[PATCH] MIPS: use 32-bit wrapper for compat_sys_futex

[PATCH] MIPS: use 32-bit wrapper for compat_sys_futex

[Yong Zhang]

We can't trust in the caller(userspace) to give signed-extend
parameter, thus futex-wait may fail in some special case.

For example, if 'val' is too big and bit-31 is 1,
the caller may enter endless loop at:
futex_wait_setup()
{
	...

	if (uval != val) {
		queue_unlock(q, *hb);
		ret = -EWOULDBLOCK;

	...
}

Below assembler code will make it more easy to understand how
the patch take effect :)

Dump of assembler code for function SyS_32_futex:
   0xffffffff811b6fe8 <+0>:	sll	a1,a1,0x0
   0xffffffff811b6fec <+4>:	sll	a2,a2,0x0
   0xffffffff811b6ff0 <+8>:	j	0xffffffff8121a240 <compat_sys_futex>
   0xffffffff811b6ff4 <+12>:	sll	a5,a5,0x0

Signed-off-by: Yong Zhang <yong.zhang@windriver.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
---
 arch/mips/kernel/linux32.c     |    7 +++++++
 arch/mips/kernel/scall64-n32.S |    2 +-
 arch/mips/kernel/scall64-o32.S |    2 +-
 3 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/mips/kernel/linux32.c b/arch/mips/kernel/linux32.c
index 876a75c..922a554 100644
--- a/arch/mips/kernel/linux32.c
+++ b/arch/mips/kernel/linux32.c
@@ -349,3 +349,10 @@ SYSCALL_DEFINE6(32_fanotify_mark, int, fanotify_fd, unsigned int, flags,
 	return sys_fanotify_mark(fanotify_fd, flags, merge_64(a3, a4),
 				 dfd, pathname);
 }
+
+SYSCALL_DEFINE6(32_futex, u32 __user *, uaddr, int, op, u32, val,
+		struct compat_timespec __user *, utime, u32 __user *, uaddr2,
+		u32, val3)
+{
+	return compat_sys_futex(uaddr, op, val, utime, uaddr2, val3);
+}
diff --git a/arch/mips/kernel/scall64-n32.S b/arch/mips/kernel/scall64-n32.S
index b85842f..c956cc9 100644
--- a/arch/mips/kernel/scall64-n32.S
+++ b/arch/mips/kernel/scall64-n32.S
@@ -315,7 +315,7 @@ EXPORT(sysn32_call_table)
 	PTR	sys_fremovexattr
 	PTR	sys_tkill
 	PTR	sys_ni_syscall
-	PTR	compat_sys_futex
+	PTR	sys_32_futex
 	PTR	compat_sys_sched_setaffinity	/* 6195 */
 	PTR	compat_sys_sched_getaffinity
 	PTR	sys_cacheflush
diff --git a/arch/mips/kernel/scall64-o32.S b/arch/mips/kernel/scall64-o32.S
index 46c4763..f48b18e 100644
--- a/arch/mips/kernel/scall64-o32.S
+++ b/arch/mips/kernel/scall64-o32.S
@@ -441,7 +441,7 @@ sys_call_table:
 	PTR	sys_fremovexattr		/* 4235 */
 	PTR	sys_tkill
 	PTR	sys_sendfile64
-	PTR	compat_sys_futex
+	PTR	sys_32_futex
 	PTR	compat_sys_sched_setaffinity
 	PTR	compat_sys_sched_getaffinity	/* 4240 */
 	PTR	compat_sys_io_setup
-- 
1.7.4.1

Re: [PATCH] MIPS: use 32-bit wrapper for compat_sys_futex

[Ralf Baechle]

Applied.  Thanks Yong!

