pidfd: move struct pidfd_fops
Move the pidfd file operations over to their own file in preparation of implementing pidfs and to isolate them from other mostly unrelated functionality in other files. Link: https://lore.kernel.org/r/20240213-vfs-pidfd_fs-v1-1-f863f58cfce1@kernel.org Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Christian Brauner
parent
e1fb1dc08e
commit
50f4f2d197
@ -15,7 +15,7 @@ obj-y := open.o read_write.o file_table.o super.o \
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pnode.o splice.o sync.o utimes.o d_path.o \
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stack.o fs_struct.o statfs.o fs_pin.o nsfs.o \
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fs_types.o fs_context.o fs_parser.o fsopen.o init.o \
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kernel_read_file.o mnt_idmapping.o remap_range.o
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kernel_read_file.o mnt_idmapping.o remap_range.o pidfs.o
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obj-$(CONFIG_BUFFER_HEAD) += buffer.o mpage.o
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obj-$(CONFIG_PROC_FS) += proc_namespace.o
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122
fs/pidfs.c
Normal file
122
fs/pidfs.c
Normal file
@ -0,0 +1,122 @@
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// SPDX-License-Identifier: GPL-2.0
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#include <linux/file.h>
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#include <linux/fs.h>
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#include <linux/magic.h>
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#include <linux/mount.h>
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#include <linux/pid.h>
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#include <linux/pid_namespace.h>
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#include <linux/poll.h>
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#include <linux/proc_fs.h>
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#include <linux/proc_ns.h>
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#include <linux/pseudo_fs.h>
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#include <linux/seq_file.h>
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#include <uapi/linux/pidfd.h>
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static int pidfd_release(struct inode *inode, struct file *file)
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{
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struct pid *pid = file->private_data;
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file->private_data = NULL;
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put_pid(pid);
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return 0;
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}
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#ifdef CONFIG_PROC_FS
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/**
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* pidfd_show_fdinfo - print information about a pidfd
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* @m: proc fdinfo file
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* @f: file referencing a pidfd
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*
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* Pid:
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* This function will print the pid that a given pidfd refers to in the
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* pid namespace of the procfs instance.
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* If the pid namespace of the process is not a descendant of the pid
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* namespace of the procfs instance 0 will be shown as its pid. This is
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* similar to calling getppid() on a process whose parent is outside of
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* its pid namespace.
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*
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* NSpid:
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* If pid namespaces are supported then this function will also print
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* the pid of a given pidfd refers to for all descendant pid namespaces
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* starting from the current pid namespace of the instance, i.e. the
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* Pid field and the first entry in the NSpid field will be identical.
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* If the pid namespace of the process is not a descendant of the pid
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* namespace of the procfs instance 0 will be shown as its first NSpid
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* entry and no others will be shown.
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* Note that this differs from the Pid and NSpid fields in
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* /proc/<pid>/status where Pid and NSpid are always shown relative to
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* the pid namespace of the procfs instance. The difference becomes
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* obvious when sending around a pidfd between pid namespaces from a
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* different branch of the tree, i.e. where no ancestral relation is
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* present between the pid namespaces:
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* - create two new pid namespaces ns1 and ns2 in the initial pid
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* namespace (also take care to create new mount namespaces in the
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* new pid namespace and mount procfs)
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* - create a process with a pidfd in ns1
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* - send pidfd from ns1 to ns2
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* - read /proc/self/fdinfo/<pidfd> and observe that both Pid and NSpid
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* have exactly one entry, which is 0
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*/
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static void pidfd_show_fdinfo(struct seq_file *m, struct file *f)
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{
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struct pid *pid = f->private_data;
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struct pid_namespace *ns;
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pid_t nr = -1;
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if (likely(pid_has_task(pid, PIDTYPE_PID))) {
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ns = proc_pid_ns(file_inode(m->file)->i_sb);
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nr = pid_nr_ns(pid, ns);
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}
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seq_put_decimal_ll(m, "Pid:\t", nr);
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#ifdef CONFIG_PID_NS
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seq_put_decimal_ll(m, "\nNSpid:\t", nr);
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if (nr > 0) {
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int i;
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/* If nr is non-zero it means that 'pid' is valid and that
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* ns, i.e. the pid namespace associated with the procfs
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* instance, is in the pid namespace hierarchy of pid.
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* Start at one below the already printed level.
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*/
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for (i = ns->level + 1; i <= pid->level; i++)
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seq_put_decimal_ll(m, "\t", pid->numbers[i].nr);
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}
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#endif
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seq_putc(m, '\n');
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}
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#endif
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/*
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* Poll support for process exit notification.
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*/
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static __poll_t pidfd_poll(struct file *file, struct poll_table_struct *pts)
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{
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struct pid *pid = file->private_data;
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bool thread = file->f_flags & PIDFD_THREAD;
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struct task_struct *task;
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__poll_t poll_flags = 0;
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poll_wait(file, &pid->wait_pidfd, pts);
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/*
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* Depending on PIDFD_THREAD, inform pollers when the thread
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* or the whole thread-group exits.
