <<<-- Prologue intrinsic call (store to Guard slot)
%index.addr = alloca i32, align 4
%offset.addr = alloca i32, align 4
%buffer = alloca [10 x i8], align 1
store i32 %index, i32* %index.addr, align 4
store i32 %offset, i32* %offset.addr, align 4
%arraydecay = getelementptr inbounds [10 x i8], [10 x i8]* %buffer, i32 0, i32 0
%1 = load i32, i32* %index.addr, align 4
call void @llvm.memset.p0i8.i32(i8* %arraydecay, i8 -52, i32 %1, i32 1, i1 false)
%2 = load i32, i32* %index.addr, align 4
%arrayidx = getelementptr inbounds [10 x i8], [10 x i8]* %buffer, i32 0, i32 %2
%3 = load i8, i8* %arrayidx, align 1
%conv = sext i8 %3 to i32
%4 = load volatile i8*, i8** %StackGuardSlot <<<-- Loading Guard slot
call void @__security_check_cookie(i8* %4) <<<-- Epilogue function-based check
ret i32 %conv
}
```
* SelectionDAG generated instrumentation:
```
clang-cl /GS test.cc /O1 /c /FA
```
```
"?example@@YAHHH@Z": # @"\01?example@@YAHHH@Z"
# BB#0: # %entry
pushl %esi
subl $16, %esp
movl ___security_cookie, %eax <<<-- Loading Stack Guard value
movl 28(%esp), %esi
movl %eax, 12(%esp) <<<-- Store to Guard slot
leal 2(%esp), %eax
pushl %esi
pushl $204
pushl %eax
calll _memset
addl $12, %esp
movsbl 2(%esp,%esi), %esi
movl 12(%esp), %ecx <<<-- Loading Guard slot
calll @__security_check_cookie@4 <<<-- Epilogue function-based check
movl %esi, %eax
addl $16, %esp
popl %esi
retl
```
Reviewers: kcc, pcc, eugenis, rnk
Subscribers: majnemer, llvm-commits, hans, thakis, rnk
Differential Revision: http://reviews.llvm.org/D20346
llvm-svn: 272053
2016-06-08 04:15:35 +08:00
|
|
|
// TODO(etienneb): Functions with funclets are not correctly supported now.
|
|
|
|
// Do nothing if this is funclet-based personality.
|
|
|
|
if (Fn.hasPersonalityFn()) {
|
|
|
|
EHPersonality Personality = classifyEHPersonality(Fn.getPersonalityFn());
|
|
|
|
if (isFuncletEHPersonality(Personality))
|
|
|
|
return false;
|
|
|
|
}
|
|
|
|
|
2013-01-23 14:43:53 +08:00
|
|
|
++NumFunProtected;
|
2008-11-05 08:00:21 +08:00
|
|
|
return InsertStackProtectors();
|
2008-11-04 10:10:20 +08:00
|
|
|
}
|
|
|
|
|
2013-10-30 05:16:16 +08:00
|
|
|
/// \param [out] IsLarge is set to true if a protectable array is found and
|
|
|
|
/// it is "large" ( >= ssp-buffer-size). In the case of a structure with
|
|
|
|
/// multiple arrays, this gets set if any of them is large.
|
|
|
|
bool StackProtector::ContainsProtectableArray(Type *Ty, bool &IsLarge,
|
2013-10-30 10:25:14 +08:00
|
|
|
bool Strong,
|
|
|
|
bool InStruct) const {
|
|
|
|
if (!Ty)
|
|
|
|
return false;
|
2012-08-18 04:59:56 +08:00
|
|
|
if (ArrayType *AT = dyn_cast<ArrayType>(Ty)) {
|
|
|
|
if (!AT->getElementType()->isIntegerTy(8)) {
|
|
|
|
// If we're on a non-Darwin platform or we're inside of a structure, don't
|
|
|
|
// add stack protectors unless the array is a character array.
|
2013-10-30 05:16:16 +08:00
|
|
|
// However, in strong mode any array, regardless of type and size,
|
|
|
|
// triggers a protector.
|
|
|
|
if (!Strong && (InStruct || !Trip.isOSDarwin()))
|
|
|
|
return false;
|
2012-08-18 04:59:56 +08:00
|
|
|
}
|
|
|
|
|
|
|
|
// If an array has more than SSPBufferSize bytes of allocated space, then we
|
|
|
|
// emit stack protectors.
|
2015-07-08 07:38:49 +08:00
|
|
|
if (SSPBufferSize <= M->getDataLayout().getTypeAllocSize(AT)) {
|
2013-10-30 05:16:16 +08:00
|
|
|
IsLarge = true;
|
|
|
|
return true;
|
2013-10-30 10:25:14 +08:00
|
|
|
}
|
2013-10-30 05:16:16 +08:00
|
|
|
|
|
|
|
if (Strong)
|
|
|
|
// Require a protector for all arrays in strong mode
|
2012-08-18 04:59:56 +08:00
|
|
|
return true;
|
|
|
|
}
|
|
|
|
|
|
|
|
const StructType *ST = dyn_cast<StructType>(Ty);
|
2013-10-30 10:25:14 +08:00
|
|
|
if (!ST)
|
|
|
|
return false;
|
2012-08-18 04:59:56 +08:00
|
|
|
|
2013-10-30 05:16:16 +08:00
|
|
|
bool NeedsProtector = false;
|
2012-08-18 04:59:56 +08:00
|
|
|
for (StructType::element_iterator I = ST->element_begin(),
|
2013-10-30 10:25:14 +08:00
|
|
|
E = ST->element_end();
|
|
|
|
I != E; ++I)
|
2013-10-30 05:16:16 +08:00
|
|
|
if (ContainsProtectableArray(*I, IsLarge, Strong, true)) {
|
|
|
|
// If the element is a protectable array and is large (>= SSPBufferSize)
|
|
|
|
// then we are done. If the protectable array is not large, then
|
|
|
|
// keep looking in case a subsequent element is a large array.
|
|
|
|
if (IsLarge)
|
|
|
|
return true;
|
|
|
|
NeedsProtector = true;
|
|
|
|
}
|
2012-08-18 04:59:56 +08:00
|
|
|
|
2013-10-30 05:16:16 +08:00
|
|
|
return NeedsProtector;
|
2012-08-18 04:59:56 +08:00
|
|
|
}
|
|
|
|
|
[StackProtector] Ignore certain intrinsics when calculating sspstrong heuristic.
Summary:
The 'strong' StackProtector heuristic takes into consideration call instructions.
Certain intrinsics, such as lifetime.start, can cause the
StackProtector to protect functions that do not need to be protected.
Specifically, a volatile variable, (not optimized away), but belonging to a stack
allocation will encourage a llvm.lifetime.start to be inserted during
compilation. Because that intrinsic is a 'call' the strong StackProtector
will see that the alloca'd variable is being passed to a call instruction, and
insert a stack protector. In this case the intrinsic isn't really lowered to a
call. This can cause unnecessary stack checking, at the cost of additional
(wasted) CPU cycles.
In the future we should rely on TargetTransformInfo::isLoweredToCall, but as of
now that routine considers all intrinsics as not being lowerable. That needs
to be corrected, and such a change is on my list of things to get moving on.
As a side note, the updated stack-protector-dbginfo.ll test always seems to
pass. I never see the dbg.declare/dbg.value reaching the
StackProtector::HasAddressTaken, but I don't see any code excluding dbg
intrinsic calls either, so I think it's the safest thing to do.
