[llvm-bugs] [Bug 38186] New: llvm-objdump doesn't handle symbols referring the .plt section, or print symbols within it.

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=38186

            Bug ID: 38186
           Summary: llvm-objdump doesn't handle symbols referring the .plt
                    section, or print symbols within it.
           Product: tools
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: llvm-objdump
          Assignee: unassignedbugs at nondot.org
          Reporter: saugustine at google.com
                CC: llvm-bugs at lists.llvm.org

Without the symbols listed in the .plt section, it is hard to know exactly what
symbol is being called. In this example, the only thing that appears is an
offset at the call site, and no symbols at all inside the .plt section. Compare
this to gnu objdump.

$ cat t.s
        .section .text,"ax", at progbits
        .global foo
foo:
        call foo at plt

$ ./bin/clang t.s -fpic -c
$ ./bin/ld.lld t.o -shared
$ ./bin/llvm-objdump -d a.out

a.out:  file format ELF64-x86-64

Disassembly of section .text:
foo:
    1000:       e8 1b 00 00 00  callq   27
Disassembly of section .plt:
.plt:
    1010:       ff 35 f2 0f 00 00       pushq   4082(%rip)
    1016:       ff 25 f4 0f 00 00       jmpq    *4084(%rip)
    101c:       0f 1f 40 00     nopl    (%rax)
    1020:       ff 25 f2 0f 00 00       jmpq    *4082(%rip)
    1026:       68 00 00 00 00  pushq   $0
    102b:       e9 e0 ff ff ff  jmp     -32 <.plt>

Compare that to gnu's objdump:

$ objdump -d a.out

a.out:     file format elf64-x86-64


Disassembly of section .text:

0000000000001000 <foo>:
    1000:       e8 1b 00 00 00          callq  1020 <foo at plt>

Disassembly of section .plt:

0000000000001010 <foo at plt-0x10>:
    1010:       ff 35 f2 0f 00 00       pushq  0xff2(%rip)        # 2008
<foo at plt+0xfe8>
    1016:       ff 25 f4 0f 00 00       jmpq   *0xff4(%rip)        # 2010
<foo at plt+0xff0>
    101c:       0f 1f 40 00             nopl   0x0(%rax)

0000000000001020 <foo at plt>:
    1020:       ff 25 f2 0f 00 00       jmpq   *0xff2(%rip)        # 2018
<foo at plt+0xff8>
    1026:       68 00 00 00 00          pushq  $0x0
    102b:       e9 e0 ff ff ff          jmpq   1010 <foo+0x10>

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