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Merge tag 'objtool-core-2025-03-22' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull objtool updates from Ingo Molnar: - The biggest change is the new option to automatically fail the build on objtool warnings: CONFIG_OBJTOOL_WERROR. While there are no currently known unfixed false positives left, such an expansion in the severity of objtool warnings inevitably creates a risk of build failures, so it's disabled by default and depends on !COMPILE_TEST, so it shouldn't be enabled on allyesconfig/allmodconfig builds and won't be forced on people who just accept build-time defaults in 'make oldconfig'. While the option is strongly recommended, only people who enable it explicitly should see it. (Josh Poimboeuf) - Disable branch profiling in noinstr code with a broad brush that includes all of arch/x86/ and kernel/sched/. (Josh Poimboeuf) - Create backup object files on objtool errors and print exact objtool arguments to make failure analysis easier (Josh Poimboeuf) - Improve noreturn handling (Josh Poimboeuf) - Improve rodata handling (Tiezhu Yang) - Support jump tables, switch tables and goto tables on LoongArch (Tiezhu Yang) - Misc cleanups and fixes (Josh Poimboeuf, David Engraf, Ingo Molnar) * tag 'objtool-core-2025-03-22' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (22 commits) tracing: Disable branch profiling in noinstr code objtool: Use O_CREAT with explicit mode mask objtool: Add CONFIG_OBJTOOL_WERROR objtool: Create backup on error and print args objtool: Change "warning:" to "error:" for --Werror objtool: Add --Werror option objtool: Add --output option objtool: Upgrade "Linked object detected" warning to error objtool: Consolidate option validation objtool: Remove --unret dependency on --rethunk objtool: Increase per-function WARN_FUNC() rate limit objtool: Update documentation objtool: Improve __noreturn annotation warning objtool: Fix error handling inconsistencies in check() x86/traps: Make exc_double_fault() consistently noreturn LoongArch: Enable jump table for objtool objtool/LoongArch: Add support for goto table objtool/LoongArch: Add support for switch table objtool: Handle PC relative relocation type objtool: Handle different entry size of rodata ...
2 parents 2360899 + 2cbb20b commit 5a658af

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35 files changed

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-252
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+571
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lines changed

‎arch/loongarch/Kconfig

+3
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@@ -291,6 +291,9 @@ config AS_HAS_LBT_EXTENSION
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config AS_HAS_LVZ_EXTENSION
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def_bool $(as-instr,hvcl 0)
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config CC_HAS_ANNOTATE_TABLEJUMP
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def_bool $(cc-option,-mannotate-tablejump)
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menu "Kernel type and options"
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source "kernel/Kconfig.hz"

‎arch/loongarch/Makefile

+5-1
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@@ -101,7 +101,11 @@ KBUILD_AFLAGS += $(call cc-option,-mthin-add-sub) $(call cc-option,-Wa$(comma)
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KBUILD_CFLAGS += $(call cc-option,-mthin-add-sub) $(call cc-option,-Wa$(comma)-mthin-add-sub)
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103103
ifdef CONFIG_OBJTOOL
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KBUILD_CFLAGS += -fno-jump-tables
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ifdef CONFIG_CC_HAS_ANNOTATE_TABLEJUMP
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KBUILD_CFLAGS += -mannotate-tablejump
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else
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KBUILD_CFLAGS += -fno-jump-tables # keep compatibility with older compilers
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endif
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endif
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KBUILD_RUSTFLAGS += --target=loongarch64-unknown-none-softfloat -Ccode-model=small

‎arch/x86/Kbuild

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@@ -1,4 +1,8 @@
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# SPDX-License-Identifier: GPL-2.0
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# Branch profiling isn't noinstr-safe. Disable it for arch/x86/*
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subdir-ccflags-$(CONFIG_TRACE_BRANCH_PROFILING) += -DDISABLE_BRANCH_PROFILING
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obj-$(CONFIG_ARCH_HAS_CC_PLATFORM) += coco/
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obj-y += entry/

‎arch/x86/coco/sev/core.c

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@@ -9,8 +9,6 @@
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#define pr_fmt(fmt) "SEV: " fmt
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#define DISABLE_BRANCH_PROFILING
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#include <linux/sched/debug.h> /* For show_regs() */
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#include <linux/percpu-defs.h>
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#include <linux/cc_platform.h>

