[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>

diff --git a/arch/ia64/kernel/unaligned.c b/arch/ia64/kernel/unaligned.c
index 1129138..1e35755 100644 (file)
--- a/arch/ia64/kernel/unaligned.c
+++ b/arch/ia64/kernel/unaligned.c
@@ -52,6 +52,15 @@ dump (const char *str, void *vp, size_t len)
 #define IA64_FIRST_ROTATING_FR 32
 #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:
  *
@@ -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())

diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 0e92bf7..bac61db 100644 (file)
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -147,6 +147,7 @@ enum
        KERN_SETUID_DUMPABLE=69, /* int: behaviour of dumps for setuid core */
        KERN_SPIN_RETRY=70,     /* int: number of spinlock retries */
        KERN_ACPI_VIDEO_FLAGS=71, /* int: flags for setting up video after ACPI sleep */
+       KERN_IA64_UNALIGNED=72, /* int: ia64 unaligned userland trap enable */
 };
 
 

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index c05a2b7..acf6c15 100644 (file)
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -124,6 +124,10 @@ extern int sysctl_hz_timer;
 extern int acct_parm[];
 #endif
 
+#ifdef CONFIG_IA64
+extern int no_unaligned_warning;
+#endif
+
 static int parse_table(int __user *, int, void __user *, size_t __user *, void __user *, size_t,
                       ctl_table *, void **);
 static int proc_doutsstring(ctl_table *table, int write, struct file *filp,
@@ -665,6 +669,16 @@ static ctl_table kern_table[] = {
                .mode           = 0644,
                .proc_handler   = &proc_dointvec,
        },
+#endif
+#ifdef CONFIG_IA64
+       {
+               .ctl_name       = KERN_IA64_UNALIGNED,
+               .procname       = "ignore-unaligned-usertrap",
+               .data           = &no_unaligned_warning,
+               .maxlen         = sizeof (int),
+               .mode           = 0644,
+               .proc_handler   = &proc_dointvec,
+       },
 #endif
        { .ctl_name = 0 }
 };