Reviewers: void, timshen
Reviewed By: timshen
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D45331
llvm-svn: 329450
2018-04-07 04:14:13 +08:00
|
|
|
static bool isLifetimeInst(const Instruction *I) {
|
|
|
|
if (const auto Intrinsic = dyn_cast<IntrinsicInst>(I)) {
|
|
|
|
const auto Id = Intrinsic->getIntrinsicID();
|
|
|
|
return Id == Intrinsic::lifetime_start || Id == Intrinsic::lifetime_end;
|
|
|
|
}
|
|
|
|
return false;
|
|
|
|
}
|
|
|
|
|
2013-01-23 14:43:53 +08:00
|
|
|
bool StackProtector::HasAddressTaken(const Instruction *AI) {
|
2014-03-09 11:16:01 +08:00
|
|
|
for (const User *U : AI->users()) {
|
2013-01-23 14:43:53 +08:00
|
|
|
if (const StoreInst *SI = dyn_cast<StoreInst>(U)) {
|
|
|
|
if (AI == SI->getValueOperand())
|
|
|
|
return true;
|
|
|
|
} else if (const PtrToIntInst *SI = dyn_cast<PtrToIntInst>(U)) {
|
|
|
|
if (AI == SI->getOperand(0))
|
|
|
|
return true;
|
[StackProtector] Ignore certain intrinsics when calculating sspstrong heuristic.
Summary:
The 'strong' StackProtector heuristic takes into consideration call instructions.
Certain intrinsics, such as lifetime.start, can cause the
StackProtector to protect functions that do not need to be protected.
Specifically, a volatile variable, (not optimized away), but belonging to a stack
allocation will encourage a llvm.lifetime.start to be inserted during
compilation. Because that intrinsic is a 'call' the strong StackProtector
will see that the alloca'd variable is being passed to a call instruction, and
insert a stack protector. In this case the intrinsic isn't really lowered to a
call. This can cause unnecessary stack checking, at the cost of additional
(wasted) CPU cycles.
In the future we should rely on TargetTransformInfo::isLoweredToCall, but as of
now that routine considers all intrinsics as not being lowerable. That needs
to be corrected, and such a change is on my list of things to get moving on.
As a side note, the updated stack-protector-dbginfo.ll test always seems to
pass. I never see the dbg.declare/dbg.value reaching the
StackProtector::HasAddressTaken, but I don't see any code excluding dbg
intrinsic calls either, so I think it's the safest thing to do.
Reviewers: void, timshen
Reviewed By: timshen
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D45331
llvm-svn: 329450
2018-04-07 04:14:13 +08:00
|
|
|
} else if (const CallInst *CI = dyn_cast<CallInst>(U)) {
|
|
|
|
// Ignore intrinsics that are not calls. TODO: Use isLoweredToCall().
|
|
|
|
if (!isa<DbgInfoIntrinsic>(CI) && !isLifetimeInst(CI))
|
|
|
|
return true;
|
2013-01-23 14:43:53 +08:00
|
|
|
} else if (isa<InvokeInst>(U)) {
|
|
|
|
return true;
|
|
|
|
} else if (const SelectInst *SI = dyn_cast<SelectInst>(U)) {
|
|
|
|
if (HasAddressTaken(SI))
|
|
|
|
return true;
|
|
|
|
} else if (const PHINode *PN = dyn_cast<PHINode>(U)) {
|
|
|
|
// Keep track of what PHI nodes we have already visited to ensure
|
|
|
|
// they are only visited once.
|
2014-11-19 15:49:26 +08:00
|
|
|
if (VisitedPHIs.insert(PN).second)
|
2013-01-23 14:43:53 +08:00
|
|
|
if (HasAddressTaken(PN))
|
|
|
|
return true;
|
|
|
|
} else if (const GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
|
|
|
|
if (HasAddressTaken(GEP))
|
|
|
|
return true;
|
|
|
|
} else if (const BitCastInst *BI = dyn_cast<BitCastInst>(U)) {
|
|
|
|
if (HasAddressTaken(BI))
|
|
|
|
return true;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
return false;
|
|
|
|
}
|
2008-11-18 13:32:11 +08:00
|
|
|
|
2018-05-01 23:54:18 +08:00
|
|
|
/// Check whether or not this function needs a stack protector based
|
2013-01-23 14:43:53 +08:00
|
|
|
/// upon the stack protector level.
|
|
|
|
///
|
|
|
|
/// We use two heuristics: a standard (ssp) and strong (sspstrong).
|
|
|
|
/// The standard heuristic which will add a guard variable to functions that
|
|
|
|
/// call alloca with a either a variable size or a size >= SSPBufferSize,
|
|
|
|
/// functions with character buffers larger than SSPBufferSize, and functions
|
|
|
|
/// with aggregates containing character buffers larger than SSPBufferSize. The
|
|
|
|
/// strong heuristic will add a guard variables to functions that call alloca
|
|
|
|
/// regardless of size, functions with any buffer regardless of type and size,
|
|
|
|
/// functions with aggregates that contain any buffer regardless of type and
|
|
|
|
/// size, and functions that contain stack-based variables that have had their
|
|
|
|
/// address taken.
|
|
|
|
bool StackProtector::RequiresStackProtector() {
|
|
|
|
bool Strong = false;
|
2013-10-30 05:16:16 +08:00
|
|
|
bool NeedsProtector = false;
|
2016-04-09 05:26:31 +08:00
|
|
|
for (const BasicBlock &BB : *F)
|
|
|
|
for (const Instruction &I : BB)
|
|
|
|
if (const CallInst *CI = dyn_cast<CallInst>(&I))
|
|
|
|
if (CI->getCalledFunction() ==
|
|
|
|
Intrinsic::getDeclaration(F->getParent(),
|
|
|
|
Intrinsic::stackprotector))
|
|
|
|
HasPrologue = true;
|
|
|
|
|
2016-04-12 06:27:48 +08:00
|
|
|
if (F->hasFnAttribute(Attribute::SafeStack))
|
|
|
|
return false;
|
|
|
|
|
2017-03-01 00:02:37 +08:00
|
|
|
// We are constructing the OptimizationRemarkEmitter on the fly rather than
|
|
|
|
// using the analysis pass to avoid building DominatorTree and LoopInfo which
|
|
|
|
// are not available this late in the IR pipeline.
|
|
|
|
OptimizationRemarkEmitter ORE(F);
|
|
|
|
|
2015-02-14 09:44:41 +08:00
|
|
|
if (F->hasFnAttribute(Attribute::StackProtectReq)) {
|
2017-10-12 01:12:59 +08:00
|
|
|
ORE.emit([&]() {
|
|
|
|
return OptimizationRemark(DEBUG_TYPE, "StackProtectorRequested", F)
|
2017-03-09 14:10:27 +08:00
|
|
|
<< "Stack protection applied to function "
|
|
|
|
<< ore::NV("Function", F)
|
2017-10-12 01:12:59 +08:00
|
|
|
<< " due to a function attribute or command-line switch";
|
|
|
|
});
|
2013-10-30 05:16:16 +08:00
|
|
|
NeedsProtector = true;
|
|
|
|
Strong = true; // Use the same heuristic as strong to determine SSPLayout
|
2015-02-14 09:44:41 +08:00
|
|
|
} else if (F->hasFnAttribute(Attribute::StackProtectStrong))
|
2013-01-23 14:43:53 +08:00
|
|
|
Strong = true;
|
2016-04-09 05:26:31 +08:00
|
|
|
else if (HasPrologue)
|
|
|
|
NeedsProtector = true;
|
2015-02-14 09:44:41 +08:00
|
|
|
else if (!F->hasFnAttribute(Attribute::StackProtect))
|
2008-11-18 13:32:11 +08:00
|
|
|
return false;
|
|
|
|
|
2014-12-21 05:37:51 +08:00
|
|
|
for (const BasicBlock &BB : *F) {
|
|
|
|
for (const Instruction &I : BB) {
|
|
|
|
if (const AllocaInst *AI = dyn_cast<AllocaInst>(&I)) {
|
2013-01-23 14:43:53 +08:00
|
|
|
if (AI->isArrayAllocation()) {
|
2017-10-12 01:12:59 +08:00
|
|
|
auto RemarkBuilder = [&]() {
|
|
|
|
return OptimizationRemark(DEBUG_TYPE, "StackProtectorAllocaOrArray",
|
|
|
|
&I)
|
|
|
|
<< "Stack protection applied to function "
|
|
|
|
<< ore::NV("Function", F)
|
|
|
|
<< " due to a call to alloca or use of a variable length "
|
|
|
|
"array";
|
|
|
|
};
|
2014-12-21 05:37:51 +08:00
|
|
|
if (const auto *CI = dyn_cast<ConstantInt>(AI->getArraySize())) {
|
2013-10-30 05:16:16 +08:00
|
|
|
if (CI->getLimitedValue(SSPBufferSize) >= SSPBufferSize) {
|
2013-01-23 14:43:53 +08:00
|
|
|
// A call to alloca with size >= SSPBufferSize requires
|
|
|
|
// stack protectors.
