Re: [PATCH v1 1/8] lib/uuid: Introduce uuid_{be|le}_cmp_p{p}() helpers

[Lukas Wunner]

> New helpers take pointers to uuid_{be|le} as parameters.
> 
> When using them on a raw data we don't need to do an ugly dereference and,
> in some cases, a type casting.
> 
> Cc: Andrew Morton 
> Cc: Arnd Bergmann 
> Cc: Liam Girdwood 
> Cc: Mark Brown 
> Cc: Vinod Koul 
> Cc: Srinivas Pandruvada 
> Cc: Benjamin Tissoires 
> Cc: Kirti Wankhede 
> Cc: Alex Williamson 
> Cc: "K. Y. Srinivasan" 
> Cc: Haiyang Zhang 
> Cc: Stephen Hemminger 
> Cc: Tomas Winkler 
> Cc: Matt Fleming 
> Cc: Ard Biesheuvel 
> Cc: "Rafael J. Wysocki" 
> 
> Signed-off-by: Andy Shevchenko 
> ---
>  include/linux/uuid.h | 20 
>  1 file changed, 20 insertions(+)
> 
> diff --git a/include/linux/uuid.h b/include/linux/uuid.h index
> 4dff73a89758..45312cb5ac65 100644
> --- a/include/linux/uuid.h
> +++ b/include/linux/uuid.h
> @@ -58,6 +58,26 @@ static inline int uuid_be_cmp(const uuid_be u1, const
> uuid_be u2)
>   return memcmp(, , sizeof(uuid_be));  }
> 
> +static inline int uuid_le_cmp_p(const uuid_le *pu1, const uuid_le u2) {
> + return memcmp(pu1, , sizeof(uuid_le)); }
> +
> +static inline int uuid_be_cmp_p(const uuid_be *pu1, const uuid_be u2) {
> + return memcmp(pu1, , sizeof(uuid_be)); }
> +
> +static inline int uuid_le_cmp_pp(const uuid_le *pu1, const uuid_le
> +*pu2) {
> + return memcmp(pu1, pu2, sizeof(uuid_le)); }
> +
> +static inline int uuid_be_cmp_pp(const uuid_be *pu1, const uuid_be
> +*pu2) {
> + return memcmp(pu1, pu2, sizeof(uuid_be)); }
> +
>  void generate_random_uuid(unsigned char uuid[16]);
> 
>  extern void uuid_le_gen(uuid_le *u);

There's a bug in gcc wherein constant compound literals are generated
on the stack at runtime, rather than stored in rodata.  The bug occurs
if the compound literal is passed by reference.  It does not manifest
itself when passing by value:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68725

Hence this patch is unfortunately counterproductive if the UUIDs are
declared const.

FWIW I've posted a series back in January to constify UUIDs as much as
possible, but I got some objections and lacked the time so far to
address them.  In fact I'm thinking that gcc needs to be fixed first,
then we can focus on improving the kernel side of things:

https://www.spinics.net/lists/linux-efi/msg10093.html

Best regards,

Lukas

Re: [PATCH v1 1/8] lib/uuid: Introduce uuid_{be|le}_cmp_p{p}() helpers

[Lukas Wunner]

> New helpers take pointers to uuid_{be|le} as parameters.
> 
> When using them on a raw data we don't need to do an ugly dereference and,
> in some cases, a type casting.
> 
> Cc: Andrew Morton 
> Cc: Arnd Bergmann 
> Cc: Liam Girdwood 
> Cc: Mark Brown 
> Cc: Vinod Koul 
> Cc: Srinivas Pandruvada 
> Cc: Benjamin Tissoires 
> Cc: Kirti Wankhede 
> Cc: Alex Williamson 
> Cc: "K. Y. Srinivasan" 
> Cc: Haiyang Zhang 
> Cc: Stephen Hemminger 
> Cc: Tomas Winkler 
> Cc: Matt Fleming 
> Cc: Ard Biesheuvel 
> Cc: "Rafael J. Wysocki" 
> 
> Signed-off-by: Andy Shevchenko 
> ---
>  include/linux/uuid.h | 20 
>  1 file changed, 20 insertions(+)
> 
> diff --git a/include/linux/uuid.h b/include/linux/uuid.h index
> 4dff73a89758..45312cb5ac65 100644
> --- a/include/linux/uuid.h
> +++ b/include/linux/uuid.h
> @@ -58,6 +58,26 @@ static inline int uuid_be_cmp(const uuid_be u1, const
> uuid_be u2)
>   return memcmp(, , sizeof(uuid_be));  }
> 
> +static inline int uuid_le_cmp_p(const uuid_le *pu1, const uuid_le u2) {
> + return memcmp(pu1, , sizeof(uuid_le)); }
> +
> +static inline int uuid_be_cmp_p(const uuid_be *pu1, const uuid_be u2) {
> + return memcmp(pu1, , sizeof(uuid_be)); }
> +
> +static inline int uuid_le_cmp_pp(const uuid_le *pu1, const uuid_le
> +*pu2) {
> + return memcmp(pu1, pu2, sizeof(uuid_le)); }
> +
> +static inline int uuid_be_cmp_pp(const uuid_be *pu1, const uuid_be
> +*pu2) {
> + return memcmp(pu1, pu2, sizeof(uuid_be)); }
> +
>  void generate_random_uuid(unsigned char uuid[16]);
> 
>  extern void uuid_le_gen(uuid_le *u);

