Re: [Minios-devel] [PATCH v3 21/43] arm64: define the CALLEE_SAVED_REGISTERS

[Julien Grall <julien.grall@xxxxxxx>]

Hi,

On 16/04/18 07:32, Huang Shijie wrote:
> In the arm64, the callee-saved registers are x19 ~ x29.
s/In the/On/.

I think it would be good to mention where that convention comes from as 
this is not very obvious for non-arm expert :). This convention is from 
AAPCS64 [1].
> This patch also removes the macro for arm32.
>
> Signed-off-by: Huang Shijie <shijie.huang@xxxxxxx>
> ---
>   arch/arm/sched.c       | 4 +---
>   include/arm/arm64/os.h | 3 +++
>   2 files changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm/sched.c b/arch/arm/sched.c
> index 8091566..d1af379 100644
> --- a/arch/arm/sched.c
> +++ b/arch/arm/sched.c
> @@ -1,12 +1,10 @@
>   #include <mini-os/sched.h>
>   #include <mini-os/xmalloc.h>
>   #include <mini-os/console.h>
> +#include <mini-os/os.h>
>   
>   void arm_start_thread(void);
>   
> -/* The AAPCS requires the callee (e.g. __arch_switch_threads) to preserve r4-r11. */
> -#define CALLEE_SAVED_REGISTERS 8
> -
>   /* Architecture specific setup of thread creation */
>   struct thread* arch_create_thread(char *name, void (*function)(void *),
>                                     void *data)
> diff --git a/include/arm/arm64/os.h b/include/arm/arm64/os.h
> index 3d4aada..89b4002 100644
> --- a/include/arm/arm64/os.h
> +++ b/include/arm/arm64/os.h
> @@ -25,4 +25,7 @@ static inline void local_irq_enable(void)
>       __asm__ __volatile__("mrs %0, daif":"=r"(x)::"memory"); \
>   }
>   
> +/* The Callee-saved registers : x19 ~ x29 */
Same here, I would mention the AAPCS64. Also I quite like the comments 
that was existing for arm32. It gives some pointer to the reader where 
to look at. So I would say:
"The AAPCS64 requires the callee (e.g __arch_switch_threads) to preserve 
x19-x29.".
Cheers,

> +#define CALLEE_SAVED_REGISTERS 11
> +
>   #endif
--
Julien Grall

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