Re: [PATCH] target/m68k: Fix exception frame format for 68010

[Laurent Vivier <laurent@vivier.eu>]

Le 15/01/2024 à 11:16, Daniel Palmer a écrit :
>  From the 68010 a word with the frame format and exception vector
> are placed on the stack before the PC and SR.
> 
> M68K_FEATURE_QUAD_MULDIV is currently checked to workout if to do
> this or not for the configured CPU but that flag isn't set for
> 68010 so currently the exception stack when 68010 is configured
> is incorrect.
> 
> It seems like checking M68K_FEATURE_MOVEFROMSR_PRIV would do but
> adding a new flag that shows exactly what is going on here is
> maybe clearer.
> 
> Add a new flag for the behaviour, M68K_FEATURE_EXCEPTION_FORMAT_VEC,
> and set it for 68010 and above, and then use it to control if the
> format and vector word are pushed/pop during exception entry/exit.
> 
> Signed-off-by: Daniel Palmer <daniel@0x0f.com>
> ---
>   target/m68k/cpu.c       | 4 +++-
>   target/m68k/cpu.h       | 2 ++
>   target/m68k/op_helper.c | 4 ++--
>   3 files changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/target/m68k/cpu.c b/target/m68k/cpu.c
> index 1421e77c2c07..20718944b4c8 100644
> --- a/target/m68k/cpu.c
> +++ b/target/m68k/cpu.c
> @@ -137,7 +137,8 @@ static void m68000_cpu_initfn(Object *obj)
>   }
>   
>   /*
> - * Adds BKPT, MOVE-from-SR *now priv instr, and MOVEC, MOVES, RTD
> + * Adds BKPT, MOVE-from-SR *now priv instr, and MOVEC, MOVES, RTD,
> + *      format+vector in exception frame.
>    */
>   static void m68010_cpu_initfn(Object *obj)
>   {
> @@ -150,6 +151,7 @@ static void m68010_cpu_initfn(Object *obj)
>       m68k_set_feature(env, M68K_FEATURE_BKPT);
>       m68k_set_feature(env, M68K_FEATURE_MOVEC);
>       m68k_set_feature(env, M68K_FEATURE_MOVEFROMSR_PRIV);
> +    m68k_set_feature(env, M68K_FEATURE_EXCEPTION_FORMAT_VEC);
>   }
>   
>   /*
> diff --git a/target/m68k/cpu.h b/target/m68k/cpu.h
> index d13427b0fe61..0fc591e618f6 100644
> --- a/target/m68k/cpu.h
> +++ b/target/m68k/cpu.h
> @@ -549,6 +549,8 @@ enum m68k_features {
>       M68K_FEATURE_TRAPCC,
>       /* MOVE from SR privileged (from 68010) */
>       M68K_FEATURE_MOVEFROMSR_PRIV,
> +    /* Exception frame with format+vector (from 68010) */
> +    M68K_FEATURE_EXCEPTION_FORMAT_VEC,
>   };
>   
>   static inline bool m68k_feature(CPUM68KState *env, int feature)
> diff --git a/target/m68k/op_helper.c b/target/m68k/op_helper.c
> index 1ce850bbc594..b09771672dec 100644
> --- a/target/m68k/op_helper.c
> +++ b/target/m68k/op_helper.c
> @@ -52,7 +52,7 @@ throwaway:
>       sp += 2;
>       env->pc = cpu_ldl_mmuidx_ra(env, sp, MMU_KERNEL_IDX, 0);
>       sp += 4;
> -    if (m68k_feature(env, M68K_FEATURE_QUAD_MULDIV)) {
> +    if (m68k_feature(env, M68K_FEATURE_EXCEPTION_FORMAT_VEC)) {
>           /*  all except 68000 */
>           fmt = cpu_lduw_mmuidx_ra(env, sp, MMU_KERNEL_IDX, 0);
>           sp += 2;
> @@ -256,7 +256,7 @@ static inline void do_stack_frame(CPUM68KState *env, uint32_t *sp,
>                                     uint16_t format, uint16_t sr,
>                                     uint32_t addr, uint32_t retaddr)
>   {
> -    if (m68k_feature(env, M68K_FEATURE_QUAD_MULDIV)) {
> +    if (m68k_feature(env, M68K_FEATURE_EXCEPTION_FORMAT_VEC)) {
>           /*  all except 68000 */
>           CPUState *cs = env_cpu(env);
>           switch (format) {

Reviewed-by: Laurent Vivier <laurent@vivier.eu>