lsfd: add KTHREAD column

Signed-off-by: Masatake YAMATO <yamato@redhat.com>

include/procfs.h

@@ -28,6 +28,7 @@ extern int procfs_process_init_path(struct path_cxt *pc, pid_t pid);
 extern int procfs_process_get_uid(struct path_cxt *pc, uid_t *uid);
 extern ssize_t procfs_process_get_cmdline(struct path_cxt *pc, char *buf, size_t bufsz);
 extern ssize_t procfs_process_get_cmdname(struct path_cxt *pc, char *buf, size_t bufsz);
+extern ssize_t procfs_process_get_stat(struct path_cxt *pc, char *buf, size_t bufsz);
 
 
 static inline ssize_t procfs_process_get_exe(struct path_cxt *pc, char *buf, size_t bufsz)

lib/procfs.c

@@ -138,9 +138,10 @@ static ssize_t read_procfs_file(int fd, char *buf, size_t bufsz)
 	return sz;
 }
 
-ssize_t procfs_process_get_cmdline(struct path_cxt *pc, char *buf, size_t bufsz)
+static ssize_t procfs_process_get_line_for(struct path_cxt *pc, char *buf, size_t bufsz,
+					    const char *fname)
 {
-	int fd = ul_path_open(pc, O_RDONLY|O_CLOEXEC, "cmdline");
+	int fd = ul_path_open(pc, O_RDONLY|O_CLOEXEC, fname);
 
 	if (fd >= 0) {
 		ssize_t sz = read_procfs_file(fd, buf, bufsz);
@@ -150,16 +151,19 @@ ssize_t procfs_process_get_cmdline(struct path_cxt *pc, char *buf, size_t bufsz)
 	return -errno;
 }
 
+ssize_t procfs_process_get_cmdline(struct path_cxt *pc, char *buf, size_t bufsz)
+{
+	return procfs_process_get_line_for(pc, buf, bufsz, "cmdline");
+}
+
 ssize_t procfs_process_get_cmdname(struct path_cxt *pc, char *buf, size_t bufsz)
 {
-	int fd = ul_path_open(pc, O_RDONLY|O_CLOEXEC, "comm");
+	return procfs_process_get_line_for(pc, buf, bufsz, "comm");
+}
 
-	if (fd >= 0) {
-		ssize_t sz = read_procfs_file(fd, buf, bufsz);
-		close(fd);
-		return sz;
-	}
-	return -errno;
+ssize_t procfs_process_get_stat(struct path_cxt *pc, char *buf, size_t bufsz)
+{
+	return procfs_process_get_line_for(pc, buf, bufsz, "stat");
 }
 
 int procfs_process_get_uid(struct path_cxt *pc, uid_t *uid)

misc-utils/lsfd-file.c

@@ -297,6 +297,9 @@ static bool file_fill_column(struct proc *proc,
 	case COL_DELETED:
 		xasprintf(&str, "%d", file->stat.st_nlink == 0);
 		break;
+	case COL_KTHREAD:
+		xasprintf(&str, "%u", proc->kthread);
+		break;
 	case COL_MNT_ID:
 		xasprintf(&str, "%d", file->association < 0? 0: file->mnt_id);
 		break;

misc-utils/lsfd.1.adoc

@@ -104,6 +104,9 @@ User ID number of the file's owner.
 INODE <__number__>::
 Inode number.
 
+KTHREAD <__boolean__>::
+Whether the process is a kernel thread or not.
+
 MAJ:MIN <__string__>::
 Device ID for special, or ID of device containing file.
 

misc-utils/lsfd.c

@@ -30,6 +30,7 @@
 #include <unistd.h>
 #include <getopt.h>
 
+#include <linux/sched.h>
 #include <sys/syscall.h>
 #include <linux/kcmp.h>
 static int kcmp(pid_t pid1, pid_t pid2, int type,
@@ -38,6 +39,10 @@ static int kcmp(pid_t pid1, pid_t pid2, int type,
 	return syscall(SYS_kcmp, pid1, pid2, type, idx1, idx2);
 }
 
+/* See proc(5).
+ * Defined in linux/include/linux/sched.h private header file. */
+#define PF_KTHREAD		0x00200000	/* I am a kernel thread */
+
 #include "c.h"
 #include "nls.h"
 #include "xalloc.h"
@@ -108,6 +113,8 @@ static struct colinfo infos[] = {
 		N_("user ID number of the file's owner") },
 	[COL_INODE]   = { "INODE",    0, SCOLS_FL_RIGHT, SCOLS_JSON_NUMBER,
 		N_("inode number") },
+	[COL_KTHREAD] = { "KTHREAD",    0, SCOLS_FL_RIGHT, SCOLS_JSON_BOOLEAN,
+		N_("opened by a kernel thread") },
 	[COL_MAJMIN]  = { "MAJ:MIN",  0, SCOLS_FL_RIGHT, SCOLS_JSON_STRING,
 		N_("device ID for special, or ID of device containing file") },
 	[COL_MAPLEN]  = { "MAPLEN",   0, SCOLS_FL_RIGHT, SCOLS_JSON_NUMBER,
@@ -195,6 +202,9 @@ struct lsfd_control {
 	struct lsfd_filter *filter;
 };
 
