Commit 2cbb20b0 authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Ingo Molnar
Browse files

tracing: Disable branch profiling in noinstr code 



CONFIG_TRACE_BRANCH_PROFILING inserts a call to ftrace_likely_update()
for each use of likely() or unlikely().  That breaks noinstr rules if
the affected function is annotated as noinstr.

Disable branch profiling for files with noinstr functions.  In addition
to some individual files, this also includes the entire arch/x86
subtree, as well as the kernel/entry, drivers/cpuidle, and drivers/idle
directories, all of which are noinstr-heavy.

Due to the nature of how sched binaries are built by combining multiple
.c files into one, branch profiling is disabled more broadly across the
sched code than would otherwise be needed.

This fixes many warnings like the following:

  vmlinux.o: warning: objtool: do_syscall_64+0x40: call to ftrace_likely_update() leaves .noinstr.text section
  vmlinux.o: warning: objtool: __rdgsbase_inactive+0x33: call to ftrace_likely_update() leaves .noinstr.text section
  vmlinux.o: warning: objtool: handle_bug.isra.0+0x198: call to ftrace_likely_update() leaves .noinstr.text section
  ...

Reported-by: default avatarIngo Molnar <mingo@kernel.org>
Suggested-by: default avatarSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Acked-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/fb94fc9303d48a5ed370498f54500cc4c338eb6d.1742586676.git.jpoimboe@kernel.org
parent 73070466

arch/x86/Kbuild

+4 −0
Original line number Diff line number Diff line 
# SPDX-License-Identifier: GPL-2.0



# Branch profiling isn't noinstr-safe.  Disable it for arch/x86/*

subdir-ccflags-$(CONFIG_TRACE_BRANCH_PROFILING) += -DDISABLE_BRANCH_PROFILING



obj-$(CONFIG_ARCH_HAS_CC_PLATFORM) += coco/



obj-y += entry/

arch/x86/coco/sev/core.c

+0 −2
Original line number Diff line number Diff line
@@ -9,8 +9,6 @@ 


#define pr_fmt(fmt)	"SEV: " fmt



#define DISABLE_BRANCH_PROFILING



#include <linux/sched/debug.h>	/* For show_regs() */

#include <linux/percpu-defs.h>

#include <linux/cc_platform.h>

arch/x86/kernel/head64.c

+0 −2
Original line number Diff line number Diff line
@@ -5,8 +5,6 @@ 
 *  Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE

 */



#define DISABLE_BRANCH_PROFILING



/* cpu_feature_enabled() cannot be used this early */

#define USE_EARLY_PGTABLE_L5

arch/x86/mm/kasan_init_64.c

+0 −1
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

#define DISABLE_BRANCH_PROFILING

#define pr_fmt(fmt) "kasan: " fmt



/* cpu_feature_enabled() cannot be used this early */

arch/x86/mm/mem_encrypt_amd.c

+0 −2
Original line number Diff line number Diff line
@@ -7,8 +7,6 @@ 
 * Author: Tom Lendacky <thomas.lendacky@amd.com>

 */



#define DISABLE_BRANCH_PROFILING



#include <linux/linkage.h>

#include <linux/init.h>

#include <linux/mm.h>