arm64/alternatives: move length validation inside the subsection

stable inclusion
from linux-4.19.137
commit 53f941777b9df64fa70fad775efabfcfb5db92c4

--------------------------------

[ Upstream commit 966a0acc ]

Commit f7b93d42 ("arm64/alternatives: use subsections for replacement
sequences") breaks LLVM's integrated assembler, because due to its
one-pass design, it cannot compute instruction sequence lengths before the
layout for the subsection has been finalized. This change fixes the build
by moving the .org directives inside the subsection, so they are processed
after the subsection layout is known.

Fixes: f7b93d42 ("arm64/alternatives: use subsections for replacement sequences")
Signed-off-by: NSami Tolvanen <samitolvanen@google.com>
Link: https://github.com/ClangBuiltLinux/linux/issues/1078
Link: https://lore.kernel.org/r/20200730153701.3892953-1-samitolvanen@google.comSigned-off-by: NWill Deacon <will@kernel.org>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

arch/arm64/include/asm/alternative.h

@@ -77,9 +77,9 @@ static inline void apply_alternatives_module(void *start, size_t length) { }
 	"663:\n\t"							\
 	newinstr "\n"							\
 	"664:\n\t"							\
-	".previous\n\t"							\
 	".org	. - (664b-663b) + (662b-661b)\n\t"			\
-	".org	. - (662b-661b) + (664b-663b)\n"			\
+	".org	. - (662b-661b) + (664b-663b)\n\t"			\
+	".previous\n"							\
 	".endif\n"
 
 #define __ALTERNATIVE_CFG_CB(oldinstr, feature, cfg_enabled, cb)	\