[PATCH 1/2] Makefile: enable --gc-sections

[Bin Meng]

On Sat, Aug 24, 2024 at 4:19 PM Kele Zhang <1952088712 at qq.com> wrote:
>
> The --gc-sections option enables the linker to perform garbage
> collection of unreferenced code and data, thereby reducing the binary
> size.
>
> The -ffunction-sections option will place each function into a separate
> section, so it is necessary to add .text.* to the linker script.
>
> Signed-off-by: Kele Zhang <1952088712 at qq.com>
> Signed-off-by: Yuan Tan <tanyuan at tinylab.org>
> Signed-off-by: Zhangjin Wu <falcon at tinylab.org>
> ---
>  Makefile                    | 4 ++--
>  firmware/fw_base.ldS        | 1 +
>  firmware/fw_payload.elf.ldS | 2 +-
>  3 files changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/Makefile b/Makefile
> index 9c7fd4d..9abea9f 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -346,9 +346,9 @@ GENFLAGS    +=      $(libsbiutils-genflags-y)
>  GENFLAGS       +=      $(platform-genflags-y)
>  GENFLAGS       +=      $(firmware-genflags-y)
>
> -CFLAGS         =       -g -Wall -Werror -ffreestanding -nostdlib -fno-stack-protector -fno-strict-aliasing
> +CFLAGS         =       -g -Wall -Werror -ffreestanding -nostdlib -fno-stack-protector -fno-strict-aliasing -ffunction-sections -fdata-sections -Wl,--gc-sections

--gc-sections should be put in the ELFFLAGS

>  ifneq ($(DEBUG),)
> -CFLAGS         +=      -O0
> +CFLAGS         +=      -O0 -Wl,--print-gc-sections
>  else
>  CFLAGS         +=      -O2
>  endif
> diff --git a/firmware/fw_base.ldS b/firmware/fw_base.ldS
> index fb47984..a33746a 100644
> --- a/firmware/fw_base.ldS
> +++ b/firmware/fw_base.ldS
> @@ -20,6 +20,7 @@
>                 PROVIDE(_text_start = .);
>                 *(.entry)
>                 *(.text)
> +               *(.text.*)
>                 . = ALIGN(8);
>                 PROVIDE(_text_end = .);
>         }
> diff --git a/firmware/fw_payload.elf.ldS b/firmware/fw_payload.elf.ldS
> index f1a544b..4e1f011 100644
> --- a/firmware/fw_payload.elf.ldS
> +++ b/firmware/fw_payload.elf.ldS
> @@ -23,7 +23,7 @@ SECTIONS
>         .payload :
>         {
>                 PROVIDE(_payload_start = .);
> -               *(.payload)
> +               KEEP(*(.payload))
>                 . = ALIGN(8);
>                 PROVIDE(_payload_end = .);
>         }
> --

Regards,
Bin