[RFC PATCH -tip 0/9] kprobes: Cleanup jprobe implementation

[RFC PATCH -tip 0/9] kprobes: Cleanup jprobe implementation

[Masami Hiramatsu]

Hello,

Since we decided to remove jprobe from kernel last year,
its APIs are disabled and we worked on moving in-kernel
jprobe users to kprobes or trace-events. And now no jprobe
users are here anymore.

I think it is good time to get rid of jprobe implementation
from the kernel. However, I need other arch developers help
to complete it, since jprobe is implemented multi arch wide.
I can remove those code, but can not test all of those.

Here is the series of patches to show how to do that.
I tried to remove it from x86 tree. Basically we need to
do 3 things;

 - Remove jprobe functions (register/unregister,
   setjump/longjump) from generic/arch-dependent code.
   [1/9][2/9][3/9]
 - Remove break_handler related code.
   [4/9][5/9][6/9]
 - Do not disable preemption on exception handler
   [7/9][8/9][9/9]

The [3/9] and [6/9] are destractive changes except for x86
(means causes build errors) since those arch still have some
references of those functions. So we need to write patches
similar to [2/9] and [5/9] for each arch before applying those.
In this series I sorted it as this order just for review,
[3/9] and [6/9] should be applied after all archs have
been fixed.

Also, [7/9] is a kind of destractive, which changes required
behavior for the pre_handlers which changes regs->ip.
So we also need a patch similar to [7/9] for each arch too.
Fortunately, current in-tree such user is very limited, both
works only on x86. So it is not hurry, but we need to change
arch dependent code.

Thank you,

---

Masami Hiramatsu (9):
      kprobes: Remove jprobe API implementation
      x86: kprobes: Remove jprobe implementation
      kprobes: Remove jprobe data structure and interfaces
      kprobes: Ignore break_handler
      x86: kprobes: Ignore break_handler
      kprobes: Remove break_handler from struct kprobe
      x86: kprobes: Do not disable preempt on int3 path
      error-injection: Fix to not enabling preemption in pre_handler
      tracing: kprobes: Fix to not enabling preemption


 Documentation/kprobes.txt        |   13 ++--
 arch/x86/include/asm/kprobes.h   |    3 -
 arch/x86/kernel/kprobes/common.h |   10 ---
 arch/x86/kernel/kprobes/core.c   |  114 ++------------------------------------
 arch/x86/kernel/kprobes/ftrace.c |   21 +------
 arch/x86/kernel/kprobes/opt.c    |    1 
 include/linux/kprobes.h          |   54 ------------------
 kernel/fail_function.c           |    1 
 kernel/kprobes.c                 |  115 ++------------------------------------
 kernel/trace/trace_kprobe.c      |    3 -
 10 files changed, 20 insertions(+), 315 deletions(-)

--
Masami Hiramatsu

[RFC PATCH -tip 1/9] kprobes: Remove jprobe API implementation

[Masami Hiramatsu]

Remove jprobe API implementations which is no more used.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 include/linux/kprobes.h |    3 --
 kernel/kprobes.c        |   78 +----------------------------------------------
 2 files changed, 1 insertion(+), 80 deletions(-)

diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index 9440a2fc8893..b520baa65682 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -389,9 +389,6 @@ int register_kprobe(struct kprobe *p);
 void unregister_kprobe(struct kprobe *p);
 int register_kprobes(struct kprobe **kps, int num);
 void unregister_kprobes(struct kprobe **kps, int num);
-int setjmp_pre_handler(struct kprobe *, struct pt_regs *);
-int longjmp_break_handler(struct kprobe *, struct pt_regs *);
-void jprobe_return(void);
 unsigned long arch_deref_entry_point(void *);
 
 int register_kretprobe(struct kretprobe *rp);
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 102160ff5c66..6d5a7c29cf99 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1272,7 +1272,7 @@ NOKPROBE_SYMBOL(cleanup_rp_inst);
 
 /*
 * Add the new probe to ap->list. Fail if this is the
-* second jprobe at the address - two jprobes can't coexist
+* second break_handler at the address
 */
 static int add_new_kprobe(struct kprobe *ap, struct kprobe *p)
 {
@@ -1812,77 +1812,6 @@ unsigned long __weak arch_deref_entry_point(void *entry)
 	return (unsigned long)entry;
 }
 
-#if 0
-int register_jprobes(struct jprobe **jps, int num)
-{
-	int ret = 0, i;
-
-	if (num <= 0)
-		return -EINVAL;
-
-	for (i = 0; i < num; i++) {
-		ret = register_jprobe(jps[i]);
-
-		if (ret < 0) {
-			if (i > 0)
-				unregister_jprobes(jps, i);
-			break;
-		}
-	}
-
-	return ret;
-}
-EXPORT_SYMBOL_GPL(register_jprobes);
-
-int register_jprobe(struct jprobe *jp)
-{
-	unsigned long addr, offset;
-	struct kprobe *kp = &jp->kp;
-
-	/*
-	 * Verify probepoint as well as the jprobe handler are
-	 * valid function entry points.
-	 */
-	addr = arch_deref_entry_point(jp->entry);
-
-	if (kallsyms_lookup_size_offset(addr, NULL, &offset) && offset == 0 &&
-	    kprobe_on_func_entry(kp->addr, kp->symbol_name, kp->offset)) {
-		kp->pre_handler = setjmp_pre_handler;
-		kp->break_handler = longjmp_break_handler;
-		return register_kprobe(kp);
-	}
-
-	return -EINVAL;
-}
-EXPORT_SYMBOL_GPL(register_jprobe);
-
-void unregister_jprobe(struct jprobe *jp)
-{
-	unregister_jprobes(&jp, 1);
-}
-EXPORT_SYMBOL_GPL(unregister_jprobe);
-
-void unregister_jprobes(struct jprobe **jps, int num)
-{
-	int i;
-
-	if (num <= 0)
-		return;
-	mutex_lock(&kprobe_mutex);
-	for (i = 0; i < num; i++)
-		if (__unregister_kprobe_top(&jps[i]->kp) < 0)
-			jps[i]->kp.addr = NULL;
-	mutex_unlock(&kprobe_mutex);
-
-	synchronize_sched();
-	for (i = 0; i < num; i++) {
-		if (jps[i]->kp.addr)
-			__unregister_kprobe_bottom(&jps[i]->kp);
-	}
-}
-EXPORT_SYMBOL_GPL(unregister_jprobes);
-#endif
-
 #ifdef CONFIG_KRETPROBES
 /*
  * This kprobe pre_handler is registered with every kretprobe. When probe
@@ -2329,8 +2258,6 @@ static void report_probe(struct seq_file *pi, struct kprobe *p,
 
