Re: [PATCH v1 1/1] arch: microblaze: allocate stack space for register params

[Michal Simek]

On 3/27/26 09:54, Neal Frager wrote:
> C functions are invoked with arguments without allocating stack space for
> register params (for potential register spills). As a result kernel built
> with gcc v15 boot hangs at the point of starting init -.

Remove -.

> This patch adds necessary stack space for few C function calls from entry.S

Add necessary.

> (not all). After this patch, the kernel boots all the way to login prompt and
> root login works. Simple commands like ps work and show normal output.
>
> Signed-off-by: Gopi Kumar Bulusu <gopi@xxxxxxxxxxx>
> Tested-by: Neal Frager <neal.frager@xxxxxxx>

If you are sending it you should have sob line here.

> ---
>   arch/microblaze/kernel/entry.S | 20 ++++++++++++++------
>   1 file changed, 14 insertions(+), 6 deletions(-)
>
> diff --git a/arch/microblaze/kernel/entry.S b/arch/microblaze/kernel/entry.S
> index 582d7256d815..2f9604640486 100644
> --- a/arch/microblaze/kernel/entry.S
> +++ b/arch/microblaze/kernel/entry.S
> @@ -339,6 +339,9 @@ C_ENTRY(mb_invalidate_icache):
>    * Trap entered via brki instruction, so BIP bit is set, and interrupts
>    * are masked. This is nice, means we don't have to CLI before state save
>    */
> +
> +#define SYSCALL_ARGS_SIZE 36
> +
>   C_ENTRY(_user_exception):
>   	swi	r1, r0, TOPHYS(PER_CPU(ENTRY_SP)) /* save stack */
>   	addi	r14, r14, 4	/* return address is 4 byte after call */
> @@ -422,16 +425,19 @@ C_ENTRY(_user_exception):
>   	lwi	r12, r12, sys_call_table
>   	/* where the trap should return need -8 to adjust for rtsd r15, 8 */
>   	addi	r15, r0, ret_from_trap-8
> +	addik 	r1, r1, -SYSCALL_ARGS_SIZE

Please check coding style here.

I will test it on real HW and will talk to you directly about results.

Thanks,
Michal