kbuild: lto: merge module sections

commit dd2776222abb9893e5b5c237a2c8c880d8854cee upstream.

LLD always splits sections with LTO, which increases module sizes. This
change adds linker script rules to merge the split sections in the final
module.

Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20201211184633.3213045-6-samitolvanen@google.com
Cc: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/scripts/module.lds.S b/scripts/module.lds.S
index 69b9b71a6a4731ba43f74996039c5272ce2254c8..18d5b84236350cf59fc4361b34307f663496be52 100644 (file)
--- a/scripts/module.lds.S
+++ b/scripts/module.lds.S
@@ -23,6 +23,30 @@ SECTIONS {
        .init_array             0 : ALIGN(8) { *(SORT(.init_array.*)) *(.init_array) }
 
        __jump_table            0 : ALIGN(8) { KEEP(*(__jump_table)) }
+
+       __patchable_function_entries : { *(__patchable_function_entries) }
+
+       /*
+        * With CONFIG_LTO_CLANG, LLD always enables -fdata-sections and
+        * -ffunction-sections, which increases the size of the final module.
+        * Merge the split sections in the final binary.
+        */
+       .bss : {
+               *(.bss .bss.[0-9a-zA-Z_]*)
+               *(.bss..L*)
+       }
+
+       .data : {
+               *(.data .data.[0-9a-zA-Z_]*)
+               *(.data..L*)
+       }
+
+       .rodata : {
+               *(.rodata .rodata.[0-9a-zA-Z_]*)
+               *(.rodata..L*)
+       }
+
+       .text : { *(.text .text.[0-9a-zA-Z_]*) }
 }
 
 /* bring in arch-specific sections */