[PATCH v3 6/6] lib: sbi: call platform load/store emulators

[Anup Patel]

On Sat, Mar 2, 2024 at 4:55 PM Bo Gan <ganboing at gmail.com> wrote:
>
> sbi_load/store_fault_handler now tries to call platform emulators
> if defined. Otherwise, redirects the fault.
>
> We let the handler fail if the trap was originated from M mode. In
> this case, something must be very wrong and we should not attempt
> to access sbi_platform_ptr(sbi_scratch_thishart_ptr()).
>
> Signed-off-by: Bo Gan <ganboing at gmail.com>
> ---
>  include/sbi/sbi_platform.h | 25 +++++++++++++++++++++++++
>  lib/sbi/sbi_trap_ldst.c    | 17 +++++++++++++++--
>  2 files changed, 40 insertions(+), 2 deletions(-)
>
> diff --git a/include/sbi/sbi_platform.h b/include/sbi/sbi_platform.h
> index 06247dc..c556925 100644
> --- a/include/sbi/sbi_platform.h
> +++ b/include/sbi/sbi_platform.h
> @@ -48,6 +48,7 @@
>  #include <sbi/sbi_error.h>
>  #include <sbi/sbi_scratch.h>
>  #include <sbi/sbi_version.h>
> +#include <sbi/sbi_trap_ldst.h>
>
>  struct sbi_domain_memregion;
>  struct sbi_ecall_return;
> @@ -686,6 +687,30 @@ static inline int sbi_platform_vendor_ext_provider(
>         return SBI_ENOTSUPP;
>  }
>
> +static inline int
> +sbi_platform_emulate_load(const struct sbi_platform *plat,
> +                         struct sbi_trap_regs *regs,
> +                         const struct sbi_trap_info *orig_trap)
> +{
> +       if (plat && sbi_platform_ops(plat)->emulate_load) {
> +               return sbi_trap_emulate_load(
> +                       regs, orig_trap, sbi_platform_ops(plat)->emulate_load);
> +       }
> +       return sbi_trap_redirect(regs, orig_trap);
> +}
> +
> +static inline int
> +sbi_platform_emulate_store(const struct sbi_platform *plat,
> +                          struct sbi_trap_regs *regs,
> +                          const struct sbi_trap_info *orig_trap)
> +{
> +       if (plat && sbi_platform_ops(plat)->emulate_store) {
> +               return sbi_trap_emulate_store(
> +                       regs, orig_trap, sbi_platform_ops(plat)->emulate_store);
> +       }
> +       return sbi_trap_redirect(regs, orig_trap);
> +}
> +

These should be implemented as follows:

static inline int
sbi_platform_emulate_load(const struct sbi_platform *plat,
                         int rlen, union sbi_reg_data *out_val)
{
       if (plat && sbi_platform_ops(plat)->emulate_load) {
               return sbi_platform_ops(plat)->emulate_load(rlen, out_val);
       }
       return SBI_ENOTSUPP;
}

static inline int
sbi_platform_emulate_store(const struct sbi_platform *plat,
                          int wlen, union sbi_reg_data in_val)
{
       if (plat && sbi_platform_ops(plat)->emulate_store) {
               return sbi_platform_ops(plat)->emulate_store(wlen, in_val);
       }
       return SBI_ENOTSUPP;
}

>  #endif
>
>  #endif
> diff --git a/lib/sbi/sbi_trap_ldst.c b/lib/sbi/sbi_trap_ldst.c
> index 5516954..606830e 100644
> --- a/lib/sbi/sbi_trap_ldst.c
> +++ b/lib/sbi/sbi_trap_ldst.c
> @@ -15,6 +15,7 @@
>  #include <sbi/sbi_pmu.h>
>  #include <sbi/sbi_trap.h>
>  #include <sbi/sbi_unpriv.h>
> +#include <sbi/sbi_platform.h>
>
>  static ulong sbi_misaligned_tinst_fixup(ulong orig_tinst, ulong new_tinst,
>                                         ulong addr_offset)
> @@ -294,11 +295,23 @@ int sbi_misaligned_store_handler(struct sbi_trap_regs *regs,
>  int sbi_load_fault_handler(struct sbi_trap_regs *regs,
>                            const struct sbi_trap_info *orig_trap)
>  {
> -       return sbi_trap_redirect(regs, orig_trap);
> +       /* If fault came from M mode, just fail */
> +       if (((regs->mstatus & MSTATUS_MPP) >> MSTATUS_MPP_SHIFT) == PRV_M) {
> +               return SBI_EINVAL;
> +       }
> +
> +       return sbi_platform_emulate_load(sbi_platform_thishart_ptr(), regs,
> +                                        orig_trap);
>  }
>
>  int sbi_store_fault_handler(struct sbi_trap_regs *regs,
>                             const struct sbi_trap_info *orig_trap)
>  {
> -       return sbi_trap_redirect(regs, orig_trap);
> +       /* If fault came from M mode, just fail */
> +       if (((regs->mstatus & MSTATUS_MPP) >> MSTATUS_MPP_SHIFT) == PRV_M) {
> +               return SBI_EINVAL;
> +       }
> +
> +       return sbi_platform_emulate_store(sbi_platform_thishart_ptr(), regs,
> +                                         orig_trap);
>  }
> --
> 2.7.4
>

Regards,
Anup