Re: [PATCH] mips/o32: fix internal_syscall5/6/7

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

On 17/08/2017 18:20, Aurelien Jarno wrote:
> On 2017-08-17 18:09, Adhemerval Zanella wrote:
>>
>>
>> On 17/08/2017 17:34, Maciej W. Rozycki wrote:
>>> On Thu, 17 Aug 2017, Adhemerval Zanella wrote:
>>>
>>>> My point is I think we should aim for compiler optimization safeness
>>>> (to avoid code breakage over compiler defined default flags) and taking
>>>> as base current approach to *avoid* VLA on GLIBC I do not think it is
>>>> good approach to use it as a bridge to force GCC to generate the expected
>>>> code.
>>>
>>>  You certainly have a point here overall, although I don't think a VLA 
>>> whose size is always 0 really hurts.  And we've used the approach with 
>>> `alloca' since forever with no adverse effects until we added a place 
>>> where the caller invokes the syscall wrapper in a loop.  So I wouldn't 
>>> necessarily call it an issue.  Mind that this is target-specific code, so 
>>> we can rely on a target-specific execution model rather than limiting 
>>> ourselves to what generic ISO C guarantees.
>>>
>>>  Aurelien's figures indicating a clear size reduction certainly count as a 
>>> pro though.
>>
>> Joseph pointed out another advantage of avoid VLAs (building with 
>> -Werror=alloca -Werror=vla).  My main problem here is we are betting that
>> compiler won't mess with our assumptions and generate the desirable code
>> without trying to adhere what it is suppose to provide.  Target generic
>> ISO C give us a better guarantee and any deviation indicates a possible
>> compiler issue, not otherwise (such this case).  My another point is we
>> can optimize if required later if this is the case and imho this is hardly
>> the case here (at least for latency).
>>
>> If I understood correctly Aurelien's suggestion of returning err in v1
>> is not ABI strictly so it will end up calling __libc_do_syscall with a
>> non-conformant ABI convention (similar to pipe implementation where requires
>> assembly specific implementation for a lot of architectures to get this
>> right).  Again this is something I would really to avoid.
>>
>>>
>>>> I still thinking trying to optimize for 5/6/7 syscall argument is over
>>>> engineering in this *specific* case.  As I put in my last message,
>>>> 5/6/7 argument syscalls are used for 
>>>>
>>>> pread, pwrite, lseek, llseek, ppoll, posix_fadvice, posix_fallocate, 
>>>> sync_file_range, fallocate, preadv, pwritev, preadv2, pwritev2, select,
>>>> pselect, mmap, readahead, epoll_pwait, splice, recvfrom, sendto, recvmmsg,
>>>> msgsnd, msgrcv, msgget, msgctl, semop, semget, semctl, semtimedop, shmat,
>>>> shmdt, shmget, and shmctl. 
>>>>
>>>> Which are the one generated from C implementation (some are still auto
>>>> generated).  The majority of them are blocking syscalls, so both context
>>>> switch plus the required work for syscall completion itself will taking
>>>> proportionally all the required time.  So trying to squeeze some cycles
>>>> don't really pay off comparing to code maintainability (just all this
>>>> discussion of which C construct would be safe enough to generate the 
>>>> correct stack spill plus the current issue should indicate we should
>>>> aim for correctness first).
>>>
>>>  TBH, I find it questionable whether it's really the approach I proposed 
>>> that requires more engineering (and long-term maintenance) effort rather 
>>> than using a separate handwritten assembly-language call stub.  Especially 
>>> if a non-standard calling convention is used.
>>
>> IMHO I find the VLA suggestion more fragile in long term.
>>
>>>
>>>  If everyone but me thinks there's a clear advantage in using such a 
>>> handcoded stub though, then as I previously noted please adjust the 
>>> affected MIPS16 stubs to avoid the extra indirection, i.e. you can call 
>>> `__libc_do_syscall' directly from MIPS16 code as you'd do from regular 
>>> MIPS or microMIPS code, as the lone reason for the existence of the MIPS16 
>>> stubs is the inexistence of a MIPS16 SYSCALL instruction.
>>
>> Ok, I will try to at least check it on qemu. If you have any points on how
>> correctly build a mips16 glibc it could be helpful. 
> 
> The patch below, based on Adhemerval's version should do it. The changes
> I have done:
> - return err through v1 instead of using a negative value
> - fix build of mips16-syscallX.c
> - route mips16 syscalls with 5 to 7th arguments through __libc_do_syscall

Thanks for complementing it, I was about to send patched version with same
modification (I figured out 64 bits return ints can be used here reading
mips16 syscall code).  Patch LGTM, I would just add some comments to give why
__libc_do_syscall is required (as for other ports). Comment below.

