Re: [Qemu-devel] [PATCH v3 22/26] Add a fallback bios file search, if -L fails.

[Michael Tokarev]

On 20.10.2012 00:43, Jason Baron wrote:
> From: Jason Baron <address@hidden>
> 
> If -L <dir> is specified, and qemu does not find the bios file in <dir>, then
> the search fails. Add infrastructure such that the search will continue in
> the default paths, if not found in the -L path.
> 
> Reviewed-by: Paolo Bonzini <address@hidden>
> Signed-off-by: Jason Baron <address@hidden>
> ---
>  vl.c |   36 +++++++++++++++++++++++++-----------
>  1 files changed, 25 insertions(+), 11 deletions(-)
> 
> diff --git a/vl.c b/vl.c
> index 6b1e546..2a2d217 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -177,6 +177,7 @@ int main(int argc, char **argv)
>  #define MAX_VIRTIO_CONSOLES 1
>  
>  static const char *data_dir;
> +static const char *data_dir_fallback;
>  const char *bios_name = NULL;
>  enum vga_retrace_method vga_retrace_method = VGA_RETRACE_DUMB;
>  DisplayType display_type = DT_DEFAULT;
> @@ -1892,16 +1893,16 @@ static int balloon_parse(const char *arg)
>      return -1;
>  }
>  
> -char *qemu_find_file(int type, const char *name)
> +static char *qemu_find_file_in_dir(int type, const char *name, const char 
> *dir)
>  {
>      int len;
>      const char *subdir;
>      char *buf;
>  
> -    /* Try the name as a straight path first */
> -    if (access(name, R_OK) == 0) {
> -        return g_strdup(name);
> +    if (!dir) {
> +        return NULL;
>      }
> +
>      switch (type) {
>      case QEMU_FILE_TYPE_BIOS:
>          subdir = "";
> @@ -1912,9 +1913,9 @@ char *qemu_find_file(int type, const char *name)
>      default:
>          abort();
>      }
> -    len = strlen(data_dir) + strlen(name) + strlen(subdir) + 2;
> +    len = strlen(dir) + strlen(name) + strlen(subdir) + 2;
>      buf = g_malloc0(len);
> -    snprintf(buf, len, "%s/%s%s", data_dir, subdir, name);
> +    snprintf(buf, len, "%s/%s%s", dir, subdir, name);
>      if (access(buf, R_OK)) {
>          g_free(buf);
>          return NULL;
> @@ -1922,6 +1923,21 @@ char *qemu_find_file(int type, const char *name)
>      return buf;
>  }
>  
> +char *qemu_find_file(int type, const char *name)
> +{
> +    char *filename;
> +
> +    /* Try the name as a straight path first */
> +    if (access(name, R_OK) == 0) {
> +        return g_strdup(name);
> +    }

FWIW, this can be a security issue, when a more privileged
user tries to run qemu from trusted path (/usr/bin) in a
directory owned by non-privileged user, to utilize -runas
or somesuch.  I understand it's been this way since the
beginning.

Maybe we can do a bit better here, like (windows systems
aside) this:

    if (strchr(name, '/') && access(name, R_OK) == 0) {...}

Note that -L can be set to "." in order to check in current
directory too.

And going forward, maybe we can treat -L argument as a PATH
(separated by whatever delimiter is okay) instead of just
a single directory?  This way, for example, we can put
various kinds of data (pxe roms, vgabios roms etc) into
different places and qemu will be able to find them all.

I understand this whole thing is not really related to q35
changes, so can be pushed/applied separately.

Thanks,

/mjt