https://github.com/efriedma-quic updated https://github.com/llvm/llvm-project/pull/195379
>From e3614887f017e34090df190f5bc4772c700580d7 Mon Sep 17 00:00:00 2001 From: Eli Friedman <[email protected]> Date: Fri, 1 May 2026 15:11:02 -0700 Subject: [PATCH 1/2] [AArch64] Make width of stack protector guard value load configurable. Embedded targets can have unusual requirements for how they store the value of the stack protector. Allow changing the backend to emit a 4-byte load for the value of the stack protector, instead of an 8-byte load. (Or vice versa for an ilp32 target.) The current version of the patch has a limitation: it still allocates a pointer-sized stack slot for the guard. This could be fixed in the future, if it becomes relevant. --- clang/include/clang/Basic/CodeGenOptions.def | 3 ++ clang/include/clang/Options/Options.td | 4 ++ clang/lib/CodeGen/CodeGenModule.cpp | 3 ++ clang/lib/Driver/ToolChains/Clang.cpp | 19 ++++++++ clang/test/CodeGen/stack-protector-guard.c | 5 +++ llvm/include/llvm/IR/Module.h | 4 ++ llvm/lib/IR/Module.cpp | 12 +++++ llvm/lib/Target/AArch64/AArch64InstrInfo.cpp | 17 +++++-- .../test/CodeGen/AArch64/stack-guard-width.ll | 44 +++++++++++++++++++ 9 files changed, 108 insertions(+), 3 deletions(-) create mode 100644 llvm/test/CodeGen/AArch64/stack-guard-width.ll diff --git a/clang/include/clang/Basic/CodeGenOptions.def b/clang/include/clang/Basic/CodeGenOptions.def index 0cd8f35339cf7..6604bb9769ec7 100644 --- a/clang/include/clang/Basic/CodeGenOptions.def +++ b/clang/include/clang/Basic/CodeGenOptions.def @@ -428,6 +428,9 @@ ENUM_CODEGENOPT(ExtendVariableLiveness, ExtendVariableLivenessKind, 2, ExtendVar /// The default stack protector guard offset to use. VALUE_CODEGENOPT(StackProtectorGuardOffset, 32, INT_MAX, Benign) +/// The width to use for the stack protector guard value. +VALUE_CODEGENOPT(StackProtectorGuardValueWidth, 32, UINT_MAX, Benign) + /// Number of path components to strip when emitting checks. (0 == full /// filename) VALUE_CODEGENOPT(EmitCheckPathComponentsToStrip, 32, 0, Benign) diff --git a/clang/include/clang/Options/Options.td b/clang/include/clang/Options/Options.td index 96ecc8fbdeb83..2bea20f9ad064 100644 --- a/clang/include/clang/Options/Options.td +++ b/clang/include/clang/Options/Options.td @@ -6072,6 +6072,10 @@ def mstack_protector_guard_offset_EQ : Joined<["-"], "mstack-protector-guard-off Visibility<[ClangOption, CC1Option]>, HelpText<"Use the given offset for addressing the stack-protector guard">, MarshallingInfoInt<CodeGenOpts<"StackProtectorGuardOffset">, "INT_MAX", "int">; +def mstack_protector_guard_value_width_EQ : Joined<["-"], "mstack-protector-guard-value-width=">, Group<m_Group>, + Visibility<[ClangOption, CC1Option]>, + HelpText<"Use the given width for the value of the the stack-protector guard">, + MarshallingInfoInt<CodeGenOpts<"StackProtectorGuardValueWidth">, "UINT_MAX", "unsigned">; def mstack_protector_guard_symbol_EQ : Joined<["-"], "mstack-protector-guard-symbol=">, Group<m_Group>, Visibility<[ClangOption, CC1Option]>, HelpText<"Use the given symbol for addressing the stack-protector guard">, diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp index b5ff40c2bd175..953b8455b533b 100644 --- a/clang/lib/CodeGen/CodeGenModule.cpp +++ b/clang/lib/CodeGen/CodeGenModule.cpp @@ -1624,6 +1624,9 @@ void CodeGenModule::Release() { if (getCodeGenOpts().StackProtectorGuardOffset != INT_MAX) getModule().setStackProtectorGuardOffset( getCodeGenOpts().StackProtectorGuardOffset); + if (getCodeGenOpts().StackProtectorGuardValueWidth != UINT_MAX) + getModule().setStackProtectorGuardValueWidth( + getCodeGenOpts().StackProtectorGuardValueWidth); if (getCodeGenOpts().StackAlignment) getModule().setOverrideStackAlignment(getCodeGenOpts().StackAlignment); if (getCodeGenOpts().SkipRaxSetup) diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp index 267e674441599..28b98a1d66b1c 100644 --- a/clang/lib/Driver/ToolChains/Clang.cpp +++ b/clang/lib/Driver/ToolChains/Clang.cpp @@ -3634,6 +3634,25 @@ static void RenderSSPOptions(const Driver &D, const ToolChain &TC, } A->render(Args, CmdArgs); } + + if (Arg *A = + Args.getLastArg(options::OPT_mstack_protector_guard_value_width_EQ)) { + if (!EffectiveTriple.isAArch64()) + D.Diag(diag::err_drv_unsupported_opt_for_target) + << A->getAsString(Args) << TripleStr; + StringRef Value = A->getValue(); + unsigned Width; + if (Value.getAsInteger(10, Width)) { + D.Diag(diag::err_drv_invalid_value) << A->getOption().getName() << Value; + return; + } + if (Width != 4 && Width != 8) { + D.Diag(diag::err_drv_invalid_int_value) + << A->getOption().getName() << Value; + return; + } + A->render(Args, CmdArgs); + } } static void RenderSCPOptions(const ToolChain &TC, const ArgList &Args, diff --git a/clang/test/CodeGen/stack-protector-guard.c b/clang/test/CodeGen/stack-protector-guard.c index 7bffa2a1107a4..5438671483aff 100644 --- a/clang/test/CodeGen/stack-protector-guard.c +++ b/clang/test/CodeGen/stack-protector-guard.c @@ -27,6 +27,8 @@ // RUN: %clang_cc1 -mstack-protector-guard=sysreg -triple aarch64-linux-gnu \ // RUN: -mstack-protector-guard-offset=1024 -mstack-protector-guard-reg=far_el2 \ // RUN: -emit-llvm %s -o - | FileCheck %s --check-prefix=AARCH64 --check-prefix=AARCH64-FAR-EL2 +// RUN: %clang_cc1 -mstack-protector-guard-value-width=4 -triple aarch64-linux-gnu \ +// RUN: -emit-llvm %s -o - | FileCheck %s --check-prefix=AARCH64-WIDTH-4 // RUN: %clang_cc1 -mstack-protector-guard=tls -triple riscv64-unknown-elf \ // RUN: -mstack-protector-guard-offset=44 -mstack-protector-guard-reg=tp \ // RUN: -emit-llvm %s -o - | FileCheck %s --check-prefix=RISCV @@ -57,6 +59,9 @@ void bar(int x) { // AARCH64-FAR-EL2: [[ATTR2]] = !{i32 1, !"stack-protector-guard-reg", !"far_el2"} // AARCH64: [[ATTR3]] = !{i32 1, !"stack-protector-guard-offset", i32 1024} +// AARCH64-WIDTH-4: !llvm.module.flags = !{{{.*}}[[ATTR1:![0-9]+]]} +// AARCH64-WIDTH-4: [[ATTR1]] = !{i32 1, !"stack-protector-guard-value-width", i32 4} + // RISCV: !llvm.module.flags = !{{{.*}}[[ATTR1:![0-9]+]], [[ATTR2:![0-9]+]], [[ATTR3:![0-9]+]], [[ATTR4:![0-9]+]]} // RISCV: [[ATTR1]] = !{i32 1, !"stack-protector-guard", !"tls"} // RISCV: [[ATTR2]] = !{i32 1, !"stack-protector-guard-reg", !"tp"} diff --git a/llvm/include/llvm/IR/Module.h b/llvm/include/llvm/IR/Module.h index 7156a83c9f3cc..5bcbf31e6e014 100644 --- a/llvm/include/llvm/IR/Module.h +++ b/llvm/include/llvm/IR/Module.h @@ -1007,6 +1007,10 @@ class LLVM_ABI Module { int getStackProtectorGuardOffset() const; void setStackProtectorGuardOffset(int Offset); + /// Get/set the width in memory of the stack protector guard value. + std::optional<unsigned> getStackProtectorGuardValueWidth() const; + void setStackProtectorGuardValueWidth(unsigned Width); + /// Get/set the stack alignment overridden from the default. unsigned getOverrideStackAlignment() const; void setOverrideStackAlignment(unsigned Align); diff --git a/llvm/lib/IR/Module.cpp b/llvm/lib/IR/Module.cpp index 11dc68e0e4751..95d7e75d1ec0a 100644 --- a/llvm/lib/IR/Module.cpp +++ b/llvm/lib/IR/Module.cpp @@ -807,6 +807,18 @@ void Module::setStackProtectorGuardOffset(int