Re: [Qemu-devel] [Qemu-arm] [PATCH v4 4/5] aarch64-linux-user: Add support for EXTRA signal frame records

["Alex Bennée" <alex.bennee@linaro.org>]

Richard Henderson <richard.henderson@linaro.org> writes:

> The EXTRA record allows for additional space to be allocated
> beyon what is currently reserved.  Add code to emit and read
> this record type.
>
> Nothing uses extra space yet.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

> ---
>  linux-user/signal.c | 74 +++++++++++++++++++++++++++++++++++++++++++++--------
>  1 file changed, 63 insertions(+), 11 deletions(-)
>
> diff --git a/linux-user/signal.c b/linux-user/signal.c
> index f9eef3d753..c31cf0601d 100644
> --- a/linux-user/signal.c
> +++ b/linux-user/signal.c
> @@ -1443,6 +1443,15 @@ struct target_fpsimd_context {
>      uint64_t vregs[32 * 2]; /* really uint128_t vregs[32] */
>  };
>
> +#define TARGET_EXTRA_MAGIC  0x45585401
> +
> +struct target_extra_context {
> +    struct target_aarch64_ctx head;
> +    uint64_t datap; /* 16-byte aligned pointer to extra space cast to __u64 */
> +    uint32_t size; /* size in bytes of the extra space */
> +    uint32_t reserved[3];
> +};
> +
>  struct target_rt_sigframe {
>      struct target_siginfo info;
>      struct target_ucontext uc;
> @@ -1502,6 +1511,15 @@ static void target_setup_fpsimd_record(struct target_fpsimd_context *fpsimd,
>      }
>  }
>
> +static void target_setup_extra_record(struct target_extra_context *extra,
> +                                      uint64_t datap, uint32_t extra_size)
> +{
> +    __put_user(TARGET_EXTRA_MAGIC, &extra->head.magic);
> +    __put_user(sizeof(struct target_extra_context), &extra->head.size);
> +    __put_user(datap, &extra->datap);
> +    __put_user(extra_size, &extra->size);
> +}
> +
>  static void target_setup_end_record(struct target_aarch64_ctx *end)
>  {
>      __put_user(0, &end->magic);
> @@ -1554,48 +1572,74 @@ static void target_restore_fpsimd_record(CPUARMState *env,
>  static int target_restore_sigframe(CPUARMState *env,
>                                     struct target_rt_sigframe *sf)
>  {
> -    struct target_aarch64_ctx *ctx;
> +    struct target_aarch64_ctx *ctx, *extra = NULL;
>      struct target_fpsimd_context *fpsimd = NULL;
> +    uint64_t extra_datap = 0;
> +    bool used_extra = false;
> +    bool err = false;
>
>      target_restore_general_frame(env, sf);
>
>      ctx = (struct target_aarch64_ctx *)sf->uc.tuc_mcontext.__reserved;
>      while (ctx) {
> -        uint32_t magic, size;
> +        uint32_t magic, size, extra_size;
>
>          __get_user(magic, &ctx->magic);
>          __get_user(size, &ctx->size);
>          switch (magic) {
>          case 0:
>              if (size != 0) {
> -                return 1;
> +                err = true;
> +                goto exit;
> +            }
> +            if (used_extra) {
> +                ctx = NULL;
> +            } else {
> +                ctx = extra;
> +                used_extra = true;
>              }
> -            ctx = NULL;
>              continue;
>
>          case TARGET_FPSIMD_MAGIC:
>              if (fpsimd || size != sizeof(struct target_fpsimd_context)) {
> -                return 1;
> +                err = true;
> +                goto exit;
>              }
>              fpsimd = (struct target_fpsimd_context *)ctx;
>              break;
>
> +        case TARGET_EXTRA_MAGIC:
> +            if (extra || size != sizeof(struct target_extra_context)) {
> +                err = true;
> +                goto exit;
> +            }
> +            __get_user(extra_datap,
> +                       &((struct target_extra_context *)ctx)->datap);
> +            __get_user(extra_size,
> +                       &((struct target_extra_context *)ctx)->size);
> +            extra = lock_user(VERIFY_READ, extra_datap, extra_size, 0);
> +            break;
> +
>          default:
>              /* Unknown record -- we certainly didn't generate it.
>               * Did we in fact get out of sync?
>               */
> -            return 1;
> +            err = true;
> +            goto exit;
>          }
>          ctx = (void *)ctx + size;
>      }
>
>      /* Require FPSIMD always.  */
> -    if (!fpsimd) {
> -        return 1;
> +    if (fpsimd) {
> +        target_restore_fpsimd_record(env, fpsimd);
> +    } else {
> +        err = true;
>      }
> -    target_restore_fpsimd_record(env, fpsimd);
>
> -    return 0;
> + exit:
> +    unlock_user(extra, extra_datap, 0);
> +    return err;
>  }
>
>  static abi_ulong get_sigframe(struct target_sigaction *ka, CPUARMState *env)
> @@ -1621,7 +1665,8 @@ static void target_setup_frame(int usig, struct target_sigaction *ka,
>                                 CPUARMState *env)
>  {
>      int size = offsetof(struct target_rt_sigframe, uc.tuc_mcontext.__reserved);
> -    int fpsimd_ofs, end1_ofs, fr_ofs;
> +    int fpsimd_ofs, end1_ofs, fr_ofs, end2_ofs = 0;
> +    int extra_ofs = 0, extra_base = 0, extra_size = 0;
>      struct target_rt_sigframe *frame;
>      struct target_rt_frame_record *fr;
>      abi_ulong frame_addr, return_addr;
> @@ -1641,7 +1686,14 @@ static void target_setup_frame(int usig, struct target_sigaction *ka,
>
>      target_setup_general_frame(frame, env, set);
>      target_setup_fpsimd_record((void *)frame + fpsimd_ofs, env);
> +    if (extra_ofs) {
> +        target_setup_extra_record((void *)frame + extra_ofs,
> +                                  frame_addr + extra_base, extra_size);
> +    }
>      target_setup_end_record((void *)frame + end1_ofs);
> +    if (end2_ofs) {
> +        target_setup_end_record((void *)frame + end2_ofs);
> +    }
>
>      /* Set up the stack frame for unwinding.  */
>      fr = (void *)frame + fr_ofs;


--
Alex Bennée