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2019-03-04gcc-plugins: structleak: Generalize to all variable typesKees Cook1-0/+2
This adjusts structleak to also work with non-struct types when they are passed by reference, since those variables may leak just like anything else. This is exposed via an improved set of Kconfig options. (This does mean structleak is slightly misnamed now.) Building with CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL should give the kernel complete initialization coverage of all stack variables passed by reference, including padding (see lib/test_stackinit.c). Using CONFIG_GCC_PLUGIN_STRUCTLEAK_VERBOSE to count added initializations under defconfig: ..._BYREF: 5945 added initializations ..._BYREF_ALL: 16606 added initializations There is virtually no change to text+data size (both have less than 0.05% growth): text data bss dec hex filename 19502103 5051456 1917000 26470559 193e89f vmlinux.stock 19513412 5051456 1908808 26473676 193f4cc vmlinux.byref 19516974 5047360 1900616 26464950 193d2b6 vmlinux.byref_all The measured performance difference is in the noise for hackbench and kernel build benchmarks: Stock: 5x hackbench -g 20 -l 1000 Mean: 10.649s Std Dev: 0.339 5x kernel build (4-way parallel) Mean: 261.98s Std Dev: 1.53 CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF: 5x hackbench -g 20 -l 1000 Mean: 10.540s Std Dev: 0.233 5x kernel build (4-way parallel) Mean: 260.52s Std Dev: 1.31 CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL: 5x hackbench -g 20 -l 1000 Mean: 10.320 Std Dev: 0.413 5x kernel build (4-way parallel) Mean: 260.10 Std Dev: 0.86 This does not yet solve missing padding initialization for structures on the stack that are never passed by reference (which should be a tiny minority). Hopefully this will be more easily addressed by upstream compiler fixes after clarifying the C11 padding initialization specification. Signed-off-by: Kees Cook <keescook@chromium.org> Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
2018-12-29Merge tag 'kbuild-v4.21' of ↵Linus Torvalds1-8/+0
git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild Pull Kbuild updates from Masahiro Yamada: "Kbuild core: - remove unneeded $(call cc-option,...) switches - consolidate Clang compiler flags into CLANG_FLAGS - announce the deprecation of SUBDIRS - fix single target build for external module - simplify the dependencies of 'prepare' stage targets - allow fixdep to directly write to .*.cmd files - simplify dependency generation for CONFIG_TRIM_UNUSED_KSYMS - change if_changed_rule to accept multi-line recipe - move .SECONDARY special target to scripts/Kbuild.include - remove redundant 'set -e' - improve parallel execution for CONFIG_HEADERS_CHECK - misc cleanups Treewide fixes and cleanups - set Clang flags correctly for PowerPC boot images - fix UML build error with CONFIG_GCC_PLUGINS - remove unneeded patterns from .gitignore files - refactor firmware/Makefile - remove unneeded rules for *offsets.s - avoid unneeded regeneration of intermediate .s files - clean up ./Kbuild Modpost: - remove unused -M, -K options - fix false positive warnings about section mismatch - use simple devtable lookup instead of linker magic - misc cleanups Coccinelle: - relax boolinit.cocci checks for overall consistency - fix warning messages of boolinit.cocci Other tools: - improve -dirty check of scripts/setlocalversion - add a tool to generate compile_commands.json from .*.cmd files" * tag 'kbuild-v4.21' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (51 commits) kbuild: remove unused cmd_gentimeconst kbuild: remove $(obj)/ prefixes in ./Kbuild treewide: add intermediate .s files to targets treewide: remove explicit rules for *offsets.s firmware: refactor firmware/Makefile firmware: remove unnecessary patterns from .gitignore scripts: remove unnecessary ihex2fw and check-lc_ctypes from .gitignore um: remove unused filechk_gen_header in Makefile scripts: add a tool to produce a compile_commands.json file kbuild: add -Werror=implicit-int flag unconditionally kbuild: add -Werror=strict-prototypes flag unconditionally kbuild: add -fno-PIE flag unconditionally scripts: coccinelle: Correct warning message scripts: coccinelle: only suggest true/false in files that already use them kbuild: handle part-of-module correctly for *.ll and *.symtypes kbuild: refactor part-of-module kbuild: refactor quiet_modtag kbuild: remove redundant quiet_modtag for $(obj-m) kbuild: refactor Makefile.asm-generic user/Makefile: Fix typo and capitalization in comment section ...
