[PATCH] i386 exceptions notifier for kprobes

This patch provides notifiers for i386 architecture exceptions.  This patch
has been ported from x86_64 architecture as suggested by Andi Kleen.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/i386/kernel/i386_ksyms.c

@@ -32,6 +32,7 @@
 #include <asm/tlbflush.h>
 #include <asm/nmi.h>
 #include <asm/ist.h>
+#include <asm/kdebug.h>
 
 extern void dump_thread(struct pt_regs *, struct user *);
 extern spinlock_t rtc_lock;
@@ -177,6 +178,7 @@ EXPORT_SYMBOL_GPL(unset_nmi_callback);
 extern int memcmp(const void *,const void *,__kernel_size_t);
 EXPORT_SYMBOL_NOVERS(memcmp);
 
+EXPORT_SYMBOL(register_die_notifier);
 #ifdef CONFIG_HAVE_DEC_LOCK
 EXPORT_SYMBOL(atomic_dec_and_lock);
 #endif

arch/i386/kernel/traps.c

@@ -48,6 +48,7 @@
 
 #include <asm/smp.h>
 #include <asm/arch_hooks.h>
+#include <asm/kdebug.h>
 
 #include <linux/irq.h>
 #include <linux/module.h>
@@ -92,6 +93,18 @@ asmlinkage void spurious_interrupt_bug(void);
 asmlinkage void machine_check(void);
 
 static int kstack_depth_to_print = 24;
+struct notifier_block *i386die_chain;
+static spinlock_t die_notifier_lock = SPIN_LOCK_UNLOCKED;
+
+int register_die_notifier(struct notifier_block *nb)
+{
+	int err = 0;
+	unsigned long flags;
+	spin_lock_irqsave(&die_notifier_lock, flags);
+	err = notifier_chain_register(&i386die_chain, nb);
+	spin_unlock_irqrestore(&die_notifier_lock, flags);
+	return err;
+}
 
 static int valid_stack_ptr(struct task_struct *task, void *p)
 {
@@ -333,6 +346,7 @@ void die(const char * str, struct pt_regs * regs, long err)
 #endif
 		if (nl)
 			printk("\n");
+	notify_die(DIE_OOPS, (char *)str, regs, err, 255, SIGSEGV);
 		show_registers(regs);
   	} else
 		printk(KERN_ERR "Recursive die() failure, output suppressed\n");
@@ -406,6 +420,9 @@ static inline void do_trap(int trapnr, int signr, char *str, int vm86,
 #define DO_ERROR(trapnr, signr, str, name) \
 asmlinkage void do_##name(struct pt_regs * regs, long error_code) \
 { \
+	if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr) \
+						== NOTIFY_OK) \
+		return; \
 	do_trap(trapnr, signr, str, 0, regs, error_code, NULL); \
 }
 
@@ -417,12 +434,18 @@ asmlinkage void do_##name(struct pt_regs * regs, long error_code) \
 	info.si_errno = 0; \
 	info.si_code = sicode; \
 	info.si_addr = (void __user *)siaddr; \
+	if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr) \
+						== NOTIFY_BAD) \
+		return; \
 	do_trap(trapnr, signr, str, 0, regs, error_code, &info); \
 }
 
 #define DO_VM86_ERROR(trapnr, signr, str, name) \
 asmlinkage void do_##name(struct pt_regs * regs, long error_code) \
 { \
+	if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr) \
+						== NOTIFY_OK) \
+		return; \
 	do_trap(trapnr, signr, str, 1, regs, error_code, NULL); \
 }
 
@@ -434,6 +457,9 @@ asmlinkage void do_##name(struct pt_regs * regs, long error_code) \
 	info.si_errno = 0; \
 	info.si_code = sicode; \
 	info.si_addr = (void __user *)siaddr; \
+	if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr) \
+						== NOTIFY_OK) \
+		return; \
 	do_trap(trapnr, signr, str, 1, regs, error_code, &info); \
 }
 
