memcheck/tests/amd64-solaris/context_rflags2.c

   1 /* Test if definedness of rflags values is correctly propagated in and out
   2    of a signal handler.  Note that actually only the propagation of the
   3    overflow and sign flags is tested.
   4
   5    This test must use alarm(2) to trigger the signal and not kill(2) as other
   6    tests do because in the latter case the signal is actually delivered after
   7    the syscall finished.  This means that Valgrind had to save a correct carry
   8    flag value (indicating if the syscall succeeded) in the rflags.  This save
   9    operation unfortunately makes all rflags initialised (due to imprecise
  10    simulation). */
  11
  12 #include <assert.h>
  13 #include <signal.h>
  14 #include <stdio.h>
  15 #include <stdlib.h>
  16 #include <unistd.h>
  17 #include <sys/regset.h>
  18 #include <sys/syscall.h>
  19 #include <ucontext.h>
  20
  21 #define OBIT(rflags) (!!((rflags) & (1 << 11)))
  22 #define SBIT(rflags) (!!((rflags) & (1 << 7)))
  23
  24 static siginfo_t si;
  25 static ucontext_t uc;
  26
  27 void break_out(void);
  28
  29 static void sighandler(int sig, siginfo_t *sip, void *arg)
  30 {
  31    ucontext_t *ucp = (ucontext_t *) arg;
  32
  33    si = *sip;
  34    uc = *ucp;
  35
  36    /* Break out of the endless loop. */
  37    *(uintptr_t*)&ucp->uc_mcontext.gregs[REG_RIP] = (uintptr_t)break_out;
  38 }
  39
  40 int main(void)
  41 {
  42    struct sigaction sa;
  43    long rflags;
  44    int x1;
  45
  46    /* Uninitialised, but we know px[0] is 0x0. */
  47    int *px = malloc(sizeof(*px));
  48    x1 = px[0] + 1;
  49
  50    sa.sa_sigaction = sighandler;
  51    sa.sa_flags = SA_SIGINFO;
  52    if (sigfillset(&sa.sa_mask)) {
  53       perror("sigfillset");
  54       return 1;
  55    }
  56    if (sigaction(SIGALRM, &sa, NULL)) {
  57       perror("sigaction");
  58       return 1;
  59    }
  60
  61    alarm(2);
  62
  63    __asm__ __volatile__(
  64       /* Set overflow and sign flags. */
  65       "movl   %[x1], %%edx\n"
  66       "addl   $0x7fffffff, %%edx\n"
  67
  68       /* Loopity loop, this is where the SIGALRM is triggered. */
  69       "1:\n"
  70       "jmp    1b\n"
  71
  72       "break_out:\n"
  73       "pushfq\n"
  74       "popq   %%rdx\n"
  75       : "=d" (rflags)
  76       : [x1] "m" (x1)
  77       : "cc", "memory");
  78
  79    /* Check that the overflow and sign flags are uninitialised.
  80
  81       Note: This actually fails because the rflags are only approximate
  82       (always initialised) in the signal handler. */
  83    if (!OBIT(uc.uc_mcontext.gregs[REG_RFL]) ||
  84        !SBIT(uc.uc_mcontext.gregs[REG_RFL]))
  85       assert(0);
  86
  87    /* Check that the overflow and sign flags are uninitialised. */
  88    if (!OBIT(rflags) || !SBIT(rflags))
  89       assert(0);
  90
  91    return 0;
  92 }
  93