[PATCH] uml: mconsole fixes

 * when we have stop/sysrq/go, we get pt_regs of whatever executes
   mc_work_proc().  Would be better to see what we had at the time of
   interrupt that got us stop.

 * stop/stop/stop.....  will give stack overflow.  Shouldn't allow stop
   from mconsole_stop().

 * stop/stop/go leaves us inside mconsole_stop() with
	os_set_fd_block(req->originating_fd, 0);
	reactivate_fd(req->originating_fd, MCONSOLE_IRQ);
   just done by nested mconsole_stop().  Ditto.

 * once we'd seen stop, there's a period when INTR commands are executed
   out of order (as they should; we might have the things stuck badly
   enough to never reach mconsole_stop(), but still not badly enough to
   block mconsole_interrupt(); in that situation we _want_ things like
   "cad" to be executed immediately).  Once we enter monsole_stop(), all
   INTR commands will be executed in order, mixed with PROC ones.  We'd
   better let user see that such change of behaviour has happened.
   (Suggested by lennert).

 * stack footprint of monsole_interrupt() is an atrocity; AFAICS we can
   safely make struct mc_request req; static in function there.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 19 insertions, 6 deletions

diff --git a/arch/um/drivers/mconsole_kern.c b/arch/um/drivers/mconsole_kern.c
index d08bd036ccb8..7b172160fe04 100644
--- a/arch/um/drivers/mconsole_kern.c
+++ b/arch/um/drivers/mconsole_kern.c
@@ -79,7 +79,7 @@ static irqreturn_t mconsole_interrupt(int irq, void *dev_id)
         /* long to avoid size mismatch warnings from gcc */
         long fd;
         struct mconsole_entry *new;
-        struct mc_request req;
+        static struct mc_request req;   /* that's OK */
 
         fd = (long) dev_id;
         while (mconsole_get_request(fd, &req)){
@@ -91,6 +91,7 @@ static irqreturn_t mconsole_interrupt(int irq, void *dev_id)
                                 mconsole_reply(&req, "Out of memory", 1, 0);
                         else {
                                 new->request = req;
+                                new->request.regs = get_irq_regs()->regs;
                                 list_add(&new->list, &mc_requests);
                         }
                 }
@@ -314,9 +315,21 @@ void mconsole_stop(struct mc_request *req)
 {
         deactivate_fd(req->originating_fd, MCONSOLE_IRQ);
         os_set_fd_block(req->originating_fd, 1);
-        mconsole_reply(req, "", 0, 0);
-        while(mconsole_get_request(req->originating_fd, req)){
-                if(req->cmd->handler == mconsole_go) break;
+        mconsole_reply(req, "stopped", 0, 0);
+        while (mconsole_get_request(req->originating_fd, req)) {
+                if (req->cmd->handler == mconsole_go)
+                        break;
+                if (req->cmd->handler == mconsole_stop) {
+                        mconsole_reply(req, "Already stopped", 1, 0);
+                        continue;
+                }
+                if (req->cmd->handler == mconsole_sysrq) {
+                        struct pt_regs *old_regs;
+                        old_regs = set_irq_regs((struct pt_regs *)&req->regs);
+                        mconsole_sysrq(req);
+                        set_irq_regs(old_regs);
+                        continue;
+                }
                 (*req->cmd->handler)(req);
         }
         os_set_fd_block(req->originating_fd, 0);
@@ -673,9 +686,7 @@ static void with_console(struct mc_request *req, void (*proc)(void *),
 static void sysrq_proc(void *arg)
 {
         char *op = arg;
-        struct pt_regs *old_regs = set_irq_regs(&current->thread.regs);
         handle_sysrq(*op, NULL);
-        set_irq_regs(old_regs);
 }
 
 void mconsole_sysrq(struct mc_request *req)
diff --git a/arch/um/drivers/mconsole_user.c b/arch/um/drivers/mconsole_user.c
index 17068eb746c0..75aef6f7ef6e 100644
--- a/arch/um/drivers/mconsole_user.c
+++ b/arch/um/drivers/mconsole_user.c
@@ -14,6 +14,7 @@
 #include <sys/un.h>
 #include <unistd.h>
 #include "user.h"
+#include "sysdep/ptrace.h"
 #include "mconsole.h"
 #include "umid.h"
 #include "user_util.h"
diff --git a/arch/um/include/mconsole.h b/arch/um/include/mconsole.h
index 58f67d391105..2666815b6af5 100644
--- a/arch/um/include/mconsole.h
+++ b/arch/um/include/mconsole.h
@@ -61,6 +61,7 @@ struct mc_request
 
         struct mconsole_request request;
         struct mconsole_command *cmd;
+        union uml_pt_regs regs;
 };
 
 extern char mconsole_socket_name[];