[sanitizer] Add TryMemCpy

compiler-rt/lib/sanitizer_common/sanitizer_common.h

@@ -268,7 +268,11 @@ class ScopedErrorReportLock {
 extern uptr stoptheworld_tracer_pid;
 extern uptr stoptheworld_tracer_ppid;
 
+// Returns true if we can read a memory range.
 bool IsAccessibleMemoryRange(uptr beg, uptr size);
+// Returns true if we can read a memory range starting at `src`, and copies
+// content into `dest`.
+bool TryMemCpy(void *dest, const void *src, uptr n);
 
 // Error report formatting.
 const char *StripPathPrefix(const char *filepath,

compiler-rt/lib/sanitizer_common/sanitizer_fuchsia.cpp

@@ -444,6 +444,11 @@ bool IsAccessibleMemoryRange(uptr beg, uptr size) {
   return status == ZX_OK;
 }
 
+bool TryMemCpy(void *dest, const void *src, uptr n) {
+  // TODO: implement.
+  return false;
+}
+
 // FIXME implement on this platform.
 void GetMemoryProfile(fill_profile_f cb, uptr *stats) {}
 

compiler-rt/lib/sanitizer_common/sanitizer_posix_libcdep.cpp

@@ -288,26 +288,79 @@ bool SignalContext::IsStackOverflow() const {
 
 #endif  // SANITIZER_GO
 
+static void SetNonBlock(int fd) {
+  int res = fcntl(fd, F_GETFL, 0);
+  CHECK(!internal_iserror(res, nullptr));
+
+  res |= O_NONBLOCK;
+  res = fcntl(fd, F_SETFL, res);
+  CHECK(!internal_iserror(res, nullptr));
+}
+
 bool IsAccessibleMemoryRange(uptr beg, uptr size) {
-  uptr page_size = GetPageSizeCached();
-  // Checking too large memory ranges is slow.
-  CHECK_LT(size, page_size * 10);
+  while (size) {
+    // `read` from `sock_pair[0]` into a dummy buffer to free up the pipe buffer
+    // for more `write` is slower than just recreating a pipe.
+    int sock_pair[2];
+    if (pipe(sock_pair))
+      return false;
+
+    auto cleanup = at_scope_exit([&]() {
+      internal_close(sock_pair[0]);
+      internal_close(sock_pair[1]);
+    });
+
+    SetNonBlock(sock_pair[1]);
+
+    int write_errno;
+    uptr w = internal_write(sock_pair[1], reinterpret_cast<char *>(beg), size);
+    if (internal_iserror(w, &write_errno)) {
+      CHECK_EQ(EFAULT, write_errno);
+      return false;
+    }
+    size -= w;
+    beg += w;
+  }
+
+  return true;
+}
+
+bool TryMemCpy(void *dest, const void *src, uptr n) {
   int sock_pair[2];
   if (pipe(sock_pair))
     return false;
-  uptr bytes_written =
-      internal_write(sock_pair[1], reinterpret_cast<void *>(beg), size);
-  int write_errno;
-  bool result;
-  if (internal_iserror(bytes_written, &write_errno)) {
-    CHECK_EQ(EFAULT, write_errno);
-    result = false;
-  } else {
-    result = (bytes_written == size);
+
+  auto cleanup = at_scope_exit([&]() {
+    internal_close(sock_pair[0]);
+    internal_close(sock_pair[1]);
+  });
+
+  SetNonBlock(sock_pair[0]);
+  SetNonBlock(sock_pair[1]);
+
+  char *d = static_cast<char *>(dest);
+  const char *s = static_cast<const char *>(src);
+
+  while (n) {
+    int e;
+    uptr w = internal_write(sock_pair[1], s, n);
+    if (internal_iserror(w, &e)) {
+      CHECK_EQ(EFAULT, e);
+      return false;
+    }
+    s += w;
+    n -= w;
+
+    while (w) {
+      uptr r = internal_read(sock_pair[0], d, w);
+      CHECK(!internal_iserror(r, &e));
+
+      d += r;
+      w -= r;
+    }
   }
-  internal_close(sock_pair[0]);
-  internal_close(sock_pair[1]);
-  return result;
+
+  return true;
 }
 
 void PlatformPrepareForSandboxing(void *args) {

compiler-rt/lib/sanitizer_common/sanitizer_win.cpp

@@ -968,6 +968,11 @@ bool IsAccessibleMemoryRange(uptr beg, uptr size) {
   return true;
 }
 