|
2018-07-13 08:08:38 +08:00
|
|
|
Layout.insert(std::make_pair(AI,
|
|
|
|
MachineFrameInfo::SSPLK_LargeArray));
|
2017-10-12 01:12:59 +08:00
|
|
|
ORE.emit(RemarkBuilder);
|
2013-10-30 05:16:16 +08:00
|
|
|
NeedsProtector = true;
|
|
|
|
} else if (Strong) {
|
|
|
|
// Require protectors for all alloca calls in strong mode.
|
2018-07-13 08:08:38 +08:00
|
|
|
Layout.insert(std::make_pair(AI,
|
|
|
|
MachineFrameInfo::SSPLK_SmallArray));
|
2017-10-12 01:12:59 +08:00
|
|
|
ORE.emit(RemarkBuilder);
|
2013-10-30 05:16:16 +08:00
|
|
|
NeedsProtector = true;
|
|
|
|
}
|
2013-07-23 04:15:21 +08:00
|
|
|
} else {
|
|
|
|
// A call to alloca with a variable size requires protectors.
|
2018-07-13 08:08:38 +08:00
|
|
|
Layout.insert(std::make_pair(AI,
|
|
|
|
MachineFrameInfo::SSPLK_LargeArray));
|
2017-10-12 01:12:59 +08:00
|
|
|
ORE.emit(RemarkBuilder);
|
2013-10-30 05:16:16 +08:00
|
|
|
NeedsProtector = true;
|
2013-07-23 04:15:21 +08:00
|
|
|
}
|
2013-10-30 05:16:16 +08:00
|
|
|
continue;
|
2013-01-23 14:43:53 +08:00
|
|
|
}
|
|
|
|
|
2013-10-30 05:16:16 +08:00
|
|
|
bool IsLarge = false;
|
|
|
|
if (ContainsProtectableArray(AI->getAllocatedType(), IsLarge, Strong)) {
|
2018-07-13 08:08:38 +08:00
|
|
|
Layout.insert(std::make_pair(AI, IsLarge
|
|
|
|
? MachineFrameInfo::SSPLK_LargeArray
|
|
|
|
: MachineFrameInfo::SSPLK_SmallArray));
|
2017-10-12 01:12:59 +08:00
|
|
|
ORE.emit([&]() {
|
|
|
|
return OptimizationRemark(DEBUG_TYPE, "StackProtectorBuffer", &I)
|
2017-03-09 14:10:27 +08:00
|
|
|
<< "Stack protection applied to function "
|
|
|
|
<< ore::NV("Function", F)
|
|
|
|
<< " due to a stack allocated buffer or struct containing a "
|
2017-10-12 01:12:59 +08:00
|
|
|
"buffer";
|
|
|
|
});
|
2013-10-30 05:16:16 +08:00
|
|
|
NeedsProtector = true;
|
|
|
|
continue;
|
|
|
|
}
|
2008-11-18 13:32:11 +08:00
|
|
|
|
2013-01-23 14:43:53 +08:00
|
|
|
if (Strong && HasAddressTaken(AI)) {
|
2013-08-20 16:46:16 +08:00
|
|
|
++NumAddrTaken;
|
2018-07-13 08:08:38 +08:00
|
|
|
Layout.insert(std::make_pair(AI, MachineFrameInfo::SSPLK_AddrOf));
|
2017-10-12 01:12:59 +08:00
|
|
|
ORE.emit([&]() {
|
|
|
|
return OptimizationRemark(DEBUG_TYPE, "StackProtectorAddressTaken",
|
|
|
|
&I)
|
|
|
|
<< "Stack protection applied to function "
|
|
|
|
<< ore::NV("Function", F)
|
|
|
|
<< " due to the address of a local variable being taken";
|
|
|
|
});
|
2013-10-30 05:16:16 +08:00
|
|
|
NeedsProtector = true;
|
2013-01-23 14:43:53 +08:00
|
|
|
}
|
2008-11-18 13:32:11 +08:00
|
|
|
}
|
2013-01-23 14:43:53 +08:00
|
|
|
}
|
2008-11-18 13:32:11 +08:00
|
|
|
}
|
|
|
|
|
2013-10-30 05:16:16 +08:00
|
|
|
return NeedsProtector;
|
2008-11-18 13:32:11 +08:00
|
|
|
}
|
|
|
|
|
2016-04-20 03:40:37 +08:00
|
|
|
/// Create a stack guard loading and populate whether SelectionDAG SSP is
|
|
|
|
/// supported.
|
|
|
|
static Value *getStackGuard(const TargetLoweringBase *TLI, Module *M,
|
|
|
|
IRBuilder<> &B,
|
|
|
|
bool *SupportsSelectionDAGSP = nullptr) {
|
|
|
|
if (Value *Guard = TLI->getIRStackGuard(B))
|
|
|
|
return B.CreateLoad(Guard, true, "StackGuard");
|
|
|
|
|
|
|
|
// Use SelectionDAG SSP handling, since there isn't an IR guard.
|
|
|
|
//
|
|
|
|
// This is more or less weird, since we optionally output whether we
|
|
|
|
// should perform a SelectionDAG SP here. The reason is that it's strictly
|
|
|
|
// defined as !TLI->getIRStackGuard(B), where getIRStackGuard is also
|
|
|
|
// mutating. There is no way to get this bit without mutating the IR, so
|
|
|
|
// getting this bit has to happen in this right time.
|
|
|
|
//
|
|
|
|
// We could have define a new function TLI::supportsSelectionDAGSP(), but that
|
|
|
|
// will put more burden on the backends' overriding work, especially when it
|
|
|
|
// actually conveys the same information getIRStackGuard() already gives.
|
|
|
|
if (SupportsSelectionDAGSP)
|
|
|
|
*SupportsSelectionDAGSP = true;
|
|
|
|
TLI->insertSSPDeclarations(*M);
|
|
|
|
return B.CreateCall(Intrinsic::getDeclaration(M, Intrinsic::stackguard));
|
|
|
|
}
|
|
|
|
|
|
|
|
/// Insert code into the entry block that stores the stack guard
|
2013-07-23 04:44:11 +08:00
|
|
|
/// variable onto the stack:
|
|
|
|
///
|
|
|
|
/// entry:
|
|
|
|
/// StackGuardSlot = alloca i8*
|
2016-04-20 03:40:37 +08:00
|
|
|
/// StackGuard = <stack guard>
|
|
|
|
/// call void @llvm.stackprotector(StackGuard, StackGuardSlot)
|
2013-07-23 04:44:11 +08:00
|
|
|
///
|
2013-08-20 16:36:53 +08:00
|
|
|
/// Returns true if the platform/triple supports the stackprotectorcreate pseudo
|
|
|
|
/// node.
|
|
|
|
static bool CreatePrologue(Function *F, Module *M, ReturnInst *RI,
|
2016-04-20 03:40:37 +08:00
|
|
|
const TargetLoweringBase *TLI, AllocaInst *&AI) {
|
2013-08-20 16:36:53 +08:00
|
|
|
bool SupportsSelectionDAGSP = false;
|
2016-04-06 06:41:50 +08:00
|
|
|
IRBuilder<> B(&F->getEntryBlock().front());
|
2016-04-09 05:26:31 +08:00
|
|
|
PointerType *PtrTy = Type::getInt8PtrTy(RI->getContext());
|
2014-04-14 08:51:57 +08:00
|
|
|
AI = B.CreateAlloca(PtrTy, nullptr, "StackGuardSlot");
|
2016-04-20 03:40:37 +08:00
|
|
|
|
[stack-protection] Add support for MSVC buffer security check
Summary:
This patch is adding support for the MSVC buffer security check implementation
The buffer security check is turned on with the '/GS' compiler switch.
