kprobes: treewide: Replace arch_deref_entry_point() with dereference_symbol_descriptor()

~15 years ago kprobes grew the 'arch_deref_entry_point()' __weak function:

  3d7e33825d87: ("jprobes: make jprobes a little safer for users")

But this is just open-coded dereference_symbol_descriptor() in essence, and
its obscure nature was causing bugs.

Just use the real thing and remove arch_deref_entry_point().

Link: https://lkml.kernel.org/r/163163043630.489837.7924988885652708696.stgit@devnote2

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Tested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

arch/ia64/kernel/kprobes.c

@@ -891,11 +891,6 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 	return ret;
 }
 
-unsigned long arch_deref_entry_point(void *entry)
-{
-	return ((struct fnptr *)entry)->ip;
-}
-
 static struct kprobe trampoline_p = {
 	.pre_handler = trampoline_probe_handler
 };

arch/powerpc/kernel/kprobes.c

@@ -542,17 +542,6 @@ int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 }
 NOKPROBE_SYMBOL(kprobe_fault_handler);
 
-unsigned long arch_deref_entry_point(void *entry)
-{
-#ifdef PPC64_ELF_ABI_v1
-	if (!kernel_text_address((unsigned long)entry))
-		return ppc_global_function_entry(entry);
-	else
-#endif
-		return (unsigned long)entry;
-}
-NOKPROBE_SYMBOL(arch_deref_entry_point);
-
 static struct kprobe trampoline_p = {
 	.addr = (kprobe_opcode_t *) &kretprobe_trampoline,
 	.pre_handler = trampoline_probe_handler

include/linux/kprobes.h

@@ -381,7 +381,6 @@ int register_kprobe(struct kprobe *p);
 void unregister_kprobe(struct kprobe *p);
 int register_kprobes(struct kprobe **kps, int num);
 void unregister_kprobes(struct kprobe **kps, int num);
-unsigned long arch_deref_entry_point(void *);
 
 int register_kretprobe(struct kretprobe *rp);
 void unregister_kretprobe(struct kretprobe *rp);

kernel/kprobes.c

@@ -1861,11 +1861,6 @@ static struct notifier_block kprobe_exceptions_nb = {
 	.priority = 0x7fffffff /* we need to be notified first */
 };
 
-unsigned long __weak arch_deref_entry_point(void *entry)
-{
-	return (unsigned long)entry;
-}
-
 #ifdef CONFIG_KRETPROBES
 
 unsigned long __kretprobe_trampoline_handler(struct pt_regs *regs,
@@ -2327,7 +2322,7 @@ static int __init populate_kprobe_blacklist(unsigned long *start,
 	int ret;
 
 	for (iter = start; iter < end; iter++) {
-		entry = arch_deref_entry_point((void *)*iter);
+		entry = (unsigned long)dereference_symbol_descriptor((void *)*iter);
 		ret = kprobe_add_ksym_blacklist(entry);
 		if (ret == -EINVAL)
 			continue;

lib/error-inject.c

@@ -8,6 +8,7 @@
 #include <linux/mutex.h>
 #include <linux/list.h>
 #include <linux/slab.h>
+#include <asm/sections.h>
 
 /* Whitelist of symbols that can be overridden for error injection. */
 static LIST_HEAD(error_injection_list);
@@ -64,7 +65,7 @@ static void populate_error_injection_list(struct error_injection_entry *start,
 
 	mutex_lock(&ei_mutex);
 	for (iter = start; iter < end; iter++) {
-		entry = arch_deref_entry_point((void *)iter->addr);
+		entry = (unsigned long)dereference_symbol_descriptor((void *)iter->addr);
 
 		if (!kernel_text_address(entry) ||
 		    !kallsyms_lookup_size_offset(entry, &size, &offset)) {