v4.19.13 snapshot.
diff --git a/arch/um/drivers/mconsole_user.c b/arch/um/drivers/mconsole_user.c
new file mode 100644
index 0000000..9920982
--- /dev/null
+++ b/arch/um/drivers/mconsole_user.c
@@ -0,0 +1,219 @@
+/*
+ * Copyright (C) 2001 Lennert Buytenhek (buytenh@gnu.org)
+ * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ * Licensed under the GPL
+ */
+
+#include <errno.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/socket.h>
+#include <sys/uio.h>
+#include <sys/un.h>
+#include "mconsole.h"
+
+static struct mconsole_command commands[] = {
+ /*
+ * With uts namespaces, uts information becomes process-specific, so
+ * we need a process context. If we try handling this in interrupt
+ * context, we may hit an exiting process without a valid uts
+ * namespace.
+ */
+ { "version", mconsole_version, MCONSOLE_PROC },
+ { "halt", mconsole_halt, MCONSOLE_PROC },
+ { "reboot", mconsole_reboot, MCONSOLE_PROC },
+ { "config", mconsole_config, MCONSOLE_PROC },
+ { "remove", mconsole_remove, MCONSOLE_PROC },
+ { "sysrq", mconsole_sysrq, MCONSOLE_INTR },
+ { "help", mconsole_help, MCONSOLE_INTR },
+ { "cad", mconsole_cad, MCONSOLE_INTR },
+ { "stop", mconsole_stop, MCONSOLE_PROC },
+ { "go", mconsole_go, MCONSOLE_INTR },
+ { "log", mconsole_log, MCONSOLE_INTR },
+ { "proc", mconsole_proc, MCONSOLE_PROC },
+ { "stack", mconsole_stack, MCONSOLE_INTR },
+};
+
+/* Initialized in mconsole_init, which is an initcall */
+char mconsole_socket_name[256];
+
+static int mconsole_reply_v0(struct mc_request *req, char *reply)
+{
+ struct iovec iov;
+ struct msghdr msg;
+
+ iov.iov_base = reply;
+ iov.iov_len = strlen(reply);
+
+ msg.msg_name = &(req->origin);
+ msg.msg_namelen = req->originlen;
+ msg.msg_iov = &iov;
+ msg.msg_iovlen = 1;
+ msg.msg_control = NULL;
+ msg.msg_controllen = 0;
+ msg.msg_flags = 0;
+
+ return sendmsg(req->originating_fd, &msg, 0);
+}
+
+static struct mconsole_command *mconsole_parse(struct mc_request *req)
+{
+ struct mconsole_command *cmd;
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(commands); i++) {
+ cmd = &commands[i];
+ if (!strncmp(req->request.data, cmd->command,
+ strlen(cmd->command))) {
+ return cmd;
+ }
+ }
+ return NULL;
+}
+
+#define MIN(a,b) ((a)<(b) ? (a):(b))
+
+#define STRINGX(x) #x
+#define STRING(x) STRINGX(x)
+
+int mconsole_get_request(int fd, struct mc_request *req)
+{
+ int len;
+
+ req->originlen = sizeof(req->origin);
+ req->len = recvfrom(fd, &req->request, sizeof(req->request), 0,
+ (struct sockaddr *) req->origin, &req->originlen);
+ if (req->len < 0)
+ return 0;
+
+ req->originating_fd = fd;
+
+ if (req->request.magic != MCONSOLE_MAGIC) {
+ /* Unversioned request */
+ len = MIN(sizeof(req->request.data) - 1,
+ strlen((char *) &req->request));
+ memmove(req->request.data, &req->request, len);
+ req->request.data[len] = '\0';
+
+ req->request.magic = MCONSOLE_MAGIC;
+ req->request.version = 0;
+ req->request.len = len;
+
+ mconsole_reply_v0(req, "ERR Version 0 mconsole clients are "
+ "not supported by this driver");
+ return 0;
+ }
+
+ if (req->request.len >= MCONSOLE_MAX_DATA) {
+ mconsole_reply(req, "Request too large", 1, 0);
+ return 0;
+ }
+ if (req->request.version != MCONSOLE_VERSION) {
+ mconsole_reply(req, "This driver only supports version "
+ STRING(MCONSOLE_VERSION) " clients", 1, 0);
+ }
+
+ req->request.data[req->request.len] = '\0';
+ req->cmd = mconsole_parse(req);
+ if (req->cmd == NULL) {
+ mconsole_reply(req, "Unknown command", 1, 0);
+ return 0;
+ }
+
+ return 1;
+}
+
+int mconsole_reply_len(struct mc_request *req, const char *str, int total,
+ int err, int more)
+{
+ /*
+ * XXX This is a stack consumption problem. It'd be nice to
+ * make it global and serialize access to it, but there are a
+ * ton of callers to this function.
+ */
+ struct mconsole_reply reply;
+ int len, n;
+
+ do {
+ reply.err = err;
+
+ /* err can only be true on the first packet */
+ err = 0;
+
+ len = MIN(total, MCONSOLE_MAX_DATA - 1);
+
+ if (len == total) reply.more = more;
+ else reply.more = 1;
+
+ memcpy(reply.data, str, len);
+ reply.data[len] = '\0';
+ total -= len;
+ str += len;
+ reply.len = len + 1;
+
+ len = sizeof(reply) + reply.len - sizeof(reply.data);
+
+ n = sendto(req->originating_fd, &reply, len, 0,
+ (struct sockaddr *) req->origin, req->originlen);
+
+ if (n < 0)
+ return -errno;
+ } while (total > 0);
+ return 0;
+}
+
+int mconsole_reply(struct mc_request *req, const char *str, int err, int more)
+{
+ return mconsole_reply_len(req, str, strlen(str), err, more);
+}
+
+
+int mconsole_unlink_socket(void)
+{
+ unlink(mconsole_socket_name);
+ return 0;
+}
+
+static int notify_sock = -1;
+
+int mconsole_notify(char *sock_name, int type, const void *data, int len)
+{
+ struct sockaddr_un target;
+ struct mconsole_notify packet;
+ int n, err = 0;
+
+ lock_notify();
+ if (notify_sock < 0) {
+ notify_sock = socket(PF_UNIX, SOCK_DGRAM, 0);
+ if (notify_sock < 0) {
+ err = -errno;
+ printk(UM_KERN_ERR "mconsole_notify - socket failed, "
+ "errno = %d\n", errno);
+ }
+ }
+ unlock_notify();
+
+ if (err)
+ return err;
+
+ target.sun_family = AF_UNIX;
+ strcpy(target.sun_path, sock_name);
+
+ packet.magic = MCONSOLE_MAGIC;
+ packet.version = MCONSOLE_VERSION;
+ packet.type = type;
+ len = (len > sizeof(packet.data)) ? sizeof(packet.data) : len;
+ packet.len = len;
+ memcpy(packet.data, data, len);
+
+ err = 0;
+ len = sizeof(packet) + packet.len - sizeof(packet.data);
+ n = sendto(notify_sock, &packet, len, 0, (struct sockaddr *) &target,
+ sizeof(target));
+ if (n < 0) {
+ err = -errno;
+ printk(UM_KERN_ERR "mconsole_notify - sendto failed, "
+ "errno = %d\n", errno);
+ }
+ return err;
+}