blob: 77d5ca1f915ca017b848840610eca748c55ae218 [file] [log] [blame]
#!/usr/bin/env python3
# Copyright (c) 2020 Intel Corporation
# SPDX-License-Identifier: Apache-2.0
"""Create the kernel's page tables for x86 CPUs.
For additional detail on paging and x86 memory management, please
consult the IA Architecture SW Developer Manual, volume 3a, chapter 4.
This script produces the initial page tables installed into the CPU
at early boot. These pages will have an identity mapping of the kernel
image. The script takes the 'zephyr_prebuilt.elf' as input to obtain region
sizes, certain memory addresses, and configuration values.
If CONFIG_SRAM_REGION_PERMISSIONS is not enabled, the kernel image will be
mapped with the Present and Write bits set. The linker scripts shouldn't
add page alignment padding between sections.
If CONFIG_SRAM_REGION_PERMISSIONS is enabled, the access permissions
- By default, the Present, Write, and Execute Disable bits are
- The __text_region region will have Present and User bits set
- The __rodata_region region will have Present, User, and Execute
Disable bits set
- On x86_64, the _locore region will have Present set and
the _lorodata region will have Present and Execute Disable set.
This script will establish a dual mapping at the address defined by
- The double-mapping is used to transition the
instruction pointer from a physical address at early boot to the
virtual address where the kernel is actually linked.
- The mapping is always double-mapped at the top-level paging structure
and the physical/virtual base addresses must have the same alignment
with respect to the scope of top-level paging structure entries.
This allows the same second-level paging structure(s) to be used for
both memory bases.
- The double-mapping is needed so that we can still fetch instructions
from identity-mapped physical addresses after we program this table
into the MMU, then jump to the equivalent virtual address.
The kernel then unlinks the identity mapping before continuing,
the address space is purely virtual after that.
Because the set of page tables are linked together by physical address,
we must know a priori the physical address of each table. The linker
script must define a z_x86_pagetables_start symbol where the page
tables will be placed, and this memory address must not shift between
prebuilt and final ELF builds. This script will not work on systems
where the physical load address of the kernel is unknown at build time.
64-bit systems will always build IA-32e page tables. 32-bit systems
build PAE page tables if CONFIG_X86_PAE is set, otherwise standard
32-bit page tables are built.
The kernel will expect to find the top-level structure of the produced
page tables at the physical address corresponding to the symbol
z_x86_kernel_ptables. The linker script will need to set that symbol
to the end of the binary produced by this script, minus the size of the
top-level paging structure as it is written out last.
import sys
import array
import argparse
import ctypes
import os
import struct
import re
import textwrap
from packaging import version
import elftools
from elftools.elf.elffile import ELFFile
from elftools.elf.sections import SymbolTableSection
if version.parse(elftools.__version__) < version.parse('0.24'):
sys.exit("pyelftools is out of date, need version 0.24 or later")
def bit(pos):
"""Get value by shifting 1 by pos"""
return 1 << pos
# Page table entry flags
FLAG_P = bit(0)
FLAG_RW = bit(1)
FLAG_US = bit(2)
FLAG_CD = bit(4)
FLAG_SZ = bit(7)
FLAG_G = bit(8)
FLAG_XD = bit(63)
FLAG_IGNORED0 = bit(9)
FLAG_IGNORED1 = bit(10)
FLAG_IGNORED2 = bit(11)