Offset) { addModuleFlag(ModFlagBehavior::Error, "stack-protector-guard-offset", Offset); } +std::optional<unsigned> Module::getStackProtectorGuardValueWidth() const { + Metadata *MD = getModuleFlag("stack-protector-guard-value-width"); + if (auto *CI = mdconst::dyn_extract_or_null<ConstantInt>(MD)) + return CI->getSExtValue(); + return std::nullopt; +} + +void Module::setStackProtectorGuardValueWidth(unsigned Width) { + addModuleFlag(ModFlagBehavior::Error, "stack-protector-guard-value-width", + Width); +} + unsigned Module::getOverrideStackAlignment() const { Metadata *MD = getModuleFlag("override-stack-alignment"); if (auto *CI = mdconst::dyn_extract_or_null<ConstantInt>(MD)) diff --git a/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp b/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp index 9d805dad07c1c..26d3892888a4a 100644 --- a/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp +++ b/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp @@ -2548,10 +2548,14 @@ bool AArch64InstrInfo::expandPostRAPseudo(MachineInstr &MI) const { unsigned OpFlags = Subtarget.ClassifyGlobalReference(GV, TM); const unsigned char MO_NC = AArch64II::MO_NC; + unsigned GuardWidth = M.getStackProtectorGuardValueWidth().value_or( + Subtarget.isTargetILP32() ? 4 : 8); + if (GuardWidth != 4 && GuardWidth != 8) + report_fatal_error("Unsupported stack protector value width"); if ((OpFlags & AArch64II::MO_GOT) != 0) { BuildMI(MBB, MI, DL, get(AArch64::LOADgot), Reg) .addGlobalAddress(GV, 0, OpFlags); - if (Subtarget.isTargetILP32()) { + if (GuardWidth == 4) { unsigned Reg32 = TRI->getSubReg(Reg, AArch64::sub_32); BuildMI(MBB, MI, DL, get(AArch64::LDRWui)) .addDef(Reg32, RegState::Dead) @@ -2566,7 +2570,9 @@ bool AArch64InstrInfo::expandPostRAPseudo(MachineInstr &MI) const { .addMemOperand(*MI.memoperands_begin()); } } else if (TM.getCodeModel() == CodeModel::Large) { - assert(!Subtarget.isTargetILP32() && "how can large exist in ILP32?"); + if (GuardWidth == 4) + report_fatal_error("Large code model with 4-byte stack protector not yet " + "supported"); BuildMI(MBB, MI, DL, get(AArch64::MOVZXi), Reg) .addGlobalAddress(GV, 0, AArch64II::MO_G0 | MO_NC) .addImm(0); @@ -2587,13 +2593,18 @@ bool AArch64InstrInfo::expandPostRAPseudo(MachineInstr &MI) const { .addImm(0) .addMemOperand(*MI.memoperands_begin()); } else if (TM.getCodeModel() == CodeModel::Tiny) { + // FIXME: This is computing the stack protector value as a constant + // pc-relative offset, not loading it from memory. Which is maybe + // an interesting compromise in some environments, but it looks like it + // was done accidentally. And it probably shouldn't be tied to the + // code model. BuildMI(MBB, MI, DL, get(AArch64::ADR), Reg) .addGlobalAddress(GV, 0, OpFlags); } else { BuildMI(MBB, MI, DL, get(AArch64::ADRP), Reg) .addGlobalAddress(GV, 0, OpFlags | AArch64II::MO_PAGE); unsigned char LoFlags = OpFlags | AArch64II::MO_PAGEOFF | MO_NC; - if (Subtarget.isTargetILP32()) { + if (GuardWidth == 4) { unsigned Reg32 = TRI->getSubReg(Reg, AArch64::sub_32); BuildMI(MBB, MI, DL, get(AArch64::LDRWui)) .addDef(Reg32, RegState::Dead) diff --git a/llvm/test/CodeGen/AArch64/stack-guard-width.ll b/llvm/test/CodeGen/AArch64/stack-guard-width.ll new file mode 100644 index 0000000000000..b9d24e5d8856e --- /dev/null +++ b/llvm/test/CodeGen/AArch64/stack-guard-width.ll @@ -0,0 +1,44 @@ +; NOTE: Do not autogenerate +; The update tools can't understand this usage of split-file. (Maybe we should +; add llc flags to set the PIC metadata.) +; RUN: rm -rf %t && split-file %s %t && cd %t +; RUN: cat a.ll nopic.ll > b.ll +; RUN: cat a.ll pic.ll > c.ll +; RUN: llc < b.ll | FileCheck %s +; RUN: llc < c.ll -relocation-model=pic | FileCheck %s -check-prefix=PIC + +;--- a.ll +target triple = "aarch64-unknown-linux-gnu" + +define dso_local void @f(ptr noundef %g) #0 { +; CHECK: adrp x9, __stack_chk_guard +; CHECK: ldr w9, [x9, :lo12:__stack_chk_guard] +; CHECK: adrp x8, __stack_chk_guard +; CHECK: ldr w8, [x8, :lo12:__stack_chk_guard] + +; PIC: adrp x9, :got:__stack_chk_guard +; PIC: ldr x9, [x9, :got_lo12:__stack_chk_guard] +; PIC: ldr w9, [x9] +; PIC: adrp x8, :got:__stack_chk_guard +; PIC: ldr x8, [x8, :got_lo12:__stack_chk_guard] +; PIC: ldr w8, [x8] +entry: + %g.addr = alloca ptr, align 8 + %x = alloca [1000 x i8], align 1 + store ptr %g, ptr %g.addr, align 8 + %0 = load ptr, ptr %g.addr, align 8 + %arraydecay = getelementptr inbounds [1000 x i8], ptr %x, i64 0, i64 0 + call void %0(ptr noundef %arraydecay) + ret void +} + +attributes #0 = { ssp } + +;--- nopic.ll +!llvm.module.flags = !{!0} +!0 = !{i32 1, !"stack-protector-guard-value-width", i32 4} + +;--- pic.ll +!llvm.module.flags = !{!0, !1} +!0 = !{i32 1, !"stack-protector-guard-value-width", i32 4} +!1 = !{i32 8, !"PIC Level", i32 2} >From cf0f25fcbd194638f35cb2e785fbea9b8295032e Mon Sep 17 00:00:00 2001 From: Eli Friedman <[email protected]> Date: Wed, 13 May 2026 14:47:36 -0700 Subject: [PATCH 2/2] Address review comments. --- clang/include/clang/Options/Options.td | 9 +++++++-- llvm/lib/IR/Module.cpp | 2 +- 2 files changed, 8 insertions(+), 3 deletions(-) diff --git a/clang/include/clang/Options/Options.td b/clang/include/clang/Options/Options.td index 2bea20f9ad064..ebfed3f92339e 100644 --- a/clang/include/clang/Options/Options.td +++ b/clang/include/clang/Options/Options.td @@ -6074,8 +6074,13 @@ def mstack_protector_guard_offset_EQ : Joined<["-"], "mstack-protector-guard-off MarshallingInfoInt<CodeGenOpts<"StackProtectorGuardOffset">, "INT_MAX", "int">; def mstack_protector_guard_value_width_EQ : Joined<["-"], "mstack-protector-guard-value-width=">, Group<m_Group>, Visibility<[ClangOption, CC1Option]>, - HelpText<"Use the given width for the value of the the stack-protector guard">, - MarshallingInfoInt<CodeGenOpts<"StackProtectorGuardValueWidth">, "UINT_MAX", "unsigned">; + HelpText<"Use the given width for the value of the the stack-protector guard (AArch64-only)">, + MarshallingInfoInt<CodeGenOpts<"StackProtectorGuardValueWidth">, "UINT_MAX", "unsigned">, + DocBrief<[{Set the width of the stack-protector guard variable. By default, +the width is the same as the pointer width. Currently only supported on AArch64 +targets. Only the values "4" and "8" are currently supported. This currently +only modifies the size of accesses to the global variable, not the value +stored on the stack.}]>; def mstack_protector_guard_symbol_EQ : Joined<["-"], "mstack-protector-guard-symbol=">, Group<m_Group>, Visibility<[ClangOption, CC1Option]>, HelpText<"Use the given symbol for addressing the stack-protector guard">, diff --git a/llvm/lib/IR/Module.cpp b/llvm/lib/IR/Module.cpp index 95d7e75d1ec0a..07edccbaf75d6 100644 --- a/llvm/lib/IR/Module.cpp +++ b/llvm/lib/IR/Module.cpp @@ -810,7 +810,7 @@ void Module::setStackProtectorGuardOffset(int Offset) { std::optional<unsigned> Module::getStackProtectorGuardValueWidth() const { Metadata *MD = getModuleFlag("stack-protector-guard-value-width"); if (auto *CI = mdconst::dyn_extract_or_null<ConstantInt>(MD)) - return CI->getSExtValue(); + return CI->getZExtValue(); return std::nullopt; } _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