 	if (p->pre_handler == pre_handler_kretprobe)
 		kprobe_type = "r";
-	else if (p->pre_handler == setjmp_pre_handler)
-		kprobe_type = "j";
 	else
 		kprobe_type = "k";
 
@@ -2637,6 +2564,3 @@ late_initcall(debugfs_kprobe_init);
 #endif /* CONFIG_DEBUG_FS */
 
 module_init(init_kprobes);
-
-/* defined in arch/.../kernel/kprobes.c */
-EXPORT_SYMBOL_GPL(jprobe_return);

[RFC PATCH -tip 2/9] x86: kprobes: Remove jprobe implementation

[Masami Hiramatsu]

Remove arch dependent setjump/longjump functions
and unused fields in kprobe_ctlblk for jprobes.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 arch/x86/include/asm/kprobes.h |    3 -
 arch/x86/kernel/kprobes/core.c |   87 ----------------------------------------
 2 files changed, 90 deletions(-)

diff --git a/arch/x86/include/asm/kprobes.h b/arch/x86/include/asm/kprobes.h
index 367d99cff426..06782c2efa04 100644
--- a/arch/x86/include/asm/kprobes.h
+++ b/arch/x86/include/asm/kprobes.h
@@ -111,9 +111,6 @@ struct kprobe_ctlblk {
 	unsigned long kprobe_status;
 	unsigned long kprobe_old_flags;
 	unsigned long kprobe_saved_flags;
-	unsigned long *jprobe_saved_sp;
-	struct pt_regs jprobe_saved_regs;
-	kprobe_opcode_t jprobes_stack[MAX_STACK_SIZE];
 	struct prev_kprobe prev_kprobe;
 };
 
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index bd36f3c33cd0..f5b09b0850ad 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -1079,93 +1079,6 @@ int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val,
 }
 NOKPROBE_SYMBOL(kprobe_exceptions_notify);
 
-int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
-{
-	struct jprobe *jp = container_of(p, struct jprobe, kp);
-	unsigned long addr;
-	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
-
-	kcb->jprobe_saved_regs = *regs;
-	kcb->jprobe_saved_sp = stack_addr(regs);
-	addr = (unsigned long)(kcb->jprobe_saved_sp);
-
-	/*
-	 * As Linus pointed out, gcc assumes that the callee
-	 * owns the argument space and could overwrite it, e.g.
-	 * tailcall optimization. So, to be absolutely safe
-	 * we also save and restore enough stack bytes to cover
-	 * the argument area.
-	 * Use __memcpy() to avoid KASAN stack out-of-bounds reports as we copy
-	 * raw stack chunk with redzones:
-	 */
-	__memcpy(kcb->jprobes_stack, (kprobe_opcode_t *)addr, MIN_STACK_SIZE(addr));
-	regs->ip = (unsigned long)(jp->entry);
-
-	/*
-	 * jprobes use jprobe_return() which skips the normal return
-	 * path of the function, and this messes up the accounting of the
-	 * function graph tracer to get messed up.
-	 *
-	 * Pause function graph tracing while performing the jprobe function.
-	 */
-	pause_graph_tracing();
-	return 1;
-}
-NOKPROBE_SYMBOL(setjmp_pre_handler);
-
-void jprobe_return(void)
-{
-	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
-
-	/* Unpoison stack redzones in the frames we are going to jump over. */
-	kasan_unpoison_stack_above_sp_to(kcb->jprobe_saved_sp);
-
-	asm volatile (
-#ifdef CONFIG_X86_64
-			"       xchg   %%rbx,%%rsp	\n"
-#else
-			"       xchgl   %%ebx,%%esp	\n"
-#endif
-			"       int3			\n"
-			"       .globl jprobe_return_end\n"
-			"       jprobe_return_end:	\n"
-			"       nop			\n"::"b"
-			(kcb->jprobe_saved_sp):"memory");
-}
-NOKPROBE_SYMBOL(jprobe_return);
-NOKPROBE_SYMBOL(jprobe_return_end);
-
-int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
-{
-	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
-	u8 *addr = (u8 *) (regs->ip - 1);
-	struct jprobe *jp = container_of(p, struct jprobe, kp);
-	void *saved_sp = kcb->jprobe_saved_sp;
-
-	if ((addr > (u8 *) jprobe_return) &&
-	    (addr < (u8 *) jprobe_return_end)) {
-		if (stack_addr(regs) != saved_sp) {
-			struct pt_regs *saved_regs = &kcb->jprobe_saved_regs;
-			printk(KERN_ERR
-			       "current sp %p does not match saved sp %p\n",
-			       stack_addr(regs), saved_sp);
-			printk(KERN_ERR "Saved registers for jprobe %p\n", jp);
-			show_regs(saved_regs);
-			printk(KERN_ERR "Current registers\n");
-			show_regs(regs);
-			BUG();
-		}
-		/* It's OK to start function graph tracing again */
-		unpause_graph_tracing();
-		*regs = kcb->jprobe_saved_regs;
-		__memcpy(saved_sp, kcb->jprobes_stack, MIN_STACK_SIZE(saved_sp));
-		preempt_enable_no_resched();
-		return 1;
-	}
-	return 0;
-}
-NOKPROBE_SYMBOL(longjmp_break_handler);
-
 bool arch_within_kprobe_blacklist(unsigned long addr)
 {
 	return  (addr >= (unsigned long)__kprobes_text_start &&

