kdb: core for kgdb back end (2 of 2)

This patch contains the hooks and instrumentation into kernel which
live outside the kernel/debug directory, which the kdb core
will call to run commands like lsmod, dmesg, bt etc...

CC: linux-arch@vger.kernel.org
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Martin Hicks <mort@sgi.com>

1 files changed, 40 insertions, 0 deletions

diff --git a/kernel/signal.c b/kernel/signal.c
index dbd7fe073c55..825a3f24ad76 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2735,3 +2735,43 @@ void __init signals_init(void)
 {
         sigqueue_cachep = KMEM_CACHE(sigqueue, SLAB_PANIC);
 }
+
+#ifdef CONFIG_KGDB_KDB
+#include <linux/kdb.h>
+/*
+ * kdb_send_sig_info - Allows kdb to send signals without exposing
+ * signal internals.  This function checks if the required locks are
+ * available before calling the main signal code, to avoid kdb
+ * deadlocks.
+ */
+void
+kdb_send_sig_info(struct task_struct *t, struct siginfo *info)
+{
+        static struct task_struct *kdb_prev_t;
+        int sig, new_t;
+        if (!spin_trylock(&t->sighand->siglock)) {
+                kdb_printf("Can't do kill command now.\n"
+                           "The sigmask lock is held somewhere else in "
+                           "kernel, try again later\n");
+                return;
+        }
+        spin_unlock(&t->sighand->siglock);
+        new_t = kdb_prev_t != t;
+        kdb_prev_t = t;
+        if (t->state != TASK_RUNNING && new_t) {
+                kdb_printf("Process is not RUNNING, sending a signal from "
+                           "kdb risks deadlock\n"
+                           "on the run queue locks. "
+                           "The signal has _not_ been sent.\n"
+                           "Reissue the kill command if you want to risk "
+                           "the deadlock.\n");
+                return;
+        }
+        sig = info->si_signo;
+        if (send_sig_info(sig, info, t))
+                kdb_printf("Fail to deliver Signal %d to process %d.\n",
+                           sig, t->pid);
+        else
+                kdb_printf("Signal %d is sent to process %d.\n", sig, t->pid);
+}
+#endif  /* CONFIG_KGDB_KDB */