x86/unwind/orc: Fix ORC unwind table alignment

commit f76a16adc485699f95bb71fce114f97c832fe664 upstream.

The .orc_unwind section is a packed array of 6-byte structs.  It's
currently aligned to 6 bytes, which is causing warnings in the LLD
linker.

Six isn't a power of two, so it's not a valid alignment value.  The
actual alignment doesn't matter much because it's an array of packed
structs.  An alignment of two is sufficient.  In reality it always gets
aligned to four bytes because it comes immediately after the
4-byte-aligned .orc_unwind_ip section.

Fixes: ee9f8fce9964 ("x86/unwind: Add the ORC unwinder")
Reported-by: Nick Desaulniers <ndesaulniers@google.com>
Reported-by: Dmitry Golovin <dima@golovin.in>
Reported-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: https://github.com/ClangBuiltLinux/linux/issues/218
Link: https://lkml.kernel.org/r/d55027ee95fe73e952dcd8be90aebd31b0095c45.1551892041.git.jpoimboe@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index fcec26d60d8ccf02f2a51123767d6cc62f8c7987..c229ffbed6d4c16ef292f2022700dd0112dc9511 100644 (file)
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -696,7 +696,7 @@
                KEEP(*(.orc_unwind_ip))                                 \
                VMLINUX_SYMBOL(__stop_orc_unwind_ip) = .;               \
        }                                                               \
-       . = ALIGN(6);                                                   \
+       . = ALIGN(2);                                                   \
        .orc_unwind : AT(ADDR(.orc_unwind) - LOAD_OFFSET) {             \
                VMLINUX_SYMBOL(__start_orc_unwind) = .;                 \
                KEEP(*(.orc_unwind))                                    \