[PATCHv4] kprobes: Introduce kprobe_handle_fault()

[Harvey Harrison <harvey.harrison@gmail.com>]

Use a central kprobe_handle_fault() inline in kprobes.h to remove
all of the arch-dependant, practically identical implementations in
avr32, ia64, powerpc, s390, sparc64, and x86.

This patch removes the preempt_disable/enable pair around kprobe_running
which was originally added to avoid the assertion from smp_processor_id
which would be unreliable if preemption was enabled.

Kprobes can not be running if we are preemptible, so test explicitly
for preemption and bail out before hitting kprobe_running().

Style comments from Christoph Hellwig and Heiko Carstens included in
this version.

avr32 was the only arch without the preempt_disable/enable pair
in its notify_page_fault implementation.

This uncovered a possible bug in the s390 version as that purely
copied the x86 version unconditionally passing 14 as the trapnr
rather than the error_code parameter.

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
---
 arch/avr32/mm/fault.c   |   21 +--------------------
 arch/ia64/mm/fault.c    |   24 +-----------------------
 arch/powerpc/mm/fault.c |   25 +------------------------
 arch/s390/mm/fault.c    |   25 +------------------------
 arch/sparc64/mm/fault.c |   23 +----------------------
 arch/x86/mm/fault_64.c  |   23 ++---------------------
 include/linux/kprobes.h |   17 +++++++++++++++++
 7 files changed, 24 insertions(+), 134 deletions(-)

diff --git a/arch/avr32/mm/fault.c b/arch/avr32/mm/fault.c
index 6560cb1..e41953e 100644
--- a/arch/avr32/mm/fault.c
+++ b/arch/avr32/mm/fault.c
@@ -20,25 +20,6 @@
 #include <asm/tlb.h>
 #include <asm/uaccess.h>
 
-#ifdef CONFIG_KPROBES
-static inline int notify_page_fault(struct pt_regs *regs, int trap)
-{
-	int ret = 0;
-
-	if (!user_mode(regs)) {
-		if (kprobe_running() && kprobe_fault_handler(regs, trap))
-			ret = 1;
-	}
-
-	return ret;
-}
-#else
-static inline int notify_page_fault(struct pt_regs *regs, int trap)
-{
-	return 0;
-}
-#endif
-
 int exception_trace = 1;
 
 /*
@@ -66,7 +47,7 @@ asmlinkage void do_page_fault(unsigned long ecr, struct pt_regs *regs)
 	int code;
 	int fault;
 
-	if (notify_page_fault(regs, ecr))
+	if (kprobe_handle_fault(regs, ecr))
 		return;
 
 	address = sysreg_read(TLBEAR);
diff --git a/arch/ia64/mm/fault.c b/arch/ia64/mm/fault.c
index 7571076..bfc83e8 100644
--- a/arch/ia64/mm/fault.c
+++ b/arch/ia64/mm/fault.c
@@ -18,28 +18,6 @@
 
 extern void 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() && kprobes_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.
@@ -106,7 +84,7 @@ ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *re
 	/*
 	 * This is to handle the kprobes on user space access instructions
 	 */
-	if (notify_page_fault(regs, TRAP_BRKPT))
+	if (kprobe_handle_fault(regs, TRAP_BRKPT))
 		return;
 
 	down_read(&mm->mmap_sem);
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 8135da0..ff64bd3 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -39,29 +39,6 @@
 #include <asm/tlbflush.h>
 #include <asm/siginfo.h>
 
-
-#ifdef CONFIG_KPROBES
-static inline int notify_page_fault(struct pt_regs *regs)
-{
-	int ret = 0;
-
-	/* kprobe_running() needs smp_processor_id() */
-	if (!user_mode(regs)) {
-		preempt_disable();
-		if (kprobe_running() && kprobe_fault_handler(regs, 11))
-			ret = 1;
-		preempt_enable();
-	}
-
-	return ret;
-}
-#else
-static inline int notify_page_fault(struct pt_regs *regs)
-{
-	return 0;
-}
-#endif
-
 /*
  * Check whether the instruction at regs->nip is a store using
  * an update addressing form which will update r1.
@@ -164,7 +141,7 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
 	is_write = error_code & ESR_DST;
 #endif /* CONFIG_4xx || CONFIG_BOOKE */
 
-	if (notify_page_fault(regs))
+	if (kprobe_handle_fault(regs, 11))
 		return 0;
 
 	if (trap == 0x300) {
diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index 2456b52..a9033cf 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -51,29 +51,6 @@ extern int sysctl_userprocess_debug;
 
 extern void die(const char *,struct pt_regs *,long);
 