  Ralf

Re: [PATCH] MIPS: use 32-bit wrapper for compat_sys_futex

[David Daney]

On 08/16/2011 06:54 PM, Yong Zhang wrote:
> We can't trust in the caller(userspace) to give signed-extend
> parameter, thus futex-wait may fail in some special case.
>
> For example, if 'val' is too big and bit-31 is 1,
> the caller may enter endless loop at:
> futex_wait_setup()
> {
> 	...
>
> 	if (uval != val) {
> 		queue_unlock(q, *hb);
> 		ret = -EWOULDBLOCK;
>
> 	...
> }
>
> Below assembler code will make it more easy to understand how
> the patch take effect :)
>
> Dump of assembler code for function SyS_32_futex:
>     0xffffffff811b6fe8<+0>:	sll	a1,a1,0x0
>     0xffffffff811b6fec<+4>:	sll	a2,a2,0x0
>     0xffffffff811b6ff0<+8>:	j	0xffffffff8121a240<compat_sys_futex>
>     0xffffffff811b6ff4<+12>:	sll	a5,a5,0x0
>
> Signed-off-by: Yong Zhang<yong.zhang@windriver.com>
> Cc: Ralf Baechle<ralf@linux-mips.org>
> ---
>   arch/mips/kernel/linux32.c     |    7 +++++++
>   arch/mips/kernel/scall64-n32.S |    2 +-
>   arch/mips/kernel/scall64-o32.S |    2 +-
>   3 files changed, 9 insertions(+), 2 deletions(-)
[...]
> diff --git a/arch/mips/kernel/linux32.c b/arch/mips/kernel/linux32.c
> index 876a75c..922a554 100644
> --- a/arch/mips/kernel/linux32.c
> +++ b/arch/mips/kernel/linux32.c
> @@ -349,3 +349,10 @@ SYSCALL_DEFINE6(32_fanotify_mark, int, fanotify_fd, unsigned int, flags,
>   	return sys_fanotify_mark(fanotify_fd, flags, merge_64(a3, a4),
>   				 dfd, pathname);
>   }
> +
> +SYSCALL_DEFINE6(32_futex, u32 __user *, uaddr, int, op, u32, val,
> +		struct compat_timespec __user *, utime, u32 __user *, uaddr2,
> +		u32, val3)
> +{
> +	return compat_sys_futex(uaddr, op, val, utime, uaddr2, val3);
> +}
> diff --git a/arch/mips/kernel/scall64-n32.S b/arch/mips/kernel/scall64-n32.S
> index b85842f..c956cc9 100644
> --- a/arch/mips/kernel/scall64-n32.S
> +++ b/arch/mips/kernel/scall64-n32.S
> @@ -315,7 +315,7 @@ EXPORT(sysn32_call_table)
>   	PTR	sys_fremovexattr
>   	PTR	sys_tkill
>   	PTR	sys_ni_syscall
> -	PTR	compat_sys_futex
> +	PTR	sys_32_futex
>   	PTR	compat_sys_sched_setaffinity	/* 6195 */
>   	PTR	compat_sys_sched_getaffinity
>   	PTR	sys_cacheflush
> diff --git a/arch/mips/kernel/scall64-o32.S b/arch/mips/kernel/scall64-o32.S
> index 46c4763..f48b18e 100644
> --- a/arch/mips/kernel/scall64-o32.S
> +++ b/arch/mips/kernel/scall64-o32.S
> @@ -441,7 +441,7 @@ sys_call_table:
>   	PTR	sys_fremovexattr		/* 4235 */
>   	PTR	sys_tkill
>   	PTR	sys_sendfile64
> -	PTR	compat_sys_futex
> +	PTR	sys_32_futex

This change is redundant, scall64-o32.S already does the right thing
so additional zero extending is not needed and is just extra
instructions to execute for no reason.

>   	PTR	compat_sys_sched_setaffinity
>   	PTR	compat_sys_sched_getaffinity	/* 4240 */
>   	PTR	compat_sys_io_setup

But really I think this patch fixes things at the wrong level.  Each
architecture potentially needs a similar patch.  What would happen if
we did something like:


diff --git a/kernel/futex_compat.c b/kernel/futex_compat.c
index 5f9e689..74ada65 100644
--- a/kernel/futex_compat.c
+++ b/kernel/futex_compat.c
@@ -180,9 +180,9 @@ err_unlock:
  	return ret;
  }

-asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, u32 val,
-		struct compat_timespec __user *utime, u32 __user *uaddr2,
-		u32 val3)
+SYSCALL_DEFINE6(compat_sys_futex, u32 __user *, uaddr, int , op, u32, val,
+		struct compat_timespec __user *, utime, u32 __user *, uaddr2,
+		u32, val3)
  {
  	struct timespec ts;
  	ktime_t t, *tp = NULL;

Obviously the function name is wrong, but a varient of
SYSCALL_DEFINE*() could be created so the proper function names are
produced.

