On Fri, Jun 27, 2025 at 06:46:56AM +0000, Berg, Benjamin wrote: > On Fri, 2025-06-27 at 06:48 +0200, Thomas Weißschuh wrote: > > On Thu, Jun 26, 2025 at 09:57:13PM +0200, Benjamin Berg wrote: > > > From: Benjamin Berg <benjamin.b...@intel.com> > > > > > > In preparation to add tests that use it. > > > > I tried to implement signal support in nolibc before but ran into some > > issues. > > Unfortunately I don't remember the details. > > But I guess you know more about signals than me, so let's try it again. > > In any case this should add some tests to > > tools/testing/selftests/nolibc/nolibc-test.c. > > > > If you test it with qemu-user please be aware that there were issues around > > SA_RESTORER up until recently [0] [1]. > > Oh, is there a convenient way to cross-compile for various > architectures and run them using qemu? > > So far I only tried x86/x86_64.
We have a script for that in the nolibc testsuite: $ cd tools/testing/selftests/nolibc/ $ ./run-tests.sh -p -m user i386: 225 test(s): 222 passed, 3 skipped, 0 failed => status: warning x86_64: 225 test(s): 222 passed, 3 skipped, 0 failed => status: warning arm64: 225 test(s): 222 passed, 3 skipped, 0 failed => status: warning ... "-p" downloads a bunch of toolchains from kernel.org "-m user" uses qemu-user. "-m system", or no "-m" at all would build a kernel and use qemu-system. "-l" will use llvm/clang instead of gcc (only use with "-m user"). Actual tests are in nolibc-test.c. > > > > [1] > > https://lore.kernel.org/qemu-devel/20250202-riscv-sa-restorer-v1-1-6f4bf814a...@t-8ch.de/ > > [0] https://lore.kernel.org/qemu-devel/mvmed060xc9....@suse.de/ > > > > > > > > Signed-off-by: Benjamin Berg <benjamin.b...@intel.com> > > > --- > > > tools/include/nolibc/nolibc.h | 3 +++ > > > tools/include/nolibc/signal.h | 34 ++++++++++++++++++++++++++++++++++ > > > 2 files changed, 37 insertions(+) > > > > > > diff --git a/tools/include/nolibc/nolibc.h b/tools/include/nolibc/nolibc.h > > > index c199ade200c2..29e37a755aba 100644 > > > --- a/tools/include/nolibc/nolibc.h > > > +++ b/tools/include/nolibc/nolibc.h > > > @@ -92,6 +92,9 @@ > > > #ifndef _NOLIBC_H > > > #define _NOLIBC_H > > > > > > +/* So that we do not get compatibility types/defines */ > > > +#define __KERNEL__ > > > > Could you explain this more? > > > > The user may have included kernel UAPI headers already before including > > nolibc, > > so it doesn't really work. > > Maybe we should just set it in the CFLAGS directly then? We also don't control the CFLAGS the user is using. > Honestly, I am not entirely sure how you are supposed to do it > correctly. The thing is, if I do not set __KERNEL__, then I get the old > compatibility defines and types from asm/signal.h. > > And, I do not see an alternative way. It would not be safe to avoid the > include entirely and if you try that you are also missing the > SA_RESTORER define for the proper "struct sigaction" definition to be > correct. > > The best alternative I see would be copying the proper definitions into > the architecture specific header. That would also be ugly, as one would > need to do a "struct sigaction" -> "struct nolibc_rt_sigaction" > conversion internally. But, that would have the advantage that nolibc > works outside of the kernel tree. I think we need to do something like this. Luckily the real mess seems to be only on x86. > Even if all this is ugly, I would prefer that over using the > compatibility sigaction syscall instead of rt_sigaction. As an alternative, you are not forced to use nolibc for the KUnit UAPI framework. You can depend on CONFIG_CC_CAN_LINK_STATIC=y and use "-static" for the toolchains "real" libc. Not that I want to discourage you from contributing to nolibc, though. > > > + > > > #include "std.h" > > > #include "arch.h" > > > #include "types.h" > > > diff --git a/tools/include/nolibc/signal.h b/tools/include/nolibc/signal.h > > > index ac13e53ac31d..fa52119e577f 100644 > > > --- a/tools/include/nolibc/signal.h > > > +++ b/tools/include/nolibc/signal.h > > > @@ -14,6 +14,7 @@ > > > #include "arch.h" > > > #include "types.h" > > > #include "sys.h" > > > +#include <linux/signal.h> > > > > > > /* This one is not marked static as it's needed by libgcc for divide by > > > zero */ > > > int raise(int signal); > > > @@ -23,4 +24,37 @@ int raise(int signal) > > > return sys_kill(sys_getpid(), signal); > > > } > > > > > > +/* > > > + * sigaction(int signum, const struct sigaction *act, struct sigaction > > > *oldact) > > > + */ > > > + > > > +#ifdef SA_RESTORER > > > +__attribute__((naked)) > > > > __attribute__((naked)) is not supported everywhere. > > One can just drop it. It just felt it was cleaner as we really just > want to set the register and do the syscall without modifying the > stack. If it works without, also good. If you want you can also use __nolibc_has_attribute(naked) from compiler.h. <snip>
