Dear stable kernel maintainers,
Please consider accepting the following backport to 5.4 and 4.19 of
commit 4d6ffa27b8e5 ("x86/lib: Change .weak to SYM_FUNC_START_WEAK for
arch/x86/lib/mem*_64.S"), attached.

The patch to 5.4 had a conflict due to 5.4 missing upstream commit
e9b9d020c487 ("x86/asm: Annotate aliases") which first landed in
v5.5-rc1.

The patch to 4.19 had a conflict due to 4.19 missing the above commit
and ffedeeb780dc ("linkage: Introduce new macros for assembler
symbols") which also first landed in v5.5-rc1 but was backported to
linux-5.4.y as commit 840d8c9b3e5f ("linkage: Introduce new macros for
assembler symbols") which shipped in v5.4.76.

This patch fixes a build error from clang's assembler when building
with Clang-12, which now errors when symbols are redeclared with
different bindings.  We're using clang's assembler in Android and
ChromeOS for 4.19+.

Jiri, would you mind reviewing the 4.19 patch (or both)?  It simply
open codes what the upstream macros would expand to; this can be and
was observed from running:
$ make ... arch/x86/lib/memmove_64.s
(ie. lowercase s, to invoke the C preprocessor on the uppercase .S file)

See also: https://github.com/ClangBuiltLinux/linux/issues/1190.
-- 
Thanks,
~Nick Desaulniers