David Daney

Re: [PATCH] MIPS: use 32-bit wrapper for compat_sys_futex

[Yong Zhang]

On Wed, Aug 17, 2011 at 10:17:52AM -0700, David Daney wrote:
> >diff --git a/arch/mips/kernel/scall64-o32.S b/arch/mips/kernel/scall64-o32.S
> >index 46c4763..f48b18e 100644
> >--- a/arch/mips/kernel/scall64-o32.S
> >+++ b/arch/mips/kernel/scall64-o32.S
> >@@ -441,7 +441,7 @@ sys_call_table:
> >  	PTR	sys_fremovexattr		/* 4235 */
> >  	PTR	sys_tkill
> >  	PTR	sys_sendfile64
> >-	PTR	compat_sys_futex
> >+	PTR	sys_32_futex
> 
> This change is redundant, scall64-o32.S already does the right thing

My first virsion(not sent out) doesn't include scall64-o32.S either.

> so additional zero extending is not needed and is just extra
> instructions to execute for no reason.

Why I'm adding it here is for:
1)code consistent, otherwise we must move SYSCALL_DEFINE6(32_futex,...)
  under CONFIG_MIPS32_N32;
2)I'm afraid there may be some other way to touch the high 32-bit of a
  register, so touching scall64-o32.S is also for safety(due to unknown
  reason, fix me if I'm wrong).

Thanks,
Yong

Re: [PATCH] MIPS: use 32-bit wrapper for compat_sys_futex

[David Daney]

On 08/17/2011 07:32 PM, Yong Zhang wrote:
> On Wed, Aug 17, 2011 at 10:17:52AM -0700, David Daney wrote:
>>> diff --git a/arch/mips/kernel/scall64-o32.S b/arch/mips/kernel/scall64-o32.S
>>> index 46c4763..f48b18e 100644
>>> --- a/arch/mips/kernel/scall64-o32.S
>>> +++ b/arch/mips/kernel/scall64-o32.S
>>> @@ -441,7 +441,7 @@ sys_call_table:
>>>   	PTR	sys_fremovexattr		/* 4235 */
>>>   	PTR	sys_tkill
>>>   	PTR	sys_sendfile64
>>> -	PTR	compat_sys_futex
>>> +	PTR	sys_32_futex
>>
>> This change is redundant, scall64-o32.S already does the right thing
>
> My first virsion(not sent out) doesn't include scall64-o32.S either.
>
>> so additional zero extending is not needed and is just extra
>> instructions to execute for no reason.
>
> Why I'm adding it here is for:
> 1)code consistent, otherwise we must move SYSCALL_DEFINE6(32_futex,...)
>    under CONFIG_MIPS32_N32;

No, you don't have to move it.  Just don't call it.


> 2)I'm afraid there may be some other way to touch the high 32-bit of a
>    register, so touching scall64-o32.S is also for safety(due to unknown
>    reason, fix me if I'm wrong).

OK: You are mistaken.  You claim you don't understand what the code 
does.  That is really a poor justification for modifying it.

David Daney

Re: [PATCH] MIPS: use 32-bit wrapper for compat_sys_futex

[Yong Zhang]

