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a5b0dc5a46
I noticed that randconfig builds with gcc no longer produce a lot of
ccache hits, unlike with clang, and traced this back to plugins
now being enabled unconditionally if they are supported.
I am now working around this by adding
export CCACHE_COMPILERCHECK=/usr/bin/size -A %compiler%
to my top-level Makefile. This changes the heuristic that ccache uses
to determine whether the plugins are the same after a 'make clean'.
However, it also seems that being able to just turn off the plugins is
generally useful, at least for build testing it adds noticeable overhead
but does not find a lot of bugs additional bugs, and may be easier for
ccache users than my workaround.
Fixes: 9f671e5815 ("security: Create "kernel hardening" config area")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Masahiro Yamada <masahiroy@kernel.org>
Link: https://lore.kernel.org/r/20191211133951.401933-1-arnd@arndb.de
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
116 lines
4.1 KiB
Plaintext
116 lines
4.1 KiB
Plaintext
# SPDX-License-Identifier: GPL-2.0-only
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preferred-plugin-hostcc := $(if-success,[ $(gcc-version) -ge 40800 ],$(HOSTCXX),$(HOSTCC))
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config PLUGIN_HOSTCC
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string
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default "$(shell,$(srctree)/scripts/gcc-plugin.sh "$(preferred-plugin-hostcc)" "$(HOSTCXX)" "$(CC)")" if CC_IS_GCC
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help
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Host compiler used to build GCC plugins. This can be $(HOSTCXX),
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$(HOSTCC), or a null string if GCC plugin is unsupported.
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config HAVE_GCC_PLUGINS
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bool
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help
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An arch should select this symbol if it supports building with
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GCC plugins.
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menuconfig GCC_PLUGINS
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bool "GCC plugins"
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depends on HAVE_GCC_PLUGINS
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depends on PLUGIN_HOSTCC != ""
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default y
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help
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GCC plugins are loadable modules that provide extra features to the
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compiler. They are useful for runtime instrumentation and static analysis.
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See Documentation/core-api/gcc-plugins.rst for details.
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if GCC_PLUGINS
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config GCC_PLUGIN_CYC_COMPLEXITY
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bool "Compute the cyclomatic complexity of a function" if EXPERT
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depends on !COMPILE_TEST # too noisy
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help
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The complexity M of a function's control flow graph is defined as:
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M = E - N + 2P
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where
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E = the number of edges
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N = the number of nodes
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P = the number of connected components (exit nodes).
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Enabling this plugin reports the complexity to stderr during the
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build. It mainly serves as a simple example of how to create a
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gcc plugin for the kernel.
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config GCC_PLUGIN_SANCOV
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bool
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help
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This plugin inserts a __sanitizer_cov_trace_pc() call at the start of
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basic blocks. It supports all gcc versions with plugin support (from
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gcc-4.5 on). It is based on the commit "Add fuzzing coverage support"
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by Dmitry Vyukov <dvyukov@google.com>.
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config GCC_PLUGIN_LATENT_ENTROPY
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bool "Generate some entropy during boot and runtime"
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help
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By saying Y here the kernel will instrument some kernel code to
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extract some entropy from both original and artificially created
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program state. This will help especially embedded systems where
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there is little 'natural' source of entropy normally. The cost
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is some slowdown of the boot process (about 0.5%) and fork and
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irq processing.
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Note that entropy extracted this way is not cryptographically
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secure!
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This plugin was ported from grsecurity/PaX. More information at:
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* https://grsecurity.net/
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* https://pax.grsecurity.net/
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config GCC_PLUGIN_RANDSTRUCT
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bool "Randomize layout of sensitive kernel structures"
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select MODVERSIONS if MODULES
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help
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If you say Y here, the layouts of structures that are entirely
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function pointers (and have not been manually annotated with
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__no_randomize_layout), or structures that have been explicitly
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marked with __randomize_layout, will be randomized at compile-time.
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This can introduce the requirement of an additional information
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exposure vulnerability for exploits targeting these structure
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types.
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Enabling this feature will introduce some performance impact,
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slightly increase memory usage, and prevent the use of forensic
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tools like Volatility against the system (unless the kernel
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source tree isn't cleaned after kernel installation).
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The seed used for compilation is located at
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scripts/gcc-plgins/randomize_layout_seed.h. It remains after
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a make clean to allow for external modules to be compiled with
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the existing seed and will be removed by a make mrproper or
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make distclean.
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Note that the implementation requires gcc 4.7 or newer.
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This plugin was ported from grsecurity/PaX. More information at:
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* https://grsecurity.net/
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* https://pax.grsecurity.net/
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config GCC_PLUGIN_RANDSTRUCT_PERFORMANCE
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bool "Use cacheline-aware structure randomization"
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depends on GCC_PLUGIN_RANDSTRUCT
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depends on !COMPILE_TEST # do not reduce test coverage
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help
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If you say Y here, the RANDSTRUCT randomization will make a
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best effort at restricting randomization to cacheline-sized
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groups of elements. It will further not randomize bitfields
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in structures. This reduces the performance hit of RANDSTRUCT
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at the cost of weakened randomization.
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config GCC_PLUGIN_ARM_SSP_PER_TASK
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bool
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depends on GCC_PLUGINS && ARM
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endif
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