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x86: gen_idt: fix some pylint issues

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Fixes some issues identified by pylint.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>
This commit is contained in:
Daniel Leung 2021-03-03 14:37:57 -08:00 • committed by Anas Nashif
commit 90722ad548
1 changed files with 31 additions and 21 deletions
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52
arch/x86/gen_gdt.py
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@ -39,26 +39,30 @@ import argparse
import sys
import struct
import os
import elftools
from distutils.version import LooseVersion
import elftools
from elftools.elf.elffile import ELFFile
from elftools.elf.sections import SymbolTableSection
if LooseVersion(elftools.__version__) < LooseVersion('0.24'):
sys.exit("pyelftools is out of date, need version 0.24 or later")
def debug(text):
if not args.verbose:
return
sys.stdout.write(os.path.basename(sys.argv[0]) + ": " + text + "\n")
"""Display debug message if --verbose"""
if args.verbose:
sys.stdout.write(os.path.basename(sys.argv[0]) + ": " + text + "\n")
def error(text):
"""Exit program with an error message"""
sys.exit(os.path.basename(sys.argv[0]) + ": " + text)
gdt_pd_fmt = "<HIH"
GDT_PD_FMT = "<HIH"
FLAGS_GRAN = 1 << 7 # page granularity
ACCESS_EX = 1 << 3 # executable
@ -70,14 +74,15 @@ ACCESS_RW = 1 << 1 # read or write permission
def create_gdt_pseudo_desc(addr, size):
"""Create pseudo GDT descriptor"""
debug("create pseudo decriptor: %x %x" % (addr, size))
# ...and take back one byte for the Intel god whose Ark this is...
size = size - 1
return struct.pack(gdt_pd_fmt, size, addr, 0)
return struct.pack(GDT_PD_FMT, size, addr, 0)
# Limit argument always in bytes
def chop_base_limit(base, limit):
"""Limit argument always in bytes"""
base_lo = base & 0xFFFF
base_mid = (base >> 16) & 0xFF
base_hi = (base >> 24) & 0xFF
@ -88,10 +93,11 @@ def chop_base_limit(base, limit):
return (base_lo, base_mid, base_hi, limit_lo, limit_hi)
gdt_ent_fmt = "<HHBBBB"
GDT_ENT_FMT = "<HHBBBB"
def create_code_data_entry(base, limit, dpl, flags, access):
"""Create GDT entry for code or data"""
debug("create code or data entry: %x %x %x %x %x" %
(base, limit, dpl, flags, access))
@ -115,11 +121,12 @@ def create_code_data_entry(base, limit, dpl, flags, access):
access = access | (present << 7) | (dpl << 5) | (desc_type << 4) | accessed
flags = flags | (size << 6) | limit_hi
return struct.pack(gdt_ent_fmt, limit_lo, base_lo, base_mid,
return struct.pack(GDT_ENT_FMT, limit_lo, base_lo, base_mid,
access, flags, base_hi)
def create_tss_entry(base, limit, dpl):
"""Create GDT TSS entry"""
debug("create TSS entry: %x %x %x" % (base, limit, dpl))
present = 1
@ -132,11 +139,12 @@ def create_tss_entry(base, limit, dpl):
flags = (gran << 7) | limit_hi
type_byte = ((present << 7) | (dpl << 5) | type_code)
return struct.pack(gdt_ent_fmt, limit_lo, base_lo, base_mid,
return struct.pack(GDT_ENT_FMT, limit_lo, base_lo, base_mid,
type_byte, flags, base_hi)
def get_symbols(obj):
"""Extract all symbols from ELF file object"""
for section in obj.iter_sections():
if isinstance(section, SymbolTableSection):
return {sym.name: sym.entry.st_value
@ -146,6 +154,7 @@ def get_symbols(obj):
def parse_args():
"""Parse command line arguments"""
global args
parser = argparse.ArgumentParser(
description=__doc__,
@ -163,10 +172,11 @@ def parse_args():
def main():
"""Main Program"""
parse_args()
with open(args.kernel, "rb") as fp:
kernel = ELFFile(fp)
with open(args.kernel, "rb") as elf_fp:
kernel = ELFFile(elf_fp)
syms = get_symbols(kernel)
# NOTE: use-cases are extremely limited; we always have a basic flat
@ -206,17 +216,17 @@ def main():
gdt_base = syms["_gdt"] + virt_to_phys_offset
with open(args.output_gdt, "wb") as fp:
with open(args.output_gdt, "wb") as output_fp:
# The pseudo descriptor is stuffed into the NULL descriptor
# since the CPU never looks at it
fp.write(create_gdt_pseudo_desc(gdt_base, num_entries * 8))
output_fp.write(create_gdt_pseudo_desc(gdt_base, num_entries * 8))
# Selector 0x08: code descriptor
fp.write(create_code_data_entry(0, 0xFFFFF, 0,
output_fp.write(create_code_data_entry(0, 0xFFFFF, 0,
FLAGS_GRAN, ACCESS_EX | ACCESS_RW))
# Selector 0x10: data descriptor
fp.write(create_code_data_entry(0, 0xFFFFF, 0,
output_fp.write(create_code_data_entry(0, 0xFFFFF, 0,
FLAGS_GRAN, ACCESS_RW))
if num_entries >= 5:
@ -224,18 +234,18 @@ def main():
df_tss = syms["_df_tss"] + virt_to_phys_offset
# Selector 0x18: main TSS
fp.write(create_tss_entry(main_tss, 0x67, 0))
output_fp.write(create_tss_entry(main_tss, 0x67, 0))
# Selector 0x20: double-fault TSS
fp.write(create_tss_entry(df_tss, 0x67, 0))
output_fp.write(create_tss_entry(df_tss, 0x67, 0))
if num_entries >= 7:
# Selector 0x28: code descriptor, dpl = 3
fp.write(create_code_data_entry(0, 0xFFFFF, 3,
output_fp.write(create_code_data_entry(0, 0xFFFFF, 3,
FLAGS_GRAN, ACCESS_EX | ACCESS_RW))
# Selector 0x30: data descriptor, dpl = 3
fp.write(create_code_data_entry(0, 0xFFFFF, 3,
output_fp.write(create_code_data_entry(0, 0xFFFFF, 3,
FLAGS_GRAN, ACCESS_RW))
if use_tls:
@ -244,7 +254,7 @@ def main():
#
# for use with thread local storage while this will be
# modified at runtime.
fp.write(create_code_data_entry(0, 0xFFFFF, 3,
output_fp.write(create_code_data_entry(0, 0xFFFFF, 3,
FLAGS_GRAN, ACCESS_RW))