Re: [PATCH v2 12/17] linux-user/aarch64: Pass syndrome to EXC_*_ABORT

[Peter Maydell]

On Fri, 5 Jun 2020 at 05:17, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> A proper syndrome is required to fill in the proper si_code.
> Use page_get_flags to determine permission vs translation
> for user-only.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  linux-user/aarch64/cpu_loop.c | 23 ++++++++++++++++++++---
>  target/arm/tlb_helper.c       | 27 +++++++++++++++++++++------
>  2 files changed, 41 insertions(+), 9 deletions(-)
>
> diff --git a/linux-user/aarch64/cpu_loop.c b/linux-user/aarch64/cpu_loop.c
> index 3cca637bb9..ce56e15be2 100644
> --- a/linux-user/aarch64/cpu_loop.c
> +++ b/linux-user/aarch64/cpu_loop.c
> @@ -75,7 +75,7 @@
>  void cpu_loop(CPUARMState *env)
>  {
>      CPUState *cs = env_cpu(env);
> -    int trapnr;
> +    int trapnr, ec, fsc;
>      abi_long ret;
>      target_siginfo_t info;
>
> @@ -116,9 +116,26 @@ void cpu_loop(CPUARMState *env)
>          case EXCP_DATA_ABORT:
>              info.si_signo = TARGET_SIGSEGV;
>              info.si_errno = 0;
> -            /* XXX: check env->error_code */
> -            info.si_code = TARGET_SEGV_MAPERR;
>              info._sifields._sigfault._addr = env->exception.vaddress;
> +
> +            /* We should only arrive here with EC in {DATAABORT, INSNABORT}. 
> */
> +            ec = extract32(env->exception.syndrome, 26, 6);

 ec = syn_get_ec(env->exception.syndrome);

(though it's in internals.h which implies moving it I guess).

> +            assert(ec == 0x24 || ec == 0x20);

assert(ec == EC_DATAABORT || ec == EC_INSNABORT);

> +
> +            /* Both EC have the same format for FSC, or close enough. */
> +            fsc = extract32(env->exception.syndrome, 0, 6);
> +            switch (fsc) {
> +            case 0x04 ... 0x07: /* Translation fault, level {0-3} */
> +                info.si_code = TARGET_SEGV_MAPERR;
> +                break;
> +            case 0x09 ... 0x0b: /* Access flag fault, level {1-3} */
> +            case 0x0d ... 0x0f: /* Permission fault, level {1-3} */
> +                info.si_code = TARGET_SEGV_ACCERR;
> +                break;
> +            default:
> +                g_assert_not_reached();
> +            }
> +
>              queue_signal(env, info.si_signo, QEMU_SI_FAULT, &info);
>              break;
>          case EXCP_UNALIGNED:
> diff --git a/target/arm/tlb_helper.c b/target/arm/tlb_helper.c
> index d4e6d37f4f..35d84ac24f 100644
> --- a/target/arm/tlb_helper.c
> +++ b/target/arm/tlb_helper.c
> @@ -10,8 +10,6 @@
>  #include "internals.h"
>  #include "exec/exec-all.h"
>
> -#if !defined(CONFIG_USER_ONLY)
> -
>  static inline uint32_t merge_syn_data_abort(uint32_t template_syn,
>                                              unsigned int target_el,
>                                              bool same_el, bool ea,
> @@ -51,6 +49,8 @@ static inline uint32_t merge_syn_data_abort(uint32_t 
> template_syn,
>      return syn;
>  }
>
> +#if !defined(CONFIG_USER_ONLY)
> +
>  static void QEMU_NORETURN arm_deliver_fault(ARMCPU *cpu, vaddr addr,
>                                              MMUAccessType access_type,
>                                              int mmu_idx, ARMMMUFaultInfo *fi)
> @@ -138,13 +138,28 @@ bool arm_cpu_tlb_fill(CPUState *cs, vaddr address, int 
> size,
>      ARMCPU *cpu = ARM_CPU(cs);
>
>  #ifdef CONFIG_USER_ONLY
> +    int flags, fsc, exc;
> +    unsigned syn;
> +
>      cpu->env.exception.vaddress = address;
> -    if (access_type == MMU_INST_FETCH) {
> -        cs->exception_index = EXCP_PREFETCH_ABORT;
> +
> +    flags = page_get_flags(useronly_clean_ptr(address));
> +    if (flags & PAGE_VALID) {
> +        fsc = 0xf; /* permission fault, level 3 */
>      } else {
> -        cs->exception_index = EXCP_DATA_ABORT;
> +        fsc = 0x7; /* translation fault, level 3 */
>      }
> -    cpu_loop_exit_restore(cs, retaddr);
> +
> +    cpu_restore_state(cs, retaddr, true);
> +    if (access_type == MMU_INST_FETCH) {
> +        exc = EXCP_PREFETCH_ABORT;
> +        syn = syn_insn_abort(0, 0, 0, fsc);
> +    } else {
> +        exc = EXCP_DATA_ABORT;
> +        syn = merge_syn_data_abort(cpu->env.exception.syndrome, 1, 0, 0, 0,
> +                                   access_type == MMU_DATA_STORE, fsc);
> +    }
> +    raise_exception(&cpu->env, exc, syn, 1);

Should we call arm_deliver_fault() the way the other series
does for linux-user alignment faults ?

thanks
-- PMM