compiler-rt/test/msan/Linux/swapcontext_annotation_reset.cpp

   1 // RUN: %clangxx_msan -fno-sanitize-memory-param-retval -fno-sanitize=memory -c %s -o %t-main.o
   2 // RUN: %clangxx_msan -fno-sanitize-memory-param-retval %t-main.o %s -o %t
   3 // RUN: %run %t
   4
   5 #include <assert.h>
   6 #include <stdio.h>
   7 #include <stdlib.h>
   8 #include <ucontext.h>
   9 #include <unistd.h>
  10
  11 #include <sanitizer/msan_interface.h>
  12
  13 #if __has_feature(memory_sanitizer)
  14
  15 __attribute__((noinline)) int bar(int a, int b) {
  16   volatile int zero = 0;
  17   return zero;
  18 }
  19
  20 void foo(int x, int y, int expected) {
  21   assert(__msan_test_shadow(&x, sizeof(x)) == expected);
  22   assert(__msan_test_shadow(&y, sizeof(y)) == expected);
  23
  24   // Poisons parameter shadow in TLS so that the next call (to foo) from
  25   // uninstrumented main has params 1 and 2 poisoned no matter what.
  26   int a, b;
  27   (void)bar(a, b);
  28 }
  29
  30 #else
  31
  32 // This code is not instrumented by MemorySanitizer to prevent it from modifying
  33 // MSAN TLS data for this test.
  34
  35 int foo(int, int, int);
  36
  37 int main(int argc, char **argv) {
  38   int x, y;
  39   // The parameters should _not_ be poisoned; this is the first call to foo.
  40   foo(x, y, -1);
  41   // The parameters should be poisoned; the prior call to foo left them so.
  42   foo(x, y, 0);
  43
  44   ucontext_t ctx;
  45   if (getcontext(&ctx) == -1) {
  46     perror("getcontext");
  47     _exit(1);
  48   }
  49
  50   // Simulate a fiber switch occurring from MSAN's perspective (though no switch
  51   // actually occurs).
  52   const void *previous_stack_bottom = nullptr;
  53   size_t previous_stack_size = 0;
  54   __msan_start_switch_fiber(ctx.uc_stack.ss_sp, ctx.uc_stack.ss_size);
  55   __msan_finish_switch_fiber(&previous_stack_bottom, &previous_stack_size);
  56
  57   // The simulated fiber switch will reset the TLS parameter shadow. So even
  58   // though the most recent call to foo left the parameter shadow poisoned, the
  59   // parameters are _not_ expected to be poisoned now.
  60   foo(x, y, -1);
  61
  62   return 0;
  63 }
  64
  65 #endif