‎arch/x86/kernel/head64.c

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@@ -5,8 +5,6 @@
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* Copyright (C) 2000 Andrea Arcangeli <[email protected]> SuSE
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*/
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8-
#define DISABLE_BRANCH_PROFILING
9-
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/* cpu_feature_enabled() cannot be used this early */
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#define USE_EARLY_PGTABLE_L5
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‎arch/x86/kernel/traps.c

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@@ -379,6 +379,21 @@ __visible void __noreturn handle_stack_overflow(struct pt_regs *regs,
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}
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#endif
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/*
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* Prevent the compiler and/or objtool from marking the !CONFIG_X86_ESPFIX64
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* version of exc_double_fault() as noreturn. Otherwise the noreturn mismatch
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* between configs triggers objtool warnings.
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*
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* This is a temporary hack until we have compiler or plugin support for
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* annotating noreturns.
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*/
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#ifdef CONFIG_X86_ESPFIX64
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#define always_true() true
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#else
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bool always_true(void);
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bool __weak always_true(void) { return true; }
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#endif
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/*
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* Runs on an IST stack for x86_64 and on a special task stack for x86_32.
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*
@@ -514,7 +529,8 @@ DEFINE_IDTENTRY_DF(exc_double_fault)
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pr_emerg("PANIC: double fault, error_code: 0x%lx\n", error_code);
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die("double fault", regs, error_code);
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panic("Machine halted.");
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if (always_true())
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panic("Machine halted.");
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instrumentation_end();
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}
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‎arch/x86/mm/kasan_init_64.c

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@@ -1,5 +1,4 @@
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// SPDX-License-Identifier: GPL-2.0
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#define DISABLE_BRANCH_PROFILING
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#define pr_fmt(fmt) "kasan: " fmt
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/* cpu_feature_enabled() cannot be used this early */

‎arch/x86/mm/mem_encrypt_amd.c

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@@ -7,8 +7,6 @@
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* Author: Tom Lendacky <[email protected]>
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*/
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#define DISABLE_BRANCH_PROFILING
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#include <linux/linkage.h>
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#include <linux/init.h>
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#include <linux/mm.h>

‎arch/x86/mm/mem_encrypt_identity.c

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@@ -7,8 +7,6 @@
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* Author: Tom Lendacky <[email protected]>
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*/
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#define DISABLE_BRANCH_PROFILING
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/*
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* Since we're dealing with identity mappings, physical and virtual
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* addresses are the same, so override these defines which are ultimately

‎drivers/acpi/Makefile

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@@ -5,6 +5,10 @@
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ccflags-$(CONFIG_ACPI_DEBUG) += -DACPI_DEBUG_OUTPUT
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ifdef CONFIG_TRACE_BRANCH_PROFILING
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CFLAGS_processor_idle.o += -DDISABLE_BRANCH_PROFILING
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endif
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#
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# ACPI Boot-Time Table Parsing
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#

‎drivers/cpuidle/Makefile

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@@ -3,6 +3,9 @@
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# Makefile for cpuidle.
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#
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# Branch profiling isn't noinstr-safe
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ccflags-$(CONFIG_TRACE_BRANCH_PROFILING) += -DDISABLE_BRANCH_PROFILING
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obj-y += cpuidle.o driver.o governor.o sysfs.o governors/
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obj-$(CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED) += coupled.o
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obj-$(CONFIG_DT_IDLE_STATES) += dt_idle_states.o

‎drivers/idle/Makefile

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@@ -1,3 +1,6 @@
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# SPDX-License-Identifier: GPL-2.0-only
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obj-$(CONFIG_INTEL_IDLE) += intel_idle.o
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# Branch profiling isn't noinstr-safe
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ccflags-$(CONFIG_TRACE_BRANCH_PROFILING) += -DDISABLE_BRANCH_PROFILING
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obj-$(CONFIG_INTEL_IDLE) += intel_idle.o

