From: Olaf Hering <o...@aepfle.de>

Currently this warning is triggered when compiling hv_fcopy_daemon:

hv_fcopy_daemon.c:216:4: warning: dereferencing type-punned pointer will break
strict-aliasing rules [-Wstrict-aliasing]
    kernel_modver = *(__u32 *)buffer;

Convert the send/receive buffer to a union and pass individual members as
needed. This also gives the correct size for the buffer.

Signed-off-by: Olaf Hering <o...@aepfle.de>
Signed-off-by: K. Y. Srinivasan <k...@microsoft.com>
---
 tools/hv/hv_fcopy_daemon.c |   32 +++++++++++++++++---------------
 1 files changed, 17 insertions(+), 15 deletions(-)

diff --git a/tools/hv/hv_fcopy_daemon.c b/tools/hv/hv_fcopy_daemon.c
index 26ae609..457a152 100644
--- a/tools/hv/hv_fcopy_daemon.c
+++ b/tools/hv/hv_fcopy_daemon.c
@@ -138,14 +138,17 @@ void print_usage(char *argv[])
 
 int main(int argc, char *argv[])
 {
-       int fcopy_fd, len;
+       int fcopy_fd;
        int error;
        int daemonize = 1, long_index = 0, opt;
        int version = FCOPY_CURRENT_VERSION;
-       char *buffer[4096 * 2];
-       struct hv_fcopy_hdr *in_msg;
+       union {
+               struct hv_fcopy_hdr hdr;
+               struct hv_start_fcopy start;
+               struct hv_do_fcopy copy;
+               __u32 kernel_modver;
+       } buffer = { };
        int in_handshake = 1;
-       __u32 kernel_modver;
 
        static struct option long_options[] = {
                {"help",        no_argument,       0,  'h' },
@@ -195,32 +198,31 @@ int main(int argc, char *argv[])
                 * In this loop we process fcopy messages after the
                 * handshake is complete.
                 */
-               len = pread(fcopy_fd, buffer, (4096 * 2), 0);
+               ssize_t len;
+
+               len = pread(fcopy_fd, &buffer, sizeof(buffer), 0);
                if (len < 0) {
                        syslog(LOG_ERR, "pread failed: %s", strerror(errno));
                        exit(EXIT_FAILURE);
                }
 
                if (in_handshake) {
-                       if (len != sizeof(kernel_modver)) {
+                       if (len != sizeof(buffer.kernel_modver)) {
                                syslog(LOG_ERR, "invalid version negotiation");
                                exit(EXIT_FAILURE);
                        }
-                       kernel_modver = *(__u32 *)buffer;
                        in_handshake = 0;
-                       syslog(LOG_INFO, "kernel module version: %d",
-                              kernel_modver);
+                       syslog(LOG_INFO, "kernel module version: %u",
+                              buffer.kernel_modver);
                        continue;
                }
 
-               in_msg = (struct hv_fcopy_hdr *)buffer;
-
-               switch (in_msg->operation) {
+               switch (buffer.hdr.operation) {
                case START_FILE_COPY:
-                       error = hv_start_fcopy((struct hv_start_fcopy *)in_msg);
+                       error = hv_start_fcopy(&buffer.start);
                        break;
                case WRITE_TO_FILE:
-                       error = hv_copy_data((struct hv_do_fcopy *)in_msg);
+                       error = hv_copy_data(&buffer.copy);
                        break;
                case COMPLETE_FCOPY:
                        error = hv_copy_finished();
@@ -231,7 +233,7 @@ int main(int argc, char *argv[])
 
                default:
                        syslog(LOG_ERR, "Unknown operation: %d",
-                               in_msg->operation);
+                               buffer.hdr.operation);
 
                }
 
-- 
1.7.1

Reply via email to