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glibc/sysdeps/unix/sysv/linux/kernel-features.h
Joseph Myers 47c5adebd2 Correct robust mutex / PI futex kernel assumptions (bug 9894). 
This patch continues fixing __ASSUME_* issues in preparation for
moving to a 2.6.32 minimum kernel version by addressing assumptions on
robust mutex and PI futex support availability.  Those assumptions are
bug 9894, but to be clear this patch does not address all the issues
from that bug about wrong version assumptions, only those still
applicable for --enable-kernel=2.6.32 or later (with the expectation
that the move to that minimum kernel will obsolete the other parts of
the bug).  The patch is independent of
<https://sourceware.org/ml/libc-alpha/2014-03/msg00585.html>, my other
pending-review patch preparing for the kernel version change; the two
together complete all the changes I believe are needed in preparation
regarding any macro in sysdeps/unix/sysv/linux/kernel-features.h that
would be affected by such a change.  (I have not checked the
correctness of macros whose conditions are unaffected by such a
change, or macros only defined in other kernel-features.h files.)

As discussed in that bug, robust mutexes and PI futexes need
futex_atomic_cmpxchg_inatomic to be implemented, in addition to
certain syscalls needed for robust mutexes (and
architecture-independent kernel pieces for all the features in
question).  That is, as I understand it, they need
futex_atomic_cmpxchg_inatomic to *work* (not return an ENOSYS error).

The issues identified in my analysis relate to ARM, M68K, MicroBlaze,
MIPS and SPARC.

On ARM, whether futex_atomic_cmpxchg_inatomic works depends on the
kernel configuration.  As of 3.13, the condition for *not* working is
CONFIG_CPU_USE_DOMAINS && CONFIG_SMP.  As of 2.6.32 it was simply
CONFIG_SMP that meant the feature was not implemented.  I don't know
if there are any circumstances in which we can say "we can assume a
userspace glibc binary built with these options will never run on a
kernel with the problematic configuration", but at least for now I'm
just undefining the relevant __ASSUME_* macros for ARM.

On M68K, two of the three macros are undefined for kernels before
3.10, but as far as I can see __ASSUME_FUTEX_LOCK_PI is in the same
group needing futex_atomic_cmpxchg_inatomic support and so should be
undefined as well.

On MicroBlaze the required support was added in 2.6.33.

On MIPS, the support depends on cpu_has_llsc in the kernel - that is,
actual hardware LL/SC support (GCC and glibc for MIPS GNU/Linux rely
on the instructions being supported in some way, but it may be kernel
emulation; futex_atomic_cmpxchg_inatomic doesn't work with that
emulation).  The same condition as in GCC for indicating LL/SC support
may not be available is used for undefining the macros in glibc,
__mips == 1 || defined _MIPS_ARCH_R5900.  (Maybe we could in fact
desupport MIPS processors without the hardware support in glibc.)

On SPARC, 32-bit kernels don't support futex_atomic_cmpxchg_inatomic;
__arch64__ || __sparc_v9__ is used as the condition for binaries that
won't run on 32-bit kernels.

This patch is not tested beyond the sanity check of an x86_64 build.

	[BZ #9894]
	* sysdeps/unix/sysv/linux/kernel-features.h
	[__sparc__ && !__arch64__ && !__sparc_v9__]
	(__ASSUME_SET_ROBUST_LIST): Do not define.
	[__sparc__ && !__arch64__ && !__sparc_v9__]
	(__ASSUME_FUTEX_LOCK_PI): Likewise.
	[__sparc__ && !__arch64__ && !__sparc_v9__] (__ASSUME_REQUEUE_PI):
	Likewise.
	* sysdeps/unix/sysv/linux/arm/kernel-features.h
	(__ASSUME_FUTEX_LOCK_PI): Undefine.
	(__ASSUME_REQUEUE_PI): Likewise.
	(__ASSUME_SET_ROBUST_LIST): Likewise.
	* sysdeps/unix/sysv/linux/m68k/kernel-features.h
	[__LINUX_KERNEL_VERSION < 0x030a00] (__ASSUME_FUTEX_LOCK_PI):
	Undefine.
	* sysdeps/unix/sysv/linux/microblaze/kernel-features.h
	[__LINUX_KERNEL_VERSION < 0x020621] (__ASSUME_FUTEX_LOCK_PI):
	Likewise.
	[__LINUX_KERNEL_VERSION < 0x020621] (__ASSUME_REQUEUE_PI):
	Likewise.
	[__LINUX_KERNEL_VERSION < 0x020621] (__ASSUME_SET_ROBUST_LIST):
	Likewise.
	* sysdeps/unix/sysv/linux/mips/kernel-features.h
	[__mips == 1 || _MIPS_ARCH_R5900] (__ASSUME_FUTEX_LOCK_PI):
	Undefine.
	[__mips == 1 || _MIPS_ARCH_R5900] (__ASSUME_REQUEUE_PI): Likewise.
	[__mips == 1 || _MIPS_ARCH_R5900] (__ASSUME_SET_ROBUST_LIST):
	Likewise.
2014-03-31 12:55:18 +00:00

