LinuxPPC-Dev Archive on lore.kernel.org
 help / color / Atom feed
* [PATCH 1/2] powerpc/kprobes: Remove redundant code
@ 2020-02-14 13:44 Christophe Leroy
  2020-02-14 13:44 ` [PATCH 2/2] powerpc/kprobes: Reduce depth of a test Christophe Leroy
  0 siblings, 1 reply; 2+ messages in thread
From: Christophe Leroy @ 2020-02-14 13:44 UTC (permalink / raw)
  To: Benjamin Herrenschmidt, Paul Mackerras, Michael Ellerman
  Cc: linuxppc-dev, linux-kernel

At the time being we have something like

	if (something) {
		p = get();
		if (p) {
			if (something_wrong)
				goto out;
			...
			return;
		} else if (a != b) {
			if (some_error)
				goto out;
			...
		}
		goto out;
	}
	p = get();
	if (!p) {
		if (a != b) {
			if (some_error)
				goto out;
			...
		}
		goto out;
	}

This is similar to

	p = get();
	if (something) {
		if (p) {
			if (something_wrong)
				goto out;
			...
			return;
		}
	}
	if (!p) {
		if (a != b) {
			if (some_error)
				goto out;
			...
		}
		goto out;
	}

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 arch/powerpc/kernel/kprobes.c | 15 +--------------
 1 file changed, 1 insertion(+), 14 deletions(-)

diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index f8b848aa65bd..7a925eb76ec0 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -276,8 +276,8 @@ int kprobe_handler(struct pt_regs *regs)
 	kcb = get_kprobe_ctlblk();
 
 	/* Check we're not actually recursing */
+	p = get_kprobe(addr);
 	if (kprobe_running()) {
-		p = get_kprobe(addr);
 		if (p) {
 			kprobe_opcode_t insn = *p->ainsn.insn;
 			if (kcb->kprobe_status == KPROBE_HIT_SS &&
@@ -308,22 +308,9 @@ int kprobe_handler(struct pt_regs *regs)
 			}
 			prepare_singlestep(p, regs);
 			return 1;
-		} else if (*addr != BREAKPOINT_INSTRUCTION) {
-			/* If trap variant, then it belongs not to us */
-			kprobe_opcode_t cur_insn = *addr;
-
-			if (is_trap(cur_insn))
-				goto no_kprobe;
-			/* The breakpoint instruction was removed by
-			 * another cpu right after we hit, no further
-			 * handling of this interrupt is appropriate
-			 */
-			ret = 1;
 		}
-		goto no_kprobe;
 	}
 
-	p = get_kprobe(addr);
 	if (!p) {
 		if (*addr != BREAKPOINT_INSTRUCTION) {
 			/*
-- 
2.25.0


^ permalink raw reply	[flat|nested] 2+ messages in thread

* [PATCH 2/2] powerpc/kprobes: Reduce depth of a test
  2020-02-14 13:44 [PATCH 1/2] powerpc/kprobes: Remove redundant code Christophe Leroy
@ 2020-02-14 13:44 ` Christophe Leroy
  0 siblings, 0 replies; 2+ messages in thread
From: Christophe Leroy @ 2020-02-14 13:44 UTC (permalink / raw)
  To: Benjamin Herrenschmidt, Paul Mackerras, Michael Ellerman
  Cc: linuxppc-dev, linux-kernel

	if (a) {
		if (b)
			do_something();
	}

Is equivalent to

	if (a & b)
		do_something();

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 arch/powerpc/kernel/kprobes.c | 58 +++++++++++++++++------------------
 1 file changed, 28 insertions(+), 30 deletions(-)

diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index 7a925eb76ec0..d7c80a078c1e 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -277,38 +277,36 @@ int kprobe_handler(struct pt_regs *regs)
 
 	/* Check we're not actually recursing */
 	p = get_kprobe(addr);
-	if (kprobe_running()) {
-		if (p) {
-			kprobe_opcode_t insn = *p->ainsn.insn;
-			if (kcb->kprobe_status == KPROBE_HIT_SS &&
-					is_trap(insn)) {
-				/* Turn off 'trace' bits */
-				regs->msr &= ~MSR_SINGLESTEP;
-				regs->msr |= kcb->kprobe_saved_msr;
-				goto no_kprobe;
-			}
-			/* We have reentered the kprobe_handler(), since
-			 * another probe was hit while within the handler.
-			 * We here save the original kprobes variables and
-			 * just single step on the instruction of the new probe
-			 * without calling any user handlers.
-			 */
-			save_previous_kprobe(kcb);
-			set_current_kprobe(p, regs, kcb);
-			kprobes_inc_nmissed_count(p);
-			kcb->kprobe_status = KPROBE_REENTER;
-			if (p->ainsn.boostable >= 0) {
-				ret = try_to_emulate(p, regs);
-
-				if (ret > 0) {
-					restore_previous_kprobe(kcb);
-					preempt_enable_no_resched();
-					return 1;
-				}
+	if (kprobe_running() && p) {
+		kprobe_opcode_t insn = *p->ainsn.insn;
+
+		if (kcb->kprobe_status == KPROBE_HIT_SS && is_trap(insn)) {
+			/* Turn off 'trace' bits */
+			regs->msr &= ~MSR_SINGLESTEP;
+			regs->msr |= kcb->kprobe_saved_msr;
+			goto no_kprobe;
+		}
+		/* We have reentered the kprobe_handler(), since
+		 * another probe was hit while within the handler.
+		 * We here save the original kprobes variables and
+		 * just single step on the instruction of the new probe
+		 * without calling any user handlers.
+		 */
+		save_previous_kprobe(kcb);
+		set_current_kprobe(p, regs, kcb);
+		kprobes_inc_nmissed_count(p);
+		kcb->kprobe_status = KPROBE_REENTER;
+		if (p->ainsn.boostable >= 0) {
+			ret = try_to_emulate(p, regs);
+
+			if (ret > 0) {
+				restore_previous_kprobe(kcb);
+				preempt_enable_no_resched();
+				return 1;
 			}
-			prepare_singlestep(p, regs);
-			return 1;
 		}
+		prepare_singlestep(p, regs);
+		return 1;
 	}
 
 	if (!p) {
-- 
2.25.0


^ permalink raw reply	[flat|nested] 2+ messages in thread

end of thread, back to index

Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-02-14 13:44 [PATCH 1/2] powerpc/kprobes: Remove redundant code Christophe Leroy
2020-02-14 13:44 ` [PATCH 2/2] powerpc/kprobes: Reduce depth of a test Christophe Leroy

LinuxPPC-Dev Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linuxppc-dev/0 linuxppc-dev/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linuxppc-dev linuxppc-dev/ https://lore.kernel.org/linuxppc-dev \
		linuxppc-dev@lists.ozlabs.org linuxppc-dev@ozlabs.org
	public-inbox-index linuxppc-dev

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.ozlabs.lists.linuxppc-dev


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git