The vast majority of virtual allocations in the vmalloc region are followed
by a guard page, which can help to avoid overruning on vma into another,
which may map a read-sensitive device.

This patch adds a guard page to the end of the kernel image mapping (i.e.
following the data/bss segments).

Cc: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NWill Deacon <will.deacon@arm.com>

arm64's mm/mmu.c uses vm_area_add_early, struct vm_area and other
definitions  but relies on implict inclusion of linux/vmalloc.h which
means that changes in other headers could break the build. Thus, add an
explicit include.
Acked-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NTobias Klauser <tklauser@distanz.ch>
Signed-off-by: NWill Deacon <will.deacon@arm.com>

arch_kexec_protect_crashkres() and arch_kexec_unprotect_crashkres()
are meant to be called by kexec_load() in order to protect the memory
allocated for crash dump kernel once the image is loaded.

The protection is implemented by unmapping the relevant segments in crash
dump kernel memory, rather than making it read-only as other archs do,
to prevent coherency issues due to potential cache aliasing (with
mismatched attributes).

Page-level mappings are consistently used here so that we can change
the attributes of segments in page granularity as well as shrink the region
also in page granularity through /sys/kernel/kexec_crash_size, putting
the freed memory back to buddy system.
Signed-off-by: NAKASHI Takahiro <takahiro.akashi@linaro.org>
Reviewed-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

This is the third attempt at enabling the use of contiguous hints for
kernel mappings. The most recent attempt 0bfc445d was reverted after
it turned out that updating permission attributes on live contiguous ranges
may result in TLB conflicts. So this time, the contiguous hint is not set
for .rodata or for the linear alias of .text/.rodata, both of which are
mapped read-write initially, and remapped read-only at a later stage.
(Note that the latter region could also be unmapped and remapped again
with updated permission attributes, given that the region, while live, is
only mapped for the convenience of the hibernation code, but that also
means the TLB footprint is negligible anyway, so why bother)

This enables the following contiguous range sizes for the virtual mapping
of the kernel image, and for the linear mapping:

          granule size |  cont PTE  |  cont PMD  |
          -------------+------------+------------+
               4 KB    |    64 KB   |   32 MB    |
              16 KB    |     2 MB   |    1 GB*   |
              64 KB    |     2 MB   |   16 GB*   |

* Only when built for 3 or more levels of translation. This is due to the
  fact that a 2 level configuration only consists of PGDs and PTEs, and the
  added complexity of dealing with folded PMDs is not justified considering
  that 16 GB contiguous ranges are likely to be ignored by the hardware (and
  16k/2 levels is a niche configuration)
Reviewed-by: NMark Rutland <mark.rutland@arm.com>
Tested-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

The routines __pud_populate and __pmd_populate only create a table
entry at their respective level which refers to the next level page
by its physical address, so there is no reason to map this page and
then unmap it immediately after.
Reviewed-by: NMark Rutland <mark.rutland@arm.com>
Tested-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

In preparation of extending the policy for manipulating kernel mappings
with whether or not contiguous hints may be used in the page tables,
replace the bool 'page_mappings_only' with a flags field and a flag
NO_BLOCK_MAPPINGS.
Reviewed-by: NMark Rutland <mark.rutland@arm.com>
Tested-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

A mapping with the contiguous bit cannot be safely manipulated while
live, regardless of whether the bit changes between the old and new
mapping. So take this into account when deciding whether the change
is safe.
Reviewed-by: NMark Rutland <mark.rutland@arm.com>
Tested-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

The debug_pagealloc facility manipulates kernel mappings in the linear
region at page granularity to detect out of bounds or use-after-free
accesses. Since the kernel segments are not allocated dynamically,
there is no point in taking the debug_pagealloc_enabled flag into
account for them, and we can use block mappings unconditionally.

Note that this applies equally to the linear alias of text/rodata:
we will never have dynamic allocations there given that the same
memory is statically in use by the kernel image.
Reviewed-by: NMark Rutland <mark.rutland@arm.com>
Tested-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

Align the function prototype of alloc_init_pte() with its pmd and pud
counterparts by replacing the pfn parameter with the equivalent physical
address.
Reviewed-by: NMark Rutland <mark.rutland@arm.com>
Tested-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

To avoid having mappings that are writable and executable at the same
time, split the init region into a .init.text region that is mapped
read-only, and a .init.data region that is mapped non-executable.

