objtool: Add arch specific function arch_ftrace_match()

Add architecture specific function to look for relocation records
pointing to architecture specific symbols.
Suggested-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Tested-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Reviewed-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Sathvika Vasireddy <sv@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20221114175754.1131267-15-sv@linux.ibm.com

tools/objtool/arch/x86/decode.c

@@ -23,6 +23,11 @@
 #include <objtool/builtin.h>
 #include <arch/elf.h>
 
+int arch_ftrace_match(char *name)
+{
+	return !strcmp(name, "__fentry__");
+}
+
 static int is_x86_64(const struct elf *elf)
 {
 	switch (elf->ehdr.e_machine) {

tools/objtool/check.c

@@ -2316,7 +2316,7 @@ static int classify_symbols(struct objtool_file *file)
 			if (arch_is_rethunk(func))
 				func->return_thunk = true;
 
-			if (!strcmp(func->name, "__fentry__"))
+			if (arch_ftrace_match(func->name))
 				func->fentry = true;
 
 			if (is_profiling_func(func->name))

tools/objtool/include/objtool/arch.h

@@ -69,6 +69,8 @@ struct stack_op {
 
 struct instruction;
 
+int arch_ftrace_match(char *name);
+
 void arch_initial_func_cfi_state(struct cfi_init_state *state);
 
 int arch_decode_instruction(struct objtool_file *file, const struct section *sec,