[AArch64][v8.5A] Branch Target Identification code-generation pass
The Branch Target Identification extension, introduced to AArch64 in
Armv8.5-A, adds the BTI instruction, which is used to mark valid targets
of indirect branches. When enabled, the processor will trap if an
instruction in a protected page tries to perform an indirect branch to
any instruction other than a BTI. The BTI instruction uses encodings
which were NOPs in earlier versions of the architecture, so BTI-enabled
code will still run on earlier hardware, just without the extra
protection.
There are 3 variants of the BTI instruction, which are valid targets for
different kinds or branches:
- BTI C can be targeted by call instructions, and is inteneded to be
used at function entry points. These are the BLR instruction, as well
as BR with x16 or x17. These BR instructions are allowed for use in
PLT entries, and we can also use them to allow indirect tail-calls.
- BTI J can be targeted by BR only, and is intended to be used by jump
tables.
- BTI JC acts ab both a BTI C and a BTI J instruction, and can be
targeted by any BLR or BR instruction.
Note that RET instructions are not restricted by branch target
identification, the reason for this is that return addresses can be
protected more effectively using return address signing. Direct branches
and calls are also unaffected, as it is assumed that an attacker cannot
modify executable pages (if they could, they wouldn't need to do a
ROP/JOP attack).
This patch adds a MachineFunctionPass which:
- Adds a BTI C at the start of every function which could be indirectly
called (either because it is address-taken, or externally visible so
could be address-taken in another translation unit).
- Adds a BTI J at the start of every basic block which could be
indirectly branched to. This could be either done by a jump table, or
by taking the address of the block (e.g. the using GCC label values
extension).
We only need to use BTI JC when a function is indirectly-callable, and
takes the address of the entry block. I've not been able to trigger this
from C or IR, but I've included a MIR test just in case.
Using BTI C at function entries relies on the fact that no other code in
BTI-protected pages uses indirect tail-calls, unless they use x16 or x17
to hold the address. I'll add that code-generation restriction as a
separate patch.
Differential revision: https://reviews.llvm.org/D52867
llvm-svn: 343967
2018-10-08 22:04:24 +08:00
|
|
|
# RUN: llc -run-pass=aarch64-branch-targets %s -o - | FileCheck %s
|
|
|
|
|
--- |
|
|
|
|
|
target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
|
|
|
|
|
target triple = "aarch64-arm-none-eabi"
|
|
|
|
|
|
|
|
|
|
define hidden i32 @simple_external() "branch-target-enforcement" {
|
|
|
|
|
entry:
|
|
|
|
|
ret i32 0
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
define internal i32 @simple_internal() "branch-target-enforcement" {
|
|
|
|
|
entry:
|
|
|
|
|
ret i32 0
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
define hidden i32 @ptr_auth() "branch-target-enforcement" {
|
|
|
|
|
entry:
|
|
|
|
|
tail call void asm sideeffect "", "~{lr}"()
|
|
|
|
|
ret i32 0
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
define hidden i32 @ptr_auth_b() "branch-target-enforcement" {
|
|
|
|
|
entry:
|
|
|
|
|
tail call void asm sideeffect "", "~{lr}"()
|
|
|
|
|
ret i32 0
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
define hidden i32 @jump_table(i32 %a) "branch-target-enforcement" {
|
|
|
|
|
entry:
|
|
|
|
|
switch i32 %a, label %sw.epilog [
|
|
|
|
|
i32 1, label %sw.bb
|
|
|
|
|
i32 2, label %sw.bb1
|
|
|
|
|
i32 3, label %sw.bb2
|
|
|
|
|
i32 4, label %sw.bb3
|
|
|
|
|
i32 5, label %sw.bb4
|
|
|
|
|
]
|
|
|
|
|
|
|
|
|
|
sw.bb: ; preds = %entry
|
|
|
|
|
tail call void asm sideeffect "", ""()
|
|
|
|
|
br label %sw.epilog
|
|
|
|
|
|
|
|
|
|
sw.bb1: ; preds = %entry
|
|
|
|
|
tail call void asm sideeffect "", ""()
|
|
|
|
|
br label %sw.epilog
|
|
|
|
|
|
|
|
|
|
sw.bb2: ; preds = %entry
|
|
|
|
|
tail call void asm sideeffect "", ""()
|
|
|
|
|
br label %sw.epilog
|
|
|
|
|
|
|
|
|
|
sw.bb3: ; preds = %entry
|
|
|
|
|
tail call void asm sideeffect "", ""()
|
|
|
|
|
br label %sw.epilog
|
|
|
|
|
|
|
|
|
|
sw.bb4: ; preds = %entry
|
|
|
|
|
tail call void asm sideeffect "", ""()
|
