17d553d299
2 Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
David Benjamin
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17d553d299 |
Add a CFI tester to CHECK_ABI.
This uses the x86 trap flag and libunwind to test CFI works at each instruction. For now, it just uses the system one out of pkg-config and disables unwind tests if unavailable. We'll probably want to stick a copy into //third_party and perhaps try the LLVM one later. This tester caught two bugs in P-256 CFI annotations already: I47b5f9798b3bcee1748e537b21c173d312a14b42 and I9f576d868850312d6c14d1386f8fbfa85021b347 An earlier design used PTRACE_SINGLESTEP with libunwind's remote unwinding features. ptrace is a mess around stop signals (see group-stop discussion in ptrace(2)) and this is 10x faster, so I went with it. The question of which is more future-proof is complex: - There are two libunwinds with the same API, https://www.nongnu.org/libunwind/ and LLVM's. This currently uses the system nongnu.org for convenience. In future, LLVM's should be easier to bundle (less complex build) and appears to even support Windows, but I haven't tested this. Moreover, setting the trap flag keeps the test single-process, which is less complex on Windows. That suggests the trap flag design and switching to LLVM later. However... - Not all architectures have a trap flag settable by userspace. As far as I can tell, ARMv8's PSTATE.SS can only be set from the kernel. If we stick with nongnu.org libunwind, we can use PTRACE_SINGLESTEP and remote unwinding. Or we implement it for LLVM. Another thought is for the ptracer to bounce SIGTRAP back into the process, to share the local unwinding code. - ARMv7 has no trap flag at all and PTRACE_SINGLESTEP fails. Debuggers single-step by injecting breakpoints instead. However, ARMv8's trap flag seems to work in both AArch32 and AArch64 modes, so we may be able to condition it on a 64-bit kernel. Sadly, neither strategy works with Intel SDE. Adding flags to cpucap vectors as we do with ARM would help, but it would not emulate CPUs newer than the host CPU. For now, I've just had SDE tests disable these. Annoyingly, CMake does not allow object libraries to have dependencies, so make test_support a proper static library. Rename the target to test_support_lib to avoid https://gitlab.kitware.com/cmake/cmake/issues/17785 Update-Note: This adds a new optional test dependency, but it's disabled by default (define BORINGSSL_HAVE_LIBUNWIND), so consumers do not need to do anything. We'll probably want to adjust this in the future. Bug: 181 Change-Id: I817263d7907aff0904a9cee83f8b26747262cc0c Reviewed-on: https://boringssl-review.googlesource.com/c/33966 Commit-Queue: David Benjamin <davidben@google.com> Reviewed-by: Adam Langley <agl@google.com> |
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David Benjamin
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54efa1afc0 |
Add an ABI testing framework.
Dear reader, I must apologize in advance. This CL contains the following: - A new 256-line perlasm file with non-trivial perl bits and a dual-ABI variadic function caller. - C preprocessor gymnastics, with variadic macros and fun facts about __VA_ARGS__'s behavior on empty argument lists. - C++ template gymnastics, including variadic arguments, template specialization, std::enable_if, and machinery to control template argument deduction. Enjoy. This tests that our assembly functions correctly honor platform ABI conventions. Right now this only tests callee-saved registers, but it should be extendable to SEH/CFI unwind testing with single-step debugging APIs. Register-checking does not involve anything funny and should be compatible with SDE. (The future unwind testing is unlikely to be compatible.) This CL adds support for x86_64 SysV and Win64 ABIs. ARM, AArch64, and x86 can be added in the future. The testing is injected in two places. First, all the assembly tests in p256-x86_64-test.cc are now instrumented. This is the intended workflow and should capture all registers. However, we currently do not unit-test our assembly much directly. We should do that as follow-up work[0] but, in the meantime, I've also wrapped all of the GTest main function in an ABI test. This is imperfect as ABI failures may be masked by other stack frames, but it costs nothing[1] and is pretty reliable at catching Win64 xmm register failures. [0] An alternate strategy would be, in debug builds, unconditionally instrument every assembly call in libcrypto. But the CHECK_ABI macro would be difficult to replicate in pure C, and unwind testing may be too invasive for this. Still, something to consider when we C++ libcrypto. [1] When single-stepped unwind testing exists, it won't cost nothing. The gtest_main.cc call will turn unwind testing off. Change-Id: I6643b26445891fd46abfacac52bc024024c8d7f6 Reviewed-on: https://boringssl-review.googlesource.com/c/33764 Reviewed-by: Adam Langley <agl@google.com> Reviewed-by: Adam Langley <alangley@gmail.com> Commit-Queue: David Benjamin <davidben@google.com> |