kallsyms: remove unused arch_get_kallsym() helper

The arch_get_kallsym() function was introduced so that x86 could override
it, but that override was removed in bf904d27 ("x86/pti/64: Remove
the SYSCALL64 entry trampoline"), so now this does nothing except causing
a warning about a missing prototype:

kernel/kallsyms.c:662:12: error: no previous prototype for 'arch_get_kallsym' [-Werror=missing-prototypes]
  662 | int __weak arch_get_kallsym(unsigned int symnum, unsigned long *value,

Restore the old behavior before d83212d5 ("kallsyms, x86: Export
addresses of PTI entry trampolines") to simplify the code and avoid
the warning.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Alan Maguire <alan.maguire@oracle.com>
[mcgrof: fold in bpf selftest fix]
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>

kernel/kallsyms.c

@@ -646,7 +646,6 @@ int sprint_backtrace_build_id(char *buffer, unsigned long address)
 /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
 struct kallsym_iter {
 	loff_t pos;
-	loff_t pos_arch_end;
 	loff_t pos_mod_end;
 	loff_t pos_ftrace_mod_end;
 	loff_t pos_bpf_end;
@@ -659,29 +658,9 @@ struct kallsym_iter {
 	int show_value;
 };
 
-int __weak arch_get_kallsym(unsigned int symnum, unsigned long *value,
-			    char *type, char *name)
-{
-	return -EINVAL;
-}
-
-static int get_ksymbol_arch(struct kallsym_iter *iter)
-{
-	int ret = arch_get_kallsym(iter->pos - kallsyms_num_syms,
-				   &iter->value, &iter->type,
-				   iter->name);
-
-	if (ret < 0) {
-		iter->pos_arch_end = iter->pos;
-		return 0;
-	}
-
-	return 1;
-}
-
 static int get_ksymbol_mod(struct kallsym_iter *iter)
 {
-	int ret = module_get_kallsym(iter->pos - iter->pos_arch_end,
+	int ret = module_get_kallsym(iter->pos - kallsyms_num_syms,
 				     &iter->value, &iter->type,
 				     iter->name, iter->module_name,
 				     &iter->exported);
@@ -764,7 +743,6 @@ static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
 	iter->nameoff = get_symbol_offset(new_pos);
 	iter->pos = new_pos;
 	if (new_pos == 0) {
-		iter->pos_arch_end = 0;
 		iter->pos_mod_end = 0;
 		iter->pos_ftrace_mod_end = 0;
 		iter->pos_bpf_end = 0;
@@ -780,10 +758,6 @@ static int update_iter_mod(struct kallsym_iter *iter, loff_t pos)
 {
 	iter->pos = pos;
 
-	if ((!iter->pos_arch_end || iter->pos_arch_end > pos) &&
-	    get_ksymbol_arch(iter))
-		return 1;
-
 	if ((!iter->pos_mod_end || iter->pos_mod_end > pos) &&
 	    get_ksymbol_mod(iter))
 		return 1;

tools/testing/selftests/bpf/progs/bpf_iter_ksym.c

@@ -59,9 +59,7 @@ int dump_ksym(struct bpf_iter__ksym *ctx)
 	} else {
 		BPF_SEQ_PRINTF(seq, "0x%llx %c %s ", value, type, iter->name);
 	}
-	if (!iter->pos_arch_end || iter->pos_arch_end > iter->pos)
-		BPF_SEQ_PRINTF(seq, "CORE ");
-	else if (!iter->pos_mod_end || iter->pos_mod_end > iter->pos)
+	if (!iter->pos_mod_end || iter->pos_mod_end > iter->pos)
 		BPF_SEQ_PRINTF(seq, "MOD ");
 	else if (!iter->pos_ftrace_mod_end || iter->pos_ftrace_mod_end > iter->pos)
 		BPF_SEQ_PRINTF(seq, "FTRACE_MOD ");