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    Subject[PATCH V5 09/13] selftests, powerpc: Add test for DSCR value inheritence across fork
    Date
    This patch adds a test to verify that the changed DSCR value inside
    any process would be inherited to it's child process across the fork
    system call.

    Acked-by: Shuah Khan <shuahkh@osg.samsung.com>
    Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
    Signed-off-by: Anton Blanchard <anton@samba.org>
    ---
    tools/testing/selftests/powerpc/dscr/Makefile | 3 +-
    .../selftests/powerpc/dscr/dscr_inherit_test.c | 96 ++++++++++++++++++++++
    2 files changed, 98 insertions(+), 1 deletion(-)
    create mode 100644 tools/testing/selftests/powerpc/dscr/dscr_inherit_test.c

    diff --git a/tools/testing/selftests/powerpc/dscr/Makefile b/tools/testing/selftests/powerpc/dscr/Makefile
    index ae865d8..81239e2 100644
    --- a/tools/testing/selftests/powerpc/dscr/Makefile
    +++ b/tools/testing/selftests/powerpc/dscr/Makefile
    @@ -1,4 +1,5 @@
    -PROGS := dscr_default_test dscr_explicit_test dscr_user_test
    +PROGS := dscr_default_test dscr_explicit_test dscr_user_test \
    + dscr_inherit_test

    CFLAGS := $(CFLAGS) -lpthread

    diff --git a/tools/testing/selftests/powerpc/dscr/dscr_inherit_test.c b/tools/testing/selftests/powerpc/dscr/dscr_inherit_test.c
    new file mode 100644
    index 0000000..9d0ca37
    --- /dev/null
    +++ b/tools/testing/selftests/powerpc/dscr/dscr_inherit_test.c
    @@ -0,0 +1,96 @@
    +/*
    + * POWER Data Stream Control Register (DSCR) fork test
    + *
    + * This testcase modifies the DSCR using mtspr, forks and then
    + * verifies that the child process has the correct changed DSCR
    + * value 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 (C) 2012 Anton Blanchard <anton@au.ibm.com>, IBM
    + * Copyright (C) 2015 Anshuman Khandual <khandual@linux.vnet.ibm.com>, IBM
    + *
    + * This program is free software; you can redistribute it and/or
    + * modify it under the terms of the GNU General Public License
    + * as published by the Free Software Foundation; either version
    + * 2 of the License, or (at your option) any later version.
    + */
    +#include "dscr.h"
    +
    +int dscr_inherit(void)
    +{
    + unsigned long i, dscr = 0;
    + pid_t pid;
    +
    + srand(getpid());
    + set_dscr(dscr);
    +
    + for (i = 0; i < COUNT; i++) {
    + unsigned long cur_dscr, cur_dscr_usr;
    +
    + dscr++;
    + if (dscr > DSCR_MAX)
    + dscr = 0;
    +
    + 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 {
    + cur_dscr = get_dscr();
    + if (cur_dscr != dscr) {
    + fprintf(stderr, "Kernel DSCR should be %ld "
    + "but is %ld\n", dscr, cur_dscr);
    + exit(1);
    + }
    +
    + cur_dscr_usr = get_dscr_usr();
    + if (cur_dscr_usr != dscr) {
    + fprintf(stderr, "User DSCR should be %ld "
    + "but is %ld\n", dscr, cur_dscr_usr);
    + exit(1);
    + }
    + exit(0);
    + }
    + }
    + return 0;
    +}
    +
    +int main(int argc, char *argv[])
    +{
    + return test_harness(dscr_inherit, "dscr_inherit_test");
    +}
    --
    2.1.0


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