[RFC PATCH -tip 3/9] kprobes: Remove jprobe data structure and interfaces

[Masami Hiramatsu]

Remove all interfaces of jprobe since it is no more
used.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 include/linux/kprobes.h |   44 --------------------------------------------
 1 file changed, 44 deletions(-)

diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index b520baa65682..f7a6c398b4bf 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -155,24 +155,6 @@ static inline int kprobe_ftrace(struct kprobe *p)
 }
 
 /*
- * Special probe type that uses setjmp-longjmp type tricks to resume
- * execution at a specified entry with a matching prototype corresponding
- * to the probed function - a trick to enable arguments to become
- * accessible seamlessly by probe handling logic.
- * Note:
- * Because of the way compilers allocate stack space for local variables
- * etc upfront, regardless of sub-scopes within a function, this mirroring
- * principle currently works only for probes placed on function entry points.
- */
-struct jprobe {
-	struct kprobe kp;
-	void *entry;	/* probe handling code to jump to */
-};
-
-/* For backward compatibility with old code using JPROBE_ENTRY() */
-#define JPROBE_ENTRY(handler)	(handler)
-
-/*
  * Function-return probe -
  * Note:
  * User needs to provide a handler function, and initialize maxactive.
@@ -436,9 +418,6 @@ static inline void unregister_kprobe(struct kprobe *p)
 static inline void unregister_kprobes(struct kprobe **kps, int num)
 {
 }
-static inline void jprobe_return(void)
-{
-}
 static inline int register_kretprobe(struct kretprobe *rp)
 {
 	return -ENOSYS;
@@ -465,20 +444,6 @@ static inline int enable_kprobe(struct kprobe *kp)
 	return -ENOSYS;
 }
 #endif /* CONFIG_KPROBES */
-static inline int register_jprobe(struct jprobe *p)
-{
-	return -ENOSYS;
-}
-static inline int register_jprobes(struct jprobe **jps, int num)
-{
-	return -ENOSYS;
-}
-static inline void unregister_jprobe(struct jprobe *p)
-{
-}
-static inline void unregister_jprobes(struct jprobe **jps, int num)
-{
-}
 static inline int disable_kretprobe(struct kretprobe *rp)
 {
 	return disable_kprobe(&rp->kp);
@@ -487,15 +452,6 @@ static inline int enable_kretprobe(struct kretprobe *rp)
 {
 	return enable_kprobe(&rp->kp);
 }
-static inline int disable_jprobe(struct jprobe *jp)
-{
-	return -ENOSYS;
-}
-static inline int enable_jprobe(struct jprobe *jp)
-{
-	return -ENOSYS;
-}
-
 #ifndef CONFIG_KPROBES
 static inline bool is_kprobe_insn_slot(unsigned long addr)
 {

[RFC PATCH -tip 4/9] kprobes: Ignore break_handler

[Masami Hiramatsu]

Ignore break_handler related code because it was only
used by jprobe and jprobe is removed.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 Documentation/kprobes.txt |    2 +-
 kernel/kprobes.c          |   39 +++++----------------------------------
 2 files changed, 6 insertions(+), 35 deletions(-)

diff --git a/Documentation/kprobes.txt b/Documentation/kprobes.txt
index 22208bf2386d..94df43224c6c 100644
--- a/Documentation/kprobes.txt
+++ b/Documentation/kprobes.txt
@@ -262,7 +262,7 @@ is optimized, that modification is ignored.  Thus, if you want to
 tweak the kernel's execution path, you need to suppress optimization,
 using one of the following techniques:
 
-- Specify an empty function for the kprobe's post_handler or break_handler.
+- Specify an empty function for the kprobe's post_handler.
 
 or
 
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 6d5a7c29cf99..889986ee3d06 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -627,8 +627,8 @@ static void optimize_kprobe(struct kprobe *p)
 	    (kprobe_disabled(p) || kprobes_all_disarmed))
 		return;
 
-	/* Both of break_handler and post_handler are not supported. */
-	if (p->break_handler || p->post_handler)
+	/* kprobes with post_handler can not be optimized */
+	if (p->post_handler)
 		return;
 
 	op = container_of(p, struct optimized_kprobe, kp);
@@ -1116,20 +1116,6 @@ static int aggr_fault_handler(struct kprobe *p, struct pt_regs *regs,
 }
 NOKPROBE_SYMBOL(aggr_fault_handler);
 
-static int aggr_break_handler(struct kprobe *p, struct pt_regs *regs)
-{
-	struct kprobe *cur = __this_cpu_read(kprobe_instance);
-	int ret = 0;
-
-	if (cur && cur->break_handler) {
-		if (cur->break_handler(cur, regs))
-			ret = 1;
-	}
-	reset_kprobe_instance();
-	return ret;
-}
-NOKPROBE_SYMBOL(aggr_break_handler);
-
 /* Walks the list and increments nmissed count for multiprobe case */
 void kprobes_inc_nmissed_count(struct kprobe *p)
 {
@@ -1270,24 +1256,15 @@ static void cleanup_rp_inst(struct kretprobe *rp)
 }
 NOKPROBE_SYMBOL(cleanup_rp_inst);
 
-/*
-* Add the new probe to ap->list. Fail if this is the
-* second break_handler at the address
-*/
+/* Add the new probe to ap->list */
 static int add_new_kprobe(struct kprobe *ap, struct kprobe *p)
 {
 	BUG_ON(kprobe_gone(ap) || kprobe_gone(p));
 
-	if (p->break_handler || p->post_handler)
+	if (p->post_handler)
 		unoptimize_kprobe(ap, true);	/* Fall back to normal kprobe */
 
