Merge tag 'objtool-core-2025-12-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull objtool updates from Ingo Molnar:

 - klp-build livepatch module generation (Josh Poimboeuf)

   Introduce new objtool features and a klp-build script to generate
   livepatch modules using a source .patch as input.

   This builds on concepts from the longstanding out-of-tree kpatch
   project which began in 2012 and has been used for many years to
   generate livepatch modules for production kernels. However, this is a
   complete rewrite which incorporates hard-earned lessons from 12+
   years of maintaining kpatch.

   Key improvements compared to kpatch-build:

    - Integrated with objtool: Leverages objtool's existing control-flow
      graph analysis to help detect changed functions.

    - Works on vmlinux.o: Supports late-linked objects, making it
      compatible with LTO, IBT, and similar.

    - Simplified code base: ~3k fewer lines of code.

    - Upstream: No more out-of-tree #ifdef hacks, far less cruft.

    - Cleaner internals: Vastly simplified logic for
      symbol/section/reloc inclusion and special section extraction.

    - Robust __LINE__ macro handling: Avoids false positive binary diffs
      caused by the __LINE__ macro by introducing a fix-patch-lines
      script which injects #line directives into the source .patch to
      preserve the original line numbers at compile time.

 - Disassemble code with libopcodes instead of running objdump
   (Alexandre Chartre)

 - Disassemble support (-d option to objtool) by Alexandre Chartre,
   which supports the decoding of various Linux kernel code generation
   specials such as alternatives:

      17ef:  sched_balance_find_dst_group+0x62f                 mov    0x34(%r9),%edx
      17f3:  sched_balance_find_dst_group+0x633               | <alternative.17f3>             | X86_FEATURE_POPCNT
      17f3:  sched_balance_find_dst_group+0x633               | call   0x17f8 <__sw_hweight64> | popcnt %rdi,%rax
      17f8:  sched_balance_find_dst_group+0x638                 cmp    %eax,%edx

   ... jump table alternatives:

      1895:  sched_use_asym_prio+0x5                            test   $0x8,%ch
      1898:  sched_use_asym_prio+0x8                            je     0x18a9 <sched_use_asym_prio+0x19>
      189a:  sched_use_asym_prio+0xa                          | <jump_table.189a>                        | JUMP
      189a:  sched_use_asym_prio+0xa                          | jmp    0x18ae <sched_use_asym_prio+0x1e> | nop2
      189c:  sched_use_asym_prio+0xc                            mov    $0x1,%eax
      18a1:  sched_use_asym_prio+0x11                           and    $0x80,%ecx

   ... exception table alternatives:

    native_read_msr:
      5b80:  native_read_msr+0x0                                                     mov    %edi,%ecx
      5b82:  native_read_msr+0x2                                                   | <ex_table.5b82> | EXCEPTION
      5b82:  native_read_msr+0x2                                                   | rdmsr           | resume at 0x5b84 <native_read_msr+0x4>
      5b84:  native_read_msr+0x4                                                     shl    $0x20,%rdx

   .... x86 feature flag decoding (also see the X86_FEATURE_POPCNT
        example in sched_balance_find_dst_group() above):

      2faaf:  start_thread_common.constprop.0+0x1f                                    jne    0x2fba4 <start_thread_common.constprop.0+0x114>
      2fab5:  start_thread_common.constprop.0+0x25                                  | <alternative.2fab5>                  | X86_FEATURE_ALWAYS                                  | X86_BUG_NULL_SEG
      2fab5:  start_thread_common.constprop.0+0x25                                  | jmp    0x2faba <.altinstr_aux+0x2f4> | jmp    0x4b0 <start_thread_common.constprop.0+0x3f> | nop5
      2faba:  start_thread_common.constprop.0+0x2a                                    mov    $0x2b,%eax

   ... NOP sequence shortening:

      1048e2:  snapshot_write_finalize+0xc2                                            je     0x104917 <snapshot_write_finalize+0xf7>
      1048e4:  snapshot_write_finalize+0xc4                                            nop6
      1048ea:  snapshot_write_finalize+0xca                                            nop11
      1048f5:  snapshot_write_finalize+0xd5                                            nop11
      104900:  snapshot_write_finalize+0xe0                                            mov    %rax,%rcx
      104903:  snapshot_write_finalize+0xe3                                            mov    0x10(%rdx),%rax

   ... and much more.