> 
> I see no regression on mipsel o32. I have only lightly tested mips o32
> (the testsuite is still running). I haven't been able to fully compile
> mips16 due to the following error compiling dl-tunables.c:
> 
> /tmp/ccI2NMgJ.s: Assembler messages:
> /tmp/ccI2NMgJ.s:1376: Error: branch to a symbol in another ISA mode
> 
> It doesn't seem to be related to my changes.

I haven't tests with --enable-tunables, but I could build a mips16 with
default options.  The only issue, although, is the new tst-gmon.c test:

tst-gmon.c: In function ‘f1’:
tst-gmon.c:25:1: sorry, unimplemented: mips16 function profiling
 }
 ^

Which is unrelated to this patch.

> 
> Aurelien
> 
> diff --git a/sysdeps/unix/sysv/linux/mips/mips32/Makefile b/sysdeps/unix/sysv/linux/mips/mips32/Makefile
> index 33b461500c..cbdf032c3a 100644
> --- a/sysdeps/unix/sysv/linux/mips/mips32/Makefile
> +++ b/sysdeps/unix/sysv/linux/mips/mips32/Makefile
> @@ -1,8 +1,26 @@
> +ifeq ($(subdir),elf)
> +sysdep-dl-routines += libc-do-syscall
> +endif
> +
>  ifeq ($(subdir),conform)
>  # For bugs 17786 and 21278.
>  conformtest-xfail-conds += mips-o32-linux
>  endif
>  
> +ifeq ($(subdir),io)
> +sysdep_routines += libc-do-syscall
> +endif
> +
> +ifeq ($(subdir),nptl)
> +libpthread-sysdep_routines += libc-do-syscall
> +libpthread-shared-only-routines += libc-do-syscall
> +endif
> +
> +ifeq ($(subdir),rt)
> +librt-sysdep_routines += libc-do-syscall
> +librt-shared-only-routines += libc-do-syscall
> +endif
> +
>  ifeq ($(subdir),stdlib)
>  tests += bug-getcontext-mips-gp
>  endif
> diff --git a/sysdeps/unix/sysv/linux/mips/mips32/libc-do-syscall.S b/sysdeps/unix/sysv/linux/mips/mips32/libc-do-syscall.S
> new file mode 100644
> index 0000000000..c02f507008
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/mips/mips32/libc-do-syscall.S
> @@ -0,0 +1,52 @@
> +/* Copyright (C) 2017 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library.  If not, see
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#include <sys/asm.h>
> +#include <sysdep.h>
> +#include <asm/unistd.h>
> +#include <sgidefs.h>
> +
> +
> +/* long int __libc_do_syscall (long int, ...)  */

I added some comments in my version:

/* Out-of-line syscall stub used for 5, 6, and 7 argument syscall which
   requires arguments in stack.  It follows the MIPS ABI similar to the C
   prototype:

   long int __libc_do_syscall (long int, ...)

   With syscall number in a0, first argument in a1, second in a2, third
   in a3 and the 4th-7th on stack.   */

