linux.git/arch/arm64/kernel/module.c, branch v4.13

arm64: fix endianness annotation for reloc_insn_movw() & reloc_insn_imm()

2017-06-29T10:09:39+00:00

Here the functions reloc_insn_movw() & reloc_insn_imm() are used
to read, modify and write back ARM instructions, which are always
stored in memory in little-endian order. These values are thus
correctly converted to/from native order but the pointers used to
hold their addresses are declared as for native order values.

Fix this by declaring the pointers as __le32* and remove the
casts that are now unneeded.

Signed-off-by: Luc Van Oostenryck 
Signed-off-by: Will Deacon

arm64: ftrace: add support for far branches to dynamic ftrace

2017-06-07T10:52:02+00:00

Currently, dynamic ftrace support in the arm64 kernel assumes that all
core kernel code is within range of ordinary branch instructions that
occur in module code, which is usually the case, but is no longer
guaranteed now that we have support for module PLTs and address space
randomization.

Since on arm64, all patching of branch instructions involves function
calls to the same entry point [ftrace_caller()], we can emit the modules
with a trampoline that has unlimited range, and patch both the trampoline
itself and the branch instruction to redirect the call via the trampoline.

Signed-off-by: Ard Biesheuvel 
[will: minor clarification to smp_wmb() comment]
Signed-off-by: Will Deacon

arm64: Silence first allocation with CONFIG_ARM64_MODULE_PLTS=y

2017-05-11T13:43:40+00:00

When CONFIG_ARM64_MODULE_PLTS is enabled, the first allocation using the
module space fails, because the module is too big, and then the module
allocation is attempted from vmalloc space. Silence the first allocation
failure in that case by setting __GFP_NOWARN.

Reviewed-by: Ard Biesheuvel 
Acked-by: Will Deacon 
Signed-off-by: Florian Fainelli 
Signed-off-by: Catalin Marinas

arm64: module: split core and init PLT sections

2017-04-26T11:31:00+00:00

The arm64 module PLT code allocates all PLT entries in a single core
section, since the overhead of having a separate init PLT section is
not justified by the small number of PLT entries usually required for
init code.

However, the core and init module regions are allocated independently,
and there is a corner case where the core region may be allocated from
the VMALLOC region if the dedicated module region is exhausted, but the
init region, being much smaller, can still be allocated from the module
region. This leads to relocation failures if the distance between those
regions exceeds 128 MB. (In fact, this corner case is highly unlikely to
occur on arm64, but the issue has been observed on ARM, whose module
region is much smaller).

So split the core and init PLT regions, and name the latter ".init.plt"
so it gets allocated along with (and sufficiently close to) the .init
sections that it serves. Also, given that init PLT entries may need to
be emitted for branches that target the core module, modify the logic
that disregards defined symbols to only disregard symbols that are
defined in the same section as the relocated branch instruction.

Since there may now be two PLT entries associated with each entry in
the symbol table, we can no longer hijack the symbol::st_size fields
to record the addresses of PLT entries as we emit them for zero-addend
relocations. So instead, perform an explicit comparison to check for
duplicate entries.

Signed-off-by: Ard Biesheuvel 
Signed-off-by: Catalin Marinas

arm64: add support for kernel ASLR

2016-02-24T14:57:27+00:00

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: Ard Biesheuvel 
Signed-off-by: Catalin Marinas

arm64: add support for module PLTs

2016-02-24T14:57:24+00:00

This adds support for emitting PLTs at module load time for relative
branches that are out of range. This is a prerequisite for KASLR, which
may place the kernel and the modules anywhere in the vmalloc area,
making it more likely that branch target offsets exceed the maximum
range of +/- 128 MB.