There's a bug in gcc wherein constant compound literals are generated
on the stack at runtime, rather than stored in rodata.  The bug occurs
if the compound literal is passed by reference.  It does not manifest
itself when passing by value:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68725

Hence this patch is unfortunately counterproductive if the UUIDs are
declared const.

FWIW I've posted a series back in January to constify UUIDs as much as
possible, but I got some objections and lacked the time so far to
address them.  In fact I'm thinking that gcc needs to be fixed first,
then we can focus on improving the kernel side of things:

https://www.spinics.net/lists/linux-efi/msg10093.html

Best regards,

Lukas

Re: [PATCH v1 1/8] lib/uuid: Introduce uuid_{be|le}_cmp_p{p}() helpers

[Andy Shevchenko]

On Sun, 2017-04-23 at 20:20 +, Winkler, Tomas wrote:
> On Sun, 2017-04-23 at 15:42 +0300, Andy Shevchenko wrote:
> > On Sun, Apr 23, 2017 at 1:29 PM, Winkler, Tomas  > .
> > com> wrote:
> > > > New helpers take pointers to uuid_{be|le} as parameters.
> > > > 
> > > > When using them on a raw data we don't need to do an ugly
> > > > dereference and,
> > > > in some cases, a type casting.
> > > 
> > > I think this going overboard, the _pp types  are just enough.
> > 
> > I looked at existing users and there are cases like
> > #define XXX_UUID UUID_...(a, b, c, ...)
> > 
> > uuid_.*_cmp(value, XXX_UUID)
> > 
> > For _pp variant if would be _cmp_pp(value, _UUID) which is
> > slightly worse than for _p variant.
> 
> 
> Maybe it's worth to actually replace the defines with variables than
> to
> create an interface with all the permutations.

Maybe. I didn't estimate the number of users that would be in a scope.

-- 
Andy Shevchenko 
Intel Finland Oy

Re: [PATCH v1 1/8] lib/uuid: Introduce uuid_{be|le}_cmp_p{p}() helpers

[Andy Shevchenko]

On Sun, 2017-04-23 at 20:20 +, Winkler, Tomas wrote:
> On Sun, 2017-04-23 at 15:42 +0300, Andy Shevchenko wrote:
> > On Sun, Apr 23, 2017 at 1:29 PM, Winkler, Tomas  > .
> > com> wrote:
> > > > New helpers take pointers to uuid_{be|le} as parameters.
> > > > 
> > > > When using them on a raw data we don't need to do an ugly
> > > > dereference and,
> > > > in some cases, a type casting.
> > > 
> > > I think this going overboard, the _pp types  are just enough.
> > 
> > I looked at existing users and there are cases like
> > #define XXX_UUID UUID_...(a, b, c, ...)
> > 
> > uuid_.*_cmp(value, XXX_UUID)
> > 
> > For _pp variant if would be _cmp_pp(value, _UUID) which is
> > slightly worse than for _p variant.
> 
> 
> Maybe it's worth to actually replace the defines with variables than
> to
> create an interface with all the permutations.

Maybe. I didn't estimate the number of users that would be in a scope.

