diff mbox

[2/4] Adjust kernel-features.h for sendmmsg/recvmmsg

Message ID 1458592867-3057-3-git-send-email-adhemerval.zanella@linaro.org
State New
Headers show

Commit Message

Adhemerval Zanella Netto March 21, 2016, 8:41 p.m. UTC 
This patch cleanups the __ASSUME_RECVMMSG_* and __ASSUME_SENDMMSG_*
usage in linux recvmmsg and sendmmsg implementation.  It also fixes
a bug on i686/x86_64 when building with 2.6.32 kernel support.  The
changes in this patches are the following:

 * Remove the __ASSUME_RECVMMSG_SYSCALL_WITH_SOCKETCALL for ports that
   for current minimum supported kernel already have direct recvmmsg
   syscall support (microblaze, powerpc, and spart).

 * Add __ASSUME_RECVMMSG_SYSCALL_WITH_SOCKETCALL define for ports that
   still uses socketcall interface (i386, m68k, s390).

 * Remove the __ASSUME_SENDMMSG_SYSCALL_WITH_SOCKETCALL for ports that
   for current minimum supported kernel alread have direct sendmmsg
   syscall support (powerpc, sparc).

 * Add __ASSUME_SENDMMSG_SYSCALL_WITH_SOCKETCALL define for ports that
   still uses socketcall interface (i386, m68k, microblaze, and s390)

Along with the define changes, the linux recvmmsg and sendmmsg implementation
now uses a different strategy to use direct syscall, socketcall, runtime
socketcall (which issues a socketcall and update have_*), and stub function:

 1. If the architecture defines __ASSUME_{RECVMMSG,SENDMMSG}_SYSCALL the
    direct syscall is used instead.  This is the default behavior for most
    ports that do not support socketcall.

 2. Otherwise, if the architecture defines
    __ASSUME_{RECVMMSG,SENDMMSG}_SYSCALL_WITH_SOCKETCALL the socketcall
    interface will be used instead.  Different than the default
    __ASSUME_{RECVMMSG,SENDMMSG}_SOCKETCALL, this define is set per
    architecture.

 3. Otherwise, if the architecure define __ASSUME_SOCKETCALL the
    runtime socketcall call will be used which will test if the kernel
    supports {sendmmsg,recvmmsg} and set have_{recvmmsg,sendmmsg}
    accordingly.

 4. Otherwise the stub warning implementation will be use.

This approach also fixes the following i386/x86_64 issue:

 * For i686 with kernel 3.2.0 but with --enable-kernel=2.6.32 (minimum
   supported kernel) will use direct syscall where it should use runtime
   socketcall

 * For x86_64 with kernel 3.2.0 but with --enable-kernel=2.6.32 (minimum
   kernel) will use syscall where it should use stub.

Tested on i686, x86_64, aarch64, armhf, and powerpc64le.