In this version, I removed the distinction between relocations against
.init executable sections and ordinary executable sections. The reason
is that it is hardly worth the trouble, given that .init.text usually
does not contain that many far branches, and this version now only
reserves PLT entry space for jump and call relocations against undefined
symbols (since symbols defined in the same module can be assumed to be
within +/- 128 MB)

For example, the mac80211.ko module (which is fairly sizable at ~400 KB)
built with -mcmodel=large gives the following relocation counts:

                    relocs    branches   unique     !local
  .text              3925       3347       518        219
  .init.text           11          8         7          1
  .exit.text            4          4         4          1
  .text.unlikely       81         67        36         17

('unique' means branches to unique type/symbol/addend combos, of which
!local is the subset referring to undefined symbols)

IOW, we are only emitting a single PLT entry for the .init sections, and
we are better off just adding it to the core PLT section instead.

Signed-off-by: Ard Biesheuvel 
Signed-off-by: Catalin Marinas

arm64: module: avoid undefined shift behavior in reloc_data()

2016-01-05T11:27:20+00:00

Compilers may engage the improbability drive when encountering shifts
by a distance that is a multiple of the size of the operand type. Since
the required bounds check is very simple here, we can get rid of all the
fuzzy masking, shifting and comparing, and use the documented bounds
directly.

Reported-by: David Binderman 
Signed-off-by: Ard Biesheuvel 
Signed-off-by: Will Deacon

arm64: module: fix relocation of movz instruction with negative immediate

2016-01-05T11:26:44+00:00

The test whether a movz instruction with a signed immediate should be
turned into a movn instruction (i.e., when the immediate is negative)
is flawed, since the value of imm is always positive. Also, the
subsequent bounds check is incorrect since the limit update never
executes, due to the fact that the imm_type comparison will always be
false for negative signed immediates.

Let's fix this by performing the sign test on sval directly, and
replacing the bounds check with a simple comparison against U16_MAX.

Signed-off-by: Ard Biesheuvel 
[will: tidied up use of sval, renamed MOVK enum value to MOVKZ]
Signed-off-by: Will Deacon

arm64: add KASAN support

2015-10-12T16:46:36+00:00

This patch adds arch specific code for kernel address sanitizer
(see Documentation/kasan.txt).

1/8 of kernel addresses reserved for shadow memory. There was no
big enough hole for this, so virtual addresses for shadow were
stolen from vmalloc area.

At early boot stage the whole shadow region populated with just
one physical page (kasan_zero_page). Later, this page reused
as readonly zero shadow for some memory that KASan currently
don't track (vmalloc).
After mapping the physical memory, pages for shadow memory are
allocated and mapped.

Functions like memset/memmove/memcpy do a lot of memory accesses.
If bad pointer passed to one of these function it is important
to catch this. Compiler's instrumentation cannot do this since
these functions are written in assembly.
KASan replaces memory functions with manually instrumented variants.
Original functions declared as weak symbols so strong definitions
in mm/kasan/kasan.c could replace them. Original functions have aliases
with '__' prefix in name, so we could call non-instrumented variant
if needed.
Some files built without kasan instrumentation (e.g. mm/slub.c).
Original mem* function replaced (via #define) with prefixed variants
to disable memory access checks for such files.

Signed-off-by: Andrey Ryabinin 
Tested-by: Linus Walleij 
Reviewed-by: Catalin Marinas 
Signed-off-by: Catalin Marinas

arm64: errata: add module build workaround for erratum #843419

2015-09-17T10:57:03+00:00

Cortex-A53 processors <= r0p4 are affected by erratum #843419 which can
lead to a memory access using an incorrect address in certain sequences
headed by an ADRP instruction.

There is a linker fix to generate veneers for ADRP instructions, but
this doesn't work for kernel modules which are built as unlinked ELF
objects.

This patch adds a new config option for the erratum which, when enabled,
builds kernel modules with the mcmodel=large flag. This uses absolute
addressing for all kernel symbols, thereby removing the use of ADRP as
a PC-relative form of addressing. The ADRP relocs are removed from the
module loader so that we fail to load any potentially affected modules.

Cc: 
Acked-by: Catalin Marinas 
Signed-off-by: Will Deacon