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.

12 files changed, 87 insertions, 22 deletions

diff --git a/sysdeps/unix/sysv/linux/aarch64/kernel-features.h b/sysdeps/unix/sysv/linux/aarch64/kernel-features.h
index c736eb9c0e..222b61c02c 100644
--- a/sysdeps/unix/sysv/linux/aarch64/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/aarch64/kernel-features.h
@@ -24,7 +24,7 @@
 /* AArch64 support starts with 3.7.0, guaranteeing many kernel
    features.  */
 
-#define __ASSUME_ACCEPT4                1
+#define __ASSUME_ACCEPT4_SYSCALL        1
 #define __ASSUME_DUP3                   1
 #define __ASSUME_EVENTFD2		1
 #define __ASSUME_IN_NONBLOCK            1
diff --git a/sysdeps/unix/sysv/linux/accept4.c b/sysdeps/unix/sysv/linux/accept4.c
index 019e96b677..a017224eef 100644
--- a/sysdeps/unix/sysv/linux/accept4.c
+++ b/sysdeps/unix/sysv/linux/accept4.c
@@ -24,6 +24,14 @@
 #include <sys/syscall.h>
 #include <kernel-features.h>
 
+/* Do not use the accept4 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_ACCEPT4_SYSCALL_WITH_SOCKETCALL \
+    && !defined __ASSUME_ACCEPT4_SYSCALL
+# undef __NR_accept4
+#endif
 
 #ifdef __NR_accept4
 int
@@ -42,7 +50,7 @@ accept4 (int fd, __SOCKADDR_ARG addr, socklen_t *addr_len, int flags)
   return result;
 }
 #elif defined __NR_socketcall
-# ifndef __ASSUME_ACCEPT4
+# ifndef __ASSUME_ACCEPT4_SOCKETCALL
 extern int __internal_accept4 (int fd, __SOCKADDR_ARG addr,
 			       socklen_t *addr_len, int flags)
      attribute_hidden;
@@ -83,7 +91,8 @@ accept4 (int fd, __SOCKADDR_ARG addr, socklen_t *addr_len, int flags)
   return -1;
 }
 # else
-/* When __ASSUME_ACCEPT4 accept4 is defined in internal_accept4.S.  */
+/* When __ASSUME_ACCEPT4_SOCKETCALL accept4 is defined in
+   internal_accept4.S.  */
 # endif
 #else
 int
diff --git a/sysdeps/unix/sysv/linux/alpha/kernel-features.h b/sysdeps/unix/sysv/linux/alpha/kernel-features.h
index 7c38854c70..8cceb34592 100644
--- a/sysdeps/unix/sysv/linux/alpha/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/alpha/kernel-features.h
@@ -42,9 +42,9 @@
 # define __ASSUME_SIGNALFD4 1
 #endif
 
-/* Support for accept4 was added for alpha after 2.6.33-rc1.  */
-#if __LINUX_KERNEL_VERSION >= 0x020621
-# define __ASSUME_ACCEPT4      1
+/* Support for accept4 was added for alpha in 3.2.  */
+#if __LINUX_KERNEL_VERSION >= 0x030200
+# define __ASSUME_ACCEPT4_SYSCALL      1
 #endif
 
 #include_next <kernel-features.h>
diff --git a/sysdeps/unix/sysv/linux/arm/kernel-features.h b/sysdeps/unix/sysv/linux/arm/kernel-features.h
index 9d7ef877af..304f88d4a6 100644
--- a/sysdeps/unix/sysv/linux/arm/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/arm/kernel-features.h
@@ -33,7 +33,7 @@
 
 /* Support for the accept4 syscall was added in 2.6.36.  */
 #if __LINUX_KERNEL_VERSION >= 0x020624
-# define __ASSUME_ACCEPT4	1
+# define __ASSUME_ACCEPT4_SYSCALL	1
 #endif
 
 #include_next <kernel-features.h>
diff --git a/sysdeps/unix/sysv/linux/i386/accept4.S b/sysdeps/unix/sysv/linux/i386/accept4.S
index cdce27b57f..20213991ca 100644
--- a/sysdeps/unix/sysv/linux/i386/accept4.S
+++ b/sysdeps/unix/sysv/linux/i386/accept4.S
@@ -23,7 +23,7 @@
 #define EINVAL	22
 #define ENOSYS	38
 
-#ifdef __ASSUME_ACCEPT4
+#ifdef __ASSUME_ACCEPT4_SOCKETCALL
 # define errlabel SYSCALL_ERROR_LABEL
 #else
 # define errlabel .Lerr
@@ -114,7 +114,7 @@ ENTRY (__libc_accept4)
 	ret
 #endif
 
-#ifndef __ASSUME_ACCEPT4
+#ifndef __ASSUME_ACCEPT4_SOCKETCALL
 	/* The kernel returns -EINVAL for unknown socket operations.
 	   We need to convert that error to an ENOSYS error.  */
 .Lerr:	cmpl $-EINVAL, %eax
diff --git a/sysdeps/unix/sysv/linux/ia64/kernel-features.h b/sysdeps/unix/sysv/linux/ia64/kernel-features.h
index 340f679320..5c7c4eb8a5 100644
--- a/sysdeps/unix/sysv/linux/ia64/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/ia64/kernel-features.h
@@ -49,7 +49,7 @@
 
