Re: [Qemu-arm] [PATCH 01/11] target-arm: Give CPSR setting on 32-bit exception return its own helper

[Sergey Fedorov]

On 15.02.2016 20:22, Peter Maydell wrote:
> The rules for setting the CPSR on a 32-bit exception return are
> subtly different from those for setting the CPSR via an instruction
> like MSR or CPS. (In particular, in Hyp mode changing the mode bits
> is not valid via MSR or CPS.) Split the exception-return case into
> its own helper for setting CPSR, so we can eventually handle them
> differently in the helper function.
>
> Signed-off-by: Peter Maydell <address@hidden>

Reviewed-by: Sergey Fedorov <address@hidden>

> ---
>  target-arm/helper.h    | 1 +
>  target-arm/op_helper.c | 6 ++++++
>  target-arm/translate.c | 6 +++---
>  3 files changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/target-arm/helper.h b/target-arm/helper.h
> index c98e9ce..ea13202 100644
> --- a/target-arm/helper.h
> +++ b/target-arm/helper.h
> @@ -57,6 +57,7 @@ DEF_HELPER_2(pre_smc, void, env, i32)
>  DEF_HELPER_1(check_breakpoints, void, env)
>  
>  DEF_HELPER_3(cpsr_write, void, env, i32, i32)
> +DEF_HELPER_2(cpsr_write_eret, void, env, i32)
>  DEF_HELPER_1(cpsr_read, i32, env)
>  
>  DEF_HELPER_3(v7m_msr, void, env, i32, i32)
> diff --git a/target-arm/op_helper.c b/target-arm/op_helper.c
> index 538887c..e3ddd5a 100644
> --- a/target-arm/op_helper.c
> +++ b/target-arm/op_helper.c
> @@ -425,6 +425,12 @@ void HELPER(cpsr_write)(CPUARMState *env, uint32_t val, 
> uint32_t mask)
>      cpsr_write(env, val, mask);
>  }
>  
> +/* Write the CPSR for a 32-bit exception return */
> +void HELPER(cpsr_write_eret)(CPUARMState *env, uint32_t val)
> +{
> +    cpsr_write(env, val, CPSR_ERET_MASK);
> +}
> +
>  /* Access to user mode registers from privileged modes.  */
>  uint32_t HELPER(get_user_reg)(CPUARMState *env, uint32_t regno)
>  {
> diff --git a/target-arm/translate.c b/target-arm/translate.c
> index e69145d..413f7de 100644
> --- a/target-arm/translate.c
> +++ b/target-arm/translate.c
> @@ -4094,7 +4094,7 @@ static void gen_exception_return(DisasContext *s, 
> TCGv_i32 pc)
>      TCGv_i32 tmp;
>      store_reg(s, 15, pc);
>      tmp = load_cpu_field(spsr);
> -    gen_set_cpsr(tmp, CPSR_ERET_MASK);
> +    gen_helper_cpsr_write_eret(cpu_env, tmp);
>      tcg_temp_free_i32(tmp);
>      s->is_jmp = DISAS_JUMP;
>  }
> @@ -4102,7 +4102,7 @@ static void gen_exception_return(DisasContext *s, 
> TCGv_i32 pc)
>  /* Generate a v6 exception return.  Marks both values as dead.  */
>  static void gen_rfe(DisasContext *s, TCGv_i32 pc, TCGv_i32 cpsr)
>  {
> -    gen_set_cpsr(cpsr, CPSR_ERET_MASK);
> +    gen_helper_cpsr_write_eret(cpu_env, cpsr);
>      tcg_temp_free_i32(cpsr);
>      store_reg(s, 15, pc);
>      s->is_jmp = DISAS_JUMP;
> @@ -9094,7 +9094,7 @@ static void disas_arm_insn(DisasContext *s, unsigned 
> int insn)
>                  if (exc_return) {
>                      /* Restore CPSR from SPSR.  */
>                      tmp = load_cpu_field(spsr);
> -                    gen_set_cpsr(tmp, CPSR_ERET_MASK);
> +                    gen_helper_cpsr_write_eret(cpu_env, tmp);
>                      tcg_temp_free_i32(tmp);
>                      s->is_jmp = DISAS_JUMP;
>                  }