2018-12-13ARM: smp: add support for per-task stack canariesArd Biesheuvel1-0/+6
On ARM, we currently only change the value of the stack canary when switching tasks if the kernel was built for UP. On SMP kernels, this is impossible since the stack canary value is obtained via a global symbol reference, which means a) all running tasks on all CPUs must use the same value b) we can only modify the value when no kernel stack frames are live on any CPU, which is effectively never. So instead, use a GCC plugin to add a RTL pass that replaces each reference to the address of the __stack_chk_guard symbol with an expression that produces the address of the 'stack_canary' field that is added to struct thread_info. This way, each task will use its own randomized value. Cc: Russell King <linux@armlinux.org.uk> Cc: Kees Cook <keescook@chromium.org> Cc: Emese Revfy <re.emese@gmail.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Laura Abbott <labbott@redhat.com> Cc: kernel-hardening@lists.openwall.com Acked-by: Nicolas Pitre <nico@linaro.org> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Kees Cook <keescook@chromium.org>
2018-12-01kbuild: descend into scripts/gcc-plugins/ via scripts/MakefileMasahiro Yamada1-8/+0
Now that 'archprepare' depends on 'scripts', Kbuild can descend into scripts/gcc-plugins in a more standard way. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> Reviewed-by: Kees Cook <keescook@chromium.org>
2018-09-04gcc-plugins: Add STACKLEAK plugin for tracking the kernel stackAlexander Popov1-0/+10
The STACKLEAK feature erases the kernel stack before returning from syscalls. That reduces the information which kernel stack leak bugs can reveal and blocks some uninitialized stack variable attacks. This commit introduces the STACKLEAK gcc plugin. It is needed for tracking the lowest border of the kernel stack, which is important for the code erasing the used part of the kernel stack at the end of syscalls (comes in a separate commit). The STACKLEAK feature is ported from grsecurity/PaX. More information at: https://grsecurity.net/ https://pax.grsecurity.net/ This code is modified from Brad Spengler/PaX Team's code in the last public patch of grsecurity/PaX based on our understanding of the code. Changes or omissions from the original code are ours and don't reflect the original grsecurity/PaX code. Signed-off-by: Alexander Popov <alex.popov@linux.com> Tested-by: Laura Abbott <labbott@redhat.com> Signed-off-by: Kees Cook <keescook@chromium.org>
2018-07-25gcc-plugins: Regularize Makefile.gcc-pluginsKees Cook1-12/+24
The layout of Makefile.gcc-plugins had uneven tabs, and the long names of things made this file a bit hard to quickly visually parse. This breaks lines and moves options to the same tab depth. While we're at it, this also adds some comments about the various sections. Signed-off-by: Kees Cook <keescook@chromium.org>
2018-07-03gcc-plugins: remove unused GCC_PLUGIN_SUBDIRMasahiro Yamada1-2/+1
GCC_PLUGIN_SUBDIR has never been used. If you really need this in the future, please re-add it then. For now, the code is unused. Remove. 'export HOSTLIBS' is not necessary either. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> Signed-off-by: Kees Cook <keescook@chromium.org>
2018-06-11gcc-plugins: test plugin support in Kconfig and clean up MakefileMasahiro Yamada1-57/+22
Run scripts/gcc-plugin.sh from Kconfig so that users can enable GCC_PLUGINS only when the compiler supports building plugins. Kconfig defines a new symbol, PLUGIN_HOSTCC. This will contain the compiler (g++ or gcc) used for building plugins, or empty if the plugin can not be supported at all. This allows us to remove all ugly testing in Makefile.gcc-plugins. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> Acked-by: Kees Cook <keescook@chromium.org>
2018-06-11gcc-plugins: move GCC version check for PowerPC to KconfigMasahiro Yamada1-8/+0
For PowerPC, GCC 5.2 is the requirement for GCC plugins. Move the version check to Kconfig so that the GCC plugin menus will be hidden if an older compiler is in use. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> Acked-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com> Reviewed-by: Kees Cook <keescook@chromium.org>
2018-06-11kcov: test compiler capability in Kconfig and correct dependencyMasahiro Yamada1-6/+2