-	if (p->break_handler) {
-		if (ap->break_handler)
-			return -EEXIST;
-		list_add_tail_rcu(&p->list, &ap->list);
-		ap->break_handler = aggr_break_handler;
-	} else
-		list_add_rcu(&p->list, &ap->list);
+	list_add_rcu(&p->list, &ap->list);
 	if (p->post_handler && !ap->post_handler)
 		ap->post_handler = aggr_post_handler;
 
@@ -1310,8 +1287,6 @@ static void init_aggr_kprobe(struct kprobe *ap, struct kprobe *p)
 	/* We don't care the kprobe which has gone. */
 	if (p->post_handler && !kprobe_gone(p))
 		ap->post_handler = aggr_post_handler;
-	if (p->break_handler && !kprobe_gone(p))
-		ap->break_handler = aggr_break_handler;
 
 	INIT_LIST_HEAD(&ap->list);
 	INIT_HLIST_NODE(&ap->hlist);
@@ -1706,8 +1681,6 @@ static int __unregister_kprobe_top(struct kprobe *p)
 		goto disarmed;
 	else {
 		/* If disabling probe has special handlers, update aggrprobe */
-		if (p->break_handler && !kprobe_gone(p))
-			ap->break_handler = NULL;
 		if (p->post_handler && !kprobe_gone(p)) {
 			list_for_each_entry_rcu(list_p, &ap->list, list) {
 				if ((list_p != p) && (list_p->post_handler))
@@ -1911,7 +1884,6 @@ int register_kretprobe(struct kretprobe *rp)
 	rp->kp.pre_handler = pre_handler_kretprobe;
 	rp->kp.post_handler = NULL;
 	rp->kp.fault_handler = NULL;
-	rp->kp.break_handler = NULL;
 
 	/* Pre-allocate memory for max kretprobe instances */
 	if (rp->maxactive <= 0) {
@@ -2034,7 +2006,6 @@ static void kill_kprobe(struct kprobe *p)
 		list_for_each_entry_rcu(kp, &p->list, list)
 			kp->flags |= KPROBE_FLAG_GONE;
 		p->post_handler = NULL;
-		p->break_handler = NULL;
 		kill_optimized_kprobe(p);
 	}
 	/*

[RFC PATCH -tip 5/9] x86: kprobes: Ignore break_handler

[Masami Hiramatsu]

Remove break_handler related code since that was used
only for jprobe and jprobe is removed now.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 arch/x86/kernel/kprobes/common.h |   10 ----------
 arch/x86/kernel/kprobes/core.c   |   13 ++-----------
 arch/x86/kernel/kprobes/ftrace.c |   16 ++--------------
 3 files changed, 4 insertions(+), 35 deletions(-)

diff --git a/arch/x86/kernel/kprobes/common.h b/arch/x86/kernel/kprobes/common.h
index ae38dccf0c8f..2b949f4fd4d8 100644
--- a/arch/x86/kernel/kprobes/common.h
+++ b/arch/x86/kernel/kprobes/common.h
@@ -105,14 +105,4 @@ static inline unsigned long __recover_optprobed_insn(kprobe_opcode_t *buf, unsig
 }
 #endif
 
-#ifdef CONFIG_KPROBES_ON_FTRACE
-extern int skip_singlestep(struct kprobe *p, struct pt_regs *regs,
-			   struct kprobe_ctlblk *kcb);
-#else
-static inline int skip_singlestep(struct kprobe *p, struct pt_regs *regs,
-				  struct kprobe_ctlblk *kcb)
-{
-	return 0;
-}
-#endif
 #endif
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index f5b09b0850ad..7663f23aa860 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -686,10 +686,8 @@ int kprobe_int3_handler(struct pt_regs *regs)
 			/*
 			 * If we have no pre-handler or it returned 0, we
 			 * continue with normal processing.  If we have a
-			 * pre-handler and it returned non-zero, it prepped
-			 * for calling the break_handler below on re-entry
-			 * for jprobe processing, so get out doing nothing
-			 * more here.
+			 * pre-handler and it returned non-zero, it modified
+			 * regs->ip so no singlestep is needed.
 			 */
 			if (!p->pre_handler || !p->pre_handler(p, regs))
 				setup_singlestep(p, regs, kcb, 0);
@@ -708,13 +706,6 @@ int kprobe_int3_handler(struct pt_regs *regs)
 		regs->ip = (unsigned long)addr;
 		preempt_enable_no_resched();
 		return 1;
-	} else if (kprobe_running()) {
-		p = __this_cpu_read(current_kprobe);
-		if (p->break_handler && p->break_handler(p, regs)) {
-			if (!skip_singlestep(p, regs, kcb))
-				setup_singlestep(p, regs, kcb, 0);
-			return 1;
-		}
 	} /* else: not a kprobe fault; let the kernel handle it */
 
 	preempt_enable_no_resched();
diff --git a/arch/x86/kernel/kprobes/ftrace.c b/arch/x86/kernel/kprobes/ftrace.c
index 8dc0161cec8f..c8696f2a583f 100644
--- a/arch/x86/kernel/kprobes/ftrace.c
+++ b/arch/x86/kernel/kprobes/ftrace.c
@@ -26,7 +26,7 @@
 #include "common.h"
 
 static nokprobe_inline
-void __skip_singlestep(struct kprobe *p, struct pt_regs *regs,
+void skip_singlestep(struct kprobe *p, struct pt_regs *regs,
 		      struct kprobe_ctlblk *kcb, unsigned long orig_ip)
 {
 	/*
@@ -43,18 +43,6 @@ void __skip_singlestep(struct kprobe *p, struct pt_regs *regs,
 		regs->ip = orig_ip;
 }
 
