From 2cbb20b008dba39893f0e296dc8ca312f40a9a0e Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Fri, 21 Mar 2025 12:53:32 -0700 Subject: 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: Ingo Molnar Suggested-by: Steven Rostedt Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Acked-by: Thomas Gleixner Cc: Linus Torvalds Link: https://lore.kernel.org/r/fb94fc9303d48a5ed370498f54500cc4c338eb6d.1742586676.git.jpoimboe@kernel.org --- kernel/Makefile | 5 +++++ kernel/entry/Makefile | 3 +++ kernel/sched/Makefile | 5 +++++ kernel/time/Makefile | 6 ++++++ 4 files changed, 19 insertions(+) (limited to 'kernel') diff --git a/kernel/Makefile b/kernel/Makefile index 87866b037fbe..434929de17ef 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -21,6 +21,11 @@ ifdef CONFIG_FUNCTION_TRACER CFLAGS_REMOVE_irq_work.o = $(CC_FLAGS_FTRACE) endif +# Branch profiling isn't noinstr-safe +ifdef CONFIG_TRACE_BRANCH_PROFILING +CFLAGS_context_tracking.o += -DDISABLE_BRANCH_PROFILING +endif + # Prevents flicker of uninteresting __do_softirq()/__local_bh_disable_ip() # in coverage traces. KCOV_INSTRUMENT_softirq.o := n diff --git a/kernel/entry/Makefile b/kernel/entry/Makefile index 095c775e001e..d4b8bd0af79b 100644 --- a/kernel/entry/Makefile +++ b/kernel/entry/Makefile @@ -6,6 +6,9 @@ KASAN_SANITIZE := n UBSAN_SANITIZE := n KCOV_INSTRUMENT := n +# Branch profiling isn't noinstr-safe +ccflags-$(CONFIG_TRACE_BRANCH_PROFILING) += -DDISABLE_BRANCH_PROFILING + CFLAGS_REMOVE_common.o = -fstack-protector -fstack-protector-strong CFLAGS_common.o += -fno-stack-protector diff --git a/kernel/sched/Makefile b/kernel/sched/Makefile index 976092b7bd45..8ae86371ddcd 100644 --- a/kernel/sched/Makefile +++ b/kernel/sched/Makefile @@ -22,6 +22,11 @@ ifneq ($(CONFIG_SCHED_OMIT_FRAME_POINTER),y) CFLAGS_core.o := $(PROFILING) -fno-omit-frame-pointer endif +# Branch profiling isn't noinstr-safe +ifdef CONFIG_TRACE_BRANCH_PROFILING +CFLAGS_build_policy.o += -DDISABLE_BRANCH_PROFILING +CFLAGS_build_utility.o += -DDISABLE_BRANCH_PROFILING +endif # # Build efficiency: # diff --git a/kernel/time/Makefile b/kernel/time/Makefile index fe0ae82124fe..e6e9b85d4db5 100644 --- a/kernel/time/Makefile +++ b/kernel/time/Makefile @@ -1,4 +1,10 @@ # SPDX-License-Identifier: GPL-2.0 + +# Branch profiling isn't noinstr-safe +ifdef CONFIG_TRACE_BRANCH_PROFILING +CFLAGS_sched_clock.o += -DDISABLE_BRANCH_PROFILING +endif + obj-y += time.o timer.o hrtimer.o sleep_timeout.o obj-y += timekeeping.o ntp.o clocksource.o jiffies.o timer_list.o obj-y += timeconv.o timecounter.o alarmtimer.o -- cgit v1.2.3