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 } 187