[PATCH 4.19.y 3/3] ia64: kprobes: Fix to pass correct trampoline address to the handler

[Masami Hiramatsu <mhiramat@kernel.org>]

commit a7fe2378454cf46cd5e2776d05e72bbe8f0a468c upstream.

The following commit:

   Commit e792ff804f49 ("ia64: kprobes: Use generic kretprobe trampoline handler")

Passed the wrong trampoline address to __kretprobe_trampoline_handler(): it
passes the descriptor address instead of function entry address.

Pass the right parameter.

Also use correct symbol dereference function to get the function address
from 'kretprobe_trampoline' - an IA64 special.

Link: https://lkml.kernel.org/r/163163042696.489837.12551102356265354730.stgit@devnote2

Fixes: e792ff804f49 ("ia64: kprobes: Use generic kretprobe trampoline handler")
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: X86 ML <x86@kernel.org>
Cc: Daniel Xu <dxu@dxuuu.xyz>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Abhishek Sagar <sagar.abhishek@gmail.com>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Paul McKenney <paulmck@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 arch/ia64/kernel/kprobes.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/ia64/kernel/kprobes.c b/arch/ia64/kernel/kprobes.c
index aa41bd5cf9b7..7fc0806bbdc9 100644
--- a/arch/ia64/kernel/kprobes.c
+++ b/arch/ia64/kernel/kprobes.c
@@ -424,7 +424,7 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 	struct hlist_node *tmp;
 	unsigned long flags, orig_ret_address = 0;
 	unsigned long trampoline_address =
-		((struct fnptr *)kretprobe_trampoline)->ip;
+		(unsigned long)dereference_function_descriptor(kretprobe_trampoline);
 
 	INIT_HLIST_HEAD(&empty_rp);
 	kretprobe_hash_lock(current, &head, &flags);
@@ -500,7 +500,7 @@ void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 	ri->ret_addr = (kprobe_opcode_t *)regs->b0;
 
 	/* Replace the return addr with trampoline addr */
-	regs->b0 = ((struct fnptr *)kretprobe_trampoline)->ip;
+	regs->b0 = (unsigned long)dereference_function_descriptor(kretprobe_trampoline);
 }
 
 /* Check the instruction in the slot is break */
@@ -1030,14 +1030,14 @@ static struct kprobe trampoline_p = {
 int __init arch_init_kprobes(void)
 {
 	trampoline_p.addr =
-		(kprobe_opcode_t *)((struct fnptr *)kretprobe_trampoline)->ip;
+		dereference_function_descriptor(kretprobe_trampoline);
 	return register_kprobe(&trampoline_p);
 }
 
 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 {
 	if (p->addr ==
-		(kprobe_opcode_t *)((struct fnptr *)kretprobe_trampoline)->ip)
+		dereference_function_descriptor(kretprobe_trampoline))
 		return 1;
 
 	return 0;