[PATCH] Move kprobe [dis]arming into arch specific code

The architecture independent code of the current kprobes implementation is
arming and disarming kprobes at registration time.  The problem is that the
code is assuming that arming and disarming is a just done by a simple write
of some magic value to an address.  This is problematic for ia64 where our
instructions look more like structures, and we can not insert break points
by just doing something like:

*p->addr = BREAKPOINT_INSTRUCTION;

The following patch to 2.6.12-rc4-mm2 adds two new architecture dependent
functions:

     * void arch_arm_kprobe(struct kprobe *p)
     * void arch_disarm_kprobe(struct kprobe *p)

and then adds the new functions for each of the architectures that already
implement kprobes (spar64/ppc64/i386/x86_64).

I thought arch_[dis]arm_kprobe was the most descriptive of what was really
happening, but each of the architectures already had a disarm_kprobe()
function that was really a "disarm and do some other clean-up items as
needed when you stumble across a recursive kprobe." So...  I took the
liberty of changing the code that was calling disarm_kprobe() to call
arch_disarm_kprobe(), and then do the cleanup in the block of code dealing
with the recursive kprobe case.

So far this patch as been tested on i386, x86_64, and ppc64, but still
needs to be tested in sparc64.
Signed-off-by: Rusty Lynch <rusty.lynch@intel.com>
Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/i386/kernel/kprobes.c

@@ -33,6 +33,7 @@
 #include <linux/ptrace.h>
 #include <linux/spinlock.h>
 #include <linux/preempt.h>
+#include <asm/cacheflush.h>
 #include <asm/kdebug.h>
 #include <asm/desc.h>
 
@@ -71,16 +72,25 @@ int arch_prepare_kprobe(struct kprobe *p)
 void arch_copy_kprobe(struct kprobe *p)
 {
 	memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
+	p->opcode = *p->addr;
 }
 
-void arch_remove_kprobe(struct kprobe *p)
+void arch_arm_kprobe(struct kprobe *p)
 {
+	*p->addr = BREAKPOINT_INSTRUCTION;
+	flush_icache_range((unsigned long) p->addr,
+			   (unsigned long) p->addr + sizeof(kprobe_opcode_t));
 }
 
-static inline void disarm_kprobe(struct kprobe *p, struct pt_regs *regs)
+void arch_disarm_kprobe(struct kprobe *p)
 {
 	*p->addr = p->opcode;
-	regs->eip = (unsigned long)p->addr;
+	flush_icache_range((unsigned long) p->addr,
+			   (unsigned long) p->addr + sizeof(kprobe_opcode_t));
+}
+
+void arch_remove_kprobe(struct kprobe *p)
+{
 }
 
 static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
@@ -177,7 +187,8 @@ static int kprobe_handler(struct pt_regs *regs)
 				unlock_kprobes();
 				goto no_kprobe;
 			}
-			disarm_kprobe(p, regs);
+			arch_disarm_kprobe(p);
+			regs->eip = (unsigned long)p->addr;
 			ret = 1;
 		} else {
 			p = current_kprobe;

arch/ppc64/kernel/kprobes.c

@@ -32,6 +32,7 @@
 #include <linux/ptrace.h>
 #include <linux/spinlock.h>
 #include <linux/preempt.h>
+#include <asm/cacheflush.h>
 #include <asm/kdebug.h>
 #include <asm/sstep.h>
 
@@ -61,16 +62,25 @@ int arch_prepare_kprobe(struct kprobe *p)
 void arch_copy_kprobe(struct kprobe *p)
 {
 	memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
+	p->opcode = *p->addr;
 }
 
-void arch_remove_kprobe(struct kprobe *p)
+void arch_arm_kprobe(struct kprobe *p)
 {
+	*p->addr = BREAKPOINT_INSTRUCTION;
+	flush_icache_range((unsigned long) p->addr,
+			   (unsigned long) p->addr + sizeof(kprobe_opcode_t));
 }
 
-static inline void disarm_kprobe(struct kprobe *p, struct pt_regs *regs)
+void arch_disarm_kprobe(struct kprobe *p)
 {
 	*p->addr = p->opcode;
-	regs->nip = (unsigned long)p->addr;
+	flush_icache_range((unsigned long) p->addr,
+			   (unsigned long) p->addr + sizeof(kprobe_opcode_t));
+}
+
+void arch_remove_kprobe(struct kprobe *p)
+{
 }
 
 static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
@@ -101,7 +111,8 @@ static inline int kprobe_handler(struct pt_regs *regs)
 				unlock_kprobes();
 				goto no_kprobe;
 			}
-			disarm_kprobe(p, regs);
+			arch_disarm_kprobe(p);
+			regs->nip = (unsigned long)p->addr;
 			ret = 1;
 		} else {
 			p = current_kprobe;

arch/sparc64/kernel/kprobes.c

@@ -6,7 +6,6 @@
 #include <linux/config.h>
 #include <linux/kernel.h>
 #include <linux/kprobes.h>
-
 #include <asm/kdebug.h>
 #include <asm/signal.h>
 
@@ -47,6 +46,19 @@ void arch_copy_kprobe(struct kprobe *p)
 {
 	p->ainsn.insn[0] = *p->addr;
 	p->ainsn.insn[1] = BREAKPOINT_INSTRUCTION_2;
+	p->opcode = *p->addr;
+}
+
+void arch_arm_kprobe(struct kprobe *p)
+{
+	*p->addr = BREAKPOINT_INSTRUCTION;
+	flushi(p->addr);
+}
+
+void arch_disarm_kprobe(struct kprobe *p)
+{
+	*p->addr = p->opcode;
+	flushi(p->addr);
 }
 
 void arch_remove_kprobe(struct kprobe *p)
@@ -78,17 +90,6 @@ static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
 	}
 }
 
