73 lines
2.2 KiB
C
73 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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