Write test for stack overflow detection

libc/log/showcrashreports.c

@@ -92,6 +92,7 @@ static void FreeSigAltStack(void *p) {
  * @see callexitontermination()
  */
 void ShowCrashReports(void) {
+  char *sp;
   struct sigaltstack ss;
   /* <SYNC-LIST>: showcrashreports.c, oncrashthunks.S, oncrash.c */
   kCrashSigs[0] = SIGQUIT; /* ctrl+\ aka ctrl+break */
@@ -105,11 +106,12 @@ void ShowCrashReports(void) {
   if (!IsWindows()) {
     bzero(&ss, sizeof(ss));
     ss.ss_flags = 0;
-    ss.ss_size = SIGSTKSZ;
+    ss.ss_size = GetStackSize();
     // FreeBSD sigaltstack() will EFAULT if we use MAP_STACK here
     // OpenBSD sigaltstack() auto-applies MAP_STACK to the memory
-    if ((ss.ss_sp = mmap(0, GetStackSize(), PROT_READ | PROT_WRITE,
-                         MAP_PRIVATE | MAP_ANONYMOUS, -1, 0))) {
+    if ((sp = mmap(0, GetStackSize(), PROT_READ | PROT_WRITE,
+                   MAP_PRIVATE | MAP_ANONYMOUS, -1, 0)) != MAP_FAILED) {
+      ss.ss_sp = sp;
       if (!sigaltstack(&ss, &g_oldsigaltstack)) {
         __cxa_atexit(FreeSigAltStack, ss.ss_sp, 0);
       } else {

libc/rand/rand64.c

@@ -47,7 +47,6 @@ _Alignas(64) static int rand64_lock;
  * @note this function is not intended for cryptography
  * @note this function passes bigcrush and practrand
  * @note this function takes at minimum 15 cycles
- * @asyncsignalsafe
  * @threadsafe
  * @vforksafe
  */

test/libc/log/backtrace_test.c

@@ -23,6 +23,7 @@
 #include "libc/fmt/conv.h"
 #include "libc/intrin/asan.internal.h"
 #include "libc/intrin/kprintf.h"
+#include "libc/limits.h"
 #include "libc/log/libfatal.internal.h"
 #include "libc/log/log.h"
 #include "libc/mem/mem.h"
@@ -39,6 +40,14 @@
 #include "libc/x/x.h"
 #include "net/http/escape.h"
 
+int StackOverflow(int f(), int n) {
+  if (n < INT_MAX) {
+    return f(f, n + 1) - 1;
+  } else {
+    return INT_MAX;
+  }
+}
+
 static bool OutputHasSymbol(const char *output, const char *s) {
   return strstr(output, s) || (!FindDebugBinary() && strstr(output, "NULL"));
 }
@@ -103,6 +112,7 @@ int (*pRodataOverrunCrash)(int) = RodataOverrunCrash;
 char *(*pStackOverrunCrash)(int) = StackOverrunCrash;
 char *(*pMemoryLeakCrash)(void) = MemoryLeakCrash;
 int (*pNpeCrash)(char *) = NpeCrash;
+int (*pStackOverflow)(int (*)(), int) = StackOverflow;
 
 void SetUp(void) {
   ShowCrashReports();
@@ -130,6 +140,8 @@ void SetUp(void) {
       case 8:
         __cxa_finalize(0);
         exit(pNpeCrash(0));
+      case 9:
+        exit(pStackOverflow(pStackOverflow, 0));
       default:
         printf("preventing fork recursion: %s\n", __argv[1]);
         exit(1);
@@ -428,6 +440,79 @@ TEST(ShowCrashReports, testDivideByZero) {
   free(output);
 }
 