-static inline void disarm_kprobe(struct kprobe *p, struct pt_regs *regs)
-{
-	*p->addr = p->opcode;
-	flushi(p->addr);
-
-	regs->tpc = (unsigned long) p->addr;
-	regs->tnpc = current_kprobe_orig_tnpc;
-	regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
-			current_kprobe_orig_tstate_pil);
-}
-
 static int kprobe_handler(struct pt_regs *regs)
 {
 	struct kprobe *p;
@@ -109,7 +110,11 @@ static int kprobe_handler(struct pt_regs *regs)
 				unlock_kprobes();
 				goto no_kprobe;
 			}
-			disarm_kprobe(p, regs);
+			arch_disarm_kprobe(p);
+			regs->tpc = (unsigned long) p->addr;
+			regs->tnpc = current_kprobe_orig_tnpc;
+			regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
+					current_kprobe_orig_tstate_pil);
 			ret = 1;
 		} else {
 			p = current_kprobe;

arch/x86_64/kernel/kprobes.c

@@ -39,7 +39,7 @@
 #include <linux/slab.h>
 #include <linux/preempt.h>
 #include <linux/moduleloader.h>
-
+#include <asm/cacheflush.h>
 #include <asm/pgtable.h>
 #include <asm/kdebug.h>
 
@@ -216,19 +216,28 @@ void arch_copy_kprobe(struct kprobe *p)
 		BUG_ON((s64) (s32) disp != disp); /* Sanity check.  */
 		*ripdisp = disp;
 	}
+	p->opcode = *p->addr;
 }
 
-void arch_remove_kprobe(struct kprobe *p)
+void arch_arm_kprobe(struct kprobe *p)
 {
-	up(&kprobe_mutex);
-	free_insn_slot(p->ainsn.insn);
-	down(&kprobe_mutex);
+	*p->addr = BREAKPOINT_INSTRUCTION;
+	flush_icache_range((unsigned long) p->addr,
+			   (unsigned long) p->addr + sizeof(kprobe_opcode_t));
 }
 
-static inline void disarm_kprobe(struct kprobe *p, struct pt_regs *regs)
+void arch_disarm_kprobe(struct kprobe *p)
 {
 	*p->addr = p->opcode;
-	regs->rip = (unsigned long)p->addr;
+	flush_icache_range((unsigned long) p->addr,
+			   (unsigned long) p->addr + sizeof(kprobe_opcode_t));
+}
+
+void arch_remove_kprobe(struct kprobe *p)
+{
+	up(&kprobe_mutex);
+	free_insn_slot(p->ainsn.insn);
+	down(&kprobe_mutex);
 }
 
 static void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
@@ -311,7 +320,8 @@ int kprobe_handler(struct pt_regs *regs)
 				unlock_kprobes();
 				goto no_kprobe;
 			}
-			disarm_kprobe(p, regs);
+			arch_disarm_kprobe(p);
+			regs->rip = (unsigned long)p->addr;
 			ret = 1;
 		} else {
 			p = current_kprobe;

include/linux/kprobes.h

@@ -165,6 +165,8 @@ static inline int kprobe_running(void)
 
 extern int arch_prepare_kprobe(struct kprobe *p);
 extern void arch_copy_kprobe(struct kprobe *p);
+extern void arch_arm_kprobe(struct kprobe *p);
+extern void arch_disarm_kprobe(struct kprobe *p);
 extern void arch_remove_kprobe(struct kprobe *p);
 extern void show_registers(struct pt_regs *regs);
 

kernel/kprobes.c

@@ -261,7 +261,7 @@ static inline void free_rp_inst(struct kretprobe *rp)
 static inline void add_aggr_kprobe(struct kprobe *ap, struct kprobe *p)
 {
 	ap->addr = p->addr;
-	ap->opcode = p->opcode;
+	memcpy(&ap->opcode, &p->opcode, sizeof(kprobe_opcode_t));
 	memcpy(&ap->ainsn, &p->ainsn, sizeof(struct arch_specific_insn));
 
 	ap->pre_handler = aggr_pre_handler;
@@ -304,10 +304,8 @@ static int register_aggr_kprobe(struct kprobe *old_p, struct kprobe *p)
 /* kprobe removal house-keeping routines */
 static inline void cleanup_kprobe(struct kprobe *p, unsigned long flags)
 {
-	*p->addr = p->opcode;
+	arch_disarm_kprobe(p);
 	hlist_del(&p->hlist);
-	flush_icache_range((unsigned long) p->addr,
-		   (unsigned long) p->addr + sizeof(kprobe_opcode_t));
 	spin_unlock_irqrestore(&kprobe_lock, flags);
 	arch_remove_kprobe(p);
 }
@@ -344,10 +342,8 @@ int register_kprobe(struct kprobe *p)
 	hlist_add_head(&p->hlist,
 		       &kprobe_table[hash_ptr(p->addr, KPROBE_HASH_BITS)]);
 
-	p->opcode = *p->addr;
-	*p->addr = BREAKPOINT_INSTRUCTION;
-	flush_icache_range((unsigned long) p->addr,
-			   (unsigned long) p->addr + sizeof(kprobe_opcode_t));
+  	arch_arm_kprobe(p);
+
 out:
 	spin_unlock_irqrestore(&kprobe_lock, flags);
 rm_kprobe: