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powerpc: Add rethook support

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

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Tested-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/164735288495.1084943.539630613772422267.stgit@devnote2
This commit is contained in:
Masami Hiramatsu 2022-03-15 23:01:25 +09:00 committed by Alexei Starovoitov
parent 83acdce689
commit 02752bd99d
3 changed files with 74 additions and 0 deletions
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1
arch/powerpc/Kconfig
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@ -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

1
arch/powerpc/kernel/Makefile
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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

72
arch/powerpc/kernel/rethook.c Normal file
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@ -0,0 +1,72 @@
// 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);