http://llvm.org/bugs/show_bug.cgi?id=10397
Summary: X86 Disassembler Gives Wrong Sign for short JMP
Product: new-bugs
Version: 2.9
Platform: PC
OS/Version: Linux
Status: NEW
Severity: normal
Priority: P
Component: new bugs
AssignedTo: [email protected]
ReportedBy: [email protected]
CC: [email protected]
I'm disassembling an executable, but the MCInst for a JMP instruction seems to
have the wrong offset (or rather, doesn't preserve the original sign).
The original assembly (from gcc -S):
.file "hello.c"
.section .rodata
.LC0:
.string "Hello!"
.text
.globl main
.type main, @function
main:
.LFB0:
.cfi_startproc
pushq %rbp
.cfi_def_cfa_offset 16
movq %rsp, %rbp
.cfi_offset 6, -16
.cfi_def_cfa_register 6
subq $16, %rsp
movl %edi, -4(%rbp)
movq %rsi, -16(%rbp)
.L2:
movl $.LC0, %edi
call puts
jmp .L2 ; <<<<<< THIS ONE
.cfi_endproc
.LFE0:
.size main, .-main
.ident "GCC: (Ubuntu 4.4.3-4ubuntu5) 4.4.3"
.section .note.GNU-stack,"",@progbits
Main disassembles to:
Seeking to offset 1316 for executable's 27 bytes.
55 48 89 e5 48 83 ec 10 89 7d fc 48 89 75 f0 bf
2c 06 40 00 e8 db fe ff ff eb f4
0 [1899]: pushq %rbp
1 [1302]: movq %rsp, %rbp
4 [2311]: subq $16, %rsp
8 [1275]: movl %edi, -4(%rbp)
11 [1291]: movq %rsi, -16(%rbp)
15 [1280]: movl $4195884, %edi
20 [275]: callq -293
25 [936]: jmp 244 ; <<<< BAD!
The 244 as the argument to JMP seems to be the 2's complement inverse of what
it should be.
Linux 64-bit x86.
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