* https://msdn.microsoft.com/en-us/library/8dbf701c.aspx
* To be added to clang here: http://reviews.llvm.org/D20347
Some overview of buffer security check feature and implementation:
* https://msdn.microsoft.com/en-us/library/aa290051(VS.71).aspx
* http://www.ksyash.com/2011/01/buffer-overflow-protection-3/
* http://blog.osom.info/2012/02/understanding-vs-c-compilers-buffer.html
For the following example:
```
int example(int offset, int index) {
char buffer[10];
memset(buffer, 0xCC, index);
return buffer[index];
}
```
The MSVC compiler is adding these instructions to perform stack integrity check:
```
push ebp
mov ebp,esp
sub esp,50h
[1] mov eax,dword ptr [__security_cookie (01068024h)]
[2] xor eax,ebp
[3] mov dword ptr [ebp-4],eax
push ebx
push esi
push edi
mov eax,dword ptr [index]
push eax
push 0CCh
lea ecx,[buffer]
push ecx
call _memset (010610B9h)
add esp,0Ch
mov eax,dword ptr [index]
movsx eax,byte ptr buffer[eax]
pop edi
pop esi
pop ebx
[4] mov ecx,dword ptr [ebp-4]
[5] xor ecx,ebp
[6] call @__security_check_cookie@4 (01061276h)
mov esp,ebp
pop ebp
ret
```
The instrumentation above is:
* [1] is loading the global security canary,
* [3] is storing the local computed ([2]) canary to the guard slot,
* [4] is loading the guard slot and ([5]) re-compute the global canary,
* [6] is validating the resulting canary with the '__security_check_cookie' and performs error handling.
Overview of the current stack-protection implementation:
* lib/CodeGen/StackProtector.cpp
* There is a default stack-protection implementation applied on intermediate representation.
* The target can overload 'getIRStackGuard' method if it has a standard location for the stack protector cookie.
* An intrinsic 'Intrinsic::stackprotector' is added to the prologue. It will be expanded by the instruction selection pass (DAG or Fast).
* Basic Blocks are added to every instrumented function to receive the code for handling stack guard validation and errors handling.
* Guard manipulation and comparison are added directly to the intermediate representation.
* lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
* lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
* There is an implementation that adds instrumentation during instruction selection (for better handling of sibbling calls).
* see long comment above 'class StackProtectorDescriptor' declaration.
* The target needs to override 'getSDagStackGuard' to activate SDAG stack protection generation. (note: getIRStackGuard MUST be nullptr).
* 'getSDagStackGuard' returns the appropriate stack guard (security cookie)
* The code is generated by 'SelectionDAGBuilder.cpp' and 'SelectionDAGISel.cpp'.
* include/llvm/Target/TargetLowering.h
* Contains function to retrieve the default Guard 'Value'; should be overriden by each target to select which implementation is used and provide Guard 'Value'.
* lib/Target/X86/X86ISelLowering.cpp
* Contains the x86 specialisation; Guard 'Value' used by the SelectionDAG algorithm.
Function-based Instrumentation:
* The MSVC doesn't inline the stack guard comparison in every function. Instead, a call to '__security_check_cookie' is added to the epilogue before every return instructions.
* To support function-based instrumentation, this patch is
* adding a function to get the function-based check (llvm 'Value', see include/llvm/Target/TargetLowering.h),
* If provided, the stack protection instrumentation won't be inlined and a call to that function will be added to the prologue.
* modifying (SelectionDAGISel.cpp) do avoid producing basic blocks used for inline instrumentation,
* generating the function-based instrumentation during the ISEL pass (SelectionDAGBuilder.cpp),
* if FastISEL (not SelectionDAG), using the fallback which rely on the same function-based implemented over intermediate representation (StackProtector.cpp).
Modifications
* adding support for MSVC (lib/Target/X86/X86ISelLowering.cpp)
* adding support function-based instrumentation (lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp, .h)
Results
* IR generated instrumentation:
```
clang-cl /GS test.cc /Od /c -mllvm -print-isel-input
```
```
*** Final LLVM Code input to ISel ***
; Function Attrs: nounwind sspstrong
define i32 @"\01?example@@YAHHH@Z"(i32 %offset, i32 %index) #0 {
entry:
%StackGuardSlot = alloca i8* <<<-- Allocated guard slot
%0 = call i8* @llvm.stackguard() <<<-- Loading Stack Guard value
call void @llvm.stackprotector(i8* %0, i8** %StackGuardSlot) <<<-- Prologue intrinsic call (store to Guard slot)
%index.addr = alloca i32, align 4
%offset.addr = alloca i32, align 4
%buffer = alloca [10 x i8], align 1
store i32 %index, i32* %index.addr, align 4
store i32 %offset, i32* %offset.addr, align 4
%arraydecay = getelementptr inbounds [10 x i8], [10 x i8]* %buffer, i32 0, i32 0
%1 = load i32, i32* %index.addr, align 4
call void @llvm.memset.p0i8.i32(i8* %arraydecay, i8 -52, i32 %1, i32 1, i1 false)
%2 = load i32, i32* %index.addr, align 4
%arrayidx = getelementptr inbounds [10 x i8], [10 x i8]* %buffer, i32 0, i32 %2
%3 = load i8, i8* %arrayidx, align 1
%conv = sext i8 %3 to i32
%4 = load volatile i8*, i8** %StackGuardSlot <<<-- Loading Guard slot
call void @__security_check_cookie(i8* %4) <<<-- Epilogue function-based check
ret i32 %conv
}
```
* SelectionDAG generated instrumentation:
```
clang-cl /GS test.cc /O1 /c /FA
```
```
"?example@@YAHHH@Z": # @"\01?example@@YAHHH@Z"
# BB#0: # %entry
pushl %esi
subl $16, %esp
movl ___security_cookie, %eax <<<-- Loading Stack Guard value
movl 28(%esp), %esi
movl %eax, 12(%esp) <<<-- Store to Guard slot
leal 2(%esp), %eax
pushl %esi
pushl $204
pushl %eax
calll _memset
addl $12, %esp
movsbl 2(%esp,%esi), %esi
movl 12(%esp), %ecx <<<-- Loading Guard slot
calll @__security_check_cookie@4 <<<-- Epilogue function-based check
movl %esi, %eax
addl $16, %esp
popl %esi
retl
```
Reviewers: kcc, pcc, eugenis, rnk
Subscribers: majnemer, llvm-commits, hans, thakis, rnk
Differential Revision: http://reviews.llvm.org/D20346
llvm-svn: 272053
2016-06-08 04:15:35 +08:00
|
|
|
Value *GuardSlot = getStackGuard(TLI, M, B, &SupportsSelectionDAGSP);
|
2015-05-19 06:13:54 +08:00
|
|
|
B.CreateCall(Intrinsic::getDeclaration(M, Intrinsic::stackprotector),
|
[stack-protection] Add support for MSVC buffer security check
Summary:
This patch is adding support for the MSVC buffer security check implementation
The buffer security check is turned on with the '/GS' compiler switch.
