Re: [dpdk-dev] [PATCH v3 2/2] eal/linux: Add support for handling built-in kernel modules

[David Marchand <david.marchand@6wind.com>]

On Mon, Dec 7, 2015 at 7:36 PM, Kamil Rytarowski <
Kamil.Rytarowski@caviumnetworks.com> wrote:

> Currently rte_eal_check_module() detects Linux kernel modules via reading
> /proc/modules. Built-in ones aren't listed there and therefore they are not
> being found by the script.
>
> Add support for checking built-in modules with parsing the sysfs files
>
> This commit obsoletes the /proc/modules parsing approach.
>
> Signed-off-by: Kamil Rytarowski <Kamil.Rytarowski@caviumnetworks.com>
> ---
>  lib/librte_eal/linuxapp/eal/eal.c | 32 +++++++++++++++++---------------
>  1 file changed, 17 insertions(+), 15 deletions(-)
>
> diff --git a/lib/librte_eal/linuxapp/eal/eal.c
> b/lib/librte_eal/linuxapp/eal/eal.c
> index 635ec36..539188f 100644
> --- a/lib/librte_eal/linuxapp/eal/eal.c
> +++ b/lib/librte_eal/linuxapp/eal/eal.c
> @@ -52,6 +52,8 @@
>  #if defined(RTE_ARCH_X86_64) || defined(RTE_ARCH_I686)
>  #include <sys/io.h>
>  #endif
> +#include <sys/types.h>
> +#include <sys/stat.h>
>
>  #include <rte_common.h>
>  #include <rte_debug.h>
> @@ -901,27 +903,27 @@ int rte_eal_has_hugepages(void)
>  int
>  rte_eal_check_module(const char *module_name)
>  {
> -       char mod_name[30]; /* Any module names can be longer than 30
> bytes? */
> -       int ret = 0;
> -       int n;
> +       char sysfs_mod_name[PATH_MAX];
> +       struct stat st;
>
>         if (NULL == module_name)
>                 return -1;
>
> -       FILE *fd = fopen("/proc/modules", "r");
> -       if (NULL == fd) {
> -               RTE_LOG(ERR, EAL, "Open /proc/modules failed!"
> -                       " error %i (%s)\n", errno, strerror(errno));
> +       /* Check if there is sysfs mounted */
> +       if (stat("/sys/module", &st) != 0) {
> +               RTE_LOG(DEBUG, EAL, "Open /sys/module failed: %s\n",
> +                       strerror(errno));
>                 return -1;
>         }
>

Not sure making a difference between /sys/module and /sys/module/XXX
presence really helps, but this is the same philosophy as how it was done
before...
So, ok let's go with this.



> -       while (!feof(fd)) {
> -               n = fscanf(fd, "%29s %*[^\n]", mod_name);
> -               if ((n == 1) && !strcmp(mod_name, module_name)) {
> -                       ret = 1;
> -                       break;
> -               }
> +
> +       /* A module might be built-in, therefore try sysfs */
> +       snprintf(sysfs_mod_name, PATH_MAX, "/sys/module/%s", module_name);
> +       if (stat(sysfs_mod_name, &st) != 0) {
> +               RTE_LOG(DEBUG, EAL, "Open %s failed! error %i (%s)\n",
> +                       sysfs_mod_name, errno, strerror(errno));
> +               return 0;
>         }
>

Please, add a check on snprintf return value.
Even if this can't happen, if snprintf fails, stat would access a truncated
or uninitialized (when < 0) path.

With this fixed, you can add my ack.


Thanks.

-- 
David Marchand