+bool TryMemCpy(void *dest, const void *src, uptr n) {
+  // TODO: implement.
+  return false;
+}
+
 bool SignalContext::IsStackOverflow() const {
   return (DWORD)GetType() == EXCEPTION_STACK_OVERFLOW;
 }

compiler-rt/lib/sanitizer_common/tests/sanitizer_posix_test.cpp

@@ -13,11 +13,14 @@
 #include "sanitizer_common/sanitizer_platform.h"
 #if SANITIZER_POSIX
 
-#include "sanitizer_common/sanitizer_common.h"
-#include "gtest/gtest.h"
+#  include <pthread.h>
+#  include <sys/mman.h>
 
-#include <pthread.h>
-#include <sys/mman.h>
+#  include <numeric>
+
+#  include "gmock/gmock.h"
+#  include "gtest/gtest.h"
+#  include "sanitizer_common/sanitizer_common.h"
 
 namespace __sanitizer {
 
@@ -82,6 +85,51 @@ TEST(SanitizerCommon, IsAccessibleMemoryRange) {
   munmap((void *)mem, 3 * page_size);
 }
 
+TEST(SanitizerCommon, IsAccessibleMemoryRangeLarge) {
+  const int size = GetPageSize() * 10000;
+
+  uptr mem = (uptr)mmap(0, size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON,
+                        -1, 0);
+
+  EXPECT_TRUE(IsAccessibleMemoryRange(mem, size));
+
+  munmap((void *)mem, size);
+}
+
+TEST(SanitizerCommon, TryMemCpy) {
+  std::vector<char> src(10000000);
+  std::iota(src.begin(), src.end(), 123);
+  std::vector<char> dst;
+
+  using ::testing::ElementsAreArray;
+
+  dst.assign(1, 0);
+  ASSERT_TRUE(TryMemCpy(dst.data(), src.data(), dst.size()));
+  EXPECT_THAT(dst, ElementsAreArray(src.data(), dst.size()));
+
+  dst.assign(100, 0);
+  ASSERT_TRUE(TryMemCpy(dst.data(), src.data(), dst.size()));
+  EXPECT_THAT(dst, ElementsAreArray(src.data(), dst.size()));
+
+  dst.assign(534, 0);
+  ASSERT_TRUE(TryMemCpy(dst.data(), src.data(), dst.size()));
+  EXPECT_THAT(dst, ElementsAreArray(src.data(), dst.size()));
+
+  dst.assign(GetPageSize(), 0);
+  ASSERT_TRUE(TryMemCpy(dst.data(), src.data(), dst.size()));
+  EXPECT_THAT(dst, ElementsAreArray(src.data(), dst.size()));
+
+  dst.assign(src.size(), 0);
+  ASSERT_TRUE(TryMemCpy(dst.data(), src.data(), dst.size()));
+  EXPECT_THAT(dst, ElementsAreArray(src.data(), dst.size()));
+
+  dst.assign(src.size() - 1, 0);
+  ASSERT_TRUE(TryMemCpy(dst.data(), src.data(), dst.size()));
+  EXPECT_THAT(dst, ElementsAreArray(src.data(), dst.size()));
+
+  EXPECT_FALSE(TryMemCpy(dst.data(), nullptr, dst.size()));
+}
+
 }  // namespace __sanitizer
 
 #endif  // SANITIZER_POSIX