On Thu, Aug 18, 2011 at 09:23:41AM -0700, David Daney wrote:
> On 08/17/2011 07:32 PM, Yong Zhang wrote:
> >On Wed, Aug 17, 2011 at 10:17:52AM -0700, David Daney wrote:
> >>>diff --git a/arch/mips/kernel/scall64-o32.S b/arch/mips/kernel/scall64-o32.S
> >>>index 46c4763..f48b18e 100644
> >>>--- a/arch/mips/kernel/scall64-o32.S
> >>>+++ b/arch/mips/kernel/scall64-o32.S
> >>>@@ -441,7 +441,7 @@ sys_call_table:
> >>>  	PTR	sys_fremovexattr		/* 4235 */
> >>>  	PTR	sys_tkill
> >>>  	PTR	sys_sendfile64
> >>>-	PTR	compat_sys_futex
> >>>+	PTR	sys_32_futex
> >>
> >>This change is redundant, scall64-o32.S already does the right thing
> >
> >My first virsion(not sent out) doesn't include scall64-o32.S either.
> >
> >>so additional zero extending is not needed and is just extra
> >>instructions to execute for no reason.
> >
> >Why I'm adding it here is for:
> >1)code consistent, otherwise we must move SYSCALL_DEFINE6(32_futex,...)
> >   under CONFIG_MIPS32_N32;
> 
> No, you don't have to move it.  Just don't call it.
> 
> 
> >2)I'm afraid there may be some other way to touch the high 32-bit of a
> >   register, so touching scall64-o32.S is also for safety(due to unknown
> >   reason, fix me if I'm wrong).
> 
> OK: You are mistaken.  You claim you don't understand what the code
> does.  That is really a poor justification for modifying it.

If you don't like it and you are sure there is no potential security problem,
just make a patch to remove it. Go ahead.

Thanks,
Yong

Re: [PATCH] MIPS: use 32-bit wrapper for compat_sys_futex

[Yong Zhang]

On Wed, Aug 17, 2011 at 10:17:52AM -0700, David Daney wrote:
> >  	PTR	compat_sys_sched_setaffinity
> >  	PTR	compat_sys_sched_getaffinity	/* 4240 */
> >  	PTR	compat_sys_io_setup
> 
> But really I think this patch fixes things at the wrong level.  Each
> architecture potentially needs a similar patch.  What would happen if
> we did something like:

I have thought about it but finally I decide to keep it under arch code;
because sparc64 and s390 have the same issue and they all smooth the
concern by themselves.

For sparc64:
arch/sparc/kernel/sys32.S:
91: SIGN3(sys32_futex, compat_sys_futex, %o1, %o2, %o5)

For s390:
arch/s390/kernel/compat_wrapper.S
ENTRY(compat_sys_futex_wrapper)
        llgtr   %r2,%r2                 # u32 *
	lgfr    %r3,%r3                 # int
	lgfr    %r4,%r4                 # int
	llgtr   %r5,%r5                 # struct compat_timespec *
	llgtr   %r6,%r6                 # u32 *
	lgf     %r0,164(%r15)           # int
	stg     %r0,160(%r15)
	jg	compat_sys_futex	# branch to system call

Maybe we can consolidate all of this like your patch in the future,
but it's a different issue.

Thanks,
Yong

> 
> 
> diff --git a/kernel/futex_compat.c b/kernel/futex_compat.c
> index 5f9e689..74ada65 100644
> --- a/kernel/futex_compat.c
> +++ b/kernel/futex_compat.c
> @@ -180,9 +180,9 @@ err_unlock:
>  	return ret;
>  }
> 
> -asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, u32 val,
> -		struct compat_timespec __user *utime, u32 __user *uaddr2,
> -		u32 val3)
> +SYSCALL_DEFINE6(compat_sys_futex, u32 __user *, uaddr, int , op, u32, val,
> +		struct compat_timespec __user *, utime, u32 __user *, uaddr2,
> +		u32, val3)
>  {
>  	struct timespec ts;
>  	ktime_t t, *tp = NULL;
> 
> Obviously the function name is wrong, but a varient of
> SYSCALL_DEFINE*() could be created so the proper function names are
> produced.
> 
> David Daney

Re: [PATCH] MIPS: use 32-bit wrapper for compat_sys_futex

[Ralf Baechle]

On Wed, Aug 17, 2011 at 10:17:52AM -0700, David Daney wrote:

> >diff --git a/arch/mips/kernel/scall64-o32.S b/arch/mips/kernel/scall64-o32.S
> >index 46c4763..f48b18e 100644
> >--- a/arch/mips/kernel/scall64-o32.S
> >+++ b/arch/mips/kernel/scall64-o32.S
> >@@ -441,7 +441,7 @@ sys_call_table:
> >  	PTR	sys_fremovexattr		/* 4235 */
> >  	PTR	sys_tkill
> >  	PTR	sys_sendfile64
> >-	PTR	compat_sys_futex
> >+	PTR	sys_32_futex
> 
> This change is redundant, scall64-o32.S already does the right thing
> so additional zero extending is not needed and is just extra
> instructions to execute for no reason.