|
|
|
|
br label %sw.epilog
|
|
|
|
|
|
|
|
|
|
sw.epilog: ; preds = %entry, %sw.bb4, %sw.bb3, %sw.bb2, %sw.bb1, %sw.bb
|
|
|
|
|
ret i32 0
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
@label_address.addr = internal unnamed_addr global i8* blockaddress(@label_address, %return), align 8
|
|
|
|
|
|
|
|
|
|
define hidden i32 @label_address() "branch-target-enforcement" {
|
|
|
|
|
entry:
|
|
|
|
|
%0 = load i8*, i8** @label_address.addr, align 8
|
|
|
|
|
indirectbr i8* %0, [label %return, label %lab2]
|
|
|
|
|
|
|
|
|
|
lab2: ; preds = %entry
|
|
|
|
|
br label %.split
|
|
|
|
|
|
|
|
|
|
return: ; preds = %entry
|
|
|
|
|
br label %.split
|
|
|
|
|
|
|
|
|
|
.split: ; preds = %lab2, %return
|
|
|
|
|
%merge = phi i8* [ blockaddress(@label_address, %lab2), %return ], [ blockaddress(@label_address, %return), %lab2 ]
|
|
|
|
|
%merge2 = phi i32 [ 1, %return ], [ 2, %lab2 ]
|
|
|
|
|
store i8* %merge, i8** @label_address.addr, align 8
|
|
|
|
|
ret i32 %merge2
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
define hidden i32 @label_address_entry() "branch-target-enforcement" {
|
|
|
|
|
entry:
|
|
|
|
|
%0 = load i8*, i8** @label_address.addr, align 8
|
|
|
|
|
indirectbr i8* %0, [label %return, label %lab2]
|
|
|
|
|
|
|
|
|
|
lab2: ; preds = %entry
|
|
|
|
|
br label %.split
|
|
|
|
|
|
|
|
|
|
return: ; preds = %entry
|
|
|
|
|
br label %.split
|
|
|
|
|
|
|
|
|
|
.split: ; preds = %lab2, %return
|
|
|
|
|
%merge = phi i8* [ blockaddress(@label_address, %lab2), %return ], [ blockaddress(@label_address, %return), %lab2 ]
|
|
|
|
|
%merge2 = phi i32 [ 1, %return ], [ 2, %lab2 ]
|
|
|
|
|
store i8* %merge, i8** @label_address.addr, align 8
|
|
|
|
|
ret i32 %merge2
|
|
|
|
|
}
|
|
|
|
|
|
2020-02-13 18:42:39 +08:00
|
|
|
define hidden i32 @debug_ptr_auth() "branch-target-enforcement" {
|
|
|
|
|
entry:
|
|
|
|
|
tail call void asm sideeffect "", "~{lr}"()
|
|
|
|
|
ret i32 0
|
|
|
|
|
}
|
|
|
|
|
|
[AArch64][v8.5A] Branch Target Identification code-generation pass
The Branch Target Identification extension, introduced to AArch64 in
Armv8.5-A, adds the BTI instruction, which is used to mark valid targets
of indirect branches. When enabled, the processor will trap if an
instruction in a protected page tries to perform an indirect branch to
any instruction other than a BTI. The BTI instruction uses encodings
which were NOPs in earlier versions of the architecture, so BTI-enabled
code will still run on earlier hardware, just without the extra
protection.
There are 3 variants of the BTI instruction, which are valid targets for
different kinds or branches:
- BTI C can be targeted by call instructions, and is inteneded to be
used at function entry points. These are the BLR instruction, as well
as BR with x16 or x17. These BR instructions are allowed for use in
PLT entries, and we can also use them to allow indirect tail-calls.
- BTI J can be targeted by BR only, and is intended to be used by jump
tables.
- BTI JC acts ab both a BTI C and a BTI J instruction, and can be
targeted by any BLR or BR instruction.
Note that RET instructions are not restricted by branch target
identification, the reason for this is that return addresses can be
protected more effectively using return address signing. Direct branches
and calls are also unaffected, as it is assumed that an attacker cannot
modify executable pages (if they could, they wouldn't need to do a
ROP/JOP attack).
This patch adds a MachineFunctionPass which:
- Adds a BTI C at the start of every function which could be indirectly
called (either because it is address-taken, or externally visible so
could be address-taken in another translation unit).
- Adds a BTI J at the start of every basic block which could be
indirectly branched to. This could be either done by a jump table, or
by taking the address of the block (e.g. the using GCC label values
extension).
We only need to use BTI JC when a function is indirectly-callable, and
takes the address of the entry block. I've not been able to trigger this
from C or IR, but I've included a MIR test just in case.
Using BTI C at function entries relies on the fact that no other code in
BTI-protected pages uses indirect tail-calls, unless they use x16 or x17
to hold the address. I'll add that code-generation restriction as a
separate patch.
