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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 sys
import struct import struct
import os import os
import elftools
from distutils.version import LooseVersion from distutils.version import LooseVersion
import elftools
from elftools.elf.elffile import ELFFile from elftools.elf.elffile import ELFFile
from elftools.elf.sections import SymbolTableSection from elftools.elf.sections import SymbolTableSection
if LooseVersion(elftools.__version__) < LooseVersion('0.24'): if LooseVersion(elftools.__version__) < LooseVersion('0.24'):
sys.exit("pyelftools is out of date, need version 0.24 or later") sys.exit("pyelftools is out of date, need version 0.24 or later")
def debug(text): def debug(text):
if not args.verbose: """Display debug message if --verbose"""
return if args.verbose:
sys.stdout.write(os.path.basename(sys.argv[0]) + ": " + text + "\n") sys.stdout.write(os.path.basename(sys.argv[0]) + ": " + text + "\n")
def error(text): def error(text):
"""Exit program with an error message"""
sys.exit(os.path.basename(sys.argv[0]) + ": " + text) sys.exit(os.path.basename(sys.argv[0]) + ": " + text)
gdt_pd_fmt = "<HIH" GDT_PD_FMT = "<HIH"
FLAGS_GRAN = 1 << 7 # page granularity FLAGS_GRAN = 1 << 7 # page granularity
ACCESS_EX = 1 << 3 # executable ACCESS_EX = 1 << 3 # executable
@ -70,14 +74,15 @@ ACCESS_RW = 1 << 1 # read or write permission
def create_gdt_pseudo_desc(addr, size): def create_gdt_pseudo_desc(addr, size):
"""Create pseudo GDT descriptor"""
debug("create pseudo decriptor: %x %x" % (addr, size)) debug("create pseudo decriptor: %x %x" % (addr, size))
# ...and take back one byte for the Intel god whose Ark this is... # ...and take back one byte for the Intel god whose Ark this is...
size = size - 1 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): def chop_base_limit(base, limit):
"""Limit argument always in bytes"""
base_lo = base & 0xFFFF base_lo = base & 0xFFFF
base_mid = (base >> 16) & 0xFF base_mid = (base >> 16) & 0xFF
base_hi = (base >> 24) & 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) 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): 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" % debug("create code or data entry: %x %x %x %x %x" %
(base, limit, dpl, flags, access)) (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 access = access | (present << 7) | (dpl << 5) | (desc_type << 4) | accessed
flags = flags | (size << 6) | limit_hi 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) access, flags, base_hi)
def create_tss_entry(base, limit, dpl): def create_tss_entry(base, limit, dpl):
"""Create GDT TSS entry"""
debug("create TSS entry: %x %x %x" % (base, limit, dpl)) debug("create TSS entry: %x %x %x" % (base, limit, dpl))
present = 1 present = 1
@ -132,11 +139,12 @@ def create_tss_entry(base, limit, dpl):
flags = (gran << 7) | limit_hi flags = (gran << 7) | limit_hi
type_byte = ((present << 7) | (dpl << 5) | type_code) 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) type_byte, flags, base_hi)
def get_symbols(obj): def get_symbols(obj):
"""Extract all symbols from ELF file object"""
for section in obj.iter_sections(): for section in obj.iter_sections():
if isinstance(section, SymbolTableSection): if isinstance(section, SymbolTableSection):
return {sym.name: sym.entry.st_value return {sym.name: sym.entry.st_value
@ -146,6 +154,7 @@ def get_symbols(obj):
def parse_args(): def parse_args():
"""Parse command line arguments"""
global args global args
parser = argparse.ArgumentParser( parser = argparse.ArgumentParser(
description=__doc__, description=__doc__,
@ -163,10 +172,11 @@ def parse_args():
def main(): def main():
"""Main Program"""
parse_args() parse_args()
with open(args.kernel, "rb") as fp: with open(args.kernel, "rb") as elf_fp:
kernel = ELFFile(fp) kernel = ELFFile(elf_fp)
syms = get_symbols(kernel) syms = get_symbols(kernel)
# NOTE: use-cases are extremely limited; we always have a basic flat # 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 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 # The pseudo descriptor is stuffed into the NULL descriptor
# since the CPU never looks at it # 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 # 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)) FLAGS_GRAN, ACCESS_EX | ACCESS_RW))
# Selector 0x10: data descriptor # 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)) FLAGS_GRAN, ACCESS_RW))
if num_entries >= 5: if num_entries >= 5:
@ -224,18 +234,18 @@ def main():
df_tss = syms["_df_tss"] + virt_to_phys_offset df_tss = syms["_df_tss"] + virt_to_phys_offset
# Selector 0x18: main TSS # 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 # 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: if num_entries >= 7:
# Selector 0x28: code descriptor, dpl = 3 # 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)) FLAGS_GRAN, ACCESS_EX | ACCESS_RW))
# Selector 0x30: data descriptor, dpl = 3 # 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)) FLAGS_GRAN, ACCESS_RW))
if use_tls: if use_tls:
@ -244,7 +254,7 @@ def main():
# #
# for use with thread local storage while this will be # for use with thread local storage while this will be
# modified at runtime. # 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)) FLAGS_GRAN, ACCESS_RW))