[gcc r11-8230] sanitizer: Fix asan against glibc 2.34 [PR100114]

[Jakub Jelinek <jakub@gcc.gnu.org>]

https://gcc.gnu.org/g:d9f462fb372fb02da032cefd6b091d7582c425ae

commit r11-8230-gd9f462fb372fb02da032cefd6b091d7582c425ae
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Sat Apr 17 11:27:14 2021 +0200

    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.

Diff:
---
 libsanitizer/sanitizer_common/sanitizer_posix_libcdep.cpp | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/libsanitizer/sanitizer_common/sanitizer_posix_libcdep.cpp b/libsanitizer/sanitizer_common/sanitizer_posix_libcdep.cpp
index d29438cf9db..7ff48c35851 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);
 }