As Documentation/kbuild/kconfig-language.txt notes, 'select' should be be used with care - it forces a lower limit of another symbol, ignoring the dependency. Currently, KCOV can select GCC_PLUGINS even if arch does not select HAVE_GCC_PLUGINS. This could cause the unmet direct dependency. Now that Kconfig can test compiler capability, let's handle this in a more sophisticated way. There are two ways to enable KCOV; use the compiler that natively supports -fsanitize-coverage=trace-pc, or build the SANCOV plugin if the compiler has ability to build GCC plugins. Hence, the correct dependency for KCOV is: depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS You do not need to build the SANCOV plugin if the compiler already supports -fsanitize-coverage=trace-pc. Hence, the select should be: select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC With this, GCC_PLUGIN_SANCOV is selected only when necessary, so scripts/Makefile.gcc-plugins can be cleaner. I also cleaned up Kconfig and scripts/Makefile.kcov as well. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> Reviewed-by: Kees Cook <keescook@chromium.org>
2018-05-05gcc-plugins: fix build condition of SANCOV pluginMasahiro Yamada1-1/+1
Since commit d677a4d60193 ("Makefile: support flag -fsanitizer-coverage=trace-cmp"), you miss to build the SANCOV plugin under some circumstances. CONFIG_KCOV=y CONFIG_KCOV_ENABLE_COMPARISONS=y Your compiler does not support -fsanitize-coverage=trace-pc Your compiler does not support -fsanitize-coverage=trace-cmp Under this condition, $(CFLAGS_KCOV) is not empty but contains a space, so the following ifeq-conditional is false. ifeq ($(CFLAGS_KCOV),) Then, scripts/Makefile.gcc-plugins misses to add sancov_plugin.so to gcc-plugin-y while the SANCOV plugin is necessary as an alternative means. Fixes: d677a4d60193 ("Makefile: support flag -fsanitizer-coverage=trace-cmp") Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> Acked-by: Kees Cook <keescook@chromium.org>
2017-11-02License cleanup: add SPDX GPL-2.0 license identifier to files with no licenseGreg Kroah-Hartman1-0/+1
Many source files in the tree are missing licensing information, which makes it harder for compliance tools to determine the correct license. By default all files without license information are under the default license of the kernel, which is GPL version 2. Update the files which contain no license information with the 'GPL-2.0' SPDX license identifier. The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. This patch is based on work done by Thomas Gleixner and Kate Stewart and Philippe Ombredanne. How this work was done: Patches were generated and checked against linux-4.14-rc6 for a subset of the use cases: - file had no licensing information it it. - file was a */uapi/* one with no licensing information in it, - file was a */uapi/* one with existing licensing information, Further patches will be generated in subsequent months to fix up cases where non-standard license headers were used, and references to license had to be inferred by heuristics based on keywords. The analysis to determine which SPDX License Identifier to be applied to a file was done in a spreadsheet of side by side results from of the output of two independent scanners (ScanCode & Windriver) producing SPDX tag:value files created by Philippe Ombredanne. Philippe prepared the base worksheet, and did an initial spot review of a few 1000 files. The 4.13 kernel was the starting point of the analysis with 60,537 files assessed. Kate Stewart did a file by file comparison of the scanner results in the spreadsheet to determine which SPDX license identifier(s) to be applied to the file. She confirmed any determination that was not immediately clear with lawyers working with the Linux Foundation. Criteria used to select files for SPDX license identifier tagging was: - Files considered eligible had to be source code files. - Make and config files were included as candidates if they contained >5 lines of source - File already had some variant of a license header in it (even if <5 lines). All documentation files were explicitly excluded. The following heuristics were used to determine which SPDX license identifiers to apply. - when both scanners couldn't find any license traces, file was considered to have no license information in it, and the top level COPYING file license applied. For non */uapi/* files that summary was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 11139 and resulted in the first patch in this series. If that file was a */uapi/* path one, it was "GPL-2.0 WITH Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 WITH Linux-syscall-note 930 and resulted in the second patch in this series. - if a file had some form of licensing information in it, and was one of the */uapi/* ones, it was denoted with the