5 files changed, 10 insertions, 65 deletions

diff --git a/Documentation/x86_64/boot-options.txt b/Documentation/x86_64/boot-options.txt
index aaabb5883ab8..e566affeed7f 100644
--- a/Documentation/x86_64/boot-options.txt
+++ b/Documentation/x86_64/boot-options.txt
@@ -193,6 +193,9 @@ Debugging
 
   kstack=N   Print that many words from the kernel stack in oops dumps.
 
+  pagefaulttrace Dump all page faults. Only useful for extreme debugging
+                and will create a lot of output.
+
 Misc
 
   noreplacement  Don't replace instructions with more appropiate ones
diff --git a/arch/x86_64/Kconfig.debug b/arch/x86_64/Kconfig.debug
index 9cf1410d2f5a..3ccf6f4d1068 100644
--- a/arch/x86_64/Kconfig.debug
+++ b/arch/x86_64/Kconfig.debug
@@ -2,15 +2,6 @@ menu "Kernel hacking"
 
 source "lib/Kconfig.debug"
 
-# !SMP for now because the context switch early causes GPF in segment reloading
-# and the GS base checking does the wrong thing then, causing a hang.
-config CHECKING
-        bool "Additional run-time checks"
-        depends on DEBUG_KERNEL && !SMP
-        help
-          Enables some internal consistency checks for kernel debugging.
-          You should normally say N.
-
 config INIT_DEBUG
         bool "Debug __init statements"
         depends on DEBUG_KERNEL
diff --git a/arch/x86_64/kernel/traps.c b/arch/x86_64/kernel/traps.c
index 4a836384dd0f..bf337f493189 100644
--- a/arch/x86_64/kernel/traps.c
+++ b/arch/x86_64/kernel/traps.c
@@ -428,19 +428,6 @@ static void __kprobes do_trap(int trapnr, int signr, char *str,
 {
         conditional_sti(regs);
 
-#ifdef CONFIG_CHECKING
-       { 
-               unsigned long gs; 
-               struct x8664_pda *pda = cpu_pda + safe_smp_processor_id(); 
-               rdmsrl(MSR_GS_BASE, gs); 
-               if (gs != (unsigned long)pda) { 
-                       wrmsrl(MSR_GS_BASE, pda); 
-                       printk("%s: wrong gs %lx expected %p rip %lx\n", str, gs, pda,
-                              regs->rip);
-               }
-       }
-#endif
-
         if (user_mode(regs)) {
                 struct task_struct *tsk = current;
 
@@ -513,20 +500,6 @@ asmlinkage void __kprobes do_general_protection(struct pt_regs * regs,
 {
         conditional_sti(regs);
 
-#ifdef CONFIG_CHECKING
-       { 
-               unsigned long gs; 
-               struct x8664_pda *pda = cpu_pda + safe_smp_processor_id(); 
-               rdmsrl(MSR_GS_BASE, gs); 
-               if (gs != (unsigned long)pda) { 
-                       wrmsrl(MSR_GS_BASE, pda); 
-                       oops_in_progress++;
-                       printk("general protection handler: wrong gs %lx expected %p\n", gs, pda);
-                       oops_in_progress--;
-               }
-       }
-#endif
-
         if (user_mode(regs)) {
                 struct task_struct *tsk = current;
 
@@ -665,19 +638,6 @@ asmlinkage void __kprobes do_debug(struct pt_regs * regs,
         struct task_struct *tsk = current;
         siginfo_t info;
 
-#ifdef CONFIG_CHECKING
-       { 
-               /* RED-PEN interaction with debugger - could destroy gs */
-               unsigned long gs; 
-               struct x8664_pda *pda = cpu_pda + safe_smp_processor_id(); 
-               rdmsrl(MSR_GS_BASE, gs); 
-               if (gs != (unsigned long)pda) { 
-                       wrmsrl(MSR_GS_BASE, pda); 
-                       printk("debug handler: wrong gs %lx expected %p\n", gs, pda);
-               }
-       }
-#endif
-
         get_debugreg(condition, 6);
 
         if (notify_die(DIE_DEBUG, "debug", regs, condition, error_code,
diff --git a/arch/x86_64/mm/fault.c b/arch/x86_64/mm/fault.c
index b75b872ec154..3a63707a698b 100644
--- a/arch/x86_64/mm/fault.c
+++ b/arch/x86_64/mm/fault.c
@@ -308,18 +308,6 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
         unsigned long flags;
         siginfo_t info;
 
-#ifdef CONFIG_CHECKING
-        { 
-                unsigned long gs; 
-                struct x8664_pda *pda = cpu_pda + stack_smp_processor_id(); 
-                rdmsrl(MSR_GS_BASE, gs); 
-                if (gs != (unsigned long)pda) { 
-                        wrmsrl(MSR_GS_BASE, pda); 
-                        printk("page_fault: wrong gs %lx expected %p\n", gs, pda);
-                }
-        }
-#endif
-
         /* get the address */
         __asm__("movq %%cr2,%0":"=r" (address));
         if (notify_die(DIE_PAGE_FAULT, "page fault", regs, error_code, 14,
@@ -571,3 +559,10 @@ do_sigbus:
         force_sig_info(SIGBUS, &info, tsk);
         return;
 }
+
+static int __init enable_pagefaulttrace(char *str)
+{
+        page_fault_trace = 1;
+        return 0;
+}
+__setup("pagefaulttrace", enable_pagefaulttrace);
diff --git a/arch/x86_64/mm/init.c b/arch/x86_64/mm/init.c
index 854a41b8372b..286f6a624c3a 100644
--- a/arch/x86_64/mm/init.c
+++ b/arch/x86_64/mm/init.c
@@ -565,10 +565,6 @@ extern int exception_trace, page_fault_trace;
 static ctl_table debug_table2[] = {
         { 99, "exception-trace", &exception_trace, sizeof(int), 0644, NULL,
           proc_dointvec },
-#ifdef CONFIG_CHECKING
-        { 100, "page-fault-trace", &page_fault_trace, sizeof(int), 0644, NULL,
-          proc_dointvec },
-#endif
         { 0, }
 };