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[AArch64] Emit PAC/BTI .note.gnu.property flags 

This patch make LLVM emit the processor specific program property types
defined in AArch64 ELF spec
https://developer.arm.com/docs/ihi0056/f/elf-for-the-arm-64-bit-architecture-aarch64-abi-2019q2-documentation

A file containing no functions gets both property flags.  Otherwise, a property
is set iff all the functions in the file have the corresponding attribute.

Patch by Daniel Kiss and Momchil Velikov.

Differential Revision: https://reviews.llvm.org/D71019
This commit is contained in:
Momchil Velikov 2019-12-13 17:37:22 +00:00
parent f99eedeb72
commit d53e61863d
10 changed files with 245 additions and 0 deletions
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60
llvm/lib/Target/AArch64/AArch64AsmPrinter.cpp
View File

@ -84,6 +84,7 @@ public:
return MCInstLowering.lowerOperand(MO, MCOp); return MCInstLowering.lowerOperand(MO, MCOp);
} }
void EmitStartOfAsmFile(Module &M) override;
void EmitJumpTableInfo() override; void EmitJumpTableInfo() override;
void emitJumpTableEntry(const MachineJumpTableInfo *MJTI, void emitJumpTableEntry(const MachineJumpTableInfo *MJTI,
const MachineBasicBlock *MBB, unsigned JTI); const MachineBasicBlock *MBB, unsigned JTI);
@ -181,6 +182,65 @@ private:
} // end anonymous namespace } // end anonymous namespace
void AArch64AsmPrinter::EmitStartOfAsmFile(Module &M) {
if (!TM.getTargetTriple().isOSBinFormatELF())
return;
// Assemble feature flags that may require creation of a note section.
unsigned Flags = ELF::GNU_PROPERTY_AARCH64_FEATURE_1_BTI |
ELF::GNU_PROPERTY_AARCH64_FEATURE_1_PAC;
if (any_of(M, [](const Function &F) {
return !F.isDeclaration() &&
!F.hasFnAttribute("branch-target-enforcement");
})) {
Flags &= ~ELF::GNU_PROPERTY_AARCH64_FEATURE_1_BTI;
}
if ((Flags & ELF::GNU_PROPERTY_AARCH64_FEATURE_1_BTI) == 0 &&
any_of(M, [](const Function &F) {
return F.hasFnAttribute("branch-target-enforcement");
})) {
errs() << "warning: some functions compiled with BTI and some compiled "
"without BTI\n"
<< "warning: not setting BTI in feature flags\n";
}
if (any_of(M, [](const Function &F) {
if (F.isDeclaration())
return false;
Attribute A = F.getFnAttribute("sign-return-address");
return !A.isStringAttribute() || A.getValueAsString() == "none";
})) {
Flags &= ~ELF::GNU_PROPERTY_AARCH64_FEATURE_1_PAC;
}
if (Flags == 0)
return;
// Emit a .note.gnu.property section with the flags.
MCSection *Cur = OutStreamer->getCurrentSectionOnly();
MCSection *Nt = MMI->getContext().getELFSection(
".note.gnu.property", ELF::SHT_NOTE, ELF::SHF_ALLOC);
OutStreamer->SwitchSection(Nt);
// Emit the note header.
EmitAlignment(Align(8));
OutStreamer->EmitIntValue(4, 4); // data size for "GNU\0"
OutStreamer->EmitIntValue(4 * 4, 4); // Elf_Prop size
OutStreamer->EmitIntValue(ELF::NT_GNU_PROPERTY_TYPE_0, 4);
OutStreamer->EmitBytes(StringRef("GNU", 4)); // note name
// Emit the PAC/BTI properties.
OutStreamer->EmitIntValue(ELF::GNU_PROPERTY_AARCH64_FEATURE_1_AND, 4);
OutStreamer->EmitIntValue(4, 4); // data size
OutStreamer->EmitIntValue(Flags, 4); // data
OutStreamer->EmitIntValue(0, 4); // pad
OutStreamer->endSection(Nt);
OutStreamer->SwitchSection(Cur);
}
void AArch64AsmPrinter::LowerPATCHABLE_FUNCTION_ENTER(const MachineInstr &MI) void AArch64AsmPrinter::LowerPATCHABLE_FUNCTION_ENTER(const MachineInstr &MI)
{ {
EmitSled(MI, SledKind::FUNCTION_ENTER); EmitSled(MI, SledKind::FUNCTION_ENTER);