This is possible now that the alternative patching occurs via the linear
mapping, and the linear alias of the init region is always mapped writable
(but never executable).

Since the alternatives descriptions themselves are read-only data, move
those into the .init.text region.
Reviewed-by: NLaura Abbott <labbott@redhat.com>
Reviewed-by: NMark Rutland <mark.rutland@arm.com>
Tested-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

Now that alternatives patching code no longer relies on the primary
mapping of .text being writable, we can remove the code that removes
the writable permissions post-init time, and map it read-only from
the outset.

To preserve the existing behavior under rodata=off, which is relied
upon by external debuggers to manage software breakpoints (as pointed
out by Mark), add an early_param() check for rodata=, and use RWX
permissions if it set to 'off'.
Reviewed-by: NLaura Abbott <labbott@redhat.com>
Reviewed-by: NKees Cook <keescook@chromium.org>
Reviewed-by: NMark Rutland <mark.rutland@arm.com>
Tested-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

One important rule of thumb when desiging a secure software system is
that memory should never be writable and executable at the same time.
We mostly adhere to this rule in the kernel, except at boot time, when
regions may be mapped RWX until after we are done applying alternatives
or making other one-off changes.

For the alternative patching, we can improve the situation by applying
the fixups via the linear mapping, which is never mapped with executable
permissions. So map the linear alias of .text with RW- permissions
initially, and remove the write permissions as soon as alternative
patching has completed.
Reviewed-by: NLaura Abbott <labbott@redhat.com>
Reviewed-by: NMark Rutland <mark.rutland@arm.com>
Tested-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

In preparation of refactoring the kernel mapping logic so that text regions
are never mapped writable, which would require adding explicit TLB
maintenance to new call sites of create_mapping_late() (which is currently
invoked twice from the same function), move the TLB maintenance from the
call site into create_mapping_late() itself, and change it from a full
TLB flush into a flush by VA, which is more appropriate here.

Also, given that create_mapping_late() has evolved into a routine that only
updates protection bits on existing mappings, rename it to
update_mapping_prot()
Reviewed-by: NMark Rutland <mark.rutland@arm.com>
Tested-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

This reverts commit 0bfc445d.

When we change the permissions of regions mapped using contiguous
entries, the architecture requires us to follow a Break-Before-Make
strategy, breaking *all* associated entries before we can change any of
the following properties from the entries:

 - presence of the contiguous bit
 - output address
 - attributes
 - permissiones

Failure to do so can result in a number of problems (e.g. TLB conflict
aborts and/or erroneous results from TLB lookups).

See ARM DDI 0487A.k_iss10775, "Misprogramming of the Contiguous bit",
page D4-1762.

We do not take this into account when altering the permissions of kernel
segments in mark_rodata_ro(), where we change the permissions of live
contiguous entires one-by-one, leaving them transiently inconsistent.
This has been observed to result in failures on some fast model
configurations.

Unfortunately, we cannot follow Break-Before-Make here as we'd have to
unmap kernel text and data used to perform the sequence.

For the timebeing, revert commit 0bfc445d so as to avoid issues
resulting from this misuse of the contiguous bit.
Signed-off-by: NMark Rutland <mark.rutland@arm.com>
Acked-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Reported-by: NJean-Philippe Brucker <jean-philippe.brucker@arm.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <Will.Deacon@arm.com>
Cc: stable@vger.kernel.org # v4.10
Signed-off-by: NWill Deacon <will.deacon@arm.com>

With 4 levels of 16KB pages, we get this warning about the fact that we are
copying a whole page into an array that is declared as having only two pointers
for the top level of the page table:

arch/arm64/mm/mmu.c: In function 'paging_init':
arch/arm64/mm/mmu.c:528:2: error: 'memcpy' writing 16384 bytes into a region of size 16 overflows the destination [-Werror=stringop-overflow=]

This is harmless since we actually reserve a whole page in the definition of the
array that comes from, and just the extern declaration is short. The pgdir
is initialized to zero either way, so copying the actual entries here seems
like the best solution.
Acked-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NWill Deacon <will.deacon@arm.com>

