When used in cross-DSO mode, CFI will generate calls to special functions rather than trap instructions. For example, instead of generating
if (!InlinedFastCheck(f))
abort();
call *f
CFI generates
if (!InlinedFastCheck(f))
__cfi_slowpath(CallSiteTypeId, f);
call *f
This patch teaches cfi-verify to recognize calls to __cfi_slowpath and abort and treat them as trap functions.
In addition to normal symbols, we also parse the dynamic relocations to handle cross-DSO calls in libraries.
We also extend cfi-verify to recognize other patterns that occur using cross-DSO. For example, some indirect calls are not guarded by a branch to a trap but instead follow a call to __cfi_slowpath. For example:
if (!InlinedFastCheck(f))
call *f
else {
__cfi_slowpath(CallSiteTypeId, f);
call *f
}
In this case, the second call to f is not marked as protected by the current code. We thus recognize if indirect calls directly follow a call to a function that will trap on CFI violations and treat them as protected.
We also ignore indirect calls in the PLT, since on AArch64 each entry contains an indirect call that should not be protected by CFI, and these are labeled incorrectly when debug information is not present.
Differential Revision: https://reviews.llvm.org/D49383
llvm-svn: 340612
This patch adds support for AArch64 to cfi-verify.
This required three changes to cfi-verify. First, it generalizes checking if an instruction is a trap by adding a new isTrap flag to TableGen (and defining it for x86 and AArch64). Second, the code that ensures that the operand register is not clobbered between the CFI check and the indirect call needs to allow a single dereference (in x86 this happens as part of the jump instruction). Third, we needed to ensure that return instructions are not counted as indirect branches. Technically, returns are indirect branches and can be covered by CFI, but LLVM's forward-edge CFI does not protect them, and x86 does not consider them, so we keep that behavior.
In addition, we had to improve AArch64's code to evaluate the branch target of a MCInst to handle calls where the destination is not the first operand (which it often is not).
Differential Revision: https://reviews.llvm.org/D48836
llvm-svn: 337007
Summary:
This patch adds another failure mode for `validateCFIProtection(..)`, wherein any register that affects the indirect control flow instruction is clobbered to between the CFI-check and the instruction's execution.
Also includes a modification to make MCInstrDesc::hasDefOfPhysReg public.
Reviewers: vlad.tsyrklevich
Reviewed By: vlad.tsyrklevich
Subscribers: llvm-commits, pcc, kcc
Differential Revision: https://reviews.llvm.org/D39820
llvm-svn: 318238
Allows users to view GraphResult objects in a DOT directed-graph format. This feature can be turned on through the --print-graphs flag.
Also enabled pretty-printing of instructions in output. Together these features make analysis of unprotected CF instructions much easier by providing a visual control flow graph.
Reviewers: pcc
Subscribers: llvm-commits, kcc, vlad.tsyrklevich
Differential Revision: https://reviews.llvm.org/D39819
llvm-svn: 318211
Refactors the behaviour of building graphs out of FileAnalysis, allowing for analysis of the GraphResult by the callee without having to rebuild the graph. Means when we want to analyse the constructed graph (planned for later revisions), we don't do repeated work.
Also makes CFI verification in FileAnalysis now return an enum that allows us to differentiate why something failed, not just that it did/didn't fail.
Reviewers: vlad.tsyrklevich
Subscribers: kcc, pcc, llvm-commits
Differential Revision: https://reviews.llvm.org/D39764
llvm-svn: 317927
Adds blacklist parsing behaviour for filtering results into four categories:
- Expected Protected: Things that are not in the blacklist and are protected.
- Unexpected Protected: Things that are in the blacklist and are protected.
- Expected Unprotected: Things that are in the blacklist and are unprotected.
- Unexpected Unprotected: Things that are not in the blacklist and are unprotected.
now can optionally be invoked with a second command line argument, which specifies the blacklist file that the binary was built with.
Current statistics for chromium:
Reviewers: vlad.tsyrklevich
Subscribers: mgorny, llvm-commits, pcc, kcc
Differential Revision: https://reviews.llvm.org/D39525
llvm-svn: 317364
Summary: Help differentiate code and data by parsing DWARF information. This will reduce false positive rates where data is placed in executable sections and is mistakenly parsed as code, resulting in an inflation in the number of indirect CF instructions (and hence an inflation of the number of unprotected).
Also prints the DWARF line data around the region of each indirect CF instruction.
Reviewers: pcc
Subscribers: probinson, llvm-commits, vlad.tsyrklevich, mgorny, aprantl, kcc
Differential Revision: https://reviews.llvm.org/D38654
llvm-svn: 317050
Add a CFI protection check that is implemented by building a graph and inspecting the output to deduce if the indirect CF instruction is CFI protected. Also added the output of this instruction to printIndirectInstructions().
Reviewers: vlad.tsyrklevich
Subscribers: llvm-commits, kcc, pcc, mgorny
Differential Revision: https://reviews.llvm.org/D38428
llvm-svn: 316610
Implement a localised graph builder for indirect control flow
instructions. Main interface is through GraphBuilder::buildFlowGraph,
which will build a flow graph around an indirect CF instruction. Various
modifications to FileVerifier are also made to const-expose some members
needed for machine code analysis done by the graph builder.
Reviewers: vlad.tsyrklevich
Reviewed By: vlad.tsyrklevich
Subscribers: llvm-commits, kcc, pcc
Differential Revision: https://reviews.llvm.org/D38427
llvm-svn: 316372
Summary: Move llvm-cfi-verify into a class in preparation for CFI analysis to come.
Reviewers: vlad.tsyrklevich
Reviewed By: vlad.tsyrklevich
Subscribers: mgorny, llvm-commits, pcc, kcc
Differential Revision: https://reviews.llvm.org/D38379
llvm-svn: 315504
Joel Galenson