-int skip_singlestep(struct kprobe *p, struct pt_regs *regs,
-		    struct kprobe_ctlblk *kcb)
-{
-	if (kprobe_ftrace(p)) {
-		__skip_singlestep(p, regs, kcb, 0);
-		preempt_enable_no_resched();
-		return 1;
-	}
-	return 0;
-}
-NOKPROBE_SYMBOL(skip_singlestep);
-
 /* Ftrace callback handler for kprobes -- called under preepmt disabed */
 void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
 			   struct ftrace_ops *ops, struct pt_regs *regs)
@@ -80,7 +68,7 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
 		__this_cpu_write(current_kprobe, p);
 		kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 		if (!p->pre_handler || !p->pre_handler(p, regs)) {
-			__skip_singlestep(p, regs, kcb, orig_ip);
+			skip_singlestep(p, regs, kcb, orig_ip);
 			preempt_enable_no_resched();
 		}
 		/*

[RFC PATCH -tip 6/9] kprobes: Remove break_handler from struct kprobe

[Masami Hiramatsu]

Since we already removed all break_handler references,
we can remove break_handler safely.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 include/linux/kprobes.h |    7 -------
 1 file changed, 7 deletions(-)

diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index f7a6c398b4bf..c15989cd4675 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -63,7 +63,6 @@ struct pt_regs;
 struct kretprobe;
 struct kretprobe_instance;
 typedef int (*kprobe_pre_handler_t) (struct kprobe *, struct pt_regs *);
-typedef int (*kprobe_break_handler_t) (struct kprobe *, struct pt_regs *);
 typedef void (*kprobe_post_handler_t) (struct kprobe *, struct pt_regs *,
 				       unsigned long flags);
 typedef int (*kprobe_fault_handler_t) (struct kprobe *, struct pt_regs *,
@@ -101,12 +100,6 @@ struct kprobe {
 	 */
 	kprobe_fault_handler_t fault_handler;
 
-	/*
-	 * ... called if breakpoint trap occurs in probe handler.
-	 * Return 1 if it handled break, otherwise kernel will see it.
-	 */
-	kprobe_break_handler_t break_handler;
-
 	/* Saved opcode (which has been replaced with breakpoint) */
 	kprobe_opcode_t opcode;
 

[RFC PATCH -tip 7/9] x86: kprobes: Do not disable preempt on int3 path

[Masami Hiramatsu]

Since int3 and debug exception(for singlestep) are run with
IRQ disabled and while running single stepping we drop IF
from regs->flags, that path must not be preemptible. So we
can remove the preempt disable/enable calls from that path.

Note that, this changes the behavior of execution path override
which is done by modifying regs->ip in pre_handler().
Previously it requires reset_current_kprobe(), enable preempt
and return !0.
With this change, preempt count is not changed on int3 path, so
user no need to enable preempt. To fit this behavior, this
modifies ftrace-based kprobe too. In total, pre_handler() does
not need to recover preempt count even if it changes regs->ip.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Suggested-by: Ingo Molnar <mingo@kernel.org>
---
 Documentation/kprobes.txt        |   11 +++++------
 arch/x86/kernel/kprobes/core.c   |   14 +++-----------
 arch/x86/kernel/kprobes/ftrace.c |    5 ++---
 arch/x86/kernel/kprobes/opt.c    |    1 -
 4 files changed, 10 insertions(+), 21 deletions(-)

diff --git a/Documentation/kprobes.txt b/Documentation/kprobes.txt
index 94df43224c6c..679cba3380e4 100644
--- a/Documentation/kprobes.txt
+++ b/Documentation/kprobes.txt
@@ -566,12 +566,11 @@ the same handler) may run concurrently on different CPUs.
 Kprobes does not use mutexes or allocate memory except during
 registration and unregistration.
 
-Probe handlers are run with preemption disabled.  Depending on the
-architecture and optimization state, handlers may also run with
-interrupts disabled (e.g., kretprobe handlers and optimized kprobe
-handlers run without interrupt disabled on x86/x86-64).  In any case,
-your handler should not yield the CPU (e.g., by attempting to acquire
-a semaphore).
+Probe handlers are run with preemption disabled or interrupt disabled,
+which depends on the architecture and optimization state.  (e.g.,
+kretprobe handlers and optimized kprobe handlers run without interrupt
+disabled on x86/x86-64).  In any case, your handler should not yield
+the CPU (e.g., by attempting to acquire a semaphore, or waiting I/O).
 
 Since a return probe is implemented by replacing the return
 address with the trampoline's address, stack backtraces and calls
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 7663f23aa860..b771a01d51f4 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -592,7 +592,6 @@ static void setup_singlestep(struct kprobe *p, struct pt_regs *regs,
 		 * stepping.
 		 */
 		regs->ip = (unsigned long)p->ainsn.insn;
-		preempt_enable_no_resched();
 		return;
 	}
 #endif
@@ -665,12 +664,10 @@ int kprobe_int3_handler(struct pt_regs *regs)
 
 	addr = (kprobe_opcode_t *)(regs->ip - sizeof(kprobe_opcode_t));
 	/*
-	 * We don't want to be preempted for the entire
-	 * duration of kprobe processing. We conditionally
-	 * re-enable preemption at the end of this function,
-	 * and also in reenter_kprobe() and setup_singlestep().
+	 * We don't want to be preempted for the entire duration of kprobe
+	 * processing. Since int3 and debug trap disables irqs and we clear
+	 * IF while singlestepping, it must be no preemptible.
 	 */
-	preempt_disable();
 
 	kcb = get_kprobe_ctlblk();
 	p = get_kprobe(addr);
@@ -704,11 +701,9 @@ int kprobe_int3_handler(struct pt_regs *regs)
 		 * the original instruction.
 		 */
 		regs->ip = (unsigned long)addr;
-		preempt_enable_no_resched();
 		return 1;
 	} /* else: not a kprobe fault; let the kernel handle it */
 
