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t_signal_and_sp.c revision 1.1 
      1 /* $NetBSD: t_signal_and_sp.c,v 1.1 2024/04/22 07:24:22 pho Exp $ */
      2 
      3 /*
      4  * Copyright (c) 2024 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     17  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     18  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     19  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     20  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     26  * POSSIBILITY OF SUCH DAMAGE.
     27  */
     28 
     29 #include <atf-c.h>
     30 
     31 #if defined(HAVE_STACK_POINTER_H)
     32 #  include <signal.h>
     33 #  include <string.h>
     34 #  include <sys/stdint.h>
     35 #  include <sys/time.h>
     36 #  include "stack_pointer.h"
     37 
     38 static volatile void* stack_pointer = NULL;
     39 static void on_alarm(int sig __attribute__((__unused__)))
     40 {
     41 	/*
     42 	 * Store the stack pointer into a variable so that we can test if
     43 	 * it's aligned.
     44 	 */
     45 	LOAD_SP(stack_pointer);
     46 
     47 	/*
     48 	 * Now we are going to return from a signal
     49 	 * handler. __sigtramp_siginfo_2 will call setcontext(2) with a
     50 	 * ucontext provided by the kernel. When that fails it will call
     51 	 * _Exit(2) with the errno, and the test will fail.
     52 	 */
     53 }
     54 #endif
     55 
     56 ATF_TC(misaligned_sp_and_signal);
     57 ATF_TC_HEAD(misaligned_sp_and_signal, tc)
     58 {
     59 	atf_tc_set_md_var(tc, "descr", "process can return from a signal"
     60 	    " handler even if the stack pointer is misaligned when a signal"
     61 	    " arrives");
     62 }
     63 ATF_TC_BODY(misaligned_sp_and_signal, tc)
     64 {
     65 #if defined(HAVE_STACK_POINTER_H)
     66 	/*
     67 	 * Set up a handler for SIGALRM.
     68 	 */
     69 	struct sigaction sa;
     70 	memset(&sa, 0, sizeof(sa));
     71 	sa.sa_handler = &on_alarm;
     72 	ATF_REQUIRE(sigaction(SIGALRM, &sa, NULL) == 0);
     73 
     74 	/*
     75 	 * Set up an interval timer so that we receive SIGALRM after 50 ms.
     76 	 */
     77 	struct itimerval itv;
     78 	memset(&itv, 0, sizeof(itv));
     79 	itv.it_value.tv_usec = 1000 * 50;
     80 	ATF_REQUIRE(setitimer(ITIMER_MONOTONIC, &itv, NULL) == 0);
     81 
     82 	/*
     83 	 * Now misalign the SP. Wait for the signal to arrive and see what
     84 	 * happens. This should be fine as long as we don't use it to
     85 	 * access memory.
     86 	 */
     87 	MISALIGN_SP;
     88 	while (stack_pointer == NULL) {
     89 		/*
     90 		 * Make sure the compiler does not optimize this busy loop
     91 		 * away.
     92 		 */
     93 		__asm__("" : : : "memory");
     94 	}
     95 	/*
     96 	 * We could successfully return from a signal handler. Now we
     97 	 * should fix the SP before calling any functions.
     98 	 */
     99 	FIX_SP;
    100 
    101 	/*
    102 	 * But was the stack pointer aligned when we were on the signal
    103 	 * handler?
    104 	 */
    105 	ATF_CHECK_MSG(is_sp_aligned((uintptr_t)stack_pointer),
    106 	    "signal handler was called with a misaligned sp: %p",
    107 	    stack_pointer);
    108 #else
    109 	atf_tc_skip("Not implemented for this platform");
    110 #endif
    111 }
    112 
    113 ATF_TP_ADD_TCS(tp)
    114 {
    115 	ATF_TP_ADD_TC(tp, misaligned_sp_and_signal);
    116 	return atf_no_error();
    117 }
    118