# PD_LEVEL and PT_LEVEL are used as list index to PtableSet.levels[]
# to get table from back of list.
def debug(text):
"""Display verbose debug message"""
if not args.verbose:
sys.stdout.write(os.path.basename(sys.argv[0]) + ": " + text + "\n")
def verbose(text):
"""Display --verbose --verbose message"""
if args.verbose and args.verbose > 1:
sys.stdout.write(os.path.basename(sys.argv[0]) + ": " + text + "\n")
def error(text):
"""Display error message and exit program"""
sys.exit(os.path.basename(sys.argv[0]) + ": " + text)
def align_check(base, size, scope=4096):
"""Make sure base and size are page-aligned"""
if (base % scope) != 0:
error("unaligned base address %x" % base)
if (size % scope) != 0:
error("Unaligned region size 0x%x for base %x" % (size, base))
def dump_flags(flags):
"""Translate page table flags into string"""
ret = ""
if flags & FLAG_P:
ret += "P "
if flags & FLAG_RW:
ret += "RW "
if flags & FLAG_US:
ret += "US "
if flags & FLAG_G:
ret += "G "
if flags & FLAG_XD:
ret += "XD "
if flags & FLAG_SZ:
ret += "SZ "
if flags & FLAG_CD:
ret += "CD "
return ret.strip()
def round_up(val, align):
"""Round up val to the next multiple of align"""
return (val + (align - 1)) & (~(align - 1))
def round_down(val, align):
"""Round down val to the previous multiple of align"""
return val & (~(align - 1))
# Hard-coded flags for intermediate paging levels. Permissive, we only control
# access or set caching properties at leaf levels.
class MMUTable():
"""Represents a particular table in a set of page tables, at any level"""
def __init__(self):
self.entries = array.array(self.type_code,
[0 for i in range(self.num_entries)])
def get_binary(self):
"""Return a bytearray representation of this table"""
# Always little-endian
ctype = "<" + self.type_code
entry_size = struct.calcsize(ctype)
ret = bytearray(entry_size * self.num_entries)
for i in range(self.num_entries):
struct.pack_into(ctype, ret, entry_size * i, self.entries[i])
return ret
def supported_flags(self):
"""Class property indicating what flag bits are supported"""
raise NotImplementedError()
def addr_shift(self):
"""Class property for how much to shift virtual addresses to obtain
the appropriate index in the table for it"""
raise NotImplementedError()
def addr_mask(self):
"""Mask to apply to an individual entry to get the physical address
raise NotImplementedError()
def type_code(self):
"""Struct packing letter code for table entries. Either I for
32-bit entries, or Q for PAE/IA-32e"""
raise NotImplementedError()
def num_entries(self):
"""Number of entries in the table. Varies by table type and paging
raise NotImplementedError()
def entry_index(self, virt_addr):
"""Get the index of the entry in this table that corresponds to the
provided virtual address"""
return (virt_addr >> self.addr_shift) & (self.num_entries - 1)
def has_entry(self, virt_addr):
"""Indicate whether an entry is present in this table for the provided
virtual address"""
index = self.entry_index(virt_addr)
return (self.entries[index] & FLAG_P) != 0
def lookup(self, virt_addr):
"""Look up the physical mapping for a virtual address.
If this is a leaf table, this is the physical address mapping. If not,
this is the physical address of the next level table"""
index = self.entry_index(virt_addr)
return self.entries[index] & self.addr_mask
def map(self, virt_addr, phys_addr, entry_flags):
"""For the table entry corresponding to the provided virtual address,
set the corresponding physical entry in the table. Unsupported flags
will be filtered out.
If this is a leaf table, this is the physical address mapping. If not,
this is the physical address of the next level table"""
index = self.entry_index(virt_addr)
verbose("%s: mapping 0x%x to 0x%x : %s" %
phys_addr, virt_addr, dump_flags(entry_flags)))
self.entries[index] = ((phys_addr & self.addr_mask) |
(entry_flags & self.supported_flags))
def set_perms(self, virt_addr, entry_flags):
""""For the table entry corresponding to the provided virtual address,
update just the flags, leaving the physical mapping alone.