-	preempt_enable_no_resched();
 	return 0;
 }
 NOKPROBE_SYMBOL(kprobe_int3_handler);
@@ -959,8 +954,6 @@ int kprobe_debug_handler(struct pt_regs *regs)
 	}
 	reset_current_kprobe();
 out:
-	preempt_enable_no_resched();
-
 	/*
 	 * if somebody else is singlestepping across a probe point, flags
 	 * will have TF set, in which case, continue the remaining processing
@@ -1007,7 +1000,6 @@ int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 			restore_previous_kprobe(kcb);
 		else
 			reset_current_kprobe();
-		preempt_enable_no_resched();
 	} else if (kcb->kprobe_status == KPROBE_HIT_ACTIVE ||
 		   kcb->kprobe_status == KPROBE_HIT_SSDONE) {
 		/*
diff --git a/arch/x86/kernel/kprobes/ftrace.c b/arch/x86/kernel/kprobes/ftrace.c
index c8696f2a583f..f1ac65d6b352 100644
--- a/arch/x86/kernel/kprobes/ftrace.c
+++ b/arch/x86/kernel/kprobes/ftrace.c
@@ -67,10 +67,9 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
 		preempt_disable();
 		__this_cpu_write(current_kprobe, p);
 		kcb->kprobe_status = KPROBE_HIT_ACTIVE;
-		if (!p->pre_handler || !p->pre_handler(p, regs)) {
+		if (!p->pre_handler || !p->pre_handler(p, regs))
 			skip_singlestep(p, regs, kcb, orig_ip);
-			preempt_enable_no_resched();
-		}
+		preempt_enable_no_resched();
 		/*
 		 * If pre_handler returns !0, it sets regs->ip and
 		 * resets current kprobe, and keep preempt count +1.
diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c
index 203d398802a3..eaf02f2e7300 100644
--- a/arch/x86/kernel/kprobes/opt.c
+++ b/arch/x86/kernel/kprobes/opt.c
@@ -491,7 +491,6 @@ int setup_detour_execution(struct kprobe *p, struct pt_regs *regs, int reenter)
 		regs->ip = (unsigned long)op->optinsn.insn + TMPL_END_IDX;
 		if (!reenter)
 			reset_current_kprobe();
-		preempt_enable_no_resched();
 		return 1;
 	}
 	return 0;

[RFC PATCH -tip 8/9] error-injection: Fix to not enabling preemption in pre_handler

[Masami Hiramatsu]

Since kprobes pre_handler doesn't need to recover preemption
even if it modifies regs->ip anymore, this fixes to remove
the preempt_enable_no_resched() from pre_handler.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 kernel/fail_function.c |    1 -
 1 file changed, 1 deletion(-)

diff --git a/kernel/fail_function.c b/kernel/fail_function.c
index 21b0122cb39c..b1713521f096 100644
--- a/kernel/fail_function.c
+++ b/kernel/fail_function.c
@@ -176,7 +176,6 @@ static int fei_kprobe_handler(struct kprobe *kp, struct pt_regs *regs)
 		override_function_with_return(regs);
 		/* Kprobe specific fixup */
 		reset_current_kprobe();
-		preempt_enable_no_resched();
 		return 1;
 	}
 

Re: [RFC PATCH -tip 8/9] error-injection: Fix to not enabling preemption in pre_handler

[Ingo Molnar]

* Masami Hiramatsu <mhiramat@kernel.org> wrote:

> Since kprobes pre_handler doesn't need to recover preemption
> even if it modifies regs->ip anymore, this fixes to remove
> the preempt_enable_no_resched() from pre_handler.
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> ---
>  kernel/fail_function.c |    1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/kernel/fail_function.c b/kernel/fail_function.c
> index 21b0122cb39c..b1713521f096 100644
> --- a/kernel/fail_function.c
> +++ b/kernel/fail_function.c
> @@ -176,7 +176,6 @@ static int fei_kprobe_handler(struct kprobe *kp, struct pt_regs *regs)
>  		override_function_with_return(regs);
>  		/* Kprobe specific fixup */
>  		reset_current_kprobe();
> -		preempt_enable_no_resched();
>  		return 1;
>  	}

So where did the matching preempt_disable() get removed? If it's the 6/9 patch, 
then this patch (and 8/9) should very much be part of it.

There should be no bisection breakage in the series.

Thanks,

	Ingo

Re: [RFC PATCH -tip 8/9] error-injection: Fix to not enabling preemption in pre_handler

[Masami Hiramatsu]

On Sat, 10 Mar 2018 09:22:48 +0100
Ingo Molnar <mingo@kernel.org> wrote:

> 
> * Masami Hiramatsu <mhiramat@kernel.org> wrote:
> 
> > Since kprobes pre_handler doesn't need to recover preemption
> > even if it modifies regs->ip anymore, this fixes to remove
> > the preempt_enable_no_resched() from pre_handler.
> > 
> > Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> > ---
> >  kernel/fail_function.c |    1 -
> >  1 file changed, 1 deletion(-)
> > 
> > diff --git a/kernel/fail_function.c b/kernel/fail_function.c
> > index 21b0122cb39c..b1713521f096 100644
> > --- a/kernel/fail_function.c
> > +++ b/kernel/fail_function.c
> > @@ -176,7 +176,6 @@ static int fei_kprobe_handler(struct kprobe *kp, struct pt_regs *regs)
> >  		override_function_with_return(regs);
> >  		/* Kprobe specific fixup */
> >  		reset_current_kprobe();
> > -		preempt_enable_no_resched();
> >  		return 1;
> >  	}
> 
> So where did the matching preempt_disable() get removed? If it's the 6/9 patch, 
> then this patch (and 8/9) should very much be part of it.

It is 7/9, in kprobe_int3_handler() and kprobe_ftrace_handler().
The latter is a bit tricky, originally it enable preemption only when
the pre_handler returns 0, but 7/9 changes it always enables preemption.

> 
> There should be no bisection breakage in the series.

OK, I will merge 7/9-9/9 (anyway those are currently only support x86).

