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

[Sughosh Ganu]

hi Simon,

On Mon, 14 Mar 2022 at 03:53, Simon Glass <sjg at chromium.org> wrote:
>
> 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?

Again, this is not being changed by my patch. This is existing code
which is not being touched by the patch. These kinds of fixes should
be taken up separately. Thanks.

-sughosh

>
> > @@ -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