[PATCH] mmc-utils: mmc_cmds: fix type-punned warning on &ext_csd[] casting

[PATCH] mmc-utils: mmc_cmds: fix type-punned warning on &ext_csd[] casting

[Giulio Benetti]

When building with -Werror=strict-aliasing error is thrown:

mmc_cmds.c: In function 'do_ffu':
mmc_cmds.c:2972:2: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
  sect_done = htole32(*((__u32 *)&ext_csd[EXT_CSD_NUM_OF_FW_SEC_PROG_0]));
  ^
cc1: all warnings being treated as errors

Let's fix type-punned breaking strict-aliasing by memcpy() the variable.

Signed-off-by: Giulio Benetti <giulio.benetti@benettiengineering.com>
---
 mmc_cmds.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mmc_cmds.c b/mmc_cmds.c
index ae7b876..dcd60aa 100644
--- a/mmc_cmds.c
+++ b/mmc_cmds.c
@@ -2968,7 +2968,8 @@ do_retry:
 	}
 
 	/* Test if we need to restart the download */
-	sect_done = htole32(*((__u32 *)&ext_csd[EXT_CSD_NUM_OF_FW_SEC_PROG_0]));
+	memcpy(&sect_done, &ext_csd[EXT_CSD_NUM_OF_FW_SEC_PROG_0], sizeof(__u32));
+	sect_done = htole32(sect_done);
 	/* By spec, host should re-start download from the first sector if sect_done is 0 */
 	if (sect_done == 0) {
 		if (retry--) {
-- 
2.34.1

RE: [PATCH] mmc-utils: mmc_cmds: fix type-punned warning on &ext_csd[] casting

[Avri Altman]

 
> When building with -Werror=strict-aliasing error is thrown:
> 
> mmc_cmds.c: In function 'do_ffu':
> mmc_cmds.c:2972:2: error: dereferencing type-punned pointer will break strict-
> aliasing rules [-Werror=strict-aliasing]
>   sect_done = htole32(*((__u32
> *)&ext_csd[EXT_CSD_NUM_OF_FW_SEC_PROG_0]));
>   ^
> cc1: all warnings being treated as errors
> 
> Let's fix type-punned breaking strict-aliasing by memcpy() the variable.
If any, I would just revert commit a1b594ca735e.

Thanks,
Avri

> 
> Signed-off-by: Giulio Benetti <giulio.benetti@benettiengineering.com>
> ---
>  mmc_cmds.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/mmc_cmds.c b/mmc_cmds.c
> index ae7b876..dcd60aa 100644
> --- a/mmc_cmds.c
> +++ b/mmc_cmds.c
> @@ -2968,7 +2968,8 @@ do_retry:
>         }
> 
>         /* Test if we need to restart the download */
> -       sect_done = htole32(*((__u32
> *)&ext_csd[EXT_CSD_NUM_OF_FW_SEC_PROG_0]));
> +       memcpy(&sect_done, &ext_csd[EXT_CSD_NUM_OF_FW_SEC_PROG_0],
> sizeof(__u32));
> +       sect_done = htole32(sect_done);
>         /* By spec, host should re-start download from the first sector if sect_done
> is 0 */
>         if (sect_done == 0) {
>                 if (retry--) {
> --
> 2.34.1
> 

RE: [PATCH] mmc-utils: mmc_cmds: fix type-punned warning on &ext_csd[] casting

[Avri Altman]

> > When building with -Werror=strict-aliasing error is thrown:
> >
> > mmc_cmds.c: In function 'do_ffu':
> > mmc_cmds.c:2972:2: error: dereferencing type-punned pointer will break
> > strict- aliasing rules [-Werror=strict-aliasing]
> >   sect_done = htole32(*((__u32
> > *)&ext_csd[EXT_CSD_NUM_OF_FW_SEC_PROG_0]));
> >   ^
> > cc1: all warnings being treated as errors
> >
> > Let's fix type-punned breaking strict-aliasing by memcpy() the variable.
> If any, I would just revert commit a1b594ca735e.
> 
> Thanks,
> Avri
Or, how about this untested option.