Thanks,

> 
> Thanks,
> 
> 	Ingo


-- 
Masami Hiramatsu <mhiramat@kernel.org>

[RFC PATCH -tip 9/9] tracing: kprobes: Fix to not enabling preemption

[Masami Hiramatsu]

Since kprobes pre_handler doesn't need to recover preemption
even if it modifies regs->ip anymore, this fixes to remove
the preempt_enable_no_resched() from pre_handler.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 kernel/trace/trace_kprobe.c |    3 ---
 1 file changed, 3 deletions(-)

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 5ce9b8cf7be3..6c894e2be8d6 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -1221,12 +1221,9 @@ kprobe_perf_func(struct trace_kprobe *tk, struct pt_regs *regs)
 		 * We need to check and see if we modified the pc of the
 		 * pt_regs, and if so clear the kprobe and return 1 so that we
 		 * don't do the single stepping.
-		 * The ftrace kprobe handler leaves it up to us to re-enable
-		 * preemption here before returning if we've modified the ip.
 		 */
 		if (orig_ip != instruction_pointer(regs)) {
 			reset_current_kprobe();
-			preempt_enable_no_resched();
 			return 1;
 		}
 		if (!ret)

Re: [RFC PATCH -tip 0/9] kprobes: Cleanup jprobe implementation

[Steven Rostedt]

On Fri,  9 Mar 2018 21:35:17 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:

> Hello,
> 
> Since we decided to remove jprobe from kernel last year,
> its APIs are disabled and we worked on moving in-kernel
> jprobe users to kprobes or trace-events. And now no jprobe
> users are here anymore.
> 
> I think it is good time to get rid of jprobe implementation
> from the kernel. However, I need other arch developers help
> to complete it, since jprobe is implemented multi arch wide.
> I can remove those code, but can not test all of those.
> 
> Here is the series of patches to show how to do that.
> I tried to remove it from x86 tree. Basically we need to
> do 3 things;
> 
>  - Remove jprobe functions (register/unregister,
>    setjump/longjump) from generic/arch-dependent code.
>    [1/9][2/9][3/9]
>  - Remove break_handler related code.
>    [4/9][5/9][6/9]
>  - Do not disable preemption on exception handler
>    [7/9][8/9][9/9]
> 
> The [3/9] and [6/9] are destractive changes except for x86
> (means causes build errors) since those arch still have some
> references of those functions. So we need to write patches
> similar to [2/9] and [5/9] for each arch before applying those.
> In this series I sorted it as this order just for review,
> [3/9] and [6/9] should be applied after all archs have
> been fixed.
> 
> Also, [7/9] is a kind of destractive, which changes required
> behavior for the pre_handlers which changes regs->ip.
> So we also need a patch similar to [7/9] for each arch too.
> Fortunately, current in-tree such user is very limited, both
> works only on x86. So it is not hurry, but we need to change
> arch dependent code.
>

Hi Masami,

thanks for doing all this. I do want to review this and your other
patch set. I've just been traveling a lot. I came home from California
yesterday and will be leaving Sunday to Portland for ELC. Will you be
there?

-- Steve

Re: [RFC PATCH -tip 0/9] kprobes: Cleanup jprobe implementation

[Masami Hiramatsu]

On Fri, 9 Mar 2018 18:54:02 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Fri,  9 Mar 2018 21:35:17 +0900
> Masami Hiramatsu <mhiramat@kernel.org> wrote:
> 
> > Hello,
> > 
> > Since we decided to remove jprobe from kernel last year,
> > its APIs are disabled and we worked on moving in-kernel
> > jprobe users to kprobes or trace-events. And now no jprobe
> > users are here anymore.
> > 
> > I think it is good time to get rid of jprobe implementation
> > from the kernel. However, I need other arch developers help
> > to complete it, since jprobe is implemented multi arch wide.
> > I can remove those code, but can not test all of those.
> > 
> > Here is the series of patches to show how to do that.
> > I tried to remove it from x86 tree. Basically we need to
> > do 3 things;
> > 
> >  - Remove jprobe functions (register/unregister,
> >    setjump/longjump) from generic/arch-dependent code.
> >    [1/9][2/9][3/9]
> >  - Remove break_handler related code.
> >    [4/9][5/9][6/9]
> >  - Do not disable preemption on exception handler
> >    [7/9][8/9][9/9]
> > 
> > The [3/9] and [6/9] are destractive changes except for x86
> > (means causes build errors) since those arch still have some
> > references of those functions. So we need to write patches
> > similar to [2/9] and [5/9] for each arch before applying those.
> > In this series I sorted it as this order just for review,
> > [3/9] and [6/9] should be applied after all archs have
> > been fixed.
> > 
> > Also, [7/9] is a kind of destractive, which changes required
> > behavior for the pre_handlers which changes regs->ip.
> > So we also need a patch similar to [7/9] for each arch too.
> > Fortunately, current in-tree such user is very limited, both
> > works only on x86. So it is not hurry, but we need to change
> > arch dependent code.
> >
> 
> Hi Masami,
> 
> thanks for doing all this. I do want to review this and your other
> patch set.

Thanks!

> I've just been traveling a lot. I came home from California
> yesterday and will be leaving Sunday to Portland for ELC. Will you be
> there?

Oh, no, sorry I'll not be there. Anyway, I will wait for your review. :)

> 
> -- Steve


-- 
Masami Hiramatsu <mhiramat@kernel.org>

Re: [RFC PATCH -tip 0/9] kprobes: Cleanup jprobe implementation

[Ingo Molnar]

* Masami Hiramatsu <mhiramat@kernel.org> wrote:

