Consolidate off_t/off64_t syscall argument passing

This patch add three new macros (SYSCALL_LL, SYSCALL_LL64, and
__ASSUME_WORDSIZE64_ILP32) to use along with off_t and off64_t argument
syscalls.  The rationale for this change is:

1. Remove multiple implementations for the same syscall for different
   architectures (for instance, pread have 6 different implementations).

2. Also remove the requirement to use syscall wrappers for cancellable
   entrypoints.

The macro usage should be used along __ALIGNMENT_ARG to follow ABI constrains
for architecture where it applies.  For instance, pread can be rewritten as:

  return SYSCALL_CANCEL (pread, fd, buf, count,
                         __ALIGNMENT_ARG SYSCALL_LL (offset));

Another macro, SYSCALL_LL64, is provided for off64_t.  The macro
__ASSUME_WORDSIZE64_ILP32 is used by the ABI to define is uses 64-bit register
even if ABI is ILP32 (for instance x32 and mips64-n32).

The changes itself are not currently used in any implementation, so no
code change is expected.

	* sysdeps/unix/sysv/linux/generic/sysdep.h (__ALIGNMENT_ARG): Move
	definition.
	(__ALIGNMENT_COUNT): Likewise.
	* sysdeps/unix/sysv/linux/sysdep.h (__ALIGNMENT_ARG): To here.
	(__ALIGNMENT_COUNT): Likewise.
	(SYSCALL_LL): New define.
	(SYSCALL_LL64): Likewise.
	* sysdeps/unix/sysv/linux/mips/kernel-features.h:
	[_MIPS_SIM == _ABIO32] (__ASSUME_WORDSIZE64_ILP32): Define.
	* sysdeps/unix/sysv/linux/x86_64/kernel-features.h:
	[ILP32] (__ASUME_WORDSIZE64_ILP32): Likewise.

ChangeLog

@@ -1,5 +1,17 @@
 2016-04-11  Adhemerval Zanella  <adhemerval.zanella@linaro.org>
 
+	* sysdeps/unix/sysv/linux/generic/sysdep.h (__ALIGNMENT_ARG): Move
+	definition.
+	(__ALIGNMENT_COUNT): Likewise.
+	* sysdeps/unix/sysv/linux/sysdep.h (__ALIGNMENT_ARG): To here.
+	(__ALIGNMENT_COUNT): Likewise.
+	(SYSCALL_LL): New define.
+	(SYSCALL_LL64): Likewise.
+	* sysdeps/unix/sysv/linux/mips/kernel-features.h:
+	[_MIPS_SIM == _ABIO32] (__ASSUME_WORDSIZE64_ILP32): Define.
+	* sysdeps/unix/sysv/linux/x86_64/kernel-features.h:
+	[ILP32] (__ASUME_WORDSIZE64_ILP32): Likewise.
+
 	* sysdeps/unix/sysv/linux/arm/kernel-features.h
 	(__ASSUME_ALIGNED_REGISTER_PAIRS): Define.
 	* sysdeps/unix/sysv/linux/mips/kernel-features.h

sysdeps/unix/sysv/linux/generic/sysdep.h

@@ -31,13 +31,3 @@
 #define __NR_pread __NR_pread64
 #define __NR_pwrite __NR_pwrite64
 #endif
-
-/* Provide a dummy argument that can be used to force register
-   alignment for register pairs if required by the syscall ABI.  */
-#ifdef __ASSUME_ALIGNED_REGISTER_PAIRS
-#define __ALIGNMENT_ARG 0,
-#define __ALIGNMENT_COUNT(a,b) b
-#else
-#define __ALIGNMENT_ARG
-#define __ALIGNMENT_COUNT(a,b) a
-#endif

sysdeps/unix/sysv/linux/mips/kernel-features.h

@@ -34,3 +34,9 @@
 #if _MIPS_SIM == _ABIO32
 # define __ASSUME_ALIGNED_REGISTER_PAIRS	1
 #endif
+
+/* Define that mips64-n32 is a ILP32 ABI to set the correct interface to
+   pass 64-bits values through syscalls.  */
+#if _MIPS_SIM == _ABIN32
+# define __ASSUME_WORDSIZE64_ILP32	1
+#endif

sysdeps/unix/sysv/linux/sysdep.h

@@ -15,6 +15,8 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+#include <bits/wordsize.h>
+
 /* Set error number and return -1.  A target may choose to return the
    internal function, __syscall_error, which sets errno and returns -1.
    We use -1l, instead of -1, so that it can be casted to (void *).  */
@@ -23,3 +25,24 @@
     __set_errno (err);				\
     -1l;					\
   })
+
+/* Provide a dummy argument that can be used to force register
+   alignment for register pairs if required by the syscall ABI.  */
+#ifdef __ASSUME_ALIGNED_REGISTER_PAIRS
+#define __ALIGNMENT_ARG 0,
+#define __ALIGNMENT_COUNT(a,b) b
+#else
+#define __ALIGNMENT_ARG
+#define __ALIGNMENT_COUNT(a,b) a
+#endif
+
+/* Provide a common macro to pass 64-bit value on syscalls.  */
+#if __WORDSIZE == 64 || defined __ASSUME_WORDSIZE64_ILP32
+# define SYSCALL_LL(val)   (val)
+# define SYSCALL_LL64(val) (val)
+#else
+#define SYSCALL_LL(val)   \
+  __LONG_LONG_PAIR ((val) >> 31, (val))
+#define SYSCALL_LL64(val) \
+  __LONG_LONG_PAIR ((long) ((val) >> 32), (long) ((val) & 0xffffffff))
+#endif

sysdeps/unix/sysv/linux/x86_64/kernel-features.h

@@ -22,4 +22,10 @@
 # define __ASSUME_GETCPU_SYSCALL	1
 #endif
 
+/* Define that x32 is a ILP32 ABI to set the correct interface to pass
+   64-bits values through syscalls.  */
+#ifdef __ILP32__
+# define __ASSUME_WORDSIZE64_ILP32	1
+#endif
+
 #include_next <kernel-features.h>