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2018-06-15kconfig: tinyconfig: remove stale stack protector fixupsMasahiro Yamada
Prior to commit 2a61f4747eea ("stack-protector: test compiler capability in Kconfig and drop AUTO mode"), the stack protector was configured by the choice of NONE, REGULAR, STRONG, AUTO. tiny.config needed to explicitly set NONE because the default value of choice, AUTO, did not produce the tiniest kernel. Now that there are only two boolean symbols, STACKPROTECTOR and STACKPROTECTOR_STRONG, they are naturally disabled by "make allnoconfig", which "make tinyconfig" is based on. Remove unnecessary lines from the tiny.config fragment file. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> Acked-by: Kees Cook <keescook@chromium.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-02-06Makefile: introduce CONFIG_CC_STACKPROTECTOR_AUTOKees Cook
Nearly all modern compilers support a stack-protector option, and nearly all modern distributions enable the kernel stack-protector, so enabling this by default in kernel builds would make sense. However, Kconfig does not have knowledge of available compiler features, so it isn't safe to force on, as this would unconditionally break builds for the compilers or architectures that don't have support. Instead, this introduces a new option, CONFIG_CC_STACKPROTECTOR_AUTO, which attempts to discover the best possible stack-protector available, and will allow builds to proceed even if the compiler doesn't support any stack-protector. This option is made the default so that kernels built with modern compilers will be protected-by-default against stack buffer overflows, avoiding things like the recent BlueBorne attack. Selection of a specific stack-protector option remains available, including disabling it. Additionally, tiny.config is adjusted to use CC_STACKPROTECTOR_NONE, since that's the option with the least code size (and it used to be the default, so we have to explicitly choose it there now). Link: http://lkml.kernel.org/r/1510076320-69931-4-git-send-email-keescook@chromium.org Signed-off-by: Kees Cook <keescook@chromium.org> Tested-by: Laura Abbott <labbott@redhat.com> Cc: Masahiro Yamada <yamada.masahiro@socionext.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Josh Triplett <josh@joshtriplett.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-09-01kconfig: tinyconfig: provide whole choice blocks to avoid warningsArnd Bergmann
Using "make tinyconfig" produces a couple of annoying warnings that show up for build test machines all the time: .config:966:warning: override: NOHIGHMEM changes choice state .config:965:warning: override: SLOB changes choice state .config:963:warning: override: KERNEL_XZ changes choice state .config:962:warning: override: CC_OPTIMIZE_FOR_SIZE changes choice state .config:933:warning: override: SLOB changes choice state .config:930:warning: override: CC_OPTIMIZE_FOR_SIZE changes choice state .config:870:warning: override: SLOB changes choice state .config:868:warning: override: KERNEL_XZ changes choice state .config:867:warning: override: CC_OPTIMIZE_FOR_SIZE changes choice state I've made a previous attempt at fixing them and we discussed a number of alternatives. I tried changing the Makefile to use "merge_config.sh -n $(fragment-list)" but couldn't get that to work properly. This is yet another approach, based on the observation that we do want to see a warning for conflicting 'choice' options, and that we can simply make them non-conflicting by listing all other options as disabled. This is a trivial patch that we can apply independent of plans for other changes. Link: http://lkml.kernel.org/r/20160829214952.1334674-2-arnd@arndb.de Link: https://storage.kernelci.org/mainline/v4.7-rc6/x86-tinyconfig/build.log https://patchwork.kernel.org/patch/9212749/ Signed-off-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Josh Triplett <josh@joshtriplett.org> Reviewed-by: Masahiro Yamada <yamada.masahiro@socionext.com> Acked-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-08-08x86: Add "make tinyconfig" to configure the tiniest possible kernelJosh Triplett
Since commit 5d2acfc7b974bbd3858b4dd3f2cdc6362dd8843a ("kconfig: make allnoconfig disable options behind EMBEDDED and EXPERT") in 3.15-rc1, "make allnoconfig" disables every possible config option. However, a few configuration options (CC_OPTIMIZE_FOR_SIZE, OPTIMIZE_INLINING) produce a smaller kernel when turned on, and a few choices exist (compression, highmem, allocator) for which a non-default option produces a smaller kernel. Add a "tinyconfig" option, which starts from allnoconfig and then sets these options to configure the tiniest possible kernel. This provides a better baseline for embedded systems or efforts to reduce kernel size. Signed-off-by: Josh Triplett <josh@joshtriplett.org>