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[PATCH 2/4] Consolidate off_t/off64_t syscall argument passing
- From: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- To: libc-alpha at sourceware dot org
- Cc: Adhemerval Zanella <adhemerval dot zanella at linaro dot com>
- Date: Thu, 25 Feb 2016 17:19:13 -0300
- Subject: [PATCH 2/4] Consolidate off_t/off64_t syscall argument passing
- Authentication-results: sourceware.org; auth=none
- References: <1456431555-14182-1-git-send-email-adhemerval dot zanella at linaro dot org>
From: Adhemerval Zanella <adhemerval.zanella@linaro.com>
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.
---
sysdeps/unix/sysv/linux/generic/sysdep.h | 10 ----------
sysdeps/unix/sysv/linux/mips/kernel-features.h | 6 ++++++
sysdeps/unix/sysv/linux/sysdep.h | 23 +++++++++++++++++++++++
sysdeps/unix/sysv/linux/x86_64/kernel-features.h | 6 ++++++
5 files changed, 47 insertions(+), 10 deletions(-)
diff --git a/sysdeps/unix/sysv/linux/generic/sysdep.h b/sysdeps/unix/sysv/linux/generic/sysdep.h
index 4f2c65d..b0422ff 100644
--- a/sysdeps/unix/sysv/linux/generic/sysdep.h
+++ b/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
diff --git a/sysdeps/unix/sysv/linux/mips/kernel-features.h b/sysdeps/unix/sysv/linux/mips/kernel-features.h
index ea6a914..17ab696 100644
--- a/sysdeps/unix/sysv/linux/mips/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/mips/kernel-features.h
@@ -53,3 +53,9 @@
#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
diff --git a/sysdeps/unix/sysv/linux/sysdep.h b/sysdeps/unix/sysv/linux/sysdep.h
index c98fc3a..5ee73d5 100644
--- a/sysdeps/unix/sysv/linux/sysdep.h
+++ b/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
diff --git a/sysdeps/unix/sysv/linux/x86_64/kernel-features.h b/sysdeps/unix/sysv/linux/x86_64/kernel-features.h
index 0b84f11..569e8f8 100644
--- a/sysdeps/unix/sysv/linux/x86_64/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/x86_64/kernel-features.h
@@ -35,4 +35,10 @@
# 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>
--
1.9.1