+static void xstrappend(char **a, const char *b);
+static void xstrputc(char **a, char c);
+
 static int column_name_to_id(const char *name, size_t namesz)
 {
 	size_t i;
@@ -381,6 +391,7 @@ static struct proc *new_process(pid_t pid, struct proc *leader)
 	INIT_LIST_HEAD(&proc->files);
 	INIT_LIST_HEAD(&proc->procs);
 
+	proc->kthread = 0;
 	return proc;
 }
 
@@ -867,6 +878,25 @@ static void read_process(struct lsfd_control *ctl, struct path_cxt *pc,
 			xstrdup(buf) : xstrdup(_("(unknown)"));
 	procfs_process_get_uid(pc, &proc->uid);
 
+	if (procfs_process_get_stat(pc, buf, sizeof(buf)) > 0) {
+		char *p;
+		unsigned int flags;
+		char *pat = NULL;
+
+		/* See proc(5) about the column in the line. */
+		xstrappend(&pat, "%*d (");
+		for (p = proc->command; *p != '\0'; p++) {
+			if (*p == '%')
+				xstrappend(&pat, "%%");
+			else
+				xstrputc(&pat, *p);
+		}
+		xstrappend(&pat, ") %*c %*d %*d %*d %*d %*d %u %*[^\n]");
+		if (sscanf(buf, pat, &flags) == 1)
+			proc->kthread = !!(flags & PF_KTHREAD);
+		free(pat);
+	}
+
 	collect_execve_file(pc, proc);
 
 	if (proc->pid == proc->leader->pid
@@ -987,6 +1017,12 @@ static void xstrappend(char **a, const char *b)
 		err(EXIT_FAILURE, _("failed to allocate memory for string"));
 }
 
+static void xstrputc(char **a, char c)
+{
+	char b[] = {c, '\0'};
+	xstrappend(a, b);
+}
+
 static char * quote_filter_expr(char *expr)
 {
 	char c[] = {'\0', '\0'};

misc-utils/lsfd.h

@@ -44,6 +44,7 @@ enum {
 	COL_FD,
 	COL_FLAGS,
 	COL_INODE,
+	COL_KTHREAD,
 	COL_MAJMIN,
 	COL_MAPLEN,
 	COL_MISCDEV,
@@ -97,6 +98,7 @@ struct proc {
 	ino_t ns_mnt;
 	struct list_head procs;
 	struct list_head files;
+	unsigned int kthread: 1;
 };
 
 /*

tests/expected/lsfd/column-kthread

@@ -0,0 +1,6 @@
+COMMAND  PID USER MODE TYPE INODE NAME KTHREAD
+systemd    1 root  ---  DIR     2 /          0
+systemd    1 root  ---  DIR     2 /          0
+kthreadd   2 root  ---  DIR     2 /          1
+kthreadd   2 root  ---  DIR     2 /          1
+0

tests/ts/lsfd/column-kthread

@@ -0,0 +1,42 @@
+#!/bin/bash
+#
+# Copyright (C) 2021 Masatake YAMATO <yamato@redhat.com>
+#
+# This file is part of util-linux.
+#
+# This file is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This file 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 General Public License for more details.
+#
+
+TS_TOPDIR="${0%/*}/../.."
+TS_DESC="directory"
+
+. $TS_TOPDIR/functions.sh
+ts_init "$*"
+
+ts_check_test_command "$TS_CMD_LSFD"
+ts_check_prog "ps"
+
+ts_skip_nonroot
+
+[ "$(ps --no-headers -o comm 1)" = 'systemd'  ] || ts_skip "pid 1 is not systemd"
+[ "$(ps --no-headers -o comm 2)" = 'kthreadd' ] || ts_skip "pid 2 is not kthreadd"
+
+ts_cd "$TS_OUTDIR"
+
+{
+    "$TS_CMD_LSFD" -o COMMAND,PID,USER,MODE,TYPE,INODE,NAME,KTHREAD \
+		   -Q '(PID < 3) and ((ASSOC == "cwd") or (ASSOC == "rtd"))'
+    echo $?
+} > $TS_OUTPUT 2>&1
+
+ts_finalize
+
+