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Commit 0097875b authored by Eric W. Biederman's avatar Eric W. Biederman
Browse files

proc: Implement /proc/thread-self to point at the directory of the current thread 



/proc/thread-self is derived from /proc/self.  /proc/thread-self
points to the directory in proc containing information about the
current thread.

This funtionality has been missing for a long time, and is tricky to
implement in userspace as gettid() is not exported by glibc.  More
importantly this allows fixing defects in /proc/mounts and /proc/net
where in a threaded application today they wind up being empty files
when only the initial pthread has exited, causing problems for other
threads.

Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
parent 6ba8ed79

fs/proc/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -23,6 +23,7 @@ proc-y += version.o 
proc-y	+= softirqs.o

proc-y	+= namespaces.o

proc-y	+= self.o

proc-y	+= thread_self.o

proc-$(CONFIG_PROC_SYSCTL)	+= proc_sysctl.o

proc-$(CONFIG_NET)		+= proc_net.o

proc-$(CONFIG_PROC_KCORE)	+= kcore.o

fs/proc/base.c

+10 −5
Original line number Diff line number Diff line
@@ -2847,7 +2847,7 @@ static struct tgid_iter next_tgid(struct pid_namespace *ns, struct tgid_iter ite 
	return iter;

}



#define TGID_OFFSET (FIRST_PROCESS_ENTRY + 1)

#define TGID_OFFSET (FIRST_PROCESS_ENTRY + 2)



/* for the /proc/ directory itself, after non-process stuff has been done */

int proc_pid_readdir(struct file *file, struct dir_context *ctx)
@@ -2859,14 +2859,19 @@ int proc_pid_readdir(struct file *file, struct dir_context *ctx) 
	if (pos >= PID_MAX_LIMIT + TGID_OFFSET)

		return 0;



	if (pos == TGID_OFFSET - 1) {

	if (pos == TGID_OFFSET - 2) {

		struct inode *inode = ns->proc_self->d_inode;

		if (!dir_emit(ctx, "self", 4, inode->i_ino, DT_LNK))

			return 0;

		iter.tgid = 0;

	} else {

		iter.tgid = pos - TGID_OFFSET;

		ctx->pos = pos = pos + 1;

	}

	if (pos == TGID_OFFSET - 1) {

		struct inode *inode = ns->proc_thread_self->d_inode;

		if (!dir_emit(ctx, "thread-self", 11, inode->i_ino, DT_LNK))

			return 0;

		ctx->pos = pos = pos + 1;

	}

	iter.tgid = pos - TGID_OFFSET;

	iter.task = NULL;

	for (iter = next_tgid(ns, iter);

	     iter.task;

fs/proc/inode.c

+6 −1
Original line number Diff line number Diff line
@@ -442,6 +442,7 @@ struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de) 
int proc_fill_super(struct super_block *s)

{

	struct inode *root_inode;

	int ret;



	s->s_flags |= MS_NODIRATIME | MS_NOSUID | MS_NOEXEC;

	s->s_blocksize = 1024;
@@ -463,5 +464,9 @@ int proc_fill_super(struct super_block *s) 
		return -ENOMEM;

	}



	return proc_setup_self(s);

	ret = proc_setup_self(s);

	if (ret) {

		return ret;

	}

	return proc_setup_thread_self(s);

}

fs/proc/internal.h

+6 −0
Original line number Diff line number Diff line
@@ -233,6 +233,12 @@ static inline int proc_net_init(void) { return 0; } 
 */

extern int proc_setup_self(struct super_block *);



/*

 * proc_thread_self.c

 */

extern int proc_setup_thread_self(struct super_block *);

extern void proc_thread_self_init(void);



/*

 * proc_sysctl.c

 */

fs/proc/root.c

+3 −0
Original line number Diff line number Diff line
@@ -149,6 +149,8 @@ static void proc_kill_sb(struct super_block *sb) 
	ns = (struct pid_namespace *)sb->s_fs_info;

	if (ns->proc_self)

		dput(ns->proc_self);

	if (ns->proc_thread_self)

		dput(ns->proc_thread_self);

	kill_anon_super(sb);

	put_pid_ns(ns);

}
@@ -170,6 +172,7 @@ void __init proc_root_init(void) 
		return;



	proc_self_init();

	proc_thread_self_init();

	proc_symlink("mounts", NULL, "self/mounts");



	proc_net_init();