kprobes: Introduce is_kprobe_fault()

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

avr32 was the only arch without the preempt_disable/enable pair in its notify_page_fault implementation. This should be checked by avr32 people.

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. This has been preserved in this patch, s390 people should check if error_code really was intended.

Signed-off-by Harvey Harrison <[email protected]>

---
Andrew, this came up when discussing some x86 fault unification work, figured you were the right person to feed this through.

At least the diffstat says I did something right. Patch against current Linus tree.

 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_32.c  |   26 ++------------------------
 arch/x86/mm/fault_64.c  |   26 ++------------------------
 include/linux/kprobes.h |   19 +++++++++++++++++++
 8 files changed, 28 insertions(+), 161 deletions(-)

arch/avr32/mm/fault.c +1 -20

index 6560cb1..a95cce2 100644
@@ -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 (is_kprobe_fault(regs, ecr))
 		return;
 
 	address = sysreg_read(TLBEAR);

arch/ia64/mm/fault.c +1 -23

index 7571076..1696805 100644
@@ -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 (is_kprobe_fault(regs, TRAP_BRKPT))
 		return;
 
 	down_read(&mm->mmap_sem);

arch/powerpc/mm/fault.c +1 -24

index 8135da0..00df6f9 100644
@@ -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 (is_kprobe_fault(regs, 11))
 		return 0;
 
 	if (trap == 0x300) {

arch/s390/mm/fault.c +1 -24

index 2456b52..59d3f0e 100644
@@ -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 (is_kprobe_fault(regs, 14))
 		return;
 
 	tsk = current;

arch/sparc64/mm/fault.c +1 -22

index e2027f2..bb5c36a 100644
@@ -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 (is_kprobe_fault(regs, 0))
 		return;
 
 	si_code = SEGV_MAPERR;

arch/x86/mm/fault_32.c +2 -24

index a2273d4..f2e909b 100644
@@ -33,28 +33,6 @@
 
 extern void die(const char *,struct pt_regs *,long);
 
-#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_vm(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)
-{
-	return 0;
-}
-#endif
-
 /*
  * Return EIP plus the CS segment base.  The segment limit is also
  * adjusted, clamped to the kernel/user address space (whichever is

@@ -331,7 +309,7 @@ fastcall void __kprobes do_page_fault(struct pt_regs *regs,
 	if (unlikely(address >= TASK_SIZE)) {
 		if (!(error_code & 0x0000000d) && vmalloc_fault(address) >= 0)
 			return;
-		if (notify_page_fault(regs))
+		if (is_kprobe_fault(regs, 14))
 			return;
 		/*
 		 * Don't take the mm semaphore here. If we fixup a prefetch

@@ -340,7 +318,7 @@ fastcall void __kprobes do_page_fault(struct pt_regs *regs,
 		goto bad_area_nosemaphore;
 	}
 
-	if (notify_page_fault(regs))
+	if (is_kprobe_fault(regs, 14))
 		return;
 
 	/* It's safe to allow irq's after cr2 has been saved and the vmalloc

arch/x86/mm/fault_64.c +2 -24

index 0e26230..376e218 100644
@@ -41,28 +41,6 @@
 #define PF_RSVD	(1<<3)
 #define PF_INSTR	(1<<4)
 
-#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, 14))
-			ret = 1;
-		preempt_enable();
-	}
-
-	return ret;
-}
-#else
-static inline int notify_page_fault(struct pt_regs *regs)
-{
-	return 0;
-}
-#endif
-
 /* Sometimes the CPU reports invalid exceptions on prefetch.
    Check that here and ignore.
    Opcode checker based on code by Richard Brunner */

@@ -343,7 +321,7 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
 			if (vmalloc_fault(address) >= 0)
 				return;
 		}
-		if (notify_page_fault(regs))
+		if (is_kprobe_fault(regs, 14))
 			return;
 		/*
 		 * Don't take the mm semaphore here. If we fixup a prefetch

@@ -352,7 +330,7 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
 		goto bad_area_nosemaphore;
 	}
 
