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Commit fcfd708b authored by Sandeepa Prabhu's avatar Sandeepa Prabhu Committed by Catalin Marinas
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arm64: Add kernel return probes support (kretprobes) 



The pre-handler of this special 'trampoline' kprobe executes the return
probe handler functions and restores original return address in ELR_EL1.
This way the saved pt_regs still hold the original register context to be
carried back to the probed kernel function.

Signed-off-by: default avatarSandeepa Prabhu <sandeepa.s.prabhu@gmail.com>
Signed-off-by: default avatarDavid A. Long <dave.long@linaro.org>
Acked-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent da6a9125

arch/arm64/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -89,6 +89,7 @@ config ARM64 
	select HAVE_RCU_TABLE_FREE

	select HAVE_SYSCALL_TRACEPOINTS

	select HAVE_KPROBES

	select HAVE_KRETPROBES if HAVE_KPROBES

	select IOMMU_DMA if IOMMU_SUPPORT

	select IRQ_DOMAIN

	select IRQ_FORCED_THREADING

arch/arm64/kernel/probes/kprobes.c

+89 −1
Original line number Diff line number Diff line
@@ -578,7 +578,95 @@ bool arch_within_kprobe_blacklist(unsigned long addr) 


void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs)

{

	return NULL;

	struct kretprobe_instance *ri = NULL;

	struct hlist_head *head, empty_rp;

	struct hlist_node *tmp;

	unsigned long flags, orig_ret_address = 0;

	unsigned long trampoline_address =

		(unsigned long)&kretprobe_trampoline;

	kprobe_opcode_t *correct_ret_addr = NULL;



	INIT_HLIST_HEAD(&empty_rp);

	kretprobe_hash_lock(current, &head, &flags);



	/*

	 * It is possible to have multiple instances associated with a given

	 * task either because multiple functions in the call path have

	 * return probes installed on them, and/or more than one

	 * return probe was registered for a target function.

	 *

	 * We can handle this because:

	 *     - instances are always pushed into the head of the list

	 *     - when multiple return probes are registered for the same

	 *	 function, the (chronologically) first instance's ret_addr

	 *	 will be the real return address, and all the rest will

	 *	 point to kretprobe_trampoline.

	 */

	hlist_for_each_entry_safe(ri, tmp, head, hlist) {

		if (ri->task != current)

			/* another task is sharing our hash bucket */

			continue;



		orig_ret_address = (unsigned long)ri->ret_addr;



		if (orig_ret_address != trampoline_address)

			/*

			 * This is the real return address. Any other

			 * instances associated with this task are for

			 * other calls deeper on the call stack

			 */

			break;

	}



	kretprobe_assert(ri, orig_ret_address, trampoline_address);



	correct_ret_addr = ri->ret_addr;

	hlist_for_each_entry_safe(ri, tmp, head, hlist) {

		if (ri->task != current)

			/* another task is sharing our hash bucket */

			continue;



		orig_ret_address = (unsigned long)ri->ret_addr;

		if (ri->rp && ri->rp->handler) {

			__this_cpu_write(current_kprobe, &ri->rp->kp);

			get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;

			ri->ret_addr = correct_ret_addr;

			ri->rp->handler(ri, regs);

			__this_cpu_write(current_kprobe, NULL);

		}



		recycle_rp_inst(ri, &empty_rp);



		if (orig_ret_address != trampoline_address)

			/*

			 * This is the real return address. Any other

			 * instances associated with this task are for

			 * other calls deeper on the call stack

			 */

			break;

	}



	kretprobe_hash_unlock(current, &flags);



	hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {

		hlist_del(&ri->hlist);

		kfree(ri);

	}

	return (void *)orig_ret_address;

}



void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,

				      struct pt_regs *regs)

{

	ri->ret_addr = (kprobe_opcode_t *)regs->regs[30];



	/* replace return addr (x30) with trampoline */

	regs->regs[30] = (long)&kretprobe_trampoline;

}



int __kprobes arch_trampoline_kprobe(struct kprobe *p)

{

	return 0;

}



int __init arch_init_kprobes(void)