	* sysdeps/unix/sysv/linux/i386/kernel-features.h
	(__ASSUME_RECVMMSG_SYSCALL_WITH_SOCKETCALL): Remove define.
	[__LINUX_KERNEL_VERSION > 0x030000]
	(__ASSUME_SENDMMSG_SYSCALL_WITH_SOCKETCALL): Add define.
	* sysdeps/unix/sysv/linux/m68k/kernel-features.h
	(__ASSUME_RECVMMSG_SYSCALL_WITH_SOCKETCALL): Likewise.
	(__ASSUME_SENDMMSG_SYSCALL_WITH_SOCKETCALL): Likewise.
	* sysdeps/unix/sysv/linux/microblaze/kernel-features.h
	(__ASSUME_SENDMMSG_SYSCALL_WITH_SOCKETCALL): Likewise.
	(__ASSUME_RECVMMSG_SYSCALL_WITH_SOCKETCALL): Remove define.
	* sysdeps/unix/sysv/linux/powerpc/kernel-features.h
	(__ASSUME_SENDMMSG_SYSCALL_WITH_SOCKETCALL): Likewise.
	* sysdeps/unix/sysv/linux/s390/kernel-features.h
	(__ASSUME_RECVMMSG_SYSCALL_WITH_SOCKETCALL): Add define.
	(__ASSUME_SENDMMSG_SYSCALL_WITH_SOCKETCALL): Likewise.
	* sysdeps/unix/sysv/linux/sh/kernel-features.h
	(__ASSUME_SENDMMSG_SYSCALL_WITH_SOCKETCALL): Remove define.
	* sysdeps/unix/sysv/linux/sparc/kernel-features.h
	(__ASSUME_RECVMMSG_SYSCALL_WITH_SOCKETCALL): Likewise.
	(__ASSUME_SENDMMSG_SYSCALL_WITH_SOCKETCALL): Likewise.
	* sysdeps/unix/sysv/linux/mips/mips32/recvmmsg.c: Remove file.
	* sysdeps/unix/sysv/linux/mips/mips32/sendmmsg.c: Likewise.
	* sysdeps/unix/sysv/linux/recvmmsg.c (recvmmsg): Refactor
	__ASSUME macro usage.
	* sysdeps/unix/sysv/linux/sendmmsg.c (__sendmmsg): Likewise.
---
 ChangeLog                                          | 26 +++++++++++++++++++
 sysdeps/unix/sysv/linux/i386/kernel-features.h     |  8 ++++--
 sysdeps/unix/sysv/linux/m68k/kernel-features.h     |  2 ++
 .../unix/sysv/linux/microblaze/kernel-features.h   |  4 +--
 sysdeps/unix/sysv/linux/mips/mips32/recvmmsg.c     | 29 ----------------------
 sysdeps/unix/sysv/linux/mips/mips32/sendmmsg.c     | 29 ----------------------
 sysdeps/unix/sysv/linux/powerpc/kernel-features.h  |  3 ---
 sysdeps/unix/sysv/linux/recvmmsg.c                 | 26 +++++--------------
 sysdeps/unix/sysv/linux/s390/kernel-features.h     |  2 ++
 sysdeps/unix/sysv/linux/sendmmsg.c                 | 27 ++++++--------------
 sysdeps/unix/sysv/linux/sparc/kernel-features.h    |  6 -----
 11 files changed, 50 insertions(+), 112 deletions(-)
 delete mode 100644 sysdeps/unix/sysv/linux/mips/mips32/recvmmsg.c
 delete mode 100644 sysdeps/unix/sysv/linux/mips/mips32/sendmmsg.c

-- 
1.9.1

Comments

Adhemerval Zanella Netto March 22, 2016, 10:38 a.m. UTC | #1 
On 21-03-2016 20:26, Joseph Myers wrote:
> On Mon, 21 Mar 2016, Adhemerval Zanella wrote:

> 

>>  * Remove the __ASSUME_RECVMMSG_SYSCALL_WITH_SOCKETCALL for ports that

>>    for current minimum supported kernel already have direct recvmmsg

>>    syscall support (microblaze, powerpc, and spart).

>>

>>  * Add __ASSUME_RECVMMSG_SYSCALL_WITH_SOCKETCALL define for ports that

>>    still uses socketcall interface (i386, m68k, s390).

> 

> This inverts the present semantics for the _WITH_SOCKETCALL macros.  At 

> present, it's defined when the syscall should be always preferred to 

> socketcall (even if the syscall isn't guaranteed to be available); you're 

> changing it to mean that the syscall should never be preferred to 

> socketcall unless guaranteed to be available.  Obviously such a change 

> requires an update to the comment in the generic kernel-features.h 

> defining the semantics of __ASSUME_ACCEPT4_SYSCALL_WITH_SOCKETCALL (and 

> that one must be updated with the other two - having different macro 

> semantics for the three functions would be excessively confusing).  

> However, I think it would be much better to use a clearly different macro 

> name if inverting the semantics (again, for all three functions in 

> question).  And similarly, any refactoring of implementations should be 

> done for all three functions together.

> 

> It's true that even with the present semantics, 

> __ASSUME_*_SYSCALL_WITH_SOCKETCALL definitions in the 

> architecture-specific header are unnecessary but harmless in the case 

> where the syscall is assumed to be present with the minimum supported 

> kernel.


In fact I wasn't sure which would be best approach, but base on your comments
and the wrong assumptions I had with the x86 'fixes' I think best approach
would be:

  1. Use syscall if __NR_recvmmsg is defined
  2. Otherwise if socketcall is __ASSUME_RECVMMSG_SYSCALL is defined
  3. Otherwise if runtime socketcall tests if __ASSUME_SOCKETCALL

For current support architectures and kernels, only microblaze and
s390 will use 2 (with s390 using 1. with kernel 4.3+).  The tests
3 will be used only for i386 with default minimum kernel version
(2.6.32) and I think we can remove the stub since it will be 
always defined with the minimum kernel headers we are supporting
(3.2).

