[committed] sanitizer: Fix asan against glibc 2.34 [PR100114]

[Jakub Jelinek via Gcc-patches]

Hi!

As mentioned in the PR, SIGSTKSZ is no longer a compile time constant in
glibc 2.34 and later, so
static const uptr kAltStackSize = SIGSTKSZ * 4;
needs dynamic initialization, but is used by a function called indirectly
from .preinit_array and therefore before the variable is constructed.
This results in using 0 size instead and all asan instrumented programs
die with:
==91==ERROR: AddressSanitizer failed to allocate 0x0 (0) bytes of 
SetAlternateSignalStack (error code: 22)

Here is a cherry-pick from upstream to fix this.

Bootstrapped/regtested on {x86_64,i686,powerpc64le,s390x,aarch64,armv7hl}-linux,
both against glibc 2.33 and 2.34 snapshots and verified the testresults
are back to roughly the same in between those two, while previously
basically all asan tests failed.
Committed to trunk.

2021-04-17  Jakub Jelinek  <ja...@redhat.com>

        PR sanitizer/100114
        * sanitizer_common/sanitizer_posix_libcdep.cpp: Cherry-pick
        llvm-project revisions 82150606fb11d28813ae6da1101f5bda638165fe
        and b93629dd335ffee2fc4b9b619bf86c3f9e6b0023.

--- libsanitizer/sanitizer_common/sanitizer_posix_libcdep.cpp
+++ libsanitizer/sanitizer_common/sanitizer_posix_libcdep.cpp
@@ -165,7 +165,11 @@ bool SupportsColoredOutput(fd_t fd) {
 
 #if !SANITIZER_GO
 // TODO(glider): different tools may require different altstack size.
-static const uptr kAltStackSize = SIGSTKSZ * 4;  // SIGSTKSZ is not enough.
+static uptr GetAltStackSize() {
+  // SIGSTKSZ is not enough.
+  static const uptr kAltStackSize = SIGSTKSZ * 4;
+  return kAltStackSize;
+}
 
 void SetAlternateSignalStack() {
   stack_t altstack, oldstack;
@@ -176,10 +180,9 @@ void SetAlternateSignalStack() {
   // TODO(glider): the mapped stack should have the MAP_STACK flag in the
   // future. It is not required by man 2 sigaltstack now (they're using
   // malloc()).
-  void* base = MmapOrDie(kAltStackSize, __func__);
-  altstack.ss_sp = (char*) base;
+  altstack.ss_size = GetAltStackSize();
+  altstack.ss_sp = (char *)MmapOrDie(altstack.ss_size, __func__);
   altstack.ss_flags = 0;
-  altstack.ss_size = kAltStackSize;
   CHECK_EQ(0, sigaltstack(&altstack, nullptr));
 }
 
@@ -187,7 +190,7 @@ void UnsetAlternateSignalStack() {
   stack_t altstack, oldstack;
   altstack.ss_sp = nullptr;
   altstack.ss_flags = SS_DISABLE;
-  altstack.ss_size = kAltStackSize;  // Some sane value required on Darwin.
+  altstack.ss_size = GetAltStackSize();  // Some sane value required on Darwin.
   CHECK_EQ(0, sigaltstack(&altstack, &oldstack));
   UnmapOrDie(oldstack.ss_sp, oldstack.ss_size);
 }


        Jakub