[v2,7/9] arm: Track M profile handler mode state in TB flags

For M profile exception-return handling we'd like to generate different
code for some instructions depending on whether we are in Handler
mode or Thread mode. This isn't the same as "are we privileged
or user", so we need an extra bit in the TB flags to distinguish.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/cpu.h       | 9 +++++++++
 target/arm/translate.h | 1 +
 target/arm/translate.c | 1 +
 3 files changed, 11 insertions(+)

Hi Peter,

On 04/10/2017 02:13 PM, Peter Maydell wrote:
> For M profile exception-return handling we'd like to generate different
> code for some instructions depending on whether we are in Handler
> mode or Thread mode. This isn't the same as "are we privileged
> or user", so we need an extra bit in the TB flags to distinguish.
>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  target/arm/cpu.h       | 9 +++++++++
>  target/arm/translate.h | 1 +
>  target/arm/translate.c | 1 +
>  3 files changed, 11 insertions(+)
>
> diff --git a/target/arm/cpu.h b/target/arm/cpu.h
> index e6f05e2..7d26357 100644
> --- a/target/arm/cpu.h
> +++ b/target/arm/cpu.h
> @@ -2291,6 +2291,9 @@ static inline bool arm_cpu_data_is_big_endian(CPUARMState *env)
>  #define ARM_TBFLAG_NS_MASK          (1 << ARM_TBFLAG_NS_SHIFT)
>  #define ARM_TBFLAG_BE_DATA_SHIFT    20
>  #define ARM_TBFLAG_BE_DATA_MASK     (1 << ARM_TBFLAG_BE_DATA_SHIFT)
> +/* For M profile only, Handler (ie not Thread) mode */
> +#define ARM_TBFLAG_HANDLER_SHIFT    21
> +#define ARM_TBFLAG_HANDLER_MASK     (1 << ARM_TBFLAG_HANDLER_SHIFT)
>
>  /* Bit usage when in AArch64 state */
>  #define ARM_TBFLAG_TBI0_SHIFT 0        /* TBI0 for EL0/1 or TBI for EL2/3 */
> @@ -2327,6 +2330,8 @@ static inline bool arm_cpu_data_is_big_endian(CPUARMState *env)
>      (((F) & ARM_TBFLAG_NS_MASK) >> ARM_TBFLAG_NS_SHIFT)
>  #define ARM_TBFLAG_BE_DATA(F) \
>      (((F) & ARM_TBFLAG_BE_DATA_MASK) >> ARM_TBFLAG_BE_DATA_SHIFT)
> +#define ARM_TBFLAG_HANDLER(F) \
> +    (((F) & ARM_TBFLAG_HANDLER_MASK) >> ARM_TBFLAG_HANDLER_SHIFT)
>  #define ARM_TBFLAG_TBI0(F) \
>      (((F) & ARM_TBFLAG_TBI0_MASK) >> ARM_TBFLAG_TBI0_SHIFT)
>  #define ARM_TBFLAG_TBI1(F) \
> @@ -2517,6 +2522,10 @@ static inline void cpu_get_tb_cpu_state(CPUARMState *env, target_ulong *pc,
>      }
>      *flags |= fp_exception_el(env) << ARM_TBFLAG_FPEXC_EL_SHIFT;
>
> +    if (env->v7m.exception != 0) {
> +        *flags |= ARM_TBFLAG_HANDLER_MASK;
> +    }
> +
>      *cs_base = 0;
>  }
>
> diff --git a/target/arm/translate.h b/target/arm/translate.h
> index abb0760..f955174 100644
> --- a/target/arm/translate.h
> +++ b/target/arm/translate.h
> @@ -31,6 +31,7 @@ typedef struct DisasContext {
>      bool vfp_enabled; /* FP enabled via FPSCR.EN */
>      int vec_len;
>      int vec_stride;
> +    bool handler; /* v7M Handler mode */

What about a more descriptive name like 'is_v7m_handler_mode' or 
'v7m_mode_handler'? It makes your next patch easier to understand:

     if (s->handler && arm_dc_feature(s, ARM_FEATURE_M)) {

>      /* Immediate value in AArch32 SVC insn; must be set if is_jmp == DISAS_SWI
>       * so that top level loop can generate correct syndrome information.
>       */
> diff --git a/target/arm/translate.c b/target/arm/translate.c
> index f28c4ca..f980cda 100644
> --- a/target/arm/translate.c
> +++ b/target/arm/translate.c
> @@ -11780,6 +11780,7 @@ void gen_intermediate_code(CPUARMState *env, TranslationBlock *tb)
>      dc->vec_len = ARM_TBFLAG_VECLEN(tb->flags);
>      dc->vec_stride = ARM_TBFLAG_VECSTRIDE(tb->flags);
>      dc->c15_cpar = ARM_TBFLAG_XSCALE_CPAR(tb->flags);
> +    dc->handler = ARM_TBFLAG_HANDLER(tb->flags);
>      dc->cp_regs = cpu->cp_regs;
>      dc->features = env->features;
>
>

On 17 April 2017 at 05:20, Philippe Mathieu-Daudé <f4bug@amsat.org> wrote:
> On 04/10/2017 02:13 PM, Peter Maydell wrote:
>> --- a/target/arm/translate.h
>> +++ b/target/arm/translate.h
>> @@ -31,6 +31,7 @@ typedef struct DisasContext {
>>      bool vfp_enabled; /* FP enabled via FPSCR.EN */
>>      int vec_len;
>>      int vec_stride;
>> +    bool handler; /* v7M Handler mode */
>
>
> What about a more descriptive name like 'is_v7m_handler_mode' or
> 'v7m_mode_handler'? It makes your next patch easier to understand:

Seems reasonable; I've made that change (but won't repost the
series as that's the only tweak).

thanks
-- PMM