Compat_sys_futex is a syscall entry point and for some configurations
such as CONFIG_FTRACE_SYSCALLS SYSCALL_DEFINE*() will do additional work
beyond cleaning up the arguments.  The 3 unnecessary shifts are the
overhead we just gotta live with.

> >  	PTR	compat_sys_sched_setaffinity
> >  	PTR	compat_sys_sched_getaffinity	/* 4240 */
> >  	PTR	compat_sys_io_setup
> 
> But really I think this patch fixes things at the wrong level.  Each
> architecture potentially needs a similar patch.  What would happen if
> we did something like:

> +++ b/kernel/futex_compat.c
> @@ -180,9 +180,9 @@ err_unlock:
>  	return ret;
>  }
> 
> -asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, u32 val,
> -		struct compat_timespec __user *utime, u32 __user *uaddr2,
> -		u32 val3)
> +SYSCALL_DEFINE6(compat_sys_futex, u32 __user *, uaddr, int , op, u32, val,
> +		struct compat_timespec __user *, utime, u32 __user *, uaddr2,
> +		u32, val3)
>  {
>  	struct timespec ts;
>  	ktime_t t, *tp = NULL;
> 
> Obviously the function name is wrong, but a varient of
> SYSCALL_DEFINE*() could be created so the proper function names are
> produced.

Right now none of the the generic compat_ functions is wrapped in
SYSCALL_DEFINE* because for some architectures a further wrapper function
is needed.  It seems some architectures call compat_ calls directly
without SYSCALL_DEFINE* which with CONFIG_FTRACE_SYSCALLS is a bug ...

  Ralf

How to trace compat syscalls? [Was Re: [PATCH] MIPS: use 32-bit wrapper for compat_sys_futex]

[Yong Zhang]

Cc'ing more people.

On Thu, Aug 18, 2011 at 09:19:11PM +0100, Ralf Baechle wrote:
> > But really I think this patch fixes things at the wrong level.  Each
> > architecture potentially needs a similar patch.  What would happen if
> > we did something like:
> 
> > +++ b/kernel/futex_compat.c
> > @@ -180,9 +180,9 @@ err_unlock:
> >  	return ret;
> >  }
> > 
> > -asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, u32 val,
> > -		struct compat_timespec __user *utime, u32 __user *uaddr2,
> > -		u32 val3)
> > +SYSCALL_DEFINE6(compat_sys_futex, u32 __user *, uaddr, int , op, u32, val,
> > +		struct compat_timespec __user *, utime, u32 __user *, uaddr2,
> > +		u32, val3)
> >  {
> >  	struct timespec ts;
> >  	ktime_t t, *tp = NULL;
> > 
> > Obviously the function name is wrong, but a varient of
> > SYSCALL_DEFINE*() could be created so the proper function names are
> > produced.
> 
> Right now none of the the generic compat_ functions is wrapped in
> SYSCALL_DEFINE* because for some architectures a further wrapper function
> is needed.  It seems some architectures call compat_ calls directly
> without SYSCALL_DEFINE* which with CONFIG_FTRACE_SYSCALLS is a bug ...

Just checked some archs which have HAVE_SYSCALL_TRACEPOINTS=y and could
call compat_* syscalls when run 32bit process on 64bit kernel, I don't
find any special code against FTRACE_SYSCALLS. So that means we could
not trace compat syscalls even if we want to(Am I missing something?).
So I think if we want to trace it, the easy way is just like what we have
done on normal syscalls, IOW, we could SYSCALL_DEFINE all of the compat
syscalls.

Thought?

BTW, I have make a trival patch to introduce COMPAT_SYSCALL_DEFINE, it's just
for calling of inspiration(no test no build, and I leave SYSCALL_METADATA
etc untouched.)