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/* Set flags signalling availability of kernel features based on given
kernel version number.
Copyright (C) 1999-2014 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/>. */
/* This file must not contain any C code. At least it must be protected
to allow using the file also in assembler files. */
#ifndef __LINUX_KERNEL_VERSION
/* We assume the worst; all kernels should be supported. */
# define __LINUX_KERNEL_VERSION 0
#endif
/* We assume for __LINUX_KERNEL_VERSION the same encoding used in
linux/version.h. I.e., the major, minor, and subminor all get a
byte with the major number being in the highest byte. This means
we can do numeric comparisons.
In the following we will define certain symbols depending on
whether the describes kernel feature is available in the kernel
version given by __LINUX_KERNEL_VERSION. We are not always exactly
recording the correct versions in which the features were
introduced. If somebody cares these values can afterwards be
corrected. */
/* 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. */
#ifndef __powerpc64__
# define __ASSUME_IPC64 1
#endif
/* The changed st_ino field appeared in 2.4.0-test6. However, SH is lame,
and still does not have a 64-bit inode field. */
#ifndef __sh__
# define __ASSUME_ST_INO_64_BIT 1
#endif
/* The getdents64 syscall was introduced in 2.4.0-test7 (but later for
MIPS n32). */
#define __ASSUME_GETDENTS64_SYSCALL 1
/* The statfs64 syscalls are available in 2.5.74 (but not for alpha). */
#define __ASSUME_STATFS64 1
/* The utimes syscall has been available for some architectures
forever. For x86 it was introduced after 2.5.75, for x86-64,
ppc, and ppc64 it was introduced in 2.6.0-test3, for s390 it was
introduced in 2.6.21-rc5. */
#if defined __sparc__ \
|| defined __i386__ \
|| defined __x86_64__ \
|| defined __powerpc__ \
|| defined __sh__ \
|| (defined __s390__ && __LINUX_KERNEL_VERSION >= 0x020616)
# define __ASSUME_UTIMES 1
#endif
/* pselect/ppoll were introduced just after 2.6.16-rc1. Due to the way
the kernel versions are advertised we can only rely on 2.6.17 to have
the code. On x86_64 and SH this appeared first in 2.6.19-rc1,
on ia64 in 2.6.22-rc1. */
#if __LINUX_KERNEL_VERSION >= 0x020611 \
&& ((!defined __x86_64__ && !defined __sh__) \
|| (__LINUX_KERNEL_VERSION >= 0x020613 \
&& (defined __x86_64__ || defined __sh__)))
# define __ASSUME_PSELECT 1
# define __ASSUME_PPOLL 1
#endif
/* The *at syscalls were introduced just after 2.6.16-rc1. Due to the way the
kernel versions are advertised we can only rely on 2.6.17 to have
the code. On PPC they were introduced in 2.6.17-rc1,
on SH in 2.6.19-rc1. */
#if __LINUX_KERNEL_VERSION >= 0x020611 \
&& (!defined __sh__ || __LINUX_KERNEL_VERSION >= 0x020613)
# define __ASSUME_ATFCTS 1
#endif
/* Support for inter-process robust mutexes was added in 2.6.17 (but
some architectures lack futex_atomic_cmpxchg_inatomic in some
