"Steven J. Hill" <sjhill@cotw.com> writes:
> Greetings.
>
> I am working on a MIPS dynamic linker/loader for uClibc and
> would appreciate some clarification on the finer points of
> ELF and the Linux kernel interface. Forgive the cross post.
>
> The first problem I have discovered is that the value of
> argc passed back to the userspace process from the Linux
> kernel is always zero. The argv, environment and auxillary
> vectors come through just fine. I have to loop through the
> stack manually to count the number of argument vectors in
> order to get argc:
In glibc I had no problems finding argc, check
sysdeps/mips/elf/start.S:
/* This is the canonical entry point, usually the first thing in the text
segment. The SVR4/Mips ABI (pages 3-31, 3-32) says that when the entry
point runs, most registers' values are unspecified, except for:
v0 ($2) Contains a function pointer to be registered with `atexit'.
This is how the dynamic linker arranges to have DT_FINI
functions called for shared libraries that have been loaded
before this code runs.
sp ($29) The stack contains the arguments and environment:
0(%esp) argc
4(%esp) argv[0]
...
(4*argc)(%esp) NULL
(4*(argc+1))(%esp) envp[0]
...
NULL
ra ($31) The return address register is set to zero so that programs
that search backword through stack frames recognize the last
stack frame.
*/
Andreas
--
Andreas Jaeger
SuSE Labs aj@suse.de
private aj@arthur.inka.de
http://www.suse.de/~aj
