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[asan] add option to set shadow mapping offset

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Allowing overriding the default ASAN shadow mapping offset with the
-asan-shadow-offset option, and allow zero to be specified for both offset and
scale.

Patch by Aaron Carroll <aaronc@apple.com>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@268724 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Ryan Govostes 2016-05-06 10:25:22 +00:00
parent 31372e2522
commit 7cf5d6815b
2 changed files with 48 additions and 2 deletions
lib/Transforms/Instrumentation
AddressSanitizer.cpp
test/Instrumentation/AddressSanitizer
scale-offset.ll

11
lib/Transforms/Instrumentation/AddressSanitizer.cpp

@ -204,10 +204,13 @@ static cl::opt<bool> ClSkipPromotableAllocas(
// These flags allow to change the shadow mapping.
// The shadow mapping looks like
// Shadow = (Mem >> scale) + (1 << offset_log)
// Shadow = (Mem >> scale) + offset
static cl::opt<int> ClMappingScale("asan-mapping-scale",
cl::desc("scale of asan shadow mapping"),
cl::Hidden, cl::init(0));
static cl::opt<unsigned long long> ClMappingOffset("asan-mapping-offset",
cl::desc("offset of asan shadow mapping [EXPERIMENTAL]"),
cl::Hidden, cl::init(0));
// Optimization flags. Not user visible, used mostly for testing
// and benchmarking the tool.
@ -404,10 +407,14 @@ static ShadowMapping getShadowMapping(Triple &TargetTriple, int LongSize,
}
Mapping.Scale = kDefaultShadowScale;
if (ClMappingScale) {
if (ClMappingScale.getNumOccurrences() > 0) {
Mapping.Scale = ClMappingScale;
}
if (ClMappingOffset.getNumOccurrences() > 0) {
Mapping.Offset = ClMappingOffset;
}
// OR-ing shadow offset if more efficient (at least on x86) if the offset
// is a power of two, but on ppc64 we have to use add since the shadow
// offset is not necessary 1/8-th of the address space. On SystemZ,

39
test/Instrumentation/AddressSanitizer/scale-offset.ll Normal file

@ -0,0 +1,39 @@
; Test that the scale (-asan-mapping-scale) and offset (-asan-mapping-offset) command-line options work as expected
;
; RUN: opt < %s -asan -asan-module -asan-mapping-offset 0xdeadbeef -S | FileCheck --check-prefix=CHECK-OFFSET %s
; RUN: opt < %s -asan -asan-module -asan-mapping-scale 1 -S | FileCheck --check-prefix=CHECK-SCALE %s
; RUN: opt < %s -asan -asan-module -asan-mapping-offset 0xc0ffee -asan-mapping-scale 0 -S | FileCheck --check-prefix=CHECK-BOTH %s
target triple = "x86_64-unknown-linux-gnu"
define i32 @read_offset(i32* %a) sanitize_address {
entry:
%tmp1 = load i32, i32* %a, align 4
ret i32 %tmp1
}
; CHECK-OFFSET-LABEL: @read_offset
; CHECK-OFFSET-NOT: ret
; CHECK-OFFSET: lshr {{.*}} 3
; CHECK-OFFSET-NEXT: add{{.*}}3735928559
; CHECK-OFFSET: ret
define i32 @read_scale(i32* %a) sanitize_address {
entry:
%tmp1 = load i32, i32* %a, align 4
ret i32 %tmp1
}
; CHECK-SCALE-LABEL: @read_scale
; CHECK-SCALE-NOT: ret
; CHECK-SCALE: lshr {{.*}} 1
; CHECK-SCALE-NEXT: add{{.*}}
; CHECK-SCALE: ret
define i32 @read_both(i32* %a) sanitize_address {
entry:
%tmp1 = load i32, i32* %a, align 4
ret i32 %tmp1
}
; CHECK-BOTH-LABEL: @read_both
; CHECK-BOTH-NOT: ret
; CHECK-BOTH: lshr {{.*}} 0
; CHECK-BOTH-NEXT: add{{.*}}12648430
; CHECK-BOTH: ret