[U-Boot] [PATCH 4/5] cmd: bcb: Use strcmp() instead of strncmp() for string literals

[Igor Opaniuk]

Hi Eugeniu,

On Fri, Jul 12, 2019 at 2:21 PM Eugeniu Rosca <erosca at de.adit-jv.com> wrote:
>
> Quote from https://patchwork.ozlabs.org/patch/1104244/#2210814:
>
>  ----------8<-----------
> strncmp() is chosen for the sake of paranoid/defensive programming.
> Indeed, strncmp() is not really needed when comparing a variable
> with a string literal. We expect strcmp() to behave safely even if the
> string variable is not NUL-terminated.
>
> In the same scenario, Linux v5.2-rc7 uses both strcmp() and strncmp(),
> but the frequency of strcmp() is higher:
>
> $ git --version
> git version 2.22.0
> $ (Linux 5.2-rc7) git grep -En 'strncmp\([^"]*"[[:alnum:]]+"' | wc -l
> 1066
> $ (Linux 5.2-rc7) git grep -En 'strcmp\([^"]*"[[:alnum:]]+"' | wc -l
> 1968
>
> A quick "strcmp vs strncmp" object size test shows that strcmp()
> generates smaller memory footprint (gcc-8, x86_64):
>
> $ (U-Boot) size cmd/bcb-strncmp.o cmd/bcb-strcmp.o
>    text    data     bss     dec     hex filename
>    3373     400    2048    5821    16bd cmd/bcb-strncmp.o
>    3314     400    2048    5762    1682 cmd/bcb-strcmp.o
>
> So, overall, I agree to use strcmp() whenever variables are compared
> with string literals.
>  ----------8<-----------
>
> Fixes: db7b7a05b267 ("cmd: Add 'bcb' command to read/modify/write BCB fields")
> Reported-by: Simon Glass <sjg at chromium.org>
> Signed-off-by: Eugeniu Rosca <erosca at de.adit-jv.com>
> ---
>  cmd/bcb.c | 42 +++++++++++++++++++++---------------------
>  1 file changed, 21 insertions(+), 21 deletions(-)
>
> diff --git a/cmd/bcb.c b/cmd/bcb.c
> index 3b1c7434e287..c7138a5179a9 100644
> --- a/cmd/bcb.c
> +++ b/cmd/bcb.c
> @@ -24,17 +24,17 @@ static struct bootloader_message bcb = { { 0 } };
>
>  static int bcb_cmd_get(char *cmd)
>  {
> -       if (!strncmp(cmd, "load", sizeof("load")))
> +       if (!strcmp(cmd, "load"))
>                 return BCB_CMD_LOAD;
> -       if (!strncmp(cmd, "set", sizeof("set")))
> +       if (!strcmp(cmd, "set"))
>                 return BCB_CMD_FIELD_SET;
> -       if (!strncmp(cmd, "clear", sizeof("clear")))
> +       if (!strcmp(cmd, "clear"))
>                 return BCB_CMD_FIELD_CLEAR;
> -       if (!strncmp(cmd, "test", sizeof("test")))
> +       if (!strcmp(cmd, "test"))
>                 return BCB_CMD_FIELD_TEST;
> -       if (!strncmp(cmd, "store", sizeof("store")))
> +       if (!strcmp(cmd, "store"))
>                 return BCB_CMD_STORE;
> -       if (!strncmp(cmd, "dump", sizeof("dump")))
> +       if (!strcmp(cmd, "dump"))
>                 return BCB_CMD_FIELD_DUMP;
>         else
>                 return -1;
> @@ -85,21 +85,21 @@ err:
>
>  static int bcb_field_get(char *name, char **field, int *size)
>  {
> -       if (!strncmp(name, "command", sizeof("command"))) {
> -               *field = bcb.command;
> -               *size = sizeof(bcb.command);
> -       } else if (!strncmp(name, "status", sizeof("status"))) {
> -               *field = bcb.status;
> -               *size = sizeof(bcb.status);
> -       } else if (!strncmp(name, "recovery", sizeof("recovery"))) {
> -               *field = bcb.recovery;
> -               *size = sizeof(bcb.recovery);
> -       } else if (!strncmp(name, "stage", sizeof("stage"))) {
> -               *field = bcb.stage;
> -               *size = sizeof(bcb.stage);
> -       } else if (!strncmp(name, "reserved", sizeof("reserved"))) {
> -               *field = bcb.reserved;
> -               *size = sizeof(bcb.reserved);
> +       if (!strcmp(name, "command")) {
> +               *fieldp = bcb.command;
> +               *sizep = sizeof(bcb.command);
> +       } else if (!strcmp(name, "status")) {
> +               *fieldp = bcb.status;
> +               *sizep = sizeof(bcb.status);
> +       } else if (!strcmp(name, "recovery")) {
> +               *fieldp = bcb.recovery;
> +               *sizep = sizeof(bcb.recovery);
> +       } else if (!strcmp(name, "stage")) {
> +               *fieldp = bcb.stage;
> +               *sizep = sizeof(bcb.stage);
> +       } else if (!strcmp(name, "reserved")) {
> +               *fieldp = bcb.reserved;
> +               *sizep = sizeof(bcb.reserved);
>         } else {
>                 printf("Error: Unknown bcb field '%s'\n", name);
>                 return -1;
> --
> 2.22.0
>

Reviewed-by: Igor Opaniuk <igor.opaniuk at gmail.com>

-- 
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Igor Opaniuk

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