[IA64] sysctl option to silence unaligned trap warnings

Allow sysadmin to disable all warnings about userland apps
making unaligned accesses by using:
 # echo 1 > /proc/sys/kernel/ignore-unaligned-usertrap
Rather than having to use prctl on a process by process basis.

Default behaivour leaves the warnings enabled.

Signed-off-by: Jes Sorensen <jes@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

1 files changed, 28 insertions, 3 deletions

diff --git a/arch/ia64/kernel/unaligned.c b/arch/ia64/kernel/unaligned.c
index 11291389684..1e357550c77 100644
--- a/arch/ia64/kernel/unaligned.c
+++ b/arch/ia64/kernel/unaligned.c
@@ -53,6 +53,15 @@ dump (const char *str, void *vp, size_t len)
 #define SIGN_EXT9               0xffffffffffffff00ul
 
 /*
+ *  sysctl settable hook which tells the kernel whether to honor the
+ *  IA64_THREAD_UAC_NOPRINT prctl.  Because this is user settable, we want
+ *  to allow the super user to enable/disable this for security reasons
+ *  (i.e. don't allow attacker to fill up logs with unaligned accesses).
+ */
+int no_unaligned_warning;
+static int noprint_warning;
+
+/*
  * For M-unit:
  *
  *  opcode |   m  |   x6    |
@@ -1324,8 +1333,9 @@ ia64_handle_unaligned (unsigned long ifa, struct pt_regs *regs)
                 if ((current->thread.flags & IA64_THREAD_UAC_SIGBUS) != 0)
                         goto force_sigbus;
 
-                if (!(current->thread.flags & IA64_THREAD_UAC_NOPRINT)
-                    && within_logging_rate_limit())
+                if (!no_unaligned_warning &&
+                    !(current->thread.flags & IA64_THREAD_UAC_NOPRINT) &&
+                    within_logging_rate_limit())
                 {
                         char buf[200];  /* comm[] is at most 16 bytes... */
                         size_t len;
@@ -1340,7 +1350,22 @@ ia64_handle_unaligned (unsigned long ifa, struct pt_regs *regs)
                         if (user_mode(regs))
                                 tty_write_message(current->signal->tty, buf);
                         buf[len-1] = '\0';      /* drop '\r' */
-                        printk(KERN_WARNING "%s", buf); /* watch for command names containing %s */
+                        /* watch for command names containing %s */
+                        printk(KERN_WARNING "%s", buf);
+                } else {
+                        if (no_unaligned_warning && !noprint_warning) {
+                                noprint_warning = 1;
+                                printk(KERN_WARNING "%s(%d) encountered an "
+                                       "unaligned exception which required\n"
+                                       "kernel assistance, which degrades "
+                                       "the performance of the application.\n"
+                                       "Unaligned exception warnings have "
+                                       "been disabled by the system "
+                                       "administrator\n"
+                                       "echo 0 > /proc/sys/kernel/ignore-"
+                                       "unaligned-usertrap to re-enable\n",
+                                       current->comm, current->pid);
+                        }
                 }
         } else {
                 if (within_logging_rate_limit())