tools/testing/selftests/sigaltstack/sas.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Stas Sergeev <stsp@users.sourceforge.net>
   4  *
   5  * test sigaltstack(SS_ONSTACK | SS_AUTODISARM)
   6  * If that succeeds, then swapcontext() can be used inside sighandler safely.
   7  *
   8  */
   9
  10 #define _GNU_SOURCE
  11 #include <signal.h>
  12 #include <stdio.h>
  13 #include <stdlib.h>
  14 #include <sys/mman.h>
  15 #include <ucontext.h>
  16 #include <alloca.h>
  17 #include <string.h>
  18 #include <assert.h>
  19 #include <errno.h>
  20
  21 #include "../kselftest.h"
  22
  23 #ifndef SS_AUTODISARM
  24 #define SS_AUTODISARM  (1U << 31)
  25 #endif
  26
  27 static void *sstack, *ustack;
  28 static ucontext_t uc, sc;
  29 static const char *msg = "[OK]\tStack preserved";
  30 static const char *msg2 = "[FAIL]\tStack corrupted";
  31 struct stk_data {
  32         char msg[128];
  33         int flag;
  34 };
  35
  36 void my_usr1(int sig, siginfo_t *si, void *u)
  37 {
  38         char *aa;
  39         int err;
  40         stack_t stk;
  41         struct stk_data *p;
  42
  43 #if __s390x__
  44         register unsigned long sp asm("%15");
  45 #else
  46         register unsigned long sp asm("sp");
  47 #endif
  48
  49         if (sp < (unsigned long)sstack ||
  50                         sp >= (unsigned long)sstack + SIGSTKSZ) {
  51                 ksft_exit_fail_msg("SP is not on sigaltstack\n");
  52         }
  53         /* put some data on stack. other sighandler will try to overwrite it */
  54         aa = alloca(1024);
  55         assert(aa);
  56         p = (struct stk_data *)(aa + 512);
  57         strcpy(p->msg, msg);
  58         p->flag = 1;
  59         ksft_print_msg("[RUN]\tsignal USR1\n");
  60         err = sigaltstack(NULL, &stk);
  61         if (err) {
  62                 ksft_exit_fail_msg("sigaltstack() - %s\n", strerror(errno));
  63                 exit(EXIT_FAILURE);
  64         }
  65         if (stk.ss_flags != SS_DISABLE)
  66                 ksft_test_result_fail("tss_flags=%x, should be SS_DISABLE\n",
  67                                 stk.ss_flags);
  68         else
  69                 ksft_test_result_pass(
  70                                 "sigaltstack is disabled in sighandler\n");
  71         swapcontext(&sc, &uc);
  72         ksft_print_msg("%s\n", p->msg);
  73         if (!p->flag) {
  74                 ksft_exit_skip("[RUN]\tAborting\n");
  75                 exit(EXIT_FAILURE);
  76         }
  77 }
  78
  79 void my_usr2(int sig, siginfo_t *si, void *u)
  80 {
  81         char *aa;
  82         struct stk_data *p;
  83
  84         ksft_print_msg("[RUN]\tsignal USR2\n");
  85         aa = alloca(1024);
  86         /* dont run valgrind on this */
  87         /* try to find the data stored by previous sighandler */
  88         p = memmem(aa, 1024, msg, strlen(msg));
  89         if (p) {
  90                 ksft_test_result_fail("sigaltstack re-used\n");
  91                 /* corrupt the data */
  92                 strcpy(p->msg, msg2);
  93                 /* tell other sighandler that his data is corrupted */
  94                 p->flag = 0;
  95         }
  96 }
  97
  98 static void switch_fn(void)
  99 {
 100         ksft_print_msg("[RUN]\tswitched to user ctx\n");
 101         raise(SIGUSR2);
 102         setcontext(&sc);
 103 }
 104
 105 int main(void)
 106 {
 107         struct sigaction act;
 108         stack_t stk;
 109         int err;
 110
 111         ksft_print_header();
 112
 113         sigemptyset(&act.sa_mask);
 114         act.sa_flags = SA_ONSTACK | SA_SIGINFO;
 115         act.sa_sigaction = my_usr1;
 116         sigaction(SIGUSR1, &act, NULL);
 117         act.sa_sigaction = my_usr2;
 118         sigaction(SIGUSR2, &act, NULL);
 119         sstack = mmap(NULL, SIGSTKSZ, PROT_READ | PROT_WRITE,
 120                       MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0);
 121         if (sstack == MAP_FAILED) {
 122                 ksft_exit_fail_msg("mmap() - %s\n", strerror(errno));
 123                 return EXIT_FAILURE;
 124         }
 125
 126         err = sigaltstack(NULL, &stk);
 127         if (err) {
 128                 ksft_exit_fail_msg("sigaltstack() - %s\n", strerror(errno));
 129                 exit(EXIT_FAILURE);
 130         }
 131         if (stk.ss_flags == SS_DISABLE) {
 132                 ksft_test_result_pass(
 133                                 "Initial sigaltstack state was SS_DISABLE\n");
 134         } else {
 135                 ksft_exit_fail_msg("Initial sigaltstack state was %x; "
 136                        "should have been SS_DISABLE\n", stk.ss_flags);
 137                 return EXIT_FAILURE;
 138         }
 139
 140         stk.ss_sp = sstack;
 141         stk.ss_size = SIGSTKSZ;
 142         stk.ss_flags = SS_ONSTACK | SS_AUTODISARM;
 143         err = sigaltstack(&stk, NULL);
 144         if (err) {
 145                 if (errno == EINVAL) {
 146                         ksft_exit_skip(
 147                                 "[NOTE]\tThe running kernel doesn't support SS_AUTODISARM\n");
 148                         /*
 149                          * If test cases for the !SS_AUTODISARM variant were
 150                          * added, we could still run them.  We don't have any
 151                          * test cases like that yet, so just exit and report
 152                          * success.
 153                          */
 154                         return 0;
 155                 } else {
 156                         ksft_exit_fail_msg(
 157                                 "sigaltstack(SS_ONSTACK | SS_AUTODISARM)  %s\n",
 158                                         strerror(errno));
 159                         return EXIT_FAILURE;
 160                 }
 161         }
 162
 163         ustack = mmap(NULL, SIGSTKSZ, PROT_READ | PROT_WRITE,
 164                       MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0);
 165         if (ustack == MAP_FAILED) {
 166                 ksft_exit_fail_msg("mmap() - %s\n", strerror(errno));
 167                 return EXIT_FAILURE;
 168         }
 169         getcontext(&uc);
 170         uc.uc_link = NULL;
 171         uc.uc_stack.ss_sp = ustack;
 172         uc.uc_stack.ss_size = SIGSTKSZ;
 173         makecontext(&uc, switch_fn, 0);
 174         raise(SIGUSR1);
 175
 176         err = sigaltstack(NULL, &stk);
 177         if (err) {
 178                 ksft_exit_fail_msg("sigaltstack() - %s\n", strerror(errno));
 179                 exit(EXIT_FAILURE);
 180         }
 181         if (stk.ss_flags != SS_AUTODISARM) {
 182                 ksft_exit_fail_msg("ss_flags=%x, should be SS_AUTODISARM\n",
 183                                 stk.ss_flags);
 184                 exit(EXIT_FAILURE);
 185         }
 186         ksft_test_result_pass(
 187                         "sigaltstack is still SS_AUTODISARM after signal\n");
 188
 189         ksft_exit_pass();
 190         return 0;
 191 }