mm, kprobes: generalize and rename notify_page_fault() as kprobe_page_fault()

Architectures which support kprobes have very similar boilerplate around
calling kprobe_fault_handler(). Use a helper function in kprobes.h to
unify them, based on the x86 code.

This changes the behaviour for other architectures when preemption is
enabled. Previously, they would have disabled preemption while calling
the kprobe handler. However, preemption would be disabled if this fault
was due to a kprobe, so we know the fault was not due to a kprobe
handler and can simply return failure.

This behaviour was introduced in commit a980c0ef9f6d ("x86/kprobes:
Refactor kprobes_fault() like kprobe_exceptions_notify()")

[[e-mail]: export kprobe_fault_handler()]
Link: http://lkml.kernel.org/r/[e-mail]
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Anshuman Khandual <[e-mail]>
Reviewed-by: Dave Hansen <[e-mail]>
Cc: Michal Hocko <[e-mail]>
Cc: Matthew Wilcox <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Christophe Leroy <[e-mail]>
Cc: Stephen Rothwell <[e-mail]>
Cc: Andrey Konovalov <[e-mail]>
Cc: Michael Ellerman <[e-mail]>
Cc: Paul Mackerras <[e-mail]>
Cc: Russell King <[e-mail]>
Cc: Catalin Marinas <[e-mail]>
Cc: Will Deacon <[e-mail]>
Cc: Tony Luck <[e-mail]>
Cc: Fenghua Yu <[e-mail]>
Cc: Martin Schwidefsky <[e-mail]>
Cc: Heiko Carstens <[e-mail]>
Cc: Yoshinori Sato <[e-mail]>
Cc: "David S. Miller" <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Andy Lutomirski <[e-mail]>
Cc: Vineet Gupta <[e-mail]>
Cc: James Hogan <[e-mail]>
Cc: Paul Burton <[e-mail]>
Cc: Ralf Baechle <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/arm/mm/fault.c

···
 
 #ifdef CONFIG_MMU
 
-#ifdef CONFIG_KPROBES
-static inline int notify_page_fault(struct pt_regs *regs, unsigned int fsr)
-{
-	int ret = 0;
-
-	if (!user_mode(regs)) {
-		/* kprobe_running() needs smp_processor_id() */
-		preempt_disable();
-		if (kprobe_running() && kprobe_fault_handler(regs, fsr))
-			ret = 1;
-		preempt_enable();
-	}
-
-	return ret;
-}
-#else
-static inline int notify_page_fault(struct pt_regs *regs, unsigned int fsr)
-{
-	return 0;
-}
-#endif
-
 /*
  * This is useful to dump out the page tables associated with
  * 'addr' in mm 'mm'.
···
 	vm_fault_t fault;
 	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 
-	if (notify_page_fault(regs, fsr))
+	if (kprobe_page_fault(regs, fsr))
 		return 0;
 
 	tsk = current;

arch/arm64/mm/fault.c

···
 	return debug_fault_info + DBG_ESR_EVT(esr);
 }
 
-#ifdef CONFIG_KPROBES
-static inline int notify_page_fault(struct pt_regs *regs, unsigned int esr)
-{
-	int ret = 0;
-
-	/* kprobe_running() needs smp_processor_id() */
-	if (!user_mode(regs)) {
-		preempt_disable();
-		if (kprobe_running() && kprobe_fault_handler(regs, esr))
-			ret = 1;
-		preempt_enable();
-	}
-
-	return ret;
-}
-#else
-static inline int notify_page_fault(struct pt_regs *regs, unsigned int esr)
-{
-	return 0;
-}
-#endif
-
 static void data_abort_decode(unsigned int esr)
 {
 	pr_alert("Data abort info:\n");
···
 	unsigned long vm_flags = VM_READ | VM_WRITE;
 	unsigned int mm_flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 
-	if (notify_page_fault(regs, esr))
+	if (kprobe_page_fault(regs, esr))
 		return 0;
 
 	/*

arch/ia64/mm/fault.c

···
 
 extern int die(char *, struct pt_regs *, long);
 
-#ifdef CONFIG_KPROBES
-static inline int notify_page_fault(struct pt_regs *regs, int trap)
-{
-	int ret = 0;
-
-	if (!user_mode(regs)) {
-		/* kprobe_running() needs smp_processor_id() */
-		preempt_disable();
-		if (kprobe_running() && kprobe_fault_handler(regs, trap))
-			ret = 1;
-		preempt_enable();
-	}
-
-	return ret;
-}
-#else
-static inline int notify_page_fault(struct pt_regs *regs, int trap)
-{
-	return 0;
-}
-#endif
-
 /*
  * Return TRUE if ADDRESS points at a page in the kernel's mapped segment
  * (inside region 5, on ia64) and that page is present.
···
 	/*
 	 * This is to handle the kprobes on user space access instructions
 	 */
-	if (notify_page_fault(regs, TRAP_BRKPT))
+	if (kprobe_page_fault(regs, TRAP_BRKPT))
 		return;
 
 	if (user_mode(regs))

arch/mips/include/asm/kprobes.h

···
 #define kretprobe_blacklist_size 0
 
 void arch_remove_kprobe(struct kprobe *p);
+int kprobe_fault_handler(struct pt_regs *regs, int trapnr);
 
