Merge tag 'objtool-core-2025-03-22' of git://git.kernel.org/pub/scm/l…

…inux/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 ...
mariux64 · Mar 25, 2025 · 5a658af · 5a658af
2 parents 2360899 + 2cbb20b
commit 5a658af
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Showing 35 changed files with 571 additions and 252 deletions.
diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
@@ -291,6 +291,9 @@ config AS_HAS_LBT_EXTENSION
 config AS_HAS_LVZ_EXTENSION
 	def_bool $(as-instr,hvcl 0)
 
+config CC_HAS_ANNOTATE_TABLEJUMP
+	def_bool $(cc-option,-mannotate-tablejump)
+
 menu "Kernel type and options"
 
 source "kernel/Kconfig.hz"

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

diff --git a/arch/x86/Kbuild b/arch/x86/Kbuild
@@ -1,4 +1,8 @@
 # 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/

diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
@@ -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>

diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
@@ -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
 

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

diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c
@@ -1,5 +1,4 @@
 // SPDX-License-Identifier: GPL-2.0
-#define DISABLE_BRANCH_PROFILING
 #define pr_fmt(fmt) "kasan: " fmt
 
 /* cpu_feature_enabled() cannot be used this early */

diff --git a/arch/x86/mm/mem_encrypt_amd.c b/arch/x86/mm/mem_encrypt_amd.c
@@ -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>

diff --git a/arch/x86/mm/mem_encrypt_identity.c b/arch/x86/mm/mem_encrypt_identity.c
@@ -7,8 +7,6 @@
  * Author: Tom Lendacky <thomas.lendacky@amd.com>
  */
 
-#define DISABLE_BRANCH_PROFILING
-
 /*
  * Since we're dealing with identity mappings, physical and virtual
  * addresses are the same, so override these defines which are ultimately

diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
@@ -5,6 +5,10 @@
 
 ccflags-$(CONFIG_ACPI_DEBUG)	+= -DACPI_DEBUG_OUTPUT
 
+ifdef CONFIG_TRACE_BRANCH_PROFILING
+CFLAGS_processor_idle.o += -DDISABLE_BRANCH_PROFILING
+endif
+
 #
 # ACPI Boot-Time Table Parsing
 #

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

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

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

diff --git a/lib/Makefile b/lib/Makefile
@@ -5,6 +5,11 @@
 
 ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
 
+# Branch profiling isn't noinstr-safe
+ifdef CONFIG_TRACE_BRANCH_PROFILING
+CFLAGS_smp_processor_id.o += -DDISABLE_BRANCH_PROFILING
+endif
+
 # These files are disabled because they produce lots of non-interesting and/or
 # flaky coverage that is not a function of syscall inputs. For example,
 # rbtree can be global and individual rotations don't correlate with inputs.

diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
@@ -277,6 +277,7 @@ objtool-args-$(CONFIG_HAVE_STATIC_CALL_INLINE)		+= --static-call
 objtool-args-$(CONFIG_HAVE_UACCESS_VALIDATION)		+= --uaccess
 objtool-args-$(CONFIG_GCOV_KERNEL)			+= --no-unreachable
 objtool-args-$(CONFIG_PREFIX_SYMBOLS)			+= --prefix=$(CONFIG_FUNCTION_PADDING_BYTES)
+objtool-args-$(CONFIG_OBJTOOL_WERROR)			+= --Werror --backtrace
 
 objtool-args = $(objtool-args-y)					\
 	$(if $(delay-objtool), --link)					\