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powerpc/kprobes: Optimize kprobe in kretprobe_trampoline()

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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>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Anju T 2017-02-08 15:20:52 +05:30 committed by Michael Ellerman
parent 51c9c08439
commit 762df10bad
2 changed files with 11 additions and 4 deletions
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8
arch/powerpc/kernel/kprobes.c
View file

@ -285,6 +285,7 @@ asm(".global kretprobe_trampoline\n"
".type kretprobe_trampoline, @function\n"
"kretprobe_trampoline:\n"
"nop\n"
"blr\n"
".size kretprobe_trampoline, .-kretprobe_trampoline\n");
/*
@ -337,6 +338,13 @@ 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);

7
arch/powerpc/kernel/optprobes.c
View file

@ -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