> The execve_wrapper macro loads thread->task like this:
> LDREG TI_TASK-THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1
>
> This assumes that at the point the macro is called that there is only
> THREAD_SZ_ALGN+FRAME_SIZE between %r30 and the starting value of %r30
> (cr30).
>
> However, in the syscall entry path I see (syscall.S):
> ldo THREAD_SZ_ALGN+FRAME_SIZE(%r30),%r30 /* set up kernel stack */
> ...
> STREGM %r1,FRAME_SIZE(%r30) /* save r1 (usp) here for now */
>
> Which means that between %r30 and the start there is actually
> THREAD_SZ_ALGN+2*FRAME_SIZE.
This is wrong as there is a compensating LDREGM:
LDREGM -FRAME_SIZE(%r30), %r2 /* get users sp back */
> or heaven forbid the easier to read:
>
> mfctl %cr30,%r1 /* get task ptr in %r1 */
> LDREG TI_TASK(%r1),%r1
The above looks safer...
Dave
--
J. David Anglin dave.anglin@xxxxxxxxxxxxxx
National Research Council of Canada (613) 990-0752 (FAX: 952-6602)
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