[AArch64] Bugfix when using execute-only and memtag sanitizer together #133084
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Support for execute-only code generation (llvm#125687) introduced a bug in the case where the memtag sanitizer is used in a module containing a mix of execute-only and non-execute-only functions. The bug is caused by using `return` instead of `break` to short-circuit a loop, which meant that the rest of the function dealing with memtag sanitizer logic wasn't run.
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@llvm/pr-subscribers-backend-aarch64 @llvm/pr-subscribers-mc Author: Csanád Hajdú (Il-Capitano) ChangesSupport for execute-only code generation (#125687) introduced a bug in the case where the memtag sanitizer is used in a module containing a mix of execute-only and non-execute-only functions. The bug is caused by using Full diff: https://github.com/llvm/llvm-project/pull/133084.diff 2 Files Affected:
diff --git a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFStreamer.cpp b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFStreamer.cpp
index 98bd102d8f4c1..b12a12436db81 100644
--- a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFStreamer.cpp
+++ b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFStreamer.cpp
@@ -511,11 +511,17 @@ void AArch64TargetELFStreamer::finish() {
})) {
auto *Text =
static_cast<MCSectionELF *>(Ctx.getObjectFileInfo()->getTextSection());
- for (auto &F : *Text)
- if (auto *DF = dyn_cast<MCDataFragment>(&F))
- if (!DF->getContents().empty())
- return;
- Text->setFlags(Text->getFlags() | ELF::SHF_AARCH64_PURECODE);
+ bool Empty = true;
+ for (auto &F : *Text) {
+ if (auto *DF = dyn_cast<MCDataFragment>(&F)) {
+ if (!DF->getContents().empty()) {
+ Empty = false;
+ break;
+ }
+ }
+ }
+ if (Empty)
+ Text->setFlags(Text->getFlags() | ELF::SHF_AARCH64_PURECODE);
}
MCSectionELF *MemtagSec = nullptr;
diff --git a/llvm/test/MC/AArch64/execute-only-memtag.ll b/llvm/test/MC/AArch64/execute-only-memtag.ll
new file mode 100644
index 0000000000000..02daf3179101f
--- /dev/null
+++ b/llvm/test/MC/AArch64/execute-only-memtag.ll
@@ -0,0 +1,18 @@
+; RUN: llc %s -mtriple=aarch64-linux-android31 -filetype=obj -o %t.o
+; RUN: llvm-readelf -r %t.o | FileCheck %s
+
+; CHECK: Relocation section '.rela.memtag.globals.static' at offset {{.*}} contains 1 entries:
+; CHECK-NEXT: Type {{.*}} Symbol's Name
+; CHECK-NEXT: R_AARCH64_NONE {{.*}} global
+
+@global = global i32 1, sanitize_memtag
+
+define void @foo() {
+ ret void
+}
+
+define void @bar() #0 {
+ ret void
+}
+
+attributes #0 = { "target-features"="+execute-only" }
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Comment on lines
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| bool Empty = true; | ||
| for (auto &F : *Text) { | ||
| if (auto *DF = dyn_cast<MCDataFragment>(&F)) { | ||
| if (!DF->getContents().empty()) { | ||
| Empty = false; | ||
| break; | ||
| } | ||
| } | ||
| } |
There was a problem hiding this comment.
Can you use something like all_of(*Text, [](***) {return DF->getContents().empty();} here?
There was a problem hiding this comment.
I wanted to do that too, but I get the following error:
error: no matching function for call to '__iterator_category'
note: candidate template ignored: substitution failure [with _Iter = llvm::MCSection::iterator]: no type named 'iterator_category' in 'std::iterator_traits<llvm::MCSection::iterator>'
To me it looks like MCSection::iterator is not a proper iterator according to the standard library, so we can't use std::all_of (which llvm::all_of uses).
There was a problem hiding this comment.
Ok. Thanks for checking.
paulwalker-arm
approved these changes
Mar 31, 2025
Comment on lines
+514
to
+522
| bool Empty = true; | ||
| for (auto &F : *Text) { | ||
| if (auto *DF = dyn_cast<MCDataFragment>(&F)) { | ||
| if (!DF->getContents().empty()) { | ||
| Empty = false; | ||
| break; | ||
| } | ||
| } | ||
| } |
There was a problem hiding this comment.
Ok. Thanks for checking.
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Support for execute-only code generation (#125687) introduced a bug in the case where the memtag sanitizer is used in a module containing a mix of execute-only and non-execute-only functions.
The bug is caused by using
returninstead ofbreakto short-circuit a loop, which meant that the rest of the function dealing with memtag sanitizer logic wasn't run.