Re: [PATCH qemu 1/2] Don't reverse bFLT endianess when not needed

[Laurent Vivier <laurent@vivier.eu>]

Le 16/07/2025 à 21:24, ~wojtekka a écrit :
> From: Wojtek Kaniewski <wojtekka@toxygen.net>
> 
> bFLT format is big-endian. get_user_ual() returns host value so for
> little-endian target and little-endian host it's necessary to reverse
> words using ntohl(). For big-endian targets we end up with incorrect
> endianess:
> 
>      $ qemu-m68k-static ./test
>      BINFMT_FLAT: reloc outside program 0x801f0000 (0 - 0x41f0/0x1e40)
>      Aborted (core dumped)
> 
> For comparison the output of `flthdr` follows:
> 
>      $ m68k-elf-flthdr -P ./test
>      ./test
>          Magic:        bFLT
>          Rev:          4
>          Build Date:   Tue Jul 15 23:02:00 2025
>          Entry:        0x44
>          Data Start:   0x1e80
>          Data End:     0x205c
>          BSS End:      0x40a0
>          Stack Size:   0x1000
>          Reloc Start:  0x205c
>          Reloc Count:  0x17
>          Flags:        0x2 ( Has-PIC-GOT )
>          Relocs:
>          #	reloc      (  address )	data
>          0	0x00001f80 (0x00001f80)	3c200000
>                    ^^^^^^^^
>          1	0x00001f84 (0x00001f84)	3c300000
>          2	0x00001f88 (0x00001f88)	3c200000
>          ...
> 
> Signed-off-by: Wojtek Kaniewski <wojtekka@toxygen.net>
> ---
>   linux-user/flatload.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/linux-user/flatload.c b/linux-user/flatload.c
> index 4beb3ed1b9..afaff4ac44 100644
> --- a/linux-user/flatload.c
> +++ b/linux-user/flatload.c
> @@ -413,7 +413,9 @@ static int load_flat_file(struct linux_binprm * bprm,
>                  relocated first).  */
>               if (get_user_ual(relval, reloc + i * sizeof(abi_ulong)))
>                   return -EFAULT;
> +#if !TARGET_BIG_ENDIAN
>               relval = ntohl(relval);
> +#endif
>               if (flat_set_persistent(relval, &persistent))
>                   continue;
>               addr = flat_get_relocate_addr(relval);

I think the ntohl() should be removed totally and flat_set_persistent() 
should use put_user_ual().

Could you test this?

Thanks,
Laurent