Stop stack unwinding at non-kernel address

The stack unwinding is for kernel addresses only. If non-kernel address
encountered, it is usually a user space address, or non-address value
like a function call parameter. So stopping stack unwinding at non-kernel
address will decrease the invalid unwind results.

Before:
crash> gdb bt
 #0  0xffffffff816a8f65 in context_switch ...
 crash-utility#1  __schedule () ...
 crash-utility#2  0xffffffff816a94e9 in schedule ...
 crash-utility#3  0xffffffff816a86fd in schedule_hrtimeout_range_clock ...
 crash-utility#4  0xffffffff816a8733 in schedule_hrtimeout_range ...
 crash-utility#5  0xffffffff8124bb7e in ep_poll ...
 crash-utility#6  0xffffffff8124d00d in SYSC_epoll_wait ...
 crash-utility#7  SyS_epoll_wait ...
 crash-utility#8  <signal handler called>
 crash-utility#9  0x00007f0449407923 in ?? ()
 crash-utility#10 0xffff880100000001 in ?? ()
 crash-utility#11 0xffff880169b3c010 in ?? ()
 crash-utility#12 0x0000000000000040 in irq_stack_union ()
 crash-utility#13 0xffff880169b3c058 in ?? ()
 crash-utility#14 0xffff880169b3c048 in ?? ()
 crash-utility#15 0xffff880169b3c050 in ?? ()
 crash-utility#16 0x0000000000000000 in ?? ()

After:
crash> gdb bt
 #0  0xffffffff816a8f65 in context_switch ...
 crash-utility#1  __schedule () ...
 crash-utility#2  0xffffffff816a94e9 in schedule () ...
 crash-utility#3  0xffffffff816a86fd in schedule_hrtimeout_range_clock ...
 crash-utility#4  0xffffffff816a8733 in schedule_hrtimeout_range ...
 crash-utility#5  0xffffffff8124bb7e in ep_poll ...
 crash-utility#6  0xffffffff8124d00d in SYSC_epoll_wait ...
 crash-utility#7  SyS_epoll_wait ...
 crash-utility#8  <signal handler called>
 crash-utility#9  0x00007f0449407923 in ?? ()

Cc: Sourabh Jain <sourabhjain@linux.ibm.com>
Cc: Hari Bathini <hbathini@linux.ibm.com>
Cc: Mahesh J Salgaonkar <mahesh@linux.ibm.com>
Cc: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Cc: Lianbo Jiang <lijiang@redhat.com>
Cc: HAGIO KAZUHITO(萩尾 一仁) <k-hagio-ab@nec.com>
Cc: Tao Liu <ltao@redhat.com>
Cc: Alexey Makhalov <alexey.makhalov@broadcom.com>
Signed-off-by: Tao Liu <ltao@redhat.com>

defs.h

@@ -7902,6 +7902,7 @@ extern unsigned char *gdb_prettyprint_arrays;
 extern unsigned int *gdb_repeat_count_threshold;
 extern unsigned char *gdb_stop_print_at_null;
 extern unsigned int *gdb_output_radix;
+int is_kvaddr(ulong);
 
 /*
  *  gdb/top.c

gdb-10.2.patch

@@ -16171,3 +16171,29 @@ exit 0
  }
 
  /*
+--- gdb-10.2/gdb/frame.c.orig
++++ gdb-10.2/gdb/frame.c
+@@ -2331,6 +2331,10 @@ inside_entry_func (frame_info *this_frame)
+    This function should not contain target-dependent tests, such as
+    checking whether the program-counter is zero.  */
+
++#ifdef CRASH_MERGE
++extern "C" int is_kvaddr(ulong);
++#endif
++
+ struct frame_info *
+ get_prev_frame (struct frame_info *this_frame)
+ {
+@@ -2353,7 +2357,11 @@ get_prev_frame (struct frame_info *this_frame)
+     get_frame_id (this_frame);
+
+   frame_pc_p = get_frame_pc_if_available (this_frame, &frame_pc);
+-
++#ifdef CRASH_MERGE
++  if (!is_kvaddr(frame_pc)) {
++        return NULL;
++  }
++#endif
+   /* tausq/2004-12-07: Dummy frames are skipped because it doesn't make much
+      sense to stop unwinding at a dummy frame.  One place where a dummy
+      frame may have an address "inside_main_func" is on HPUX.  On HPUX, the

gdb_interface.c

@@ -947,6 +947,12 @@ gdb_lookup_module_symbol(ulong addr, ulong *offset)
 	}
 }
 
+int
+is_kvaddr(ulong addr)
+{
+	return IS_KVADDR(addr);
+}
+
 /*
  *  Used by gdb_interface() to catch gdb-related errors, if desired.
  */