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
33 lines
896 B
LLVM
33 lines
896 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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define i32 @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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; CHECK-NEXT .cfi_def_cfa_offset 5888
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; CHECK-NEXT movl $1, 2088(%rsp)
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; CHECK-NEXT subq $1784, %rsp # imm = 0x6F8
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; CHECK-NEXT movl $2, 672(%rsp)
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; CHECK-NEXT movl 1872(%rsp), %eax
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; CHECK-NEXT addq $5880, %rsp # imm = 0x16F8
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; CHECK-NEXT .cfi_def_cfa_offset 8
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; CHECK-NEXT retq
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%a = alloca i32, i64 1000, align 16
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%b = alloca i32, i64 500, align 16
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%a0 = getelementptr inbounds i32, i32* %a, i64 500
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%b0 = getelementptr inbounds i32, i32* %b, i64 200
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store volatile i32 1, i32* %a0
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store volatile i32 2, i32* %b0
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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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