 - Function validation tracing support (Alexandre Chartre)

 - Various -ffunction-sections fixes (Josh Poimboeuf)

 - Clang AutoFDO (Automated Feedback-Directed Optimizations) support
   (Josh Poimboeuf)

 - Misc fixes and cleanups (Borislav Petkov, Chen Ni, Dylan Hatch, Ingo
   Molnar, John Wang, Josh Poimboeuf, Pankaj Raghav, Peter Zijlstra,
   Thorsten Blum)

* tag 'objtool-core-2025-12-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (129 commits)
  objtool: Fix segfault on unknown alternatives
  objtool: Build with disassembly can fail when including bdf.h
  objtool: Trim trailing NOPs in alternative
  objtool: Add wide output for disassembly
  objtool: Compact output for alternatives with one instruction
  objtool: Improve naming of group alternatives
  objtool: Add Function to get the name of a CPU feature
  objtool: Provide access to feature and flags of group alternatives
  objtool: Fix address references in alternatives
  objtool: Disassemble jump table alternatives
  objtool: Disassemble exception table alternatives
  objtool: Print addresses with alternative instructions
  objtool: Disassemble group alternatives
  objtool: Print headers for alternatives
  objtool: Preserve alternatives order
  objtool: Add the --disas=<function-pattern> action
  objtool: Do not validate IBT for .return_sites and .call_sites
  objtool: Improve tracing of alternative instructions
  objtool: Add functions to better name alternatives
  objtool: Identify the different types of alternatives
  ...

1 files changed, 46 insertions, 30 deletions

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index caef183a73bc..a464ff6c1a61 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -87,39 +87,56 @@
 #define ALIGN_FUNCTION()  . = ALIGN(CONFIG_FUNCTION_ALIGNMENT)
 
