2021-02-05 08:27:35

by Andreas Oetken

Subject: [PATCH] nios2: fixed broken sys_clone syscall

From: Andreas Oetken <[email protected]>

The tls pointer must be pushed on the stack prior to calling nios2_clone
as it is the 5th function argument. Prior handling of the tls pointer was
done inside former called function copy_thread_tls using the r8 register
from the current_pt_regs directly. This was a bad design and resulted in
the current bug introduced in 04bd52fb.

Fixes: 04bd52fb ("nios2: enable HAVE_COPY_THREAD_TLS, switch to kernel_clone_args")
Signed-off-by: Andreas Oetken <[email protected]>
---
arch/nios2/kernel/entry.S | 3 +++
1 file changed, 3 insertions(+)

diff --git a/arch/nios2/kernel/entry.S b/arch/nios2/kernel/entry.S
index da8442450e46..0794cd7803df 100644
--- a/arch/nios2/kernel/entry.S
+++ b/arch/nios2/kernel/entry.S
@@ -389,7 +389,10 @@ ENTRY(ret_from_interrupt)
*/
ENTRY(sys_clone)
SAVE_SWITCH_STACK
+ subi sp, sp, 4 /* make space for tls pointer */
+ stw r8, 0(sp) /* pass tls pointer (r8) via stack (5th argument) */
call nios2_clone
+ addi sp, sp, 4
RESTORE_SWITCH_STACK
ret

--
2.30.0

2021-02-05 08:43:38

by Christian Brauner

Subject: Re: [PATCH] nios2: fixed broken sys_clone syscall

On Fri, Feb 05, 2021 at 09:23:38AM +0100, Andreas Oetken wrote:
> From: Andreas Oetken <[email protected]>
>
> The tls pointer must be pushed on the stack prior to calling nios2_clone
> as it is the 5th function argument. Prior handling of the tls pointer was
> done inside former called function copy_thread_tls using the r8 register
> from the current_pt_regs directly. This was a bad design and resulted in
> the current bug introduced in 04bd52fb.
>
> Fixes: 04bd52fb ("nios2: enable HAVE_COPY_THREAD_TLS, switch to kernel_clone_args")
> Signed-off-by: Andreas Oetken <[email protected]>
> ---

Thanks for catching this!
Acked-by: Christian Brauner <[email protected]>