> Hello,
> 
> Since we decided to remove jprobe from kernel last year,
> its APIs are disabled and we worked on moving in-kernel
> jprobe users to kprobes or trace-events. And now no jprobe
> users are here anymore.
> 
> I think it is good time to get rid of jprobe implementation
> from the kernel. However, I need other arch developers help
> to complete it, since jprobe is implemented multi arch wide.
> I can remove those code, but can not test all of those.
> 
> Here is the series of patches to show how to do that.
> I tried to remove it from x86 tree. Basically we need to
> do 3 things;
> 
>  - Remove jprobe functions (register/unregister,
>    setjump/longjump) from generic/arch-dependent code.
>    [1/9][2/9][3/9]
>  - Remove break_handler related code.
>    [4/9][5/9][6/9]
>  - Do not disable preemption on exception handler
>    [7/9][8/9][9/9]
> 
> The [3/9] and [6/9] are destractive changes except for x86
> (means causes build errors) since those arch still have some
> references of those functions. So we need to write patches
> similar to [2/9] and [5/9] for each arch before applying those.
> In this series I sorted it as this order just for review,
> [3/9] and [6/9] should be applied after all archs have
> been fixed.
> 
> Also, [7/9] is a kind of destractive, which changes required
> behavior for the pre_handlers which changes regs->ip.
> So we also need a patch similar to [7/9] for each arch too.
> Fortunately, current in-tree such user is very limited, both
> works only on x86. So it is not hurry, but we need to change
> arch dependent code.
>
> Thank you,
> 
> ---
> 
> Masami Hiramatsu (9):
>       kprobes: Remove jprobe API implementation
>       x86: kprobes: Remove jprobe implementation
>       kprobes: Remove jprobe data structure and interfaces
>       kprobes: Ignore break_handler
>       x86: kprobes: Ignore break_handler
>       kprobes: Remove break_handler from struct kprobe
>       x86: kprobes: Do not disable preempt on int3 path
>       error-injection: Fix to not enabling preemption in pre_handler
>       tracing: kprobes: Fix to not enabling preemption
> 
> 
>  Documentation/kprobes.txt        |   13 ++--
>  arch/x86/include/asm/kprobes.h   |    3 -
>  arch/x86/kernel/kprobes/common.h |   10 ---
>  arch/x86/kernel/kprobes/core.c   |  114 ++------------------------------------
>  arch/x86/kernel/kprobes/ftrace.c |   21 +------
>  arch/x86/kernel/kprobes/opt.c    |    1 
>  include/linux/kprobes.h          |   54 ------------------
>  kernel/fail_function.c           |    1 
>  kernel/kprobes.c                 |  115 ++------------------------------------
>  kernel/trace/trace_kprobe.c      |    3 -
>  10 files changed, 20 insertions(+), 315 deletions(-)

Nice work, and I love the diffstat, but please do a series that works (builds and 
boots and has working kprobes) at every interim step.

Thanks,

	Ingo

Re: [RFC PATCH -tip 0/9] kprobes: Cleanup jprobe implementation

[Masami Hiramatsu]

On Sat, 10 Mar 2018 09:24:44 +0100
Ingo Molnar <mingo@kernel.org> wrote:

> 
> * Masami Hiramatsu <mhiramat@kernel.org> wrote:
> 
> > Hello,
> > 
> > Since we decided to remove jprobe from kernel last year,
> > its APIs are disabled and we worked on moving in-kernel
> > jprobe users to kprobes or trace-events. And now no jprobe
> > users are here anymore.
> > 
> > I think it is good time to get rid of jprobe implementation
> > from the kernel. However, I need other arch developers help
> > to complete it, since jprobe is implemented multi arch wide.
> > I can remove those code, but can not test all of those.
> > 
> > Here is the series of patches to show how to do that.
> > I tried to remove it from x86 tree. Basically we need to
> > do 3 things;
> > 
> >  - Remove jprobe functions (register/unregister,
> >    setjump/longjump) from generic/arch-dependent code.
> >    [1/9][2/9][3/9]
> >  - Remove break_handler related code.
> >    [4/9][5/9][6/9]
> >  - Do not disable preemption on exception handler
> >    [7/9][8/9][9/9]
> > 
> > The [3/9] and [6/9] are destractive changes except for x86
> > (means causes build errors) since those arch still have some
> > references of those functions. So we need to write patches
> > similar to [2/9] and [5/9] for each arch before applying those.
> > In this series I sorted it as this order just for review,
> > [3/9] and [6/9] should be applied after all archs have
> > been fixed.
> > 
> > Also, [7/9] is a kind of destractive, which changes required
> > behavior for the pre_handlers which changes regs->ip.
> > So we also need a patch similar to [7/9] for each arch too.
> > Fortunately, current in-tree such user is very limited, both
> > works only on x86. So it is not hurry, but we need to change
> > arch dependent code.
> >
> > Thank you,
> > 
> > ---
> > 
> > Masami Hiramatsu (9):
> >       kprobes: Remove jprobe API implementation
> >       x86: kprobes: Remove jprobe implementation
> >       kprobes: Remove jprobe data structure and interfaces
> >       kprobes: Ignore break_handler
> >       x86: kprobes: Ignore break_handler
> >       kprobes: Remove break_handler from struct kprobe
> >       x86: kprobes: Do not disable preempt on int3 path
> >       error-injection: Fix to not enabling preemption in pre_handler
> >       tracing: kprobes: Fix to not enabling preemption
> > 
> > 
> >  Documentation/kprobes.txt        |   13 ++--
> >  arch/x86/include/asm/kprobes.h   |    3 -
> >  arch/x86/kernel/kprobes/common.h |   10 ---
> >  arch/x86/kernel/kprobes/core.c   |  114 ++------------------------------------
> >  arch/x86/kernel/kprobes/ftrace.c |   21 +------
> >  arch/x86/kernel/kprobes/opt.c    |    1 
> >  include/linux/kprobes.h          |   54 ------------------
> >  kernel/fail_function.c           |    1 
> >  kernel/kprobes.c                 |  115 ++------------------------------------
> >  kernel/trace/trace_kprobe.c      |    3 -
> >  10 files changed, 20 insertions(+), 315 deletions(-)
> 
> Nice work, and I love the diffstat, but please do a series that works (builds and 
> boots and has working kprobes) at every interim step.

Thank you! Yes, I'm thinking just keep header files no change (no removing
API and structure) until all archs apply C file changes in next version,
so that we can avoid any build error/test error.

Thanks,



> 
> Thanks,
> 
> 	Ingo


-- 
Masami Hiramatsu <mhiramat@kernel.org>