configurations). */
#if __LINUX_KERNEL_VERSION >= 0x020611 \
&& (!defined __sh__ || __LINUX_KERNEL_VERSION >= 0x020613) \
&& !(defined __sparc__ && !defined __arch64__ && !defined __sparc_v9__)
# define __ASSUME_SET_ROBUST_LIST 1
#endif
/* Pessimistically assume that 2.6.18 introduced real handling of
large numbers of requests to readv and writev and that we don't
need a fallback. It likely worked for much longer. */
#if __LINUX_KERNEL_VERSION >= 0x020612
# define __ASSUME_COMPLETE_READV_WRITEV 1
#endif
/* Support for PI futexes was added in 2.6.18 (but some architectures
lack futex_atomic_cmpxchg_inatomic in some configurations). */
#if __LINUX_KERNEL_VERSION >= 0x020612 \
&& !(defined __sparc__ && !defined __arch64__ && !defined __sparc_v9__)
# define __ASSUME_FUTEX_LOCK_PI 1
#endif
/* Support for utimensat syscall was added in 2.6.22, on SH
only after 2.6.22-rc1. */
#if __LINUX_KERNEL_VERSION >= 0x020616 \
&& (!defined __sh__ || __LINUX_KERNEL_VERSION >= 0x020617)
# define __ASSUME_UTIMENSAT 1
#endif
/* Support for private futexes was added in 2.6.22. */
#if __LINUX_KERNEL_VERSION >= 0x020616
# define __ASSUME_PRIVATE_FUTEX 1
#endif
/* Support for fallocate was added in 2.6.23, on s390
only after 2.6.23-rc1. */
#if __LINUX_KERNEL_VERSION >= 0x020617 \
&& (!defined __s390__ || __LINUX_KERNEL_VERSION >= 0x020618)
# define __ASSUME_FALLOCATE 1
#endif
/* Support for various CLOEXEC and NONBLOCK flags was added for x86,
x86-64, PPC, IA-64, SPARC< and S390 in 2.6.23. */
#if __LINUX_KERNEL_VERSION >= 0x020617 \
&& (defined __i386__ || defined __x86_64__ || defined __powerpc__ \
|| defined __sparc__ || defined __s390__)
# define __ASSUME_O_CLOEXEC 1
#endif
/* From 2.6.23 onwards the value of ARG_MAX depends on the stack
size. */
#define __LINUX_ARG_MAX_STACK_BASED_MIN_KERNEL 0x020617
#if __LINUX_KERNEL_VERSION >= __LINUX_ARG_MAX_STACK_BASED_MIN_KERNEL
# define __ASSUME_ARG_MAX_STACK_BASED 1
#endif
/* Support for ADJ_OFFSET_SS_READ was added in 2.6.24. */
#if __LINUX_KERNEL_VERSION >= 0x020618
# define __ASSUME_ADJ_OFFSET_SS_READ 1
#endif
/* Support for various CLOEXEC and NONBLOCK flags was added for x86,
x86-64, PPC, IA-64, and SPARC in 2.6.27. */
#if __LINUX_KERNEL_VERSION >= 0x02061b \
&& (defined __i386__ || defined __x86_64__ || defined __powerpc__ \
|| defined __sparc__ || defined __s390__)
# define __ASSUME_SOCK_CLOEXEC 1
# define __ASSUME_IN_NONBLOCK 1
# define __ASSUME_PIPE2 1
# define __ASSUME_EVENTFD2 1
# define __ASSUME_SIGNALFD4 1
# define __ASSUME_DUP3 1
#endif
/* 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
/* Support for the FUTEX_CLOCK_REALTIME flag was added in 2.6.29. */
#if __LINUX_KERNEL_VERSION >= 0x02061d
# define __ASSUME_FUTEX_CLOCK_REALTIME 1
#endif
/* Support for the AT_RANDOM auxiliary vector entry was added in 2.6.29. */
#if __LINUX_KERNEL_VERSION >= 0x02061d
# define __ASSUME_AT_RANDOM 1
#endif
/* Support for preadv and pwritev was added in 2.6.30. */
