[RFC] Kprobes for book-e

[Sulibhavi, Madhvesh]

Hi Kumar,

I could switch to different version of binutils and
boot the recent git for ebony target. The kprobes
booke patches attached below got applied and
i didnot see any issues.  These patches can be 
now pushed to main line?

Below is the revised patch set after addressing some 
cleanups in traps.c and bug fixes to kprobes.c discussed 
earlier. Also added the support to Documentation/kprobes.txt 
and KRETPROBES check in powerpc/Kconfig file.

-Madhvesh

---------------------------------------------------------------------
arch/powerpc/kernel/kprobes.c |   35 +++++++++++++++++++++++++++++++----
 arch/powerpc/kernel/misc_32.S |    2 +-
 arch/powerpc/kernel/traps.c   |   26 +++++++++++++++++++++++++-
 3 files changed, 57 insertions(+), 6 deletions(-)

Index: b/arch/powerpc/kernel/kprobes.c
===================================================================
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -35,6 +35,21 @@
 #include <asm/sstep.h>
 #include <asm/uaccess.h>
 
+
+#if defined(CONFIG_4xx) || defined(CONFIG_BOOKE)
+#define single_stepping(regs)	(current->thread.dbcr0 & DBCR0_IC)
+#define clear_single_step(regs)	(current->thread.dbcr0 &=
~DBCR0_IC)
+#else
+#define single_stepping(regs)	((regs)->msr & MSR_SE)
+#define clear_single_step(regs)	((regs)->msr &= ~MSR_SE)
+#endif
+
+#ifdef CONFIG_BOOKE
+#define MSR_SINGLESTEP	(MSR_DE)
+#else
+#define MSR_SINGLESTEP	(MSR_SE)
+#endif
+
 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
 
@@ -53,7 +68,8 @@ int __kprobes arch_prepare_kprobe(struct
 		ret = -EINVAL;
 	}
 
-	/* insn must be on a special executable page on ppc64 */
+	/* insn must be on a special executable page on ppc64.  This is
+	 * explicitly not required on ppc32 (right now), but it doesn't
hurt */
 	if (!ret) {
 		p->ainsn.insn = get_insn_slot();
 		if (!p->ainsn.insn)
@@ -95,7 +111,14 @@ void __kprobes arch_remove_kprobe(struct
 
 static void __kprobes prepare_singlestep(struct kprobe *p, struct
pt_regs *regs)
 {
+#ifdef CONFIG_BOOKE
+	regs->msr &= ~(MSR_EE); /* Turn off 'Externel Interrupt' bits */
+	regs->msr &= ~(MSR_CE); /* Turn off 'Critical Interrupt' bits */
+	regs->msr |= MSR_DE;
+	mtspr(SPRN_DBCR0, mfspr(SPRN_DBCR0) | DBCR0_IC | DBCR0_IDM);
+#else
 	regs->msr |= MSR_SE;
+#endif
 
 	/*
 	 * On powerpc we should single step on the original
@@ -158,7 +181,7 @@ static int __kprobes kprobe_handler(stru
 			kprobe_opcode_t insn = *p->ainsn.insn;
 			if (kcb->kprobe_status == KPROBE_HIT_SS &&
 					is_trap(insn)) {
-				regs->msr &= ~MSR_SE;
+				regs->msr &= ~MSR_SINGLESTEP; /* Turn
off 'trace' bits */
 				regs->msr |= kcb->kprobe_saved_msr;
 				goto no_kprobe;
 			}
@@ -398,7 +421,7 @@ out:
 	 * will have SE set, in which case, continue the remaining
processing
 	 * of do_debug, as if this is not a probe hit.
 	 */
-	if (regs->msr & MSR_SE)
+	if (single_stepping(regs))
 		return 0;
 
 	return 1;
@@ -421,7 +444,7 @@ int __kprobes kprobe_fault_handler(struc
 		 * normal page fault.
 		 */
 		regs->nip = (unsigned long)cur->addr;
-		regs->msr &= ~MSR_SE;
+		regs->msr &= ~MSR_SINGLESTEP; /* Turn off 'trace' bits
*/
 		regs->msr |= kcb->kprobe_saved_msr;
 		if (kcb->kprobe_status == KPROBE_REENTER)
 			restore_previous_kprobe(kcb);
Index: b/arch/powerpc/kernel/misc_32.S
===================================================================
--- a/arch/powerpc/kernel/misc_32.S
+++ b/arch/powerpc/kernel/misc_32.S
@@ -489,7 +489,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_UNIFIED_ID
  *
  * flush_icache_range(unsigned long start, unsigned long stop)
  */
-_GLOBAL(__flush_icache_range)
+_KPROBE(__flush_icache_range)
 BEGIN_FTR_SECTION
 	blr				/* for 601, do nothing */
 END_FTR_SECTION_IFSET(CPU_FTR_COHERENT_ICACHE)
Index: b/arch/powerpc/kernel/traps.c
===================================================================
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -1030,7 +1030,7 @@ void SoftwareEmulation(struct pt_regs *r
 
 #if defined(CONFIG_40x) || defined(CONFIG_BOOKE)
 
-void DebugException(struct pt_regs *regs, unsigned long debug_status)
+void __kprobes DebugException(struct pt_regs *regs, unsigned long
debug_status)
 {
 	if (debug_status & DBSR_IC) {	/* instruction completion */
 		regs->msr &= ~MSR_DE;
@@ -1041,6 +1041,12 @@ void DebugException(struct pt_regs *regs
 			mtspr(SPRN_DBCR0, mfspr(SPRN_DBCR0) &
~DBCR0_IC);
 			/* Clear the instruction completion event */
 			mtspr(SPRN_DBSR, DBSR_IC);
+#ifdef CONFIG_KPROBES
+			if (notify_die(DIE_SSTEP, "single_step", regs,
5,
+			       5, SIGTRAP) == NOTIFY_STOP) {
+				return;
+			}
+#endif
 			if (debugger_sstep(regs))
 				return;
 		}
Index: b/Documentation/kprobes.txt
===================================================================
--- a/Documentation/kprobes.txt
+++ b/Documentation/kprobes.txt
@@ -172,6 +172,7 @@ architectures:
 - ia64 (Does not support probes on instruction slot1.)
 - sparc64 (Return probes not yet implemented.)
 - arm
+- ppc32
 
 3. Configuring Kprobes
 
Index: b/arch/powerpc/Kconfig
===================================================================
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -108,7 +108,7 @@ config PPC
 	select HAVE_IDE
 	select HAVE_OPROFILE
 	select HAVE_KPROBES
-	select HAVE_KRETPROBES
+	select HAVE_KRETPROBES if (HAVE_KPROBES)
 	select HAVE_LMB
 
 config EARLY_PRINTK


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