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 39f50da2a3 with proper LiveIn
declaration, better option handling and more portable testing.
Differential Revision: https://reviews.llvm.org/D68720
45 lines
1.3 KiB
LLVM
45 lines
1.3 KiB
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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define i32 @foo(i32 %n) local_unnamed_addr #0 {
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; CHECK-LABEL: foo:
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; CHECK: # %bb.0:
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; CHECK-NEXT: pushq %rbp
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; CHECK-NEXT: .cfi_def_cfa_offset 16
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; CHECK-NEXT: .cfi_offset %rbp, -16
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; CHECK-NEXT: movq %rsp, %rbp
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; CHECK-NEXT: .cfi_def_cfa_register %rbp
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; CHECK-NEXT: movl %edi, %eax
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; CHECK-NEXT: leaq 15(,%rax,4), %rax
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; CHECK-NEXT: andq $-16, %rax
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; CHECK-NEXT: cmpq $4096, %rax # imm = 0x1000
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; CHECK-NEXT: jl .LBB0_3
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; CHECK-NEXT: .LBB0_2: # =>This Inner Loop Header: Depth=1
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; CHECK-NEXT: subq $4096, %rax # imm = 0x1000
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; CHECK-NEXT: subq $4096, %rsp # imm = 0x1000
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; CHECK-NEXT: movq $0, (%rsp)
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; CHECK-NEXT: cmpq $4096, %rax # imm = 0x1000
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; CHECK-NEXT: jge .LBB0_2
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; CHECK-NEXT: .LBB0_3:
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; CHECK-NEXT: subq %rax, %rsp
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; CHECK-NEXT: movq %rsp, %rax
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; CHECK-NEXT: movl $1, 4792(%rax)
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; CHECK-NEXT: movl (%rax), %eax
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; CHECK-NEXT: movq %rbp, %rsp
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; CHECK-NEXT: popq %rbp
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; CHECK-NEXT: .cfi_def_cfa %rsp, 8
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; CHECK-NEXT: retq
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%a = alloca i32, i32 %n, align 16
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%b = getelementptr inbounds i32, i32* %a, i64 1198
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store volatile i32 1, i32* %b
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%c = load volatile i32, i32* %a
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ret i32 %c
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}
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attributes #0 = {"probe-stack"="inline-asm"}
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