x86, lto: Enable Clang LTO for 32-bit as well

Commit b33fff07e3e3 ("x86, build: allow LTO to be selected") enabled
support for LTO for x86_64 but 32-bit works fine as well.

I tested the following config combinations:

* i386_defconfig + CONFIG_LTO_CLANG_FULL=y

* i386_defconfig + CONFIG_LTO_CLANG_THIN=y

* ARCH=i386 allmodconfig + CONFIG_LTO_CLANG_THIN=y

with LLVM 11.1.0, 12.0.0, and 13.0.0 from git without any build
failures. The defconfigs boot in QEMU with no new warnings.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210429232611.3966964-1-nathan@kernel.org

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 0045e1b..12fa0d7 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -103,8 +103,8 @@ config X86
        select ARCH_SUPPORTS_DEBUG_PAGEALLOC
        select ARCH_SUPPORTS_NUMA_BALANCING     if X86_64
        select ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP       if NR_CPUS <= 4096
-       select ARCH_SUPPORTS_LTO_CLANG          if X86_64
-       select ARCH_SUPPORTS_LTO_CLANG_THIN     if X86_64
+       select ARCH_SUPPORTS_LTO_CLANG
+       select ARCH_SUPPORTS_LTO_CLANG_THIN
        select ARCH_USE_BUILTIN_BSWAP
        select ARCH_USE_MEMTEST
        select ARCH_USE_QUEUED_RWLOCKS