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[IR] Make stack protector symbol dso_local according to -f[no-]direct-access-external-data

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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
This commit is contained in:
Fangrui Song
2023-05-23 09:49:57 -07:00
parent 71400505ca
commit e018cbf720
20 changed files with 108 additions and 16 deletions
Download Patch File Download Diff File Expand all files Collapse all files

6
clang/lib/CodeGen/CodeGenModule.cpp
View File

@@ -908,6 +908,12 @@ void CodeGenModule::Release() {
if (CodeGenOpts.NoPLT)
getModule().setRtLibUseGOT();
if (getTriple().isOSBinFormatELF() &&
CodeGenOpts.DirectAccessExternalData !=
getModule().getDirectAccessExternalData()) {
getModule().setDirectAccessExternalData(
CodeGenOpts.DirectAccessExternalData);
}
if (CodeGenOpts.UnwindTables)
getModule().setUwtable(llvm::UWTableKind(CodeGenOpts.UnwindTables));

8
clang/test/CodeGen/dso-local-executable.c
View File

@@ -36,6 +36,8 @@
// STATIC-DAG: define dso_local ptr @zed()
// STATIC-DAG: declare dso_local void @import_func()
// STATIC-NOT: !"direct-access-external-data"
/// If -fno-direct-access-external-data is set, drop dso_local from global variable
/// declarations.
// RUN: %clang_cc1 -triple x86_64 -emit-llvm %s -mrelocation-model static -fno-direct-access-external-data -o - | FileCheck --check-prefix=STATIC-INDIRECT %s
@@ -49,6 +51,8 @@
// STATIC-INDIRECT-DAG: define dso_local ptr @zed()
// STATIC-INDIRECT-DAG: declare void @foo()
// STATIC-INDIRECT: ![[#]] = !{i32 7, !"direct-access-external-data", i32 0}
// RUN: %clang_cc1 -triple x86_64 -emit-llvm -pic-level 1 -pic-is-pie %s -o - | FileCheck --check-prefix=PIE %s
// PIE: @baz = dso_local global i32 42
// PIE-NEXT: @import_var = external global i32
@@ -60,6 +64,8 @@
// PIE-DAG: define dso_local ptr @zed()
// PIE-DAG: declare void @import_func()
// PIE-NOT: !"direct-access-external-data"
// RUN: %clang_cc1 -triple x86_64 -emit-llvm -pic-level 1 -pic-is-pie -fdirect-access-external-data %s -o - | FileCheck --check-prefix=PIE-DIRECT %s
// PIE-DIRECT: @baz = dso_local global i32 42
// PIE-DIRECT-NEXT: @import_var = external dso_local global i32
@@ -71,6 +77,8 @@
// PIE-DIRECT-DAG: define dso_local ptr @zed()
// PIE-DIRECT-DAG: declare void @import_func()
// PIE-DIRECT: ![[#]] = !{i32 7, !"direct-access-external-data", i32 1}
// RUN: %clang_cc1 -triple x86_64 -emit-llvm -mrelocation-model static -fno-plt %s -o - | FileCheck --check-prefix=NOPLT %s
// NOPLT: @baz = dso_local global i32 42
// NOPLT-NEXT: @import_var = external dso_local global i32

5
llvm/include/llvm/IR/Module.h
View File

@@ -945,6 +945,11 @@ public:
/// Set that PLT should be avoid for RTLib calls.
void setRtLibUseGOT();
/// Get/set whether referencing global variables can use direct access
/// relocations on ELF targets.
bool getDirectAccessExternalData() const;
void setDirectAccessExternalData(bool Value);
/// Get/set whether synthesized functions should get the uwtable attribute.
UWTableKind getUwtable() const;
void setUwtable(UWTableKind Kind);

2
llvm/lib/CodeGen/TargetLoweringBase.cpp
View File

@@ -1977,7 +1977,7 @@ void TargetLoweringBase::insertSSPDeclarations(Module &M) const {
"__stack_chk_guard");
// FreeBSD has "__stack_chk_guard" defined externally on libc.so
if (TM.getRelocationModel() == Reloc::Static &&
if (M.getDirectAccessExternalData() &&
!TM.getTargetTriple().isWindowsGNUEnvironment() &&
!TM.getTargetTriple().isOSFreeBSD())
GV->setDSOLocal(true);