> +
> +#define FRAMESZ 32
> +
> +	.text
> +	.set    nomips16
> +	.hidden __libc_do_syscall
> +ENTRY(__libc_do_syscall)
> +	move    v0, a0
> +	move    a0, a1
> +	move    a1, a2
> +	move    a2, a3
> +	lw      a3, 16(sp)
> +	lw      t0, 20(sp)
> +	lw      t1, 24(sp)
> +	lw      t2, 28(sp)
> +	.set 	noreorder
> +	PTR_SUBU sp, FRAMESZ
> +	cfi_adjust_cfa_offset (FRAMESZ)
> +	sw      t0, 16(sp)
> +	sw      t1, 20(sp)
> +	sw      t2, 24(sp)
> +	syscall
> +	PTR_ADDU sp, FRAMESZ
> +	cfi_adjust_cfa_offset (-FRAMESZ)
> +	.set	reorder
> +	move    v1, a3
> +1:      ret
> +END (__libc_do_syscall)
> diff --git a/sysdeps/unix/sysv/linux/mips/mips32/mips16/Makefile b/sysdeps/unix/sysv/linux/mips/mips32/mips16/Makefile
> index fa9fcb7e6f..6869bf4f7c 100644
> --- a/sysdeps/unix/sysv/linux/mips/mips32/mips16/Makefile
> +++ b/sysdeps/unix/sysv/linux/mips/mips32/mips16/Makefile
> @@ -1,13 +1,9 @@
>  ifeq ($(subdir),misc)
>  sysdep_routines += mips16-syscall0 mips16-syscall1 mips16-syscall2
> -sysdep_routines += mips16-syscall3 mips16-syscall4 mips16-syscall5
> -sysdep_routines += mips16-syscall6 mips16-syscall7
> +sysdep_routines += mips16-syscall3 mips16-syscall4
>  CFLAGS-mips16-syscall0.c += -fexceptions
>  CFLAGS-mips16-syscall1.c += -fexceptions
>  CFLAGS-mips16-syscall2.c += -fexceptions
>  CFLAGS-mips16-syscall3.c += -fexceptions
>  CFLAGS-mips16-syscall4.c += -fexceptions
> -CFLAGS-mips16-syscall5.c += -fexceptions
> -CFLAGS-mips16-syscall6.c += -fexceptions
> -CFLAGS-mips16-syscall7.c += -fexceptions
>  endif
> diff --git a/sysdeps/unix/sysv/linux/mips/mips32/mips16/Versions b/sysdeps/unix/sysv/linux/mips/mips32/mips16/Versions
> index 73bcfb566c..bb21747f44 100644
> --- a/sysdeps/unix/sysv/linux/mips/mips32/mips16/Versions
> +++ b/sysdeps/unix/sysv/linux/mips/mips32/mips16/Versions
> @@ -1,6 +1,6 @@
>  libc {
>    GLIBC_PRIVATE {
>      __mips16_syscall0; __mips16_syscall1; __mips16_syscall2; __mips16_syscall3;
> -    __mips16_syscall4; __mips16_syscall5; __mips16_syscall6; __mips16_syscall7;
> +    __mips16_syscall4;
>    }
>  }
> diff --git a/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall.h b/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall.h
> index 880e9908e8..60f856d248 100644
> --- a/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall.h
> +++ b/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall.h
> @@ -21,17 +21,6 @@
>  
>  #define __nomips16 __attribute__ ((nomips16))
>  
> -union __mips16_syscall_return
> -  {
> -    long long val;
> -    struct
> -      {
> -	long v0;
> -	long v1;
> -      }
> -    reg;
> -  };
> -
>  long long __nomips16 __mips16_syscall0 (long number);
>  #define __mips16_syscall0(dummy, number)				\
>  	__mips16_syscall0 ((long) (number))
> diff --git a/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall0.c b/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall0.c
> index 490245b34e..b9f78e875f 100644
> --- a/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall0.c
> +++ b/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall0.c
> @@ -24,7 +24,7 @@
>  long long __nomips16
>  __mips16_syscall0 (long number)
>  {
> -  union __mips16_syscall_return ret;
> +  union __libc_do_syscall_return ret;
>    ret.reg.v0 = INTERNAL_SYSCALL_MIPS16 (number, ret.reg.v1, 0);
>    return ret.val;
>  }
> diff --git a/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall1.c b/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall1.c
> index 3061e8accb..284ce712cc 100644
> --- a/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall1.c
> +++ b/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall1.c
> @@ -25,7 +25,7 @@ long long __nomips16
>  __mips16_syscall1 (long a0,
>  		   long number)
>  {
> -  union __mips16_syscall_return ret;
> +  union __libc_do_syscall_return ret;
