Lorenzo Stoakes
f08d0c3a71
It is useful to be able to utilise the pidfd mechanism to reference the current thread or process (from a userland point of view - thread group leader from the kernel's point of view). Therefore introduce PIDFD_SELF_THREAD to refer to the current thread, and PIDFD_SELF_THREAD_GROUP to refer to the current thread group leader. For convenience and to avoid confusion from userland's perspective we alias these: * PIDFD_SELF is an alias for PIDFD_SELF_THREAD - This is nearly always what the user will want to use, as they would find it surprising if for instance fd's were unshared()'d and they wanted to invoke pidfd_getfd() and that failed. * PIDFD_SELF_PROCESS is an alias for PIDFD_SELF_THREAD_GROUP - Most users have no concept of thread groups or what a thread group leader is, and from userland's perspective and nomenclature this is what userland considers to be a process. We adjust pidfd_get_task() and the pidfd_send_signal() system call with specific handling for this, implementing this functionality for process_madvise(), process_mrelease() (albeit, using it here wouldn't really make sense) and pidfd_send_signal(). Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Link: https://lore.kernel.org/r/24315a16a3d01a548dd45c7515f7d51c767e954e.1738268370.git.lorenzo.stoakes@oracle.com Signed-off-by: Christian Brauner <brauner@kernel.org>
107 lines
4.0 KiB
C
107 lines
4.0 KiB
C
/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
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#ifndef _UAPI_LINUX_PIDFD_H
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#define _UAPI_LINUX_PIDFD_H
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#include <linux/types.h>
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#include <linux/fcntl.h>
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#include <linux/ioctl.h>
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/* Flags for pidfd_open(). */
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#define PIDFD_NONBLOCK O_NONBLOCK
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#define PIDFD_THREAD O_EXCL
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/* Flags for pidfd_send_signal(). */
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#define PIDFD_SIGNAL_THREAD (1UL << 0)
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#define PIDFD_SIGNAL_THREAD_GROUP (1UL << 1)
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#define PIDFD_SIGNAL_PROCESS_GROUP (1UL << 2)
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/* Flags for pidfd_info. */
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#define PIDFD_INFO_PID (1UL << 0) /* Always returned, even if not requested */
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#define PIDFD_INFO_CREDS (1UL << 1) /* Always returned, even if not requested */
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#define PIDFD_INFO_CGROUPID (1UL << 2) /* Always returned if available, even if not requested */
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#define PIDFD_INFO_SIZE_VER0 64 /* sizeof first published struct */
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/*
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* The concept of process and threads in userland and the kernel is a confusing
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* one - within the kernel every thread is a 'task' with its own individual PID,
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* however from userland's point of view threads are grouped by a single PID,
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* which is that of the 'thread group leader', typically the first thread
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* spawned.
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*
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* To cut the Gideon knot, for internal kernel usage, we refer to
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* PIDFD_SELF_THREAD to refer to the current thread (or task from a kernel
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* perspective), and PIDFD_SELF_THREAD_GROUP to refer to the current thread
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* group leader...
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*/
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#define PIDFD_SELF_THREAD -10000 /* Current thread. */
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#define PIDFD_SELF_THREAD_GROUP -20000 /* Current thread group leader. */
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/*
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* ...and for userland we make life simpler - PIDFD_SELF refers to the current
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* thread, PIDFD_SELF_PROCESS refers to the process thread group leader.
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*
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* For nearly all practical uses, a user will want to use PIDFD_SELF.
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*/
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#define PIDFD_SELF PIDFD_SELF_THREAD
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#define PIDFD_SELF_PROCESS PIDFD_SELF_THREAD_GROUP
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struct pidfd_info {
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/*
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* This mask is similar to the request_mask in statx(2).
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*
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* Userspace indicates what extensions or expensive-to-calculate fields
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* they want by setting the corresponding bits in mask. The kernel
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* will ignore bits that it does not know about.
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*
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* When filling the structure, the kernel will only set bits
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* corresponding to the fields that were actually filled by the kernel.
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* This also includes any future extensions that might be automatically
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* filled. If the structure size is too small to contain a field
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* (requested or not), to avoid confusion the mask will not
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* contain a bit for that field.
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*
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* As such, userspace MUST verify that mask contains the
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* corresponding flags after the ioctl(2) returns to ensure that it is
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* using valid data.
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*/
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__u64 mask;
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/*
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* The information contained in the following fields might be stale at the
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* time it is received, as the target process might have exited as soon as
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* the IOCTL was processed, and there is no way to avoid that. However, it
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* is guaranteed that if the call was successful, then the information was
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* correct and referred to the intended process at the time the work was
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* performed. */
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__u64 cgroupid;
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__u32 pid;
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__u32 tgid;
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__u32 ppid;
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__u32 ruid;
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__u32 rgid;
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__u32 euid;
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__u32 egid;
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__u32 suid;
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__u32 sgid;
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__u32 fsuid;
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__u32 fsgid;
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__u32 spare0[1];
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};
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#define PIDFS_IOCTL_MAGIC 0xFF
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#define PIDFD_GET_CGROUP_NAMESPACE _IO(PIDFS_IOCTL_MAGIC, 1)
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#define PIDFD_GET_IPC_NAMESPACE _IO(PIDFS_IOCTL_MAGIC, 2)
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#define PIDFD_GET_MNT_NAMESPACE _IO(PIDFS_IOCTL_MAGIC, 3)
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#define PIDFD_GET_NET_NAMESPACE _IO(PIDFS_IOCTL_MAGIC, 4)
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#define PIDFD_GET_PID_NAMESPACE _IO(PIDFS_IOCTL_MAGIC, 5)
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#define PIDFD_GET_PID_FOR_CHILDREN_NAMESPACE _IO(PIDFS_IOCTL_MAGIC, 6)
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#define PIDFD_GET_TIME_NAMESPACE _IO(PIDFS_IOCTL_MAGIC, 7)
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#define PIDFD_GET_TIME_FOR_CHILDREN_NAMESPACE _IO(PIDFS_IOCTL_MAGIC, 8)
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#define PIDFD_GET_USER_NAMESPACE _IO(PIDFS_IOCTL_MAGIC, 9)
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#define PIDFD_GET_UTS_NAMESPACE _IO(PIDFS_IOCTL_MAGIC, 10)
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#define PIDFD_GET_INFO _IOWR(PIDFS_IOCTL_MAGIC, 11, struct pidfd_info)
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#endif /* _UAPI_LINUX_PIDFD_H */
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