[compiler-rt] [msan] Reland: Increase k num stack origin descrs (limited to non-PowerPC) (PR #93117)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

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

Author: Thurston Dang (thurstond)

<details>
<summary>Changes</summary>

The original pull request (https://github.com/llvm/llvm-project/pull/92838) was reverted due to a PowerPC buildbot breakage (https://github.com/llvm/llvm-project/commit/df626dd11c360c58eddae813ce6a0524d0a53696).
This reland limits the scope of the change to non-PowerPC platforms. I am unaware of any PowerPC use cases that would benefit from a larger kNumStackOriginDescrs constant.

Original CL description: This increases the constant size of kNumStackOriginDescrs to 4M (64GB of BSS across two arrays), which ought to be enough for anybody.

This is the easier alternative suggested by eugenis@ in https://github.com/llvm/llvm-project/pull/92826.



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Full diff: https://github.com/llvm/llvm-project/pull/93117.diff


1 Files Affected:

- (modified) compiler-rt/lib/msan/msan.cpp (+11-1) 


``````````diff
diff --git a/compiler-rt/lib/msan/msan.cpp b/compiler-rt/lib/msan/msan.cpp
index a2fc27de1901b..9375e27d4f4d2 100644
--- a/compiler-rt/lib/msan/msan.cpp
+++ b/compiler-rt/lib/msan/msan.cpp
@@ -100,7 +100,17 @@ int msan_report_count = 0;
 
 // Array of stack origins.
 // FIXME: make it resizable.
-static const uptr kNumStackOriginDescrs = 1024 * 1024;
+// Although BSS memory doesn't cost anything until used, it is limited to 2GB
+// in some configurations (e.g., "relocation R_X86_64_PC32 out of range:
+// ... is not in [-2147483648, 2147483647]; references section '.bss'").
+// We use kNumStackOriginDescrs * (sizeof(char*) + sizeof(uptr)) == 64MB.
+#ifdef SANITIZER_PPC
+// soft_rss_limit test (release_origin.c) fails on PPC if kNumStackOriginDescrs
+// is too high
+static const uptr kNumStackOriginDescrs = 1 * 1024 * 1024;
+#else
+static const uptr kNumStackOriginDescrs = 4 * 1024 * 1024;
+#endif  // SANITIZER_PPC
 static const char *StackOriginDescr[kNumStackOriginDescrs];
 static uptr StackOriginPC[kNumStackOriginDescrs];
 static atomic_uint32_t NumStackOriginDescrs;

``````````

</details>


https://github.com/llvm/llvm-project/pull/93117