-	if (notify_page_fault(regs))
+	if (is_kprobe_fault(regs, 14))
 		return;
 
 	if (likely(regs->eflags & X86_EFLAGS_IF))

include/linux/kprobes.h +19 -0

index 8189158..65c1ffb 100644
@@ -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>

@@ -203,6 +204,20 @@ static inline struct kprobe *kprobe_running(void)
 	return (__get_cpu_var(current_kprobe));
 }
 
+/*
+ * If it is a kprobe pagefault we can not be premptible so return before
+ * calling kprobe_running() as it will assert on smp_processor_id if
+ * preemption is enabled.
+ */
+static inline int is_kprobe_fault(struct pt_regs *regs, int trapnr)
+{
+	if (!user_mode(regs) && !preemptible() && kprobe_running() &&
+	    kprobe_fault_handler(regs, trapnr))
+		return 1;
+	else
+		return 0;
+}
+
 static inline void reset_current_kprobe(void)
 {
 	__get_cpu_var(current_kprobe) = NULL;

@@ -237,6 +252,10 @@ static inline struct kprobe *kprobe_running(void)
 {
 	return NULL;
 }
+static inline int is_kprobe_fault(struct pt_regs *regs, int trapnr)
+{
+	return 0;
+}
 static inline int register_kprobe(struct kprobe *p)
 {
 	return -ENOSYS;

arch/x86/mm/fault_32.c +0 -0

index a2273d4..f2e909b 100644

arch/x86/mm/fault_32.c +2 -17

-		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)
-{
-	return 0;
-}
-#endif
-
 /*
  * Return EIP plus the CS segment base.  The segment limit is also
  * adjusted, clamped to the kernel/user address space (whichever is

@@ -331,7 +309,7 @@ fastcall void __kprobes do_page_fault(struct pt_regs *regs,
 	if (unlikely(address >= TASK_SIZE)) {
 		if (!(error_code & 0x0000000d) && vmalloc_fault(address) >= 0)
 			return;
-		if (notify_page_fault(regs))
+		if (is_kprobe_fault(regs, 14))
 			return;
 		/*
 		 * Don't take the mm semaphore here. If we fixup a prefetch

@@ -340,7 +318,7 @@ fastcall void __kprobes do_page_fault(struct pt_regs *regs,
 		goto bad_area_nosemaphore;
 	}
 
-	if (notify_page_fault(regs))
+	if (is_kprobe_fault(regs, 14))
 		return;
 
 	/* It's safe to allow irq's after cr2 has been saved and the vmalloc

include/linux/kprobes.h +15 -0

index 8189158..65c1ffb 100644
@@ -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>

@@ -203,6 +204,20 @@ static inline struct kprobe *kprobe_running(void)
 	return (__get_cpu_var(current_kprobe));
 }
 
+/*
+ * If it is a kprobe pagefault we can not be premptible so return before
+ * calling kprobe_running() as it will assert on smp_processor_id if
+ * preemption is enabled.
+ */
+static inline int is_kprobe_fault(struct pt_regs *regs, int trapnr)
+{
+	if (!user_mode(regs) && !preemptible() && kprobe_running() &&
+	    kprobe_fault_handler(regs, trapnr))
+		return 1;
+	else
+		return 0;
+}
+
 static inline void reset_current_kprobe(void)
 {
 	__get_cpu_var(current_kprobe) = NULL;

On Wed, Jan 02, 2008 at 08:05:14PM -0800, Harvey Harrison wrote:

Thanks for the cleanup...

...

Quoted 5 lines

arch/x86/mm/fault_32.c +0 -0

index a2273d4..f2e909b 100644

arch/x86/mm/fault_32.c line 42

Quoted 10 lines

arch/x86/mm/fault_32.c +0 -7

@@ -33,28 +33,6 @@
 
 extern void die(const char *,struct pt_regs *,long);
 
-#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_vm(regs)) {

		^^^^^^^^^^^

For x86_32, this check is important. See commit 6444541671bd821b950dbaafee70d65188198aa6 (Never allow int3 traps from V8086 mode to enter the kprobes handler) for precise reason why its user_mode_vm() and not user_mode() for x86_32.

You'll need to make room for this check in the generic macro below...