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[WebAssembly] Generate unreachable after __stack_chk_fail

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`__stack_chk_fail` does not return, but `unreachable` was not generated
following `call __stack_chk_fail`. This had a possibility to generate an
invalid binary for functions with a return type, because
`__stack_chk_fail`'s return type is void and `call __stack_chk_fail` can
be the last instruction in the function whose return type is non-void.
Generating `unreachable` after it makes sure CFGStackify's
`fixEndsAtEndOfFunction` handles it correctly.

Reviewed By: tlively

Differential Revision: https://reviews.llvm.org/D83277
This commit is contained in:
Heejin Ahn 2020-07-08 00:59:21 -07:00
parent 4414d94c30
commit 07746c07ec
2 changed files with 32 additions and 6 deletions
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5
lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
View File

@ -2668,6 +2668,11 @@ SelectionDAGBuilder::visitSPDescriptorFailure(StackProtectorDescriptor &SPD) {
// Passing 'true' for doesNotReturn above won't generate the trap for us. // Passing 'true' for doesNotReturn above won't generate the trap for us.
if (TM.getTargetTriple().isPS4CPU()) if (TM.getTargetTriple().isPS4CPU())
Chain = DAG.getNode(ISD::TRAP, getCurSDLoc(), MVT::Other, Chain); Chain = DAG.getNode(ISD::TRAP, getCurSDLoc(), MVT::Other, Chain);
// WebAssembly needs an unreachable instruction after a non-returning call,
// because the function return type can be different from __stack_chk_fail's
// return type (void).
if (TM.getTargetTriple().isWasm())
Chain = DAG.getNode(ISD::TRAP, getCurSDLoc(), MVT::Other, Chain);
DAG.setRoot(Chain); DAG.setRoot(Chain);
} }

33
test/CodeGen/WebAssembly/stack-protector.ll
View File

@ -1,13 +1,13 @@
; RUN: llc -verify-machineinstrs -mtriple=wasm32-unknown-unknown < %s | FileCheck -check-prefix=WASM32 %s ; RUN: llc -verify-machineinstrs -mtriple=wasm32-unknown-unknown < %s | FileCheck -check-prefix=WASM32 %s
; WASM32: i32.load 28
; WASM32-NEXT: i32.ne
; WASM32-NEXT: br_if 0
; WASM32: __stack_chk_fail
@"\01LC" = internal constant [11 x i8] c"buf == %s\0A\00" ; <[11 x i8]*> [#uses=1] @"\01LC" = internal constant [11 x i8] c"buf == %s\0A\00" ; <[11 x i8]*> [#uses=1]
; WASM32-LABEL: test
; WASM32: i32.load 28
; WASM32: br_if 0
; WASM32: call __stack_chk_fail
; WASM32-NEXT: unreachable
define void @test(i8* %a) nounwind ssp { define void @test(i8* %a) nounwind ssp {
entry: entry:
%a_addr = alloca i8* ; <i8**> [#uses=2] %a_addr = alloca i8* ; <i8**> [#uses=2]
@ -25,6 +25,27 @@ return: ; preds = %entry
ret void ret void
} }
; WASM32-LABEL: test_return_i32
; WASM32: call __stack_chk_fail
; WASM32-NEXT: unreachable
define i32 @test_return_i32(i8* %a) nounwind ssp {
entry:
%a_addr = alloca i8* ; <i8**> [#uses=2]
%buf = alloca [8 x i8] ; <[8 x i8]*> [#uses=2]
%"alloca point" = bitcast i32 0 to i32 ; <i32> [#uses=0]
store i8* %a, i8** %a_addr
%buf1 = bitcast [8 x i8]* %buf to i8* ; <i8*> [#uses=1]
%0 = load i8*, i8** %a_addr, align 4 ; <i8*> [#uses=1]
%1 = call i8* @strcpy(i8* %buf1, i8* %0) nounwind ; <i8*> [#uses=0]
%buf2 = bitcast [8 x i8]* %buf to i8* ; <i8*> [#uses=1]
%2 = call i32 (i8*, ...) @printf(i8* getelementptr ([11 x i8], [11 x i8]* @"\01LC", i32 0, i32 0), i8* %buf2) nounwind ; <i32> [#uses=0]
br label %return
return: ; preds = %entry
ret i32 0
}
declare i8* @strcpy(i8*, i8*) nounwind declare i8* @strcpy(i8*, i8*) nounwind
declare i32 @printf(i8*, ...) nounwind declare i32 @printf(i8*, ...) nounwind