Linux-syscall-note if any GPL family license was found in the file or had no licensing in it (per prior point). Results summary: SPDX license identifier # files ---------------------------------------------------|------ GPL-2.0 WITH Linux-syscall-note 270 GPL-2.0+ WITH Linux-syscall-note 169 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17 LGPL-2.1+ WITH Linux-syscall-note 15 GPL-1.0+ WITH Linux-syscall-note 14 ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5 LGPL-2.0+ WITH Linux-syscall-note 4 LGPL-2.1 WITH Linux-syscall-note 3 ((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3 ((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1 and that resulted in the third patch in this series. - when the two scanners agreed on the detected license(s), that became the concluded license(s). - when there was disagreement between the two scanners (one detected a license but the other didn't, or they both detected different licenses) a manual inspection of the file occurred. - In most cases a manual inspection of the information in the file resulted in a clear resolution of the license that should apply (and which scanner probably needed to revisit its heuristics). - When it was not immediately clear, the license identifier was confirmed with lawyers working with the Linux Foundation. - If there was any question as to the appropriate license identifier, the file was flagged for further research and to be revisited later in time. In total, over 70 hours of logged manual review was done on the spreadsheet to determine the SPDX license identifiers to apply to the source files by Kate, Philippe, Thomas and, in some cases, confirmation by lawyers working with the Linux Foundation. Kate also obtained a third independent scan of the 4.13 code base from FOSSology, and compared selected files where the other two scanners disagreed against that SPDX file, to see if there was new insights. The Windriver scanner is based on an older version of FOSSology in part, so they are related. Thomas did random spot checks in about 500 files from the spreadsheets for the uapi headers and agreed with SPDX license identifier in the files he inspected. For the non-uapi files Thomas did random spot checks in about 15000 files. In initial set of patches against 4.14-rc6, 3 files were found to have copy/paste license identifier errors, and have been fixed to reflect the correct identifier. Additionally Philippe spent 10 hours this week doing a detailed manual inspection and review of the 12,461 patched files from the initial patch version early this week with: - a full scancode scan run, collecting the matched texts, detected license ids and scores - reviewing anything where there was a license detected (about 500+ files) to ensure that the applied SPDX license was correct - reviewing anything where there was no detection but the patch license was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied SPDX license was correct This produced a worksheet with 20 files needing minor correction. This worksheet was then exported into 3 different .csv files for the different types of files to be modified. These .csv files were then reviewed by Greg. Thomas wrote a script to parse the csv files and add the proper SPDX tag to the file, in the format that the file expected. This script was further refined by Greg based on the output to detect more types of files automatically and to distinguish between header and source .c files (which need different comment types.) Finally Greg ran the script using the .csv files to generate the patches. Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org> Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-08-07gcc-plugins: structleak: add option to init all vars used as byref argsArd Biesheuvel1-0/+1
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: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Kees Cook <keescook@chromium.org>
2017-06-23gcc-plugins: Add the randstruct pluginKees Cook1-0/+4
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: Kees Cook <keescook@chromium.org>
2017-02-22Merge tag 'powerpc-4.11-1' of ↵Linus Torvalds1-1/+9
