Fix __ASSUME_ACCEPT4 issues (bug 16609).

In <https://sourceware.org/ml/libc-alpha/2013-12/msg00008.html>,
Aurelien noted issues with the definition of __ASSUME_ACCEPT4, which I
discussed in more detail in
<https://sourceware.org/ml/libc-alpha/2013-12/msg00014.html>; these
are now bug 16609.

As previously noted, __ASSUME_ACCEPT4 is used in two ways:

* In OS-independent code, to mean "accept4 can be assumed to work
  rather than fail with ENOSYS".  It doesn't matter whether it's
  implemented with socketcall or a separate syscall.

* In Linux-specific code, to mean "the socketcall multiplex syscall
  can be assumed to handle the accept4 operation.  When used in
  Linux-specific code, it *never* refers to anything relating to the
  accept4 syscall, only to the socketcall multiplexer.

This patch splits the macro into separate __ASSUME_ACCEPT4_SOCKETCALL,
__ASSUME_ACCEPT4_SYSCALL and __ASSUME_ACCEPT4 to clarify the different
cases involved.  A macro __ASSUME_SOCKETCALL is added for convenience
in writing logic relating to all socketcall architectures.  In
addition, to address the issue of architectures where socketcall
support for accept4 was added before a separate syscall was added (and
so the separate syscall should not be used unless known to be present
or fallback to socketcall is available), a fourth macro
__ASSUME_ACCEPT4_SYSCALL_WITH_SOCKETCALL is added to indicate that the
syscall became available at the same time as socketcall support.  This
is then used in the relevant places in a conditional determining
whether to undefine __NR_accept4 (the simple approach to avoiding the
syscall's presence causing problems; I didn't try to implement runtime
fallback from the syscall to socketcall).

Architecture-specific note: alpha defined __ASSUME_ACCEPT4 for 2.6.33
and later, but actually the syscall was added for alpha in 3.2, so
this patch uses the correct condition for __ASSUME_ACCEPT4_SYSCALL
there.

Tested x86_64, including that disassembly of the installed shared
libraries is unchanged by this patch.

	[BZ #16609]
	* sysdeps/unix/sysv/linux/kernel-features.h [__i386__ ||
	__powerpc__ || __s390__ || __sh__ || __sparc__]
	(__ASSUME_SOCKETCALL): Define.
	[__LINUX_KERNEL_VERSION && __ASSUME_SOCKETCALL]
	(__ASSUME_ACCEPT4_SOCKETCALL): Likewise.
	[(__LINUX_KERNEL_VERSION >= 0x02061c && (__x86_64__ || __sparc__))
	|| (__LINUX_KERNEL_VERSION >= 0x020625 && (__powerpc__ ||
	__sh__))] (__ASSUME_ACCEPT4_SYSCALL): Likewise.
	[__sparc__] (__ASSUME_ACCEPT4_SYSCALL_WITH_SOCKETCALL): Likewise.
	[__ASSUME_ACCEPT4_SOCKETCALL || __ASSUME_ACCEPT4_SYSCALL]
	(__ASSUME_ACCEPT4): Define instead of using previous
	[__LINUX_KERNEL_VERSION >= 0x02061c && (__i386__ || __x86_64__ ||
	__powerpc__ || __sparc__ || __s390__)] condition.
	* sysdeps/unix/sysv/linux/aarch64/kernel-features.h
	(__ASSUME_ACCEPT4): Change to __ASSUME_ACCEPT4_SYSCALL.
	* sysdeps/unix/sysv/linux/accept4.c [__ASSUME_SOCKETCALL &&
	!__ASSUME_ACCEPT4_SYSCALL_WITH_SOCKETCALL &&
	!__ASSUME_ACCEPT4_SYSCALL] (__NR_accept4): Undefine.
	[!__ASSUME_ACCEPT4]: Change condition to
	[!__ASSUME_ACCEPT4_SOCKETCALL].
	* sysdeps/unix/sysv/linux/alpha/kernel-features.h
	(__ASSUME_ACCEPT4): Change to __ASSUME_ACCEPT4_SYSCALL.  Correct
	condition to [__LINUX_KERNEL_VERSION >= 0x030200].
	* sysdeps/unix/sysv/linux/arm/kernel-features.h
	[__LINUX_KERNEL_VERSION >= 0x020624] (__ASSUME_ACCEPT4): Change to
	__ASSUME_ACCEPT4_SYSCALL.
	* sysdeps/unix/sysv/linux/i386/accept4.S [__ASSUME_ACCEPT4]:
	Change conditions to [__ASSUME_ACCEPT4_SOCKETCALL].
	* sysdeps/unix/sysv/linux/ia64/kernel-features.h
	[__LINUX_KERNEL_VERSION >= 0x030300] (__ASSUME_ACCEPT4): Change to
	__ASSUME_ACCEPT4_SYSCALL.
	* sysdeps/unix/sysv/linux/internal_accept4.S [__ASSUME_SOCKETCALL
	&& !__ASSUME_ACCEPT4_SYSCALL_WITH_SOCKETCALL &&
	!__ASSUME_ACCEPT4_SYSCALL] (__NR_accept4): Undefine.
	[__ASSUME_ACCEPT4]: Change condition to
	[__ASSUME_ACCEPT4_SOCKETCALL].
	* sysdeps/unix/sysv/linux/m68k/kernel-features.h
	(__ASSUME_SOCKETCALL): Define.
	[__LINUX_KERNEL_VERSION >= 0x02061c] (__ASSUME_ACCEPT4): Remove.
	* sysdeps/unix/sysv/linux/microblaze/kernel-features.h
	(__ASSUME_SOCKETCALL): Define.
	(__ASSUME_ACCEPT4): Remove.
	[__LINUX_KERNEL_VERSION >= 0x020621] (__ASSUME_ACCEPT4_SYSCALL):
	Define.
	* sysdeps/unix/sysv/linux/mips/kernel-features.h
	[__LINUX_KERNEL_VERSION >= 0x02061f] (__ASSUME_ACCEPT4_SYSCALL):
	Likewise.
	* sysdeps/unix/sysv/linux/tile/kernel-features.h
	(__ASSUME_ACCEPT4): Change to __ASSUME_ACCEPT4_SYSCALL.

