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Merge tag 'clone3-v5.3' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux
Pull clone3 system call from Christian Brauner:
"This adds the clone3 syscall which is an extensible successor to clone
after we snagged the last flag with CLONE_PIDFD during the 5.2 merge
window for clone(). It cleanly supports all of the flags from clone()
and thus all legacy workloads.
There are few user visible differences between clone3 and clone.
First, CLONE_DETACHED will cause EINVAL with clone3 so we can reuse
this flag. Second, the CSIGNAL flag is deprecated and will cause
EINVAL to be reported. It is superseeded by a dedicated "exit_signal"
argument in struct clone_args thus freeing up even more flags. And
third, clone3 gives CLONE_PIDFD a dedicated return argument in struct
clone_args instead of abusing CLONE_PARENT_SETTID's parent_tidptr
argument.
The clone3 uapi is designed to be easy to handle on 32- and 64 bit:
/* uapi */
struct clone_args {
__aligned_u64 flags;
__aligned_u64 pidfd;
__aligned_u64 child_tid;
__aligned_u64 parent_tid;
__aligned_u64 exit_signal;
__aligned_u64 stack;
__aligned_u64 stack_size;
__aligned_u64 tls;
};
and a separate kernel struct is used that uses proper kernel typing:
/* kernel internal */
struct kernel_clone_args {
u64 flags;
int __user *pidfd;
int __user *child_tid;
int __user *parent_tid;
int exit_signal;
unsigned long stack;
unsigned long stack_size;
unsigned long tls;
};
The system call comes with a size argument which enables the kernel to
detect what version of clone_args userspace is passing in. clone3
validates that any additional bytes a given kernel does not know about
are set to zero and that the size never exceeds a page.
A nice feature is that this patchset allowed us to cleanup and
simplify various core kernel codepaths in kernel/fork.c by making the
internal _do_fork() function take struct kernel_clone_args even for
legacy clone().
This patch also unblocks the time namespace patchset which wants to
introduce a new CLONE_TIMENS flag.
Note, that clone3 has only been wired up for x86{_32,64}, arm{64}, and
xtensa. These were the architectures that did not require special
massaging.
Other architectures treat fork-like system calls individually and
after some back and forth neither Arnd nor I felt confident that we
dared to add clone3 unconditionally to all architectures. We agreed to
leave this up to individual architecture maintainers. This is why
there's an additional patch that introduces __ARCH_WANT_SYS_CLONE3
which any architecture can set once it has implemented support for
clone3. The patch also adds a cond_syscall(clone3) for architectures
such as nios2 or h8300 that generate their syscall table by simply
including asm-generic/unistd.h. The hope is to get rid of
__ARCH_WANT_SYS_CLONE3 and cond_syscall() rather soon"
* tag 'clone3-v5.3' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
arch: handle arches who do not yet define clone3
arch: wire-up clone3() syscall
fork: add clone3
52 lines
1.4 KiB
C
52 lines
1.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Copyright (C) 2012 ARM Ltd.
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*/
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#ifdef CONFIG_COMPAT
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#define __ARCH_WANT_COMPAT_STAT64
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#define __ARCH_WANT_SYS_GETHOSTNAME
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#define __ARCH_WANT_SYS_PAUSE
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#define __ARCH_WANT_SYS_GETPGRP
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#define __ARCH_WANT_SYS_NICE
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#define __ARCH_WANT_SYS_SIGPENDING
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#define __ARCH_WANT_SYS_SIGPROCMASK
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#define __ARCH_WANT_COMPAT_SYS_SENDFILE
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#define __ARCH_WANT_SYS_UTIME32
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#define __ARCH_WANT_SYS_FORK
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#define __ARCH_WANT_SYS_VFORK
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/*
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* Compat syscall numbers used by the AArch64 kernel.
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*/
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#define __NR_compat_restart_syscall 0
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#define __NR_compat_exit 1
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#define __NR_compat_read 3
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#define __NR_compat_write 4
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#define __NR_compat_gettimeofday 78
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#define __NR_compat_sigreturn 119
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#define __NR_compat_rt_sigreturn 173
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#define __NR_compat_clock_getres 247
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#define __NR_compat_clock_gettime 263
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#define __NR_compat_clock_gettime64 403
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#define __NR_compat_clock_getres_time64 406
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/*
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* The following SVCs are ARM private.
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*/
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#define __ARM_NR_COMPAT_BASE 0x0f0000
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#define __ARM_NR_compat_cacheflush (__ARM_NR_COMPAT_BASE + 2)
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#define __ARM_NR_compat_set_tls (__ARM_NR_COMPAT_BASE + 5)
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#define __ARM_NR_COMPAT_END (__ARM_NR_COMPAT_BASE + 0x800)
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#define __NR_compat_syscalls 436
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#endif
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#define __ARCH_WANT_SYS_CLONE
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#define __ARCH_WANT_SYS_CLONE3
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#ifndef __COMPAT_SYSCALL_NR
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#include <uapi/asm/unistd.h>
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#endif
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#define NR_syscalls (__NR_syscalls)
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