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Re: [PATCH v3 2/2] posix: Implement preadv2 and pwritev2


On Sat, Jun 3, 2017 at 8:28 AM, Andreas Schwab <schwab@linux-m68k.org> wrote:
> On Jun 03 2017, "H.J. Lu" <hjl.tools@gmail.com> wrote:
>
>> X32 inherits LO_HI_LONG from x86-64.  If we change x86-64
>> LO_HI_LONG, x32 needs to redefine LO_HI_LONG.
>
> Your LO_HI_LONG_FLAGS doesn't work for x32 either.
>

My patch redefined LO_HI_LONG_FLAGS for x32.   Here is an alternate
patch which defines different LO_HI_LONGs for x86-64 and x32.

Tested on x86-64 and x32.


-- 
H.J.
From a9a12a727f6bed053ce1396ec44a754585de4167 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Fri, 2 Jun 2017 18:31:16 -0700
Subject: [PATCH] x86-64: Update LO_HI_LONG for p{readv,writev}{64}v2

The kernel interface for p{readv,writev}{64}v is

(unsigned long fd, {const }struct iovec *iov, unsigned long vlen,
 unsigned long pos_l, unsigned long pos_h)

Except for targets which define __ARCH_WANT_COMPAT_SYS_PREADV64 and
__ARCH_WANT_COMPAT_SYS_PWRITEV64,

(unsigned long fd, {const }struct iovec *iov, unsigned long vlen,
 off64_t pos)

is used for p{readv,writev}{64}v.  X32 is the only such target.  The
LO_HI_LONG macro is used to pass offset to the pos_l and pos_h pair.
Since pos_h is ignored when size of offset == sizeof of pos_l, x86-64
has

 #define LO_HI_LONG(val) (val)

But the kernel interface for p{readv,writev}{64}v2 is

(unsigned long fd, {const }struct iovec *iov, unsigned long vlen,
 unsigned long pos_l, unsigned long pos_h, int flags)

Except for targets which define __ARCH_WANT_COMPAT_SYS_PREADV64V2 and
__ARCH_WANT_COMPAT_SYS_PWRITEV64V2,

(unsigned long fd, {const }struct iovec *iov, unsigned long vlen,
 off64_t pos, int flags)

is used for p{readv,writev}{64}v2.  X32 is the only such target.  Update
x86-64 LO_HI_LONG to pass 0 as the high part of the offset argument for
p{readv,writev}{64}v2 and define a different LO_HI_LONG for x32 to only
pass one argument for offset.

Tested on x32 and x86-64.

	* sysdeps/unix/sysv/linux/x86_64/sysdep.h (LO_HI_LONG): Pass
	0 as the high part of offset.
	* sysdeps/unix/sysv/linux/x86_64/x32/sysdep.h (LO_HI_LONG): New.
---
 sysdeps/unix/sysv/linux/x86_64/sysdep.h     | 2 +-
 sysdeps/unix/sysv/linux/x86_64/x32/sysdep.h | 4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/sysdeps/unix/sysv/linux/x86_64/sysdep.h b/sysdeps/unix/sysv/linux/x86_64/sysdep.h
index 7b8bd79..880e496 100644
--- a/sysdeps/unix/sysv/linux/x86_64/sysdep.h
+++ b/sysdeps/unix/sysv/linux/x86_64/sysdep.h
@@ -387,6 +387,6 @@
 
 /* How to pass the off{64}_t argument on p{readv,writev}{64}.  */
 #undef LO_HI_LONG
-#define LO_HI_LONG(val) (val)
+#define LO_HI_LONG(val) (val), 0
 
 #endif /* linux/x86_64/sysdep.h */
diff --git a/sysdeps/unix/sysv/linux/x86_64/x32/sysdep.h b/sysdeps/unix/sysv/linux/x86_64/x32/sysdep.h
index f90fcfa..04c73a2 100644
--- a/sysdeps/unix/sysv/linux/x86_64/x32/sysdep.h
+++ b/sysdeps/unix/sysv/linux/x86_64/x32/sysdep.h
@@ -22,4 +22,8 @@
 #include <sysdeps/unix/sysv/linux/x86_64/sysdep.h>
 #include <sysdeps/x86_64/x32/sysdep.h>
 
+/* How to pass the off{64}_t argument on p{readv,writev}{64}.  */
+#undef LO_HI_LONG
+#define LO_HI_LONG(val) (val)
+
 #endif /* linux/x86_64/x32/sysdep.h */
-- 
2.9.4


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