preferred-plugin-hostcc := $(if-success,[ $(gcc-version) -ge 40800 ],$(HOSTCXX),$(HOSTCC)) config PLUGIN_HOSTCC string default "$(shell,$(srctree)/scripts/gcc-plugin.sh "$(preferred-plugin-hostcc)" "$(HOSTCXX)" "$(CC)")" if CC_IS_GCC help Host compiler used to build GCC plugins. This can be $(HOSTCXX), $(HOSTCC), or a null string if GCC plugin is unsupported. config HAVE_GCC_PLUGINS bool help An arch should select this symbol if it supports building with GCC plugins. menuconfig GCC_PLUGINS bool "GCC plugins" depends on HAVE_GCC_PLUGINS depends on PLUGIN_HOSTCC != "" help GCC plugins are loadable modules that provide extra features to the compiler. They are useful for runtime instrumentation and static analysis. See Documentation/gcc-plugins.txt for details. if GCC_PLUGINS config GCC_PLUGIN_CYC_COMPLEXITY bool "Compute the cyclomatic complexity of a function" if EXPERT depends on !COMPILE_TEST # too noisy help 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). Enabling this plugin reports the complexity to stderr during the build. It mainly serves as a simple example of how to create a gcc plugin for the kernel. config GCC_PLUGIN_SANCOV bool help This plugin inserts a __sanitizer_cov_trace_pc() call at the start of basic blocks. It supports all gcc versions with plugin support (from gcc-4.5 on). It is based on the commit "Add fuzzing coverage support" by Dmitry Vyukov . config GCC_PLUGIN_LATENT_ENTROPY bool "Generate some entropy during boot and runtime" help By saying Y here the kernel will instrument some kernel code to extract some entropy from both original and artificially created program state. This will help especially embedded systems where there is little 'natural' source of entropy normally. The cost is some slowdown of the boot process (about 0.5%) and fork and irq processing. Note that entropy extracted this way is not cryptographically secure! This plugin was ported from grsecurity/PaX. More information at: * https://grsecurity.net/ * https://pax.grsecurity.net/ config GCC_PLUGIN_STRUCTLEAK bool "Zero initialize stack variables" help While the kernel is built with warnings enabled for any missed stack variable initializations, this warning is silenced for anything passed by reference to another function, under the occasionally misguided assumption that the function will do the initialization. As this regularly leads to exploitable flaws, this plugin is available to identify and zero-initialize such variables, depending on the chosen level of coverage. This plugin was originally ported from grsecurity/PaX. More information at: * https://grsecurity.net/ * https://pax.grsecurity.net/ choice prompt "Coverage" depends on GCC_PLUGIN_STRUCTLEAK default GCC_PLUGIN_STRUCTLEAK_BYREF_ALL help This chooses the level of coverage over classes of potentially uninitialized variables. The selected class will be zero-initialized before use. config GCC_PLUGIN_STRUCTLEAK_USER bool "structs marked for userspace" help Zero-initialize any structures on the stack containing a __user attribute. This can prevent some classes of uninitialized stack variable exploits and information exposures, like CVE-2013-2141: https://git.kernel.org/linus/b9e146d8eb3b9eca config GCC_PLUGIN_STRUCTLEAK_BYREF bool "structs passed by reference" help Zero-initialize any structures on the stack that may be passed by reference and had not already been explicitly initialized. This can prevent most classes of uninitialized stack variable exploits and information exposures, like CVE-2017-1000410: https://git.kernel.org/linus/06e7e776ca4d3654 config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL bool "anything passed by reference" help Zero-initialize any stack variables that may be passed by reference and had not already been explicitly initialized. This is intended to eliminate all classes of uninitialized stack variable exploits and information exposures. endchoice config GCC_PLUGIN_STRUCTLEAK_VERBOSE bool "Report forcefully initialized variables" depends on GCC_PLUGIN_STRUCTLEAK depends on !COMPILE_TEST # too noisy help This option will cause a warning to be printed each time the structleak plugin finds a variable it thinks needs to be initialized. Since not all existing initializers are detected by the plugin, this can produce false positive warnings. config GCC_PLUGIN_RANDSTRUCT bool "Randomize layout of sensitive kernel structures" select MODVERSIONS if MODULES help If you say Y here, the layouts of structures that are entirely function pointers (and have not been manually annotated with __no_randomize_layout), or structures that have been explicitly marked with __randomize_layout, will be randomized at compile-time. This can introduce the requirement of an additional information exposure vulnerability for exploits targeting these structure types. Enabling this feature will introduce some performance impact, slightly increase memory usage, and prevent the use of forensic tools like Volatility against the system (unless the kernel source tree isn't cleaned after kernel installation). The seed used for compilation is located at scripts/gcc-plgins/randomize_layout_seed.h. It remains after a make clean to allow for external modules to be compiled with the existing seed and will be removed by a make mrproper or make distclean. Note that the implementation requires gcc 4.7 or newer. This plugin was ported from grsecurity/PaX. More information at: * https://grsecurity.net/ * https://pax.grsecurity.net/ config GCC_PLUGIN_RANDSTRUCT_PERFORMANCE bool "Use cacheline-aware structure randomization" depends on GCC_PLUGIN_RANDSTRUCT depends on !COMPILE_TEST # do not reduce test coverage help If you say Y here, the RANDSTRUCT randomization will make a best effort at restricting randomization to cacheline-sized groups of elements. It will further not randomize bitfields in structures. This reduces the performance hit of RANDSTRUCT at the cost of weakened randomization. config GCC_PLUGIN_STACKLEAK bool "Erase the kernel stack before returning from syscalls" depends on GCC_PLUGINS depends on HAVE_ARCH_STACKLEAK help This option makes the kernel erase the kernel stack before returning from system calls. That reduces the information which kernel stack leak bugs can reveal and blocks some uninitialized stack variable attacks. The tradeoff is the performance impact: on a single CPU system kernel compilation sees a 1% slowdown, other systems and workloads may vary and you are advised to test this feature on your expected workload before deploying it. This plugin was ported from grsecurity/PaX. More information at: * https://grsecurity.net/ * https://pax.grsecurity.net/ config STACKLEAK_TRACK_MIN_SIZE int "Minimum stack frame size of functions tracked by STACKLEAK" default 100 range 0 4096 depends on GCC_PLUGIN_STACKLEAK help The STACKLEAK gcc plugin instruments the kernel code for tracking the lowest border of the kernel stack (and for some other purposes). It inserts the stackleak_track_stack() call for the functions with a stack frame size greater than or equal to this parameter. If unsure, leave the default value 100. config STACKLEAK_METRICS bool "Show STACKLEAK metrics in the /proc file system" depends on GCC_PLUGIN_STACKLEAK depends on PROC_FS help If this is set, STACKLEAK metrics for every task are available in the /proc file system. In particular, /proc//stack_depth shows the maximum kernel stack consumption for the current and previous syscalls. Although this information is not precise, it can be useful for estimating the STACKLEAK performance impact for your workloads. config STACKLEAK_RUNTIME_DISABLE bool "Allow runtime disabling of kernel stack erasing" depends on GCC_PLUGIN_STACKLEAK help This option provides 'stack_erasing' sysctl, which can be used in runtime to control kernel stack erasing for kernels built with CONFIG_GCC_PLUGIN_STACKLEAK. config GCC_PLUGIN_ARM_SSP_PER_TASK bool depends on GCC_PLUGINS && ARM endif