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>
Unwind testing will make CHECK_ABI much slower. The original
ptrace-based design is some 10,000x slower. I've found an alternate
design that's a mere 1,000x slower, but this probably warrants being
more straightforward. It also removes the weirdness where NDEBUG
controlled which tests were run.
While it does mean we need to write some extra tests for p256-x86_64.pl,
we otherwise do not directly unit test our assembly anyway. Usually we
test the public crypto APIs themselves. So, for most files, this isn't
actually extra work.
Bug: 181
Change-Id: I7cbb7f930c2ea6ae32a201da503dcd36844704f0
Reviewed-on: https://boringssl-review.googlesource.com/c/33965
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: Adam Langley <agl@google.com>
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>
