--- v3
+++ v4
@@ -1,73 +1,58 @@
-From: "Naveen N. Rao" <naveen.n.rao@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'.
-To permit the use of relative branch instruction in powerpc, the target
-address has to be relatively nearby, since the address is specified in an
-immediate field (24 bit filed) in the instruction opcode itself. Here
-nearby refers to 32MB on either side of the current instruction.
+Signed-off-by: Anju T Sudhakar <anju@linux.vnet.ibm.com>
+Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
+---
+ arch/powerpc/kernel/kprobes.c | 8 ++++++++
+ arch/powerpc/kernel/optprobes.c | 7 +++----
+ 2 files changed, 11 insertions(+), 4 deletions(-)
-This patch verifies whether the target address is within +/- 32MB
-range or not.
-
-Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
-Signed-off-by: Anju T Sudhakar <anju@linux.vnet.ibm.com>
----
- arch/powerpc/include/asm/code-patching.h | 1 +
- arch/powerpc/lib/code-patching.c | 24 +++++++++++++++++++++++-
- 2 files changed, 24 insertions(+), 1 deletion(-)
-
-diff --git a/arch/powerpc/include/asm/code-patching.h b/arch/powerpc/include/asm/code-patching.h
-index 2015b07..75ee4f4 100644
---- a/arch/powerpc/include/asm/code-patching.h
-+++ b/arch/powerpc/include/asm/code-patching.h
-@@ -22,6 +22,7 @@
- #define BRANCH_SET_LINK 0x1
- #define BRANCH_ABSOLUTE 0x2
+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");
-+bool is_offset_in_branch_range(long offset);
- unsigned int create_branch(const unsigned int *addr,
- unsigned long target, int flags);
- unsigned int create_cond_branch(const unsigned int *addr,
-diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
-index d5edbeb..f643451 100644
---- a/arch/powerpc/lib/code-patching.c
-+++ b/arch/powerpc/lib/code-patching.c
-@@ -32,6 +32,28 @@ int patch_branch(unsigned int *addr, unsigned long target, int flags)
- return patch_instruction(addr, create_branch(addr, target, flags));
- }
+ /*
+@@ -334,6 +335,13 @@ static int __kprobes trampoline_probe_handler(struct kprobe *p,
-+bool is_offset_in_branch_range(long offset)
-+{
+ kretprobe_assert(ri, orig_ret_address, trampoline_address);
+ regs->nip = orig_ret_address;
+ /*
-+ * Powerpc branch instruction is :
-+ *
-+ * 0 6 30 31
-+ * +---------+----------------+---+---+
-+ * | opcode | LI |AA |LK |
-+ * +---------+----------------+---+---+
-+ * Where AA = 0 and LK = 0
-+ *
-+ * LI is a signed 24 bits integer. The real branch offset is computed
-+ * by: imm32 = SignExtend(LI:'0b00', 32);
-+ *
-+ * So the maximum forward branch should be:
-+ * (0x007fffff << 2) = 0x01fffffc = 0x1fffffc
-+ * The maximum backward branch should be:
-+ * (0xff800000 << 2) = 0xfe000000 = -0x2000000
++ * 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.
+ */
-+ return (offset >= -0x2000000 && offset <= 0x1fffffc && !(offset & 0x3));
-+}
-+
- unsigned int create_branch(const unsigned int *addr,
- unsigned long target, int flags)
- {
-@@ -43,7 +65,7 @@ unsigned int create_branch(const unsigned int *addr,
- offset = offset - (unsigned long)addr;
++ regs->link = orig_ret_address;
- /* Check we can represent the target in the instruction format */
-- if (offset < -0x2000000 || offset > 0x1fffffc || offset & 0x3)
-+ if (!is_offset_in_branch_range(offset))
- return 0;
+ 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)
- /* Mask out the flags and target, so they don't step on each other. */
+ /*
+ * 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