From patchwork Tue Jun 11 07:43:07 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dev Jain X-Patchwork-Id: 13693196 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 55F051E52F; Tue, 11 Jun 2024 07:43:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718091820; cv=none; b=LlduXIjlG05NwDc8eHinTXf8tCKQaRZpT+k0zKpiv8ntjwMHIoP0TISE656RpxFGaiQzpNAiNHBP5LWBihNfflOhsGSl+CZHDvTQmCn3Gonv3v0NjhD3sBD4iBv5bSCwOjOLtUTEHt6OFiYSQ2YS9qPprK7z2/3/0k02D/9qEoc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718091820; c=relaxed/simple; bh=EQ+NGOw5bXDNjRbB2iyltApn1GO4jcxEvzNNK5bp5lI=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=LNxtAsACotaNpfNjV29/g0qjDF/no8+gtdkVpfADokrbnyjK78GiIUJwSv+c4Y57cuYa1AdRHGyIR0i84mZJcElbe1mvk352ugKMU+OO0tMNgtlqPZNE0PXZVrOCLik8nDMNm7rhJYPiqPfTF0PutFOPMSwIKMspe7p3Bsg2MeA= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 665171516; Tue, 11 Jun 2024 00:44:02 -0700 (PDT) Received: from e116581.blr.arm.com (e116581.arm.com [10.162.41.16]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id B7F0D3F64C; Tue, 11 Jun 2024 00:43:32 -0700 (PDT) From: Dev Jain To: shuah@kernel.org, oleg@redhat.com, stsp2@yandex.ru Cc: mingo@kernel.org, tglx@linutronix.de, mark.rutland@arm.com, ryan.roberts@arm.com, broonie@kernel.org, suzuki.poulose@arm.com, Anshuman.Khandual@arm.com, DeepakKumar.Mishra@arm.com, AneeshKumar.KizhakeVeetil@arm.com, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Dev Jain Subject: [PATCH v2 2/2] selftests: Add a test mangling with uc_sigmask Date: Tue, 11 Jun 2024 13:13:07 +0530 Message-Id: <20240611074307.812939-3-dev.jain@arm.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240611074307.812939-1-dev.jain@arm.com> References: <20240611074307.812939-1-dev.jain@arm.com> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 This test asserts the relation between blocked signal, delivered signal, and ucontext. The ucontext is mangled with, by adding a signal mask to it; on return from the handler, the thread must block the corresponding signal. In the test description, I have also described what it exactly means for a signal to be delivered or blocked, for ease of clarity. Signed-off-by: Dev Jain --- tools/testing/selftests/signal/.gitignore | 1 + tools/testing/selftests/signal/Makefile | 3 +- .../selftests/signal/mangle_uc_sigmask.c | 194 ++++++++++++++++++ 3 files changed, 197 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/signal/mangle_uc_sigmask.c diff --git a/tools/testing/selftests/signal/.gitignore b/tools/testing/selftests/signal/.gitignore index 98a7bbc4f325..397fef11c89f 100644 --- a/tools/testing/selftests/signal/.gitignore +++ b/tools/testing/selftests/signal/.gitignore @@ -1,2 +1,3 @@ # SPDX-License-Identifier: GPL-2.0-only +mangle_uc_sigmask sigaltstack diff --git a/tools/testing/selftests/signal/Makefile b/tools/testing/selftests/signal/Makefile index dd6be992fd81..735387a53114 100644 --- a/tools/testing/selftests/signal/Makefile +++ b/tools/testing/selftests/signal/Makefile @@ -1,6 +1,7 @@ # SPDX-License-Identifier: GPL-2.0-only CFLAGS = -Wall -TEST_GEN_PROGS = sigaltstack +TEST_GEN_PROGS = mangle_uc_sigmask +TEST_GEN_PROGS += sigaltstack include ../lib.mk diff --git a/tools/testing/selftests/signal/mangle_uc_sigmask.c b/tools/testing/selftests/signal/mangle_uc_sigmask.c new file mode 100644 index 000000000000..9d4644106465 --- /dev/null +++ b/tools/testing/selftests/signal/mangle_uc_sigmask.c @@ -0,0 +1,194 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2024 ARM Ltd. + * + * Author: Dev Jain + * + * Test describing a clear distinction between signal states - delivered and + * blocked, and their relation with ucontext. + * + * A signal is said to be delivered, when the program takes action on the + * signal: such action may involve termination of the process, ignoring the + * signal, terminating with core dump, stopping the process, or continuing the + * process if it was currently stopped. A signal is said to be blocked when the + * program refuses to take any of the above actions; note that, this is not the + * same as ignoring the signal. At a later time, the program may unblock the + * signal and then it will have to take one of the five actions + * described above. + * + * We test the following functionalities of the kernel: + * + * ucontext_t describes the current state of the thread; this implies that, in + * case of registering a handler and catching the corresponding signal, that + * state is before what was jumping into the handler. + * + * The thread's mask of blocked signals can be permanently changed, i.e, not + * just during the execution of the handler, by mangling with uc_sigmask + * from inside the handler. + * + * Assume