* https://msdn.microsoft.com/en-us/library/8dbf701c.aspx
* To be added to clang here: http://reviews.llvm.org/D20347
Some overview of buffer security check feature and implementation:
* https://msdn.microsoft.com/en-us/library/aa290051(VS.71).aspx
* http://www.ksyash.com/2011/01/buffer-overflow-protection-3/
* http://blog.osom.info/2012/02/understanding-vs-c-compilers-buffer.html
For the following example:
```
int example(int offset, int index) {
char buffer[10];
memset(buffer, 0xCC, index);
return buffer[index];
}
```
The MSVC compiler is adding these instructions to perform stack integrity check:
```
push ebp
mov ebp,esp
sub esp,50h
[1] mov eax,dword ptr [__security_cookie (01068024h)]
[2] xor eax,ebp
[3] mov dword ptr [ebp-4],eax
push ebx
push esi
push edi
mov eax,dword ptr [index]
push eax
push 0CCh
lea ecx,[buffer]
push ecx
call _memset (010610B9h)
add esp,0Ch
mov eax,dword ptr [index]
movsx eax,byte ptr buffer[eax]
pop edi
pop esi
pop ebx
[4] mov ecx,dword ptr [ebp-4]
[5] xor ecx,ebp
[6] call @__security_check_cookie@4 (01061276h)
mov esp,ebp
pop ebp
ret
```
The instrumentation above is:
* [1] is loading the global security canary,
* [3] is storing the local computed ([2]) canary to the guard slot,
* [4] is loading the guard slot and ([5]) re-compute the global canary,
* [6] is validating the resulting canary with the '__security_check_cookie' and performs error handling.
Overview of the current stack-protection implementation:
* lib/CodeGen/StackProtector.cpp
* There is a default stack-protection implementation applied on intermediate representation.
* The target can overload 'getIRStackGuard' method if it has a standard location for the stack protector cookie.
* An intrinsic 'Intrinsic::stackprotector' is added to the prologue. It will be expanded by the instruction selection pass (DAG or Fast).
* Basic Blocks are added to every instrumented function to receive the code for handling stack guard validation and errors handling.
* Guard manipulation and comparison are added directly to the intermediate representation.
* lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
* lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
* There is an implementation that adds instrumentation during instruction selection (for better handling of sibbling calls).
* see long comment above 'class StackProtectorDescriptor' declaration.
* The target needs to override 'getSDagStackGuard' to activate SDAG stack protection generation. (note: getIRStackGuard MUST be nullptr).
* 'getSDagStackGuard' returns the appropriate stack guard (security cookie)
* The code is generated by 'SelectionDAGBuilder.cpp' and 'SelectionDAGISel.cpp'.
* include/llvm/Target/TargetLowering.h
* Contains function to retrieve the default Guard 'Value'; should be overriden by each target to select which implementation is used and provide Guard 'Value'.
* lib/Target/X86/X86ISelLowering.cpp
* Contains the x86 specialisation; Guard 'Value' used by the SelectionDAG algorithm.
Function-based Instrumentation:
* The MSVC doesn't inline the stack guard comparison in every function. Instead, a call to '__security_check_cookie' is added to the epilogue before every return instructions.
* To support function-based instrumentation, this patch is
* adding a function to get the function-based check (llvm 'Value', see include/llvm/Target/TargetLowering.h),
* If provided, the stack protection instrumentation won't be inlined and a call to that function will be added to the prologue.
* modifying (SelectionDAGISel.cpp) do avoid producing basic blocks used for inline instrumentation,
* generating the function-based instrumentation during the ISEL pass (SelectionDAGBuilder.cpp),
* if FastISEL (not SelectionDAG), using the fallback which rely on the same function-based implemented over intermediate representation (StackProtector.cpp).
Modifications
* adding support for MSVC (lib/Target/X86/X86ISelLowering.cpp)
* adding support function-based instrumentation (lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp, .h)
Results
* IR generated instrumentation:
```
clang-cl /GS test.cc /Od /c -mllvm -print-isel-input
```
```
*** Final LLVM Code input to ISel ***
; Function Attrs: nounwind sspstrong
define i32 @"\01?example@@YAHHH@Z"(i32 %offset, i32 %index) #0 {
entry:
%StackGuardSlot = alloca i8* <<<-- Allocated guard slot
%0 = call i8* @llvm.stackguard() <<<-- Loading Stack Guard value
call void @llvm.stackprotector(i8* %0, i8** %StackGuardSlot) <<<-- Prologue intrinsic call (store to Guard slot)
%index.addr = alloca i32, align 4
%offset.addr = alloca i32, align 4
%buffer = alloca [10 x i8], align 1
store i32 %index, i32* %index.addr, align 4
store i32 %offset, i32* %offset.addr, align 4
%arraydecay = getelementptr inbounds [10 x i8], [10 x i8]* %buffer, i32 0, i32 0
%1 = load i32, i32* %index.addr, align 4
call void @llvm.memset.p0i8.i32(i8* %arraydecay, i8 -52, i32 %1, i32 1, i1 false)
%2 = load i32, i32* %index.addr, align 4
%arrayidx = getelementptr inbounds [10 x i8], [10 x i8]* %buffer, i32 0, i32 %2
%3 = load i8, i8* %arrayidx, align 1
%conv = sext i8 %3 to i32
%4 = load volatile i8*, i8** %StackGuardSlot <<<-- Loading Guard slot
call void @__security_check_cookie(i8* %4) <<<-- Epilogue function-based check
ret i32 %conv
}
```
* SelectionDAG generated instrumentation:
```
clang-cl /GS test.cc /O1 /c /FA
```
```
"?example@@YAHHH@Z": # @"\01?example@@YAHHH@Z"
# BB#0: # %entry
pushl %esi
subl $16, %esp
movl ___security_cookie, %eax <<<-- Loading Stack Guard value
movl 28(%esp), %esi
movl %eax, 12(%esp) <<<-- Store to Guard slot
leal 2(%esp), %eax
pushl %esi
pushl $204
pushl %eax
calll _memset
addl $12, %esp
movsbl 2(%esp,%esi), %esi
movl 12(%esp), %ecx <<<-- Loading Guard slot
calll @__security_check_cookie@4 <<<-- Epilogue function-based check
movl %esi, %eax
addl $16, %esp
popl %esi
retl
```
Reviewers: kcc, pcc, eugenis, rnk
Subscribers: majnemer, llvm-commits, hans, thakis, rnk
Differential Revision: http://reviews.llvm.org/D20346
llvm-svn: 272053
2016-06-08 04:15:35 +08:00
|
|
|
{GuardSlot, AI});
|
2013-08-20 16:36:53 +08:00
|
|
|
return SupportsSelectionDAGSP;
|
2013-07-23 04:44:11 +08:00
|
|
|
}
|
|
|
|
|
2008-11-05 08:00:21 +08:00
|
|
|
/// InsertStackProtectors - Insert code into the prologue and epilogue of the
|
|
|
|
/// function.
|
|
|
|
///
|
|
|
|
/// - The prologue code loads and stores the stack guard onto the stack.
|
|
|
|
/// - The epilogue checks the value stored in the prologue against the original
|
|
|
|
/// value. It calls __stack_chk_fail if they differ.
|
|
|
|
bool StackProtector::InsertStackProtectors() {
|
2017-12-06 04:22:20 +08:00
|
|
|
// If the target wants to XOR the frame pointer into the guard value, it's
|
|
|
|
// impossible to emit the check in IR, so the target *must* support stack
|
|
|
|
// protection in SDAG.
|
2013-08-20 16:56:26 +08:00
|
|
|
bool SupportsSelectionDAGSP =
|
2017-12-06 04:22:20 +08:00
|
|
|
TLI->useStackGuardXorFP() ||
|
|
|
|
(EnableSelectionDAGSP && !TM->Options.EnableFastISel);
|
2014-04-14 08:51:57 +08:00
|
|
|
AllocaInst *AI = nullptr; // Place on stack that stores the stack guard.
|
2008-11-07 09:23:58 +08:00
|
|
|
|
2013-10-30 10:25:14 +08:00
|
|
|
for (Function::iterator I = F->begin(), E = F->end(); I != E;) {
|
2015-10-10 06:56:24 +08:00
|
|
|
BasicBlock *BB = &*I++;
|
2008-11-18 13:32:11 +08:00
|
|
|
ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator());
|
2013-08-20 16:56:28 +08:00
|
|
|
if (!RI)
|
|
|
|
continue;
|
2008-11-18 13:32:11 +08:00
|
|
|
|
[stack-protection] Add support for MSVC buffer security check
Summary:
This patch is adding support for the MSVC buffer security check implementation
The buffer security check is turned on with the '/GS' compiler switch.