Thanks,
Yong

---
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 8c03b98..e79027f 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -221,26 +221,38 @@ extern struct trace_event_functions exit_syscall_print_funcs;
 		__SC_STR_ADECL##x(__VA_ARGS__)			\
 	};							\
 	SYSCALL_METADATA(sname, x);				\
-	__SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
+	__SYSCALL_DEFINEx(, x, sname, __VA_ARGS__)
+
+#define COMPAT_SYSCALL_DEFINEx(x, sname, ...)			\
+	static const char *types_compat_##sname[] = {		\
+		__SC_STR_TDECL##x(__VA_ARGS__)			\
+	};							\
+	static const char *args_compat_##sname[] = {		\
+		__SC_STR_ADECL##x(__VA_ARGS__)			\
+	};							\
+	SYSCALL_METADATA(compat, sname, x);			\
+	__SYSCALL_DEFINEx(cmopat_, x, sname, __VA_ARGS__)
 #else
 #define SYSCALL_DEFINEx(x, sname, ...)				\
-	__SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
+	__SYSCALL_DEFINEx(, x, sname, __VA_ARGS__)
+#define COMPAT_SYSCALL_DEFINEx(x, sname, ...)			\
+	__SYSCALL_DEFINEx(compat_, x, sname, __VA_ARGS__)
 #endif
 
 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
 
-#define SYSCALL_DEFINE(name) static inline long SYSC_##name
+#define SYSCALL_DEFINE(compat, name) static inline long compat##SYSC_##name
 
-#define __SYSCALL_DEFINEx(x, name, ...)					\
-	asmlinkage long sys##name(__SC_DECL##x(__VA_ARGS__));		\
-	static inline long SYSC##name(__SC_DECL##x(__VA_ARGS__));	\
-	asmlinkage long SyS##name(__SC_LONG##x(__VA_ARGS__))		\
+#define __SYSCALL_DEFINEx(compat, x, name, ...)				\
+	asmlinkage long compat##sys##name(__SC_DECL##x(__VA_ARGS__));	\
+	static inline long compat##SYSC##name(__SC_DECL##x(__VA_ARGS__));\
+	asmlinkage long compat##SyS##name(__SC_LONG##x(__VA_ARGS__))	\
 	{								\
 		__SC_TEST##x(__VA_ARGS__);				\
-		return (long) SYSC##name(__SC_CAST##x(__VA_ARGS__));	\
+		return (long) compat##SYSC##name(__SC_CAST##x(__VA_ARGS__));\
 	}								\
-	SYSCALL_ALIAS(sys##name, SyS##name);				\
-	static inline long SYSC##name(__SC_DECL##x(__VA_ARGS__))
+	SYSCALL_ALIAS(compat##sys##name, compat##SyS##name);		\
+	static inline long compat##SYSC##name(__SC_DECL##x(__VA_ARGS__))
 
 #else /* CONFIG_HAVE_SYSCALL_WRAPPERS */
 

Re: How to trace compat syscalls? [Was Re: [PATCH] MIPS: use 32-bit wrapper for compat_sys_futex]

[Yong Zhang]

On Fri, Aug 19, 2011 at 11:49:50AM +0800, Yong Zhang wrote:
> Cc'ing more people.
> 
> On Thu, Aug 18, 2011 at 09:19:11PM +0100, Ralf Baechle wrote:
> > > But really I think this patch fixes things at the wrong level.  Each
> > > architecture potentially needs a similar patch.  What would happen if
> > > we did something like:
> > 
> > > +++ b/kernel/futex_compat.c
> > > @@ -180,9 +180,9 @@ err_unlock:
> > >  	return ret;
> > >  }
> > > 
> > > -asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, u32 val,
> > > -		struct compat_timespec __user *utime, u32 __user *uaddr2,
> > > -		u32 val3)
> > > +SYSCALL_DEFINE6(compat_sys_futex, u32 __user *, uaddr, int , op, u32, val,
> > > +		struct compat_timespec __user *, utime, u32 __user *, uaddr2,
> > > +		u32, val3)
> > >  {
> > >  	struct timespec ts;
> > >  	ktime_t t, *tp = NULL;
> > > 
> > > Obviously the function name is wrong, but a varient of
> > > SYSCALL_DEFINE*() could be created so the proper function names are
> > > produced.
> > 
> > Right now none of the the generic compat_ functions is wrapped in
> > SYSCALL_DEFINE* because for some architectures a further wrapper function
> > is needed.  It seems some architectures call compat_ calls directly
> > without SYSCALL_DEFINE* which with CONFIG_FTRACE_SYSCALLS is a bug ...
> 
> Just checked some archs which have HAVE_SYSCALL_TRACEPOINTS=y and could
> call compat_* syscalls when run 32bit process on 64bit kernel, I don't
> find any special code against FTRACE_SYSCALLS. So that means we could
> not trace compat syscalls even if we want to(Am I missing something?).
> So I think if we want to trace it, the easy way is just like what we have
> done on normal syscalls, IOW, we could SYSCALL_DEFINE all of the compat
> syscalls.