Unsupported flags will be filtered out."""
index = self.entry_index(virt_addr)
verbose("%s: changing perm at 0x%x : %s" %
virt_addr, dump_flags(entry_flags)))
self.entries[index] = ((self.entries[index] & self.addr_mask) |
(entry_flags & self.supported_flags))
# Specific supported table types
class Pml4(MMUTable):
"""Page mapping level 4 for IA-32e"""
addr_shift = 39
addr_mask = 0x7FFFFFFFFFFFF000
type_code = 'Q'
num_entries = 512
supported_flags = INT_FLAGS
class Pdpt(MMUTable):
"""Page directory pointer table for IA-32e"""
addr_shift = 30
addr_mask = 0x7FFFFFFFFFFFF000
type_code = 'Q'
num_entries = 512
supported_flags = INT_FLAGS | FLAG_SZ | FLAG_CD
class PdptPAE(Pdpt):
"""Page directory pointer table for PAE"""
num_entries = 4
class Pd(MMUTable):
"""Page directory for 32-bit"""
addr_shift = 22
addr_mask = 0xFFFFF000
type_code = 'I'
num_entries = 1024
supported_flags = INT_FLAGS | FLAG_SZ | FLAG_CD
class PdXd(Pd):
"""Page directory for either PAE or IA-32e"""
addr_shift = 21
addr_mask = 0x7FFFFFFFFFFFF000
num_entries = 512
type_code = 'Q'
class Pt(MMUTable):
"""Page table for 32-bit"""
addr_shift = 12
addr_mask = 0xFFFFF000
type_code = 'I'
num_entries = 1024
supported_flags = (FLAG_P | FLAG_RW | FLAG_US | FLAG_G | FLAG_CD |
class PtXd(Pt):
"""Page table for either PAE or IA-32e"""
addr_mask = 0x07FFFFFFFFFFF000
type_code = 'Q'
num_entries = 512
supported_flags = (FLAG_P | FLAG_RW | FLAG_US | FLAG_G | FLAG_XD | FLAG_CD |
class PtableSet():
"""Represents a complete set of page tables for any paging mode"""
def __init__(self, pages_start):
"""Instantiate a set of page tables which will be located in the
image starting at the provided physical memory location"""
self.toplevel = self.levels[0]()
self.page_pos = pages_start
debug("%s starting at physical address 0x%x" %
(self.__class__.__name__, self.page_pos))
# Database of page table pages. Maps physical memory address to
# MMUTable objects, excluding the top-level table which is tracked
# separately. Starts out empty as we haven't mapped anything and
# the top-level table is tracked separately.
self.tables = {}
def get_new_mmutable_addr(self):
"""If we need to instantiate a new MMUTable, return a physical
address location for it"""
ret = self.page_pos
self.page_pos += 4096
return ret
def levels(self):
"""Class hierarchy of paging levels, with the first entry being
the toplevel table class, and the last entry always being
some kind of leaf page table class (Pt or PtXd)"""
raise NotImplementedError()
def is_mapped(self, virt_addr, level):
Return True if virt_addr has already been mapped.
level_from_last == 0 only searches leaf level page tables.
level_from_last == 1 searches both page directories and page tables.