Differential revision: https://reviews.llvm.org/D52867
llvm-svn: 343967
2018-10-08 22:04:24 +08:00
|
|
|
...
|
|
|
|
|
---
|
|
|
|
|
# External function, could be addres-taken elsewhere so needs BTI JC.
|
|
|
|
|
name: simple_external
|
|
|
|
|
body: |
|
|
|
|
|
bb.0.entry:
|
|
|
|
|
; CHECK-LABEL: name: simple_external
|
|
|
|
|
; CHECK: HINT 34
|
|
|
|
|
; CHECK: RET
|
|
|
|
|
$w0 = ORRWrs $wzr, $wzr, 0
|
|
|
|
|
RET undef $lr, implicit killed $w0
|
|
|
|
|
|
|
|
|
|
---
|
|
|
|
|
# Internal function, not address-taken in this module, so no BTI needed.
|
|
|
|
|
name: simple_internal
|
|
|
|
|
body: |
|
|
|
|
|
bb.0.entry:
|
|
|
|
|
; CHECK-LABEL: name: simple_internal
|
|
|
|
|
; CHECK-NOT: HINT
|
|
|
|
|
; CHECK: RET
|
|
|
|
|
$w0 = ORRWrs $wzr, $wzr, 0
|
|
|
|
|
RET undef $lr, implicit killed $w0
|
|
|
|
|
|
|
|
|
|
---
|
|
|
|
|
# Function starts with PACIASP, which implicitly acts as BTI JC, so no change
|
|
|
|
|
# needed.
|
|
|
|
|
name: ptr_auth
|
|
|
|
|
stack:
|
|
|
|
|
- { id: 0, name: '', type: spill-slot, offset: -16, size: 8, alignment: 16,
|
2019-06-17 17:13:29 +08:00
|
|
|
stack-id: default, callee-saved-register: '$lr', callee-saved-restored: true,
|
[AArch64][v8.5A] Branch Target Identification code-generation pass
The Branch Target Identification extension, introduced to AArch64 in
Armv8.5-A, adds the BTI instruction, which is used to mark valid targets
of indirect branches. When enabled, the processor will trap if an
instruction in a protected page tries to perform an indirect branch to
any instruction other than a BTI. The BTI instruction uses encodings
which were NOPs in earlier versions of the architecture, so BTI-enabled
code will still run on earlier hardware, just without the extra
protection.
There are 3 variants of the BTI instruction, which are valid targets for
different kinds or branches:
- BTI C can be targeted by call instructions, and is inteneded to be
used at function entry points. These are the BLR instruction, as well
as BR with x16 or x17. These BR instructions are allowed for use in
PLT entries, and we can also use them to allow indirect tail-calls.
- BTI J can be targeted by BR only, and is intended to be used by jump
tables.
- BTI JC acts ab both a BTI C and a BTI J instruction, and can be
targeted by any BLR or BR instruction.
Note that RET instructions are not restricted by branch target
identification, the reason for this is that return addresses can be
protected more effectively using return address signing. Direct branches
and calls are also unaffected, as it is assumed that an attacker cannot
modify executable pages (if they could, they wouldn't need to do a
ROP/JOP attack).
This patch adds a MachineFunctionPass which:
- Adds a BTI C at the start of every function which could be indirectly
called (either because it is address-taken, or externally visible so
could be address-taken in another translation unit).
- Adds a BTI J at the start of every basic block which could be
indirectly branched to. This could be either done by a jump table, or
by taking the address of the block (e.g. the using GCC label values
extension).
We only need to use BTI JC when a function is indirectly-callable, and
takes the address of the entry block. I've not been able to trigger this
from C or IR, but I've included a MIR test just in case.
Using BTI C at function entries relies on the fact that no other code in
BTI-protected pages uses indirect tail-calls, unless they use x16 or x17
to hold the address. I'll add that code-generation restriction as a
separate patch.
