e018cbf720
There are two motivations. `-fno-pic -fstack-protector -mstack-protector-guard=global` created `__stack_chk_guard` is referenced directly on all ELF OSes except FreeBSD. This patch allows referencing the symbol indirectly with -fno-direct-access-external-data. Some Linux kernel folks want `-fno-pic -fstack-protector -mstack-protector-guard-reg=gs -mstack-protector-guard-symbol=__stack_chk_guard` created `__stack_chk_guard` to be referenced directly, avoiding R_X86_64_REX_GOTPCRELX (even if the relocation may be optimized out by the linker). https://github.com/llvm/llvm-project/issues/60116 Why they need this isn't so clear to me. --- Add module flag "direct-access-external-data" and set the dso_local property of the stack protector symbol. The module flag can benefit other LLVMCodeGen synthesized symbols that are not represented in LLVM IR. Nowadays, with `-fno-pic` being uncommon, ideally we should set "direct-access-external-data" when it is true. However, doing so would require ~90 clang/test tests to be updated, which are too much. As a compromise, we set "direct-access-external-data" only when it's different from the implied default value. Reviewed By: nickdesaulniers Differential Revision: https://reviews.llvm.org/D150841
42 lines
1.4 KiB
LLVM
42 lines
1.4 KiB
LLVM
; RUN: llc --frame-pointer=all -mtriple=aarch64-- < %s | FileCheck %s
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; PR25610: -fstack-protector places the canary in the wrong place on arm64 with
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; va_args
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%struct.__va_list = type { ptr, ptr, ptr, i32, i32 }
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; CHECK-LABEL: test
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; CHECK: ldr [[GUARD:x[0-9]+]]{{.*}}:lo12:__stack_chk_guard]
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; Make sure the canary is placed relative to the frame pointer, not
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; the stack pointer.
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; CHECK: stur [[GUARD]], [x29, #-8]
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define void @test(ptr %i, ...) #0 {
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entry:
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%buf = alloca [10 x i8], align 1
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%ap = alloca %struct.__va_list, align 8
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%tmp = alloca %struct.__va_list, align 8
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call void @llvm.lifetime.start(i64 10, ptr %buf)
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call void @llvm.lifetime.start(i64 32, ptr %ap)
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call void @llvm.va_start(ptr %ap)
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call void @llvm.memcpy.p0.p0.i64(ptr %tmp, ptr %ap, i64 32, i32 8, i1 false)
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call void @baz(ptr %i, ptr nonnull %tmp)
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call void @bar(ptr %buf)
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call void @llvm.va_end(ptr %ap)
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call void @llvm.lifetime.end(i64 32, ptr %ap)
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call void @llvm.lifetime.end(i64 10, ptr %buf)
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ret void
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}
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declare void @llvm.lifetime.start(i64, ptr nocapture)
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declare void @llvm.va_start(ptr)
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declare void @baz(ptr, ptr)
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declare void @llvm.memcpy.p0.p0.i64(ptr nocapture, ptr nocapture readonly, i64, i32, i1)
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declare void @bar(ptr)
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declare void @llvm.va_end(ptr)
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declare void @llvm.lifetime.end(i64, ptr nocapture)
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attributes #0 = { noinline nounwind optnone ssp }
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!llvm.module.flags = !{!0}
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!0 = !{i32 7, !"direct-access-external-data", i32 1}
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