ddff9799d2
For a simple program like below:
-bash-4.4$ cat t.c
int test() {
asm volatile("r0 = r0" ::);
return 0;
}
compiled with
clang -target bpf -O2 -c t.c
the following llvm-objdump command will segfault.
llvm-objdump -d t.o
0: bf 00 00 00 00 00 00 00 nop
llvm-objdump: ../include/llvm/ADT/SmallVector.h:180
...
Assertion `idx < size()' failed
...
abort
...
llvm::BPFInstPrinter::printOperand
llvm::BPFInstPrinter::printInstruction
...
The reason is both NOP and MOV_rr (r0 = r0) having the same encoding.
The disassembly getInstruction() decodes to be a NOP instruciton but
during printInstruction() the same encoding is interpreted as
a MOV_rr instruction. Such a mismatcch caused the segfault.
The fix is to make NOP instruction as CodeGen only so disassembler
will skip NOP insn for disassembling.
Note that instruction "r0 = r0" should not appear in non inline
asm codes since BPF Machine Instruction Peephole optimization will
remove it.
Differential Revision: https://reviews.llvm.org/D80156
20 lines
442 B
LLVM
20 lines
442 B
LLVM
; RUN: llc -march=bpfel -filetype=obj -o - %s | llvm-objdump -d - | FileCheck %s
|
|
;
|
|
; Source:
|
|
; int test() {
|
|
; asm volatile("r0 = r0" ::);
|
|
; return 0;
|
|
; }
|
|
; Compilation flag:
|
|
; clang -target bpf -O2 -S -emit-llvm t.c
|
|
|
|
; Function Attrs: nounwind
|
|
define dso_local i32 @test() local_unnamed_addr {
|
|
entry:
|
|
tail call void asm sideeffect "r0 = r0", ""()
|
|
ret i32 0
|
|
}
|
|
; CHECK-LABEL: test
|
|
; CHECK: r0 = r0
|
|
; CHECK: r0 = 0
|