Summary:
Commit
b684c1a50f70 ("Add a `Symbolizer::GetEnvP()` method that allows
symbolizer implementations to customise the environment of the
symbolizer binary.") exposed a latent ARM issue, and that broke
http://lab.llvm.org:8011/builders/clang-cmake-thumbv7-full-sh
This coincided with breakage caused by my commit
5f5fb56c68e4
("[compiler-rt] Intercept the uname() function"), so I had to
investigate.
The issue is that GetArgsAndEnv does not work on ARM: there glibc's
_start overwrites argc value stored at __libc_start_end, breaking the
existing argv/envp parsing logic.
Fix by inferring argc from argv.
Reviewers: eugenis, vitalybuka
Reviewed By: eugenis
Subscribers: dberris, kristof.beyls, danielkiss, #sanitizers, delcypher
Tags: #sanitizers
Differential Revision: https://reviews.llvm.org/D77400
#if !SANITIZER_GO
if (&__libc_stack_end) {
uptr* stack_end = (uptr*)__libc_stack_end;
- int argc = *stack_end;
+ // Normally argc can be obtained from *stack_end, however, on ARM glibc's
+ // _start clobbers it:
+ // https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/arm/start.S;hb=refs/heads/release/2.31/master#l75
+ // Do not special-case ARM and infer argc from argv everywhere.
+ int argc = 0;
+ while (stack_end[argc + 1]) argc++;
*argv = (char**)(stack_end + 1);
*envp = (char**)(stack_end + argc + 2);
} else {