Nico Weber 6613a4cb8c disasm: Insert symbol names in disassembly stream ...

The symbol name insertion scheme is different from objdump -d's.
Compare the output on Build/Userland/id:

* disasm:

        ...
        _start (08048305-0804836b):
        08048305  push ebp
        ...
        08048366  call 0x0000df56

        0804836b  o16 nop
        0804836d  o16 nop
        0804836f  nop

        (deregister_tm_clones (08048370-08048370))

        08048370  mov eax, 0x080643e0
        ...
        _ZN2AK8Utf8ViewC1ERKNS_6StringE (0805d9b2-0805d9b7):
        _ZN2AK8Utf8ViewC2ERKNS_6StringE (0805d9b2-0805d9b7):
        0805d9b2  jmp 0x00014ff2

        0805d9b7  nop

* objdump -d:

        08048305 <_start>:
         8048305:	55                   	push   %ebp
        ...
         8048366:	e8 9b dc 00 00       	call   8056006 <exit>
         804836b:	66 90                	xchg   %ax,%ax
         804836d:	66 90                	xchg   %ax,%ax
         804836f:	90                   	nop

        08048370 <deregister_tm_clones>:
         8048370:	b8 e0 43 06 08       	mov    $0x80643e0,%eax
        ...
        0805d9b2 <_ZN2AK8Utf8ViewC1ERKNS_6StringE>:
         805d9b2:	e9 eb f6 ff ff       	jmp    805d0a2 <_ZN2AK10StringViewC1ERKNS_6StringE>
         805d9b7:	90                   	nop

Differences:

1. disasm can show multiple symbols that cover the same instructions.
   I've only seen this happen for C1/C2 (and D1/D2) ctor/dtor pairs,
   but it could conceivably happen with ICF as well.

2. disasm separates instructions that do not belong to a symbol with
   a newline, so that nop padding isn't shown as part of a function
   when it technically isn't.

3. disasm shows symbols that are skipped (due to having size 0)
   in parenthesis, separated from preceding and following instructions.

2020-08-10 11:48:10 +02:00

6.7 KiB

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