12
llvm/lib/IR/Module.cpp
View File

@@ -672,6 +672,18 @@ void Module::setRtLibUseGOT() {
addModuleFlag(ModFlagBehavior::Max, "RtLibUseGOT", 1);
}
bool Module::getDirectAccessExternalData() const {
auto *Val = cast_or_null<ConstantAsMetadata>(
getModuleFlag("direct-access-external-data"));
if (Val)
return cast<ConstantInt>(Val->getValue())->getZExtValue() > 0;
return getPICLevel() == PICLevel::NotPIC;
}
void Module::setDirectAccessExternalData(bool Value) {
addModuleFlag(ModFlagBehavior::Max, "direct-access-external-data", Value);
}
UWTableKind Module::getUwtable() const {
if (auto *Val = cast_or_null<ConstantAsMetadata>(getModuleFlag("uwtable")))
return UWTableKind(cast<ConstantInt>(Val->getValue())->getZExtValue());

1
llvm/lib/Target/X86/X86ISelLowering.cpp
View File

@@ -3074,6 +3074,7 @@ Value *X86TargetLowering::getIRStackGuard(IRBuilderBase &IRB) const {
GV = new GlobalVariable(*M, Ty, false, GlobalValue::ExternalLinkage,
nullptr, GuardSymb, nullptr,
GlobalValue::NotThreadLocal, AddressSpace);
GV->setDSOLocal(M->getDirectAccessExternalData());
}
return GV;
}

3
llvm/test/CodeGen/AArch64/arm64_32.ll
View File

@@ -759,3 +759,6 @@ define void @test_bzero(i64 %in) {
}
declare void @llvm.memset.p0.i32(ptr nocapture writeonly, i8, i32, i1)
!llvm.module.flags = !{!0}
!0 = !{i32 7, !"PIC Level", i32 2}

3
llvm/test/CodeGen/AArch64/stack-guard-sve.ll
View File

@@ -337,3 +337,6 @@ entry:
attributes #0 = { ssp "frame-pointer"="non-leaf" }
attributes #1 = { sspstrong "frame-pointer"="non-leaf" }
!llvm.module.flags = !{!0}
!0 = !{i32 7, !"direct-access-external-data", i32 1}

3
llvm/test/CodeGen/AArch64/stack-guard-vaarg.ll
View File

@@ -36,3 +36,6 @@ declare void @llvm.va_end(ptr)
declare void @llvm.lifetime.end(i64, ptr nocapture)
attributes #0 = { noinline nounwind optnone ssp }
!llvm.module.flags = !{!0}
!0 = !{i32 7, !"direct-access-external-data", i32 1}