	* sysdeps/unix/sysv/linux/hppa/kernel-features.h
	[__LINUX_KERNEL_VERSION >= 0x020622] (__ASSUME_ACCEPT4_SYSCALL):
	Define.

1 files changed, 40 insertions, 4 deletions

diff --git a/sysdeps/unix/sysv/linux/kernel-features.h b/sysdeps/unix/sysv/linux/kernel-features.h
index 784f4dd491..b6d7714073 100644
--- a/sysdeps/unix/sysv/linux/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/kernel-features.h
@@ -40,6 +40,18 @@
 /* The sendfile syscall was introduced in 2.2.0.  */
 #define __ASSUME_SENDFILE		1
 
+/* Some architectures use the socketcall multiplexer for some or all
+   socket-related operations, via a socket.S file in glibc, instead of
+   separate syscalls.  __ASSUME_SOCKETCALL is defined for such
+   architectures.  */
+#if defined __i386__ \
+    || defined __powerpc__ \
+    || defined __s390__ \
+    || defined __sh__ \
+    || defined __sparc__
+# define __ASSUME_SOCKETCALL		1
+#endif
+
 /* Linux 2.3.39 introduced IPC64.  Except for powerpc.  Linux 2.4.0 on
    PPC introduced a correct IPC64.  But PowerPC64 does not support a
    separate 64-bit syscall, already 64-bit.  */
@@ -164,10 +176,34 @@
 # define __ASSUME_DUP3		1
 #endif
 
-/* Support for the accept4 syscall was added in 2.6.28.  */
-#if __LINUX_KERNEL_VERSION >= 0x02061c \
-    && (defined __i386__ || defined __x86_64__ || defined __powerpc__ \
-	|| defined __sparc__ || defined __s390__)
+/* Support for accept4 functionality was added in 2.6.28, but for some
+   architectures using a separate syscall rather than socketcall that
+   syscall was only added later, and some architectures first had
+   socketcall support then a separate syscall.  Define
+   __ASSUME_ACCEPT4_SOCKETCALL if glibc uses socketcall on this
+   architecture and accept4 is available through socketcall,
+   __ASSUME_ACCEPT4_SYSCALL if it is available through a separate
+   syscall, __ASSUME_ACCEPT4_SYSCALL_WITH_SOCKETCALL if it became
+   available through a separate syscall at the same time as through
+   socketcall, and __ASSUME_ACCEPT4 if the accept4 function is known
+   to work.  */
+#if __LINUX_KERNEL_VERSION >= 0x02061c && defined __ASSUME_SOCKETCALL
+# define __ASSUME_ACCEPT4_SOCKETCALL	1
+#endif
+
+/* The accept4 syscall was added for x86_64 and SPARC in 2.6.28, and
+   for PowerPC and SH in 2.6.37.  */
+#if (__LINUX_KERNEL_VERSION >= 0x02061c			\
+     && (defined __x86_64__ || defined __sparc__))	\
+    || (__LINUX_KERNEL_VERSION >= 0x020625		\
+	&& (defined __powerpc__ || defined __sh__))
+# define __ASSUME_ACCEPT4_SYSCALL	1
+#endif
+#ifdef __sparc__
+# define __ASSUME_ACCEPT4_SYSCALL_WITH_SOCKETCALL	1
+#endif
+
+#if defined __ASSUME_ACCEPT4_SOCKETCALL || defined __ASSUME_ACCEPT4_SYSCALL
 # define __ASSUME_ACCEPT4	1
 #endif