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
  ...

Author: torvalds

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"

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

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/

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>

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
 

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();
 }
 

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 */

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>

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

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
 #