> 

>> This approach also fixes the following i386/x86_64 issue:

>>

>>  * For i686 with kernel 3.2.0 but with --enable-kernel=2.6.32 (minimum

>>    supported kernel) will use direct syscall where it should use runtime

>>    socketcall

> 

> Why is this a bug?  For all released i686 kernels, recvmmsg is either 

> available through both socketcall and the syscall, or through neither 

> socketcall and the syscall, and likewise for sendmmsg.  And where both are 

> available, it's better to use the syscall than socketcall (on general 

> principles of socketcall being deprecated).  So libc built for i686 should 

> never try to use socketcall at all for recvmmsg or sendmmsg under any 

> circumstances (it *should* try for accept4 if the minimum kernel is below 

> 4.3, because accept4 is available through socketcall on more kernels than 

> the syscall).

> 

>>  * For x86_64 with kernel 3.2.0 but with --enable-kernel=2.6.32 (minimum

>>    kernel) will use syscall where it should use stub.

> 

> No, it should use the syscall (which might or might not exist at runtime).  

> It's always wrong to use the stub implementation if the syscall number is 

> known and so the syscall might be available at runtime.

> 

> The only reason stubs might be used at all for any of accept4, recvmmsg, 

> sendmmsg on any GNU/Linux architecture is on non-socketcall architectures 

> where the syscall number is unavailable in the kernel headers used.  Given 

> the requirement for >= 3.2 headers on all architectures, this applies to 

> accept4 on ia64, and no other cases.

>
diff mbox

Patch

diff --git a/sysdeps/unix/sysv/linux/i386/kernel-features.h b/sysdeps/unix/sysv/linux/i386/kernel-features.h
index 148963c..3e25476 100644
--- a/sysdeps/unix/sysv/linux/i386/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/i386/kernel-features.h
@@ -21,10 +21,14 @@ 
 #define __ASSUME_SOCKETCALL		1
 
 /* The recvmmsg syscall was added for i386 in 2.6.33.  */
-#define __ASSUME_RECVMMSG_SYSCALL_WITH_SOCKETCALL	1
+#if __LINUX_KERNEL_VERSION >= 0x020621
+# define __ASSUME_RECVMMSG_SYSCALL_WITH_SOCKETCALL	1
+#endif
 
 /* The sendmmsg syscall was added for i386 in 3.0.  */
-#define __ASSUME_SENDMMSG_SYSCALL_WITH_SOCKETCALL	1
+#if __LINUX_KERNEL_VERSION >= 0x030000
+# define __ASSUME_SENDMMSG_SYSCALL_WITH_SOCKETCALL	1
+#endif
 
 /* Direct socketcalls available with kernel 4.3.  */
 #if __LINUX_KERNEL_VERSION >= 0x040300
diff --git a/sysdeps/unix/sysv/linux/m68k/kernel-features.h b/sysdeps/unix/sysv/linux/m68k/kernel-features.h
index dec04f0..0945779 100644
--- a/sysdeps/unix/sysv/linux/m68k/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/m68k/kernel-features.h
@@ -19,6 +19,8 @@ 
 
 /* m68k uses socketcall.  */
 #define __ASSUME_SOCKETCALL	1
+#define __ASSUME_RECVMMSG_SYSCALL_WITH_SOCKETCALL	1
+#define __ASSUME_SENDMMSG_SYSCALL_WITH_SOCKETCALL	1
 
 /* Direct socketcalls available with kernel 4.3.  */
 #if __LINUX_KERNEL_VERSION >= 0x040300
diff --git a/sysdeps/unix/sysv/linux/microblaze/kernel-features.h b/sysdeps/unix/sysv/linux/microblaze/kernel-features.h
index db471ef..e25b6ed 100644
--- a/sysdeps/unix/sysv/linux/microblaze/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/microblaze/kernel-features.h
@@ -18,6 +18,7 @@ 
 
 /* MicroBlaze uses socketcall.  */
 #define __ASSUME_SOCKETCALL	1
+#define __ASSUME_SENDMMSG_SYSCALL_WITH_SOCKETCALL	1
 
 /* All supported kernel versions for MicroBlaze have these syscalls.  */
 #define __ASSUME_SOCKET_SYSCALL		1
@@ -36,9 +37,6 @@ 
 #define __ASSUME_GETSOCKOPT_SYSCALL	1
 #define __ASSUME_SETSOCKOPT_SYSCALL	1
 