* https://msdn.microsoft.com/en-us/library/8dbf701c.aspx
* To be added to clang here: http://reviews.llvm.org/D20347
Some overview of buffer security check feature and implementation:
* https://msdn.microsoft.com/en-us/library/aa290051(VS.71).aspx
* http://www.ksyash.com/2011/01/buffer-overflow-protection-3/
* http://blog.osom.info/2012/02/understanding-vs-c-compilers-buffer.html
For the following example:
```
int example(int offset, int index) {
char buffer[10];
memset(buffer, 0xCC, index);
return buffer[index];
}
```
The MSVC compiler is adding these instructions to perform stack integrity check:
```
push ebp
mov ebp,esp
sub esp,50h
[1] mov eax,dword ptr [__security_cookie (01068024h)]
[2] xor eax,ebp
[3] mov dword ptr [ebp-4],eax
push ebx
push esi
push edi
mov eax,dword ptr [index]
push eax
push 0CCh
lea ecx,[buffer]
push ecx
call _memset (010610B9h)
add esp,0Ch
mov eax,dword ptr [index]
movsx eax,byte ptr buffer[eax]
pop edi
pop esi
pop ebx
[4] mov ecx,dword ptr [ebp-4]
[5] xor ecx,ebp
[6] call @__security_check_cookie@4 (01061276h)
mov esp,ebp
pop ebp
ret
```
The instrumentation above is:
* [1] is loading the global security canary,
* [3] is storing the local computed ([2]) canary to the guard slot,
* [4] is loading the guard slot and ([5]) re-compute the global canary,
* [6] is validating the resulting canary with the '__security_check_cookie' and performs error handling.
Overview of the current stack-protection implementation:
* lib/CodeGen/StackProtector.cpp
* There is a default stack-protection implementation applied on intermediate representation.
* The target can overload 'getIRStackGuard' method if it has a standard location for the stack protector cookie.
* An intrinsic 'Intrinsic::stackprotector' is added to the prologue. It will be expanded by the instruction selection pass (DAG or Fast).
* Basic Blocks are added to every instrumented function to receive the code for handling stack guard validation and errors handling.
* Guard manipulation and comparison are added directly to the intermediate representation.
* lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
* lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
* There is an implementation that adds instrumentation during instruction selection (for better handling of sibbling calls).
* see long comment above 'class StackProtectorDescriptor' declaration.
* The target needs to override 'getSDagStackGuard' to activate SDAG stack protection generation. (note: getIRStackGuard MUST be nullptr).
* 'getSDagStackGuard' returns the appropriate stack guard (security cookie)
* The code is generated by 'SelectionDAGBuilder.cpp' and 'SelectionDAGISel.cpp'.
* include/llvm/Target/TargetLowering.h
* Contains function to retrieve the default Guard 'Value'; should be overriden by each target to select which implementation is used and provide Guard 'Value'.
* lib/Target/X86/X86ISelLowering.cpp
* Contains the x86 specialisation; Guard 'Value' used by the SelectionDAG algorithm.
Function-based Instrumentation:
* The MSVC doesn't inline the stack guard comparison in every function. Instead, a call to '__security_check_cookie' is added to the epilogue before every return instructions.
* To support function-based instrumentation, this patch is
* adding a function to get the function-based check (llvm 'Value', see include/llvm/Target/TargetLowering.h),
* If provided, the stack protection instrumentation won't be inlined and a call to that function will be added to the prologue.
* modifying (SelectionDAGISel.cpp) do avoid producing basic blocks used for inline instrumentation,
* generating the function-based instrumentation during the ISEL pass (SelectionDAGBuilder.cpp),
* if FastISEL (not SelectionDAG), using the fallback which rely on the same function-based implemented over intermediate representation (StackProtector.cpp).
Modifications
* adding support for MSVC (lib/Target/X86/X86ISelLowering.cpp)
* adding support function-based instrumentation (lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp, .h)
Results
* IR generated instrumentation:
```
clang-cl /GS test.cc /Od /c -mllvm -print-isel-input
```
```
*** Final LLVM Code input to ISel ***
; Function Attrs: nounwind sspstrong
define i32 @"\01?example@@YAHHH@Z"(i32 %offset, i32 %index) #0 {
entry:
%StackGuardSlot = alloca i8* <<<-- Allocated guard slot
%0 = call i8* @llvm.stackguard() <<<-- Loading Stack Guard value
call void @llvm.stackprotector(i8* %0, i8** %StackGuardSlot) <<<-- Prologue intrinsic call (store to Guard slot)
%index.addr = alloca i32, align 4
%offset.addr = alloca i32, align 4
%buffer = alloca [10 x i8], align 1
store i32 %index, i32* %index.addr, align 4
store i32 %offset, i32* %offset.addr, align 4
%arraydecay = getelementptr inbounds [10 x i8], [10 x i8]* %buffer, i32 0, i32 0
%1 = load i32, i32* %index.addr, align 4
call void @llvm.memset.p0i8.i32(i8* %arraydecay, i8 -52, i32 %1, i32 1, i1 false)
%2 = load i32, i32* %index.addr, align 4
%arrayidx = getelementptr inbounds [10 x i8], [10 x i8]* %buffer, i32 0, i32 %2
%3 = load i8, i8* %arrayidx, align 1
%conv = sext i8 %3 to i32
%4 = load volatile i8*, i8** %StackGuardSlot <<<-- Loading Guard slot
call void @__security_check_cookie(i8* %4) <<<-- Epilogue function-based check
ret i32 %conv
}
```
* SelectionDAG generated instrumentation:
```
clang-cl /GS test.cc /O1 /c /FA
```
```
"?example@@YAHHH@Z": # @"\01?example@@YAHHH@Z"
# BB#0: # %entry
pushl %esi
subl $16, %esp
movl ___security_cookie, %eax <<<-- Loading Stack Guard value
movl 28(%esp), %esi
movl %eax, 12(%esp) <<<-- Store to Guard slot
leal 2(%esp), %eax
pushl %esi
pushl $204
pushl %eax
calll _memset
addl $12, %esp
movsbl 2(%esp,%esi), %esi
movl 12(%esp), %ecx <<<-- Loading Guard slot
calll @__security_check_cookie@4 <<<-- Epilogue function-based check
movl %esi, %eax
addl $16, %esp
popl %esi
retl
```
Reviewers: kcc, pcc, eugenis, rnk
Subscribers: majnemer, llvm-commits, hans, thakis, rnk
Differential Revision: http://reviews.llvm.org/D20346
llvm-svn: 272053
2016-06-08 04:15:35 +08:00
|
|
|
// Generate prologue instrumentation if not already generated.
|
2013-08-10 05:26:18 +08:00
|
|
|
if (!HasPrologue) {
|
|
|
|
HasPrologue = true;
|
2016-04-20 03:40:37 +08:00
|
|
|
SupportsSelectionDAGSP &= CreatePrologue(F, M, RI, TLI, AI);
|
2013-08-20 16:46:16 +08:00
|
|
|
}
|
2013-08-20 16:36:53 +08:00
|
|
|
|
[stack-protection] Add support for MSVC buffer security check
Summary:
This patch is adding support for the MSVC buffer security check implementation
The buffer security check is turned on with the '/GS' compiler switch.