-#ifdef CONFIG_KPROBES
-static inline int notify_page_fault(struct pt_regs *regs, long err)
-{
-	int ret = 0;
-
-	/* kprobe_running() needs smp_processor_id() */
-	if (!user_mode(regs)) {
-		preempt_disable();
-		if (kprobe_running() && kprobe_fault_handler(regs, 14))
-			ret = 1;
-		preempt_enable();
-	}
-
-	return ret;
-}
-#else
-static inline int notify_page_fault(struct pt_regs *regs, long err)
-{
-	return 0;
-}
-#endif
-
-
 /*
  * Unlock any spinlocks which will prevent us from getting the
  * message out.
@@ -309,7 +286,7 @@ do_exception(struct pt_regs *regs, unsigned long error_code, int write)
 	int si_code;
 	int fault;
 
-	if (notify_page_fault(regs, error_code))
+	if (kprobe_handle_fault(regs, 14))
 		return;
 
 	tsk = current;
diff --git a/arch/sparc64/mm/fault.c b/arch/sparc64/mm/fault.c
index e2027f2..8467dd6 100644
--- a/arch/sparc64/mm/fault.c
+++ b/arch/sparc64/mm/fault.c
@@ -31,27 +31,6 @@
 #include <asm/sections.h>
 #include <asm/mmu_context.h>
 
-#ifdef CONFIG_KPROBES
-static inline int notify_page_fault(struct pt_regs *regs)
-{
-	int ret = 0;
-
-	/* kprobe_running() needs smp_processor_id() */
-	if (!user_mode(regs)) {
-		preempt_disable();
-		if (kprobe_running() && kprobe_fault_handler(regs, 0))
-			ret = 1;
-		preempt_enable();
-	}
-	return ret;
-}
-#else
-static inline int notify_page_fault(struct pt_regs *regs)
-{
-	return 0;
-}
-#endif
-
 /*
  * To debug kernel to catch accesses to certain virtual/physical addresses.
  * Mode = 0 selects physical watchpoints, mode = 1 selects virtual watchpoints.
@@ -280,7 +259,7 @@ asmlinkage void __kprobes do_sparc64_fault(struct pt_regs *regs)
 
 	fault_code = get_thread_fault_code();
 
-	if (notify_page_fault(regs))
+	if (kprobe_handle_fault(regs, 0))
 		return;
 
 	si_code = SEGV_MAPERR;
diff --git a/arch/x86/mm/fault_64.c b/arch/x86/mm/fault_64.c
index f681ff8..f81660f 100644
--- a/arch/x86/mm/fault_64.c
+++ b/arch/x86/mm/fault_64.c
@@ -45,25 +45,6 @@
 #define PF_RSVD		(1<<3)
 #define PF_INSTR	(1<<4)
 
-static inline int notify_page_fault(struct pt_regs *regs)
-{
-#ifdef CONFIG_KPROBES
-	int ret = 0;
-
-	/* kprobe_running() needs smp_processor_id() */
-	if (!user_mode(regs)) {
-		preempt_disable();
-		if (kprobe_running() && kprobe_fault_handler(regs, 14))
-			ret = 1;
-		preempt_enable();
-	}
-
-	return ret;
-#else
-	return 0;
-#endif
-}
-
 #ifdef CONFIG_X86_32
 /*
  * Return EIP plus the CS segment base.  The segment limit is also
@@ -468,7 +449,7 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
 			if (vmalloc_fault(address) >= 0)
 				return;
 		}
-		if (notify_page_fault(regs))
+		if (kprobe_handle_fault(regs, 14))
 			return;
 		/*
 		 * Don't take the mm semaphore here. If we fixup a prefetch
@@ -477,7 +458,7 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
 		goto bad_area_nosemaphore;
 	}
 
-	if (notify_page_fault(regs))
+	if (kprobe_handle_fault(regs, 14))
 		return;
 
 	if (likely(regs->flags & X86_EFLAGS_IF))
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index 6168c0a..e099426 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -36,6 +36,7 @@
 #include <linux/spinlock.h>
 #include <linux/rcupdate.h>
 #include <linux/mutex.h>
+#include <linux/hardirq.h>
 
 #ifdef CONFIG_KPROBES
 #include <asm/kprobes.h>
@@ -212,6 +213,18 @@ static inline struct kprobe *kprobe_running(void)
 	return (__get_cpu_var(current_kprobe));
 }
 
+/*
+ * If it is a kprobe pagefault we can not be preemptible so return before
+ * calling kprobe_running() as it will assert on smp_processor_id if
+ * preemption is enabled.
+ */
+static inline int kprobe_handle_fault(struct pt_regs *regs, int trapnr)
+{
+	if (!user_mode(regs) && !preemptible() && kprobe_running())
+		return kprobe_fault_handler(regs, trapnr);
+	return 0;
+}
+
 static inline void reset_current_kprobe(void)
 {
 	__get_cpu_var(current_kprobe) = NULL;
@@ -247,6 +260,10 @@ static inline struct kprobe *kprobe_running(void)
 {
 	return NULL;
 }
+static inline int kprobe_handle_fault(struct pt_regs *regs, int trapnr)
+{
+	return 0;
+}
 static inline int register_kprobe(struct kprobe *p)
 {
 	return -ENOSYS;
-- 
1.5.4.rc2.1164.g6451