[IA64] dump stack on kernel unaligned warnings

Often the cause of kernel unaligned access warnings is not
obvious from just the ip displayed in the warning.  This adds
the option via proc to dump the stack in addition to the warning.
The default is off (just display the 1 line warning).  To enable
the stack to be shown: echo 1 > /proc/sys/kernel/unaligned-dump-stack

Signed-off-by: Doug Chapman <doug.chapman@hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

2 files changed, 14 insertions, 1 deletions

diff --git a/arch/ia64/kernel/unaligned.c b/arch/ia64/kernel/unaligned.c
index ff0e7c10faa7..6db08599ebbc 100644
--- a/arch/ia64/kernel/unaligned.c
+++ b/arch/ia64/kernel/unaligned.c
@@ -59,6 +59,7 @@ dump (const char *str, void *vp, size_t len)
  *  (i.e. don't allow attacker to fill up logs with unaligned accesses).
  */
 int no_unaligned_warning;
+int unaligned_dump_stack;
 static int noprint_warning;
 
 /*
@@ -1371,9 +1372,12 @@ ia64_handle_unaligned (unsigned long ifa, struct pt_regs *regs)
                         }
                 }
         } else {
-                if (within_logging_rate_limit())
+                if (within_logging_rate_limit()) {
                         printk(KERN_WARNING "kernel unaligned access to 0x%016lx, ip=0x%016lx\n",
                                ifa, regs->cr_iip + ipsr->ri);
+                        if (unaligned_dump_stack)
+                                dump_stack();
+                }
                 set_fs(KERNEL_DS);
         }
 
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 3e38b74b6124..368d1638ee78 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -144,6 +144,7 @@ extern int acct_parm[];
 
 #ifdef CONFIG_IA64
 extern int no_unaligned_warning;
+extern int unaligned_dump_stack;
 #endif
 
 #ifdef CONFIG_RT_MUTEXES
@@ -781,6 +782,14 @@ static struct ctl_table kern_table[] = {
                 .mode           = 0644,
                 .proc_handler   = &proc_dointvec,
         },
+        {
+                .ctl_name       = CTL_UNNUMBERED,
+                .procname       = "unaligned-dump-stack",
+                .data           = &unaligned_dump_stack,
+                .maxlen         = sizeof (int),
+                .mode           = 0644,
+                .proc_handler   = &proc_dointvec,
+        },
 #endif
 #ifdef CONFIG_DETECT_SOFTLOCKUP
         {