sanitizer: Fix asan against glibc 2.34 [PR100114]

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.

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

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

1 files changed, 8 insertions, 5 deletions

diff --git a/libsanitizer/sanitizer_common/sanitizer_posix_libcdep.cpp b/libsanitizer/sanitizer_common/sanitizer_posix_libcdep.cpp
index d29438c..7ff48c3 100644
--- a/libsanitizer/sanitizer_common/sanitizer_posix_libcdep.cpp
+++ b/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);
 }