Assume FS_IOC_GETFLAGS may trash output on error

[bup.git] / lib / bup / _helpers.c

diff --git a/lib/bup/_helpers.c b/lib/bup/_helpers.c
index b9b050bad10a2a40ad6de1289380628e69324853..9082dca72994079da1f900f8785f751a3d52715c 100644 (file)
--- a/lib/bup/_helpers.c
+++ b/lib/bup/_helpers.c
@@ -39,6 +39,14 @@
 #define BUP_HAVE_FILE_ATTRS 1
 #endif
 
+/*
+ * Check for incomplete UTIMENSAT support (NetBSD 6), and if so,
+ * pretend we don't have it.
+ */
+#if !defined(AT_FDCWD) || !defined(AT_SYMLINK_NOFOLLOW)
+#undef HAVE_UTIMENSAT
+#endif
+
 #ifndef FS_NOCOW_FL
 // Of course, this assumes it's a bitfield value.
 #define FS_NOCOW_FL 0
@@ -46,6 +54,22 @@
 
 static int istty2 = 0;
 
+
+#ifndef htonll
+// This function should technically be macro'd out if it's going to be used
+// more than ocasionally.  As of this writing, it'll actually never be called
+// in real world bup scenarios (because our packs are < MAX_INT bytes).
+static uint64_t htonll(uint64_t value)
+{
+    static const int endian_test = 42;
+
+    if (*(char *)&endian_test == endian_test) // LSB-MSB
+       return ((uint64_t)htonl(value & 0xFFFFFFFF) << 32) | htonl(value >> 32);
+    return value; // already in network byte order MSB-LSB
+}
+#endif
+
+
 // At the moment any code that calls INTGER_TO_PY() will have to
 // disable -Wtautological-compare for clang.  See below.
 
@@ -578,18 +602,6 @@ static PyObject *merge_into(PyObject *self, PyObject *args)
     return PyLong_FromUnsignedLong(count);
 }
 
-// This function should technically be macro'd out if it's going to be used
-// more than ocasionally.  As of this writing, it'll actually never be called
-// in real world bup scenarios (because our packs are < MAX_INT bytes).
-static uint64_t htonll(uint64_t value)
-{
-    static const int endian_test = 42;
-
-    if (*(char *)&endian_test == endian_test) // LSB-MSB
-       return ((uint64_t)htonl(value & 0xFFFFFFFF) << 32) | htonl(value >> 32);
-    return value; // already in network byte order MSB-LSB
-}
-
 #define FAN_ENTRIES 256
 
 static PyObject *write_idx(PyObject *self, PyObject *args)
@@ -803,11 +815,21 @@ static PyObject *fadvise_done(PyObject *self, PyObject *args)
 }
 
 
+// Currently the Linux kernel and FUSE disagree over the type for
+// FS_IOC_GETFLAGS and FS_IOC_SETFLAGS.  The kernel actually uses int,
+// but FUSE chose long (matching the declaration in linux/fs.h).  So
+// if you use int, and then traverse a FUSE filesystem, you may
+// corrupt the stack.  But if you use long, then you may get invalid
+// results on big-endian systems.
+//
+// For now, we just use long, and then disable Linux attrs entirely
+// (with a warning) in helpers.py on systems that are affected.
+
 #ifdef BUP_HAVE_FILE_ATTRS
 static PyObject *bup_get_linux_file_attr(PyObject *self, PyObject *args)
 {
     int rc;
-    unsigned int attr;
+    unsigned long attr;
     char *path;
     int fd;
 
@@ -818,16 +840,16 @@ static PyObject *bup_get_linux_file_attr(PyObject *self, PyObject *args)
     if (fd == -1)
         return PyErr_SetFromErrnoWithFilename(PyExc_OSError, path);
 
-    attr = 0;
+    attr = 0;  // Handle int/long mismatch (see above)
     rc = ioctl(fd, FS_IOC_GETFLAGS, &attr);
     if (rc == -1)
     {
         close(fd);
         return PyErr_SetFromErrnoWithFilename(PyExc_OSError, path);
     }
-
     close(fd);
-    return Py_BuildValue("I", attr);
+    assert(attr <= UINT_MAX);  // Kernel type is actually int
+    return PyLong_FromUnsignedLong(attr);
 }
 #endif /* def BUP_HAVE_FILE_ATTRS */
 
@@ -837,7 +859,8 @@ static PyObject *bup_get_linux_file_attr(PyObject *self, PyObject *args)
 static PyObject *bup_set_linux_file_attr(PyObject *self, PyObject *args)
 {
     int rc;
-    unsigned int orig_attr, attr;
+    unsigned long orig_attr;
+    unsigned int attr;
     char *path;
     PyObject *py_attr;
     int fd;
@@ -861,13 +884,15 @@ static PyObject *bup_set_linux_file_attr(PyObject *self, PyObject *args)
     | FS_TOPDIR_FL | FS_NOCOW_FL;
 
     // The extents flag can't be removed, so don't (see chattr(1) and chattr.c).
+    orig_attr = 0; // Handle int/long mismatch (see above)
     rc = ioctl(fd, FS_IOC_GETFLAGS, &orig_attr);
+    assert(orig_attr <= UINT_MAX);  // Kernel type is actually int
     if (rc == -1)
     {
         close(fd);
         return PyErr_SetFromErrnoWithFilename(PyExc_OSError, path);
     }
-    attr |= (orig_attr & FS_EXTENT_FL);
+    attr |= ((unsigned int) orig_attr) & FS_EXTENT_FL;
 
     rc = ioctl(fd, FS_IOC_SETFLAGS, &attr);
     if (rc == -1)
@@ -1222,9 +1247,9 @@ PyMODINIT_FUNC init_helpers(void)
     if (m == NULL)
         return;
 
-#ifdef HAVE_UTIMENSAT
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wtautological-compare" // For INTEGER_TO_PY().
+#ifdef HAVE_UTIMENSAT
     {
         PyObject *value;
         value = INTEGER_TO_PY(AT_FDCWD);
@@ -1237,8 +1262,20 @@ PyMODINIT_FUNC init_helpers(void)
         PyObject_SetAttrString(m, "UTIME_NOW", value);
         Py_DECREF(value);
     }
-#pragma clang diagnostic pop  // ignored "-Wtautological-compare"
 #endif
+    {
+        PyObject *value;
+        const long arg_max = sysconf(_SC_ARG_MAX);
+        if (arg_max == -1)
+        {
+            fprintf(stderr, "Cannot find SC_ARG_MAX, please report a bug.\n");
+            exit(1);
+        }
+        value = INTEGER_TO_PY(arg_max);
+        PyObject_SetAttrString(m, "SC_ARG_MAX", value);
+        Py_DECREF(value);
+    }
+#pragma clang diagnostic pop  // ignored "-Wtautological-compare"
 
     e = getenv("BUP_FORCE_TTY");
     istty2 = isatty(2) || (atoi(e ? e : "0") & 2);