14
llvm/test/CodeGen/AArch64/note-gnu-property-pac-bti-0.ll Normal file
View File

@ -0,0 +1,14 @@
; RUN: llc -mtriple=aarch64-linux %s -o - | \
; RUN: FileCheck %s --check-prefix=ASM
; RUN: llc -mtriple=aarch64-linux %s -filetype=obj -o - | \
; RUN: llvm-readelf --notes | FileCheck %s --check-prefix=OBJ
@x = common dso_local global i32 0, align 4
attributes #0 = { "branch-target-enforcement" }
; Both attributes present in a file with no functions.
; ASM: .word 3221225472
; ASM-NEXT: .word 4
; ASM-NEXT .word 3
; OBJ: Properties: aarch64 feature: BTI, PAC

18
llvm/test/CodeGen/AArch64/note-gnu-property-pac-bti-1.ll Normal file
View File

@ -0,0 +1,18 @@
; RUN: llc -mtriple=aarch64-linux %s -o - | \
; RUN: FileCheck %s --check-prefix=ASM
; RUN: llc -mtriple=aarch64-linux %s -filetype=obj -o - | \
; RUN: llvm-readelf --notes | FileCheck %s --check-prefix=OBJ
define dso_local i32 @f() #0 {
entry:
ret i32 0
}
attributes #0 = { "branch-target-enforcement" }
; BTI attribute present
; ASM: .word 3221225472
; ASM-NEXT: .word 4
; ASM-NEXT .word 1
; OBJ: Properties: aarch64 feature: BTI

18
llvm/test/CodeGen/AArch64/note-gnu-property-pac-bti-2.ll Normal file
View File

@ -0,0 +1,18 @@
; RUN: llc -mtriple=aarch64-linux %s -o - | \
; RUN: FileCheck %s --check-prefix=ASM
; RUN: llc -mtriple=aarch64-linux %s -filetype=obj -o - | \
; RUN: llvm-readelf --notes | FileCheck %s --check-prefix=OBJ
define dso_local i32 @f() #0 {
entry:
ret i32 0
}
attributes #0 = { "sign-return-address"="all" }
; PAC attribute present
; ASM: .word 3221225472
; ASM-NEXT: .word 4
; ASM-NEXT .word 2
; OBJ: Properties: aarch64 feature: PAC

18
llvm/test/CodeGen/AArch64/note-gnu-property-pac-bti-3.ll Normal file
View File

@ -0,0 +1,18 @@
; RUN: llc -mtriple=aarch64-linux %s -o - | \
; RUN: FileCheck %s --check-prefix=ASM
; RUN: llc -mtriple=aarch64-linux %s -filetype=obj -o - | \
; RUN: llvm-readelf --notes | FileCheck %s --check-prefix=OBJ
define dso_local i32 @f() #0 {
entry:
ret i32 0
}
attributes #0 = { "branch-target-enforcement" "sign-return-address"="non-leaf" }
; Both attribute present
; ASM: .word 3221225472
; ASM-NEXT: .word 4
; ASM-NEXT .word 3
; OBJ: Properties: aarch64 feature: BTI, PAC

25
llvm/test/CodeGen/AArch64/note-gnu-property-pac-bti-4.ll Normal file
View File