* https://msdn.microsoft.com/en-us/library/8dbf701c.aspx
* To be added to clang here: http://reviews.llvm.org/D20347
Some overview of buffer security check feature and implementation:
* https://msdn.microsoft.com/en-us/library/aa290051(VS.71).aspx
* http://www.ksyash.com/2011/01/buffer-overflow-protection-3/
* http://blog.osom.info/2012/02/understanding-vs-c-compilers-buffer.html
For the following example:
```
int example(int offset, int index) {
char buffer[10];
memset(buffer, 0xCC, index);
return buffer[index];
}
```
The MSVC compiler is adding these instructions to perform stack integrity check:
```
push ebp
mov ebp,esp
sub esp,50h
[1] mov eax,dword ptr [__security_cookie (01068024h)]
[2] xor eax,ebp
[3] mov dword ptr [ebp-4],eax
push ebx
push esi
push edi
mov eax,dword ptr [index]
push eax
push 0CCh
lea ecx,[buffer]
push ecx
call _memset (010610B9h)
add esp,0Ch
mov eax,dword ptr [index]
movsx eax,byte ptr buffer[eax]
pop edi
pop esi
pop ebx
[4] mov ecx,dword ptr [ebp-4]
[5] xor ecx,ebp
[6] call @__security_check_cookie@4 (01061276h)
mov esp,ebp
pop ebp
ret
```
The instrumentation above is:
* [1] is loading the global security canary,
* [3] is storing the local computed ([2]) canary to the guard slot,
* [4] is loading the guard slot and ([5]) re-compute the global canary,
* [6] is validating the resulting canary with the '__security_check_cookie' and performs error handling.
Overview of the current stack-protection implementation:
* lib/CodeGen/StackProtector.cpp
* There is a default stack-protection implementation applied on intermediate representation.
* The target can overload 'getIRStackGuard' method if it has a standard location for the stack protector cookie.
* An intrinsic 'Intrinsic::stackprotector' is added to the prologue. It will be expanded by the instruction selection pass (DAG or Fast).
* Basic Blocks are added to every instrumented function to receive the code for handling stack guard validation and errors handling.
* Guard manipulation and comparison are added directly to the intermediate representation.
* lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
* lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
* There is an implementation that adds instrumentation during instruction selection (for better handling of sibbling calls).
* see long comment above 'class StackProtectorDescriptor' declaration.
* The target needs to override 'getSDagStackGuard' to activate SDAG stack protection generation. (note: getIRStackGuard MUST be nullptr).
* 'getSDagStackGuard' returns the appropriate stack guard (security cookie)
* The code is generated by 'SelectionDAGBuilder.cpp' and 'SelectionDAGISel.cpp'.
* include/llvm/Target/TargetLowering.h
* Contains function to retrieve the default Guard 'Value'; should be overriden by each target to select which implementation is used and provide Guard 'Value'.
* lib/Target/X86/X86ISelLowering.cpp
* Contains the x86 specialisation; Guard 'Value' used by the SelectionDAG algorithm.
Function-based Instrumentation:
* The MSVC doesn't inline the stack guard comparison in every function. Instead, a call to '__security_check_cookie' is added to the epilogue before every return instructions.
* To support function-based instrumentation, this patch is
* adding a function to get the function-based check (llvm 'Value', see include/llvm/Target/TargetLowering.h),
* If provided, the stack protection instrumentation won't be inlined and a call to that function will be added to the prologue.
* modifying (SelectionDAGISel.cpp) do avoid producing basic blocks used for inline instrumentation,
* generating the function-based instrumentation during the ISEL pass (SelectionDAGBuilder.cpp),
* if FastISEL (not SelectionDAG), using the fallback which rely on the same function-based implemented over intermediate representation (StackProtector.cpp).
Modifications
* adding support for MSVC (lib/Target/X86/X86ISelLowering.cpp)
* adding support function-based instrumentation (lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp, .h)
Results
* IR generated instrumentation:
```
clang-cl /GS test.cc /Od /c -mllvm -print-isel-input
```
```
*** Final LLVM Code input to ISel ***
; Function Attrs: nounwind sspstrong
define i32 @"\01?example@@YAHHH@Z"(i32 %offset, i32 %index) #0 {
entry:
%StackGuardSlot = alloca i8* <<<-- Allocated guard slot
%0 = call i8* @llvm.stackguard() <<<-- Loading Stack Guard value
call void @llvm.stackprotector(i8* %0, i8** %StackGuardSlot) <<<-- Prologue intrinsic call (store to Guard slot)
%index.addr = alloca i32, align 4
%offset.addr = alloca i32, align 4
%buffer = alloca [10 x i8], align 1
store i32 %index, i32* %index.addr, align 4
store i32 %offset, i32* %offset.addr, align 4
%arraydecay = getelementptr inbounds [10 x i8], [10 x i8]* %buffer, i32 0, i32 0
%1 = load i32, i32* %index.addr, align 4
call void @llvm.memset.p0i8.i32(i8* %arraydecay, i8 -52, i32 %1, i32 1, i1 false)
%2 = load i32, i32* %index.addr, align 4
%arrayidx = getelementptr inbounds [10 x i8], [10 x i8]* %buffer, i32 0, i32 %2
%3 = load i8, i8* %arrayidx, align 1
%conv = sext i8 %3 to i32
%4 = load volatile i8*, i8** %StackGuardSlot <<<-- Loading Guard slot
call void @__security_check_cookie(i8* %4) <<<-- Epilogue function-based check
ret i32 %conv
}
```
* SelectionDAG generated instrumentation:
```
clang-cl /GS test.cc /O1 /c /FA
```
```
"?example@@YAHHH@Z": # @"\01?example@@YAHHH@Z"
# BB#0: # %entry
pushl %esi
subl $16, %esp
movl ___security_cookie, %eax <<<-- Loading Stack Guard value
movl 28(%esp), %esi
movl %eax, 12(%esp) <<<-- Store to Guard slot
leal 2(%esp), %eax
pushl %esi
pushl $204
pushl %eax
calll _memset
addl $12, %esp
movsbl 2(%esp,%esi), %esi
movl 12(%esp), %ecx <<<-- Loading Guard slot
calll @__security_check_cookie@4 <<<-- Epilogue function-based check
movl %esi, %eax
addl $16, %esp
popl %esi
retl
```
Reviewers: kcc, pcc, eugenis, rnk
Subscribers: majnemer, llvm-commits, hans, thakis, rnk
Differential Revision: http://reviews.llvm.org/D20346
llvm-svn: 272053
2016-06-08 04:15:35 +08:00
|
|
|
// SelectionDAG based code generation. Nothing else needs to be done here.
|
|
|
|
// The epilogue instrumentation is postponed to SelectionDAG.
|
|
|
|
if (SupportsSelectionDAGSP)
|
|
|
|
break;
|
|
|
|
|
|
|
|
// Set HasIRCheck to true, so that SelectionDAG will not generate its own
|
|
|
|
// version. SelectionDAG called 'shouldEmitSDCheck' to check whether
|
|
|
|
// instrumentation has already been generated.
|
|
|
|
HasIRCheck = true;
|
|
|
|
|
|
|
|
// Generate epilogue instrumentation. The epilogue intrumentation can be
|
|
|
|
// function-based or inlined depending on which mechanism the target is
|
|
|
|
// providing.
|
|
|
|
if (Value* GuardCheck = TLI->getSSPStackGuardCheck(*M)) {
|
|
|
|
// Generate the function-based epilogue instrumentation.
|
|
|
|
// The target provides a guard check function, generate a call to it.
|
|
|
|
IRBuilder<> B(RI);
|
|
|
|
LoadInst *Guard = B.CreateLoad(AI, true, "Guard");
|
|
|
|
CallInst *Call = B.CreateCall(GuardCheck, {Guard});
|
|
|
|
llvm::Function *Function = cast<llvm::Function>(GuardCheck);
|
|
|
|
Call->setAttributes(Function->getAttributes());
|
|
|
|
Call->setCallingConv(Function->getCallingConv());
|
|
|
|
} else {
|
|
|
|
// Generate the epilogue with inline instrumentation.
|
2013-08-20 16:46:13 +08:00
|
|
|
// If we do not support SelectionDAG based tail calls, generate IR level
|
|
|
|
// tail calls.
|
|
|
|
//
|
2013-08-20 16:36:53 +08:00
|
|
|
// For each block with a return instruction, convert this:
|
|
|
|
//
|
|
|
|
// return:
|
|
|
|
// ...
