| Message ID | 20190712112059.25558-5-erosca@de.adit-jv.com |
|---|---|
| State | Superseded |
| Delegated to: | Tom Rini |
| Headers | show |
| Series | Fixes and improvements in BCB and Android docs | expand |
Hi Eugeniu, On Fri, Jul 12, 2019 at 2:21 PM Eugeniu Rosca <erosca@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@chromium.org> > Signed-off-by: Eugeniu Rosca <erosca@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@gmail.com>
Hi Igor, On Fri, Jul 12, 2019 at 02:54:19PM +0300, Igor Opaniuk wrote: > > static int bcb_field_get(char *name, char **field, int *size) > > { > > - if (!strncmp(name, "command", sizeof("command"))) { > > - *field = bcb.command; > > + if (!strcmp(name, "command")) { > > + *fieldp = bcb.command; Many thanks for the recent reviews! There is a small issue committed by my autopilot, i.e. I didn't do the best partitioning of the patches, such that they could provoke a build breakage during git bisecting (see the intermixed usage of field and fieldp variables above). I will fix it in v2, adding your Reviewed-by in the other patches. Thanks again!
Superseded by https://patchwork.ozlabs.org/patch/1131358/
("[v2,4/5] cmd: bcb: Use strcmp() instead of strncmp() for string literals")
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;
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> --- cmd/bcb.c | 42 +++++++++++++++++++++--------------------- 1 file changed, 21 insertions(+), 21 deletions(-)