 /*
- * LD_DEAD_CODE_DATA_ELIMINATION option enables -fdata-sections, which
- * generates .data.identifier sections, which need to be pulled in with
- * .data. We don't want to pull in .data..other sections, which Linux
- * has defined. Same for text and bss.
+ * Support -ffunction-sections by matching .text and .text.*,
+ * but exclude '.text..*', .text.startup[.*], and .text.exit[.*].
  *
- * With LTO_CLANG, the linker also splits sections by default, so we need
- * these macros to combine the sections during the final link.
+ * .text.startup and .text.startup.* are matched later by INIT_TEXT, and
+ * .text.exit and .text.exit.* are matched later by EXIT_TEXT, so they must be
+ * explicitly excluded here.
  *
- * With AUTOFDO_CLANG and PROPELLER_CLANG, by default, the linker splits
- * text sections and regroups functions into subsections.
+ * Other .text.* sections that are typically grouped separately, such as
+ * .text.unlikely or .text.hot, must be matched explicitly before using
+ * TEXT_MAIN.
  *
- * RODATA_MAIN is not used because existing code already defines .rodata.x
- * sections to be brought in with rodata.
+ * NOTE: builds *with* and *without* -ffunction-sections are both supported by
+ * this single macro.  Even with -ffunction-sections, there may be some objects
+ * NOT compiled with the flag due to the use of a specific Makefile override
+ * like cflags-y or AUTOFDO_PROFILE_foo.o.  So this single catchall rule is
+ * needed to support mixed object builds.
+ *
+ * One implication is that functions named startup(), exit(), split(),
+ * unlikely(), hot(), and unknown() are not allowed in the kernel due to the
+ * ambiguity of their section names with -ffunction-sections.  For example,
+ * .text.startup could be __attribute__((constructor)) code in a *non*
+ * ffunction-sections object, which should be placed in .init.text; or it could
+ * be an actual function named startup() in an ffunction-sections object, which
+ * should be placed in .text.  The build will detect and complain about any such
+ * ambiguously named functions.
+ */
+#define TEXT_MAIN							\
+	.text								\
+	.text.[_0-9A-Za-df-rt-z]*					\
+	.text.s[_0-9A-Za-su-z]*		.text.s		.text.s.*	\
+	.text.st[_0-9A-Zb-z]*		.text.st	.text.st.*	\
+	.text.sta[_0-9A-Za-qs-z]*	.text.sta	.text.sta.*	\
+	.text.star[_0-9A-Za-su-z]*	.text.star	.text.star.*	\
+	.text.start[_0-9A-Za-tv-z]*	.text.start	.text.start.*	\
+	.text.startu[_0-9A-Za-oq-z]*	.text.startu	.text.startu.*	\
+	.text.startup[_0-9A-Za-z]*					\
+	.text.e[_0-9A-Za-wy-z]*		.text.e		.text.e.*	\
+	.text.ex[_0-9A-Za-hj-z]*	.text.ex	.text.ex.*	\
+	.text.exi[_0-9A-Za-su-z]*	.text.exi	.text.exi.*	\
+	.text.exit[_0-9A-Za-z]*
+
+/*
+ * Support -fdata-sections by matching .data, .data.*, and others,
+ * but exclude '.data..*'.
  */
-#if defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) || defined(CONFIG_LTO_CLANG) || \
-defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG)
-#define TEXT_MAIN .text .text.[0-9a-zA-Z_]*
-#else
-#define TEXT_MAIN .text
-#endif
-#if defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) || defined(CONFIG_LTO_CLANG)
 #define DATA_MAIN .data .data.[0-9a-zA-Z_]* .data.rel.* .data..L* .data..compoundliteral* .data.$__unnamed_* .data.$L*
 #define SDATA_MAIN .sdata .sdata.[0-9a-zA-Z_]*
 #define RODATA_MAIN .rodata .rodata.[0-9a-zA-Z_]* .rodata..L*
 #define BSS_MAIN .bss .bss.[0-9a-zA-Z_]* .bss..L* .bss..compoundliteral*
 #define SBSS_MAIN .sbss .sbss.[0-9a-zA-Z_]*
-#else
-#define DATA_MAIN .data .data.rel .data.rel.local
-#define SDATA_MAIN .sdata
-#define RODATA_MAIN .rodata
-#define BSS_MAIN .bss
-#define SBSS_MAIN .sbss
-#endif
 
 /*
  * GCC 4.5 and later have a 32 bytes section alignment for structures.
@@ -581,9 +598,8 @@ defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG)
  * during second ld run in second ld pass when generating System.map
  *
  * TEXT_MAIN here will match symbols with a fixed pattern (for example,
- * .text.hot or .text.unlikely) if dead code elimination or
- * function-section is enabled. Match these symbols first before
- * TEXT_MAIN to ensure they are grouped together.
+ * .text.hot or .text.unlikely).  Match those before TEXT_MAIN to ensure
+ * they get grouped together.
  *
  * Also placing .text.hot section at the beginning of a page, this
  * would help the TLB performance.
@@ -729,16 +745,16 @@ defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG)
 
 #define INIT_TEXT							\
 	*(.init.text .init.text.*)					\
-	*(.text.startup)
+	*(.text.startup .text.startup.*)
 
 #define EXIT_DATA							\
 	*(.exit.data .exit.data.*)					\
 	*(.fini_array .fini_array.*)					\
-	*(.dtors .dtors.*)						\
+	*(.dtors .dtors.*)
 
 #define EXIT_TEXT							\
 	*(.exit.text)							\
-	*(.text.exit)							\
+	*(.text.exit .text.exit.*)
 
 #define EXIT_CALL							\
 	*(.exitcall.exit)