From: Anju T Sudhakar <anju@linux.vnet.ibm.com>
To: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Cc: ananth@in.ibm.com, naveen.n.rao@linux.vnet.ibm.com,
paulus@samba.org, srikar@linux.vnet.ibm.com,
benh@kernel.crashing.org, mpe@ellerman.id.au,
mahesh@linux.vnet.ibm.com, mhiramat@kernel.org,
anju@linux.vnet.ibm.com
Subject: [PATCH V2 4/4] arch/powerpc: Optimize kprobe in kretprobe_trampoline
Date: Wed, 14 Dec 2016 21:48:28 +0530 [thread overview]
Message-ID: <1481732310-7779-3-git-send-email-anju@linux.vnet.ibm.com> (raw)
In-Reply-To: <1481732310-7779-1-git-send-email-anju@linux.vnet.ibm.com>
Kprobe placed on the kretprobe_trampoline during boot time can be
optimized, since the instruction at probe point is a 'nop'.
Signed-off-by: Anju T Sudhakar <anju@linux.vnet.ibm.com>
---
arch/powerpc/kernel/kprobes.c | 8 ++++++++
arch/powerpc/kernel/optprobes.c | 7 +++----
2 files changed, 11 insertions(+), 4 deletions(-)
diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index e785cc9..5b0fd07 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -282,6 +282,7 @@ asm(".global kretprobe_trampoline\n"
".type kretprobe_trampoline, @function\n"
"kretprobe_trampoline:\n"
"nop\n"
+ "blr\n"
".size kretprobe_trampoline, .-kretprobe_trampoline\n");
/*
@@ -334,6 +335,13 @@ static int __kprobes trampoline_probe_handler(struct kprobe *p,
kretprobe_assert(ri, orig_ret_address, trampoline_address);
regs->nip = orig_ret_address;
+ /*
+ * Make LR point to the orig_ret_address.
+ * When the 'nop' inside the kretprobe_trampoline
+ * is optimized, we can do a 'blr' after executing the
+ * detour buffer code.
+ */
+ regs->link = orig_ret_address;
reset_current_kprobe();
kretprobe_hash_unlock(current, &flags);
diff --git a/arch/powerpc/kernel/optprobes.c b/arch/powerpc/kernel/optprobes.c
index ecba221..5e4c254 100644
--- a/arch/powerpc/kernel/optprobes.c
+++ b/arch/powerpc/kernel/optprobes.c
@@ -72,12 +72,11 @@ static unsigned long can_optimize(struct kprobe *p)
/*
* kprobe placed for kretprobe during boot time
- * is not optimizing now.
- *
- * TODO: Optimize kprobe in kretprobe_trampoline
+ * has a 'nop' instruction, which can be emulated.
+ * So further checks can be skipped.
*/
if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
- return 0;
+ return (unsigned long)p->addr + sizeof(kprobe_opcode_t);
/*
* We only support optimizing kernel addresses, but not
--
2.7.4
next prev parent reply other threads:[~2016-12-14 16:19 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-14 16:18 [PATCH V2 0/4] OPTPROBES for powerpc Anju T Sudhakar
2016-12-14 16:18 ` [PATCH V2 3/4] arch/powerpc: Implement Optprobes Anju T Sudhakar
2016-12-16 14:02 ` Masami Hiramatsu
2016-12-16 17:54 ` Anju T Sudhakar
2016-12-14 16:18 ` Anju T Sudhakar [this message]
2016-12-16 14:09 ` [PATCH V2 4/4] arch/powerpc: Optimize kprobe in kretprobe_trampoline Masami Hiramatsu
2016-12-14 16:18 ` [PATCH V2 1/4] powerpc: asm/ppc-opcode.h: introduce __PPC_SH64() Anju T Sudhakar
2016-12-14 16:18 ` [PATCH V2 2/4] powerpc: add helper to check if offset is within rel branch range Anju T Sudhakar
2016-12-16 11:52 ` Masami Hiramatsu
2016-12-16 16:31 ` Anju T Sudhakar
2016-12-16 14:46 ` [PATCH V2 0/4] OPTPROBES for powerpc Balbir Singh
2016-12-16 17:19 ` Naveen N. Rao
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