In the Linux kernel, struct type variables are rarely passed by-value,
and so functions that initialize such variables typically take an input
reference to the variable rather than returning a value that can
subsequently be used in an assignment.

If the initalization function is not part of the same compilation unit,
the lack of an assignment operation defeats any analysis the compiler
can perform as to whether the variable may be used before having been
initialized. This means we may end up passing on such variables
uninitialized, resulting in potential information leaks.

So extend the existing structleak GCC plugin so it will [optionally]
apply to all struct type variables that have their address taken at any
point, rather than only to variables of struct types that have a __user
annotation.
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NKees Cook <keescook@chromium.org>

This randstruct plugin is modified from Brad Spengler/PaX Team's code
in the last public patch of grsecurity/PaX based on my understanding
of the code. Changes or omissions from the original code are mine and
don't reflect the original grsecurity/PaX code.

The randstruct GCC plugin randomizes the layout of selected structures
at compile time, as a probabilistic defense against attacks that need to
know the layout of structures within the kernel. This is most useful for
"in-house" kernel builds where neither the randomization seed nor other
build artifacts are made available to an attacker. While less useful for
distribution kernels (where the randomization seed must be exposed for
third party kernel module builds), it still has some value there since now
all kernel builds would need to be tracked by an attacker.

In more performance sensitive scenarios, GCC_PLUGIN_RANDSTRUCT_PERFORMANCE
can be selected to make a best effort to restrict randomization to
cacheline-sized groups of elements, and will not randomize bitfields. This
comes at the cost of reduced randomization.

Two annotations are defined,__randomize_layout and __no_randomize_layout,
which respectively tell the plugin to either randomize or not to
randomize instances of the struct in question. Follow-on patches enable
the auto-detection logic for selecting structures for randomization
that contain only function pointers. It is disabled here to assist with
bisection.

Since any randomized structs must be initialized using designated
initializers, __randomize_layout includes the __designated_init annotation
even when the plugin is disabled so that all builds will require
the needed initialization. (With the plugin enabled, annotations for
automatically chosen structures are marked as well.)

The main differences between this implemenation and grsecurity are:
- disable automatic struct selection (to be enabled in follow-up patch)
- add designated_init attribute at runtime and for manual marking
- clarify debugging output to differentiate bad cast warnings
- add whitelisting infrastructure
- support gcc 7's DECL_ALIGN and DECL_MODE changes (Laura Abbott)
- raise minimum required GCC version to 4.7

Earlier versions of this patch series were ported by Michael Leibowitz.
Signed-off-by: NKees Cook <keescook@chromium.org>

Enable support for GCC plugins on powerpc.

Add an additional version check in gcc-plugins-check to advise users to
upgrade to gcc 5.2+ on powerpc to avoid issues with header files (gcc <=
4.6) or missing copies of rs6000-cpus.def (4.8 to 5.1 on 64-bit
targets).
Signed-off-by: NAndrew Donnellan <andrew.donnellan@au1.ibm.com>
Acked-by: NKees Cook <keescook@chromium.org>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

The variable DISABLE_LATENT_ENTROPY_PLUGIN is defined when
CONFIG_PAX_LATENT_ENTROPY is set. This is leftover from the original PaX
version of the plugin code and doesn't actually exist. Change the condition
to depend on CONFIG_GCC_PLUGIN_LATENT_ENTROPY instead.

Fixes: 38addce8 ("gcc-plugins: Add latent_entropy plugin")
Signed-off-by: NAndrew Donnellan <andrew.donnellan@au1.ibm.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

This plugin detects any structures that contain __user attributes and
makes sure it is being fully initialized so that a specific class of
information exposure is eliminated. (This plugin was originally designed
to block the exposure of siginfo in CVE-2013-2141.)

Ported from grsecurity/PaX. This version adds a verbose option to the
plugin and the Kconfig.
Signed-off-by: NKees Cook <keescook@chromium.org>

This adds a new gcc plugin named "latent_entropy". It is designed to
extract as much possible uncertainty from a running system at boot time as
possible, hoping to capitalize on any possible variation in CPU operation
(due to runtime data differences, hardware differences, SMP ordering,
thermal timing variation, cache behavior, etc).

At the very least, this plugin is a much more comprehensive example for
how to manipulate kernel code using the gcc plugin internals.

The need for very-early boot entropy tends to be very architecture or
system design specific, so this plugin is more suited for those sorts
of special cases. The existing kernel RNG already attempts to extract
entropy from reliable runtime variation, but this plugin takes the idea to
a logical extreme by permuting a global variable based on any variation
in code execution (e.g. a different value (and permutation function)
is used to permute the global based on loop count, case statement,
if/then/else branching, etc).