Differential revision: https://reviews.llvm.org/D52867
llvm-svn: 343967
2018-10-08 22:04:24 +08:00
|
|
|
debug-info-variable: '', debug-info-expression: '', debug-info-location: '' }
|
|
|
|
|
body: |
|
|
|
|
|
bb.0.entry:
|
|
|
|
|
liveins: $lr
|
|
|
|
|
|
|
|
|
|
; CHECK-LABEL: name: ptr_auth
|
|
|
|
|
; CHECK-NOT: HINT
|
|
|
|
|
; CHECK: frame-setup PACIASP
|
|
|
|
|
; CHECK-NOT: HINT
|
|
|
|
|
; CHECK: RETAA
|
|
|
|
|
frame-setup PACIASP implicit-def $lr, implicit killed $lr, implicit $sp
|
|
|
|
|
early-clobber $sp = frame-setup STRXpre killed $lr, $sp, -16 :: (store 8 into %stack.0)
|
|
|
|
|
INLINEASM &"", 1, 12, implicit-def dead early-clobber $lr
|
|
|
|
|
$w0 = ORRWrs $wzr, $wzr, 0
|
|
|
|
|
early-clobber $sp, $lr = frame-destroy LDRXpost $sp, 16 :: (load 8 from %stack.0)
|
2019-06-26 09:44:39 +08:00
|
|
|
RETAA implicit $sp, implicit $lr, implicit killed $w0
|
[AArch64][v8.5A] Branch Target Identification code-generation pass
The Branch Target Identification extension, introduced to AArch64 in
Armv8.5-A, adds the BTI instruction, which is used to mark valid targets
of indirect branches. When enabled, the processor will trap if an
instruction in a protected page tries to perform an indirect branch to
any instruction other than a BTI. The BTI instruction uses encodings
which were NOPs in earlier versions of the architecture, so BTI-enabled
code will still run on earlier hardware, just without the extra
protection.
There are 3 variants of the BTI instruction, which are valid targets for
different kinds or branches:
- BTI C can be targeted by call instructions, and is inteneded to be
used at function entry points. These are the BLR instruction, as well
as BR with x16 or x17. These BR instructions are allowed for use in
PLT entries, and we can also use them to allow indirect tail-calls.
- BTI J can be targeted by BR only, and is intended to be used by jump
tables.
- BTI JC acts ab both a BTI C and a BTI J instruction, and can be
targeted by any BLR or BR instruction.
Note that RET instructions are not restricted by branch target
identification, the reason for this is that return addresses can be
protected more effectively using return address signing. Direct branches
and calls are also unaffected, as it is assumed that an attacker cannot
modify executable pages (if they could, they wouldn't need to do a
ROP/JOP attack).
This patch adds a MachineFunctionPass which:
- Adds a BTI C at the start of every function which could be indirectly
called (either because it is address-taken, or externally visible so
could be address-taken in another translation unit).
- Adds a BTI J at the start of every basic block which could be
indirectly branched to. This could be either done by a jump table, or
by taking the address of the block (e.g. the using GCC label values
extension).
We only need to use BTI JC when a function is indirectly-callable, and
takes the address of the entry block. I've not been able to trigger this
from C or IR, but I've included a MIR test just in case.
Using BTI C at function entries relies on the fact that no other code in
BTI-protected pages uses indirect tail-calls, unless they use x16 or x17
to hold the address. I'll add that code-generation restriction as a
separate patch.
Differential revision: https://reviews.llvm.org/D52867
llvm-svn: 343967
2018-10-08 22:04:24 +08:00
|
|
|
|
|
|
|
|
---
|
|
|
|
|
# Function starts with PACIBSP, which implicitly acts as BTI JC, so no change
|
|
|
|
|
# needed.
|
|
|
|
|
name: ptr_auth_b
|
|
|
|
|
stack:
|
|
|
|
|
- { id: 0, name: '', type: spill-slot, offset: -16, size: 8, alignment: 16,
|
2019-06-17 17:13:29 +08:00
|
|
|
stack-id: default, callee-saved-register: '$lr', callee-saved-restored: true,
|
[AArch64][v8.5A] Branch Target Identification code-generation pass
The Branch Target Identification extension, introduced to AArch64 in
Armv8.5-A, adds the BTI instruction, which is used to mark valid targets
of indirect branches. When enabled, the processor will trap if an
instruction in a protected page tries to perform an indirect branch to
any instruction other than a BTI. The BTI instruction uses encodings
which were NOPs in earlier versions of the architecture, so BTI-enabled
code will still run on earlier hardware, just without the extra
protection.
There are 3 variants of the BTI instruction, which are valid targets for
different kinds or branches:
- BTI C can be targeted by call instructions, and is inteneded to be
used at function entry points. These are the BLR instruction, as well
as BR with x16 or x17. These BR instructions are allowed for use in
PLT entries, and we can also use them to allow indirect tail-calls.
- BTI J can be targeted by BR only, and is intended to be used by jump
tables.
- BTI JC acts ab both a BTI C and a BTI J instruction, and can be
targeted by any BLR or BR instruction.
Note that RET instructions are not restricted by branch target
identification, the reason for this is that return addresses can be
protected more effectively using return address signing. Direct branches
and calls are also unaffected, as it is assumed that an attacker cannot
modify executable pages (if they could, they wouldn't need to do a
ROP/JOP attack).
This patch adds a MachineFunctionPass which:
- Adds a BTI C at the start of every function which could be indirectly
called (either because it is address-taken, or externally visible so
could be address-taken in another translation unit).
- Adds a BTI J at the start of every basic block which could be
indirectly branched to. This could be either done by a jump table, or
by taking the address of the block (e.g. the using GCC label values
extension).