Thanks,
Avri


index ae7b876..10f7532 100644
--- a/mmc_cmds.c
+++ b/mmc_cmds.c
@@ -58,6 +58,11 @@
 #define WPTYPE_PWRON 2
 #define WPTYPE_PERM 3

+static inline __u32 strict_htole32(__u8 *arr)
+{
+       return arr[0] | arr[1] << 8 | arr[2] << 16 | arr[3] << 24;
+}
+
 int read_extcsd(int fd, __u8 *ext_csd)
 {
        int ret = 0;
@@ -2807,7 +2812,7 @@ static void set_ffu_single_cmd(struct mmc_ioc_multi_cmd *multi_cmd,
                               __u8 *ext_csd, unsigned int bytes, __u8 *buf,
                               off_t offset)
 {
-       __u32 arg = htole32(*((__u32 *)&ext_csd[EXT_CSD_FFU_ARG_0]));
+       __u32 arg = safe_htole32(&ext_csd[EXT_CSD_FFU_ARG_0]);

        /* send block count */
        set_single_cmd(&multi_cmd->cmds[1], MMC_SET_BLOCK_COUNT, 0, 0,
@@ -2827,7 +2832,7 @@ static void set_ffu_single_cmd(struct mmc_ioc_multi_cmd *multi_cmd,
 int do_ffu(int nargs, char **argv)
 {
        int dev_fd, img_fd;
-       int sect_done = 0, retry = 3, ret = -EINVAL;
+       int retry = 3, ret = -EINVAL;
        unsigned int sect_size;
        __u8 ext_csd[512];
        __u8 *buf = NULL;
@@ -2835,6 +2840,7 @@ int do_ffu(int nargs, char **argv)
        char *device;
        struct mmc_ioc_multi_cmd *multi_cmd = NULL;
        unsigned int default_chunk = MMC_IOC_MAX_BYTES;
+       __u32 sect_done = 0;

        assert (nargs == 3 || nargs == 4);

@@ -2968,7 +2974,7 @@ do_retry:
        }

        /* Test if we need to restart the download */
-       sect_done = htole32(*((__u32 *)&ext_csd[EXT_CSD_NUM_OF_FW_SEC_PROG_0]));
+       sect_done = strict_htole32(&ext_csd[EXT_CSD_NUM_OF_FW_SEC_PROG_0]);
        /* By spec, host should re-start download from the first sector if sect_done is 0 */
        if (sect_done == 0) {
                if (retry--) {

[PATCH v2] mmc-utils: mmc_cmds: fix type-punned warning on &ext_csd[] casting

[Giulio Benetti]

When building with -Werror=strict-aliasing error is thrown:

mmc_cmds.c: In function 'do_ffu':
mmc_cmds.c:2972:2: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
  sect_done = htole32(*((__u32 *)&ext_csd[EXT_CSD_NUM_OF_FW_SEC_PROG_0]));
  ^
cc1: all warnings being treated as errors

Let's fix type-punned breaking strict-aliasing by implementing local
per_byte_htole32(__u8 *) and use it for the 2 present occurences of
htole32(). Let's also change sect_done type to __u32 for consistency.

Suggested-by: Avri Altman <Avri.Altman@wdc.com>
Fixes: a1b594ca735e ("mmc-utils: ffu: Simplify ext_csd bytes parsing")
Signed-off-by: Giulio Benetti <giulio.benetti@benettiengineering.com>
---
V1->V2:
* implement local per_byte_htole32() as suggested by Avril Altman
---
 mmc_cmds.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/mmc_cmds.c b/mmc_cmds.c
index ae7b876..936e0c5 100644
--- a/mmc_cmds.c
+++ b/mmc_cmds.c
@@ -58,6 +58,11 @@
 #define WPTYPE_PWRON 2
 #define WPTYPE_PERM 3
 
+static inline __u32 per_byte_htole32(__u8 *arr)
+{
+	return arr[0] | arr[1] << 8 | arr[2] << 16 | arr[3] << 24;
+}
+
 int read_extcsd(int fd, __u8 *ext_csd)
 {
 	int ret = 0;
@@ -2807,7 +2812,7 @@ static void set_ffu_single_cmd(struct mmc_ioc_multi_cmd *multi_cmd,
 			       __u8 *ext_csd, unsigned int bytes, __u8 *buf,
 			       off_t offset)
 {
-	__u32 arg = htole32(*((__u32 *)&ext_csd[EXT_CSD_FFU_ARG_0]));
+	__u32 arg = per_byte_htole32(&ext_csd[EXT_CSD_FFU_ARG_0]);
 