table = self.toplevel
num_levels = len(self.levels) + level + 1
has_mapping = False
# Create and link up intermediate tables if necessary
for depth in range(0, num_levels):
# Create child table if needed
if table.has_entry(virt_addr):
if depth == num_levels:
has_mapping = True
table = self.tables[table.lookup(virt_addr)]
if has_mapping:
# pylint doesn't like break in the above if-block
return has_mapping
def is_region_mapped(self, virt_base, size, level=PT_LEVEL):
"""Find out if a region has been mapped"""
align_check(virt_base, size)
for vaddr in range(virt_base, virt_base + size, 4096):
if self.is_mapped(vaddr, level):
return True
return False
def new_child_table(self, table, virt_addr, depth):
"""Create a new child table"""
new_table_addr = self.get_new_mmutable_addr()
new_table = self.levels[depth]()
debug("new %s at physical addr 0x%x"
% (self.levels[depth].__name__, new_table_addr))
self.tables[new_table_addr] = new_table, new_table_addr, INT_FLAGS)
return new_table
def map_page(self, virt_addr, phys_addr, flags, reserve, level=PT_LEVEL):
"""Map a virtual address to a physical address in the page tables,
with provided access flags"""
table = self.toplevel
num_levels = len(self.levels) + level + 1
# Create and link up intermediate tables if necessary
for depth in range(1, num_levels):
# Create child table if needed
if not table.has_entry(virt_addr):
table = self.new_child_table(table, virt_addr, depth)
table = self.tables[table.lookup(virt_addr)]
# Set up entry in leaf page table
if not reserve:, phys_addr, flags)
def reserve(self, virt_base, size, to_level=PT_LEVEL):
"""Reserve page table space with already aligned virt_base and size"""
debug("Reserving paging structures for 0x%x (0x%x)" %
(virt_base, size))
align_check(virt_base, size)
# How much memory is covered by leaf page table
scope = 1 << self.levels[PD_LEVEL].addr_shift
if virt_base % scope != 0:
error("misaligned virtual address space, 0x%x not a multiple of 0x%x" %
(virt_base, scope))
for addr in range(virt_base, virt_base + size, scope):
self.map_page(addr, 0, 0, True, to_level)
def reserve_unaligned(self, virt_base, size, to_level=PT_LEVEL):
"""Reserve page table space with virt_base and size alignment"""
# How much memory is covered by leaf page table
scope = 1 << self.levels[PD_LEVEL].addr_shift
mem_start = round_down(virt_base, scope)
mem_end = round_up(virt_base + size, scope)
mem_size = mem_end - mem_start
self.reserve(mem_start, mem_size, to_level)
def map(self, phys_base, virt_base, size, flags, level=PT_LEVEL):
"""Map an address range in the page tables provided access flags.
If virt_base is None, identity mapping using phys_base is done.
is_identity_map = virt_base is None or virt_base == phys_base
if virt_base is None:
virt_base = phys_base
scope = 1 << self.levels[level].addr_shift
debug("Mapping 0x%x (0x%x) to 0x%x: %s" %
(phys_base, size, virt_base, dump_flags(flags)))
align_check(phys_base, size, scope)
align_check(virt_base, size, scope)
for paddr in range(phys_base, phys_base + size, scope):
if is_identity_map and paddr == 0 and level == PT_LEVEL:
# Never map the NULL page at page table level.
vaddr = virt_base + (paddr - phys_base)
self.map_page(vaddr, paddr, flags, False, level)
def identity_map_unaligned(self, phys_base, size, flags, level=PT_LEVEL):
"""Identity map a region of memory"""
scope = 1 << self.levels[level].addr_shift
phys_aligned_base = round_down(phys_base, scope)
phys_aligned_end = round_up(phys_base + size, scope)
phys_aligned_size = phys_aligned_end - phys_aligned_base, None, phys_aligned_size, flags, level)
def map_region(self, name, flags, virt_to_phys_offset, level=PT_LEVEL):
"""Map a named region"""
if not isdef(name + "_start"):
# Region may not exists
region_start = syms[name + "_start"]
region_end = syms[name + "_end"]
region_size = region_end - region_start
region_start_phys = region_start
if virt_to_phys_offset is not None:
region_start_phys += virt_to_phys_offset, region_start, region_size, flags, level)
def set_region_perms(self, name, flags, level=PT_LEVEL):
"""Set access permissions for a named region that is already mapped
The bounds of the region will be looked up in the symbol table
with _start and _size suffixes. The physical address mapping
is unchanged and this will not disturb any double-mapping."""