>    ret.reg.v0 = INTERNAL_SYSCALL_MIPS16 (number, ret.reg.v1, 1,
>  					a0);
>    return ret.val;
> diff --git a/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall2.c b/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall2.c
> index 440a4ed285..4e76329239 100644
> --- a/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall2.c
> +++ b/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall2.c
> @@ -25,7 +25,7 @@ long long __nomips16
>  __mips16_syscall2 (long a0, long a1,
>  		   long number)
>  {
> -  union __mips16_syscall_return ret;
> +  union __libc_do_syscall_return ret;
>    ret.reg.v0 = INTERNAL_SYSCALL_MIPS16 (number, ret.reg.v1, 2,
>  					a0, a1);
>    return ret.val;
> diff --git a/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall3.c b/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall3.c
> index c3f83fc1f6..dbb31d2f20 100644
> --- a/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall3.c
> +++ b/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall3.c
> @@ -25,7 +25,7 @@ long long __nomips16
>  __mips16_syscall3 (long a0, long a1, long a2,
>  		   long number)
>  {
> -  union __mips16_syscall_return ret;
> +  union __libc_do_syscall_return ret;
>    ret.reg.v0 = INTERNAL_SYSCALL_MIPS16 (number, ret.reg.v1, 3,
>  					a0, a1, a2);
>    return ret.val;
> diff --git a/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall4.c b/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall4.c
> index 496297d296..a5dade3b3f 100644
> --- a/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall4.c
> +++ b/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall4.c
> @@ -25,7 +25,7 @@ long long __nomips16
>  __mips16_syscall4 (long a0, long a1, long a2, long a3,
>  		   long number)
>  {
> -  union __mips16_syscall_return ret;
> +  union __libc_do_syscall_return ret;
>    ret.reg.v0 = INTERNAL_SYSCALL_MIPS16 (number, ret.reg.v1, 4,
>  					a0, a1, a2, a3);
>    return ret.val;
> diff --git a/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall5.c b/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall5.c
> deleted file mode 100644
> index ad265d88e2..0000000000
> --- a/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall5.c
> +++ /dev/null
> @@ -1,33 +0,0 @@
> -/* MIPS16 syscall wrappers.
> -   Copyright (C) 2013-2017 Free Software Foundation, Inc.
> -   This file is part of the GNU C Library.
> -
> -   The GNU C Library is free software; you can redistribute it and/or
> -   modify it under the terms of the GNU Lesser General Public
> -   License as published by the Free Software Foundation; either
> -   version 2.1 of the License, or (at your option) any later version.
> -
> -   The GNU C Library is distributed in the hope that it will be useful,
> -   but WITHOUT ANY WARRANTY; without even the implied warranty of
> -   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> -   Lesser General Public License for more details.
> -
> -   You should have received a copy of the GNU Lesser General Public
> -   License along with the GNU C Library; if not, see
> -   <http://www.gnu.org/licenses/>.  */
> -
> -#include <sysdep.h>
> -#include <mips16-syscall.h>
> -
> -#undef __mips16_syscall5
> -
> -long long __nomips16
> -__mips16_syscall5 (long a0, long a1, long a2, long a3,
> -		   long a4,
> -		   long number)
> -{
> -  union __mips16_syscall_return ret;
> -  ret.reg.v0 = INTERNAL_SYSCALL_MIPS16 (number, ret.reg.v1, 5,
> -					a0, a1, a2, a3, a4);
> -  return ret.val;
> -}
> diff --git a/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall6.c b/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall6.c
> deleted file mode 100644
> index bfbd395ed3..0000000000
> --- a/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall6.c
> +++ /dev/null
> @@ -1,33 +0,0 @@
> -/* MIPS16 syscall wrappers.
> -   Copyright (C) 2013-2017 Free Software Foundation, Inc.