 	/* send block count */
 	set_single_cmd(&multi_cmd->cmds[1], MMC_SET_BLOCK_COUNT, 0, 0,
@@ -2827,7 +2832,7 @@ static void set_ffu_single_cmd(struct mmc_ioc_multi_cmd *multi_cmd,
 int do_ffu(int nargs, char **argv)
 {
 	int dev_fd, img_fd;
-	int sect_done = 0, retry = 3, ret = -EINVAL;
+	int retry = 3, ret = -EINVAL;
 	unsigned int sect_size;
 	__u8 ext_csd[512];
 	__u8 *buf = NULL;
@@ -2835,6 +2840,7 @@ int do_ffu(int nargs, char **argv)
 	char *device;
 	struct mmc_ioc_multi_cmd *multi_cmd = NULL;
 	unsigned int default_chunk = MMC_IOC_MAX_BYTES;
+	__u32 sect_done = 0;
 
 	assert (nargs == 3 || nargs == 4);
 
@@ -2968,7 +2974,7 @@ do_retry:
 	}
 
 	/* Test if we need to restart the download */
-	sect_done = htole32(*((__u32 *)&ext_csd[EXT_CSD_NUM_OF_FW_SEC_PROG_0]));
+	sect_done = per_byte_htole32(&ext_csd[EXT_CSD_NUM_OF_FW_SEC_PROG_0]);
 	/* By spec, host should re-start download from the first sector if sect_done is 0 */
 	if (sect_done == 0) {
 		if (retry--) {
-- 
2.34.1

Re: [PATCH] mmc-utils: mmc_cmds: fix type-punned warning on &ext_csd[] casting

[Giulio Benetti]

On 05/03/24 16:01, Avri Altman wrote:
>>> When building with -Werror=strict-aliasing error is thrown:
>>>
>>> mmc_cmds.c: In function 'do_ffu':
>>> mmc_cmds.c:2972:2: error: dereferencing type-punned pointer will break
>>> strict- aliasing rules [-Werror=strict-aliasing]
>>>    sect_done = htole32(*((__u32
>>> *)&ext_csd[EXT_CSD_NUM_OF_FW_SEC_PROG_0]));
>>>    ^
>>> cc1: all warnings being treated as errors
>>>
>>> Let's fix type-punned breaking strict-aliasing by memcpy() the variable.
>> If any, I would just revert commit a1b594ca735e.
>>
>> Thanks,
>> Avri
> Or, how about this untested option.

This is a good solution, just re-spin and renamed to
per_byte_htole32(__u8 *). Hope it sounds good the name to you.

Thank you
Best regards
-- 
Giulio Benetti
CEO&CTO@Benetti Engineering sas

> Thanks,
> Avri
> 
> 
> index ae7b876..10f7532 100644
> --- a/mmc_cmds.c
> +++ b/mmc_cmds.c
> @@ -58,6 +58,11 @@
>   #define WPTYPE_PWRON 2
>   #define WPTYPE_PERM 3
> 
> +static inline __u32 strict_htole32(__u8 *arr)
> +{
> +       return arr[0] | arr[1] << 8 | arr[2] << 16 | arr[3] << 24;
> +}
> +
>   int read_extcsd(int fd, __u8 *ext_csd)
>   {
>          int ret = 0;
> @@ -2807,7 +2812,7 @@ static void set_ffu_single_cmd(struct mmc_ioc_multi_cmd *multi_cmd,
>                                 __u8 *ext_csd, unsigned int bytes, __u8 *buf,
>                                 off_t offset)
>   {
> -       __u32 arg = htole32(*((__u32 *)&ext_csd[EXT_CSD_FFU_ARG_0]));
> +       __u32 arg = safe_htole32(&ext_csd[EXT_CSD_FFU_ARG_0]);
> 
>          /* send block count */
>          set_single_cmd(&multi_cmd->cmds[1], MMC_SET_BLOCK_COUNT, 0, 0,
> @@ -2827,7 +2832,7 @@ static void set_ffu_single_cmd(struct mmc_ioc_multi_cmd *multi_cmd,
>   int do_ffu(int nargs, char **argv)
>   {
>          int dev_fd, img_fd;
> -       int sect_done = 0, retry = 3, ret = -EINVAL;
> +       int retry = 3, ret = -EINVAL;
>          unsigned int sect_size;
>          __u8 ext_csd[512];
>          __u8 *buf = NULL;
> @@ -2835,6 +2840,7 @@ int do_ffu(int nargs, char **argv)
>          char *device;
>          struct mmc_ioc_multi_cmd *multi_cmd = NULL;
>          unsigned int default_chunk = MMC_IOC_MAX_BYTES;
> +       __u32 sect_done = 0;
> 
>          assert (nargs == 3 || nargs == 4);
> 
> @@ -2968,7 +2974,7 @@ do_retry:
>          }
> 
>          /* Test if we need to restart the download */
> -       sect_done = htole32(*((__u32 *)&ext_csd[EXT_CSD_NUM_OF_FW_SEC_PROG_0]));
> +       sect_done = strict_htole32(&ext_csd[EXT_CSD_NUM_OF_FW_SEC_PROG_0]);
>          /* By spec, host should re-start download from the first sector if sect_done is 0 */
>          if (sect_done == 0) {
>                  if (retry--) {

