selftests/powerpc: Add test for DSCR inheritence across fork & exec

TEST_PROGS := dscr_default_test dscr_explicit_test dscr_user_test	\

	      dscr_inherit_test

	      dscr_inherit_test dscr_inherit_exec_test

dscr_default_test: LDLIBS += -lpthread

/*

 * POWER Data Stream Control Register (DSCR) fork exec test

 *

 * This testcase modifies the DSCR using mtspr, forks & execs and

 * verifies that the child is using the changed DSCR using mfspr.

 *

 * When using the privilege state SPR, the instructions such as

 * mfspr or mtspr are priviledged and the kernel emulates them

 * for us. Instructions using problem state SPR can be exuecuted

 * directly without any emulation if the HW supports them. Else

 * they also get emulated by the kernel.

 *

 * Copyright 2012, Anton Blanchard, IBM Corporation.

 * Copyright 2015, Anshuman Khandual, IBM Corporation.

 *

 * This program is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 as published

 * by the Free Software Foundation.

 */

#include "dscr.h"

static char prog[LEN_MAX];

static void do_exec(unsigned long parent_dscr)

{

	unsigned long cur_dscr, cur_dscr_usr;

	cur_dscr = get_dscr();

	cur_dscr_usr = get_dscr_usr();

	if (cur_dscr != parent_dscr) {

		fprintf(stderr, "Parent DSCR %ld was not inherited "

				"over exec (kernel value)\n", parent_dscr);

		exit(1);

	}

	if (cur_dscr_usr != parent_dscr) {

		fprintf(stderr, "Parent DSCR %ld was not inherited "

				"over exec (user value)\n", parent_dscr);

		exit(1);

	}

	exit(0);

}

int dscr_inherit_exec(void)

{

	unsigned long i, dscr = 0;

	pid_t pid;

	for (i = 0; i < COUNT; i++) {

		dscr++;

		if (dscr > DSCR_MAX)

			dscr = 0;

		if (dscr == get_default_dscr())

			continue;

		if (i % 2 == 0)

			set_dscr_usr(dscr);

		else

			set_dscr(dscr);

		/*

		 * XXX: Force a context switch out so that DSCR

		 * current value is copied into the thread struct

		 * which is required for the child to inherit the

		 * changed value.

		 */

		sleep(1);

		pid = fork();

		if (pid == -1) {

			perror("fork() failed");

			exit(1);

		} else if (pid) {

			int status;

			if (waitpid(pid, &status, 0) == -1) {

				perror("waitpid() failed");

				exit(1);

			}

			if (!WIFEXITED(status)) {

				fprintf(stderr, "Child didn't exit cleanly\n");

				exit(1);

			}

			if (WEXITSTATUS(status) != 0) {

				fprintf(stderr, "Child didn't exit cleanly\n");

				return 1;

			}

		} else {

			char dscr_str[16];

			sprintf(dscr_str, "%ld", dscr);

			execlp(prog, prog, "exec", dscr_str, NULL);

			exit(1);

		}

	}

	return 0;

}

int main(int argc, char *argv[])

{

	if (argc == 3 && !strcmp(argv[1], "exec")) {

		unsigned long parent_dscr;

		parent_dscr = atoi(argv[2]);

		do_exec(parent_dscr);

	} else if (argc != 1) {

		fprintf(stderr, "Usage: %s\n", argv[0]);

		exit(1);

	}

	strncpy(prog, argv[0], strlen(argv[0]));

	return test_harness(dscr_inherit_exec, "dscr_inherit_exec_test");

}