27
llvm/test/CodeGen/AArch64/stack_guard_remat.ll
View File

@@ -1,14 +1,16 @@
; RUN: llc < %s -mtriple=arm64-apple-ios -relocation-model=pic -no-integrated-as | FileCheck %s -check-prefix=DARWIN
; RUN: llc < %s -mtriple=arm64-apple-ios -relocation-model=static -no-integrated-as | FileCheck %s -check-prefix=DARWIN
; RUN: llc < %s -mtriple=aarch64-linux-gnu -relocation-model=pic -no-integrated-as | FileCheck %s -check-prefix=PIC-LINUX
; RUN: llc < %s -mtriple=aarch64-linux-gnu -relocation-model=static -code-model=large -no-integrated-as | FileCheck %s -check-prefix=STATIC-LARGE
; RUN: llc < %s -mtriple=aarch64-linux-gnu -relocation-model=static -code-model=small -no-integrated-as | FileCheck %s -check-prefix=STATIC-SMALL
; RUN: rm -rf %t && split-file %s %t && cd %t
; RUN: cat a.ll pic.ll > b.ll
; RUN: llc < b.ll -mtriple=arm64-apple-ios -relocation-model=pic -no-integrated-as | FileCheck %s -check-prefix=DARWIN
; RUN: llc < b.ll -mtriple=arm64-apple-ios -relocation-model=static -no-integrated-as | FileCheck %s -check-prefix=DARWIN
; RUN: llc < b.ll -mtriple=aarch64-linux-gnu -relocation-model=pic -no-integrated-as | FileCheck %s -check-prefix=PIC-LINUX
; RUN: llc < a.ll -mtriple=aarch64-linux-gnu -relocation-model=static -code-model=large -no-integrated-as | FileCheck %s -check-prefix=STATIC-LARGE
; RUN: llc < a.ll -mtriple=aarch64-linux-gnu -relocation-model=static -code-model=small -no-integrated-as | FileCheck %s -check-prefix=STATIC-SMALL
; RUN: llc < %s -global-isel -global-isel-abort=2 -pass-remarks-missed=gisel* -mtriple=arm64-apple-ios -relocation-model=pic -no-integrated-as 2>&1 | FileCheck %s -check-prefixes=DARWIN,FALLBACK
; RUN: llc < %s -global-isel -global-isel-abort=2 -pass-remarks-missed=gisel* -mtriple=arm64-apple-ios -relocation-model=static -no-integrated-as 2>&1 | FileCheck %s -check-prefixes=DARWIN,FALLBACK
; RUN: llc < %s -global-isel -global-isel-abort=2 -pass-remarks-missed=gisel* -mtriple=aarch64-linux-gnu -relocation-model=pic -no-integrated-as 2>&1 | FileCheck %s -check-prefixes=PIC-LINUX,FALLBACK
; RUN: llc < %s -global-isel -global-isel-abort=2 -pass-remarks-missed=gisel* -mtriple=aarch64-linux-gnu -relocation-model=static -code-model=large -no-integrated-as 2>&1 | FileCheck %s -check-prefixes=STATIC-LARGE,FALLBACK
; RUN: llc < %s -global-isel -global-isel-abort=2 -pass-remarks-missed=gisel* -mtriple=aarch64-linux-gnu -relocation-model=static -code-model=small -no-integrated-as 2>&1 | FileCheck %s -check-prefixes=STATIC-SMALL,FALLBACK
; RUN: llc < b.ll -global-isel -global-isel-abort=2 -pass-remarks-missed=gisel* -mtriple=arm64-apple-ios -relocation-model=pic -no-integrated-as 2>&1 | FileCheck %s -check-prefixes=DARWIN,FALLBACK
; RUN: llc < b.ll -global-isel -global-isel-abort=2 -pass-remarks-missed=gisel* -mtriple=arm64-apple-ios -relocation-model=static -no-integrated-as 2>&1 | FileCheck %s -check-prefixes=DARWIN,FALLBACK
; RUN: llc < b.ll -global-isel -global-isel-abort=2 -pass-remarks-missed=gisel* -mtriple=aarch64-linux-gnu -relocation-model=pic -no-integrated-as 2>&1 | FileCheck %s -check-prefixes=PIC-LINUX,FALLBACK
; RUN: llc < a.ll -global-isel -global-isel-abort=2 -pass-remarks-missed=gisel* -mtriple=aarch64-linux-gnu -relocation-model=static -code-model=large -no-integrated-as 2>&1 | FileCheck %s -check-prefixes=STATIC-LARGE,FALLBACK
; RUN: llc < a.ll -global-isel -global-isel-abort=2 -pass-remarks-missed=gisel* -mtriple=aarch64-linux-gnu -relocation-model=static -code-model=small -no-integrated-as 2>&1 | FileCheck %s -check-prefixes=STATIC-SMALL,FALLBACK
; DARWIN: foo2
; DARWIN: adrp [[R0:x[0-9]+]], ___stack_chk_guard@GOTPAGE
@@ -33,6 +35,7 @@
; FALLBACK-NOT: remark:{{.*}}llvm.lifetime.end
; FALLBACK-NOT: remark:{{.*}}llvm.lifetime.start
;--- a.ll
define i32 @test_stack_guard_remat() #0 {
entry:
%a1 = alloca [256 x i32], align 4
@@ -52,3 +55,7 @@ declare void @foo3(ptr)
declare void @llvm.lifetime.end.p0(i64, ptr nocapture)
attributes #0 = { nounwind sspstrong "less-precise-fpmad"="false" "frame-pointer"="all" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
;--- pic.ll
!llvm.module.flags = !{!0}
!0 = !{i32 8, !"PIC Level", i32 2}