> -   This file is part of the GNU C Library.
> -
> -   The GNU C Library is free software; you can redistribute it and/or
> -   modify it under the terms of the GNU Lesser General Public
> -   License as published by the Free Software Foundation; either
> -   version 2.1 of the License, or (at your option) any later version.
> -
> -   The GNU C Library is distributed in the hope that it will be useful,
> -   but WITHOUT ANY WARRANTY; without even the implied warranty of
> -   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> -   Lesser General Public License for more details.
> -
> -   You should have received a copy of the GNU Lesser General Public
> -   License along with the GNU C Library; if not, see
> -   <http://www.gnu.org/licenses/>.  */
> -
> -#include <sysdep.h>
> -#include <mips16-syscall.h>
> -
> -#undef __mips16_syscall6
> -
> -long long __nomips16
> -__mips16_syscall6 (long a0, long a1, long a2, long a3,
> -		   long a4, long a5,
> -		   long number)
> -{
> -  union __mips16_syscall_return ret;
> -  ret.reg.v0 = INTERNAL_SYSCALL_MIPS16 (number, ret.reg.v1, 6,
> -					a0, a1, a2, a3, a4, a5);
> -  return ret.val;
> -}
> diff --git a/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall7.c b/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall7.c
> deleted file mode 100644
> index e1267616dc..0000000000
> --- a/sysdeps/unix/sysv/linux/mips/mips32/mips16/mips16-syscall7.c
> +++ /dev/null
> @@ -1,33 +0,0 @@
> -/* MIPS16 syscall wrappers.
> -   Copyright (C) 2013-2017 Free Software Foundation, Inc.
> -   This file is part of the GNU C Library.
> -
> -   The GNU C Library is free software; you can redistribute it and/or
> -   modify it under the terms of the GNU Lesser General Public
> -   License as published by the Free Software Foundation; either
> -   version 2.1 of the License, or (at your option) any later version.
> -
> -   The GNU C Library is distributed in the hope that it will be useful,
> -   but WITHOUT ANY WARRANTY; without even the implied warranty of
> -   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> -   Lesser General Public License for more details.
> -
> -   You should have received a copy of the GNU Lesser General Public
> -   License along with the GNU C Library; if not, see
> -   <http://www.gnu.org/licenses/>.  */
> -
> -#include <sysdep.h>
> -#include <mips16-syscall.h>
> -
> -#undef __mips16_syscall7
> -
> -long long __nomips16
> -__mips16_syscall7 (long a0, long a1, long a2, long a3,
> -		   long a4, long a5, long a6,
> -		   long number)
> -{
> -  union __mips16_syscall_return ret;
> -  ret.reg.v0 = INTERNAL_SYSCALL_MIPS16 (number, ret.reg.v1, 7,
> -					a0, a1, a2, a3, a4, a5, a6);
> -  return ret.val;
> -}
> diff --git a/sysdeps/unix/sysv/linux/mips/mips32/sysdep.h b/sysdeps/unix/sysv/linux/mips/mips32/sysdep.h
> index e9e3ee7e82..8e55538a5c 100644
> --- a/sysdeps/unix/sysv/linux/mips/mips32/sysdep.h
> +++ b/sysdeps/unix/sysv/linux/mips/mips32/sysdep.h
> @@ -49,9 +49,9 @@
>  /* Define a macro which expands into the inline wrapper code for a system
>     call.  */
>  #undef INLINE_SYSCALL
> -#define INLINE_SYSCALL(name, nr, args...)                               \
> +#define INLINE_SYSCALL(name, nr, ...)                                   \
>    ({ INTERNAL_SYSCALL_DECL (_sc_err);					\
> -     long result_var = INTERNAL_SYSCALL (name, _sc_err, nr, args);	\
> +     long result_var = INTERNAL_SYSCALL (name, _sc_err, nr, ## __VA_ARGS__); \
>       if ( INTERNAL_SYSCALL_ERROR_P (result_var, _sc_err) )		\
>         {								\
>  	 __set_errno (INTERNAL_SYSCALL_ERRNO (result_var, _sc_err));	\
> @@ -98,6 +98,19 @@
>  #undef INTERNAL_SYSCALL
>  #undef INTERNAL_SYSCALL_NCS
>  
> +long long __attribute__ ((nomips16)) __libc_do_syscall (long int, ...) attribute_hidden;

