Re: [PATCH V5 08/11] riscv: Support HAVE_IRQ_EXIT_ON_IRQ_STACK

Chen Zhongjin
2022-09-21T08:42:42Z

Hi,

On 2022/9/18 23:52, guoren@kernel.org wrote:
> diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
> index 5f49517cd3a2..426529b84db0 100644
> --- a/arch/riscv/kernel/entry.S
> +++ b/arch/riscv/kernel/entry.S
> @@ -332,6 +332,33 @@ ENTRY(ret_from_kernel_thread)
> tail syscall_exit_to_user_mode
> ENDPROC(ret_from_kernel_thread)
>
> +#ifdef CONFIG_IRQ_STACKS
> +ENTRY(call_on_stack)
> + /* Create a frame record to save our ra and fp */
> + addi sp, sp, -RISCV_SZPTR
> + REG_S ra, (sp)
> + addi sp, sp, -RISCV_SZPTR
> + REG_S fp, (sp)
> +
> + /* Save sp in fp */
> + move fp, sp
> +
> + /* Move to the new stack and call the function there */
> + li a3, IRQ_STACK_SIZE
> + add sp, a1, a3
> + jalr a2
> +
> + /*
> + * Restore sp from prev fp, and fp, ra from the frame
> + */
> + move sp, fp
> + REG_L fp, (sp)
> + addi sp, sp, RISCV_SZPTR
> + REG_L ra, (sp)
> + addi sp, sp, RISCV_SZPTR
> + ret
> +ENDPROC(call_on_stack)
> +#endif

Seems my compiler (riscv64-linux-gnu-gcc 8.4.0, cross compiling from
x86) cannot recognize the register `fp`.

After I changed it to `s0` this can pass compiling.

Seems there is nowhere else using `fp`, can this just using `s0` instead?

Best,

Chen