linux-kernel - [RFC PATCH 07/14] ia64: kprobes: Use generic kretprobe trampoline handler

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Message-Id: <159844964317.510284.8941010491714059097.stgit@devnote2>
Date:   Wed, 26 Aug 2020 22:47:23 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Eddy Wu <Eddy_Wu@...ndmicro.com>, linux-kernel@...r.kernel.org,
        x86@...nel.org, "David S . Miller" <davem@...emloft.net>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        "Naveen N . Rao" <naveen.n.rao@...ux.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        linux-arch@...r.kernel.org
Subject: [RFC PATCH 07/14] ia64: kprobes: Use generic kretprobe trampoline handler

Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
---
 arch/ia64/kernel/kprobes.c |   79 ++------------------------------------------
 1 file changed, 4 insertions(+), 75 deletions(-)

diff --git a/arch/ia64/kernel/kprobes.c b/arch/ia64/kernel/kprobes.c
index 7a7df944d798..0e725ca9c60d 100644
--- a/arch/ia64/kernel/kprobes.c
+++ b/arch/ia64/kernel/kprobes.c
@@ -396,83 +396,11 @@ static void kretprobe_trampoline(void)
 {
 }
 
-/*
- * At this point the target function has been tricked into
- * returning into our trampoline.  Lookup the associated instance
- * and then:
- *    - call the handler function
- *    - cleanup by marking the instance as unused
- *    - long jump back to the original return address
- */
 int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 {
-	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 =
-		((struct fnptr *)kretprobe_trampoline)->ip;
-
-	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 an multiple functions in the call path
-	 * have a return probe installed on them, and/or more than one return
-	 * return probe was registered for a target function.
-	 *
-	 * We can handle this because:
-	 *     - instances are always inserted at the head of the list
-	 *     - when multiple return probes are registered for the same
-	 *       function, the first instance's ret_addr will point to 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;
-	}
-
-	regs->cr_iip = orig_ret_address;
-
-	hlist_for_each_entry_safe(ri, tmp, head, hlist) {
-		if (ri->task != current)
-			/* another task is sharing our hash bucket */
-			continue;
-
-		if (ri->rp && ri->rp->handler)
-			ri->rp->handler(ri, regs);
-
-		orig_ret_address = (unsigned long)ri->ret_addr;
-		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_assert(ri, orig_ret_address, trampoline_address);
-
-	kretprobe_hash_unlock(current, &flags);
-
-	hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
-		hlist_del(&ri->hlist);
-		kfree(ri);
-	}
+	regs->cr_iip = __kretprobe_trampoline_handler(regs,
+				(unsigned long)kretprobe_trampoline,
+				NULL);
 	/*
 	 * By returning a non-zero value, we are telling
 	 * kprobe_handler() that we don't want the post_handler
@@ -485,6 +413,7 @@ void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 				      struct pt_regs *regs)
 {
 	ri->ret_addr = (kprobe_opcode_t *)regs->b0;
+	ri->fp = NULL;
 
 	/* Replace the return addr with trampoline addr */
 	regs->b0 = ((struct fnptr *)kretprobe_trampoline)->ip;