if not isdef(name + "_start"):
# Region may not exists
# Doesn't matter if this is a virtual address, we have a
# either dual mapping or it's the same as physical
base = syms[name + "_start"]
if isdef(name + "_size"):
size = syms[name + "_size"]
region_end = syms[name + "_end"]
size = region_end - base
if size == 0:
debug("change flags for %s at 0x%x (0x%x): %s" %
(name, base, size, dump_flags(flags)))
num_levels = len(self.levels) + level + 1
scope = 1 << self.levels[level].addr_shift
align_check(base, size, scope)
for addr in range(base, base + size, scope):
# Never map the NULL page
if addr == 0:
table = self.toplevel
for _ in range(1, num_levels):
table = self.tables[table.lookup(addr)]
table.set_perms(addr, flags)
except KeyError:
error("no mapping for %s region 0x%x (size 0x%x)" %
(name, base, size))
def write_output(self, filename):
"""Write the page tables to the output file in binary format"""
written_size = 0
with open(filename, "wb") as output_fp:
for addr in sorted(self.tables):
mmu_table = self.tables[addr]
mmu_table_bin = mmu_table.get_binary()
written_size += len(mmu_table_bin)
# We always have the top-level table be last. This is because
# in PAE, the top-level PDPT has only 4 entries and is not a
# full page in size. We do not put it in the tables dictionary
# and treat it as a special case.
debug("top-level %s at physical addr 0x%x" %
top_level_bin = self.toplevel.get_binary()
written_size += len(top_level_bin)
return written_size
# Paging mode classes, we'll use one depending on configuration
class Ptables32bit(PtableSet):
"""32-bit Page Tables"""
levels = [Pd, Pt]
class PtablesPAE(PtableSet):
"""PAE Page Tables"""
levels = [PdptPAE, PdXd, PtXd]
class PtablesIA32e(PtableSet):
"""Page Tables under IA32e mode"""
levels = [Pml4, Pdpt, PdXd, PtXd]
def parse_args():
"""Parse command line arguments"""
global args
parser = argparse.ArgumentParser(
parser.add_argument("-k", "--kernel", required=True,
help="path to prebuilt kernel ELF binary")
parser.add_argument("-o", "--output", required=True,
help="output file")
parser.add_argument("--map", action='append',
Map extra memory:
<physical address>,<size>[,<flags:LUWXD>[,<virtual address>]]
where flags can be empty or combination of:
L - Large page (2MB or 4MB),
U - Userspace accessible,
W - Writable,
X - Executable,
D - Cache disabled.
Default is
small (4KB) page,
supervisor only,
read only,
and execution disabled.
parser.add_argument("-v", "--verbose", action="count",
help="Print extra debugging information")
args = parser.parse_args()
if "VERBOSE" in os.environ:
args.verbose = 1
def get_symbols(elf_obj):
"""Get all symbols from the ELF file"""
for section in elf_obj.iter_sections():
if isinstance(section, SymbolTableSection):
return { sym.entry.st_value
for sym in section.iter_symbols()}
raise LookupError("Could not find symbol table")
def isdef(sym_name):
"""True if symbol is defined in ELF file"""
return sym_name in syms
def find_symbol(obj, name):
"""Find symbol object from ELF file"""
for section in obj.iter_sections():
if isinstance(section, SymbolTableSection):
for sym in section.iter_symbols():
if == name:
return sym
return None
def map_extra_regions(pt):
"""Map extra regions specified in command line"""
# Extract command line arguments
mappings = []
for entry in
elements = entry.split(',')
if len(elements) < 2:
error("Not enough arguments for --map %s" % entry)
one_map = {}
one_map['cmdline'] = entry
one_map['phys'] = int(elements[0], 0)
one_map['size']= int(elements[1], 0)
one_map['large_page'] = False
flags = FLAG_P | ENTRY_XD
if len(elements) > 2:
map_flags = elements[2]
# Check for allowed flags
if not bool(re.match('^[LUWXD]*$', map_flags)):
error("Unrecognized flags: %s" % map_flags)
flags = FLAG_P | ENTRY_XD
if 'W' in map_flags:
flags |= ENTRY_RW
if 'X' in map_flags:
flags &= ~ENTRY_XD
if 'U' in map_flags:
flags |= ENTRY_US
if 'L' in map_flags:
flags |= FLAG_SZ
one_map['large_page'] = True
if 'D' in map_flags:
flags |= FLAG_CD
one_map['flags'] = flags
if len(elements) > 3:
one_map['virt'] = int(elements[3], 16)
one_map['virt'] = one_map['phys']
# Map the regions
for one_map in mappings:
phys = one_map['phys']
size = one_map['size']
flags = one_map['flags']
virt = one_map['virt']
