Andy Lutomirski schreef op 13/06/2014 7:23:
On Thu, Jun 12, 2014 at 10:15 PM, H. Peter Anvin <[email protected]> wrote:
On 06/12/2014 09:36 PM, Andy Lutomirski wrote:
If we were to implement both, maybe we'd actually want to provide
something like:
struct vdso_entry {
unsigned long vdso_entry_struct_size; /* so we can add fields later on */
void *func;
unsigned int max_stack; /* zero if not known */
};
How different is this really from the .dynsym table -- other than that
you have to find the latter via the dynamic segment?
The hash part is just to speed up lookup...
As far as I know, there's no reliable way to just read the dynsym
table -- the thing doesn't have a specified length, which is what
broke Go in the first place.
Parsing the ELF dynamic tables is kind of annoyingly complicated, and
understanding the format is a real PITA -- the documentation I've been
able to find is outright terrible.
--Andy
Why does it need a specified length? It's pretty easy to find, the
entries have a fixed length and the last entry in the table is NULLed
out (i.e. the d_tag is DT_NULL).
Just look for the PT_DYNAMIC segment in the program headers and iterate
over the fixed length Elf_Dyn entries to find what you're looking for.
As for ELF documentation, I've never had any problems understanding the
official specification:
http://refspecs.linuxbase.org/elf/elf.pdf
--Stijn
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