|
|
|
|
// ret ...
|
|
|
|
//
|
|
|
|
// into this:
|
|
|
|
//
|
|
|
|
// return:
|
|
|
|
// ...
|
2016-04-20 03:40:37 +08:00
|
|
|
// %1 = <stack guard>
|
2013-08-20 16:36:53 +08:00
|
|
|
// %2 = load StackGuardSlot
|
|
|
|
// %3 = cmp i1 %1, %2
|
|
|
|
// br i1 %3, label %SP_return, label %CallStackCheckFailBlk
|
|
|
|
//
|
|
|
|
// SP_return:
|
|
|
|
// ret ...
|
|
|
|
//
|
|
|
|
// CallStackCheckFailBlk:
|
|
|
|
// call void @__stack_chk_fail()
|
|
|
|
// unreachable
|
|
|
|
|
|
|
|
// Create the FailBB. We duplicate the BB every time since the MI tail
|
|
|
|
// merge pass will merge together all of the various BB into one including
|
2013-08-20 16:46:16 +08:00
|
|
|
// fail BB generated by the stack protector pseudo instruction.
|
2013-08-20 16:36:53 +08:00
|
|
|
BasicBlock *FailBB = CreateFailBB();
|
2013-08-20 16:46:16 +08:00
|
|
|
|
2013-08-20 16:36:53 +08:00
|
|
|
// Split the basic block before the return instruction.
|
2015-10-10 06:56:24 +08:00
|
|
|
BasicBlock *NewBB = BB->splitBasicBlock(RI->getIterator(), "SP_return");
|
2013-08-20 16:46:16 +08:00
|
|
|
|
2013-08-20 16:36:53 +08:00
|
|
|
// Update the dominator tree if we need to.
|
|
|
|
if (DT && DT->isReachableFromEntry(BB)) {
|
|
|
|
DT->addNewBlock(NewBB, BB);
|
|
|
|
DT->addNewBlock(FailBB, BB);
|
|
|
|
}
|
2013-08-20 16:46:16 +08:00
|
|
|
|
2013-08-20 16:36:53 +08:00
|
|
|
// Remove default branch instruction to the new BB.
|
|
|
|
BB->getTerminator()->eraseFromParent();
|
2013-08-20 16:46:16 +08:00
|
|
|
|
2013-08-20 16:36:53 +08:00
|
|
|
// Move the newly created basic block to the point right after the old
|
|
|
|
// basic block so that it's in the "fall through" position.
|
|
|
|
NewBB->moveAfter(BB);
|
2013-08-20 16:46:16 +08:00
|
|
|
|
2013-08-20 16:36:53 +08:00
|
|
|
// Generate the stack protector instructions in the old basic block.
|
2013-09-10 01:38:01 +08:00
|
|
|
IRBuilder<> B(BB);
|
2016-04-20 03:40:37 +08:00
|
|
|
Value *Guard = getStackGuard(TLI, M, B);
|
|
|
|
LoadInst *LI2 = B.CreateLoad(AI, true);
|
|
|
|
Value *Cmp = B.CreateICmpEQ(Guard, LI2);
|
2015-12-23 02:56:14 +08:00
|
|
|
auto SuccessProb =
|
|
|
|
BranchProbabilityInfo::getBranchProbStackProtector(true);
|
|
|
|
auto FailureProb =
|
|
|
|
BranchProbabilityInfo::getBranchProbStackProtector(false);
|
2014-12-01 12:27:03 +08:00
|
|
|
MDNode *Weights = MDBuilder(F->getContext())
|
2015-12-23 02:56:14 +08:00
|
|
|
.createBranchWeights(SuccessProb.getNumerator(),
|
|
|
|
FailureProb.getNumerator());
|
2014-12-01 12:27:03 +08:00
|
|
|
B.CreateCondBr(Cmp, NewBB, FailBB, Weights);
|
2011-01-09 01:01:52 +08:00
|
|
|
}
|
2008-11-04 10:10:20 +08:00
|
|
|
}
|
2008-11-05 08:00:21 +08:00
|
|
|
|
2014-12-22 05:52:38 +08:00
|
|
|
// Return if we didn't modify any basic blocks. i.e., there are no return
|
2008-11-07 07:55:49 +08:00
|
|
|
// statements in the function.
|
2015-10-25 07:11:13 +08:00
|
|
|
return HasPrologue;
|
2008-11-04 10:10:20 +08:00
|
|
|
}
|
|
|
|
|
|
|
|
/// CreateFailBB - Create a basic block to jump to when the stack protector
|
|
|
|
/// check fails.
|
2008-11-05 08:00:21 +08:00
|
|
|
BasicBlock *StackProtector::CreateFailBB() {
|
2013-06-08 00:35:57 +08:00
|
|
|
LLVMContext &Context = F->getContext();
|
|
|
|
BasicBlock *FailBB = BasicBlock::Create(Context, "CallStackCheckFailBlk", F);
|
2013-09-10 01:38:01 +08:00
|
|
|
IRBuilder<> B(FailBB);
|
2016-07-01 02:49:04 +08:00
|
|
|
B.SetCurrentDebugLocation(DebugLoc::get(0, 0, F->getSubprogram()));
|
2014-11-30 03:18:21 +08:00
|
|
|
if (Trip.isOSOpenBSD()) {
|
2017-04-07 04:23:57 +08:00
|
|
|
Constant *StackChkFail =
|
|
|
|
M->getOrInsertFunction("__stack_smash_handler",
|
|
|
|
Type::getVoidTy(Context),
|
2017-04-11 23:01:18 +08:00
|
|
|
Type::getInt8PtrTy(Context));
|
2013-06-08 00:35:57 +08:00
|
|
|
|
2013-09-10 01:38:01 +08:00
|
|
|
B.CreateCall(StackChkFail, B.CreateGlobalStringPtr(F->getName(), "SSH"));
|
2013-06-08 00:35:57 +08:00
|
|
|
} else {
|
2014-12-22 05:52:38 +08:00
|
|
|
Constant *StackChkFail =
|
2017-04-11 23:01:18 +08:00
|
|
|
M->getOrInsertFunction("__stack_chk_fail", Type::getVoidTy(Context));
|
|
|
|
|
2015-05-19 06:13:54 +08:00
|
|
|
B.CreateCall(StackChkFail, {});
|
2013-06-08 00:35:57 +08:00
|
|
|
}
|
2013-09-10 01:38:01 +08:00
|
|
|
B.CreateUnreachable();
|
2008-11-05 08:00:21 +08:00
|
|
|
return FailBB;
|
2008-11-04 10:10:20 +08:00
|
|
|
}
|
2016-04-09 05:26:31 +08:00
|
|
|
|
|
|
|
bool StackProtector::shouldEmitSDCheck(const BasicBlock &BB) const {
|
|
|
|
return HasPrologue && !HasIRCheck && dyn_cast<ReturnInst>(BB.getTerminator());
|
|
|
|
}
|
2018-07-13 08:08:38 +08:00
|
|
|
|
|
|
|
void StackProtector::copyToMachineFrameInfo(MachineFrameInfo &MFI) const {
|
|
|
|
if (Layout.empty())
|
|
|
|
return;
|
|
|
|
|
|
|
|
for (int I = 0, E = MFI.getObjectIndexEnd(); I != E; ++I) {
|
|
|
|
if (MFI.isDeadObjectIndex(I))
|
|
|
|
continue;
|
|
|
|
|
|
|
|
const AllocaInst *AI = MFI.getObjectAllocation(I);
|
|
|
|
if (!AI)
|
|
|
|
continue;
|
|
|
|
|
|
|
|
SSPLayoutMap::const_iterator LI = Layout.find(AI);
|
|
|
|
if (LI == Layout.end())
|
|
|
|
continue;
|
|
|
|
|
|
|
|
MFI.setObjectSSPLayout(I, LI->second);
|
|
|
|
}
|
|
|
|
}
|