kernel/linux.git/init/Kconfig, branch v5.4.198

Kconfig: add config option for asm goto w/ outputs

2022-06-14T16:11:50+00:00

commit 587f17018a2c6c414e41a312b002faaef60cf423 upstream. This allows C code to make use of compilers with support for output variables along the fallthrough path via preprocessor define: CONFIG_CC_HAS_ASM_GOTO_OUTPUT [ This is not used anywhere yet, and currently released compilers don't support this yet, but it's coming, and I have some local experimental patches to take advantage of it when it does - Linus ] Signed-off-by: Nick Desaulniers Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

Kconfig: Add option for asm goto w/ tied outputs to workaround clang-13 bug

2022-06-14T16:11:47+00:00

commit 1aa0e8b144b6474c4914439d232d15bfe883636b upstream. Add a config option to guard (future) usage of asm_volatile_goto() that includes "tied outputs", i.e. "+" constraints that specify both an input and output parameter. clang-13 has a bug[1] that causes compilation of such inline asm to fail, and KVM wants to use a "+m" constraint to implement a uaccess form of CMPXCHG[2]. E.g. the test code fails with :1:29: error: invalid operand in inline asm: '.long (${1:l}) - .' int foo(int *x) { asm goto (".long (%l[bar]) - .\n": "+m"(*x) ::: bar); return *x; bar: return 0; } ^ :1:29: error: unknown token in expression :1:9: note: instantiated into assembly here .long () - . ^ 2 errors generated. on clang-13, but passes on gcc (with appropriate asm goto support). The bug is fixed in clang-14, but won't be backported to clang-13 as the changes are too invasive/risky. gcc also had a similar bug[3], fixed in gcc-11, where gcc failed to account for its behavior of assigning two numbers to tied outputs (one for input, one for output) when evaluating symbolic references. [1] https://github.com/ClangBuiltLinux/linux/issues/1512 [2] https://lore.kernel.org/all/YfMruK8%2F1izZ2VHS@google.com [3] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98096 Suggested-by: Nick Desaulniers Reviewed-by: Nick Desaulniers Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson Message-Id: <20220202004945.2540433-2-seanjc@google.com> Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman

bpf: Add kconfig knob for disabling unpriv bpf by default

2022-02-16T11:52:49+00:00

commit 08389d888287c3823f80b0216766b71e17f0aba5 upstream. Add a kconfig knob which allows for unprivileged bpf to be disabled by default. If set, the knob sets /proc/sys/kernel/unprivileged_bpf_disabled to value of 2. This still allows a transition of 2 -> {0,1} through an admin. Similarly, this also still keeps 1 -> {1} behavior intact, so that once set to permanently disabled, it cannot be undone aside from a reboot. We've also added extra2 with max of 2 for the procfs handler, so that an admin still has a chance to toggle between 0 <-> 2. Either way, as an additional alternative, applications can make use of CAP_BPF that we added a while ago. Signed-off-by: Daniel Borkmann Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/74ec548079189e4e4dffaeb42b8987bb3c852eee.1620765074.git.daniel@iogearbox.net [fllinden@amazon.com: backported to 5.4] Signed-off-by: Frank van der Linden Signed-off-by: Greg Kroah-Hartman

kbuild: add CONFIG_LD_IS_LLD

2021-06-30T12:47:44+00:00

commit b744b43f79cc758127042e71f9ad7b1afda30f84 upstream. Similarly to the CC_IS_CLANG config, add LD_IS_LLD to avoid GNU ld specific logic such as ld-version or ld-ifversion and gain the ability to select potential features that depend on the linker at configuration time such as LTO. Signed-off-by: Sami Tolvanen Acked-by: Masahiro Yamada [nc: Reword commit message] Signed-off-by: Nathan Chancellor Tested-by: Sedat Dilek Reviewed-by: Sedat Dilek Signed-off-by: Thomas Bogendoerfer Signed-off-by: Greg Kroah-Hartman

init/Kconfig: make COMPILE_TEST depend on HAS_IOMEM

2021-04-10T11:34:32+00:00

commit ea29b20a828511de3348334e529a3d046a180416 upstream. I read the commit log of the following two: - bc083a64b6c0 ("init/Kconfig: make COMPILE_TEST depend on !UML") - 334ef6ed06fa ("init/Kconfig: make COMPILE_TEST depend on !S390") Both are talking about HAS_IOMEM dependency missing in many drivers. So, 'depends on HAS_IOMEM' seems the direct, sensible solution to me. This does not change the behavior of UML. UML still cannot enable COMPILE_TEST because it does not provide HAS_IOMEM. The current dependency for S390 is too strong. Under the condition of CONFIG_PCI=y, S390 provides HAS_IOMEM, hence can enable COMPILE_TEST. I also removed the meaningless 'default n'. Link: https://lkml.kernel.org/r/20210224140809.1067582-1-masahiroy@kernel.org Signed-off-by: Masahiro Yamada Cc: Heiko Carstens Cc: Guenter Roeck Cc: Arnd Bergmann Cc: Kees Cook Cc: Daniel Borkmann Cc: Johannes Weiner Cc: KP Singh Cc: Nathan Chancellor Cc: Nick Terrell Cc: Quentin Perret Cc: Valentin Schneider Cc: "Enrico Weigelt, metux IT consult" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Cc: Guenter Roeck Signed-off-by: Greg Kroah-Hartman

