[compiler-rt] Fixed Android 8.1 getauxval(AT_PAGESZ) crashes if called from .preinit_array. (#113427)

[funsafe-ptr]

No description provided.

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[funsafe-ptr]

@fmayer

[fmayer]

Please change status of PR from "Draft"

[fmayer]

Leave comment about the API level this was introduced by, and also add the fact that before that API level, the page size was always 4096

[fmayer]

This is missing that strerrorname_np was also introduced in Android 15 (reference is https://cs.android.com/android/platform/superproject/main/+/main:bionic/libc/libc.map.txt?q=strerrorname_np%20f:bionic%2Flibc%2Flibc.map.txt)

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[fmayer]

nit: drop the blank line

[fmayer]

@DanAlbert does this LGTY from NDK perspective to use a weak symbol to runtime detect API level?

[llvmbot]

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

Author: None (funsafe-ptr)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/116121.diff

1 Files Affected:

• (modified) compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp (+13)

diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp b/compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp
index 04b095dca904ab..344b16be4a96e0 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp
@@ -82,6 +82,12 @@
 #    include <sys/personality.h>
 #  endif
 
+# if SANITIZER_ANDROID && __ANDROID_API__ < 35
+// The weak strerrorname_np definition allows to check for the API level at
+// runtime.
+extern "C" SANITIZER_WEAK_ATTRIBUTE const char* strerrorname_np(int);
+# endif
+
 #  if SANITIZER_LINUX && defined(__loongarch__)
 #    include <sys/sysmacros.h>
 #  endif
@@ -1237,6 +1243,13 @@ uptr GetPageSize() {
   CHECK_EQ(rv, 0);
   return (uptr)pz;
 #    elif SANITIZER_USE_GETAUXVAL
+#      if SANITIZER_ANDROID && __ANDROID_API__ < 35
+  // The 16 KB page size was introduced in Android 15, while earlier versions 
+  // of Android used a 4 KB page size.
+  if (!strerrorname_np)
+    return 4096;
+#      endif
+
   return getauxval(AT_PAGESZ);
 #    else
   return sysconf(_SC_PAGESIZE);  // EXEC_PAGESIZE may not be trustworthy.

[fmayer]

FYI: "This commit is not signed, but one or more authors requires that any commit attributed to them is signed."

[funsafe-ptr]

I tested it on Termux using Android 8.1. termux/termux-packages#22369 (comment)