[asan] Intercept __makecontext_v2 on Solaris/SPARC (llvm#81588)

As detailed in [GCC PR
sanitizer/113785](https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113785),
the GCC test `c-c++-common/asan/swapcontext-test-1.c` `FAIL`s on
Solaris/sparc.

This is due to the fact that Solaris 10/SPARC changed the semantics of
`makecontext` so `ucontext_t.uc_stack.ss_sp` refers to the stack base
address. To maintain binary compatiblity, the external name was changed
to `__makecontext_v2`, keeping the old version.

To match this, `__makecontext_v2` needs to be intercepted instead of
`makecontext`.

Tested on GCC trunk on `sparc-sun-solaris2.11`, `i386-pc-solaris2.11`,
and `x86_64-pc-linux-gnu`.

Also tested on the same targets on LLVM `main`. However, this only
proves that Linux/x86_64 isn't broken, since all `makecontext` tests are
Linux-specific.

Author: rorth

compiler-rt/lib/asan/asan_interceptors.cpp

@@ -352,8 +352,16 @@ static void ClearShadowMemoryForContextStack(uptr stack, uptr ssize) {
   PoisonShadow(bottom, ssize, 0);
 }
 
+// Since Solaris 10/SPARC, ucp->uc_stack.ss_sp refers to the stack base address
+// as on other targets.  For binary compatibility, the new version uses a
+// different external name, so we intercept that.
+#    if SANITIZER_SOLARIS && defined(__sparc__)
+INTERCEPTOR(void, __makecontext_v2, struct ucontext_t *ucp, void (*func)(),
+            int argc, ...) {
+#    else
 INTERCEPTOR(void, makecontext, struct ucontext_t *ucp, void (*func)(), int argc,
             ...) {
+#    endif
   va_list ap;
   uptr args[64];
   // We don't know a better way to forward ... into REAL function. We can
@@ -373,7 +381,11 @@ INTERCEPTOR(void, makecontext, struct ucontext_t *ucp, void (*func)(), int argc,
       ENUMERATE_ARRAY_16(0), ENUMERATE_ARRAY_16(16), ENUMERATE_ARRAY_16(32), \
           ENUMERATE_ARRAY_16(48)
 
+#    if SANITIZER_SOLARIS && defined(__sparc__)
+  REAL(__makecontext_v2)
+#    else
   REAL(makecontext)
+#    endif
   ((struct ucontext_t *)ucp, func, argc, ENUMERATE_ARRAY_64());
 
 #    undef ENUMERATE_ARRAY_4
@@ -780,7 +792,12 @@ void InitializeAsanInterceptors() {
 
 #  if ASAN_INTERCEPT_SWAPCONTEXT
   ASAN_INTERCEPT_FUNC(swapcontext);
+  // See the makecontext interceptor above for an explanation.
+#    if SANITIZER_SOLARIS && defined(__sparc__)
+  ASAN_INTERCEPT_FUNC(__makecontext_v2);
+#    else
   ASAN_INTERCEPT_FUNC(makecontext);
+#    endif
 #  endif
 #  if ASAN_INTERCEPT__LONGJMP
   ASAN_INTERCEPT_FUNC(_longjmp);