[CFI] Remove function pointer casts

Control Flow Integrity [1] indirect call checking verifies that function
pointers only call valid functions with a matching type signature. This
change eliminates function pointer casts to make libvpx CFI-safe.

[1] https://www.chromium.org/developers/testing/control-flow-integrity

Change-Id: I7e08522d195a43c88cda06fa20414426c8c4372c

6 files changed, 22 insertions, 15 deletions

diff --git a/vp9/common/vp9_loopfilter.c b/vp9/common/vp9_loopfilter.c
index be425d638..c7c343aed 100644
--- a/vp9/common/vp9_loopfilter.c
+++ b/vp9/common/vp9_loopfilter.c
@@ -1618,7 +1618,8 @@ void vp9_reset_lfm(VP9_COMMON *const cm) {
   }
 }
 
-int vp9_loop_filter_worker(LFWorkerData *const lf_data, void *unused) {
+int vp9_loop_filter_worker(void *arg1, void *unused) {
+  LFWorkerData *const lf_data = (LFWorkerData *)arg1;
   (void)unused;
   loop_filter_rows(lf_data->frame_buffer, lf_data->cm, lf_data->planes,
                    lf_data->start, lf_data->stop, lf_data->y_only);
diff --git a/vp9/common/vp9_loopfilter.h b/vp9/common/vp9_loopfilter.h
index da37a6ebd..481a6cdc6 100644
--- a/vp9/common/vp9_loopfilter.h
+++ b/vp9/common/vp9_loopfilter.h
@@ -151,8 +151,8 @@ void vp9_loop_filter_data_reset(
     LFWorkerData *lf_data, YV12_BUFFER_CONFIG *frame_buffer,
     struct VP9Common *cm, const struct macroblockd_plane planes[MAX_MB_PLANE]);
 
-// Operates on the rows described by 'lf_data'.
-int vp9_loop_filter_worker(LFWorkerData *const lf_data, void *unused);
+// Operates on the rows described by 'arg1' (cast to LFWorkerData *).
+int vp9_loop_filter_worker(void *arg1, void *unused);
 #ifdef __cplusplus
 }  // extern "C"
 #endif
diff --git a/vp9/common/vp9_thread_common.c b/vp9/common/vp9_thread_common.c
index 07e659d23..8d44e91f2 100644
--- a/vp9/common/vp9_thread_common.c
+++ b/vp9/common/vp9_thread_common.c
@@ -140,8 +140,9 @@ static INLINE void thread_loop_filter_rows(
 }
 
 // Row-based multi-threaded loopfilter hook
-static int loop_filter_row_worker(VP9LfSync *const lf_sync,
-                                  LFWorkerData *const lf_data) {
+static int loop_filter_row_worker(void *arg1, void *arg2) {
+  VP9LfSync *const lf_sync = (VP9LfSync *)arg1;
+  LFWorkerData *const lf_data = (LFWorkerData *)arg2;
   thread_loop_filter_rows(lf_data->frame_buffer, lf_data->cm, lf_data->planes,
                           lf_data->start, lf_data->stop, lf_data->y_only,
                           lf_sync);
@@ -183,7 +184,7 @@ static void loop_filter_rows_mt(YV12_BUFFER_CONFIG *frame, VP9_COMMON *cm,
     VPxWorker *const worker = &workers[i];
     LFWorkerData *const lf_data = &lf_sync->lfdata[i];
 
-    worker->hook = (VPxWorkerHook)loop_filter_row_worker;
+    worker->hook = loop_filter_row_worker;
     worker->data1 = lf_sync;
     worker->data2 = lf_data;
 
