e67cbac812
Implement protection against the stack clash attack [0] through inline stack probing. Probe stack allocation every PAGE_SIZE during frame lowering or dynamic allocation to make sure the page guard, if any, is touched when touching the stack, in a similar manner to GCC[1]. This extends the existing `probe-stack' mechanism with a special value `inline-asm'. Technically the former uses function call before stack allocation while this patch provides inlined stack probes and chunk allocation. Only implemented for x86. [0] https://www.qualys.com/2017/06/19/stack-clash/stack-clash.txt [1] https://gcc.gnu.org/ml/gcc-patches/2017-07/msg00556.html This a recommit of 39f50da2a357a8f685b3540246c5d762734e035f with proper LiveIn declaration, better option handling and more portable testing. Differential Revision: https://reviews.llvm.org/D68720
32 lines
925 B
LLVM
32 lines
925 B
LLVM
; RUN: llc < %s | FileCheck %s
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target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-unknown-linux-gnu"
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declare void @llvm.memset.p0i8.i64(i8* nocapture writeonly, i8, i64, i1 immarg);
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define void @foo() local_unnamed_addr #0 {
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;CHECK-LABEL: foo:
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;CHECK: # %bb.0:
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;CHECK-NEXT: subq $4096, %rsp # imm = 0x1000
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; it's important that we don't use the call as a probe here
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;CHECK-NEXT: movq $0, (%rsp)
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;CHECK-NEXT: subq $3912, %rsp # imm = 0xF48
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;CHECK-NEXT: .cfi_def_cfa_offset 8016
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;CHECK-NEXT: movq %rsp, %rdi
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;CHECK-NEXT: movl $8000, %edx # imm = 0x1F40
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;CHECK-NEXT: xorl %esi, %esi
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;CHECK-NEXT: callq memset
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;CHECK-NEXT: addq $8008, %rsp # imm = 0x1F48
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;CHECK-NEXT: .cfi_def_cfa_offset 8
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;CHECK-NEXT: retq
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%a = alloca i8, i64 8000, align 16
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call void @llvm.memset.p0i8.i64(i8* align 16 %a, i8 0, i64 8000, i1 false)
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ret void
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}
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attributes #0 = {"probe-stack"="inline-asm"}
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