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Atmosphere/mesosphere/build_mesosphere.py
Michael Scire cfc54dbc88 kern: put rela in bss (EXPERIMENTAL)
NOTE: This does some really gross things. It saves ~0x4000 of space, but
at the cost of crimes against the linker script. We should consider/evaluate
whether this is worth doing for real.
2021-10-08 12:32:35 -07:00

82 lines
2.9 KiB
Python

#!/usr/bin/env python
import sys, os
from struct import pack as pk, unpack as up
def atmosphere_target_firmware(major, minor, micro, rev = 0):
return (major << 24) | (minor << 16) | (micro << 8) | rev
def align_up(val, algn):
val += algn - 1
return val - (val % algn)
def find_rela(kernel, dynamic):
rela_offset, rela_size = (None, None)
while True:
dyn_type, dyn_val = up('<QQ', kernel[dynamic:dynamic+0x10])
if dyn_type == 0:
break
elif dyn_type == 7:
assert (rela_offset is None)
rela_offset = dyn_val
elif dyn_type == 8:
assert (rela_size is None)
rela_size = dyn_val
dynamic += 0x10
assert (rela_offset is not None)
assert (rela_size is not None)
return (rela_offset, rela_size)
def main(argc, argv):
if argc != 4:
print('Usage: %s kernel_ldr.bin kernel.bin output.bin' % argv[0])
return 1
with open(argv[1], 'rb') as f:
kernel_ldr = f.read()
with open(argv[2], 'rb') as f:
kernel = f.read()
kernel_metadata_offset = 4
assert (kernel_metadata_offset <= len(kernel) - 0x40)
assert (kernel[kernel_metadata_offset:kernel_metadata_offset + 4] == b'MSS0')
bss_start, bss_end, kernel_end, dynamic = up('<IIII', kernel[kernel_metadata_offset + 0x30:kernel_metadata_offset + 0x40])
assert (bss_end >= bss_start)
bss_size = bss_end - bss_start
assert (bss_end == kernel_end)
assert (kernel_end <= len(kernel))
rela_offset, rela_size = find_rela(kernel, dynamic)
assert (rela_size == len(kernel) - kernel_end)
assert (bss_start <= rela_offset and rela_offset + rela_size <= bss_end)
assert (kernel[bss_start:bss_end] == (b'\x00'* bss_size))
kernel = kernel[:rela_offset] + kernel[bss_end:] + (b'\x00' * (bss_size - (rela_size + (rela_offset - bss_start))))
assert (kernel_end == len(kernel))
embedded_ini = b''
try:
with open('ini.bin', 'rb') as f:
embedded_ini = f.read()
except:
pass
embedded_ini_offset = align_up(kernel_end, 0x1000)
embedded_ini_end = embedded_ini_offset + len(embedded_ini) # TODO: Create and embed an INI, eventually.
kernel_ldr_offset = align_up(embedded_ini_end, 0x1000) + (0x1000 if len(embedded_ini) == 0 else 0)
kernel_ldr_end = kernel_ldr_offset + len(kernel_ldr)
mesosphere_end = align_up(kernel_ldr_end, 0x1000)
with open(argv[3], 'wb') as f:
f.write(kernel[:kernel_metadata_offset + 4])
f.write(pk('<QQI', embedded_ini_offset, kernel_ldr_offset, atmosphere_target_firmware(13, 0, 0)))
f.write(kernel[kernel_metadata_offset + 0x18:])
f.seek(embedded_ini_offset)
f.write(embedded_ini)
f.seek(embedded_ini_end)
f.seek(kernel_ldr_offset)
f.write(kernel_ldr)
f.seek(mesosphere_end)
f.write(b'\x00'*0x1000)
return 0
if __name__ == '__main__':
sys.exit(main(len(sys.argv), sys.argv))