Re: [PATCH 12/12] efi: make const array 'apple' static

From: Ingo Molnar
Date: Fri Mar 09 2018 - 02:47:30 EST



* Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote:

> From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
>
> Don't populate the const read-only array 'buf' on the stack but instead
> make it static. Makes the object code smaller by 64 bytes:
>
> Before:
> text data bss dec hex filename
> 9264 1 16 9281 2441 arch/x86/boot/compressed/eboot.o
>
> After:
> text data bss dec hex filename
> 9200 1 16 9217 2401 arch/x86/boot/compressed/eboot.o
>
> (gcc version 7.2.0 x86_64)
>
> Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> ---
> arch/x86/boot/compressed/eboot.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
> index 886a9115af62..f2251c1c9853 100644
> --- a/arch/x86/boot/compressed/eboot.c
> +++ b/arch/x86/boot/compressed/eboot.c
> @@ -423,7 +423,7 @@ static void retrieve_apple_device_properties(struct boot_params *boot_params)
>
> static void setup_quirks(struct boot_params *boot_params)
> {
> - efi_char16_t const apple[] = { 'A', 'p', 'p', 'l', 'e', 0 };
> + static efi_char16_t const apple[] = { 'A', 'p', 'p', 'l', 'e', 0 };
> efi_char16_t *fw_vendor = (efi_char16_t *)(unsigned long)
> efi_table_attr(efi_system_table, fw_vendor, sys_table);

As a general policy, please don't put 'static' variables into the local scope,
use file scope instead - right before setup_quirks() would be fine.

This makes it abundantly clear that it's not on the stack.

Also, would it make sense to rename it to something more descriptive like
"apple_unicode_str[]" or so?

Plus an unicode string literal initializer would be pretty descriptive as well,
instead of the weird looking character array, i.e. something like:

static efi_char16_t const apple_unicode_str[] = u"Apple";

... or so?

Thanks,

Ingo