-/* Support for the accept4 and recvmmsg syscalls was added in 2.6.33.  */
-#define __ASSUME_RECVMMSG_SYSCALL_WITH_SOCKETCALL      1
-
 /* Support for the futimesat syscall was added in 2.6.33.  */
 #define __ASSUME_FUTIMESAT              1
 
diff --git a/sysdeps/unix/sysv/linux/mips/mips32/recvmmsg.c b/sysdeps/unix/sysv/linux/mips/mips32/recvmmsg.c
deleted file mode 100644
index c2a3440..0000000
--- a/sysdeps/unix/sysv/linux/mips/mips32/recvmmsg.c
+++ /dev/null
@@ -1,29 +0,0 @@ 
-/* Copyright (C) 2010-2016 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/>.  */
-
-/* Avoid recvmmsg.c trying to use a definition based on the socketcall
-   syscall and internal_recvmmsg.S.  */
-
-#include <errno.h>
-#include <sys/socket.h>
-
-#include <sysdep-cancel.h>
-#include <sys/syscall.h>
-
-#undef __NR_socketcall
-
-#include <sysdeps/unix/sysv/linux/recvmmsg.c>
diff --git a/sysdeps/unix/sysv/linux/mips/mips32/sendmmsg.c b/sysdeps/unix/sysv/linux/mips/mips32/sendmmsg.c
deleted file mode 100644
index 7cd4e15..0000000
--- a/sysdeps/unix/sysv/linux/mips/mips32/sendmmsg.c
+++ /dev/null
@@ -1,29 +0,0 @@ 
-/* Copyright (C) 2011-2016 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/>.  */
-
-/* Avoid sendmmsg.c trying to use a definition based on the socketcall
-   syscall and internal_sendmmsg.S.  */
-
-#include <errno.h>
-#include <sys/socket.h>
-
-#include <sysdep-cancel.h>
-#include <sys/syscall.h>
-
-#undef __NR_socketcall
-
-#include <sysdeps/unix/sysv/linux/sendmmsg.c>
diff --git a/sysdeps/unix/sysv/linux/powerpc/kernel-features.h b/sysdeps/unix/sysv/linux/powerpc/kernel-features.h
index 5449f18..825c0f0 100644
--- a/sysdeps/unix/sysv/linux/powerpc/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/powerpc/kernel-features.h
@@ -37,7 +37,4 @@ 
 #define __ASSUME_GETSOCKOPT_SYSCALL	1
 #define __ASSUME_SETSOCKOPT_SYSCALL	1
 
-/* The sendmmsg syscall was added for PowerPC in 3.0.  */
-#define __ASSUME_SENDMMSG_SYSCALL_WITH_SOCKETCALL	1
-
 #include_next <kernel-features.h>
diff --git a/sysdeps/unix/sysv/linux/recvmmsg.c b/sysdeps/unix/sysv/linux/recvmmsg.c
index bf18260..fb3f325 100644
--- a/sysdeps/unix/sysv/linux/recvmmsg.c
+++ b/sysdeps/unix/sysv/linux/recvmmsg.c
@@ -16,39 +16,26 @@ 
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-#include <errno.h>
 #include <sys/socket.h>
-
 #include <sysdep-cancel.h>
-#include <sys/syscall.h>
-#include <kernel-features.h>
-
-/* Do not use the recvmmsg syscall on socketcall architectures unless
-   it was added at the same time as the socketcall support or can be
-   assumed to be present.  */
-#if defined __ASSUME_SOCKETCALL \
-    && !defined __ASSUME_RECVMMSG_SYSCALL_WITH_SOCKETCALL \
-    && !defined __ASSUME_RECVMMSG_SYSCALL
-# undef __NR_recvmmsg
-#endif
+#include <socketcall.h>
+#include <shlib-compat.h>
 
-#ifdef __NR_recvmmsg
+#ifdef __ASSUME_RECVMMSG_SYSCALL
 int
 recvmmsg (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags,
 	  struct timespec *tmo)
 {
   return SYSCALL_CANCEL (recvmmsg, fd, vmessages, vlen, flags, tmo);
 }
-#elif defined __NR_socketcall
-# include <socketcall.h>
-# ifdef __ASSUME_RECVMMSG_SOCKETCALL
+#elif defined __ASSUME_RECVMMSG_SYSCALL_WITH_SOCKETCALL
 int
 recvmmsg (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags,
 	  struct timespec *tmo)
 {
   return SOCKETCALL_CANCEL (recvmmsg, fd, vmessages, vlen, flags, tmo);
 }
-# else
+#elif defined __ASSUME_SOCKETCALL
 static int have_recvmmsg;
 
 int
@@ -87,7 +74,6 @@  recvmmsg (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags,
   __set_errno (ENOSYS);
   return -1;
 }
-# endif /* __ASSUME_RECVMMSG_SOCKETCALL  */
-#else
+#else /* __ASSUME_RECVMMSG_SOCKETCALL  */
 # include <socket/recvmmsg.c>
 #endif
diff --git a/sysdeps/unix/sysv/linux/s390/kernel-features.h b/sysdeps/unix/sysv/linux/s390/kernel-features.h
index b3edee4..4656c4a 100644
--- a/sysdeps/unix/sysv/linux/s390/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/s390/kernel-features.h
@@ -19,6 +19,8 @@ 
 