#if __LINUX_KERNEL_VERSION >= 0x02061e
# define __ASSUME_PREADV 1
# define __ASSUME_PWRITEV 1
#endif
/* Support for FUTEX_*_REQUEUE_PI was added in 2.6.31 (but some
architectures lack futex_atomic_cmpxchg_inatomic in some
configurations). */
#if __LINUX_KERNEL_VERSION >= 0x02061f \
&& !(defined __sparc__ && !defined __arch64__ && !defined __sparc_v9__)
# define __ASSUME_REQUEUE_PI 1
#endif
/* Support for F_GETOWN_EX was introduced in 2.6.32. */
#if __LINUX_KERNEL_VERSION >= 0x020620
# define __ASSUME_F_GETOWN_EX 1
#endif
/* Support for recvmmsg functionality was added in 2.6.33. The macros
defined correspond to those for accept4. */
#if __LINUX_KERNEL_VERSION >= 0x020621 && defined __ASSUME_SOCKETCALL
# define __ASSUME_RECVMMSG_SOCKETCALL 1
#endif
/* The recvmmsg syscall was added for i386, x86_64 and SPARC in
2.6.33, and for PowerPC and SH in 2.6.37. */
#if (__LINUX_KERNEL_VERSION >= 0x020621 \
&& (defined __i386__ || defined __x86_64__ || defined __sparc__)) \
|| (__LINUX_KERNEL_VERSION >= 0x020625 \
&& (defined __powerpc__ || defined __sh__))
# define __ASSUME_RECVMMSG_SYSCALL 1
#endif
#if defined __i386__ || defined __sparc__
# define __ASSUME_RECVMMSG_SYSCALL_WITH_SOCKETCALL 1
#endif
#if defined __ASSUME_RECVMMSG_SOCKETCALL || defined __ASSUME_RECVMMSG_SYSCALL
# define __ASSUME_RECVMMSG 1
#endif
/* Support for /proc/self/task/$tid/comm and /proc/$pid/task/$tid/comm was
added in 2.6.33. */
#if __LINUX_KERNEL_VERSION >= 0x020621
# define __ASSUME_PROC_PID_TASK_COMM 1
#endif
/* statfs fills in f_flags since 2.6.36. */
#if __LINUX_KERNEL_VERSION >= 0x020624
# define __ASSUME_STATFS_F_FLAGS 1
#endif
/* prlimit64 is available in 2.6.36. */
#if __LINUX_KERNEL_VERSION >= 0x020624
# define __ASSUME_PRLIMIT64 1
#endif
/* Support for sendmmsg functionality was added in 3.0. The macros
defined correspond to those for accept4 and recvmmsg. */
#if __LINUX_KERNEL_VERSION >= 0x030000 && defined __ASSUME_SOCKETCALL
# define __ASSUME_SENDMMSG_SOCKETCALL 1
#endif
/* The sendmmsg syscall was added for i386, x86_64, PowerPC, SH and
SPARC in 3.0. */
#if __LINUX_KERNEL_VERSION >= 0x030000 \
&& (defined __i386__ || defined __x86_64__ || defined __powerpc__ \
|| defined __sh__ || defined __sparc__)
# define __ASSUME_SENDMMSG_SYSCALL 1
#endif
#if defined __i386__ || defined __powerpc__ || defined __sh__ \
|| defined __sparc__
# define __ASSUME_SENDMMSG_SYSCALL_WITH_SOCKETCALL 1
#endif
#if defined __ASSUME_SENDMMSG_SOCKETCALL || defined __ASSUME_SENDMMSG_SYSCALL
# define __ASSUME_SENDMMSG 1
#endif
/* getcpu is a syscall for x86-64 since 3.1. */
#if defined __x86_64__ && __LINUX_KERNEL_VERSION >= 0x030100
# define __ASSUME_GETCPU_SYSCALL 1
#endif
/* 2.6.29 removed the XFS restricted_chown sysctl, so it is pointless looking
for it in newer kernels. */
#if __LINUX_KERNEL_VERSION >= 0x02061d
# define __ASSUME_XFS_RESTRICTED_CHOWN 1
#endif
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