Merge tag 'objtool-urgent-2025-12-06' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull objtool fixes from Ingo Molnar:
"Address various objtool scalability bugs/inefficiencies exposed

Merge tag 'objtool-urgent-2025-12-06' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull objtool fixes from Ingo Molnar:
"Address various objtool scalability bugs/inefficiencies exposed by
allmodconfig builds, plus improve the quality of alternatives
instructions generated code and disassembly"

* tag 'objtool-urgent-2025-12-06' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
objtool: Simplify .annotate_insn code generation output some more
objtool: Add more robust signal error handling, detect and warn about stack overflows
objtool: Remove newlines and tabs from annotation macros
objtool: Consolidate annotation macros
x86/asm: Remove ANNOTATE_DATA_SPECIAL usage
x86/alternative: Remove ANNOTATE_DATA_SPECIAL usage
objtool: Fix stack overflow in validate_branch()

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objtool: Add more robust signal error handling, detect and warn about stack overflows

When the kernel build fails due to an objtool segfault, the error
message is a bit obtuse and confusing:

make

objtool: Add more robust signal error handling, detect and warn about stack overflows

When the kernel build fails due to an objtool segfault, the error
message is a bit obtuse and confusing:

make[5]: *** [scripts/Makefile.build:503: drivers/scsi/qla2xxx/qla2xxx.o] Error 139
^^^^^^^^^
make[5]: *** Deleting file 'drivers/scsi/qla2xxx/qla2xxx.o'
make[4]: *** [scripts/Makefile.build:556: drivers/scsi/qla2xxx] Error 2
make[3]: *** [scripts/Makefile.build:556: drivers/scsi] Error 2
make[2]: *** [scripts/Makefile.build:556: drivers] Error 2
make[1]: *** [/home/jpoimboe/git/linux/Makefile:2013: .] Error 2
make: *** [Makefile:248: __sub-make] Error 2

Add a signal handler to objtool which prints an error message like if
the local stack has overflown (for which there's a chance as objtool
makes heavy use of recursion):

drivers/scsi/qla2xxx/qla2xxx.o: error: SIGSEGV: objtool stack overflow!

or:

drivers/scsi/qla2xxx/qla2xxx.o: error: SIGSEGV: objtool crash!

Also, re-raise the signal so the core dump still gets triggered.

[ mingo: Applied a build fix, added more comments and prettified the code. ]

Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Alexandre Chartre <alexandre.chartre@oracle.com>
Cc: David Laight <david.laight.linux@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/mi4tihk4dbncn7belrhp6ooudhpw4vdggerktu5333w3gqf3uf@vqlhc3y667mg

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