Cosmetic change to use phys_addr_t instead of unsigned long for the
return value of __pa_symbol().
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
Acked-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NMiles Chen <miles.chen@mediatek.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>

__pa_symbol is technically the marcro that should be used for kernel
symbols. Switch to this as a pre-requisite for DEBUG_VIRTUAL which
will do bounds checking.
Reviewed-by: NMark Rutland <mark.rutland@arm.com>
Tested-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NLaura Abbott <labbott@redhat.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>

Page mappings with full RWX permissions are a security risk. x86
has an option to walk the page tables and dump any bad pages.
(See e1a58320 ("x86/mm: Warn on W^X mappings")). Add a similar
implementation for arm64.
Reviewed-by: NKees Cook <keescook@chromium.org>
Reviewed-by: NMark Rutland <mark.rutland@arm.com>
Tested-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NLaura Abbott <labbott@redhat.com>
Reviewed-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
[catalin.marinas@arm.com: folded fix for KASan out of bounds from Mark Rutland]
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

Now that we no longer allow live kernel PMDs to be split, it is safe to
start using the contiguous bit for kernel mappings. So set the contiguous
bit in the kernel page mappings for regions whose size and alignment are
suitable for this.

This enables the following contiguous range sizes for the virtual mapping
of the kernel image, and for the linear mapping:

          granule size |  cont PTE  |  cont PMD  |
          -------------+------------+------------+
               4 KB    |    64 KB   |   32 MB    |
              16 KB    |     2 MB   |    1 GB*   |
              64 KB    |     2 MB   |   16 GB*   |

* Only when built for 3 or more levels of translation. This is due to the
  fact that a 2 level configuration only consists of PGDs and PTEs, and the
  added complexity of dealing with folded PMDs is not justified considering
  that 16 GB contiguous ranges are likely to be ignored by the hardware (and
  16k/2 levels is a niche configuration)
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

In preparation of adding support for contiguous PTE and PMD mappings,
let's replace 'block_mappings_allowed' with 'page_mappings_only', which
will be a more accurate description of the nature of the setting once we
add such contiguous mappings into the mix.
Reviewed-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

Now that we take care not manipulate the live kernel page tables in a
way that may lead to TLB conflicts, the case where a table mapping is
replaced by a block mapping can no longer occur. So remove the handling
of this at the PUD and PMD levels, and instead, BUG() on any occurrence
of live kernel page table manipulations that modify anything other than
the permission bits.

Since mark_rodata_ro() is the only caller where the kernel mappings that
are being manipulated are actually live, drop the various conditional
flush_tlb_all() invocations, and add a single call to mark_rodata_ro()
instead.
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

There is only fixup_init() in mm.h , and it is only called
in free_initmem(), so move the codes from fixup_init() into
free_initmem(), then drop fixup_init() and mm.h.
Acked-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NKefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>

These objects are set during initialization, thereafter are read only.

Previously I only want to mark vdso_pages, vdso_spec, vectors_page and
cpu_ops as __read_mostly from performance point of view. Then inspired
by Kees's patch[1] to apply more __ro_after_init for arm, I think it's
better to mark them as __ro_after_init. What's more, I find some more
objects are also read only after init. So apply __ro_after_init to all
of them.

This patch also removes global vdso_pagelist and tries to clean up
vdso_spec[] assignment code.

[1] http://www.spinics.net/lists/arm-kernel/msg523188.htmlAcked-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NJisheng Zhang <jszhang@marvell.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>

As reported by Zijun, the fdt_check_header() call in __fixmap_remap_fdt()
is not safe since it is not guaranteed that the FDT header is mapped
completely. Due to the minimum alignment of 8 bytes, the only fields we
can assume to be mapped are 'magic' and 'totalsize'.

Since the OF layer is in charge of validating the FDT image, and we are
only interested in making reasonably sure that the size field contains
a meaningful value, replace the fdt_check_header() call with an explicit
comparison of the magic field's value against the expected value.

Cc: <stable@vger.kernel.org>
Reported-by: NZijun Hu <zijun_hu@htc.com>
Acked-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NWill Deacon <will.deacon@arm.com>

The kernel page table creation routines are accessible to other subsystems
(e.g., EFI) via the create_pgd_mapping() entry point, which allows mappings
to be created that are not covered by init_mm.

