Re: what's parisc execve_wrapper doing in the end?

James Bottomley
2012-10-05T14:47:56Z

On Fri, 2012-10-05 at 14:44 +0100, James Bottomley wrote:
> On Fri, 2012-10-05 at 12:07 +0100, James Bottomley wrote:
> > I tried out the code at
> >
> > git://git.kernel.org/pub/scm/linux/kernel/git/viro/signal.git
> > experimental-kernel_thread
> >
> > and it gives me this panic on boot.
>
> OK, found the fix: the idle thread is a kernel thread, but it doesn't
> come through kernel_thread(). The fix is to check for it (fortunately
> it has the signal usp == 0).
>
> I'm now getting as freeing the init memory, which then hangs, so I
> suspect some type of execve failure trying to start the initrd... I'm
> debugging.

And the fix for this one is below: ret_from_kernel_execve has pt_regs in
%r26 ... it needs to be in %r16 for intr_return, so we just copy them
over.

With this, I can bring up the kernel all the way to a login prompt with
no apparent ill effects.

James

---

diff --git a/arch/parisc/kernel/entry.S b/arch/parisc/kernel/entry.S
index 272c7a0..dd137fc 100644
--- a/arch/parisc/kernel/entry.S
+++ b/arch/parisc/kernel/entry.S
@@ -744,7 +744,8 @@ ENDPROC(ret_from_kernel_thread)
ENTRY(ret_from_kernel_execve)
mfctl %cr30, %r1
ldo THREAD_SZ_ALGN(%r1), %r30
- b,n intr_return /* forward */
+ b intr_return /* forward */
+ copy %r26,%r16 /* pt_regs into r16 */
ENDPROC(ret_from_kernel_execve)