ftrace: Add HAVE_DYNAMIC_FTRACE_NO_PATCHABLE

x86 will shortly start using -fpatchable-function-entry for purposes
other than ftrace, make sure the __patchable_function_entry section
isn't merged in the mcount_loc section.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220903131154.420467-2-jolsa@kernel.org

include/asm-generic/vmlinux.lds.h

@@ -154,6 +154,14 @@
 #define MEM_DISCARD(sec) *(.mem##sec)
 #endif
 
+#ifndef CONFIG_HAVE_DYNAMIC_FTRACE_NO_PATCHABLE
+#define KEEP_PATCHABLE		KEEP(*(__patchable_function_entries))
+#define PATCHABLE_DISCARDS
+#else
+#define KEEP_PATCHABLE
+#define PATCHABLE_DISCARDS	*(__patchable_function_entries)
+#endif
+
 #ifdef CONFIG_FTRACE_MCOUNT_RECORD
 /*
  * The ftrace call sites are logged to a section whose name depends on the
@@ -172,7 +180,7 @@
 #define MCOUNT_REC()	. = ALIGN(8);				\
 			__start_mcount_loc = .;			\
 			KEEP(*(__mcount_loc))			\
-			KEEP(*(__patchable_function_entries))	\
+			KEEP_PATCHABLE				\
 			__stop_mcount_loc = .;			\
 			ftrace_stub_graph = ftrace_stub;	\
 			ftrace_ops_list_func = arch_ftrace_ops_list_func;
@@ -1024,6 +1032,7 @@
 
 #define COMMON_DISCARDS							\
 	SANITIZER_DISCARDS						\
+	PATCHABLE_DISCARDS						\
 	*(.discard)							\
 	*(.discard.*)							\
 	*(.modinfo)							\

kernel/trace/Kconfig

@@ -51,6 +51,12 @@ config HAVE_DYNAMIC_FTRACE_WITH_ARGS
 	 This allows for use of regs_get_kernel_argument() and
 	 kernel_stack_pointer().
 
+config HAVE_DYNAMIC_FTRACE_NO_PATCHABLE
+	bool
+	help
+	  If the architecture generates __patchable_function_entries sections
+	  but does not want them included in the ftrace locations.
+
 config HAVE_FTRACE_MCOUNT_RECORD
 	bool
 	help

tools/objtool/check.c

@@ -4113,7 +4113,8 @@ static int validate_ibt(struct objtool_file *file)
 		    !strcmp(sec->name, "__bug_table")			||
 		    !strcmp(sec->name, "__ex_table")			||
 		    !strcmp(sec->name, "__jump_table")			||
-		    !strcmp(sec->name, "__mcount_loc"))
+		    !strcmp(sec->name, "__mcount_loc")			||
+		    strstr(sec->name, "__patchable_function_entries"))
 			continue;
 
 		list_for_each_entry(reloc, &sec->reloc->reloc_list, list)