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Add sample notification program

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The sample program is run like:

	./samples/watch_queue/watch_test

and watches "/" for mount changes and the current session keyring for key
changes:

	# keyctl add user a a @s
	1035096409
	# keyctl unlink 1035096409 @s

producing:

	# ./watch_test
	read() = 16
	NOTIFY[000]: ty=000001 sy=02 i=00000110
	KEY 2ffc2e5d change=2[linked] aux=1035096409
	read() = 16
	NOTIFY[000]: ty=000001 sy=02 i=00000110
	KEY 2ffc2e5d change=3[unlinked] aux=1035096409

Other events may be produced, such as with a failing disk:

	read() = 22
	NOTIFY[000]: ty=000003 sy=02 i=00000416
	USB 3-7.7 dev-reset e=0 r=0
	read() = 24
	NOTIFY[000]: ty=000002 sy=06 i=00000418
	BLOCK 00800050 e=6[critical medium] s=64000ef8

This corresponds to:

	blk_update_request: critical medium error, dev sdf, sector 1677725432 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0

in dmesg.

Signed-off-by: David Howells <dhowells@redhat.com>
This commit is contained in:
David Howells 2020-01-14 17:07:11 +00:00
parent f7e47677e3
commit f5b5a164f9
4 changed files with 197 additions and 0 deletions
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6
samples/Kconfig
View File

@ -190,5 +190,11 @@ config SAMPLE_INTEL_MEI
help
Build a sample program to work with mei device.
config SAMPLE_WATCH_QUEUE
bool "Build example /dev/watch_queue notification consumer"
depends on HEADERS_INSTALL
help
Build example userspace program to use the new mount_notify(),
sb_notify() syscalls and the KEYCTL_WATCH_KEY keyctl() function.
endif # SAMPLES

1
samples/Makefile
View File

@ -24,3 +24,4 @@ obj-$(CONFIG_VIDEO_PCI_SKELETON) += v4l/
obj-y += vfio-mdev/
subdir-$(CONFIG_SAMPLE_VFS) += vfs
obj-$(CONFIG_SAMPLE_INTEL_MEI) += mei/
subdir-$(CONFIG_SAMPLE_WATCH_QUEUE) += watch_queue

7
samples/watch_queue/Makefile Normal file
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@ -0,0 +1,7 @@
# List of programs to build
hostprogs := watch_test
# Tell kbuild to always build the programs
always-y := $(hostprogs)
HOSTCFLAGS_watch_test.o += -I$(objtree)/usr/include

183
samples/watch_queue/watch_test.c Normal file
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@ -0,0 +1,183 @@
// SPDX-License-Identifier: GPL-2.0
/* Use /dev/watch_queue to watch for notifications.
*
* Copyright (C) 2020 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*/
#define _GNU_SOURCE
#include <stdbool.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <unistd.h>
#include <errno.h>
#include <sys/ioctl.h>
#include <limits.h>
#include <linux/watch_queue.h>
#include <linux/unistd.h>
#include <linux/keyctl.h>
#ifndef KEYCTL_WATCH_KEY
#define KEYCTL_WATCH_KEY -1
#endif
#ifndef __NR_keyctl
#define __NR_keyctl -1
#endif
#define BUF_SIZE 256
static long keyctl_watch_key(int key, int watch_fd, int watch_id)
{
return syscall(__NR_keyctl, KEYCTL_WATCH_KEY, key, watch_fd, watch_id);
}
static const char *key_subtypes[256] = {
[NOTIFY_KEY_INSTANTIATED] = "instantiated",
[NOTIFY_KEY_UPDATED] = "updated",
[NOTIFY_KEY_LINKED] = "linked",
[NOTIFY_KEY_UNLINKED] = "unlinked",
[NOTIFY_KEY_CLEARED] = "cleared",
[NOTIFY_KEY_REVOKED] = "revoked",
[NOTIFY_KEY_INVALIDATED] = "invalidated",
[NOTIFY_KEY_SETATTR] = "setattr",
};
static void saw_key_change(struct watch_notification *n, size_t len)
{
struct key_notification *k = (struct key_notification *)n;
if (len != sizeof(struct key_notification)) {
fprintf(stderr, "Incorrect key message length\n");
return;
}
printf("KEY %08x change=%u[%s] aux=%u\n",
k->key_id, n->subtype, key_subtypes[n->subtype], k->aux);
}
/*
* Consume and display events.
*/
static void consumer(int fd)
{
unsigned char buffer[4096], *p, *end;
union {
struct watch_notification n;
unsigned char buf1[128];
} n;
ssize_t buf_len;
for (;;) {
buf_len = read(fd, buffer, sizeof(buffer));
if (buf_len == -1) {
perror("read");
exit(1);
}
if (buf_len == 0) {
printf("-- END --\n");
return;
}
if (buf_len > sizeof(buffer)) {
fprintf(stderr, "Read buffer overrun: %zd\n", buf_len);
return;
}
printf("read() = %zd\n", buf_len);
p = buffer;
end = buffer + buf_len;
while (p < end) {
size_t largest, len;
largest = end - p;
if (largest > 128)
largest = 128;
if (largest < sizeof(struct watch_notification)) {
fprintf(stderr, "Short message header: %zu\n", largest);
return;
}
memcpy(&n, p, largest);
printf("NOTIFY[%03zx]: ty=%06x sy=%02x i=%08x\n",
p - buffer, n.n.type, n.n.subtype, n.n.info);
len = n.n.info & WATCH_INFO_LENGTH;
if (len < sizeof(n.n) || len > largest) {
fprintf(stderr, "Bad message length: %zu/%zu\n", len, largest);
exit(1);
}
switch (n.n.type) {
case WATCH_TYPE_META:
switch (n.n.subtype) {
case WATCH_META_REMOVAL_NOTIFICATION:
printf("REMOVAL of watchpoint %08x\n",
(n.n.info & WATCH_INFO_ID) >>
WATCH_INFO_ID__SHIFT);
break;
default:
printf("other meta record\n");
break;
}
break;
case WATCH_TYPE_KEY_NOTIFY:
saw_key_change(&n.n, len);
break;
default:
printf("other type\n");
break;
}
p += len;
}
}
}
static struct watch_notification_filter filter = {
.nr_filters = 1,
.filters = {
[0] = {
.type = WATCH_TYPE_KEY_NOTIFY,
.subtype_filter[0] = UINT_MAX,
},
},
};
int main(int argc, char **argv)
{
int pipefd[2], fd;
if (pipe2(pipefd, O_NOTIFICATION_PIPE) == -1) {
perror("pipe2");
exit(1);
}
fd = pipefd[0];
if (ioctl(fd, IOC_WATCH_QUEUE_SET_SIZE, BUF_SIZE) == -1) {
perror("watch_queue(size)");
exit(1);
}
if (ioctl(fd, IOC_WATCH_QUEUE_SET_FILTER, &filter) == -1) {
perror("watch_queue(filter)");
exit(1);
}
if (keyctl_watch_key(KEY_SPEC_SESSION_KEYRING, fd, 0x01) == -1) {
perror("keyctl");
exit(1);
}
if (keyctl_watch_key(KEY_SPEC_USER_KEYRING, fd, 0x02) == -1) {
perror("keyctl");
exit(1);
}
consumer(fd);
exit(0);
}