@ -0,0 +1,25 @@
; RUN: llc -mtriple=aarch64-linux %s -o - | \
; RUN: FileCheck %s --check-prefix=ASM
; RUN: llc -mtriple=aarch64-linux %s -filetype=obj -o - | \
; RUN: llvm-readelf --notes | FileCheck %s --check-prefix=OBJ
define dso_local i32 @f() #0 {
entry:
ret i32 0
}
define dso_local i32 @g() #1 {
entry:
ret i32 0
}
attributes #0 = { "branch-target-enforcement" "sign-return-address"="non-leaf" }
attributes #1 = { "branch-target-enforcement" }
; Only the common atttribute (BTI)
; ASM: .word 3221225472
; ASM-NEXT: .word 4
; ASM-NEXT .word 1
; OBJ: Properties: aarch64 feature: BTI

26
llvm/test/CodeGen/AArch64/note-gnu-property-pac-bti-5.ll Normal file
View File

@ -0,0 +1,26 @@
; RUN: llc -mtriple=aarch64-linux %s -o - 2>&1 | \
; RUN: FileCheck %s --check-prefix=ASM
; RUN: llc -mtriple=aarch64-linux %s -filetype=obj -o - | \
; RUN: llvm-readelf --notes | FileCheck %s --check-prefix=OBJ
define dso_local i32 @f() #0 {
entry:
ret i32 0
}
define dso_local i32 @g() #1 {
entry:
ret i32 0
}
attributes #0 = { "branch-target-enforcement" "sign-return-address"="non-leaf" }
attributes #1 = { "sign-return-address"="all" }
; Only the common atttribute (PAC)
; ASM: warning: not setting BTI in feature flags
; ASM: .word 3221225472
; ASM-NEXT: .word 4
; ASM-NEXT .word 2
; OBJ: Properties: aarch64 feature: PAC

22
llvm/test/CodeGen/AArch64/note-gnu-property-pac-bti-6.ll Normal file
View File

@ -0,0 +1,22 @@
; RUN: llc -mtriple=aarch64-linux %s -o - | \
; RUN: FileCheck %s --check-prefix=ASM
; RUN: llc -mtriple=aarch64-linux %s -filetype=obj -o - | \
; RUN: llvm-readelf -S | FileCheck %s --check-prefix=OBJ
define dso_local i32 @f() #0 {
entry:
ret i32 0
}
define dso_local i32 @g() #1 {
entry:
ret i32 0
}
attributes #0 = { "sign-return-address"="non-leaf" }
attributes #1 = { "sign-return-address"="none" }
; No common attribute, no note section
; ASM-NOT: .note.gnu.property
; OBJ-NOT: .note.gnu.property

23
llvm/test/CodeGen/AArch64/note-gnu-property-pac-bti-7.ll Normal file
View File

@ -0,0 +1,23 @@
; RUN: llc -mtriple=aarch64-linux %s -o - 2>&1 | \
; RUN: FileCheck %s --check-prefix=ASM
; RUN: llc -mtriple=aarch64-linux %s -filetype=obj -o - | \
; RUN: llvm-readelf -S | FileCheck %s --check-prefix=OBJ
define dso_local i32 @f() #0 {
entry:
ret i32 0
}
define dso_local i32 @g() #1 {
entry:
ret i32 0
}
attributes #0 = { "sign-return-address"="non-leaf" }
attributes #1 = { "branch-target-enforcement" }
; No common attribute, no note section
; ASM: warning: not setting BTI in feature flags
; ASM-NOT: .note.gnu.property
; OBJ-NOT: .note.gnu.property

21
llvm/test/CodeGen/AArch64/note-gnu-property-pac-bti-8.ll Normal file
View File

@ -0,0 +1,21 @@
; RUN: llc -mtriple=aarch64-linux %s -o - | \
; RUN: FileCheck %s --check-prefix=ASM
; RUN: llc -mtriple=aarch64-linux %s -filetype=obj -o - | \
; RUN: llvm-readelf --notes | FileCheck %s --check-prefix=OBJ
define dso_local i32 @f() #0 {
entry:
%r = tail call i32 @g()
ret i32 %r
}
declare dso_local i32 @g()
attributes #0 = { "branch-target-enforcement" }
; Declarations don't prevent setting BTI
; ASM: .word 3221225472
; ASM-NEXT: .word 4
; ASM-NEXT .word 1
; OBJ: Properties: aarch64 feature: BTI