On Tuesday, 24 March 2015 14:08:25 UTC+11, jcea wrote:
>
> On 23/03/15 02:13, Graham Dumpleton wrote:
> > My memory is that truss allows you to specify certain system
> > functions which you want verbose display of arguments and return
> > value.
> >
> > From memory:
> >
> > -v writev
> >
> > Can you see if you can get extra information that way about the
> > arguments?
>
> [root@babylon5 /]# truss -t writev -v writev -p 29939 29940
>
> """
> /12: writev(10, 0x08146010, 76) Err#22 EINVAL
> /12: iov_base = 0xFE155AB8 iov_len = 4
> /12: iov_base = 0xFE155ABC iov_len = 4
> /12: iov_base = 0x080B3A7B iov_len = 18
> /12: iov_base = 0x080B3A73 iov_len = 8
> /12: iov_base = 0x080B3A8D iov_len = 16
> /12: iov_base = 0x08144F28 iov_len = 9
> /12: iov_base = 0x080B3A9D iov_len = 15
> /12: iov_base = 0x08144F08 iov_len = 4
> /12: iov_base = 0x080B3A4B iov_len = 13
> /12: iov_base = 0x080B2628 iov_len = 1
> /12: iov_base = 0x080B3AAC iov_len = 12
> /12: iov_base = 0x081455C0 iov_len = 2
> /12: iov_base = 0x080B3AB8 iov_len = 12
> /12: iov_base = 0x081459C0 iov_len = 2
> /12: iov_base = 0x080B3944 iov_len = 5
> /12: iov_base = 0x08145810 iov_len = 226
> /12: writev(9, 0xFE155E30, 2) = 750
> /12: iov_base = 0x08148028 iov_len = 219
> /12: iov_base = 0x08142010 iov_len = 531
> """
>
> Are those two first values, in the "0xFExxxxxx" range, normal?.
>
They are integers giving a length and location is on the stack, so likely
okay.
vec[1].iov_base = (void*)&count;
vec[1].iov_len = sizeof(count);
total += vec[1].iov_len;
vec[0].iov_base = (void*)&total;
vec[0].iov_len = sizeof(total);
rv = wsgi_socket_sendv(daemon->socket, vec, (int)(vec_next-vec));
There shouldn't be a restriction on using stack memory.
Thanks for the details. Will think over what this tells me.
> The content of those memory areas looks weird. With GDB:
>
> """
> (gdb) x/1xw 0xFE155AB8
> 0xfe155ab8: 0xfe155ad8
> (gdb) x/1xw 0xFE155ABC
> 0xfe155abc: 0xfed7720b
> """
>
> The rest of the IOVEC looks good, with content like:
>
> "GATEWAY_INTERFACE"
> "CGI/1.1"
>
>
>
>
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