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*/
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guard(rcu)();
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task = pid_task(pid, PIDTYPE_PID);
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if (!task)
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poll_flags = EPOLLIN | EPOLLRDNORM | EPOLLHUP;
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else if (task->exit_state && (thread || thread_group_empty(task)))
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poll_flags = EPOLLIN | EPOLLRDNORM;
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return poll_flags;
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}
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const struct file_operations pidfd_fops = {
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.release = pidfd_release,
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.poll = pidfd_poll,
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#ifdef CONFIG_PROC_FS
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.show_fdinfo = pidfd_show_fdinfo,
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#endif
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};
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110
kernel/fork.c
110
kernel/fork.c
@ -1993,116 +1993,6 @@ struct pid *pidfd_pid(const struct file *file)
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return ERR_PTR(-EBADF);
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}
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static int pidfd_release(struct inode *inode, struct file *file)
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{
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struct pid *pid = file->private_data;
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file->private_data = NULL;
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put_pid(pid);
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return 0;
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}
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#ifdef CONFIG_PROC_FS
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/**
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* pidfd_show_fdinfo - print information about a pidfd
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* @m: proc fdinfo file
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* @f: file referencing a pidfd
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*
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* Pid:
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* This function will print the pid that a given pidfd refers to in the
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* pid namespace of the procfs instance.
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* If the pid namespace of the process is not a descendant of the pid
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* namespace of the procfs instance 0 will be shown as its pid. This is
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* similar to calling getppid() on a process whose parent is outside of
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* its pid namespace.
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*
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* NSpid:
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* If pid namespaces are supported then this function will also print
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* the pid of a given pidfd refers to for all descendant pid namespaces
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* starting from the current pid namespace of the instance, i.e. the
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* Pid field and the first entry in the NSpid field will be identical.
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* If the pid namespace of the process is not a descendant of the pid
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* namespace of the procfs instance 0 will be shown as its first NSpid
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* entry and no others will be shown.
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* Note that this differs from the Pid and NSpid fields in
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* /proc/<pid>/status where Pid and NSpid are always shown relative to
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* the pid namespace of the procfs instance. The difference becomes
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* obvious when sending around a pidfd between pid namespaces from a
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* different branch of the tree, i.e. where no ancestral relation is
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* present between the pid namespaces:
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* - create two new pid namespaces ns1 and ns2 in the initial pid
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* namespace (also take care to create new mount namespaces in the
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* new pid namespace and mount procfs)
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* - create a process with a pidfd in ns1
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* - send pidfd from ns1 to ns2
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* - read /proc/self/fdinfo/<pidfd> and observe that both Pid and NSpid
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* have exactly one entry, which is 0
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*/
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static void pidfd_show_fdinfo(struct seq_file *m, struct file *f)
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{
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struct pid *pid = f->private_data;
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struct pid_namespace *ns;
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pid_t nr = -1;
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if (likely(pid_has_task(pid, PIDTYPE_PID))) {
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ns = proc_pid_ns(file_inode(m->file)->i_sb);
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nr = pid_nr_ns(pid, ns);
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}
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seq_put_decimal_ll(m, "Pid:\t", nr);
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#ifdef CONFIG_PID_NS
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seq_put_decimal_ll(m, "\nNSpid:\t", nr);
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if (nr > 0) {
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int i;
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/* If nr is non-zero it means that 'pid' is valid and that
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* ns, i.e. the pid namespace associated with the procfs
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* instance, is in the pid namespace hierarchy of pid.
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* Start at one below the already printed level.
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*/
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for (i = ns->level + 1; i <= pid->level; i++)
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seq_put_decimal_ll(m, "\t", pid->numbers[i].nr);
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}
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#endif
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seq_putc(m, '\n');
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}
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#endif
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/*
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* Poll support for process exit notification.
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*/
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static __poll_t pidfd_poll(struct file *file, struct poll_table_struct *pts)
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{
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struct pid *pid = file->private_data;
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bool thread = file->f_flags & PIDFD_THREAD;
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struct task_struct *task;
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__poll_t poll_flags = 0;
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poll_wait(file, &pid->wait_pidfd, pts);
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/*
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* Depending on PIDFD_THREAD, inform pollers when the thread
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* or the whole thread-group exits.
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*/
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rcu_read_lock();
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task = pid_task(pid, PIDTYPE_PID);
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if (!task)
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poll_flags = EPOLLIN | EPOLLRDNORM | EPOLLHUP;
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else if (task->exit_state && (thread || thread_group_empty(task)))
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poll_flags = EPOLLIN | EPOLLRDNORM;
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rcu_read_unlock();
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return poll_flags;
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}
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const struct file_operations pidfd_fops = {
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.release = pidfd_release,
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.poll = pidfd_poll,
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#ifdef CONFIG_PROC_FS
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.show_fdinfo = pidfd_show_fdinfo,
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#endif
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};
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/**
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* __pidfd_prepare - allocate a new pidfd_file and reserve a pidfd
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* @pid: the struct pid for which to create a pidfd
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