[src/trunk]: src/sys/ddb Unbreak db_cpu_*. Allows backtraces on i386 to prog...

[jakllsch <jakllsch%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/0d9f5df74f8e
branches:  trunk
changeset: 328665:0d9f5df74f8e
user:      jakllsch <jakllsch%NetBSD.org@localhost>
date:      Sat Apr 12 19:01:49 2014 +0000

description:
Unbreak db_cpu_*.  Allows backtraces on i386 to progress beyond the
first function by not doing a NULL-deref in the debugger.

Bug located by me.  Patch implementation by riastradh@.  Hi rmind@.

diffstat:

 sys/ddb/db_cpu.c |  34 +++++++++++++++++++++++++---------
 1 files changed, 25 insertions(+), 9 deletions(-)

diffs (71 lines):

diff -r f3938fdaef2a -r 0d9f5df74f8e sys/ddb/db_cpu.c
--- a/sys/ddb/db_cpu.c  Sat Apr 12 18:30:39 2014 +0000
+++ b/sys/ddb/db_cpu.c  Sat Apr 12 19:01:49 2014 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: db_cpu.c,v 1.5 2013/11/24 21:58:38 rmind Exp $ */
+/*     $NetBSD: db_cpu.c,v 1.6 2014/04/12 19:01:49 jakllsch Exp $      */
 
 /*-
  * Copyright (c) 2009 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: db_cpu.c,v 1.5 2013/11/24 21:58:38 rmind Exp $");
+__KERNEL_RCSID(0, "$NetBSD: db_cpu.c,v 1.6 2014/04/12 19:01:49 jakllsch Exp $");
 
 #ifndef _KERNEL
 #include <stdbool.h>
@@ -42,23 +42,37 @@
 
 #include <ddb/ddb.h>
 
-static struct cpu_info **cpu_info_addr;
+static int             db_ncpu;
+static struct cpu_info **db_cpu_infos;
+
+static void
+db_cpu_init(void)
+{
+       db_expr_t addr;
+
+       db_value_of_name("ncpu", &addr);
+       db_read_bytes((db_addr_t)addr, sizeof(db_ncpu), (char *)&db_ncpu);
+
+       db_value_of_name("cpu_infos", &addr);
+       db_read_bytes((db_addr_t)addr, sizeof(db_cpu_infos),
+           (char *)&db_cpu_infos);
+}
 
 static struct cpu_info *
-db_cpu_index(u_int idx)
+db_cpu_by_index(u_int idx)
 {
-       db_addr_t slot_addr = (db_addr_t)(cpu_info_addr + idx);
        struct cpu_info *ci;
 
-       db_read_bytes(slot_addr, sizeof(ci), (char *)&ci);
+       db_read_bytes((db_addr_t)&db_cpu_infos[idx], sizeof(ci), (char *)&ci);
        return ci;
 }
 
 struct cpu_info *
 db_cpu_first(void)
 {
-       db_value_of_name("cpu_infos", (db_expr_t *)&cpu_info_addr);
-       return db_cpu_index(0);
+
+       db_cpu_init();
+       return db_cpu_by_index(0);
 }
 
 struct cpu_info *
@@ -67,5 +81,7 @@
        u_int idx;
 
        db_read_bytes((db_addr_t)&ci->ci_index, sizeof(idx), (char *)&idx);
-       return db_cpu_index(idx + 1);
+       if ((idx + 1) >= ncpu)
+               return NULL;
+       return db_cpu_by_index(idx + 1);
 }