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19f1bc3fb5
This is an adaptation of commit f3a112c0c40d ("x86,rethook,kprobes:
Replace kretprobe with rethook on x86") to powerpc.
Rethook follows the existing kretprobe implementation, but separates
it from kprobes so that it can be used by fprobe (ftrace-based
function entry/exit probes). As such, this patch also enables fprobe
to work on powerpc. The only other change compared to the existing
kretprobe implementation is doing the return address fixup in
arch_rethook_fixup_return().
Reference to other archs:
commit b57c2f124098 ("riscv: add riscv rethook implementation")
commit 7b0a096436c2 ("LoongArch: Replace kretprobe with rethook")
Note:
=====
In future, rethook will be only for kretprobe, and kretprobe
will be replaced by fprobe.
https://lore.kernel.org/all/172000134410.63468.13742222887213469474.stgit@devnote2/
We will adapt the above implementation for powerpc once its upstream.
Until then, we can have this implementation of rethook to serve
current kretprobe usecases.
Reviewed-by: Naveen Rao <naveen@kernel.org>
Signed-off-by: Abhishek Dubey <adubey@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240830113131.7597-1-adubey@linux.ibm.com
74 lines
2.2 KiB
C
74 lines
2.2 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* PowerPC implementation of rethook. This depends on kprobes.
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*/
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#include <linux/kprobes.h>
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#include <linux/rethook.h>
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/*
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* Function return trampoline:
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* - init_kprobes() establishes a probepoint here
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* - When the probed function returns, this probe
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* causes the handlers to fire
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*/
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asm(".global arch_rethook_trampoline\n"
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".type arch_rethook_trampoline, @function\n"
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"arch_rethook_trampoline:\n"
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"nop\n"
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"blr\n"
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".size arch_rethook_trampoline, .-arch_rethook_trampoline\n");
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/*
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* Called when the probe at kretprobe trampoline is hit
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*/
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static int trampoline_rethook_handler(struct kprobe *p, struct pt_regs *regs)
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{
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return !rethook_trampoline_handler(regs, regs->gpr[1]);
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}
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NOKPROBE_SYMBOL(trampoline_rethook_handler);
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void arch_rethook_prepare(struct rethook_node *rh, struct pt_regs *regs, bool mcount)
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{
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rh->ret_addr = regs->link;
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rh->frame = regs->gpr[1];
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/* Replace the return addr with trampoline addr */
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regs->link = (unsigned long)arch_rethook_trampoline;
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}
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NOKPROBE_SYMBOL(arch_rethook_prepare);
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/* This is called from rethook_trampoline_handler(). */
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void arch_rethook_fixup_return(struct pt_regs *regs, unsigned long orig_ret_address)
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{
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/*
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* We get here through one of two paths:
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* 1. by taking a trap -> kprobe_handler() -> here
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* 2. by optprobe branch -> optimized_callback() -> opt_pre_handler() -> here
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*
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* When going back through (1), we need regs->nip to be setup properly
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* as it is used to determine the return address from the trap.
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* For (2), since nip is not honoured with optprobes, we instead setup
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* the link register properly so that the subsequent 'blr' in
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* arch_rethook_trampoline jumps back to the right instruction.
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*
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* For nip, we should set the address to the previous instruction since
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* we end up emulating it in kprobe_handler(), which increments the nip
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* again.
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*/
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regs_set_return_ip(regs, orig_ret_address - 4);
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regs->link = orig_ret_address;
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}
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NOKPROBE_SYMBOL(arch_rethook_fixup_return);
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static struct kprobe trampoline_p = {
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.addr = (kprobe_opcode_t *) &arch_rethook_trampoline,
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.pre_handler = trampoline_rethook_handler
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};
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/* rethook initializer */
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int __init arch_init_kprobes(void)
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{
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return register_kprobe(&trampoline_p);
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}
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