Re: [PATCH qemu v2 2/2] m68k: align bootinfo strings and data to 4 bytes

[Laurent Vivier <laurent@vivier.eu>]

Le 26/09/2022 à 13:39, Jason A. Donenfeld a écrit :
> Various tools, such as kexec-tools and m68k-bootinfo, expect each
> bootinfo entry to be aligned to 4 bytes, not 2 bytes. So adjust the
> padding to fill this out as such.

Agree, I found the same problem using petitboot as a ROM for the virt machine [1].
(I didn't update BOOTINFOSTR() but I think I should).

Reviewed-by: Laurent Vivier <laurent@vivier.eu>

[1] https://github.com/vivier/qemu-m68k/commits/m68k-virt
> 
> Also, break apart the padding additions from the other field length
> additions, so that it's more clear why these magic numbers are being
> added, and comment them too.
> 
> Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Cc: Laurent Vivier <laurent@vivier.eu>
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
> ---
>   hw/m68k/bootinfo.h | 10 ++++++----
>   1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/m68k/bootinfo.h b/hw/m68k/bootinfo.h
> index bd8b212fd3..897162b818 100644
> --- a/hw/m68k/bootinfo.h
> +++ b/hw/m68k/bootinfo.h
> @@ -48,13 +48,14 @@
>           stw_phys(as, base, id); \
>           base += 2; \
>           stw_phys(as, base, \
> -                 (sizeof(struct bi_record) + strlen(string) + 2) & ~1); \
> +                 (sizeof(struct bi_record) + strlen(string) + \
> +                  1 /* null termination */ + 3 /* padding */) & ~3); \
>           base += 2; \
>           for (i = 0; string[i]; i++) { \
>               stb_phys(as, base++, string[i]); \
>           } \
>           stb_phys(as, base++, 0); \
> -        base = (base + 1) & ~1; \
> +        base = (base + 3) & ~3; \
>       } while (0)
>   
>   #define BOOTINFODATA(as, base, id, data, len) \
> @@ -63,13 +64,14 @@
>           stw_phys(as, base, id); \
>           base += 2; \
>           stw_phys(as, base, \
> -                 (sizeof(struct bi_record) + len + 3) & ~1); \
> +                 (sizeof(struct bi_record) + len + \
> +                  2 /* length field */ + 3 /* padding */) & ~3); \
>           base += 2; \
>           stw_phys(as, base, len); \
>           base += 2; \
>           for (i = 0; i < len; ++i) { \
>               stb_phys(as, base++, data[i]); \
>           } \
> -        base = (base + 1) & ~1; \
> +        base = (base + 3) & ~3; \
>       } while (0)
>   #endif