| 1 | |
| 2 | |
| 3 | * PowerPC implementation of rethook. This depends on kprobes.
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| 4 |
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| 5 |
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| 6 | #include <linux/kprobes.h>
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| 7 | #include <linux/rethook.h>
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| 8 |
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| 9 | |
| 10 | * Function return trampoline:
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| 11 | * - init_kprobes() establishes a probepoint here
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| 12 | * - When the probed function returns, this probe
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| 13 | * causes the handlers to fire
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| 14 |
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| 15 | asm(".global arch_rethook_trampoline\n"
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| 16 | ".type arch_rethook_trampoline, @function\n"
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| 17 | "arch_rethook_trampoline:\n"
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| 18 | "nop\n"
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| 19 | "blr\n"
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| 20 | ".size arch_rethook_trampoline, .-arch_rethook_trampoline\n");
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| 21 |
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| 22 | |
| 23 | * Called when the probe at kretprobe trampoline is hit
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| 24 |
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| 25 | static int trampoline_rethook_handler(struct kprobe *p, struct pt_regs *regs)
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| 26 | {
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| 27 | return !rethook_trampoline_handler(regs, regs->gpr[1]);
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| 28 | }
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| 29 | NOKPROBE_SYMBOL(trampoline_rethook_handler);
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| 30 |
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| 31 | void arch_rethook_prepare(struct rethook_node *rh, struct pt_regs *regs, bool mcount)
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| 32 | {
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| 33 | rh->ret_addr = regs->link;
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| 34 | rh->frame = regs->gpr[1];
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| 35 |
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| 36 |
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| 37 | regs->link = (unsigned long)arch_rethook_trampoline;
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| 38 | }
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| 39 | NOKPROBE_SYMBOL(arch_rethook_prepare);
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| 40 |
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| 41 |
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| 42 | void arch_rethook_fixup_return(struct pt_regs *regs, unsigned long orig_ret_address)
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| 43 | {
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| 44 | |
| 45 | * We get here through one of two paths:
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| 46 | * 1. by taking a trap -> kprobe_handler() -> here
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| 47 | * 2. by optprobe branch -> optimized_callback() -> opt_pre_handler() -> here
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| 48 | *
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| 49 | * When going back through (1), we need regs->nip to be setup properly
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| 50 | * as it is used to determine the return address from the trap.
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| 51 | * For (2), since nip is not honoured with optprobes, we instead setup
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| 52 | * the link register properly so that the subsequent 'blr' in
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| 53 | * arch_rethook_trampoline jumps back to the right instruction.
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| 54 | *
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| 55 | * For nip, we should set the address to the previous instruction since
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| 56 | * we end up emulating it in kprobe_handler(), which increments the nip
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| 57 | * again.
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| 58 |
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| 59 | regs_set_return_ip(regs, orig_ret_address - 4);
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| 60 | regs->link = orig_ret_address;
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| 61 | }
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| 62 | NOKPROBE_SYMBOL(arch_rethook_fixup_return);
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| 63 |
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| 64 | static struct kprobe trampoline_p = {
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| 65 | .addr = (kprobe_opcode_t *) &arch_rethook_trampoline,
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| 66 | .pre_handler = trampoline_rethook_handler
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| 67 | };
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| 68 |
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| 69 |
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| 70 | int __init arch_init_kprobes(void)
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| 71 | {
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| 72 | return register_kprobe(&trampoline_p);
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| 73 | }
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