[sanitizer_common] Fix GetArgsAndEnv on Linux/sparc64

[rorth]

When ASan testing is enabled on SPARC as per PR #107405, the

  AddressSanitizer-sparc-linux :: TestCases/Posix/print_cmdline.cpp

test FAILs. Either ASAN_OPTIONS=print_cmdline=true yielded binary garbage in the Command: output or just an empty string.

It turns out one needs to apply an offset to __libc_stack_end to get at the actual argc/argv, as described in glibc's sysdeps/sparc/sparc{32,64}/dl-machine.h (DL_STACK_END).

This patch does this, fixing the test.

Tested on sparc64-unknown-linux-gnu.

[llvmbot]

@llvm/pr-subscribers-compiler-rt-sanitizer

Author: Rainer Orth (rorth)

Changes

When ASan testing is enabled on SPARC as per PR #107405, the

  AddressSanitizer-sparc-linux :: TestCases/Posix/print_cmdline.cpp

test FAILs. Either ASAN_OPTIONS=print_cmdline=true yielded binary garbage in the Command: output or just an empty string.

It turns out one needs to apply an offset to __libc_stack_end to get at the actual argc/argv, as described in glibc's sysdeps/sparc/sparc{32,64}/dl-machine.h (DL_STACK_END).

This patch does this, fixing the test.

Tested on sparc64-unknown-linux-gnu.

---

Full diff: https://github.com/llvm/llvm-project/pull/109109.diff

1 Files Affected:

• (modified) compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp (+5)

diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp b/compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp
index 6359f4348e3c48..2faba3353d13dc 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp
@@ -725,6 +725,11 @@ static void GetArgsAndEnv(char ***argv, char ***envp) {
 #    if !SANITIZER_GO
   if (&__libc_stack_end) {
     uptr *stack_end = (uptr *)__libc_stack_end;
+    // Linux/sparc64 needs an adjustment, cf. glibc
+    // sysdeps/sparc/sparc{32,64}/dl-machine.h (DL_STACK_END).
+#      if SANITIZER_LINUX && defined(__sparc__)
+    stack_end = &stack_end[16];
+#      endif
     // 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