Since generic code such as apply_to_page_range() may expect translation
table pages that are not associated with init_mm to be covered by fully
constructed struct pages, add a call to pgtable_page_ctor() in the alloc
function used by create_pgd_mapping. Since it is no longer used by
create_mapping_late(), also update the name of this function to better
reflect its purpose.
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: NLaura Abbott <labbott@redhat.com>
Tested-by: NSudeep Holla <sudeep.holla@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

The only purpose served by create_mapping_late() is to remap the already
mapped .text and .rodata kernel segments with read-only permissions. Since
we no longer allow block mappings to be split or merged,
create_mapping_late() should not pass an allocation function pointer into
__create_pgd_mapping(). So pass NULL instead.
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: NLaura Abbott <labbott@redhat.com>
Tested-by: NSudeep Holla <sudeep.holla@arm.com>
Acked-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

The routine __create_pgd_mapping() does nothing except calling init_pgd(),
which has no other callers. So fold the latter into the former. Also, drop
a comment that has gone stale.
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

Since the efi_create_mapping() no longer generates block mappings
and being the last user of the split_p*d code, remove these functions
and the corresponding TLBI.
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>
[ardb: replace 'overlapping regions' with 'block mappings' in commit log]
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

Add a bool parameter 'allow_block_mappings' to create_pgd_mapping() and
the various helper functions that it descends into, to give the caller
control over whether block entries may be used to create the mapping.

The UEFI runtime mapping routines will use this to avoid creating block
entries that would need to split up into page entries when applying the
permissions listed in the Memory Attributes firmware table.

This also replaces the block_mappings_allowed() helper function that was
added for DEBUG_PAGEALLOC functionality, but the resulting code is
functionally equivalent (given that debug_page_alloc does not operate on
EFI page table entries anyway)
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

The memblock_alloc() and memblock_alloc_base() will panic on their own
if no free memory, remove pointless BUG_ON.
Signed-off-by: NKefeng Wang <wangkefeng.wang@huawei.com>
Acked-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

As Kees Cook notes in the ARM counterpart of this patch [0]:

  The _etext position is defined to be the end of the kernel text code,
  and should not include any part of the data segments. This interferes
  with things that might check memory ranges and expect executable code
  up to _etext.

In particular, Kees is referring to the HARDENED_USERCOPY patch set [1],
which rejects attempts to call copy_to_user() on kernel ranges containing
executable code, but does allow access to the .rodata segment. Regardless
of whether one may or may not agree with the distinction, it makes sense
for _etext to have the same meaning across architectures.

So let's put _etext where it belongs, between .text and .rodata, and fix
up existing references to use __init_begin instead, which unlike _end_rodata
includes the exception and notes sections as well.

The _etext references in kaslr.c are left untouched, since its references
to [_stext, _etext) are meant to capture potential jump instruction targets,
and so disregarding .rodata is actually an improvement here.

[0] http://article.gmane.org/gmane.linux.kernel/2245084
[1] http://thread.gmane.org/gmane.linux.kernel.hardened.devel/2502Reported-by: NKees Cook <keescook@chromium.org>
Reviewed-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: NKees Cook <keescook@chromium.org>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

In order to extract NUMA information from the device tree, we need to
have the tree in its unflattened form.

Move the call to bootmem_init() in the tail of paging_init() into
setup_arch, and adjust header files so that its declaration is
visible.

Move the unflatten_device_tree() call between the calls to
paging_init() and bootmem_init().  Follow on patches add NUMA handling
to bootmem_init().
Signed-off-by: NDavid Daney <david.daney@cavium.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>

Keeping .head.text out of the .text mapping buys us very little: its actual
payload is only 4 KB, most of which is padding, but the page alignment may
add up to 2 MB (in case of CONFIG_DEBUG_ALIGN_RODATA=y) of additional
padding to the uncompressed kernel Image.

Also, on 4 KB granule kernels, the 4 KB misalignment of .text forces us to
map the adjacent 56 KB of code without the PTE_CONT attribute, and since
this region contains things like the vector table and the GIC interrupt
handling entry point, this region is likely to benefit from the reduced TLB
pressure that results from PTE_CONT mappings.