-- 
Andy Shevchenko 
Intel Finland Oy

Re: [PATCH v1 1/8] lib/uuid: Introduce uuid_{be|le}_cmp_p{p}() helpers

[Winkler, Tomas]

On Sun, 2017-04-23 at 15:42 +0300, Andy Shevchenko wrote:
> On Sun, Apr 23, 2017 at 1:29 PM, Winkler, Tomas  com> wrote:
> > > New helpers take pointers to uuid_{be|le} as parameters.
> > > 
> > > When using them on a raw data we don't need to do an ugly
> > > dereference and,
> > > in some cases, a type casting.
> > I think this going overboard, the _pp types  are just enough.
> 
> I looked at existing users and there are cases like
> #define XXX_UUID UUID_...(a, b, c, ...)
> 
> uuid_.*_cmp(value, XXX_UUID)
> 
> For _pp variant if would be _cmp_pp(value, _UUID) which is
> slightly worse than for _p variant.


Maybe it's worth to actually replace the defines with variables than to
create an interface with all the permutations.

Tomas

Re: [PATCH v1 1/8] lib/uuid: Introduce uuid_{be|le}_cmp_p{p}() helpers

[Winkler, Tomas]

On Sun, 2017-04-23 at 15:42 +0300, Andy Shevchenko wrote:
> On Sun, Apr 23, 2017 at 1:29 PM, Winkler, Tomas  com> wrote:
> > > New helpers take pointers to uuid_{be|le} as parameters.
> > > 
> > > When using them on a raw data we don't need to do an ugly
> > > dereference and,
> > > in some cases, a type casting.
> > I think this going overboard, the _pp types  are just enough.
> 
> I looked at existing users and there are cases like
> #define XXX_UUID UUID_...(a, b, c, ...)
> 
> uuid_.*_cmp(value, XXX_UUID)
> 
> For _pp variant if would be _cmp_pp(value, _UUID) which is
> slightly worse than for _p variant.


Maybe it's worth to actually replace the defines with variables than to
create an interface with all the permutations.

Tomas

Re: [PATCH v1 1/8] lib/uuid: Introduce uuid_{be|le}_cmp_p{p}() helpers

[Andy Shevchenko]

On Sun, Apr 23, 2017 at 1:29 PM, Winkler, Tomas  wrote:
>> New helpers take pointers to uuid_{be|le} as parameters.
>>
>> When using them on a raw data we don't need to do an ugly dereference and,
>> in some cases, a type casting.

> I think this going overboard, the _pp types  are just enough.
I looked at existing users and there are cases like
#define XXX_UUID UUID_...(a, b, c, ...)

uuid_.*_cmp(value, XXX_UUID)

For _pp variant if would be _cmp_pp(value, _UUID) which is
slightly worse than for _p variant.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v1 1/8] lib/uuid: Introduce uuid_{be|le}_cmp_p{p}() helpers

[Andy Shevchenko]

On Sun, Apr 23, 2017 at 1:29 PM, Winkler, Tomas  wrote:
>> New helpers take pointers to uuid_{be|le} as parameters.
>>
>> When using them on a raw data we don't need to do an ugly dereference and,
>> in some cases, a type casting.

> I think this going overboard, the _pp types  are just enough.
I looked at existing users and there are cases like
#define XXX_UUID UUID_...(a, b, c, ...)

uuid_.*_cmp(value, XXX_UUID)

For _pp variant if would be _cmp_pp(value, _UUID) which is
slightly worse than for _p variant.

-- 
With Best Regards,
Andy Shevchenko

RE: [PATCH v1 1/8] lib/uuid: Introduce uuid_{be|le}_cmp_p{p}() helpers

[Winkler, Tomas]