We only need to use BTI JC when a function is indirectly-callable, and
takes the address of the entry block. I've not been able to trigger this
from C or IR, but I've included a MIR test just in case.
Using BTI C at function entries relies on the fact that no other code in
BTI-protected pages uses indirect tail-calls, unless they use x16 or x17
to hold the address. I'll add that code-generation restriction as a
separate patch.
Differential revision: https://reviews.llvm.org/D52867
llvm-svn: 343967
2018-10-08 22:04:24 +08:00
|
|
|
debug-info-variable: '', debug-info-expression: '', debug-info-location: '' }
|
|
|
|
|
body: |
|
|
|
|
|
bb.0.entry:
|
|
|
|
|
liveins: $lr
|
|
|
|
|
|
|
|
|
|
; CHECK-LABEL: name: ptr_auth_b
|
|
|
|
|
; CHECK-NOT: HINT
|
|
|
|
|
; CHECK: frame-setup PACIBSP
|
|
|
|
|
; CHECK-NOT: HINT
|
|
|
|
|
; CHECK: RETAB
|
|
|
|
|
frame-setup PACIBSP implicit-def $lr, implicit killed $lr, implicit $sp
|
|
|
|
|
early-clobber $sp = frame-setup STRXpre killed $lr, $sp, -16 :: (store 8 into %stack.0)
|
|
|
|
|
INLINEASM &"", 1, 12, implicit-def dead early-clobber $lr
|
|
|
|
|
$w0 = ORRWrs $wzr, $wzr, 0
|
|
|
|
|
early-clobber $sp, $lr = frame-destroy LDRXpost $sp, 16 :: (load 8 from %stack.0)
|
2019-06-26 09:44:39 +08:00
|
|
|
RETAB implicit $sp, implicit $lr, implicit killed $w0
|
[AArch64][v8.5A] Branch Target Identification code-generation pass
The Branch Target Identification extension, introduced to AArch64 in
Armv8.5-A, adds the BTI instruction, which is used to mark valid targets
of indirect branches. When enabled, the processor will trap if an
instruction in a protected page tries to perform an indirect branch to
any instruction other than a BTI. The BTI instruction uses encodings
which were NOPs in earlier versions of the architecture, so BTI-enabled
code will still run on earlier hardware, just without the extra
protection.
There are 3 variants of the BTI instruction, which are valid targets for
different kinds or branches:
- BTI C can be targeted by call instructions, and is inteneded to be
used at function entry points. These are the BLR instruction, as well
as BR with x16 or x17. These BR instructions are allowed for use in
PLT entries, and we can also use them to allow indirect tail-calls.
- BTI J can be targeted by BR only, and is intended to be used by jump
tables.
- BTI JC acts ab both a BTI C and a BTI J instruction, and can be
targeted by any BLR or BR instruction.
Note that RET instructions are not restricted by branch target
identification, the reason for this is that return addresses can be
protected more effectively using return address signing. Direct branches
and calls are also unaffected, as it is assumed that an attacker cannot
modify executable pages (if they could, they wouldn't need to do a
ROP/JOP attack).
This patch adds a MachineFunctionPass which:
- Adds a BTI C at the start of every function which could be indirectly
called (either because it is address-taken, or externally visible so
could be address-taken in another translation unit).
- Adds a BTI J at the start of every basic block which could be
indirectly branched to. This could be either done by a jump table, or
by taking the address of the block (e.g. the using GCC label values
extension).
We only need to use BTI JC when a function is indirectly-callable, and
takes the address of the entry block. I've not been able to trigger this
from C or IR, but I've included a MIR test just in case.
Using BTI C at function entries relies on the fact that no other code in
BTI-protected pages uses indirect tail-calls, unless they use x16 or x17
to hold the address. I'll add that code-generation restriction as a
separate patch.