+TEST(ShowCrashReports, testStackOverflow) {
+  if (IsXnu()) return;      // TODO(jart): fix me
+  if (IsWindows()) return;  // TODO(jart): fix me
+  if (IsFreebsd()) return;  // TODO(jart): fix me
+  if (IsOpenbsd()) return;  // TODO(jart): fix me
+  size_t got;
+  ssize_t rc;
+  int ws, pid, fds[2];
+  char *output, buf[512];
+  ASSERT_NE(-1, pipe2(fds, O_CLOEXEC));
+  ASSERT_NE(-1, (pid = vfork()));
+  if (!pid) {
+    dup2(fds[1], 1);
+    dup2(fds[1], 2);
+    execv(GetProgramExecutableName(),
+          (char *const[]){GetProgramExecutableName(), "9", "--strace", 0});
+    _exit(127);
+  }
+  close(fds[1]);
+  output = 0;
+  appends(&output, "");
+  for (;;) {
+    rc = read(fds[0], buf, sizeof(buf));
+    if (rc == -1) {
+      ASSERT_EQ(EINTR, errno);
+      continue;
+    }
+    if ((got = rc)) {
+      appendd(&output, buf, got);
+    } else {
+      break;
+    }
+  }
+  close(fds[0]);
+  ASSERT_NE(-1, wait(&ws));
+  EXPECT_TRUE(WIFEXITED(ws));
+  // kprintf("exit status %d\n", WEXITSTATUS(ws));
+  assert(128 + SIGSEGV == WEXITSTATUS(ws) || 77 == WEXITSTATUS(ws));
+  /* NULL is stopgap until we can copy symbol tablces into binary */
+#ifdef __FNO_OMIT_FRAME_POINTER__
+  if (!OutputHasSymbol(output, "StackOverflow")) {
+    fprintf(stderr, "ERROR: crash report didn't have backtrace\n%s\n",
+            gc(IndentLines(output, -1, 0, 4)));
+    __die();
+  }
+#endif
+  // ShowCrashReports() handled it
+  if (!strstr(output, gc(xasprintf("%d", pid)))) {
+    fprintf(stderr, "ERROR: crash report didn't have pid\n%s\n",
+            gc(IndentLines(output, -1, 0, 4)));
+    __die();
+  }
+  if (!strstr(output, "SIGSEGV")) {
+    fprintf(stderr, "ERROR: crash report didn't have signal name\n%s\n",
+            gc(IndentLines(output, -1, 0, 4)));
+    __die();
+  }
+  if (!IsTiny()) {
+    if (!strstr(output, "Stack Overflow")) {
+      fprintf(stderr, "ERROR: crash report didn't have 'Stack Overflow'\n%s\n",
+              gc(IndentLines(output, -1, 0, 4)));
+      __die();
+    }
+  } else {
+    if (!strstr(output, "SEGV_MAPERR")) {
+      fprintf(stderr, "ERROR: crash report didn't have 'SEGV_MAPERR'\n%s\n",
+              gc(IndentLines(output, -1, 0, 4)));
+      __die();
+    }
+  }
+  free(output);
+}
+
 // clang-format off
 //
 // test/libc/log/backtrace_test.c:59: ubsan error: 'int' index 10 into 'char [10]' out of bounds

tool/build/lib/eztls.c

@@ -63,8 +63,11 @@ static ssize_t EzWritevAll(int fd, struct iovec *iov, int iovlen) {
           wrote = 0;
         }
       } while (wrote);
-    } else if (errno != EINTR) {
-      return total ? total : -1;
+    } else {
+      WARNF("writev() failed %m");
+      if (errno != EINTR) {
+        return total ? total : -1;
+      }
     }
   } while (i < iovlen);
   return total;
@@ -121,6 +124,7 @@ static int EzTlsRecvImpl(void *ctx, unsigned char *p, size_t n, uint32_t o) {
   v[1].iov_base = bio->t;
   v[1].iov_len = sizeof(bio->t);
   while ((r = readv(bio->fd, v, 2)) == -1) {
+    WARNF("tls read() error %s", strerror(errno));
     if (errno == EINTR) {
       return MBEDTLS_ERR_SSL_WANT_READ;
     } else if (errno == EAGAIN) {
@@ -128,7 +132,6 @@ static int EzTlsRecvImpl(void *ctx, unsigned char *p, size_t n, uint32_t o) {
     } else if (errno == EPIPE || errno == ECONNRESET || errno == ENETRESET) {
       return MBEDTLS_ERR_NET_CONN_RESET;
     } else {
-      WARNF("tls read() error %s", strerror(errno));
       return MBEDTLS_ERR_NET_RECV_FAILED;
     }
   }