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2020-05-17samples: pidfd: build sample program for target architectureMasahiro Yamada
This userspace program includes UAPI headers exported to usr/include/. 'make headers' always works for the target architecture (i.e. the same architecture as the kernel), so the sample program should be built for the target as well. Kbuild now supports 'userprogs' for that. I also guarded the CONFIG option by 'depends on CC_CAN_LINK' because $(CC) may not provide libc. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Acked-by: Sam Ravnborg <sam@ravnborg.org>
2020-03-25.gitignore: add SPDX License IdentifierMasahiro Yamada
Add SPDX License Identifier to all .gitignore files. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-02-04kbuild: rename hostprogs-y/always to hostprogs/always-yMasahiro Yamada
In old days, the "host-progs" syntax was used for specifying host programs. It was renamed to the current "hostprogs-y" in 2004. It is typically useful in scripts/Makefile because it allows Kbuild to selectively compile host programs based on the kernel configuration. This commit renames like follows: always -> always-y hostprogs-y -> hostprogs So, scripts/Makefile will look like this: always-$(CONFIG_BUILD_BIN2C) += ... always-$(CONFIG_KALLSYMS) += ... ... hostprogs := $(always-y) $(always-m) I think this makes more sense because a host program is always a host program, irrespective of the kernel configuration. We want to specify which ones to compile by CONFIG options, so always-y will be handier. The "always", "hostprogs-y", "hostprogs-m" will be kept for backward compatibility for a while. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2019-06-24samples: make pidfd-metadata fail gracefully on older kernelsDmitry V. Levin
Initialize pidfd to an invalid descriptor, to fail gracefully on those kernels that do not implement CLONE_PIDFD and leave pidfd unchanged. Signed-off-by: Dmitry V. Levin <ldv@altlinux.org> Signed-off-by: Christian Brauner <christian@brauner.io>
2019-06-05samples: fix pidfd-metadata compilationGuenter Roeck
Define __NR_pidfd_send_signal if it isn't to prevent a compilation error. To make pidfd-metadata compile on all arches, irrespective of whether or not syscall numbers are assigned, define the syscall number to -1. If it isn't defined this will cause the kernel to return -ENOSYS. Fixes: 43c6afee48d4 ("samples: show race-free pidfd metadata access") Reported-by: Arnd Bergmann <arnd@arndb.de> Reported-by: Guenter Roeck <linux@roeck-us.net> Cc: Christian Brauner <christian@brauner.io> Signed-off-by: Guenter Roeck <linux@roeck-us.net> [christian@brauner.io: tweak commit message] Signed-off-by: Christian Brauner <christian@brauner.io>
2019-05-10samples: add .gitignore for pidfd-metadataChristian Brauner
Ignore the pidfd-metadata binary so it doesn't show up in unwanted scenarios. Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Christian Brauner <christian@brauner.io>
2019-05-07samples: show race-free pidfd metadata accessChristian Brauner
This is a sample program showing userspace how to get race-free access to process metadata from a pidfd. It is rather easy to do and userspace can actually simply reuse code that currently parses a process's status file in procfs. The program can easily be extended into a generic helper suitable for inclusion in a libc to make it even easier for userspace to gain metadata access. Since this came up in a discussion because this API is going to be used in various service managers: A lot of programs will have a whitelist seccomp filter that returns <some-errno> for all new syscalls. This means that programs might get confused if CLONE_PIDFD works but the later pidfd_send_signal() syscall doesn't. Hence, here's a ahead of time check that pidfd_send_signal() is supported: bool pidfd_send_signal_supported() { int procfd = open("/proc/self", O_DIRECTORY | O_RDONLY | O_CLOEXEC); if (procfd < 0) return false; /* * A process is always allowed to signal itself so * pidfd_send_signal() should never fail this test. If it does * it must mean it is not available, blocked by an LSM, seccomp, * or other. */ return pidfd_send_signal(procfd, 0, NULL, 0) == 0; } Signed-off-by: Christian Brauner <christian@brauner.io> Co-developed-by: Jann Horn <jannh@google.com> Signed-off-by: Jann Horn <jannh@google.com> Reviewed-by: Oleg Nesterov <oleg@redhat.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Kees Cook <keescook@chromium.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: David Howells <dhowells@redhat.com> Cc: "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> Cc: Andy Lutomirsky <luto@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Aleksa Sarai <cyphar@cyphar.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Al Viro <viro@zeniv.linux.org.uk>