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x86: mmu: don't mark generic sections as present if desired

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With demand paging, it is possible for data pages to not be
present in physical memory. The gen_mmu.py script is updated
so that, if so desired, the generic sections are marked
non-present so the paging mechanism can bring them in
if needed.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>
This commit is contained in:
Daniel Leung 2021-07-12 13:35:14 -07:00 • committed by Christopher Friedt
commit c11ad59ed6
1 changed files with 34 additions and 16 deletions
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50
arch/x86/gen_mmu.py
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@ -786,21 +786,34 @@ def main():
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 = FLAG_P | ENTRY_XD
else:
map_flags = FLAG_P
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
pt.map(image_base_phys, image_base, image_size, map_flags | ENTRY_RW)
if is_generic_section_present:
map_flags = map_flags | FLAG_P
pt.map(image_base_phys, image_base, image_size, map_flags | ENTRY_RW)
else:
# 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.
pt.map(image_base, image_base, image_size, map_flags | ENTRY_RW)
if virt_to_phys_offset != 0:
# Need to identity map the physical address space
@ -820,18 +833,18 @@ def main():
locore_size = syms["_lodata_end"] - locore_base
debug("Base addresses: physical 0x%x size 0x%x" % (locore_base,
locore_size))
pt.map(locore_base, None, locore_size, map_flags | ENTRY_RW)
pt.map(locore_base, None, locore_size, map_flags | FLAG_P | ENTRY_RW)
if isdef("CONFIG_XIP"):
# Additionally identity-map all ROM as read-only
pt.map(syms["CONFIG_FLASH_BASE_ADDRESS"], None,
syms["CONFIG_FLASH_SIZE"] * 1024, map_flags)
syms["CONFIG_FLASH_SIZE"] * 1024, map_flags | FLAG_P)
if isdef("CONFIG_LINKER_USE_BOOT_SECTION"):
pt.map_region("lnkr_boot", map_flags | ENTRY_RW, virt_to_phys_offset)
pt.map_region("lnkr_boot", map_flags | FLAG_P | ENTRY_RW, virt_to_phys_offset)
if isdef("CONFIG_LINKER_USE_PINNED_SECTION"):
pt.map_region("lnkr_pinned", map_flags | 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
if args.map:
@ -846,27 +859,32 @@ def main():
# - User mode needs access as we currently do not separate application
# text/rodata from kernel text/rodata
if isdef("CONFIG_GDBSTUB"):
flags = FLAG_P | ENTRY_US | ENTRY_RW
flags = ENTRY_US | ENTRY_RW
else:
flags = FLAG_P | ENTRY_US
flags = ENTRY_US
if is_generic_section_present:
flags = flags | FLAG_P
pt.set_region_perms("_image_text", flags)
if isdef("CONFIG_LINKER_USE_BOOT_SECTION"):
pt.set_region_perms("lnkr_boot_text", flags)
pt.set_region_perms("lnkr_boot_text", flags | FLAG_P)
if isdef("CONFIG_LINKER_USE_PINNED_SECTION"):
pt.set_region_perms("lnkr_pinned_text", flags)
pt.set_region_perms("lnkr_pinned_text", flags | FLAG_P)
flags = ENTRY_US | ENTRY_XD
if is_generic_section_present:
flags = flags | FLAG_P
flags = FLAG_P | ENTRY_US | ENTRY_XD
pt.set_region_perms("_image_rodata", flags)
if isdef("CONFIG_LINKER_USE_BOOT_SECTION"):
pt.set_region_perms("lnkr_boot_rodata", flags)
pt.set_region_perms("lnkr_boot_rodata", flags | FLAG_P)
if isdef("CONFIG_LINKER_USE_PINNED_SECTION"):
pt.set_region_perms("lnkr_pinned_rodata", flags)
pt.set_region_perms("lnkr_pinned_rodata", flags | FLAG_P)
if isdef("CONFIG_COVERAGE_GCOV") and isdef("CONFIG_USERSPACE"):
# If GCOV is enabled, user mode must be able to write to its