3
llvm/test/CodeGen/ARM/expand-pseudos.ll
View File

@@ -28,3 +28,6 @@ define void @_ZN2v88internal4wasm16LiftoffAssembler13emit_i32_addiENS0_8Register
}
attributes #0 = { ssp }
!llvm.module.flags = !{!0}
!0 = !{i32 7, !"PIC Level", i32 2}

3
llvm/test/CodeGen/ARM/stack-guard-rwpi.ll
View File

@@ -26,3 +26,6 @@ entry:
}
declare dso_local i32 @baz(ptr)
!llvm.module.flags = !{!0}
!0 = !{i32 7, !"PIC Level", i32 2}

3
llvm/test/CodeGen/ARM/stack_guard_remat.ll
View File

@@ -66,3 +66,6 @@ declare void @foo3(ptr)
declare void @llvm.lifetime.end.p0(i64, ptr nocapture)
attributes #0 = { nounwind ssp "less-precise-fpmad"="false" "frame-pointer"="all" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
!llvm.module.flags = !{!0}
!0 = !{i32 7, !"PIC Level", i32 2}

3
llvm/test/CodeGen/Inputs/stack-guard-reassign.ll
View File

@@ -19,3 +19,6 @@ declare i8* @strcpy(i8*, i8*)
declare i32 @puts(i8*)
attributes #0 = { noinline nounwind optnone ssp }
!llvm.module.flags = !{!0}
!0 = !{i32 7, !"direct-access-external-data", i32 1}

3
llvm/test/CodeGen/PowerPC/stack-guard-oob.ll
View File

@@ -419,3 +419,6 @@ define i32 @multi_dimensional_array() #0 {
}
attributes #0 = { sspstrong }
!llvm.module.flags = !{!0}
!0 = !{i32 7, !"direct-access-external-data", i32 1}

3
llvm/test/CodeGen/Thumb/stack_guard_remat.ll
View File

@@ -57,3 +57,6 @@ declare void @foo3(ptr)
declare void @llvm.lifetime.end.p0(i64, ptr nocapture)
attributes #0 = { nounwind ssp "less-precise-fpmad"="false" "frame-pointer"="all" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
!llvm.module.flags = !{!0}
!0 = !{i32 7, !"PIC Level", i32 2}

3
llvm/test/CodeGen/Thumb2/stack_guard_remat.ll
View File

@@ -39,3 +39,6 @@ declare void @foo3(ptr)
declare void @llvm.lifetime.end.p0(i64, ptr nocapture)
attributes #0 = { nounwind ssp "less-precise-fpmad"="false" "frame-pointer"="all" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
!llvm.module.flags = !{!0}
!0 = !{i32 7, !"PIC Level", i32 2}

3
llvm/test/CodeGen/X86/2009-04-14-IllegalRegs.ll
View File

@@ -81,3 +81,6 @@ return: ; preds = %entry
}
declare i32 @f(ptr byval(%struct.X) align 4, ptr byval(%struct.X) align 4) nounwind ssp
!llvm.module.flags = !{!0}
!0 = !{i32 7, !"PIC Level", i32 2}

3
llvm/test/CodeGen/X86/2010-09-17-SideEffectsInChain.ll
View File

@@ -49,3 +49,6 @@ entry:
store i8 %e, ptr %c, align 8
ret i32 0
}
!llvm.module.flags = !{!0}
!0 = !{i32 7, !"direct-access-external-data", i32 1}

