#!/usr/bin/env python3
"""sbl_mains.py — кандидаты в sbl_main: плотность BL + близость строк boot-лога.
Использование: ./tools/sbl_mains.py fw/sbl/img0.elf
"""
import struct
import sys

d = open(sys.argv[1], "rb").read()
phoff = struct.unpack("<I", d[28:32])[0]
phnum = struct.unpack("<H", d[44:46])[0]
segs = []
for k in range(phnum):
    p = d[phoff + k * 32:phoff + (k + 1) * 32]
    t, off, v, pa, fsz, msz, fl, al = struct.unpack("<IIIIIIII", p)
    if t == 1 and fsz:
        segs.append((off, v, fsz))

# prologues: STMDB sp!,{...,lr} (bit11 set)
cands = []
for off, v, sz in segs:
    code = d[off:off + sz]
    for j in range(0, len(code) - 4, 4):
        x = struct.unpack("<I", code[j:j + 4])[0]
        if (x & 0xFFFF0000) == 0xE92D0000:  # push ... r11?/lr frame
            # count BLs in next 2KB
            bls = 0
            for q in range(j, min(j + 2048, len(code) - 4), 4):
                y = struct.unpack("<I", code[q:q + 4])[0]
                if (y >> 25) == 0b101 and (y & 0x01000000):
                    bls += 1
            if bls >= 8:
                cands.append((bls, v + j))
cands.sort(reverse=True)
print("top candidates (bl-count, addr):")
for bls, a in cands[:15]:
    print(f"  {bls:3d}  {a:#x}")