 /* S/390 uses socketcall.  */
 #define __ASSUME_SOCKETCALL		1
+#define __ASSUME_RECVMMSG_SYSCALL_WITH_SOCKETCALL	1
+#define __ASSUME_SENDMMSG_SYSCALL_WITH_SOCKETCALL	1
 
 /* Direct socketcalls available with kernel 4.3.  */
 #if __LINUX_KERNEL_VERSION >= 0x040300
diff --git a/sysdeps/unix/sysv/linux/sendmmsg.c b/sysdeps/unix/sysv/linux/sendmmsg.c
index 6e0d46b..37f0ec9 100644
--- a/sysdeps/unix/sysv/linux/sendmmsg.c
+++ b/sysdeps/unix/sysv/linux/sendmmsg.c
@@ -16,23 +16,11 @@ 
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-#include <errno.h>
 #include <sys/socket.h>
-
 #include <sysdep-cancel.h>
-#include <sys/syscall.h>
-#include <kernel-features.h>
-
-/* Do not use the sendmmsg syscall on socketcall architectures unless
-   it was added at the same time as the socketcall support or can be
-   assumed to be present.  */
-#if defined __ASSUME_SOCKETCALL \
-    && !defined __ASSUME_SENDMMSG_SYSCALL_WITH_SOCKETCALL \
-    && !defined __ASSUME_SENDMMSG_SYSCALL
-# undef __NR_sendmmsg
-#endif
+#include <socketcall.h>
 
-#ifdef __NR_sendmmsg
+#ifdef __ASSUME_SENDMMSG_SYSCALL
 int
 __sendmmsg (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags)
 {
@@ -40,15 +28,15 @@  __sendmmsg (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags)
 }
 libc_hidden_def (__sendmmsg)
 weak_alias (__sendmmsg, sendmmsg)
-#elif defined __NR_socketcall
-# include <socketcall.h>
-# ifdef __ASSUME_SENDMMSG_SOCKETCALL
+#elif defined __ASSUME_SENDMMSG_SYSCALL_WITH_SOCKETCALL
 int
 __sendmmsg (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags)
 {
   return SOCKETCALL_CANCEL (sendmmsg, fd, vmessages, vlen, flags);
 }
-# else
+libc_hidden_def (__sendmmsg)
+weak_alias (__sendmmsg, sendmmsg)
+#elif defined __ASSUME_SOCKETCALL
 static int have_sendmmsg;
 
 int
@@ -85,9 +73,8 @@  __sendmmsg (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags)
   __set_errno (ENOSYS);
   return -1;
 }
-# endif /* __ASSUME_SENDMMSG_SOCKETCALL  */
 libc_hidden_def (__sendmmsg)
 weak_alias (__sendmmsg, sendmmsg)
-#else
+#else /* __ASSUME_SENDMMSG_SOCKETCALL  */
 # include <socket/sendmmsg.c>
 #endif
diff --git a/sysdeps/unix/sysv/linux/sparc/kernel-features.h b/sysdeps/unix/sysv/linux/sparc/kernel-features.h
index 386f230..486036d 100644
--- a/sysdeps/unix/sysv/linux/sparc/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/sparc/kernel-features.h
@@ -23,12 +23,6 @@ 
 /* The accept4 syscall was added for SPARC in 2.6.28.  */
 #define __ASSUME_ACCEPT4_SYSCALL_WITH_SOCKETCALL	1
 
-/* The recvmmsg syscall was added for SPARC in 2.6.33.  */
-#define __ASSUME_RECVMMSG_SYSCALL_WITH_SOCKETCALL	1
-
-/* The sendmmsg syscall was added for SPARC in 3.0.  */
-#define __ASSUME_SENDMMSG_SYSCALL_WITH_SOCKETCALL	1
-
 #include_next <kernel-features.h>
 
 /* 32-bit SPARC kernels do not support