init/Kconfig: make COMPILE_TEST depend on !S390

2021-04-10T11:34:32+00:00

commit 334ef6ed06fa1a54e35296b77b693bcf6d63ee9e upstream. While allmodconfig and allyesconfig build for s390 there are also various bots running compile tests with randconfig, where PCI is disabled. This reveals that a lot of drivers should actually depend on HAS_IOMEM. Adding this to each device driver would be a never ending story, therefore just disable COMPILE_TEST for s390. The reasoning is more or less the same as described in commit bc083a64b6c0 ("init/Kconfig: make COMPILE_TEST depend on !UML"). Reported-by: kernel test robot Suggested-by: Arnd Bergmann Signed-off-by: Heiko Carstens Cc: Guenter Roeck Signed-off-by: Greg Kroah-Hartman

printk: reduce LOG_BUF_SHIFT range for H8300

2020-11-05T10:43:16+00:00

[ Upstream commit 550c10d28d21bd82a8bb48debbb27e6ed53262f6 ] The .bss section for the h8300 is relatively small. A value of CONFIG_LOG_BUF_SHIFT that is larger than 19 will create a static printk ringbuffer that is too large. Limit the range appropriately for the H8300. Reported-by: kernel test robot Signed-off-by: John Ogness Reviewed-by: Sergey Senozhatsky Acked-by: Steven Rostedt (VMware) Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20200812073122.25412-1-john.ogness@linutronix.de Signed-off-by: Sasha Levin

Stop the ad-hoc games with -Wno-maybe-initialized

2020-05-20T06:20:28+00:00

commit 78a5255ffb6a1af189a83e493d916ba1c54d8c75 upstream. We have some rather random rules about when we accept the "maybe-initialized" warnings, and when we don't. For example, we consider it unreliable for gcc versions < 4.9, but also if -O3 is enabled, or if optimizing for size. And then various kernel config options disabled it, because they know that they trigger that warning by confusing gcc sufficiently (ie PROFILE_ALL_BRANCHES). And now gcc-10 seems to be introducing a lot of those warnings too, so it falls under the same heading as 4.9 did. At the same time, we have a very straightforward way to _enable_ that warning when wanted: use "W=2" to enable more warnings. So stop playing these ad-hoc games, and just disable that warning by default, with the known and straight-forward "if you want to work on the extra compiler warnings, use W=123". Would it be great to have code that is always so obvious that it never confuses the compiler whether a variable is used initialized or not? Yes, it would. In a perfect world, the compilers would be smarter, and our source code would be simpler. That's currently not the world we live in, though. Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

kbuild: remove header compile test

2020-03-05T15:43:47+00:00

commit fcbb8461fd2376ba3782b5b8bd440c929b8e4980 upstream. There are both positive and negative options about this feature. At first, I thought it was a good idea, but actually Linus stated a negative opinion (https://lkml.org/lkml/2019/9/29/227). I admit it is ugly and annoying. The baseline I'd like to keep is the compile-test of uapi headers. (Otherwise, kernel developers have no way to ensure the correctness of the exported headers.) I will maintain a small build rule in usr/include/Makefile. Remove the other header test functionality. Signed-off-by: Masahiro Yamada [ added to 5.4.y due to start of build warnings from backported patches because of this feature - gregkh] Signed-off-by: Greg Kroah-Hartman

Revert "um: Enable CONFIG_CONSTRUCTORS"

2020-02-01T09:34:53+00:00

commit 87c9366e17259040a9118e06b6dc8de986e5d3d1 upstream. This reverts commit 786b2384bf1c ("um: Enable CONFIG_CONSTRUCTORS"). There are two issues with this commit, uncovered by Anton in tests on some (Debian) systems: 1) I completely forgot to call any constructors if CONFIG_CONSTRUCTORS isn't set. Don't recall now if it just wasn't needed on my system, or if I never tested this case. 2) With that fixed, it works - with CONFIG_CONSTRUCTORS *unset*. If I set CONFIG_CONSTRUCTORS, it fails again, which isn't totally unexpected since whatever wanted to run is likely to have to run before the kernel init etc. that calls the constructors in this case. Basically, some constructors that gcc emits (libc has?) need to run very early during init; the failure mode otherwise was that the ptrace fork test already failed: ---------------------- $ ./linux mem=512M Core dump limits : soft - 0 hard - NONE Checking that ptrace can change system call numbers...check_ptrace : child exited with exitcode 6, while expecting 0; status 0x67f Aborted ---------------------- Thinking more about this, it's clear that we simply cannot support CONFIG_CONSTRUCTORS in UML. All the cases we need now (gcov, kasan) involve not use of the __attribute__((constructor)), but instead some constructor code/entry generated by gcc. Therefore, we cannot distinguish between kernel constructors and system constructors. Thus, revert this commit. Cc: stable@vger.kernel.org [5.4+] Fixes: 786b2384bf1c ("um: Enable CONFIG_CONSTRUCTORS") Reported-by: Anton Ivanov Signed-off-by: Johannes Berg Acked-by: Anton Ivanov Signed-off-by: Greg Kroah-Hartman Signed-off-by: Richard Weinberger