 /* Support for the accept4 syscall was added in 3.3.  */
 #if __LINUX_KERNEL_VERSION >= 0x030300
-# define __ASSUME_ACCEPT4	1
+# define __ASSUME_ACCEPT4_SYSCALL	1
 #endif
 
 #include_next <kernel-features.h>
diff --git a/sysdeps/unix/sysv/linux/internal_accept4.S b/sysdeps/unix/sysv/linux/internal_accept4.S
index ffc553624c..f0c61b55b1 100644
--- a/sysdeps/unix/sysv/linux/internal_accept4.S
+++ b/sysdeps/unix/sysv/linux/internal_accept4.S
@@ -1,8 +1,18 @@
 #include <kernel-features.h>
 #include <sys/syscall.h>
+
+/* Do not use the accept4 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_ACCEPT4_SYSCALL_WITH_SOCKETCALL \
+    && !defined __ASSUME_ACCEPT4_SYSCALL
+# undef __NR_accept4
+#endif
+
 #if !defined __NR_accept4 && defined __NR_socketcall
 # define socket	accept4
-# ifdef __ASSUME_ACCEPT4
+# ifdef __ASSUME_ACCEPT4_SOCKETCALL
 #  define __socket accept4
 # else
 #  define __socket __internal_accept4
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
 
diff --git a/sysdeps/unix/sysv/linux/m68k/kernel-features.h b/sysdeps/unix/sysv/linux/m68k/kernel-features.h
index 3b05e96610..cb8915f127 100644
--- a/sysdeps/unix/sysv/linux/m68k/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/m68k/kernel-features.h
@@ -17,6 +17,9 @@
    License along with the GNU C Library.  If not, see
    <http://www.gnu.org/licenses/>.  */
 
+/* m68k uses socketcall.  */
+#define __ASSUME_SOCKETCALL	1
+
 /* Many syscalls were added in 2.6.10 for m68k.  */
 #define __ASSUME_UTIMES	1
 
@@ -35,11 +38,6 @@
 # define __ASSUME_DUP3		1
 #endif
 
-/* Support for the accept4 syscall was added in 2.6.28.  */
-#if __LINUX_KERNEL_VERSION >= 0x02061c
-# define __ASSUME_ACCEPT4	1
-#endif
-
 #include_next <kernel-features.h>
 
 /* These syscalls were added only in 3.0 for m68k.  */
diff --git a/sysdeps/unix/sysv/linux/microblaze/kernel-features.h b/sysdeps/unix/sysv/linux/microblaze/kernel-features.h
index dcc0ac9bbc..413b4a0b90 100644
--- a/sysdeps/unix/sysv/linux/microblaze/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/microblaze/kernel-features.h
@@ -16,6 +16,9 @@
    <http://www.gnu.org/licenses/>.  */
 
 
+/* MicroBlaze uses socketcall.  */
+#define __ASSUME_SOCKETCALL	1
+
 /* MicroBlaze glibc support starts with 2.6.30, guaranteeing many kernel features.  */
 #define __ASSUME_UTIMES         1
 #define __ASSUME_O_CLOEXEC      1
@@ -24,7 +27,11 @@
 #define __ASSUME_PIPE2          1
 #define __ASSUME_EVENTFD2       1
 #define __ASSUME_SIGNALFD4      1
-#define __ASSUME_ACCEPT4        1
 #define __ASSUME_DUP3           1
 
+/* Support for the accept4 syscall was added in 2.6.33.  */
+#if __LINUX_KERNEL_VERSION >= 0x020621
+# define __ASSUME_ACCEPT4_SYSCALL        1
+#endif
+
 #include_next <kernel-features.h>
diff --git a/sysdeps/unix/sysv/linux/mips/kernel-features.h b/sysdeps/unix/sysv/linux/mips/kernel-features.h
index 1c83ee558d..94deaf9205 100644
--- a/sysdeps/unix/sysv/linux/mips/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/mips/kernel-features.h
@@ -31,6 +31,11 @@
 # define __ASSUME_SIGNALFD4	1
 #endif
 
+/* Support for the accept4 syscall was added in 2.6.31.  */
+#if __LINUX_KERNEL_VERSION >= 0x02061f
+# define __ASSUME_ACCEPT4_SYSCALL	1
+#endif
+
 #include_next <kernel-features.h>
 
 /* The n32 syscall ABI did not have a getdents64 syscall until
diff --git a/sysdeps/unix/sysv/linux/tile/kernel-features.h b/sysdeps/unix/sysv/linux/tile/kernel-features.h
index 5b811288ee..e339e7a5b2 100644
--- a/sysdeps/unix/sysv/linux/tile/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/tile/kernel-features.h
@@ -25,7 +25,7 @@
 #define __ASSUME_PIPE2			1
 #define __ASSUME_EVENTFD2		1
 #define __ASSUME_SIGNALFD4		1
-#define __ASSUME_ACCEPT4		1
+#define __ASSUME_ACCEPT4_SYSCALL	1
 #define __ASSUME_DUP3			1
 
 #include_next <kernel-features.h>