that we block the set of signals, S1, by sigaction(), and say, the + * signal for which the handler was installed, is S2. When S2 is sent to the + * program, it will be considered "delivered", since we will act on the + * signal and jump to the handler. Any instances of S1 or S2 raised, while the + * program is executing inside the handler, will be blocked; they will be + * delivered immediately upon termination of the handler. + * + * For standard signals (also see real-time signals in the man page), multiple + * blocked instances of the same signal are not queued; such a signal will + * be delivered just once. + */ + +#include +#include +#include +#include + +#include "../kselftest.h" + +void handler_verify_ucontext(int signo, siginfo_t *info, void *uc) +{ + int ret; + + /* Kernel dumps ucontext with USR2 blocked */ + ret = sigismember(&(((ucontext_t *)uc)->uc_sigmask), SIGUSR2); + ksft_test_result(ret == 1, "USR2 blocked in ucontext\n"); + + /* + * USR2 is blocked; can be delivered neither here, nor after + * exit from handler + */ + if (raise(SIGUSR2)) + ksft_exit_fail_perror("raise"); +} + +void handler_segv(int signo, siginfo_t *info, void *uc) +{ + /* + * Three cases possible: + * 1. Program already terminated due to segmentation fault. + * 2. SEGV was blocked even after returning from handler_usr. + * 3. SEGV was delivered on returning from handler_usr. + * The last option must happen. + */ + ksft_test_result_pass("SEGV delivered\n"); +} + +static int cnt; + +void handler_usr(int signo, siginfo_t *info, void *uc) +{ + int ret; + + /* + * Break out of infinite recursion caused by raise(SIGUSR1) invoked + * from inside the handler + */ + ++cnt; + if (cnt > 1) + return; + + ksft_print_msg("In handler_usr\n"); + + /* SEGV blocked during handler execution, delivered on return */ + if (raise(SIGSEGV)) + ksft_exit_fail_perror("raise"); + + ksft_print_msg("SEGV bypassed successfully\n"); + + /* + * Signal responsible for handler invocation is blocked by default; + * delivered on return, leading to recursion + */ + if (raise(SIGUSR1)) + ksft_exit_fail_perror("raise"); + + ksft_test_result(cnt == 1, + "USR1 is blocked, cannot invoke handler right now\n"); + + /* Raise USR1 again; only one instance must be delivered upon exit */ + if (raise(SIGUSR1)) + ksft_exit_fail_perror("raise"); + + /* SEGV has been blocked in sa_mask, but ucontext is invariant */ + ret = sigismember(&(((ucontext_t *)uc)->uc_sigmask), SIGSEGV); + ksft_test_result(ret == 0, "USR1 not blocked in ucontext\n"); + + /* USR1 has been blocked, but ucontext is invariant */ + ret = sigismember(&(((ucontext_t *)uc)->uc_sigmask), SIGUSR1); + ksft_test_result(ret == 0, "SEGV not blocked in ucontext\n"); + + /* + * Mangle ucontext; this will be copied back into ¤t->blocked + * on return from the handler. + */ + if (sigaddset(&((ucontext_t *)uc)->uc_sigmask, SIGUSR2)) + ksft_exit_fail_perror("sigaddset"); +} + +int main(int argc, char *argv[]) +{ + struct sigaction act, act2; + sigset_t *set, *oldset; + + ksft_print_header(); + ksft_set_plan(7); + + act.sa_flags = SA_SIGINFO; + act.sa_sigaction = &handler_usr; + + /* Add SEGV to blocked mask */ + if (sigemptyset(&act.sa_mask) || sigaddset(&act.sa_mask, SIGSEGV) + || (sigismember(&act.sa_mask, SIGSEGV) != 1)) + ksft_exit_fail_msg("Cannot add SEGV to blocked mask\n"); + + if (sigaction(SIGUSR1, &act, NULL)) + ksft_exit_fail_perror("Cannot install handler"); + + act2.sa_flags = SA_SIGINFO; + act2.sa_sigaction = &handler_segv; + + if (sigaction(SIGSEGV, &act2, NULL)) + ksft_exit_fail_perror("Cannot install handler"); + + /* Invoke handler */ + if (raise(SIGUSR1)) + ksft_exit_fail_perror("raise"); + + /* USR1 must not be queued */ + ksft_test_result(cnt == 2, "handler invoked only twice\n"); + + /* Mangled ucontext implies USR2 is blocked for current thread */ + if (raise(SIGUSR2)) + ksft_exit_fail_perror("raise"); + + ksft_print_msg("USR2 bypassed successfully\n"); + + act.sa_sigaction = &handler_verify_ucontext; + if (sigaction(SIGUSR1, &act, NULL)) + ksft_exit_fail_perror("Cannot install handler"); + + if (raise(SIGUSR1)) + ksft_exit_fail_perror("raise"); + + ksft_print_msg("USR2 still blocked on return from handler\n"); + + /* Confirm USR2 blockage by sigprocmask() too */ + set = malloc(sizeof(sigset_t *)); + if (!set) + ksft_exit_fail_perror("malloc"); + + oldset = malloc(sizeof(sigset_t *)); + if (!oldset) + ksft_exit_fail_perror("malloc"); + + if (sigemptyset(set)) + ksft_exit_fail_perror("sigemptyset"); + + if (sigprocmask(SIG_BLOCK, set, oldset)) + ksft_exit_fail_perror("sigprocmask"); + + ksft_test_result(sigismember(oldset, SIGUSR2) == 1, + "USR2 present in ¤t->blocked\n"); + + ksft_finished(); +}