[PATCH] x86_64: Add compat_printk and sysctl to turn off compat layer warnings

Sometimes e.g. with crashme the compat layer warnings can be noisy.
Add a way to turn them off by gating all output through compat_printk
that checks a global sysctl. The default is not changed.

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

5 files changed, 32 insertions, 3 deletions

diff --git a/arch/x86_64/ia32/sys_ia32.c b/arch/x86_64/ia32/sys_ia32.c
index f182b20858e2..ee30557629dc 100644
--- a/arch/x86_64/ia32/sys_ia32.c
+++ b/arch/x86_64/ia32/sys_ia32.c
@@ -514,7 +514,7 @@ int sys32_ni_syscall(int call)
         static char lastcomm[sizeof(me->comm)];
 
         if (strncmp(lastcomm, me->comm, sizeof(lastcomm))) {
-                printk(KERN_INFO "IA32 syscall %d from %s not implemented\n",
+                compat_printk(KERN_INFO "IA32 syscall %d from %s not implemented\n",
                        call, me->comm);
                 strncpy(lastcomm, me->comm, sizeof(lastcomm));
         } 
@@ -916,7 +916,7 @@ long sys32_vm86_warning(void)
         struct task_struct *me = current;
         static char lastcomm[sizeof(me->comm)];
         if (strncmp(lastcomm, me->comm, sizeof(lastcomm))) {
-                printk(KERN_INFO "%s: vm86 mode not supported on 64 bit kernel\n",
+                compat_printk(KERN_INFO "%s: vm86 mode not supported on 64 bit kernel\n",
                        me->comm);
                 strncpy(lastcomm, me->comm, sizeof(lastcomm));
         } 
diff --git a/fs/compat.c b/fs/compat.c
index 7e7e5bc4f3cf..e31e9cf96647 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -55,6 +55,20 @@
 
 extern void sigset_from_compat(sigset_t *set, compat_sigset_t *compat);
 
+int compat_log = 1;
+
+int compat_printk(const char *fmt, ...)
+{
+        va_list ap;
+        int ret;
+        if (!compat_log)
+                return 0;
+        va_start(ap, fmt);
+        ret = vprintk(fmt, ap);
+        va_end(ap);
+        return ret;
+}
+
 /*
  * Not all architectures have sys_utime, so implement this in terms
  * of sys_utimes.
@@ -359,7 +373,7 @@ static void compat_ioctl_error(struct file *filp, unsigned int fd,
         sprintf(buf,"'%c'", (cmd>>24) & 0x3f);
         if (!isprint(buf[1]))
                 sprintf(buf, "%02x", buf[1]);
-        printk("ioctl32(%s:%d): Unknown cmd fd(%d) "
+        compat_printk("ioctl32(%s:%d): Unknown cmd fd(%d) "
                         "cmd(%08x){%s} arg(%08x) on %s\n",
                         current->comm, current->pid,
                         (int)fd, (unsigned int)cmd, buf,
diff --git a/include/linux/compat.h b/include/linux/compat.h
index dda1697ec753..9760753e662b 100644
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -226,5 +226,7 @@ static inline int compat_timespec_compare(struct compat_timespec *lhs,
 
 asmlinkage long compat_sys_adjtimex(struct compat_timex __user *utp);
 
+extern int compat_printk(const char *fmt, ...);
+
 #endif /* CONFIG_COMPAT */
 #endif /* _LINUX_COMPAT_H */
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 6a60770984e9..349ef908a222 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -148,9 +148,11 @@ enum
         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 */
+        KERN_COMPAT_LOG=73,     /* int: print compat layer  messages */
 };
 
 
+
 /* CTL_VM names: */
 enum
 {
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 2c0e65819448..f1a4eb1a655e 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -73,6 +73,7 @@ extern int printk_ratelimit_burst;
 extern int pid_max_min, pid_max_max;
 extern int sysctl_drop_caches;
 extern int percpu_pagelist_fraction;
+extern int compat_log;
 
 #if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86)
 int unknown_nmi_panic;
@@ -677,6 +678,16 @@ static ctl_table kern_table[] = {
                 .proc_handler   = &proc_dointvec,
         },
 #endif
+#ifdef CONFIG_COMPAT
+        {
+                .ctl_name       = KERN_COMPAT_LOG,
+                .procname       = "compat-log",
+                .data           = &compat_log,
+                .maxlen         = sizeof (int),
+                .mode           = 0644,
+                .proc_handler   = &proc_dointvec,
+        },
+#endif
         { .ctl_name = 0 }
 };