[LLVMdev] llvm-objdump does not give information about all relocations

[Aleksandrs Saveljevs]

Hi,

We are trying to use LLVM API to programmatically obtain a list of
relocations in an ELF file. The way we are doing this is exactly as
llvm-objdump does it: we are iterating through sections and in each
section we are iterating over relocations (see PrintRelocations()
function at https://llvm.org/svn/llvm-project/llvm/trunk/tools/llvm-objdump/llvm-objdump.cpp).
However, it does not give us relocation entries in .rela.dyn section.

Consider, for instance, the output of "readelf -r /bin/true":

$ readelf -r /bin/true

Relocation section '.rela.dyn' at offset 0xa80 contains 5 entries:
  Offset          Info           Type           Sym. Value    Sym. Name + Addend
000000604c38  001800000006 R_X86_64_GLOB_DAT 0000000000000000 __gmon_start__ + 0
000000604de0  002800000005 R_X86_64_COPY     0000000000604de0 __progname + 0
000000604df0  002700000005 R_X86_64_COPY     0000000000604df0 stdout + 0
000000604e00  002a00000005 R_X86_64_COPY     0000000000604e00
__progname_full + 0
000000604e08  002c00000005 R_X86_64_COPY     0000000000604e08 stderr + 0

Relocation section '.rela.plt' at offset 0xaf8 contains 37 entries:
  Offset          Info           Type           Sym. Value    Sym. Name + Addend
000000604c60  000100000007 R_X86_64_JUMP_SLO 0000000000000000 free + 0
000000604c68  000200000007 R_X86_64_JUMP_SLO 0000000000000000 abort + 0
000000604c70  000300000007 R_X86_64_JUMP_SLO 0000000000000000
__errno_location + 0
000000604c78  000400000007 R_X86_64_JUMP_SLO 0000000000000000 _exit + 0
000000604c80  000500000007 R_X86_64_JUMP_SLO 0000000000000000 __fpending + 0
...

(The list for .rela.plt has been truncated for brevity.)

If we now run "llvm-objdump-3.1 -r /bin/true", we will get a list of
entries in .rela.plt section:

$ llvm-objdump-3.1 -r /bin/true | grep -c JUMP_SLOT
37

So the question is: why llvm-objdump does not list relocation entries
in .rela.dyn section and is it possible to get at them somehow?

Aleksandrs