Same as before, I think it worth adding a comment:

/* MIPS kernel ABI requires for internal_syscall5/6/7 that the 5th and
   following arguments to be on the stack.  To avoid trying force a stack
   allocation (which compiler may optimize) the macros use a auxiliary
   function to actually issue the syscall.  */

> +
> +union __libc_do_syscall_return
> +  {
> +    long long val;
> +    struct
> +      {
> +	long v0;
> +	long v1;
> +      }
> +    reg;
> +  };
> +
>  #ifdef __mips16
>  /* There's no MIPS16 syscall instruction, so we go through out-of-line
>     standard MIPS wrappers.  These do use inline snippets below though,
> @@ -107,13 +120,16 @@
>  
>  # include <mips16-syscall.h>
>  
> -# define INTERNAL_SYSCALL(name, err, nr, args...)			\
> -	INTERNAL_SYSCALL_NCS (SYS_ify (name), err, nr, args)
> +# define INTERNAL_SYSCALL(name, err, nr, ...)				\
> +	INTERNAL_SYSCALL_NCS (SYS_ify (name), err, nr, ## __VA_ARGS__)
>  
> -# define INTERNAL_SYSCALL_NCS(number, err, nr, args...)			\
> +# define INTERNAL_SYSCALL_NCS(number, err, nr, ...)			\
>  ({									\
> -	union __mips16_syscall_return _sc_ret;				\
> -	_sc_ret.val = __mips16_syscall##nr (args, number);		\
> +	union __libc_do_syscall_return _sc_ret;				\
> +	if (nr <= 4)							\
> +	  _sc_ret.val = __mips16_syscall##nr (__VA_ARGS__, number);	\
> +	else								\
> +	  _sc_ret.val = __libc_do_syscall (number, ## __VA_ARGS__);	\
>  	err = _sc_ret.reg.v1;						\
>  	_sc_ret.reg.v0;							\
>  })
> @@ -121,13 +137,13 @@
>  # define INTERNAL_SYSCALL_MIPS16(number, err, nr, args...)		\
>  	internal_syscall##nr ("lw\t%0, %2\n\t",				\
>  			      "R" (number),				\
> -			      0, err, args)
> +			      number, err, args)
>  
>  #else /* !__mips16 */
>  # define INTERNAL_SYSCALL(name, err, nr, args...)			\
>  	internal_syscall##nr ("li\t%0, %2\t\t\t# " #name "\n\t",	\
>  			      "IK" (SYS_ify (name)),			\
> -			      0, err, args)
> +			      SYS_ify(name), err, args)
>  
>  # define INTERNAL_SYSCALL_NCS(number, err, nr, args...)			\
>  	internal_syscall##nr (MOVE32 "\t%0, %2\n\t",			\
> @@ -136,6 +152,7 @@
>  
>  #endif /* !__mips16 */
>  
> +
>  #define internal_syscall0(v0_init, input, number, err, dummy...)	\
>  ({									\
>  	long _sys_result;						\
> @@ -262,110 +279,34 @@
>  	_sys_result;							\
>  })
>  
> -/* We need to use a frame pointer for the functions in which we
> -   adjust $sp around the syscall, or debug information and unwind
> -   information will be $sp relative and thus wrong during the syscall.  As
> -   of GCC 4.7, this is sufficient.  */
> -#define FORCE_FRAME_POINTER						\
> -  void *volatile __fp_force __attribute__ ((unused)) = alloca (4)
> -
>  #define internal_syscall5(v0_init, input, number, err,			\
>  			  arg1, arg2, arg3, arg4, arg5)			\
>  ({									\
> -	long _sys_result;						\
> -									\
> -	FORCE_FRAME_POINTER;						\
> -	{								\
> -	register long __s0 asm ("$16") __attribute__ ((unused))		\
> -	  = (number);							\
> -	register long __v0 asm ("$2");					\
> -	register long __a0 asm ("$4") = (long) (arg1);			\
> -	register long __a1 asm ("$5") = (long) (arg2);			\
> -	register long __a2 asm ("$6") = (long) (arg3);			\
> -	register long __a3 asm ("$7") = (long) (arg4);			\
> -	__asm__ volatile (						\
> -	".set\tnoreorder\n\t"						\
> -	"subu\t$29, 32\n\t"						\
> -	"sw\t%6, 16($29)\n\t"						\
> -	v0_init								\
