Re: [Qemu-devel] [PATCH v2 1/2] linux-user: improve fake /proc/self/stat making `ps` not segfault.

[Alexander Graf]

On 03.01.2012, at 20:20, Fabio Erculiani wrote:

> With the current fake /proc/self/stat implementation `ps` is
> segfaulting because it expects to read PID and argv[0] as first and
> second field respectively, with the latter being enclosed between
> backets.
> 
> Reproducing is as easy as running: `ps` inside qemu-user chroot
> with /proc mounted.
> 
> Signed-off-by: Fabio Erculiani <address@hidden>
> ---
> linux-user/syscall.c |   21 ++++++++++++++++-----
> 1 files changed, 16 insertions(+), 5 deletions(-)
> 
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index 9ba51bf..e563c00 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -4678,14 +4678,25 @@ static int open_self_stat(void *cpu_env, int fd)
>       int len;
>       uint64_t val = 0;
> 
> -      if (i == 27) {
> -          /* stack bottom */
> -          val = start_stack;
> +      if (i == 0) {
> +        /* pid */
> +        val = getpid();
> +        snprintf(buf, sizeof(buf), "%"PRId64 " ", val);
> +      } else if (i == 1) {
> +        /* app name */
> +        snprintf(buf, sizeof(buf), "(%s) ", ts->bprm->argv[0]);
> +      } else if (i == 27) {
> +        /* stack bottom */
> +        val = start_stack;
> +        snprintf(buf, sizeof(buf), "%"PRId64 " ", val);
> +      } else {
> +        /* for the rest, there is MasterCard */
> +        snprintf(buf, sizeof(buf), "0%c", i == 43 ? '\n' : ' ');
>       }
> -      snprintf(buf, sizeof(buf), "%"PRId64 "%c", val, i == 43 ? '\n' : ' ');
> +
>       len = strlen(buf);
>       if (write(fd, buf, len) != len) {
> -          return -1;
> +        return -1;

This looks suspicious :).

The rest looks good!


Alex