Re: [PATCH 6/6] target/sh4: Implement prctl_unalign_sigbus

[Laurent Vivier]

Le 20/12/2021 à 22:41, Richard Henderson a écrit :
> Leave TARGET_ALIGNED_ONLY set, but use the new CPUState
> flag to set MO_UNALN for the instructions that the kernel
> handles in the unaligned trap.
>
> The Linux kernel does not handle all memory operations: no
> floating-point and no MAC.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>   linux-user/sh4/target_prctl.h |  2 +-
>   target/sh4/cpu.h              |  4 +++
>   target/sh4/translate.c        | 50 ++++++++++++++++++++++++-----------
>   3 files changed, 39 insertions(+), 17 deletions(-)
>
> diff --git a/linux-user/sh4/target_prctl.h b/linux-user/sh4/target_prctl.h
> index eb53b31ad5..5629ddbf39 100644
> --- a/linux-user/sh4/target_prctl.h
> +++ b/linux-user/sh4/target_prctl.h
> @@ -1 +1 @@
> -/* No special prctl support required. */
> +#include "../generic/target_prctl_unalign.h"
> diff --git a/target/sh4/cpu.h b/target/sh4/cpu.h
> index 4cfb109f56..fb9dd9db2f 100644
> --- a/target/sh4/cpu.h
> +++ b/target/sh4/cpu.h
> @@ -83,6 +83,7 @@
>   #define DELAY_SLOT_RTE         (1 << 2)
>   
>   #define TB_FLAG_PENDING_MOVCA  (1 << 3)
> +#define TB_FLAG_UNALIGN        (1 << 4)
>   
>   #define GUSA_SHIFT             4
>   #ifdef CONFIG_USER_ONLY
> @@ -373,6 +374,9 @@ static inline void cpu_get_tb_cpu_state(CPUSH4State *env, 
> target_ulong *pc,
>               | (env->sr & ((1u << SR_MD) | (1u << SR_RB)))      /* Bits 29-30 
> */
>               | (env->sr & (1u << SR_FD))                        /* Bit 15 */
>               | (env->movcal_backup ? TB_FLAG_PENDING_MOVCA : 0); /* Bit 3 */
> +#ifdef CONFIG_USER_ONLY
> +    *flags |= TB_FLAG_UNALIGN * !env_cpu(env)->prctl_unalign_sigbus;
> +#endif
>   }
>   
>   #endif /* SH4_CPU_H */
> diff --git a/target/sh4/translate.c b/target/sh4/translate.c
> index ce5d674a52..c959ce1508 100644
> --- a/target/sh4/translate.c
> +++ b/target/sh4/translate.c
> @@ -50,8 +50,10 @@ typedef struct DisasContext {
>   
>   #if defined(CONFIG_USER_ONLY)
>   #define IS_USER(ctx) 1
> +#define UNALIGN(C)   (ctx->tbflags & TB_FLAG_UNALIGN ? MO_UNALN : 0)

Why isn't it like the other targets: "ctx->tb_flags & TB_FLAG_UNALIGN ? MO_UNALN : 
MO_ALIGN)"?

>   #else
>   #define IS_USER(ctx) (!(ctx->tbflags & (1u << SR_MD)))
> +#define UNALIGN(C)   0
>   #endif
>   
>   /* Target-specific values for ctx->base.is_jmp.  */

Thanks,
Laurent