> -	"syscall\n\t"							\
> -	"addiu\t$29, 32\n\t"						\
> -	".set\treorder"							\
> -	: "=r" (__v0), "+r" (__a3)					\
> -	: input, "r" (__a0), "r" (__a1), "r" (__a2),			\
> -	  "r" ((long) (arg5))						\
> -	: __SYSCALL_CLOBBERS);						\
> -	err = __a3;							\
> -	_sys_result = __v0;						\
> -	}								\
> -	_sys_result;							\
> +        union __libc_do_syscall_return _sys_result;			\
> +	_sys_result.val = __libc_do_syscall (number, arg1, arg2, arg3,	\
> +					     arg4, arg5);		\
> +	err = _sys_result.reg.v1;					\
> +	_sys_result.reg.v0;						\
>  })
>  
>  #define internal_syscall6(v0_init, input, number, err,			\
>  			  arg1, arg2, arg3, arg4, arg5, arg6)		\
>  ({									\
> -	long _sys_result;						\
> -									\
> -	FORCE_FRAME_POINTER;						\
> -	{								\
> -	register long __s0 asm ("$16") __attribute__ ((unused))		\
> -	  = (number);							\
> -	register long __v0 asm ("$2");					\
> -	register long __a0 asm ("$4") = (long) (arg1);			\
> -	register long __a1 asm ("$5") = (long) (arg2);			\
> -	register long __a2 asm ("$6") = (long) (arg3);			\
> -	register long __a3 asm ("$7") = (long) (arg4);			\
> -	__asm__ volatile (						\
> -	".set\tnoreorder\n\t"						\
> -	"subu\t$29, 32\n\t"						\
> -	"sw\t%6, 16($29)\n\t"						\
> -	"sw\t%7, 20($29)\n\t"						\
> -	v0_init								\
> -	"syscall\n\t"							\
> -	"addiu\t$29, 32\n\t"						\
> -	".set\treorder"							\
> -	: "=r" (__v0), "+r" (__a3)					\
> -	: input, "r" (__a0), "r" (__a1), "r" (__a2),			\
> -	  "r" ((long) (arg5)), "r" ((long) (arg6))			\
> -	: __SYSCALL_CLOBBERS);						\
> -	err = __a3;							\
> -	_sys_result = __v0;						\
> -	}								\
> -	_sys_result;							\
> +        union __libc_do_syscall_return _sys_result;			\
> +	_sys_result.val = __libc_do_syscall (number, arg1, arg2, arg3,	\
> +					     arg4, arg5, arg6);		\
> +	err = _sys_result.reg.v1;					\
> +	_sys_result.reg.v0;						\
>  })
>  
>  #define internal_syscall7(v0_init, input, number, err,			\
>  			  arg1, arg2, arg3, arg4, arg5, arg6, arg7)	\
>  ({									\
> -	long _sys_result;						\
> -									\
> -	FORCE_FRAME_POINTER;						\
> -	{								\
> -	register long __s0 asm ("$16") __attribute__ ((unused))		\
> -	  = (number);							\
> -	register long __v0 asm ("$2");					\
> -	register long __a0 asm ("$4") = (long) (arg1);			\
> -	register long __a1 asm ("$5") = (long) (arg2);			\
> -	register long __a2 asm ("$6") = (long) (arg3);			\
> -	register long __a3 asm ("$7") = (long) (arg4);			\
> -	__asm__ volatile (						\
> -	".set\tnoreorder\n\t"						\
> -	"subu\t$29, 32\n\t"						\
> -	"sw\t%6, 16($29)\n\t"						\
> -	"sw\t%7, 20($29)\n\t"						\
> -	"sw\t%8, 24($29)\n\t"						\
> -	v0_init								\
> -	"syscall\n\t"							\
> -	"addiu\t$29, 32\n\t"						\
> -	".set\treorder"							\
> -	: "=r" (__v0), "+r" (__a3)					\
> -	: input, "r" (__a0), "r" (__a1), "r" (__a2),			\
> -	  "r" ((long) (arg5)), "r" ((long) (arg6)), "r" ((long) (arg7))	\
> -	: __SYSCALL_CLOBBERS);						\
> -	err = __a3;							\
> -	_sys_result = __v0;						\
> -	}								\
> -	_sys_result;							\
> +        union __libc_do_syscall_return _sys_result;			\
> +	_sys_result.val = __libc_do_syscall (number, arg1, arg2, arg3,	\
> +					     arg4, arg5, arg6, arg7);	\
> +	err = _sys_result.reg.v1;					\
> +	_sys_result.reg.v0;						\
>  })
>  
>  #define __SYSCALL_CLOBBERS "$1", "$3", "$8", "$9", "$10", "$11", "$12", "$13", \
> 
>