27
llvm/test/CodeGen/X86/stack-protector-3.ll
View File

@@ -7,7 +7,8 @@
; RUN: cat %t/main.ll %t/f.ll > %t/f2.ll
; RUN: cat %t/main.ll %t/g.ll > %t/g2.ll
; RUN: cat %t/main.ll %t/h.ll > %t/h2.ll
; RUN: cat %t/existedGV.ll %t/main.ll %t/h.ll > %t/i2.ll
; RUN: cat %t/existedGV.ll %t/main.ll %t/h.ll > %t/h3.ll
; RUN: cat %t/main.ll %t/i.ll > %t/i2.ll
; RUN: llc -mtriple=x86_64-pc-linux-gnu -o - < %t/a2.ll | FileCheck --check-prefix=CHECK-TLS-FS-40 %s
; RUN: llc -mtriple=x86_64-pc-linux-gnu -o - < %t/b2.ll | FileCheck --check-prefix=CHECK-TLS-FS-40 %s
; RUN: llc -mtriple=x86_64-pc-linux-gnu -o - < %t/c2.ll | FileCheck --check-prefix=CHECK-GLOBAL %s
@@ -16,7 +17,8 @@
; RUN: llc -mtriple=x86_64-pc-linux-gnu -o - < %t/f2.ll | FileCheck --check-prefix=CHECK-OFFSET %s
; RUN: llc -mtriple=x86_64-pc-linux-gnu -o - < %t/g2.ll | FileCheck --check-prefix=CHECK-NEGATIVE-OFFSET %s
; RUN: llc -mtriple=x86_64-pc-linux-gnu -o - < %t/h2.ll | FileCheck --check-prefix=CHECK-SYM %s
; RUN: llc -mtriple=x86_64-pc-linux-gnu -o - < %t/i2.ll | FileCheck --check-prefix=CHECK-SYMGV %s
; RUN: llc -mtriple=x86_64-pc-linux-gnu -o - < %t/h3.ll | FileCheck --check-prefix=CHECK-SYMGV %s
; RUN: llc -mtriple=x86_64-pc-linux-gnu -o - < %t/i2.ll | FileCheck --check-prefix=CHECK-SYM2 %s
; CHECK-TLS-FS-40: movq %fs:40, %rax
; CHECK-TLS-FS-40: movq %fs:40, %rax
@@ -67,7 +69,7 @@
; CHECK-SYM-NEXT: jne .LBB0_2
; CHECK-SYM: .LBB0_2:
; CHECK-SYM-NEXT: .cfi_def_cfa_offset 32
; CHECK-SYM-NEXT: callq __stack_chk_fai
; CHECK-SYM-NEXT: callq __stack_chk_fail
; CHECK-SYMGV: movq __woof(%rip), %rax
; CHECK-SYMGV-NEXT: movq %rax, 16(%rsp)
@@ -77,6 +79,15 @@
; CHECK-SYMGV-NEXT: .cfi_def_cfa_offset 32
; CHECK-SYMGV-NEXT: callq __stack_chk_fail
; CHECK-SYM2: movq %fs:__woof(%rip), %rax
; CHECK-SYM2-NEXT: movq %rax, 16(%rsp)
; CHECK-SYM2: movq %fs:__woof(%rip), %rax
; CHECK-SYM2-NEXT: cmpq 16(%rsp), %rax
; CHECK-SYM2-NEXT: jne .LBB0_2
; CHECK-SYM2: .LBB0_2:
; CHECK-SYM2-NEXT: .cfi_def_cfa_offset 32
; CHECK-SYM2-NEXT: callq __stack_chk_fai
; ModuleID = 't.c'
;--- existedGV.ll
@@ -116,7 +127,8 @@ attributes #2 = { nounwind }
!llvm.module.flags = !{!1}
!1 = !{i32 2, !"stack-protector-guard", !"tls"}
;--- c.ll
!llvm.module.flags = !{!1}
!llvm.module.flags = !{!0,!1}
!0 = !{i32 7, !"direct-access-external-data", i32 1}
!1 = !{i32 2, !"stack-protector-guard", !"global"}
;--- d.ll
!llvm.module.flags = !{!1}
@@ -131,5 +143,10 @@ attributes #2 = { nounwind }
!llvm.module.flags = !{!1}
!1 = !{i32 2, !"stack-protector-guard-offset", i32 -20}
;--- h.ll
!llvm.module.flags = !{!1}
!llvm.module.flags = !{!0,!1}
!0 = !{i32 7, !"direct-access-external-data", i32 0}
!1 = !{i32 2, !"stack-protector-guard-symbol", !"__woof"}
;--- i.ll
!llvm.module.flags = !{!0,!1}
!0 = !{i32 7, !"direct-access-external-data", i32 1}
!1 = !{i32 2, !"stack-protector-guard-symbol", !"__woof"}