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Commit 762df10b authored by Anju T's avatar Anju T Committed by Michael Ellerman
Browse files

powerpc/kprobes: Optimize kprobe in kretprobe_trampoline() 



Kprobe placed on the  kretprobe_trampoline() during boot time can be
optimized, since the instruction at probe point is a 'nop'.

Signed-off-by: default avatarAnju T Sudhakar <anju@linux.vnet.ibm.com>
Acked-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 51c9c084

arch/powerpc/kernel/kprobes.c

+8 −0
Original line number Diff line number Diff line
@@ -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);

arch/powerpc/kernel/optprobes.c

+3 −4
Original line number Diff line number Diff line
@@ -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