‎kernel/Makefile

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@@ -21,6 +21,11 @@ ifdef CONFIG_FUNCTION_TRACER
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CFLAGS_REMOVE_irq_work.o = $(CC_FLAGS_FTRACE)
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endif
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# Branch profiling isn't noinstr-safe
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ifdef CONFIG_TRACE_BRANCH_PROFILING
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CFLAGS_context_tracking.o += -DDISABLE_BRANCH_PROFILING
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endif
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# Prevents flicker of uninteresting __do_softirq()/__local_bh_disable_ip()
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# in coverage traces.
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KCOV_INSTRUMENT_softirq.o := n

‎kernel/entry/Makefile

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@@ -6,6 +6,9 @@ KASAN_SANITIZE := n
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UBSAN_SANITIZE := n
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KCOV_INSTRUMENT := n
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9+
# Branch profiling isn't noinstr-safe
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ccflags-$(CONFIG_TRACE_BRANCH_PROFILING) += -DDISABLE_BRANCH_PROFILING
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CFLAGS_REMOVE_common.o = -fstack-protector -fstack-protector-strong
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CFLAGS_common.o += -fno-stack-protector
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‎kernel/sched/Makefile

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@@ -22,6 +22,11 @@ ifneq ($(CONFIG_SCHED_OMIT_FRAME_POINTER),y)
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CFLAGS_core.o := $(PROFILING) -fno-omit-frame-pointer
2323
endif
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25+
# Branch profiling isn't noinstr-safe
26+
ifdef CONFIG_TRACE_BRANCH_PROFILING
27+
CFLAGS_build_policy.o += -DDISABLE_BRANCH_PROFILING
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CFLAGS_build_utility.o += -DDISABLE_BRANCH_PROFILING
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endif
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#
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# Build efficiency:
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#

‎kernel/time/Makefile

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@@ -1,4 +1,10 @@
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# SPDX-License-Identifier: GPL-2.0
2+
3+
# Branch profiling isn't noinstr-safe
4+
ifdef CONFIG_TRACE_BRANCH_PROFILING
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CFLAGS_sched_clock.o += -DDISABLE_BRANCH_PROFILING
6+
endif
7+
28
obj-y += time.o timer.o hrtimer.o sleep_timeout.o
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obj-y += timekeeping.o ntp.o clocksource.o jiffies.o timer_list.o
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obj-y += timeconv.o timecounter.o alarmtimer.o

‎lib/Kconfig.debug

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@@ -545,6 +545,17 @@ config FRAME_POINTER
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config OBJTOOL
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bool
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548+
config OBJTOOL_WERROR
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bool "Upgrade objtool warnings to errors"
550+
depends on OBJTOOL && !COMPILE_TEST
551+
help
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Fail the build on objtool warnings.
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Objtool warnings can indicate kernel instability, including boot
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failures. This option is highly recommended.
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If unsure, say Y.
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548559
config STACK_VALIDATION
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bool "Compile-time stack metadata validation"
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depends on HAVE_STACK_VALIDATION && UNWINDER_FRAME_POINTER

‎lib/Makefile

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@@ -5,6 +5,11 @@
55

66
ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
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8+
# Branch profiling isn't noinstr-safe
9+
ifdef CONFIG_TRACE_BRANCH_PROFILING
10+
CFLAGS_smp_processor_id.o += -DDISABLE_BRANCH_PROFILING
11+
endif
12+
813
# These files are disabled because they produce lots of non-interesting and/or
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# flaky coverage that is not a function of syscall inputs. For example,
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# rbtree can be global and individual rotations don't correlate with inputs.

‎scripts/Makefile.lib

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@@ -277,6 +277,7 @@ objtool-args-$(CONFIG_HAVE_STATIC_CALL_INLINE) += --static-call
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objtool-args-$(CONFIG_HAVE_UACCESS_VALIDATION) += --uaccess
278278
objtool-args-$(CONFIG_GCOV_KERNEL) += --no-unreachable
279279
objtool-args-$(CONFIG_PREFIX_SYMBOLS) += --prefix=$(CONFIG_FUNCTION_PADDING_BYTES)
280+
objtool-args-$(CONFIG_OBJTOOL_WERROR) += --Werror --backtrace
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281282
objtool-args = $(objtool-args-y) \
282283
$(if $(delay-objtool), --link) \

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