RE: [PATCH v2] mmc-utils: mmc_cmds: fix type-punned warning on &ext_csd[] casting

[Avri Altman]

> When building with -Werror=strict-aliasing error is thrown:
> 
> mmc_cmds.c: In function 'do_ffu':
> mmc_cmds.c:2972:2: error: dereferencing type-punned pointer will break strict-
> aliasing rules [-Werror=strict-aliasing]
>   sect_done = htole32(*((__u32
> *)&ext_csd[EXT_CSD_NUM_OF_FW_SEC_PROG_0]));
>   ^
> cc1: all warnings being treated as errors
> 
> Let's fix type-punned breaking strict-aliasing by implementing local
> per_byte_htole32(__u8 *) and use it for the 2 present occurences of
> htole32(). Let's also change sect_done type to __u32 for consistency.
> 
> Suggested-by: Avri Altman <Avri.Altman@wdc.com>
> Fixes: a1b594ca735e ("mmc-utils: ffu: Simplify ext_csd bytes parsing")
> Signed-off-by: Giulio Benetti <giulio.benetti@benettiengineering.com>
Reviewed-by: Avri Altman <avri.altman@wdc.com>


> ---
> V1->V2:
> * implement local per_byte_htole32() as suggested by Avril Altman
> ---
>  mmc_cmds.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/mmc_cmds.c b/mmc_cmds.c
> index ae7b876..936e0c5 100644
> --- a/mmc_cmds.c
> +++ b/mmc_cmds.c
> @@ -58,6 +58,11 @@
>  #define WPTYPE_PWRON 2
>  #define WPTYPE_PERM 3
> 
> +static inline __u32 per_byte_htole32(__u8 *arr)
> +{
> +       return arr[0] | arr[1] << 8 | arr[2] << 16 | arr[3] << 24;
> +}
> +
>  int read_extcsd(int fd, __u8 *ext_csd)
>  {
>         int ret = 0;
> @@ -2807,7 +2812,7 @@ static void set_ffu_single_cmd(struct
> mmc_ioc_multi_cmd *multi_cmd,
>                                __u8 *ext_csd, unsigned int bytes, __u8 *buf,
>                                off_t offset)
>  {
> -       __u32 arg = htole32(*((__u32 *)&ext_csd[EXT_CSD_FFU_ARG_0]));
> +       __u32 arg = per_byte_htole32(&ext_csd[EXT_CSD_FFU_ARG_0]);
> 
>         /* send block count */
>         set_single_cmd(&multi_cmd->cmds[1], MMC_SET_BLOCK_COUNT, 0, 0,
> @@ -2827,7 +2832,7 @@ static void set_ffu_single_cmd(struct
> mmc_ioc_multi_cmd *multi_cmd,
>  int do_ffu(int nargs, char **argv)
>  {
>         int dev_fd, img_fd;
> -       int sect_done = 0, retry = 3, ret = -EINVAL;
> +       int retry = 3, ret = -EINVAL;
>         unsigned int sect_size;
>         __u8 ext_csd[512];
>         __u8 *buf = NULL;
> @@ -2835,6 +2840,7 @@ int do_ffu(int nargs, char **argv)
>         char *device;
>         struct mmc_ioc_multi_cmd *multi_cmd = NULL;
>         unsigned int default_chunk = MMC_IOC_MAX_BYTES;
> +       __u32 sect_done = 0;
> 
>         assert (nargs == 3 || nargs == 4);
> 
> @@ -2968,7 +2974,7 @@ do_retry:
>         }
> 
>         /* Test if we need to restart the download */
> -       sect_done = htole32(*((__u32
> *)&ext_csd[EXT_CSD_NUM_OF_FW_SEC_PROG_0]));
> +       sect_done =
> per_byte_htole32(&ext_csd[EXT_CSD_NUM_OF_FW_SEC_PROG_0]);
>         /* By spec, host should re-start download from the first sector if sect_done
> is 0 */
>         if (sect_done == 0) {
>                 if (retry--) {
> --
> 2.34.1

