[RFC] un petite hack: /proc/*/ctl

[Alexey Dobriyan <adobriyan@gmail.com>]

echo kill >/proc/$PID/ctl
	send SIGKILL to process

echo term >/proc/$PID/ctl
	send SIGTERM to process

--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -71,6 +71,7 @@
 #include <linux/cpuset.h>
 #include <linux/audit.h>
 #include <linux/poll.h>
+#include <linux/syscalls.h>
 #include "internal.h"
 
 /*
@@ -125,6 +126,7 @@ enum pid_directory_inos {
 #endif
 	PROC_TGID_OOM_SCORE,
 	PROC_TGID_OOM_ADJUST,
+	PROC_TGID_CTL,
 	PROC_TID_INO,
 	PROC_TID_STATUS,
 	PROC_TID_MEM,
@@ -165,6 +167,7 @@ enum pid_directory_inos {
 #endif
 	PROC_TID_OOM_SCORE,
 	PROC_TID_OOM_ADJUST,
+	PROC_TID_CTL,
 
 	/* Add new entries before this */
 	PROC_TID_FD_DIR = 0x8000,	/* 0x8000-0xffff */
@@ -220,6 +223,7 @@ static struct pid_entry tgid_base_stuff[
 #ifdef CONFIG_AUDITSYSCALL
 	E(PROC_TGID_LOGINUID, "loginuid", S_IFREG|S_IWUSR|S_IRUGO),
 #endif
+	E(PROC_TGID_CTL,       "ctl",     S_IFREG|S_IWUSR),
 	{0,0,NULL,0}
 };
 static struct pid_entry tid_base_stuff[] = {
@@ -262,6 +266,7 @@ static struct pid_entry tid_base_stuff[]
 #ifdef CONFIG_AUDITSYSCALL
 	E(PROC_TID_LOGINUID, "loginuid", S_IFREG|S_IWUSR|S_IRUGO),
 #endif
+	E(PROC_TID_CTL,        "ctl",     S_IFREG|S_IWUSR),
 	{0,0,NULL,0}
 };
 
@@ -942,6 +947,42 @@ static struct file_operations proc_oom_a
 	.write		= oom_adjust_write,
 };
 
+static ssize_t ctl_write(struct file *file, const char __user *buf,
+			 size_t count, loff_t *ppos)
+{
+	char __buf[5];
+	struct task_struct *task;
+	int sig;
+
+	count = min(count, sizeof(__buf));
+	memset(__buf, 0, sizeof(__buf));
+	if (copy_from_user(__buf, buf, count))
+		return -EFAULT;
+	__buf[sizeof(__buf) - 1] = '\0';
+
+enum {
+	CONFIG_BOFH = 0,
+};
+
+	if (strcmp(__buf, "kill") == 0)
+		sig = SIGKILL;
+	else if (CONFIG_BOFH && strcmp(__buf, "FOAD") == 0)
+		sig = SIGKILL;
+	else if (strcmp(__buf, "term") == 0)
+		sig = SIGTERM;
+	else
+		goto exit;
+
+	task = proc_task(file->f_dentry->d_inode);
+	sys_kill(task->pid, sig);
+exit:
+	return count;
+}
+
+static struct file_operations proc_ctl_operations = {
+	.write		= ctl_write,
+};
+
 static struct inode_operations proc_mem_inode_operations = {
 	.permission	= proc_permission,
 };
@@ -1780,6 +1821,10 @@ static struct dentry *proc_pident_lookup
 		case PROC_TGID_OOM_ADJUST:
 			inode->i_fop = &proc_oom_adjust_operations;
 			break;
+		case PROC_TID_CTL:
+		case PROC_TGID_CTL:
+			inode->i_fop = &proc_ctl_operations;
+			break;
 #ifdef CONFIG_AUDITSYSCALL
 		case PROC_TID_LOGINUID:
 		case PROC_TGID_LOGINUID:

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