kernel/tools/testing/selftests/powerpc/dscr/dscr_inherit_test.c

   1 /*
   2  * POWER Data Stream Control Register (DSCR) fork test
   3  *
   4  * This testcase modifies the DSCR using mtspr, forks and then
   5  * verifies that the child process has the correct changed DSCR
   6  * value using mfspr.
   7  *
   8  * When using the privilege state SPR, the instructions such as
   9  * mfspr or mtspr are priviledged and the kernel emulates them
  10  * for us. Instructions using problem state SPR can be exuecuted
  11  * directly without any emulation if the HW supports them. Else
  12  * they also get emulated by the kernel.
  13  *
  14  * Copyright 2012, Anton Blanchard, IBM Corporation.
  15  * Copyright 2015, Anshuman Khandual, IBM Corporation.
  16  *
  17  * This program is free software; you can redistribute it and/or modify it
  18  * under the terms of the GNU General Public License version 2 as published
  19  * by the Free Software Foundation.
  20  */
  21 #include "dscr.h"
  22
  23 int dscr_inherit(void)
  24 {
  25         unsigned long i, dscr = 0;
  26         pid_t pid;
  27
  28         srand(getpid());
  29         set_dscr(dscr);
  30
  31         for (i = 0; i < COUNT; i++) {
  32                 unsigned long cur_dscr, cur_dscr_usr;
  33
  34                 dscr++;
  35                 if (dscr > DSCR_MAX)
  36                         dscr = 0;
  37
  38                 if (i % 2 == 0)
  39                         set_dscr_usr(dscr);
  40                 else
  41                         set_dscr(dscr);
  42
  43                 /*
  44                  * XXX: Force a context switch out so that DSCR
  45                  * current value is copied into the thread struct
  46                  * which is required for the child to inherit the
  47                  * changed value.
  48                  */
  49                 sleep(1);
  50
  51                 pid = fork();
  52                 if (pid == -1) {
  53                         perror("fork() failed");
  54                         exit(1);
  55                 } else if (pid) {
  56                         int status;
  57
  58                         if (waitpid(pid, &status, 0) == -1) {
  59                                 perror("waitpid() failed");
  60                                 exit(1);
  61                         }
  62
  63                         if (!WIFEXITED(status)) {
  64                                 fprintf(stderr, "Child didn't exit cleanly\n");
  65                                 exit(1);
  66                         }
  67
  68                         if (WEXITSTATUS(status) != 0) {
  69                                 fprintf(stderr, "Child didn't exit cleanly\n");
  70                                 return 1;
  71                         }
  72                 } else {
  73                         cur_dscr = get_dscr();
  74                         if (cur_dscr != dscr) {
  75                                 fprintf(stderr, "Kernel DSCR should be %ld "
  76                                         "but is %ld\n", dscr, cur_dscr);
  77                                 exit(1);
  78                         }
  79
  80                         cur_dscr_usr = get_dscr_usr();
  81                         if (cur_dscr_usr != dscr) {
  82                                 fprintf(stderr, "User DSCR should be %ld "
  83                                         "but is %ld\n", dscr, cur_dscr_usr);
  84                                 exit(1);
  85                         }
  86                         exit(0);
  87                 }
  88         }
  89         return 0;
  90 }
  91
  92 int main(int argc, char *argv[])
  93 {
  94         return test_harness(dscr_inherit, "dscr_inherit_test");
  95 }