Re: [Qemu-devel] [PATCH 2/2] linux-user: SOCK_PACKET uses network endian to encode protocol in socket()

[Laurent Vivier <Laurent@vivier.eu>]

Le mardi 01 janvier 2013 à 18:27 +0100, Laurent Vivier a écrit :
> Le mardi 01 janvier 2013 à 15:03 +0000, Peter Maydell a écrit :
> > On 31 December 2012 22:19, Laurent Vivier <Laurent@vivier.eu> wrote:
> > > works... sometime. In fact, work if target endianess is network endianess.
> > >
> > > Correct me if I'm wrong.
> > >
> > > target          host
> > > little endian / big endian
> > >
> > > memory   00 00 00 03
> > 
> > Syscall arguments aren't generally passed in memory, they're
> > in registers (and if they were pased in memory for some architecture
> > then that arch would do a load-and-swap-from-memory in main.c).
> > So the value you see in do_socket() is always "the integer passed
> > as a syscall parameter, as a host-order integer".
> 
> Yes, I missed that.

But, in fact, for socketcall(), they are read from memory :

        static abi_long do_socketcall(int num, abi_ulong vptr)
        {
            abi_long ret;
            const int n = sizeof(abi_ulong);
        
            switch(num) {
            case SOCKOP_socket:
                {
                    abi_ulong domain, type, protocol;
        
                    if (get_user_ual(domain, vptr)
                        || get_user_ual(type, vptr + n)
                        || get_user_ual(protocol, vptr + 2 * n))
                        return -TARGET_EFAULT;
        
                    ret = do_socket(domain, type, protocol);
                }
                break;


So, I don't know if "tswap16()" is always correct. It works for
m68k-to-x86_64, but I don't understand how it can works for
i386-to-i386.

Your opinion ?

Regards,
Laurent

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