level = PD_LEVEL if one_map['large_page'] else PT_LEVEL
# Check if addresses have already been mapped.
# Error out if so as they could override kernel mappings.
if pt.is_region_mapped(virt, size, level):
error(("Region 0x%x (%d) already been mapped "
"for --map %s" % (virt, size, one_map['cmdline'])))
# Reserve space in page table, and map the region
pt.reserve_unaligned(virt, size, level), virt, size, flags, level)
def main():
"""Main program"""
global syms
with open(args.kernel, "rb") as elf_fp:
kernel = ELFFile(elf_fp)
syms = get_symbols(kernel)
sym_dummy_pagetables = find_symbol(kernel, "dummy_pagetables")
if sym_dummy_pagetables:
reserved_pt_size = sym_dummy_pagetables['st_size']
reserved_pt_size = None
if isdef("CONFIG_X86_64"):
pclass = PtablesIA32e
elif isdef("CONFIG_X86_PAE"):
pclass = PtablesPAE
pclass = Ptables32bit
debug("building %s" % pclass.__name__)
vm_base = syms["CONFIG_KERNEL_VM_BASE"]
vm_size = syms["CONFIG_KERNEL_VM_SIZE"]
vm_offset = syms["CONFIG_KERNEL_VM_OFFSET"]
sram_base = syms["CONFIG_SRAM_BASE_ADDRESS"]
sram_size = syms["CONFIG_SRAM_SIZE"] * 1024
mapped_kernel_base = syms["z_mapped_start"]
mapped_kernel_size = syms["z_mapped_size"]
sram_offset = syms["CONFIG_SRAM_OFFSET"]
sram_offset = 0
# Figure out if there is any need to do virtual-to-physical
# address translation
virt_to_phys_offset = (sram_base + sram_offset) - (vm_base + vm_offset)
image_base = sram_base
image_size = sram_size
image_base = mapped_kernel_base
image_size = mapped_kernel_size
image_base_phys = image_base + virt_to_phys_offset
ptables_phys = syms["z_x86_pagetables_start"] + virt_to_phys_offset
debug("Address space: 0x%x - 0x%x size 0x%x" %
(vm_base, vm_base + vm_size - 1, vm_size))
debug("Zephyr image: 0x%x - 0x%x size 0x%x" %
(image_base, image_base + image_size - 1, image_size))
if virt_to_phys_offset != 0:
debug("Physical address space: 0x%x - 0x%x size 0x%x" %
(sram_base, sram_base + sram_size - 1, sram_size))
is_perm_regions = isdef("CONFIG_SRAM_REGION_PERMISSIONS")
# Are pages in non-boot, non-pinned sections present at boot.
is_generic_section_present = isdef("CONFIG_LINKER_GENERIC_SECTIONS_PRESENT_AT_BOOT")
if image_size >= vm_size:
error("VM size is too small (have 0x%x need more than 0x%x)" % (vm_size, image_size))
map_flags = 0
if is_perm_regions:
# Don't allow execution by default for any pages. We'll adjust this
# in later calls to pt.set_region_perms()
map_flags = ENTRY_XD
pt = pclass(ptables_phys)
# Instantiate all the paging structures for the address space
pt.reserve(vm_base, vm_size)
# Map the zephyr image
if is_generic_section_present:
map_flags = map_flags | FLAG_P, image_base, image_size, map_flags | ENTRY_RW)
