linux-kernel - [PATCH v3 36/59] ftrace: Add HAVE_DYNAMIC_FTRACE_NO

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Date:   Thu, 15 Sep 2022 13:11:15 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org, x86@...nel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Andrew Cooper <Andrew.Cooper3@...rix.com>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Johannes Wikner <kwikner@...z.ch>,
        Alyssa Milburn <alyssa.milburn@...ux.intel.com>,
        Jann Horn <jannh@...gle.com>, "H.J. Lu" <hjl.tools@...il.com>,
        Joao Moreira <joao.moreira@...el.com>,
        Joseph Nuzman <joseph.nuzman@...el.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Juergen Gross <jgross@...e.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        K Prateek Nayak <kprateek.nayak@....com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH v3 36/59] ftrace: Add HAVE_DYNAMIC_FTRACE_NO_PATCHABLE

From: Peter Zijlstra <peterz@...radead.org>

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@...radead.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 include/asm-generic/vmlinux.lds.h |   11 ++++++++++-
 kernel/trace/Kconfig              |    6 ++++++
 tools/objtool/check.c             |    3 ++-
 3 files changed, 18 insertions(+), 2 deletions(-)

--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -159,6 +159,14 @@
 #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
@@ -177,7 +185,7 @@
 #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;
@@ -1029,6 +1037,7 @@
 
 #define COMMON_DISCARDS							\
 	SANITIZER_DISCARDS						\
+	PATCHABLE_DISCARDS						\
 	*(.discard)							\
 	*(.discard.*)							\
 	*(.modinfo)							\
--- a/kernel/trace/Kconfig
+++ b/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
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -4196,7 +4196,8 @@ static int validate_ibt(struct objtool_f
 		    !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)