linux-user/elfload.c: byteswap function is not working when ELF is big endian

I run qemu-mipsel for ELF with mips MSB(big endian), it always outputs error message: Invalid ELF image for this architecture. For the ELF I run:

$file busybox

ELF 32-bit MSB  executable, MIPS, MIPS-I version 1 (SYSV), statically linked, stripped

The section header is not corrupted(MSB, corrputed section header table also outputs same error as above), when I run ELF with LSB, it works perfectly. I debugged with /linux-user/elfload.c, I am sure that the problem comes from byteswap function. But I don't know how to handle it. I really hope this can be fixed ASAP. Really appreciate your help.