> New helpers take pointers to uuid_{be|le} as parameters.
> 
> When using them on a raw data we don't need to do an ugly dereference and,
> in some cases, a type casting.
> 
> Cc: Andrew Morton 
> Cc: Arnd Bergmann 
> Cc: Liam Girdwood 
> Cc: Mark Brown 
> Cc: Vinod Koul 
> Cc: Srinivas Pandruvada 
> Cc: Benjamin Tissoires 
> Cc: Kirti Wankhede 
> Cc: Alex Williamson 
> Cc: "K. Y. Srinivasan" 
> Cc: Haiyang Zhang 
> Cc: Stephen Hemminger 
> Cc: Tomas Winkler 
> Cc: Matt Fleming 
> Cc: Ard Biesheuvel 
> Cc: "Rafael J. Wysocki" 
> 
> Signed-off-by: Andy Shevchenko 
> ---
>  include/linux/uuid.h | 20 
>  1 file changed, 20 insertions(+)
> 
> diff --git a/include/linux/uuid.h b/include/linux/uuid.h index
> 4dff73a89758..45312cb5ac65 100644
> --- a/include/linux/uuid.h
> +++ b/include/linux/uuid.h
> @@ -58,6 +58,26 @@ static inline int uuid_be_cmp(const uuid_be u1, const
> uuid_be u2)
>   return memcmp(, , sizeof(uuid_be));  }
> 
> +static inline int uuid_le_cmp_p(const uuid_le *pu1, const uuid_le u2) {
> + return memcmp(pu1, , sizeof(uuid_le)); }
> +
> +static inline int uuid_be_cmp_p(const uuid_be *pu1, const uuid_be u2) {
> + return memcmp(pu1, , sizeof(uuid_be)); }
> +
> +static inline int uuid_le_cmp_pp(const uuid_le *pu1, const uuid_le
> +*pu2) {
> + return memcmp(pu1, pu2, sizeof(uuid_le)); }
> +
> +static inline int uuid_be_cmp_pp(const uuid_be *pu1, const uuid_be
> +*pu2) {
> + return memcmp(pu1, pu2, sizeof(uuid_be)); }
> +
>  void generate_random_uuid(unsigned char uuid[16]);
> 
>  extern void uuid_le_gen(uuid_le *u);

I think this going overboard, the _pp types  are just enough. 
Tomas

RE: [PATCH v1 1/8] lib/uuid: Introduce uuid_{be|le}_cmp_p{p}() helpers

[Winkler, Tomas]

> New helpers take pointers to uuid_{be|le} as parameters.
> 
> When using them on a raw data we don't need to do an ugly dereference and,
> in some cases, a type casting.
> 
> Cc: Andrew Morton 
> Cc: Arnd Bergmann 
> Cc: Liam Girdwood 
> Cc: Mark Brown 
> Cc: Vinod Koul 
> Cc: Srinivas Pandruvada 
> Cc: Benjamin Tissoires 
> Cc: Kirti Wankhede 
> Cc: Alex Williamson 
> Cc: "K. Y. Srinivasan" 
> Cc: Haiyang Zhang 
> Cc: Stephen Hemminger 
> Cc: Tomas Winkler 
> Cc: Matt Fleming 
> Cc: Ard Biesheuvel 
> Cc: "Rafael J. Wysocki" 
> 
> Signed-off-by: Andy Shevchenko 
> ---
>  include/linux/uuid.h | 20 
>  1 file changed, 20 insertions(+)
> 
> diff --git a/include/linux/uuid.h b/include/linux/uuid.h index
> 4dff73a89758..45312cb5ac65 100644
> --- a/include/linux/uuid.h
> +++ b/include/linux/uuid.h
> @@ -58,6 +58,26 @@ static inline int uuid_be_cmp(const uuid_be u1, const
> uuid_be u2)
>   return memcmp(, , sizeof(uuid_be));  }
> 
> +static inline int uuid_le_cmp_p(const uuid_le *pu1, const uuid_le u2) {
> + return memcmp(pu1, , sizeof(uuid_le)); }
> +
> +static inline int uuid_be_cmp_p(const uuid_be *pu1, const uuid_be u2) {
> + return memcmp(pu1, , sizeof(uuid_be)); }
> +
> +static inline int uuid_le_cmp_pp(const uuid_le *pu1, const uuid_le
> +*pu2) {
> + return memcmp(pu1, pu2, sizeof(uuid_le)); }
> +
> +static inline int uuid_be_cmp_pp(const uuid_be *pu1, const uuid_be
> +*pu2) {
> + return memcmp(pu1, pu2, sizeof(uuid_be)); }
> +
>  void generate_random_uuid(unsigned char uuid[16]);
> 
>  extern void uuid_le_gen(uuid_le *u);

I think this going overboard, the _pp types  are just enough. 
Tomas

[PATCH v1 1/8] lib/uuid: Introduce uuid_{be|le}_cmp_p{p}() helpers

[Andy Shevchenko]

New helpers take pointers to uuid_{be|le} as parameters.

When using them on a raw data we don't need to do an ugly dereference
and, in some cases, a type casting.