# When generic linker sections are not present in physical memory,
# the corresponding virtual pages should not be mapped to non-existent
# physical pages. So simply identity map them to create the page table
# entries but without the present bit set.
# Boot and pinned sections (if configured) will be mapped to
# physical memory below., image_base, image_size, map_flags | ENTRY_RW)
if virt_to_phys_offset != 0:
# Need to identity map the physical address space
# as it is needed during early boot process.
# This will be unmapped once z_x86_mmu_init()
# is called.
# Note that this only does the identity mapping
# at the page directory level to minimize wasted space.
pt.reserve_unaligned(image_base_phys, image_size, to_level=PD_LEVEL)
pt.identity_map_unaligned(image_base_phys, image_size,
if isdef("CONFIG_X86_64"):
# 64-bit has a special region in the first 64K to bootstrap other CPUs
# from real mode
locore_base = syms["_locore_start"]
locore_size = syms["_lodata_end"] - locore_base
debug("Base addresses: physical 0x%x size 0x%x" % (locore_base,
locore_size)), None, locore_size, map_flags | FLAG_P | ENTRY_RW)
if isdef("CONFIG_XIP"):
# Additionally identity-map all ROM as read-only["CONFIG_FLASH_BASE_ADDRESS"], None,
syms["CONFIG_FLASH_SIZE"] * 1024, map_flags | FLAG_P)
pt.map_region("lnkr_boot", map_flags | FLAG_P | ENTRY_RW, virt_to_phys_offset)
pt.map_region("lnkr_pinned", map_flags | FLAG_P | ENTRY_RW, virt_to_phys_offset)
# Process extra mapping requests
# Adjust mapped region permissions if configured
if is_perm_regions:
# Need to accomplish the following things:
# - Text regions need the XD flag cleared and RW flag removed
# if not built with gdbstub support
# - Rodata regions need the RW flag cleared
# - User mode needs access as we currently do not separate application
# text/rodata from kernel text/rodata
if isdef("CONFIG_GDBSTUB"):
flags = ENTRY_US
if is_generic_section_present:
flags = flags | FLAG_P
pt.set_region_perms("__text_region", flags)
pt.set_region_perms("lnkr_boot_text", flags | FLAG_P)
pt.set_region_perms("lnkr_pinned_text", flags | FLAG_P)
if is_generic_section_present:
flags = flags | FLAG_P
pt.set_region_perms("__rodata_region", flags)
pt.set_region_perms("lnkr_boot_rodata", flags | FLAG_P)
pt.set_region_perms("lnkr_pinned_rodata", flags | FLAG_P)
# If GCOV is enabled, user mode must be able to write to its
# common data area
if isdef("CONFIG_X86_64"):
# Set appropriate permissions for locore areas much like we did
# with the main text/rodata regions
if isdef("CONFIG_X86_KPTI"):
# Set the User bit for the read-only locore/lorodata areas.
# This ensures they get mapped into the User page tables if
# KPTI is turned on. There is no sensitive data in them, and
# they contain text/data needed to take an exception or
# interrupt.
flag_user = ENTRY_US
flag_user = 0
pt.set_region_perms("_locore", FLAG_P | flag_user)
pt.set_region_perms("_lorodata", FLAG_P | ENTRY_XD | flag_user)
written_size = pt.write_output(args.output)
debug("Written %d bytes to %s" % (written_size, args.output))
# Warn if reserved page table is not of correct size
if reserved_pt_size and written_size != reserved_pt_size:
# Figure out how many extra pages needed
size_diff = written_size - reserved_pt_size
page_size = syms["CONFIG_MMU_PAGE_SIZE"]
extra_pages_needed = int(round_up(size_diff, page_size) / page_size)
extra_pages_kconfig = syms["CONFIG_X86_EXTRA_PAGE_TABLE_PAGES"]
if isdef("CONFIG_X86_64"):
extra_pages_needed += ctypes.c_int64(extra_pages_kconfig).value
extra_pages_needed += ctypes.c_int32(extra_pages_kconfig).value
reason = "big" if reserved_pt_size > written_size else "small"
error(("Reserved space for page table is too %s."
(reason, extra_pages_needed))
if __name__ == "__main__":