ftrace: Test mcount_loc addr before calling ftrace_call_addr()

The addresses in the mcount_loc can be zeroed and then moved by KASLR
making them invalid addresses. ftrace_call_addr() for ARM 64 expects a
valid address to kernel text. If the addr read from the mcount_loc section
is invalid, it must not call ftrace_call_addr(). Move the addr check
before calling ftrace_call_addr() in ftrace_process_locs().

Cc: Masami Hiramatsu <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Masahiro Yamada <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Mark Brown <[email protected]>
Link: https://lore.kernel.org/[email protected]
Fixes: ef378c3 ("scripts/sorttable: Zero out weak functions in mcount_loc table")
Reported-by: Nathan Chancellor <[email protected]>
Reported-by: "Arnd Bergmann" <[email protected]>
Tested-by: Nathan Chancellor <[email protected]>
Closes: https://lore.kernel.org/all/20250225025631.GA271248@ax162/
Closes: https://lore.kernel.org/all/[email protected]/
Signed-off-by: Steven Rostedt (Google) <[email protected]>

Author: rostedt

kernel/trace/ftrace.c

@@ -7063,7 +7063,9 @@ static int ftrace_process_locs(struct module *mod,
 	pg = start_pg;
 	while (p < end) {
 		unsigned long end_offset;
-		addr = ftrace_call_adjust(*p++);
+
+		addr = *p++;
+
 		/*
 		 * Some architecture linkers will pad between
 		 * the different mcount_loc sections of different
@@ -7075,6 +7077,8 @@ static int ftrace_process_locs(struct module *mod,
 			continue;
 		}
 
+		addr = ftrace_call_adjust(addr);
+
 		end_offset = (pg->index+1) * sizeof(pg->records[0]);
 		if (end_offset > PAGE_SIZE << pg->order) {
 			/* We should have allocated enough */