 /* Architecture specific copy of original instruction*/
 struct arch_specific_insn {

arch/mips/kernel/kprobes.c

···
 	return 1;
 }
 
-static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
+int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 {
 	struct kprobe *cur = kprobe_running();
 	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();

arch/powerpc/mm/fault.c

···
 #include <asm/debug.h>
 #include <asm/kup.h>
 
-static inline bool notify_page_fault(struct pt_regs *regs)
-{
-	bool ret = false;
-
-#ifdef CONFIG_KPROBES
-	/* kprobe_running() needs smp_processor_id() */
-	if (!user_mode(regs)) {
-		preempt_disable();
-		if (kprobe_running() && kprobe_fault_handler(regs, 11))
-			ret = true;
-		preempt_enable();
-	}
-#endif /* CONFIG_KPROBES */
-
-	if (unlikely(debugger_fault_handler(regs)))
-		ret = true;
-
-	return ret;
-}
-
 /*
  * Check whether the instruction inst is a store using
  * an update addressing form which will update r1.
···
 	int is_write = page_fault_is_write(error_code);
 	vm_fault_t fault, major = 0;
 	bool must_retry = false;
+	bool kprobe_fault = kprobe_page_fault(regs, 11);
 
-	if (notify_page_fault(regs))
+	if (unlikely(debugger_fault_handler(regs) || kprobe_fault))
 		return 0;
 
 	if (unlikely(page_fault_is_bad(error_code))) {

arch/s390/mm/fault.c

···
 }
 early_initcall(fault_init);
 
-static inline int notify_page_fault(struct pt_regs *regs)
-{
-	int ret = 0;
-
-	/* kprobe_running() needs smp_processor_id() */
-	if (kprobes_built_in() && !user_mode(regs)) {
-		preempt_disable();
-		if (kprobe_running() && kprobe_fault_handler(regs, 14))
-			ret = 1;
-		preempt_enable();
-	}
-	return ret;
-}
-
 /*
  * Find out which address space caused the exception.
  */
···
 	 */
 	clear_pt_regs_flag(regs, PIF_PER_TRAP);
 
-	if (notify_page_fault(regs))
+	if (kprobe_page_fault(regs, 14))
 		return 0;
 
 	mm = tsk->mm;

arch/sh/mm/fault.c

···
 #include <asm/tlbflush.h>
 #include <asm/traps.h>
 
-static inline int notify_page_fault(struct pt_regs *regs, int trap)
-{
-	int ret = 0;
-
-	if (kprobes_built_in() && !user_mode(regs)) {
-		preempt_disable();
-		if (kprobe_running() && kprobe_fault_handler(regs, trap))
-			ret = 1;
-		preempt_enable();
-	}
-
-	return ret;
-}
-
 static void
 force_sig_info_fault(int si_signo, int si_code, unsigned long address)
 {
···
 	if (unlikely(fault_in_kernel_space(address))) {
 		if (vmalloc_fault(address) >= 0)
 			return;
-		if (notify_page_fault(regs, vec))
+		if (kprobe_page_fault(regs, vec))
 			return;
 
 		bad_area_nosemaphore(regs, error_code, address);
 		return;
 	}
 
-	if (unlikely(notify_page_fault(regs, vec)))
+	if (unlikely(kprobe_page_fault(regs, vec)))
 		return;
 
 	/* Only enable interrupts if they were on before the fault */

arch/sparc/mm/fault_64.c

···
 
 int show_unhandled_signals = 1;
 
-static inline __kprobes int notify_page_fault(struct pt_regs *regs)
-{
-	int ret = 0;
-
-	/* kprobe_running() needs smp_processor_id() */
-	if (kprobes_built_in() && !user_mode(regs)) {
-		preempt_disable();
-		if (kprobe_running() && kprobe_fault_handler(regs, 0))
-			ret = 1;
-		preempt_enable();
-	}
-	return ret;
-}
-
 static void __kprobes unhandled_fault(unsigned long address,
 				      struct task_struct *tsk,
 				      struct pt_regs *regs)
···
 
 	fault_code = get_thread_fault_code();
 
-	if (notify_page_fault(regs))
+	if (kprobe_page_fault(regs, 0))
 		goto exit_exception;
 
 	si_code = SEGV_MAPERR;

arch/x86/mm/fault.c

···
 	return 0;
 }
 
-static nokprobe_inline int kprobes_fault(struct pt_regs *regs)
-{
-	if (!kprobes_built_in())
-		return 0;
-	if (user_mode(regs))
-		return 0;
-	/*
-	 * To be potentially processing a kprobe fault and to be allowed to call
-	 * kprobe_running(), we have to be non-preemptible.
-	 */
-	if (preemptible())
-		return 0;
-	if (!kprobe_running())
-		return 0;
-	return kprobe_fault_handler(regs, X86_TRAP_PF);
-}
-
 /*
  * Prefetch quirks:
  *
···
 		return;
 
 	/* kprobes don't want to hook the spurious faults: */
-	if (kprobes_fault(regs))
+	if (kprobe_page_fault(regs, X86_TRAP_PF))
 		return;
 
 	/*
···
 	mm = tsk->mm;
 
 	/* kprobes don't want to hook the spurious faults: */
-	if (unlikely(kprobes_fault(regs)))
+	if (unlikely(kprobe_page_fault(regs, X86_TRAP_PF)))
 		return;
 
 	/*

include/linux/kprobes.h

···
 }
 #endif
 
+/* Returns true if kprobes handled the fault */
+static nokprobe_inline bool kprobe_page_fault(struct pt_regs *regs,
+					      unsigned int trap)
+{
+	if (!kprobes_built_in())
+		return false;
+	if (user_mode(regs))
+		return false;
+	/*
+	 * To be potentially processing a kprobe fault and to be allowed
+	 * to call kprobe_running(), we have to be non-preemptible.
+	 */
+	if (preemptible())
+		return false;
+	if (!kprobe_running())
+		return false;
+	return kprobe_fault_handler(regs, trap);
+}
+
 #endif /* _LINUX_KPROBES_H */