[Bro-Dev] Alignment check in RPC code

[Gregor Maier]

Hi,

it seems that the XDR extractor, which is used by the RPC code checks
the alignment of a memory buffer before extracting data.

uint32 extract_XDR_uint32(const u_char*& buf, int& len)
    {
    /* ... check that buf has enough len */

    uint32 bits32 = XDR_aligned(buf) ? *(uint32*) buf :
            ((buf[0] << 24) | (buf[1] << 16) | (buf[2] << 8) | buf[3]);

    buf += 4;
    len -= 4;

    return ntohl(bits32);
    }

inline int XDR_aligned(const u_char* buf)
    {
    return (((unsigned long) buf) & 0x3) == 0;
    }

However, on my Mac OS, buf it not 4-byte aligned. If this is the case
than the 32-bit value is byte-swapped (which is a bug, which makes the
testsuite fail on MAC OS X, which is why I discovered this code).

Mac OS X is fine with doing un-aligned reads. More general, with current
architectures and OSes, does one still need to check for 4- or 8-byte
alignments? If so, should this be done higher up in the Analyzer tree?
But my thought is that we can just remove the alignment check here.


cu
Gregor
-- 
Gregor Maier                                             gregor at icir.org
Int. Computer Science Institute (ICSI)          gregor at icsi.berkeley.edu
1947 Center St., Ste. 600                    http://www.icir.org/gregor/
Berkeley, CA 94704
USA