[PATCH v5 7/9] cmd: rng: Use a statically allocated array for random bytes

[Simon Glass]

Hi Sughosh,

On Sun, 13 Mar 2022 at 08:49, Sughosh Ganu <sughosh.ganu at linaro.org> wrote:
>
> Use a statically allocated buffer on stack instead of using malloc for
> reading the random bytes. Using a local array is faster than
> allocating heap memory on every initiation of the command.
>
> Signed-off-by: Sughosh Ganu <sughosh.ganu at linaro.org>
> ---
>
> Changes since V4:
>
> * New patch based on review comments from Simon to not use the malloc
>   call
>
>  cmd/rng.c | 17 +++++++----------
>  1 file changed, 7 insertions(+), 10 deletions(-)

It might be easier to put this patch before the other one.

>
> diff --git a/cmd/rng.c b/cmd/rng.c
> index 2ddf27545f..81a23964b8 100644
> --- a/cmd/rng.c
> +++ b/cmd/rng.c
> @@ -14,9 +14,9 @@
>  static int do_rng(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
>  {
>         size_t n;
> -       struct udevice *dev;
> -       void *buf;
> +       u8 buf[64];
>         int devnum;
> +       struct udevice *dev;
>         int ret = CMD_RET_SUCCESS;
>
>         switch (argc) {
> @@ -41,11 +41,10 @@ static int do_rng(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
>                 return CMD_RET_FAILURE;
>         }
>
> -       buf = malloc(n);
> -       if (!buf) {
> -               printf("Out of memory\n");
> -               return CMD_RET_FAILURE;
> -       }
> +       if (!n)
> +               return 0;
> +
> +       n = min(n, sizeof(buf));
>
>         if (dm_rng_read(dev, buf, n)) {
>                 printf("Reading RNG failed\n");

This looks like a Windows-style error. How about adding "(err=%d)",
ret to this so we can see the error?

> @@ -54,15 +53,13 @@ static int do_rng(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
>                 print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, buf, n);
>         }
>
> -       free(buf);
> -
>         return ret;
>  }
>
>  #ifdef CONFIG_SYS_LONGHELP
>  static char rng_help_text[] =
>         "[dev [n]]\n"
> -       "  - print n random bytes read from dev\n";
> +       "  - print n random bytes(max 64) read from dev\n";
>  #endif
>
>  U_BOOT_CMD(
> --
> 2.25.1
>

Regards,
SImon