To do this, the plugin starts by inserting a local variable in every
marked function. The plugin then adds logic so that the value of this
variable is modified by randomly chosen operations (add, xor and rol) and
random values (gcc generates separate static values for each location at
compile time and also injects the stack pointer at runtime). The resulting
value depends on the control flow path (e.g., loops and branches taken).

Before the function returns, the plugin mixes this local variable into
the latent_entropy global variable. The value of this global variable
is added to the kernel entropy pool in do_one_initcall() and _do_fork(),
though it does not credit any bytes of entropy to the pool; the contents
of the global are just used to mix the pool.

Additionally, the plugin can pre-initialize arrays with build-time
random contents, so that two different kernel builds running on identical
hardware will not have the same starting values.
Signed-off-by: NEmese Revfy <re.emese@gmail.com>
[kees: expanded commit message and code comments]
Signed-off-by: NKees Cook <keescook@chromium.org>

This adds support for building more complex gcc plugins that live in a
subdirectory instead of just in a single source file.
Reported-by: NPaX Team <pageexec@freemail.hu>
Signed-off-by: NEmese Revfy <re.emese@gmail.com>
[kees: clarified commit message]
Signed-off-by: NKees Cook <keescook@chromium.org>

The latent_entropy plugin needs to pass arguments, so this adds the
support.
Signed-off-by: NEmese Revfy <re.emese@gmail.com>
Signed-off-by: NKees Cook <keescook@chromium.org>

When the compiler doesn't support gcc plugins (either due to missing
headers or too old a version), report the problem and abort the build
instead of emitting a warning and letting the build founder with arcane
compiler errors.
Signed-off-by: NKees Cook <keescook@chromium.org>

The sancov gcc plugin inserts a __sanitizer_cov_trace_pc() call
at the start of basic blocks.

This plugin is a helper plugin for the kcov feature. It supports
all gcc versions with plugin support (from gcc-4.5 on).
It is based on the gcc commit "Add fuzzing coverage support" by Dmitry Vyukov
(https://gcc.gnu.org/viewcvs/gcc?limit_changes=0&view=revision&revision=231296).
Signed-off-by: NEmese Revfy <re.emese@gmail.com>
Acked-by: NKees Cook <keescook@chromium.org>
Signed-off-by: NMichal Marek <mmarek@suse.com>

Add a very simple plugin to demonstrate the GCC plugin infrastructure. This GCC
plugin computes the cyclomatic complexity of each function.

The complexity M of a function's control flow graph is defined as:
M = E - N + 2P
where
E = the number of edges
N = the number of nodes
P = the number of connected components (exit nodes).
Signed-off-by: NEmese Revfy <re.emese@gmail.com>
Acked-by: NKees Cook <keescook@chromium.org>
Signed-off-by: NMichal Marek <mmarek@suse.com>

This patch allows to build the whole kernel with GCC plugins. It was ported from
grsecurity/PaX. The infrastructure supports building out-of-tree modules and
building in a separate directory. Cross-compilation is supported too.
Currently the x86, arm, arm64 and uml architectures enable plugins.

The directory of the gcc plugins is scripts/gcc-plugins. You can use a file or a directory
there. The plugins compile with these options:
 * -fno-rtti: gcc is compiled with this option so the plugins must use it too
 * -fno-exceptions: this is inherited from gcc too
 * -fasynchronous-unwind-tables: this is inherited from gcc too
 * -ggdb: it is useful for debugging a plugin (better backtrace on internal
    errors)
 * -Wno-narrowing: to suppress warnings from gcc headers (ipa-utils.h)
 * -Wno-unused-variable: to suppress warnings from gcc headers (gcc_version
    variable, plugin-version.h)

The infrastructure introduces a new Makefile target called gcc-plugins. It
supports all gcc versions from 4.5 to 6.0. The scripts/gcc-plugin.sh script
chooses the proper host compiler (gcc-4.7 can be built by either gcc or g++).
This script also checks the availability of the included headers in
scripts/gcc-plugins/gcc-common.h.

The gcc-common.h header contains frequently included headers for GCC plugins
and it has a compatibility layer for the supported gcc versions.

The gcc-generate-*-pass.h headers automatically generate the registration
structures for GIMPLE, SIMPLE_IPA, IPA and RTL passes.

Note that 'make clean' keeps the *.so files (only the distclean or mrproper
targets clean all) because they are needed for out-of-tree modules.

Based on work created by the PaX Team.
Signed-off-by: NEmese Revfy <re.emese@gmail.com>
Acked-by: NKees Cook <keescook@chromium.org>
Signed-off-by: NMichal Marek <mmarek@suse.com>