Patchwork sparc: sys32.S incorrect compat-layer splice() system call

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Submitter Mathieu Desnoyers
Date Aug. 19, 2009, 2:56 a.m.
Message ID <20090819025623.GA11677@Krystal>
Download mbox | patch
Permalink /patch/31625/
State Accepted
Delegated to: David Miller
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Comments

Mathieu Desnoyers - Aug. 19, 2009, 2:56 a.m.
Hi David,

I just installed a shiny (old) Sparc64 machine, trying to get LTTng to
run on it (2.6.30 kernel), and noticed this problem when extracting the
buffers: lttd (the daemon) causes faults in __copy_from_user() within
splice().

lttd is compiled as a 32-bits process on my system. The kernel is
64-bits kernel.

I think arch/sparc/kernel/sys32.S has an incorrect splice definition:

SIGN2(sys32_splice, sys_splice, %o0, %o1)

The splice() prototype looks like :

       long splice(int fd_in, loff_t *off_in, int fd_out,
                   loff_t *off_out, size_t len, unsigned int flags);

So I think we should have :

SIGN2(sys32_splice, sys_splice, %o0, %o2)

instead, am I correct ?


BTW, I can't figure out why we have %o5 in :

SIGN2(sys32_sync_file_range, compat_sync_file_range, %o0, %o5)

which takes only 4 arguments:

       int sync_file_range(int fd, off64_t offset, off64_t nbytes,
                  unsigned int flags);

maybe it has something to do with the return value ? Anyway it should
not hurt if it is unused.


I provide the patch for splice() below.

With this patch applied, I have been able to gather a trace with LTTng
and view it in LTTV. Next steps for LTTng support on sparc64 are to add
the syscall and trap instrumentation.

Thanks,

Mathieu


sparc: sys32.S incorrect compat-layer splice() system call

I think arch/sparc/kernel/sys32.S has an incorrect splice definition:

SIGN2(sys32_splice, sys_splice, %o0, %o1)

The splice() prototype looks like :

       long splice(int fd_in, loff_t *off_in, int fd_out,
                   loff_t *off_out, size_t len, unsigned int flags);

So I think we should have :

SIGN2(sys32_splice, sys_splice, %o0, %o2)

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
CC: "David S. Miller" <davem@caip.rutgers.edu>
CC: Jakub Jelinek <jj@ultra.linux.cz>
---
 arch/sparc/kernel/sys32.S |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
David Miller - Aug. 19, 2009, 3:16 a.m.
From: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Date: Tue, 18 Aug 2009 22:56:23 -0400

> I think arch/sparc/kernel/sys32.S has an incorrect splice definition:
> 
> SIGN2(sys32_splice, sys_splice, %o0, %o1)
> 
> The splice() prototype looks like :
> 
>        long splice(int fd_in, loff_t *off_in, int fd_out,
>                    loff_t *off_out, size_t len, unsigned int flags);
> 
> So I think we should have :
> 
> SIGN2(sys32_splice, sys_splice, %o0, %o2)
> 
> instead, am I correct ?

Indeed, that's correct, thanks for your fix.  I'll apply it.

> 
> BTW, I can't figure out why we have %o5 in :
> 
> SIGN2(sys32_sync_file_range, compat_sync_file_range, %o0, %o5)
> 
> which takes only 4 arguments:
> 
>        int sync_file_range(int fd, off64_t offset, off64_t nbytes,
>                   unsigned int flags);
> 
> maybe it has something to do with the return value ? Anyway it should
> not hurt if it is unused.

It takes 4 arguments, but they are passed in 6 registers.  Each
off64_t is passed in two 32-bit register parts.

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Mathieu Desnoyers - Aug. 19, 2009, 3:40 a.m.
* David Miller (davem@davemloft.net) wrote:
> From: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
> Date: Tue, 18 Aug 2009 22:56:23 -0400
> 
> > I think arch/sparc/kernel/sys32.S has an incorrect splice definition:
> > 
> > SIGN2(sys32_splice, sys_splice, %o0, %o1)
> > 
> > The splice() prototype looks like :
> > 
> >        long splice(int fd_in, loff_t *off_in, int fd_out,
> >                    loff_t *off_out, size_t len, unsigned int flags);
> > 
> > So I think we should have :
> > 
> > SIGN2(sys32_splice, sys_splice, %o0, %o2)
> > 
> > instead, am I correct ?
> 
> Indeed, that's correct, thanks for your fix.  I'll apply it.
> 
> > 
> > BTW, I can't figure out why we have %o5 in :
> > 
> > SIGN2(sys32_sync_file_range, compat_sync_file_range, %o0, %o5)
> > 
> > which takes only 4 arguments:
> > 
> >        int sync_file_range(int fd, off64_t offset, off64_t nbytes,
> >                   unsigned int flags);
> > 
> > maybe it has something to do with the return value ? Anyway it should
> > not hurt if it is unused.
> 
> It takes 4 arguments, but they are passed in 6 registers.  Each
> off64_t is passed in two 32-bit register parts.
> 

Thanks for the clarification. So the %o5 is there to sign-extend
"unsigned int flags" ?

Mathieu
David Miller - Aug. 19, 2009, 4:21 a.m.
From: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Date: Tue, 18 Aug 2009 23:40:46 -0400

> * David Miller (davem@davemloft.net) wrote:
>> From: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
>> Date: Tue, 18 Aug 2009 22:56:23 -0400
>> 
>> > BTW, I can't figure out why we have %o5 in :
>> > 
>> > SIGN2(sys32_sync_file_range, compat_sync_file_range, %o0, %o5)
>> > 
>> > which takes only 4 arguments:
>> > 
>> >        int sync_file_range(int fd, off64_t offset, off64_t nbytes,
>> >                   unsigned int flags);
>> > 
>> > maybe it has something to do with the return value ? Anyway it should
>> > not hurt if it is unused.
>> 
>> It takes 4 arguments, but they are passed in 6 registers.  Each
>> off64_t is passed in two 32-bit register parts.
>> 
> 
> Thanks for the clarification. So the %o5 is there to sign-extend
> "unsigned int flags" ?

Yes, but it seems that might be inappropriate (albeit harmless) here.
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Patch

Index: linux-2.6-lttng/arch/sparc/kernel/sys32.S
===================================================================
--- linux-2.6-lttng.orig/arch/sparc/kernel/sys32.S	2009-08-18 21:21:20.000000000 -0400
+++ linux-2.6-lttng/arch/sparc/kernel/sys32.S	2009-08-18 21:56:47.000000000 -0400
@@ -134,7 +134,7 @@  SIGN1(sys32_getpeername, sys_getpeername
 SIGN1(sys32_getsockname, sys_getsockname, %o0)
 SIGN2(sys32_ioprio_get, sys_ioprio_get, %o0, %o1)
 SIGN3(sys32_ioprio_set, sys_ioprio_set, %o0, %o1, %o2)
-SIGN2(sys32_splice, sys_splice, %o0, %o1)
+SIGN2(sys32_splice, sys_splice, %o0, %o2)
 SIGN2(sys32_sync_file_range, compat_sync_file_range, %o0, %o5)
 SIGN2(sys32_tee, sys_tee, %o0, %o1)
 SIGN1(sys32_vmsplice, compat_sys_vmsplice, %o0)