tools/testing/selftests/sigaltstack/sas.c

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