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Disable memtag sanitization for global fnptrs going into .ctors #70186

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Merged
merged 1 commit into from
Nov 1, 2023
Merged

Disable memtag sanitization for global fnptrs going into .ctors #70186

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20 changes: 20 additions & 0 deletions clang/test/CodeGen/memtag-globals-asm.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -259,3 +259,23 @@ int f(int x) {
// CHECK-Q-DAG: ldr {{.*}}, [[[REG_O2]]]
function_int;
}

typedef void (*func_t)(void);
#define CONSTRUCTOR(section_name) \
__attribute__((used)) __attribute__((section(section_name)))

__attribute__((constructor(0))) void func_constructor() {}
CONSTRUCTOR(".init") func_t func_init = func_constructor;
CONSTRUCTOR(".fini") func_t func_fini = func_constructor;
CONSTRUCTOR(".ctors") func_t func_ctors = func_constructor;
CONSTRUCTOR(".dtors") func_t func_dtors = func_constructor;
CONSTRUCTOR(".init_array") func_t func_init_array = func_constructor;
CONSTRUCTOR(".fini_array") func_t func_fini_array = func_constructor;

// CHECK-NOT: .memtag func_constructor
// CHECK-NOT: .memtag func_init
// CHECK-NOT: .memtag func_fini
// CHECK-NOT: .memtag func_ctors
// CHECK-NOT: .memtag func_dtors
// CHECK-NOT: .memtag func_init_array
// CHECK-NOT: .memtag func_fini_array
12 changes: 12 additions & 0 deletions llvm/lib/Target/AArch64/AArch64GlobalsTagging.cpp
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Expand Up @@ -43,6 +43,18 @@ static bool shouldTagGlobal(GlobalVariable &G) {
return false;
}

// Don't instrument function pointers that are going into various init arrays
// via `__attribute__((section(<foo>)))`:
// https://github.com/llvm/llvm-project/issues/69939
if (G.hasSection() &&
(G.getSection() == ".init" || G.getSection() == ".fini" ||
G.getSection() == ".init_array" || G.getSection() == ".fini_array" ||
G.getSection() == ".ctors" || G.getSection() == ".dtors")) {
Meta.Memtag = false;
G.setSanitizerMetadata(Meta);
return false;
}

return true;
}

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