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The patch resolves the conflict between AddressSanitizer and load widening (GVN).

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The problem initially reported by Mozilla folks (http://code.google.com/p/address-sanitizer/issues/detail?id=20),
but it also prevents us from enabling LLVM bootstrap with AddressSanitizer.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@149925 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Kostya Serebryany 2012-02-06 22:48:56 +00:00
parent 44ebf8b033
commit 0ca032b03d
2 changed files with 51 additions and 0 deletions
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8
lib/Analysis/MemoryDependenceAnalysis.cpp
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@ -323,6 +323,14 @@ getLoadLoadClobberFullWidthSize(const Value *MemLocBase, int64_t MemLocOffs,
!TD.fitsInLegalInteger(NewLoadByteSize*8)) !TD.fitsInLegalInteger(NewLoadByteSize*8))
return 0; return 0;
if (LIOffs+NewLoadByteSize > MemLocEnd &&
LI->getParent()->getParent()->hasFnAttr(Attribute::AddressSafety)) {
// We will be reading past the location accessed by the original program.
// While this is safe in a regular build, Address Safety analysis tools
// may start reporting false warnings. So, don't do widening.
return 0;
}
// If a load of this width would include all of MemLoc, then we succeed. // If a load of this width would include all of MemLoc, then we succeed.
if (LIOffs+NewLoadByteSize >= MemLocEnd) if (LIOffs+NewLoadByteSize >= MemLocEnd)
return NewLoadByteSize; return NewLoadByteSize;

43
test/Instrumentation/AddressSanitizer/asan-vs-gvn.ll Normal file
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@ -0,0 +1,43 @@
; RUN: opt < %s -basicaa -gvn -asan -S | FileCheck %s
; ASAN conflicts with load widening iff the widened load accesses data out of bounds
; (while the original unwidened loads do not).
; http://code.google.com/p/address-sanitizer/issues/detail?id=20#c1
; 32-bit little endian target.
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128-n8:16:32"
%struct_of_7_bytes_4_aligned = type { i32, i8, i8, i8}
@f = global %struct_of_7_bytes_4_aligned zeroinitializer, align 4
; Accessing bytes 4 and 6, not ok to widen to i32 if address_safety is set.
define i32 @test_widening_bad(i8* %P) nounwind ssp noredzone address_safety {
entry:
%tmp = load i8* getelementptr inbounds (%struct_of_7_bytes_4_aligned* @f, i64 0, i32 1), align 4
%conv = zext i8 %tmp to i32
%tmp1 = load i8* getelementptr inbounds (%struct_of_7_bytes_4_aligned* @f, i64 0, i32 3), align 1
%conv2 = zext i8 %tmp1 to i32
%add = add nsw i32 %conv, %conv2
ret i32 %add
; CHECK: @test_widening_bad
; CHECK: __asan_report_load1
; CHECK: __asan_report_load1
; CHECK-ret i32
}
;; Accessing byets 4 and 5. Ok to widen to i16.
define i32 @test_widening_ok(i8* %P) nounwind ssp noredzone address_safety {
entry:
%tmp = load i8* getelementptr inbounds (%struct_of_7_bytes_4_aligned* @f, i64 0, i32 1), align 4
%conv = zext i8 %tmp to i32
%tmp1 = load i8* getelementptr inbounds (%struct_of_7_bytes_4_aligned* @f, i64 0, i32 2), align 1
%conv2 = zext i8 %tmp1 to i32
%add = add nsw i32 %conv, %conv2
ret i32 %add
; CHECK: @test_widening_ok
; CHECK: __asan_report_load1
; CHECK-ret i32
}