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
32 lines
925 B
LLVM
32 lines
925 B
LLVM
; RUN: llc < %s | FileCheck %s
|
|
|
|
|
|
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
|
|
target triple = "x86_64-unknown-linux-gnu"
|
|
|
|
declare void @llvm.memset.p0i8.i64(i8* nocapture writeonly, i8, i64, i1 immarg);
|
|
|
|
define void @foo() local_unnamed_addr #0 {
|
|
|
|
;CHECK-LABEL: foo:
|
|
;CHECK: # %bb.0:
|
|
;CHECK-NEXT: subq $4096, %rsp # imm = 0x1000
|
|
; it's important that we don't use the call as a probe here
|
|
;CHECK-NEXT: movq $0, (%rsp)
|
|
;CHECK-NEXT: subq $3912, %rsp # imm = 0xF48
|
|
;CHECK-NEXT: .cfi_def_cfa_offset 8016
|
|
;CHECK-NEXT: movq %rsp, %rdi
|
|
;CHECK-NEXT: movl $8000, %edx # imm = 0x1F40
|
|
;CHECK-NEXT: xorl %esi, %esi
|
|
;CHECK-NEXT: callq memset
|
|
;CHECK-NEXT: addq $8008, %rsp # imm = 0x1F48
|
|
;CHECK-NEXT: .cfi_def_cfa_offset 8
|
|
;CHECK-NEXT: retq
|
|
|
|
%a = alloca i8, i64 8000, align 16
|
|
call void @llvm.memset.p0i8.i64(i8* align 16 %a, i8 0, i64 8000, i1 false)
|
|
ret void
|
|
}
|
|
|
|
attributes #0 = {"probe-stack"="inline-asm"}
|