git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux Pull powerpc updates from Michael Ellerman: "Highlights include: - Support for direct mapped LPC on POWER9, giving Linux direct access to devices that may be on there such as a UART. - Memory hotplug support for the Power9 Radix MMU. - Add new AUX vectors describing the processor's cache geometry, to be used by glibc. - The ability for a guest to ask the hypervisor to resize the guest's hash table, and in addition support for doing so automatically when memory is hotplugged into/out-of the guest. This allows the hash table to be sized based on the current memory usage of the guest, rather than the maximum possible memory usage. - Implementation of optprobes (kprobe optimisation) for powerpc. In addition there's the topic branch shared with the KVM tree, which includes support for guests to use the Radix MMU on Power9. Thanks to: Alistair Popple, Andrew Donnellan, Aneesh Kumar K.V, Anju T, Anton Blanchard, Benjamin Herrenschmidt, Chris Packham, Daniel Axtens, Daniel Borkmann, David Gibson, Finn Thain, Gautham R. Shenoy, Gavin Shan, Greg Kurz, Joel Stanley, John Allen, Madhavan Srinivasan, Mahesh Salgaonkar, Markus Elfring, Michael Neuling, Nathan Fontenot, Naveen N. Rao, Nicholas Piggin, Paul Mackerras, Ravi Bangoria, Reza Arbab, Shailendra Singh, Vaibhav Jain, Wei Yongjun" * tag 'powerpc-4.11-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux: (129 commits) powerpc/mm/radix: Skip ptesync in pte update helpers powerpc/mm/radix: Use ptep_get_and_clear_full when clearing pte for full mm powerpc/mm/radix: Update pte update sequence for pte clear case powerpc/mm: Update PROTFAULT handling in the page fault path powerpc/xmon: Fix data-breakpoint powerpc/mm: Fix build break with BOOK3S_64=n and MEMORY_HOTPLUG=y powerpc/mm: Fix build break when CMA=n && SPAPR_TCE_IOMMU=y powerpc/mm: Fix build break with RADIX=y & HUGETLBFS=n powerpc/pseries: Fix typo in parameter description powerpc/kprobes: Remove kprobe_exceptions_notify() kprobes: Introduce weak variant of kprobe_exceptions_notify() powerpc/ftrace: Fix confusing help text for DISABLE_MPROFILE_KERNEL powerpc/powernv: Fix opal_exit tracepoint opcode powerpc: Add a prototype for mcount() so it can be versioned powerpc: Drop GPL from of_node_to_nid() export to match other arches powerpc/kprobes: Optimize kprobe in kretprobe_trampoline() powerpc/kprobes: Implement Optprobes powerpc/kprobes: Fixes for kprobe_lookup_name() on BE powerpc: Add helper to check if offset is within relative branch range powerpc/bpf: Introduce __PPC_SH64() ...
2017-02-03powerpc: Enable support for GCC pluginsAndrew Donnellan1-0/+8
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: Andrew Donnellan <andrew.donnellan@au1.ibm.com> Acked-by: Kees Cook <keescook@chromium.org> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
2017-02-03gcc-plugins: Fix definition of DISABLE_LATENT_ENTROPY_PLUGINAndrew Donnellan1-1/+1
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: 38addce8b600 ("gcc-plugins: Add latent_entropy plugin") Signed-off-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
2017-01-18gcc-plugins: Add structleak for more stack initializationKees Cook1-0/+4
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: Kees Cook <keescook@chromium.org>
2016-10-11gcc-plugins: Add latent_entropy pluginEmese Revfy1-1/+8
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: Emese Revfy <re.emese@gmail.com> [kees: expanded commit message and code comments] Signed-off-by: Kees Cook <keescook@chromium.org>
2016-08-09gcc-plugins: Add support for plugin subdirectoriesEmese Revfy1-1/+2
This adds support for building more complex gcc plugins that live in a subdirectory instead of just in a single source file. Reported-by: PaX Team <pageexec@freemail.hu> Signed-off-by: Emese Revfy <re.emese@gmail.com> [kees: clarified commit message] Signed-off-by: Kees Cook <keescook@chromium.org>
2016-08-09gcc-plugins: Add support for passing plugin argumentsEmese Revfy1-1/+1
The latent_entropy plugin needs to pass arguments, so this adds the support. Signed-off-by: Emese Revfy <re.emese@gmail.com> Signed-off-by: Kees Cook <keescook@chromium.org>
2016-08-09gcc-plugins: abort builds cleanly when not supportedKees Cook1-9/+25
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: Kees Cook <keescook@chromium.org>
2016-06-07Add sancov pluginEmese Revfy1-1/+20
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: Emese Revfy <re.emese@gmail.com> Acked-by: Kees Cook <keescook@chromium.org> Signed-off-by: Michal Marek <mmarek@suse.com>
2016-06-07Add Cyclomatic complexity GCC pluginEmese Revfy1-0/+1
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: Emese Revfy <re.emese@gmail.com> Acked-by: Kees Cook <keescook@chromium.org> Signed-off-by: Michal Marek <mmarek@suse.com>
2016-06-07GCC plugin infrastructureEmese Revfy1-0/+23
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: Emese Revfy <re.emese@gmail.com> Acked-by: Kees Cook <keescook@chromium.org> Signed-off-by: Michal Marek <mmarek@suse.com>