Re: Symbol not Detectable by Objdump

[Ahmad Nouralizadeh]

The (default system) binutils used for the above-mentioned outputs is
`2.30`. I also tried with `binutils-2.43.1` (i.e., the latest stable
release) and the problem was not resolved.

On Mon, 18 Nov 2024 at 15:59, Ahmad Nouralizadeh <ahmad.mlists@gmail.com> wrote:
>
> Hi,
> I have a shared library
> `/opt/evince-3.28.4/lib/evince/4/backends/libpdfdocument.so`. In GDB,
> I can easily detect a function at offset `0xa830` of this library, as
> shown below:
>
> (gdb) disas 0xa830
> Dump of assembler code for function ev_link_from_action(PdfDocument*,
> PopplerAction*):
>    0x000000000000a830 <+0>:     cmpl   $0xa,(%rsi)
>    0x000000000000a833 <+3>:     ja     0xaaf0
> <ev_link_from_action(PdfDocument*, PopplerAction*)+704>
>    0x000000000000a839 <+9>:     push   %r15
>    0x000000000000a83b <+11>:    push   %r14
>    0x000000000000a83d <+13>:    lea    0x5f28(%rip),%rdx        # 0x1076c
>
> The output of `objdump -D` on the library for this offset is shown below:
>
> a826:   66 2e 0f 1f 84 00 00    nopw   %cs:0x0(%rax,%rax,1)
> a82d:   00 00 00
> a830:   83 3e 0a                cmpl   $0xa,(%rsi)
> a833:   0f 87 b7 02 00 00       ja     aaf0 <__cxa_finalize@plt+0x1d10>
> a839:   41 57                   push   %r15
>
> No function name is printed at `0xa830`. Also, the output of `objdump
> -t` on the library does not contain this offset. How can I detect the
> symbol name assuming the offset is known and GDB is not available?
>
> Regards.
>
> -------------------
>
> P.S.: The shared library contains debuginfo. The relevant portion of
> `objdump -h` on the library is shown below:
>
>  25 .debug_aranges 00000030  0000000000000000  0000000000000000  00014bd9  
> 2**0
>               CONTENTS, READONLY, DEBUGGING
>  26 .debug_info   00014b8d  0000000000000000  0000000000000000  00014c09  2**0
>               CONTENTS, READONLY, DEBUGGING
>  27 .debug_abbrev 00000773  0000000000000000  0000000000000000  00029796  2**0
>               CONTENTS, READONLY, DEBUGGING
>  28 .debug_line   00002036  0000000000000000  0000000000000000  00029f09  2**0
>               CONTENTS, READONLY, DEBUGGING
>  29 .debug_str    0000c377  0000000000000000  0000000000000000  0002bf3f  2**0
>               CONTENTS, READONLY, DEBUGGING
>  30 .debug_loc    0000d45f  0000000000000000  0000000000000000  000382b6  2**0
>               CONTENTS, READONLY, DEBUGGING
>  31 .debug_ranges 00001080  0000000000000000  0000000000000000  00045715  2**0
>               CONTENTS, READONLY, DEBUGGING
>
> -------------------
>
> P.S.2: The question issue is also notified here:
>
> https://stackoverflow.com/questions/79196334/symbol-not-detectable-by-objdump