[PATCH] D91677: Avoid transforming fortified bcopy to memmove
Siddhesh Poyarekar via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Tue Nov 17 20:12:57 PST 2020
siddhesh created this revision.
siddhesh added a reviewer: serge-sans-paille.
siddhesh added a project: LLVM.
Herald added subscribers: llvm-commits, hiraditya.
siddhesh requested review of this revision.
When simplifying libcalls, llvm transforms bcopy calls to memmove. This is incorrect when building fortified objects because the C library implements bcopy as an extern inline that calls __builtin___memmove_chk and the transformation ends up removing that fortification.
The proposed fix modifies the transformation so that it is avoided when the bcopy has a call instruction, thus skipping over any inline bcopy implementations that may call additional routines for diagnostics, including the fortified __memmove_chk.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D91677
Files:
llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
llvm/test/Transforms/InstCombine/bcopy-chk.ll
Index: llvm/test/Transforms/InstCombine/bcopy-chk.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/InstCombine/bcopy-chk.ll
@@ -0,0 +1,27 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -O1 -S | FileCheck %s
+
+declare i8* @__memmove_chk(i8*, i8*, i64, i64)
+declare i64 @llvm.objectsize.i64.p0i8(i8*, i1, i1, i1)
+
+define available_externally dso_local void @bcopy(i8* nocapture readonly %src, i8* nocapture %dst, i64 %len) #0 {
+ %size = call i64 @llvm.objectsize.i64.p0i8(i8* %dst, i1 false, i1 true, i1 false)
+ call i8* @__memmove_chk(i8* %dst, i8* %src, i64 %len, i64 %size)
+ ret void
+}
+
+ at buf = dso_local global [4 x i8] zeroinitializer, align 1
+
+define dso_local void @fortified_bcopy(i64 %argc) {
+; CHECK-LABEL: @fortified_bcopy(
+; CHECK-NEXT: [[ADD:%.*]] = add i64 [[ARGC:%.*]], 1
+; CHECK-NEXT: [[TMP1:%.*]] = call i8* @__memmove_chk(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @buf, i64 0, i64 2), i8* getelementptr inbounds ([4 x i8], [4 x i8]* @buf, i64 0, i64 1), i64 [[ADD]], i64 2)
+; CHECK-NEXT: ret void
+;
+ %add = add i64 %argc, 1
+ tail call void @bcopy(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @buf, i64 0, i64 1), i8* getelementptr inbounds ([4 x i8], [4 x i8]* @buf, i64 0, i64 2), i64 %add) #1
+ ret void
+}
+
+attributes #0 = { alwaysinline }
+attributes #1 = { builtin }
Index: llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
===================================================================
--- llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -2821,6 +2821,16 @@
}
Value *LibCallSimplifier::optimizeBCopy(CallInst *CI, IRBuilderBase &B) {
+ // Do not transform a bcopy call into llvm.memmove if it calls into another
+ // function. This ensures that the fortified implementation with
+ // __builtin___memmove_chk is not overriden.
+ Function *Callee = CI->getCalledFunction();
+ if (!Callee->empty()) {
+ BasicBlock &BB = Callee->getEntryBlock();
+ if (isa<CallInst>(BB.getFirstNonPHIOrDbgOrLifetime()))
+ return nullptr;
+ }
+
// bcopy(src, dst, n) -> llvm.memmove(dst, src, n)
return B.CreateMemMove(CI->getArgOperand(1), Align(1), CI->getArgOperand(0),
Align(1), CI->getArgOperand(2));
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