Commit 02752bd9 authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Alexei Starovoitov
Browse files

powerpc: Add rethook support 



Add rethook powerpc64 implementation. Most of the code has been copied from
kretprobes on powerpc64.

Signed-off-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
Tested-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/164735288495.1084943.539630613772422267.stgit@devnote2
parent 83acdce6

arch/powerpc/Kconfig

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Original line number Diff line number Diff line
@@ -229,6 +229,7 @@ config PPC 
	select HAVE_PERF_EVENTS_NMI		if PPC64

	select HAVE_PERF_REGS

	select HAVE_PERF_USER_STACK_DUMP

	select HAVE_RETHOOK			if KPROBES

	select HAVE_REGS_AND_STACK_ACCESS_API

	select HAVE_RELIABLE_STACKTRACE

	select HAVE_RSEQ

arch/powerpc/kernel/Makefile

+1 −0
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@@ -115,6 +115,7 @@ obj-$(CONFIG_SMP) += smp.o 
obj-$(CONFIG_KPROBES)		+= kprobes.o

obj-$(CONFIG_OPTPROBES)		+= optprobes.o optprobes_head.o

obj-$(CONFIG_KPROBES_ON_FTRACE)	+= kprobes-ftrace.o

obj-$(CONFIG_RETHOOK)		+= rethook.o

obj-$(CONFIG_UPROBES)		+= uprobes.o

obj-$(CONFIG_PPC_UDBG_16550)	+= legacy_serial.o udbg_16550.o

obj-$(CONFIG_SWIOTLB)		+= dma-swiotlb.o

arch/powerpc/kernel/rethook.c

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// SPDX-License-Identifier: GPL-2.0-only

/*

 * PowerPC implementation of rethook. This depends on kprobes.

 */



#include <linux/kprobes.h>

#include <linux/rethook.h>



/*

 * Function return trampoline:

 * 	- init_kprobes() establishes a probepoint here

 * 	- When the probed function returns, this probe

 * 		causes the handlers to fire

 */

asm(".global arch_rethook_trampoline\n"

	".type arch_rethook_trampoline, @function\n"

	"arch_rethook_trampoline:\n"

	"nop\n"

	"blr\n"

	".size arch_rethook_trampoline, .-arch_rethook_trampoline\n");



/*

 * Called when the probe at kretprobe trampoline is hit

 */

static int trampoline_rethook_handler(struct kprobe *p, struct pt_regs *regs)

{

	unsigned long orig_ret_address;



	orig_ret_address = rethook_trampoline_handler(regs, 0);

	/*

	 * We get here through one of two paths:

	 * 1. by taking a trap -> kprobe_handler() -> here

	 * 2. by optprobe branch -> optimized_callback() -> opt_pre_handler() -> here

	 *

	 * When going back through (1), we need regs->nip to be setup properly

	 * as it is used to determine the return address from the trap.

	 * For (2), since nip is not honoured with optprobes, we instead setup

	 * the link register properly so that the subsequent 'blr' in

	 * __kretprobe_trampoline jumps back to the right instruction.

	 *

	 * For nip, we should set the address to the previous instruction since

	 * we end up emulating it in kprobe_handler(), which increments the nip

	 * again.

	 */

	regs_set_return_ip(regs, orig_ret_address - 4);

	regs->link = orig_ret_address;



	return 0;

}

NOKPROBE_SYMBOL(trampoline_rethook_handler);



void arch_rethook_prepare(struct rethook_node *rh, struct pt_regs *regs, bool mcount)

{

	rh->ret_addr = regs->link;

	rh->frame = 0;



	/* Replace the return addr with trampoline addr */

	regs->link = (unsigned long)arch_rethook_trampoline;

}

NOKPROBE_SYMBOL(arch_prepare_kretprobe);



static struct kprobe trampoline_p = {

	.addr = (kprobe_opcode_t *) &arch_rethook_trampoline,

	.pre_handler = trampoline_rethook_handler

};



static int init_arch_rethook(void)

{

	return register_kprobe(&trampoline_p);

}



core_initcall(init_arch_rethook);