@@ -467,8 +493,12 @@ asmlinkage void do_general_protection(struct pt_regs * regs, long error_code)
 	return;
 
 gp_in_kernel:
-	if (!fixup_exception(regs))
+	if (!fixup_exception(regs)) {
+		if (notify_die(DIE_GPF, "general protection fault", regs,
+				error_code, 13, SIGSEGV) == NOTIFY_OK);
+			return;
 		die("general protection fault", regs, error_code);
+	}
 }
 
 static void mem_parity_error(unsigned char reason, struct pt_regs * regs)
@@ -538,6 +568,9 @@ static void default_do_nmi(struct pt_regs * regs)
 	unsigned char reason = get_nmi_reason();
  
 	if (!(reason & 0xc0)) {
+		if (notify_die(DIE_NMI_IPI, "nmi_ipi", regs, reason, 0, SIGINT)
+							== NOTIFY_BAD)
+			return;
 #ifdef CONFIG_X86_LOCAL_APIC
 		/*
 		 * Ok, so this is none of the documented NMI sources,
@@ -551,6 +584,8 @@ static void default_do_nmi(struct pt_regs * regs)
 		unknown_nmi_error(reason, regs);
 		return;
 	}
+	if (notify_die(DIE_NMI, "nmi", regs, reason, 0, SIGINT) == NOTIFY_BAD)
+		return;
 	if (reason & 0x80)
 		mem_parity_error(reason, regs);
 	if (reason & 0x40)
@@ -624,6 +659,9 @@ asmlinkage void do_debug(struct pt_regs * regs, long error_code)
 
 	__asm__ __volatile__("movl %%db6,%0" : "=r" (condition));
 
+	if (notify_die(DIE_DEBUG, "debug", regs, condition, error_code,
+					SIGTRAP) == NOTIFY_OK)
+		return;
 	/* It's safe to allow irq's after DR6 has been saved */
 	if (regs->eflags & X86_EFLAGS_IF)
 		local_irq_enable();

arch/i386/mm/fault.c

@@ -26,6 +26,7 @@
 #include <asm/uaccess.h>
 #include <asm/hardirq.h>
 #include <asm/desc.h>
+#include <asm/kdebug.h>
 
 extern void die(const char *,struct pt_regs *,long);
 
@@ -226,6 +227,9 @@ asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long error_code)
 	/* get the address */
 	__asm__("movl %%cr2,%0":"=r" (address));
 
+	if (notify_die(DIE_PAGE_FAULT, "page fault", regs, error_code, 14,
+					SIGSEGV) == NOTIFY_OK)
+		return;
 	/* It's safe to allow irq's after cr2 has been saved */
 	if (regs->eflags & (X86_EFLAGS_IF|VM_MASK))
 		local_irq_enable();

include/asm-i386/kdebug.h

+#ifndef _I386_KDEBUG_H
+#define _I386_KDEBUG_H 1
+
+/*
+ * Aug-05 2004 Ported by Prasanna S Panchamukhi <prasanna@in.ibm.com>
+ * from x86_64 architecture.
+ */
+#include <linux/notifier.h>
+
+struct pt_regs;
+
+struct die_args {
+	struct pt_regs *regs;
+	const char *str;
+	long err;
+	int trapnr;
+	int signr;
+};
+
+/* Note - you should never unregister because that can race with NMIs.
+   If you really want to do it first unregister - then synchronize_kernel - then free.
+  */
+int register_die_notifier(struct notifier_block *nb);
+extern struct notifier_block *i386die_chain;
+
+
+/* Grossly misnamed. */
+enum die_val {
+	DIE_OOPS = 1,
+	DIE_INT3,
+	DIE_DEBUG,
+	DIE_PANIC,
+	DIE_NMI,
+	DIE_DIE,
+	DIE_NMIWATCHDOG,
+	DIE_KERNELDEBUG,
+	DIE_TRAP,
+	DIE_GPF,
+	DIE_CALL,
+	DIE_NMI_IPI,
+	DIE_PAGE_FAULT,
+};
+
+static inline int notify_die(enum die_val val,char *str,struct pt_regs *regs,long err,int trap, int sig)
+{
+	struct die_args args = { .regs=regs, .str=str, .err=err, .trapnr=trap,.signr=sig };
+	return notifier_call_chain(&i386die_chain, val, &args);
+}
+
+#endif