Differential revision: https://reviews.llvm.org/D52867
llvm-svn: 343967
2018-10-08 22:04:24 +08:00
|
|
|
|
|
|
|
|
---
|
|
|
|
|
# Function contains a jump table, so every target of the jump table must start
|
|
|
|
|
# with BTI J.
|
|
|
|
|
name: jump_table
|
|
|
|
|
jumpTable:
|
|
|
|
|
kind: block-address
|
|
|
|
|
entries:
|
|
|
|
|
- id: 0
|
|
|
|
|
blocks: [ '%bb.2', '%bb.3', '%bb.4', '%bb.5', '%bb.6' ]
|
|
|
|
|
body: |
|
|
|
|
|
bb.0.entry:
|
|
|
|
|
; CHECK-LABEL: name: jump_table
|
|
|
|
|
; CHECK: HINT 34
|
|
|
|
|
successors: %bb.7(0x15555555), %bb.1(0x6aaaaaab)
|
|
|
|
|
liveins: $w0
|
|
|
|
|
|
|
|
|
|
renamable $w8 = SUBWri killed renamable $w0, 1, 0, implicit-def $x8
|
|
|
|
|
dead $wzr = SUBSWri renamable $w8, 4, 0, implicit-def $nzcv
|
|
|
|
|
Bcc 8, %bb.7, implicit $nzcv
|
|
|
|
|
|
|
|
|
|
bb.1.entry:
|
|
|
|
|
; CHECK: bb.1.entry:
|
|
|
|
|
; CHECK-NOT: HINT
|
|
|
|
|
; CHECK: BR killed renamable $x8
|
|
|
|
|
successors: %bb.2(0x1999999a), %bb.3(0x1999999a), %bb.4(0x1999999a), %bb.5(0x1999999a), %bb.6(0x1999999a)
|
|
|
|
|
liveins: $x8
|
|
|
|
|
|
|
|
|
|
$x9 = ADRP target-flags(aarch64-page) %jump-table.0
|
|
|
|
|
renamable $x9 = ADDXri killed $x9, target-flags(aarch64-pageoff, aarch64-nc) %jump-table.0, 0
|
|
|
|
|
renamable $x8 = LDRXroX killed renamable $x9, killed renamable $x8, 0, 1 :: (load 8 from jump-table)
|
|
|
|
|
BR killed renamable $x8
|
|
|
|
|
|
|
|
|
|
bb.2.sw.bb:
|
|
|
|
|
; CHECK: bb.2.sw.bb
|
|
|
|
|
; CHECK-NEXT: HINT 36
|
|
|
|
|
$w0 = ORRWrs $wzr, $wzr, 0
|
|
|
|
|
INLINEASM &"", 1
|
|
|
|
|
RET undef $lr, implicit killed $w0
|
|
|
|
|
|
|
|
|
|
bb.3.sw.bb1:
|
|
|
|
|
; CHECK: bb.3.sw.bb1
|
|
|
|
|
; CHECK-NEXT: HINT 36
|
|
|
|
|
$w0 = ORRWrs $wzr, $wzr, 0
|
|
|
|
|
INLINEASM &"", 1
|
|
|
|
|
RET undef $lr, implicit killed $w0
|
|
|
|
|
|
|
|
|
|
bb.4.sw.bb2:
|
|
|
|
|
; CHECK: bb.4.sw.bb2
|
|
|
|
|
; CHECK-NEXT: HINT 36
|
|
|
|
|
$w0 = ORRWrs $wzr, $wzr, 0
|
|
|
|
|
INLINEASM &"", 1
|
|
|
|
|
RET undef $lr, implicit killed $w0
|
|
|
|
|
|
|
|
|
|
bb.5.sw.bb3:
|
|
|
|
|
; CHECK: bb.5.sw.bb3
|
|
|
|
|
; CHECK-NEXT: HINT 36
|
|
|
|
|
$w0 = ORRWrs $wzr, $wzr, 0
|
|
|
|
|
INLINEASM &"", 1
|
|
|
|
|
RET undef $lr, implicit killed $w0
|
|
|
|
|
|
|
|
|
|
bb.6.sw.bb4:
|
|
|
|
|
; CHECK: bb.6.sw.bb4
|
|
|
|
|
; CHECK-NEXT: successors: %bb.7(0x80000000)
|
|
|
|
|
; CHECK-NEXT: {{ }}
|
|
|
|
|
; CHECK-NEXT: HINT 36
|
|
|
|
|
successors: %bb.7(0x80000000)
|
|
|
|
|
|
|
|
|
|
INLINEASM &"", 1
|
|
|
|
|
|
|
|
|
|
bb.7.sw.epilog:
|
|
|
|
|
; CHECK: bb.7.sw.epilog:
|
|
|
|
|
; CHECK-NOT: HINT
|
|
|
|
|
; CHECK: RET
|
|
|
|
|
$w0 = ORRWrs $wzr, $wzr, 0
|
|
|
|
|
RET undef $lr, implicit killed $w0
|
|
|
|
|
|
|
|
|
|
---
|
|
|
|
|
# Function takes address of basic blocks, so they must start with BTI J.
|
|
|
|
|
name: label_address
|
|
|
|
|
body: |
|
|
|
|
|
bb.0.entry:
|
|
|
|
|
; CHECK-LABEL: label_address
|
|
|
|
|
; CHECK: bb.0.entry:
|
|
|
|
|
; CHECK-NEXT: successors: %bb.1(0x40000000), %bb.2(0x40000000)
|
|
|
|
|
; CHECK-NEXT: {{ }}
|
|
|
|
|
; CHECK-NEXT: HINT 34
|
|
|
|
|
; CHECK: BR killed renamable $x9
|
|
|
|
|
successors: %bb.1(0x40000000), %bb.2(0x40000000)
|
|
|
|
|
|
|
|
|
|
renamable $x8 = ADRP target-flags(aarch64-page) @label_address.addr
|
|
|
|
|
renamable $x9 = LDRXui renamable $x8, target-flags(aarch64-pageoff, aarch64-nc) @label_address.addr :: (dereferenceable load 8 from @label_address.addr)
|
|
|
|
|
BR killed renamable $x9
|
|
|
|
|
|
|
|
|
|
bb.1.return (address-taken):
|
|
|
|
|
; CHECK: bb.1.return (address-taken):
|
|
|
|
|
; CHECK-NEXT: HINT 36
|
|
|
|
|
liveins: $x8
|
|
|
|
|
|
|
|
|
|
$x9 = ADRP target-flags(aarch64-page) blockaddress(@label_address, %ir-block.lab2)
|
|
|
|
|
renamable $w0 = ORRWri $wzr, 0
|
|
|
|
|
renamable $x9 = ADDXri killed $x9, target-flags(aarch64-pageoff, aarch64-nc) blockaddress(@label_address, %ir-block.lab2), 0
|
|
|
|
|
STRXui killed renamable $x9, killed renamable $x8, target-flags(aarch64-pageoff, aarch64-nc) @label_address.addr :: (store 8 into @label_address.addr)
|
|
|
|
|
RET undef $lr, implicit killed $w0
|
|
|
|
|
|
|
|
|
|
bb.2.lab2 (address-taken):
|
|
|
|
|
; CHECK: bb.2.lab2 (address-taken):
|
|
|
|
|
; CHECK-NEXT: HINT 36
|
|
|
|
|
liveins: $x8
|
|
|
|
|
|
|
|
|
|
$x9 = ADRP target-flags(aarch64-page) blockaddress(@label_address, %ir-block.return)
|
|
|
|
|
renamable $w0 = ORRWri $wzr, 1984
|
|
|
|
|
renamable $x9 = ADDXri killed $x9, target-flags(aarch64-pageoff, aarch64-nc) blockaddress(@label_address, %ir-block.return), 0
|
|
|
|
|
STRXui killed renamable $x9, killed renamable $x8, target-flags(aarch64-pageoff, aarch64-nc) @label_address.addr :: (store 8 into @label_address.addr)
|
|
|
|
|
RET undef $lr, implicit killed $w0
|
|
|
|
|
|
|
|
|
|
---
|
|
|
|
|
# Function takes address of the entry block, so the entry block needs a BTI JC.
|
|
|
|
|
name: label_address_entry
|
|
|
|
|
body: |
|
|
|
|
|
bb.0.entry (address-taken):
|
|
|
|
|
; CHECK-LABEL: label_address_entry
|
|
|
|
|
; CHECK: bb.0.entry (address-taken):
|
|
|
|
|
; CHECK-NEXT: successors: %bb.1(0x40000000), %bb.2(0x40000000)
|
|
|
|
|
; CHECK-NEXT: {{ }}
|
|
|
|
|
; CHECK-NEXT: HINT 38
|
|
|
|
|
; CHECK: BR killed renamable $x9
|
|
|
|
|
successors: %bb.1(0x40000000), %bb.2(0x40000000)
|
|
|
|
|
|
|
|
|
|
renamable $x8 = ADRP target-flags(aarch64-page) @label_address.addr
|
|
|
|
|
renamable $x9 = LDRXui renamable $x8, target-flags(aarch64-pageoff, aarch64-nc) @label_address.addr :: (dereferenceable load 8 from @label_address.addr)
|
|
|
|
|
BR killed renamable $x9
|
|
|
|
|
|
|
|
|
|
bb.1.return (address-taken):
|
|
|
|
|
; CHECK: bb.1.return (address-taken):
|
|
|
|
|
; CHECK-NEXT: HINT 36
|
|
|
|
|
liveins: $x8
|
|
|
|
|
|
|
|
|
|
$x9 = ADRP target-flags(aarch64-page) blockaddress(@label_address, %ir-block.entry)
|
|
|
|
|
renamable $w0 = ORRWri $wzr, 0
|
|
|
|
|
renamable $x9 = ADDXri killed $x9, target-flags(aarch64-pageoff, aarch64-nc) blockaddress(@label_address, %ir-block.entry), 0
|
|
|
|
|
STRXui killed renamable $x9, killed renamable $x8, target-flags(aarch64-pageoff, aarch64-nc) @label_address.addr :: (store 8 into @label_address.addr)
|
|
|
|
|
RET undef $lr, implicit killed $w0
|
|
|
|
|
|
|
|
|
|
bb.2.lab2:
|
|
|
|
|
; CHECK: bb.2.lab2:
|
|
|
|
|
; CHECK-NOT: HINT
|
|
|
|
|
liveins: $x8
|
|
|
|
|
|
|
|
|
|
$x9 = ADRP target-flags(aarch64-page) blockaddress(@label_address, %ir-block.return)
|
|
|
|
|
renamable $w0 = ORRWri $wzr, 1984
|
|
|
|
|
renamable $x9 = ADDXri killed $x9, target-flags(aarch64-pageoff, aarch64-nc) blockaddress(@label_address, %ir-block.return), 0
|
|
|
|
|
STRXui killed renamable $x9, killed renamable $x8, target-flags(aarch64-pageoff, aarch64-nc) @label_address.addr :: (store 8 into @label_address.addr)
