From: Waldemar Kozaczuk <jwkozac...@gmail.com> Committer: Waldemar Kozaczuk <jwkozac...@gmail.com> Branch: master
sigaction: handle null sa_sigaction as SIG_DFL As the comment of the issue #1047 - https://github.com/cloudius-systems/osv/issues/1047#issuecomment-846535939 - explains, Linux treats null value of the sa_sigaction parameter of the sigaction() function as SIG_DFL even if SA_SIGINFO is set per sa_flags parameter. This behavior does not seem to be standard as this stack overflow - https://stackoverflow.com/questions/24079875/what-does-it-mean-if-sa-sigaction-is-set-to-null-when-calling-sigaction - explains and probably stems from the fact that both sa_sigaction and sa_handler are fields of the same union. The above means, that if sa_sigaction is null we should treat it the same same as if sa_handler == SIG_DFL and invoke default signal handler if any when corresponding signal arrived. To that effect this patch refines is_sig_dfl() helper function to implemented the expected behavior. Finally this patch adds new test - tst-sigaction.cc - that can be built and run on both Linux and OSv to verify the same handling of null sa_sigaction. Ideally, we would have wanted to expand existing tst-kill.cc test, however we need a separate test to verify the default action to terminate the app when SIGTERM is received is testable. Fixes #1047 Signed-off-by: Waldemar Kozaczuk <jwkozac...@gmail.com> --- diff --git a/libc/signal.cc b/libc/signal.cc --- a/libc/signal.cc +++ b/libc/signal.cc @@ -57,7 +57,11 @@ sigset* thread_signals(sched::thread *t) } inline bool is_sig_dfl(const struct sigaction &sa) { - return (!(sa.sa_flags & SA_SIGINFO) && sa.sa_handler == SIG_DFL); + if (sa.sa_flags & SA_SIGINFO) { + return sa.sa_sigaction == nullptr; // a non-standard Linux extension + } else { + return sa.sa_handler == SIG_DFL; + } } inline bool is_sig_ign(const struct sigaction &sa) { diff --git a/modules/tests/Makefile b/modules/tests/Makefile --- a/modules/tests/Makefile +++ b/modules/tests/Makefile @@ -111,7 +111,8 @@ tests := tst-pthread.so misc-ramdisk.so tst-vblk.so tst-bsd-evh.so \ tst-calloc.so tst-crypt.so tst-non-fpic.so tst-small-malloc.so \ tst-getopt.so tst-getopt-pie.so tst-non-pie.so tst-semaphore.so \ tst-elf-init.so tst-realloc.so tst-setjmp.so \ - libtls.so libtls_gold.so tst-tls.so tst-tls-gold.so tst-tls-pie.so + libtls.so libtls_gold.so tst-tls.so tst-tls-gold.so tst-tls-pie.so \ + tst-sigaction.so # libstatic-thread-variable.so tst-static-thread-variable.so \ #TODO For now let us disable these tests for aarch64 until diff --git a/tests/tst-sigaction.cc b/tests/tst-sigaction.cc --- a/tests/tst-sigaction.cc +++ b/tests/tst-sigaction.cc @@ -0,0 +1,43 @@ +/* + * Copyright (C) 2021 Waldemar Kozaczuk + * + * This work is open source software, licensed under the terms of the + * BSD license as described in the LICENSE file in the top-level directory. + */ +// To compile on Linux, use: g++ -std=c++11 tests/tst-sigaction.cc +#include <stdio.h> +#include <unistd.h> +#include <signal.h> +#include <cassert> + +static int global = 0; +void test_handler(int sig, siginfo_t *info, void *ucontext) +{ + printf("test_handler called, sig=%d, global=%d\n", sig, global); + global = 1; +} + +void test_sigaction_with_handler(void (*handler)(int, siginfo_t *, void *)) +{ + struct sigaction act = {}; + act.sa_flags = SA_SIGINFO; + sigemptyset(&act.sa_mask); + act.sa_sigaction = handler; + assert(0 == sigaction(SIGTERM, &act, nullptr)); + assert(0 == kill(getpid(), SIGTERM)); +} + +int main(int ac, char** av) +{ + test_sigaction_with_handler(test_handler); + for(int i = 0; i < 100; i++){ + if(global == 1) break; + usleep(10000); + } + assert(global == 1); + printf("global now 1, test_handler called\n"); + + test_sigaction_with_handler(nullptr); + sleep(1); + assert(0); //We should not get here as the app and OSv should have already terminated by this time +} -- You received this message because you are subscribed to the Google Groups "OSv Development" group. To unsubscribe from this group and stop receiving emails from it, send an email to osv-dev+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/osv-dev/000000000000b9e19405c41fb5c2%40google.com.