Except the ones which call sys_* finally, :)

> 
> Thought?
> 
> BTW, I have make a trival patch to introduce COMPAT_SYSCALL_DEFINE, it's just
> for calling of inspiration(no test no build, and I leave SYSCALL_METADATA
> etc untouched.)
> 
> Thanks,
> Yong
> 
> ---
> diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
> index 8c03b98..e79027f 100644
> --- a/include/linux/syscalls.h
> +++ b/include/linux/syscalls.h
> @@ -221,26 +221,38 @@ extern struct trace_event_functions exit_syscall_print_funcs;
>  		__SC_STR_ADECL##x(__VA_ARGS__)			\
>  	};							\
>  	SYSCALL_METADATA(sname, x);				\
> -	__SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
> +	__SYSCALL_DEFINEx(, x, sname, __VA_ARGS__)
> +
> +#define COMPAT_SYSCALL_DEFINEx(x, sname, ...)			\
> +	static const char *types_compat_##sname[] = {		\
> +		__SC_STR_TDECL##x(__VA_ARGS__)			\
> +	};							\
> +	static const char *args_compat_##sname[] = {		\
> +		__SC_STR_ADECL##x(__VA_ARGS__)			\
> +	};							\
> +	SYSCALL_METADATA(compat, sname, x);			\
> +	__SYSCALL_DEFINEx(cmopat_, x, sname, __VA_ARGS__)
>  #else
>  #define SYSCALL_DEFINEx(x, sname, ...)				\
> -	__SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
> +	__SYSCALL_DEFINEx(, x, sname, __VA_ARGS__)
> +#define COMPAT_SYSCALL_DEFINEx(x, sname, ...)			\
> +	__SYSCALL_DEFINEx(compat_, x, sname, __VA_ARGS__)
>  #endif
>  
>  #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
>  
> -#define SYSCALL_DEFINE(name) static inline long SYSC_##name
> +#define SYSCALL_DEFINE(compat, name) static inline long compat##SYSC_##name
>  
> -#define __SYSCALL_DEFINEx(x, name, ...)					\
> -	asmlinkage long sys##name(__SC_DECL##x(__VA_ARGS__));		\
> -	static inline long SYSC##name(__SC_DECL##x(__VA_ARGS__));	\
> -	asmlinkage long SyS##name(__SC_LONG##x(__VA_ARGS__))		\
> +#define __SYSCALL_DEFINEx(compat, x, name, ...)				\
> +	asmlinkage long compat##sys##name(__SC_DECL##x(__VA_ARGS__));	\
> +	static inline long compat##SYSC##name(__SC_DECL##x(__VA_ARGS__));\
> +	asmlinkage long compat##SyS##name(__SC_LONG##x(__VA_ARGS__))	\
>  	{								\
>  		__SC_TEST##x(__VA_ARGS__);				\
> -		return (long) SYSC##name(__SC_CAST##x(__VA_ARGS__));	\
> +		return (long) compat##SYSC##name(__SC_CAST##x(__VA_ARGS__));\
>  	}								\
> -	SYSCALL_ALIAS(sys##name, SyS##name);				\
> -	static inline long SYSC##name(__SC_DECL##x(__VA_ARGS__))
> +	SYSCALL_ALIAS(compat##sys##name, compat##SyS##name);		\
> +	static inline long compat##SYSC##name(__SC_DECL##x(__VA_ARGS__))
>  
>  #else /* CONFIG_HAVE_SYSCALL_WRAPPERS */
>