|
|
|
|
|
RET undef $lr, implicit killed $w0
|
2020-02-13 18:42:39 +08:00
|
|
|
---
|
|
|
|
|
# When PACIASP is the first real instruction in the functions then BTI should not be inserted.
|
|
|
|
|
name: debug_ptr_auth
|
|
|
|
|
stack:
|
|
|
|
|
- { id: 0, name: '', type: spill-slot, offset: -16, size: 8, alignment: 16,
|
|
|
|
|
stack-id: default, callee-saved-register: '$lr', callee-saved-restored: true,
|
|
|
|
|
debug-info-variable: '', debug-info-expression: '', debug-info-location: '' }
|
|
|
|
|
body: |
|
|
|
|
|
bb.0.entry:
|
|
|
|
|
liveins: $lr
|
|
|
|
|
|
|
|
|
|
; CHECK-LABEL: name: debug_ptr_auth
|
|
|
|
|
; CHECK-NOT: HINT
|
|
|
|
|
; CHECK: DBG_VALUE
|
|
|
|
|
; CHECK: frame-setup PACIASP
|
|
|
|
|
; CHECK-NOT: HINT
|
|
|
|
|
; CHECK: RETAA
|
|
|
|
|
DBG_VALUE $lr
|
|
|
|
|
frame-setup PACIASP implicit-def $lr, implicit killed $lr, implicit $sp
|
|
|
|
|
frame-setup CFI_INSTRUCTION negate_ra_sign_state
|
|
|
|
|
early-clobber $sp = frame-setup STRXpre killed $lr, $sp, -16 :: (store 8 into %stack.0)
|
|
|
|
|
INLINEASM &"", 1, 12, implicit-def dead early-clobber $lr
|
|
|
|
|
$w0 = ORRWrs $wzr, $wzr, 0
|
|
|
|
|
early-clobber $sp, $lr = frame-destroy LDRXpost $sp, 16 :: (load 8 from %stack.0)
|
|
|
|
|
RETAA implicit $sp, implicit $lr, implicit killed $w0
|
[AArch64][v8.5A] Branch Target Identification code-generation pass
The Branch Target Identification extension, introduced to AArch64 in
Armv8.5-A, adds the BTI instruction, which is used to mark valid targets
of indirect branches. When enabled, the processor will trap if an
instruction in a protected page tries to perform an indirect branch to
any instruction other than a BTI. The BTI instruction uses encodings
which were NOPs in earlier versions of the architecture, so BTI-enabled
code will still run on earlier hardware, just without the extra
protection.
There are 3 variants of the BTI instruction, which are valid targets for
different kinds or branches:
- BTI C can be targeted by call instructions, and is inteneded to be
used at function entry points. These are the BLR instruction, as well
as BR with x16 or x17. These BR instructions are allowed for use in
PLT entries, and we can also use them to allow indirect tail-calls.
- BTI J can be targeted by BR only, and is intended to be used by jump
tables.
- BTI JC acts ab both a BTI C and a BTI J instruction, and can be
targeted by any BLR or BR instruction.
Note that RET instructions are not restricted by branch target
identification, the reason for this is that return addresses can be
protected more effectively using return address signing. Direct branches
and calls are also unaffected, as it is assumed that an attacker cannot
modify executable pages (if they could, they wouldn't need to do a
ROP/JOP attack).
This patch adds a MachineFunctionPass which:
- Adds a BTI C at the start of every function which could be indirectly
called (either because it is address-taken, or externally visible so
could be address-taken in another translation unit).
- Adds a BTI J at the start of every basic block which could be
indirectly branched to. This could be either done by a jump table, or
by taking the address of the block (e.g. the using GCC label values
extension).
We only need to use BTI JC when a function is indirectly-callable, and
takes the address of the entry block. I've not been able to trigger this
from C or IR, but I've included a MIR test just in case.
Using BTI C at function entries relies on the fact that no other code in
BTI-protected pages uses indirect tail-calls, unless they use x16 or x17
to hold the address. I'll add that code-generation restriction as a
separate patch.
Differential revision: https://reviews.llvm.org/D52867
llvm-svn: 343967
2018-10-08 22:04:24 +08:00
|
|
|
|
|
|
|
|
...
|