Hi,
Someone, somewhere (perhaps on bugs@?) said they would like to see
something useful when typing show panic on a page fault'd kernel. That
struck very close to home so I went ahead and did it.
The following diff shows the uvm_fault and the first trace entry in an
attempt to mimic a real show panic. The uvm_fault entry is extra.
Currently I only wrote support for amd64 but I can add support for
other architectures if you guys like it.
Thoughts?
Paul
Index: arch/amd64/amd64/trap.c
===================================================================
RCS file: /cvs/src/sys/arch/amd64/amd64/trap.c,v
retrieving revision 1.62
diff -u -p -u -p -r1.62 trap.c
--- arch/amd64/amd64/trap.c 14 Oct 2017 04:44:43 -0000 1.62
+++ arch/amd64/amd64/trap.c 4 Nov 2017 15:15:47 -0000
@@ -380,12 +380,16 @@ faultcommon:
}
if (type == T_PAGEFLT) {
+ static char faultbuf[512];
if (pcb->pcb_onfault != 0) {
KERNEL_UNLOCK();
goto copyfault;
}
- printf("uvm_fault(%p, 0x%lx, 0, %d) -> %x\n",
+ snprintf(faultbuf, sizeof faultbuf,
+ "uvm_fault(%p, 0x%lx, 0, %d) -> %x",
map, fa, ftype, error);
+ printf("%s\n", faultbuf);
+ faultstr = faultbuf;
goto we_re_toast;
}
Index: ddb/db_command.c
===================================================================
RCS file: /cvs/src/sys/ddb/db_command.c,v
retrieving revision 1.79
diff -u -p -u -p -r1.79 db_command.c
--- ddb/db_command.c 19 Oct 2017 16:58:05 -0000 1.79
+++ ddb/db_command.c 4 Nov 2017 15:15:48 -0000
@@ -51,6 +51,7 @@
#include <ddb/db_watch.h>
#include <ddb/db_run.h>
#include <ddb/db_sym.h>
+#include <ddb/db_var.h>
#include <ddb/db_variables.h>
#include <ddb/db_interface.h>
#include <ddb/db_extern.h>
@@ -500,6 +501,11 @@ db_show_panic_cmd(db_expr_t addr, int ha
{
if (panicstr)
db_printf("%s\n", panicstr);
+ else if (faultstr) {
+ db_printf("kernel page fault\n");
+ db_printf("%s\n", faultstr);
+ db_stack_trace_print(addr, have_addr, 1, modif, db_printf);
+ }
else
db_printf("the kernel did not panic\n"); /* yet */
}
Index: kern/subr_prf.c
===================================================================
RCS file: /cvs/src/sys/kern/subr_prf.c,v
retrieving revision 1.91
diff -u -p -u -p -r1.91 subr_prf.c
--- kern/subr_prf.c 30 Apr 2017 16:45:46 -0000 1.91
+++ kern/subr_prf.c 4 Nov 2017 15:15:48 -0000
@@ -100,6 +100,7 @@ struct mutex kprintf_mutex =
extern int log_open; /* subr_log: is /dev/klog open? */
const char *panicstr; /* arg to first call to panic (used as a flag
to indicate that panic has already been called). */
+const char *faultstr; /* page fault string */
#ifdef DDB
/*
* Enter ddb on panic.
Index: sys/systm.h
===================================================================
RCS file: /cvs/src/sys/sys/systm.h,v
retrieving revision 1.133
diff -u -p -u -p -r1.133 systm.h
--- sys/systm.h 11 Aug 2017 21:24:20 -0000 1.133
+++ sys/systm.h 4 Nov 2017 15:15:49 -0000
@@ -72,6 +72,7 @@
*/
extern int securelevel; /* system security level */
extern const char *panicstr; /* panic message */
+extern const char *faultstr; /* fault message */
extern const char version[]; /* system version */
extern const char copyright[]; /* system copyright */
extern const char ostype[];
