During x86_64 kernel build with CONFIG_KMSAN, the objtool warns following:
AR built-in.a
AR vmlinux.a
LD vmlinux.o
vmlinux.o: warning: objtool: handle_bug+0x4: call to
kmsan_unpoison_entry_regs() leaves .noinstr.text section
OBJCOPY modules.builtin.modinfo
GEN modules.builtin
MODPOST Module.symvers
CC .vmlinux.export.o
Moving kmsan_unpoison_entry_regs() _after_ instrumentation_begin() fixes
the warning.
There is decode_bug(regs->ip, &imm) is left before KMSAN unpoisoining, but
it has the return condition and if we include it after
instrumentation_begin() it results the warning "return with
instrumentation enabled", hence, I'm concerned that regs will not be KMSAN
unpoisoned if `ud_type == BUG_NONE` is true.
Link: https://lkml.kernel.org/r/20241016152407.3149001-1-snovitoll@gmail.com
Fixes: ba54d194f8 ("x86/traps: avoid KMSAN bugs originating from handle_bug()")
Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Cc: Borislav Petkov (AMD) <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
1db272864f