Cc: Andrew Morton 
Cc: Arnd Bergmann 
Cc: Liam Girdwood 
Cc: Mark Brown 
Cc: Vinod Koul 
Cc: Srinivas Pandruvada 
Cc: Benjamin Tissoires 
Cc: Kirti Wankhede 
Cc: Alex Williamson 
Cc: "K. Y. Srinivasan" 
Cc: Haiyang Zhang 
Cc: Stephen Hemminger 
Cc: Tomas Winkler 
Cc: Matt Fleming 
Cc: Ard Biesheuvel 
Cc: "Rafael J. Wysocki" 

Signed-off-by: Andy Shevchenko 
---
 include/linux/uuid.h | 20 
 1 file changed, 20 insertions(+)

diff --git a/include/linux/uuid.h b/include/linux/uuid.h
index 4dff73a89758..45312cb5ac65 100644
--- a/include/linux/uuid.h
+++ b/include/linux/uuid.h
@@ -58,6 +58,26 @@ static inline int uuid_be_cmp(const uuid_be u1, const 
uuid_be u2)
return memcmp(, , sizeof(uuid_be));
 }
 
+static inline int uuid_le_cmp_p(const uuid_le *pu1, const uuid_le u2)
+{
+   return memcmp(pu1, , sizeof(uuid_le));
+}
+
+static inline int uuid_be_cmp_p(const uuid_be *pu1, const uuid_be u2)
+{
+   return memcmp(pu1, , sizeof(uuid_be));
+}
+
+static inline int uuid_le_cmp_pp(const uuid_le *pu1, const uuid_le *pu2)
+{
+   return memcmp(pu1, pu2, sizeof(uuid_le));
+}
+
+static inline int uuid_be_cmp_pp(const uuid_be *pu1, const uuid_be *pu2)
+{
+   return memcmp(pu1, pu2, sizeof(uuid_be));
+}
+
 void generate_random_uuid(unsigned char uuid[16]);
 
 extern void uuid_le_gen(uuid_le *u);
-- 
2.11.0

[PATCH v1 1/8] lib/uuid: Introduce uuid_{be|le}_cmp_p{p}() helpers

[Andy Shevchenko]

New helpers take pointers to uuid_{be|le} as parameters.

When using them on a raw data we don't need to do an ugly dereference
and, in some cases, a type casting.

Cc: Andrew Morton 
Cc: Arnd Bergmann 
Cc: Liam Girdwood 
Cc: Mark Brown 
Cc: Vinod Koul 
Cc: Srinivas Pandruvada 
Cc: Benjamin Tissoires 
Cc: Kirti Wankhede 
Cc: Alex Williamson 
Cc: "K. Y. Srinivasan" 
Cc: Haiyang Zhang 
Cc: Stephen Hemminger 
Cc: Tomas Winkler 
Cc: Matt Fleming 
Cc: Ard Biesheuvel 
Cc: "Rafael J. Wysocki" 

Signed-off-by: Andy Shevchenko 
---
 include/linux/uuid.h | 20 
 1 file changed, 20 insertions(+)

diff --git a/include/linux/uuid.h b/include/linux/uuid.h
index 4dff73a89758..45312cb5ac65 100644
--- a/include/linux/uuid.h
+++ b/include/linux/uuid.h
@@ -58,6 +58,26 @@ static inline int uuid_be_cmp(const uuid_be u1, const 
uuid_be u2)
return memcmp(, , sizeof(uuid_be));
 }
 
+static inline int uuid_le_cmp_p(const uuid_le *pu1, const uuid_le u2)
+{
+   return memcmp(pu1, , sizeof(uuid_le));
+}
+
+static inline int uuid_be_cmp_p(const uuid_be *pu1, const uuid_be u2)
+{
+   return memcmp(pu1, , sizeof(uuid_be));
+}
+
+static inline int uuid_le_cmp_pp(const uuid_le *pu1, const uuid_le *pu2)
+{
+   return memcmp(pu1, pu2, sizeof(uuid_le));
+}
+
+static inline int uuid_be_cmp_pp(const uuid_be *pu1, const uuid_be *pu2)
+{
+   return memcmp(pu1, pu2, sizeof(uuid_be));
+}
+
 void generate_random_uuid(unsigned char uuid[16]);
 
 extern void uuid_le_gen(uuid_le *u);
-- 
2.11.0