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@chromium.org Signed-off-by: Eugeniu Rosca erosca@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 {