Re: Using dwarf_getfuncs to get function from object stored in memory

[Mark Wielaard <mark@klomp.org>]

Hi Jeff,

On Tue, Aug 17, 2021 at 03:40:08AM +0000, Jeff Lin via Elfutils-devel wrote:
> I’ve written code to extract function from a shared object with
> dwarf_begin api that finds the dwarf objects with the file
> descriptor using dwarf_getfuncs.  However, when I tried to parse the
> same object that is loaded into memory first, dwarf_getfuncs is not
> able to get the function.  In the case of accessing the object that
> is in memory, I used the following line to get the dwarf object:
>
>   Elf *ehandle = elf_memory(const_cast<char *>(so_file), size);
>   Dwarf *dw = dwarf_begin_elf(ehandle, DWARF_C_READ, NULL);
> 
> I am able to get the offset and tag with dwarf_nextcu, but errors
> out with dwarf_getfuncs.  Does anyone know why dwarf_getfuncs does
> return properly when trying to process dwarf object that was store
> in memory?

If the ELF in memory is the same as the ELF on disk I don't know why
dwarf_getfuncs would work differently. Does the callback get called?
Does dwarf_getfuncs return -1? What does dwarf_errmsg say?

Cheers,

Mark