Re: [PATCH v2] mmc-utils: mmc_cmds: fix type-punned warning on &ext_csd[] casting

[Ulf Hansson]

On Tue, 5 Mar 2024 at 19:52, Giulio Benetti
<giulio.benetti@benettiengineering.com> wrote:
>
> When building with -Werror=strict-aliasing error is thrown:
>
> mmc_cmds.c: In function 'do_ffu':
> mmc_cmds.c:2972:2: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
>   sect_done = htole32(*((__u32 *)&ext_csd[EXT_CSD_NUM_OF_FW_SEC_PROG_0]));
>   ^
> cc1: all warnings being treated as errors
>
> Let's fix type-punned breaking strict-aliasing by implementing local
> per_byte_htole32(__u8 *) and use it for the 2 present occurences of
> htole32(). Let's also change sect_done type to __u32 for consistency.
>
> Suggested-by: Avri Altman <Avri.Altman@wdc.com>
> Fixes: a1b594ca735e ("mmc-utils: ffu: Simplify ext_csd bytes parsing")
> Signed-off-by: Giulio Benetti <giulio.benetti@benettiengineering.com>

Applied to git.kernel.org/pub/scm/utils/mmc/mmc-utils.git master, thanks!

Kind regards
Uffe

> ---
> V1->V2:
> * implement local per_byte_htole32() as suggested by Avril Altman
> ---
>  mmc_cmds.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/mmc_cmds.c b/mmc_cmds.c
> index ae7b876..936e0c5 100644
> --- a/mmc_cmds.c
> +++ b/mmc_cmds.c
> @@ -58,6 +58,11 @@
>  #define WPTYPE_PWRON 2
>  #define WPTYPE_PERM 3
>
> +static inline __u32 per_byte_htole32(__u8 *arr)
> +{
> +       return arr[0] | arr[1] << 8 | arr[2] << 16 | arr[3] << 24;
> +}
> +
>  int read_extcsd(int fd, __u8 *ext_csd)
>  {
>         int ret = 0;
> @@ -2807,7 +2812,7 @@ static void set_ffu_single_cmd(struct mmc_ioc_multi_cmd *multi_cmd,
>                                __u8 *ext_csd, unsigned int bytes, __u8 *buf,
>                                off_t offset)
>  {
> -       __u32 arg = htole32(*((__u32 *)&ext_csd[EXT_CSD_FFU_ARG_0]));
> +       __u32 arg = per_byte_htole32(&ext_csd[EXT_CSD_FFU_ARG_0]);
>
>         /* send block count */
>         set_single_cmd(&multi_cmd->cmds[1], MMC_SET_BLOCK_COUNT, 0, 0,
> @@ -2827,7 +2832,7 @@ static void set_ffu_single_cmd(struct mmc_ioc_multi_cmd *multi_cmd,
>  int do_ffu(int nargs, char **argv)
>  {
>         int dev_fd, img_fd;
> -       int sect_done = 0, retry = 3, ret = -EINVAL;
> +       int retry = 3, ret = -EINVAL;
>         unsigned int sect_size;
>         __u8 ext_csd[512];
>         __u8 *buf = NULL;
> @@ -2835,6 +2840,7 @@ int do_ffu(int nargs, char **argv)
>         char *device;
>         struct mmc_ioc_multi_cmd *multi_cmd = NULL;
>         unsigned int default_chunk = MMC_IOC_MAX_BYTES;
> +       __u32 sect_done = 0;
>
>         assert (nargs == 3 || nargs == 4);
>
> @@ -2968,7 +2974,7 @@ do_retry:
>         }
>
>         /* Test if we need to restart the download */
> -       sect_done = htole32(*((__u32 *)&ext_csd[EXT_CSD_NUM_OF_FW_SEC_PROG_0]));
> +       sect_done = per_byte_htole32(&ext_csd[EXT_CSD_NUM_OF_FW_SEC_PROG_0]);
>         /* By spec, host should re-start download from the first sector if sect_done is 0 */
>         if (sect_done == 0) {
>                 if (retry--) {
> --
> 2.34.1
>
>