So remove the alignment between the .head.text and .text sections, and use
the [_text, _etext) rather than the [_stext, _etext) interval for mapping
the .text segment.
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NWill Deacon <will.deacon@arm.com>

Replace the poorly defined term chunk with segment, which is a term that is
already used by the ELF spec to describe contiguous mappings with the same
permission attributes of statically allocated ranges of an executable.
Acked-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NWill Deacon <will.deacon@arm.com>

Commit 324420bf ("arm64: add support for ioremap() block
mappings") added new p?d_set_huge functions which do the hard work to
generate and set a correct block entry.

These differ from open-coded huge page creation in the early page table
code by explicitly setting the P?D_TYPE_SECT bits (which are implicitly
retained by mk_sect_prot() for any valid prot), but are otherwise
identical (and cannot fail on arm64).

For simplicity and consistency, make use of these in the initial page
table creation code.
Signed-off-by: NMark Rutland <mark.rutland@arm.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

Currently the .rodata section is actually still executable when DEBUG_RODATA
is enabled. This changes that so the .rodata is actually read only, no execute.
It also adds the .rodata section to the mem_init banner.
Signed-off-by: NJeremy Linton <jeremy.linton@arm.com>
Reviewed-by: NKees Cook <keescook@chromium.org>
Acked-by: NMark Rutland <mark.rutland@arm.com>
[catalin.marinas@arm.com: added vm_struct vmlinux_rodata in map_kernel()]
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

This adds support for KASLR is implemented, based on entropy provided by
the bootloader in the /chosen/kaslr-seed DT property. Depending on the size
of the address space (VA_BITS) and the page size, the entropy in the
virtual displacement is up to 13 bits (16k/2 levels) and up to 25 bits (all
4 levels), with the sidenote that displacements that result in the kernel
image straddling a 1GB/32MB/512MB alignment boundary (for 4KB/16KB/64KB
granule kernels, respectively) are not allowed, and will be rounded up to
an acceptable value.

If CONFIG_RANDOMIZE_MODULE_REGION_FULL is enabled, the module region is
randomized independently from the core kernel. This makes it less likely
that the location of core kernel data structures can be determined by an
adversary, but causes all function calls from modules into the core kernel
to be resolved via entries in the module PLTs.

If CONFIG_RANDOMIZE_MODULE_REGION_FULL is not enabled, the module region is
randomized by choosing a page aligned 128 MB region inside the interval
[_etext - 128 MB, _stext + 128 MB). This gives between 10 and 14 bits of
entropy (depending on page size), independently of the kernel randomization,
but still guarantees that modules are within the range of relative branch
and jump instructions (with the caveat that, since the module region is
shared with other uses of the vmalloc area, modules may need to be loaded
further away if the module region is exhausted)
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

This relaxes the kernel Image placement requirements, so that it
may be placed at any 2 MB aligned offset in physical memory.

This is accomplished by ignoring PHYS_OFFSET when installing
memblocks, and accounting for the apparent virtual offset of
the kernel Image. As a result, virtual address references
below PAGE_OFFSET are correctly mapped onto physical references
into the kernel Image regardless of where it sits in memory.

Special care needs to be taken for dealing with memory limits passed
via mem=, since the generic implementation clips memory top down, which
may clip the kernel image itself if it is loaded high up in memory. To
deal with this case, we simply add back the memory covering the kernel
image, which may result in more memory to be retained than was passed
as a mem= parameter.

Since mem= should not be considered a production feature, a panic notifier
handler is installed that dumps the memory limit at panic time if one was
set.
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

This moves the module area to right before the vmalloc area, and moves
the kernel image to the base of the vmalloc area. This is an intermediate
step towards implementing KASLR, which allows the kernel image to be
located anywhere in the vmalloc area.

Since other subsystems such as hibernate may still need to refer to the
kernel text or data segments via their linears addresses, both are mapped
in the linear region as well. The linear alias of the text region is
mapped read-only/non-executable to prevent inadvertent modification or
execution.
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

Since the early fixmap page tables are populated using pages that are
part of the static footprint of the kernel, they are covered by the
initial kernel mapping, and we can refer to them without using __va/__pa
translations, which are tied to the linear mapping.

Since the fixmap page tables are disjoint from the kernel mapping up
to the top level pgd entry, we can refer to bm_pte[] directly, and there
is no need to walk the page tables and perform __pa()/__va() translations
at each step.
Reviewed-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>