[U-Boot] [PATCH v2 4/5] cmd: bcb: Use strcmp() instead of strncmp() for string literals

[Eugeniu Rosca]

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>
---
v2:
 - Fixed accidental rename of field/size variables in bcb_field_get()

v1:
 - https://patchwork.ozlabs.org/patch/1131306/
---
 cmd/bcb.c | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/cmd/bcb.c b/cmd/bcb.c
index 3b1c7434e287..fa9fdeeb0dfc 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;
@@ -85,19 +85,19 @@ err:
 
 static int bcb_field_get(char *name, char **field, int *size)
 {
-	if (!strncmp(name, "command", sizeof("command"))) {
+	if (!strcmp(name, "command")) {
 		*field = bcb.command;
 		*size = sizeof(bcb.command);
-	} else if (!strncmp(name, "status", sizeof("status"))) {
+	} else if (!strcmp(name, "status")) {
 		*field = bcb.status;
 		*size = sizeof(bcb.status);
-	} else if (!strncmp(name, "recovery", sizeof("recovery"))) {
+	} else if (!strcmp(name, "recovery")) {
 		*field = bcb.recovery;
 		*size = sizeof(bcb.recovery);
-	} else if (!strncmp(name, "stage", sizeof("stage"))) {
+	} else if (!strcmp(name, "stage")) {
 		*field = bcb.stage;
 		*size = sizeof(bcb.stage);
-	} else if (!strncmp(name, "reserved", sizeof("reserved"))) {
+	} else if (!strcmp(name, "reserved")) {
 		*field = bcb.reserved;
 		*size = sizeof(bcb.reserved);
 	} else {
-- 
2.22.0