exidx-count.py

import os, sys, struct, subprocess
READELF = os.getenv("READELF") or "readelf"

def main(argv):
    filename = argv[1]
    phdrs = subprocess.Popen([READELF, "-l", filename], 
                             stdout = subprocess.PIPE, stderr = sys.stderr)
    offset = None
    fsize = None
    for line in phdrs.stdout:
        fields = line.split()
        if len(fields) > 0 and fields[0] == "EXIDX":
            offset = int(fields[1], 16)
            fsize = int(fields[4], 16)
    phdrs.wait()
    if phdrs.returncode != 0:
        raise Exception("readelf failed")
    if not offset:
        raise Exception("No EXIDX phdr found")
    progs = {}
    refs = {}
    print ("%u exidx entries" % (fsize / 8))
    with open(filename, "rb") as fh:
        fh.seek(offset)
        for n in xrange(0, fsize / 8):
            (pcoff, exidx) = struct.unpack("<LL", fh.read(8))
            if exidx == 1:
                progs[None] = progs.get(None, 0) + 1
            elif exidx & 0x80000000:
                prog = struct.pack("<L", exidx)
                progs[prog] = progs.get(prog, 0) + 1
            else:
                rel31 = exidx | -(exidx & 0x40000000)
                ref = rel31 + offset + 8 * n + 4
                refs[ref] = refs.get(ref, 0) + 1
        print ("%u unwinders stored in exidx + %u extab refs" % (len(progs), len(refs)))
        for ref in refs:
            fh.seek(ref)
            buf = fh.read(4)
            (hdr,) = struct.unpack("<L", buf)
            if hdr >> 24 == 0x81:
                words = (hdr >> 16) & 0xff
            elif hdr >> 24 == 0x82:
                words = hdr & 0xffffff
            else:
                raise Exception("Unhandled personality %x offset %d" % (hdr, ref))
            buf += fh.read(4 * words)
            progs[buf] = progs.get(buf, 0) + refs[ref]
        print ("%u total unwinders" % (len(progs)))
    

if __name__ == '__main__':
    main(sys.argv)