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    Subject[PATCH 01/10] selftests/x86: In syscall_nt, test NT|TF as well
    Date
    Setting TF prevents fastpath returns in most cases, which causes the
    test to fail on 32-bit kernels because 32-bit kernels do not, in
    fact, handle NT correctly on SYSENTER entries.

    The next patch will fix 32-bit kernels.

    Signed-off-by: Andy Lutomirski <luto@kernel.org>
    ---
    tools/testing/selftests/x86/syscall_nt.c | 57 +++++++++++++++++++++++++++-----
    1 file changed, 49 insertions(+), 8 deletions(-)

    diff --git a/tools/testing/selftests/x86/syscall_nt.c b/tools/testing/selftests/x86/syscall_nt.c
    index 60c06af4646a..a6ceff86c199 100644
    --- a/tools/testing/selftests/x86/syscall_nt.c
    +++ b/tools/testing/selftests/x86/syscall_nt.c
    @@ -17,6 +17,9 @@

    #include <stdio.h>
    #include <unistd.h>
    +#include <string.h>
    +#include <signal.h>
    +#include <err.h>
    #include <sys/syscall.h>
    #include <asm/processor-flags.h>

    @@ -26,6 +29,8 @@
    # define WIDTH "l"
    #endif

    +static unsigned int nerrs;
    +
    static unsigned long get_eflags(void)
    {
    unsigned long eflags;
    @@ -39,16 +44,52 @@ static void set_eflags(unsigned long eflags)
    : : "rm" (eflags) : "flags");
    }

    -int main()
    +static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
    + int flags)
    {
    - printf("[RUN]\tSet NT and issue a syscall\n");
    - set_eflags(get_eflags() | X86_EFLAGS_NT);
    + struct sigaction sa;
    + memset(&sa, 0, sizeof(sa));
    + sa.sa_sigaction = handler;
    + sa.sa_flags = SA_SIGINFO | flags;
    + sigemptyset(&sa.sa_mask);
    + if (sigaction(sig, &sa, 0))
    + err(1, "sigaction");
    +}
    +
    +static void sigtrap(int sig, siginfo_t *si, void *ctx_void)
    +{
    +}
    +
    +static void do_it(unsigned long extraflags)
    +{
    + unsigned long flags;
    +
    + set_eflags(get_eflags() | extraflags);
    syscall(SYS_getpid);
    - if (get_eflags() & X86_EFLAGS_NT) {
    - printf("[OK]\tThe syscall worked and NT is still set\n");
    - return 0;
    + flags = get_eflags();
    + if ((flags & extraflags) == extraflags) {
    + printf("[OK]\tThe syscall worked and flags are still set\n");
    } else {
    - printf("[FAIL]\tThe syscall worked but NT was cleared\n");
    - return 1;
    + printf("[FAIL]\tThe syscall worked but flags were cleared (flags = 0x%lx but expected 0x%lx set)\n",
    + flags, extraflags);
    + nerrs++;
    }
    }
    +
    +int main()
    +{
    + printf("[RUN]\tSet NT and issue a syscall\n");
    + do_it(X86_EFLAGS_NT);
    +
    + /*
    + * Now try it again with TF set -- TF forces returns via IRET in all
    + * cases except non-ptregs-using 64-bit full fast path syscalls.
    + */
    +
    + sethandler(SIGTRAP, sigtrap, 0);
    +
    + printf("[RUN]\tSet NT|TF and issue a syscall\n");
    + do_it(X86_EFLAGS_NT | X86_EFLAGS_TF);
    +
    + return nerrs == 0 ? 0 : 1;
    +}
    --
    2.5.0
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