MFC r301522 (by bz)

Implement a `show panic` command to DDB which will helpfully print the
panic string again if set, in case it scrolled out of the active
window.  This avoids having to remember the symbol name.

Also add a show callout <addr> command to DDB in order to inspect
some struct callout fields in case of panics in the callout code.
This may help to see if there was memory corruption or to further
ease debugging problems.

No objection by:    bz

3 files changed, 59 insertions, 0 deletions

diff --git a/share/man/man4/ddb.4 b/share/man/man4/ddb.4
index 7a7759c..e810028 100644
--- a/share/man/man4/ddb.4
+++ b/share/man/man4/ddb.4
@@ -611,6 +611,13 @@ See the
 header file for more details on the exact meaning of the structure fields.
 .\"
 .Pp
+.It Ic show Cm callout Ar addr
+Show information about the callout structure
+.Vt struct callout
+present at
+.Ar addr .
+.\"
+.Pp
 .It Ic show Cm cbstat
 Show brief information about the TTY subsystem.
 .\"
@@ -839,6 +846,10 @@ option is specified the
 complete object is printed.
 .\"
 .Pp
+.It Ic show Cm panic
+Print the panic message if set.
+.\"
+.Pp
 .It Ic show Cm page
 Show statistics on VM pages.
 .\"
diff --git a/sys/kern/kern_shutdown.c b/sys/kern/kern_shutdown.c
index 8139c8c..d590555 100644
--- a/sys/kern/kern_shutdown.c
+++ b/sys/kern/kern_shutdown.c
@@ -1031,3 +1031,14 @@ mkdumpheader(struct kerneldumpheader *kdh, char *magic, uint32_t archver,
 		strlcpy(kdh->panicstring, panicstr, sizeof(kdh->panicstring));
 	kdh->parity = kerneldump_parity(kdh);
 }
+
+#ifdef DDB
+DB_SHOW_COMMAND(panic, db_show_panic)
+{
+
+	if (panicstr == NULL)
+		db_printf("panicstr not set\n");
+	else
+		db_printf("panic: %s\n", panicstr);
+}
+#endif
diff --git a/sys/kern/kern_timeout.c b/sys/kern/kern_timeout.c
index 7e5aab7..f3c4e78 100644
--- a/sys/kern/kern_timeout.c
+++ b/sys/kern/kern_timeout.c
@@ -39,6 +39,7 @@ __FBSDID("$FreeBSD$");
 
 #include "opt_callout_profiling.h"
 #include "opt_kdtrace.h"
+#include "opt_ddb.h"
 #if defined(__arm__)
 #include "opt_timer.h"
 #endif
@@ -60,6 +61,11 @@ __FBSDID("$FreeBSD$");
 #include <sys/sysctl.h>
 #include <sys/smp.h>
 
+#ifdef DDB
+#include <ddb/ddb.h>
+#include <machine/_inttypes.h>
+#endif
+
 #ifdef SMP
 #include <machine/cpu.h>
 #endif
@@ -1576,3 +1582,34 @@ SYSCTL_PROC(_kern, OID_AUTO, callout_stat,
     CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE,
     0, 0, sysctl_kern_callout_stat, "I",
     "Dump immediate statistic snapshot of the scheduled callouts");
+
+#ifdef DDB
+static void
+_show_callout(struct callout *c)
+{
+
+	db_printf("callout %p\n", c);
+#define	C_DB_PRINTF(f, e)	db_printf("   %s = " f "\n", #e, c->e);
+	db_printf("   &c_links = %p\n", &(c->c_links));
+	C_DB_PRINTF("%" PRId64,	c_time);
+	C_DB_PRINTF("%" PRId64,	c_precision);
+	C_DB_PRINTF("%p",	c_arg);
+	C_DB_PRINTF("%p",	c_func);
+	C_DB_PRINTF("%p",	c_lock);
+	C_DB_PRINTF("%#x",	c_flags);
+	C_DB_PRINTF("%#x",	c_iflags);
+	C_DB_PRINTF("%d",	c_cpu);
+#undef	C_DB_PRINTF
+}
+
+DB_SHOW_COMMAND(callout, db_show_callout)
+{
+
+	if (!have_addr) {
+		db_printf("usage: show callout <struct callout *>\n");
+		return;
+	}
+
+	_show_callout((struct callout *)addr);
+}
+#endif /* DDB */