diff --git a/vp9/decoder/vp9_decodeframe.c b/vp9/decoder/vp9_decodeframe.c
index 9452ec4dc..d0e896c13 100644
--- a/vp9/decoder/vp9_decodeframe.c
+++ b/vp9/decoder/vp9_decodeframe.c
@@ -1364,7 +1364,7 @@ static const uint8_t *decode_tiles(VP9Decoder *pbi, const uint8_t *data,
       pbi->lf_worker.data1 == NULL) {
     CHECK_MEM_ERROR(cm, pbi->lf_worker.data1,
                     vpx_memalign(32, sizeof(LFWorkerData)));
-    pbi->lf_worker.hook = (VPxWorkerHook)vp9_loop_filter_worker;
+    pbi->lf_worker.hook = vp9_loop_filter_worker;
     if (pbi->max_threads > 1 && !winterface->reset(&pbi->lf_worker)) {
       vpx_internal_error(&cm->error, VPX_CODEC_ERROR,
                          "Loop filter thread creation failed");
@@ -1474,8 +1474,10 @@ static const uint8_t *decode_tiles(VP9Decoder *pbi, const uint8_t *data,
 // On entry 'tile_data->data_end' points to the end of the input frame, on exit
 // it is updated to reflect the bitreader position of the final tile column if
 // present in the tile buffer group or NULL otherwise.
-static int tile_worker_hook(TileWorkerData *const tile_data,
-                            VP9Decoder *const pbi) {
+static int tile_worker_hook(void *arg1, void *arg2) {
+  TileWorkerData *const tile_data = (TileWorkerData *)arg1;
+  VP9Decoder *const pbi = (VP9Decoder *)arg2;
+
   TileInfo *volatile tile = &tile_data->xd.tile;
   const int final_col = (1 << pbi->common.log2_tile_cols) - 1;
   const uint8_t *volatile bit_reader_end = NULL;
@@ -1569,7 +1571,7 @@ static const uint8_t *decode_tiles_mt(VP9Decoder *pbi, const uint8_t *data,
     tile_data->xd = pbi->mb;
     tile_data->xd.counts =
         cm->frame_parallel_decoding_mode ? NULL : &tile_data->counts;
-    worker->hook = (VPxWorkerHook)tile_worker_hook;
+    worker->hook = tile_worker_hook;
     worker->data1 = tile_data;
     worker->data2 = pbi;
   }
diff --git a/vp9/encoder/vp9_bitstream.c b/vp9/encoder/vp9_bitstream.c
index 8433f4edd..d346cd57a 100644
--- a/vp9/encoder/vp9_bitstream.c
+++ b/vp9/encoder/vp9_bitstream.c
@@ -919,7 +919,9 @@ int vp9_get_refresh_mask(VP9_COMP *cpi) {
   }
 }
 
-static int encode_tile_worker(VP9_COMP *cpi, VP9BitstreamWorkerData *data) {
+static int encode_tile_worker(void *arg1, void *arg2) {
+  VP9_COMP *cpi = (VP9_COMP *)arg1;
+  VP9BitstreamWorkerData *data = (VP9BitstreamWorkerData *)arg2;
   MACROBLOCKD *const xd = &data->xd;
   const int tile_row = 0;
   vpx_start_encode(&data->bit_writer, data->dest);
@@ -995,7 +997,7 @@ static size_t encode_tiles_mt(VP9_COMP *cpi, uint8_t *data_ptr) {
       }
       worker->data1 = cpi;
       worker->data2 = data;
-      worker->hook = (VPxWorkerHook)encode_tile_worker;
+      worker->hook = encode_tile_worker;
       worker->had_error = 0;
 
       if (i < num_workers - 1) {
diff --git a/vp9/encoder/vp9_ethread.c b/vp9/encoder/vp9_ethread.c
index d182ec765..6c5004c6c 100644
--- a/vp9/encoder/vp9_ethread.c
+++ b/vp9/encoder/vp9_ethread.c
@@ -35,7 +35,8 @@ static void accumulate_rd_opt(ThreadData *td, ThreadData *td_t) {
                   td_t->rd_counts.coef_counts[i][j][k][l][m][n];
 }
 
-static int enc_worker_hook(EncWorkerData *const thread_data, void *unused) {
+static int enc_worker_hook(void *arg1, void *unused) {
+  EncWorkerData *const thread_data = (EncWorkerData *)arg1;
   VP9_COMP *const cpi = thread_data->cpi;
   const VP9_COMMON *const cm = &cpi->common;
   const int tile_cols = 1 << cm->log2_tile_cols;
@@ -142,7 +143,7 @@ static void launch_enc_workers(VP9_COMP *cpi, VPxWorkerHook hook, void *data2,
 
   for (i = 0; i < num_workers; i++) {
     VPxWorker *const worker = &cpi->workers[i];
-    worker->hook = (VPxWorkerHook)hook;
+    worker->hook = hook;
     worker->data1 = &cpi->tile_thr_data[i];
     worker->data2 = data2;
   }
@@ -210,7 +211,7 @@ void vp9_encode_tiles_mt(VP9_COMP *cpi) {
     }
   }
 
-  launch_enc_workers(cpi, (VPxWorkerHook)enc_worker_hook, NULL, num_workers);
+  launch_enc_workers(cpi, enc_worker_hook, NULL, num_workers);
 
   for (i = 0; i < num_workers; i++) {
     VPxWorker *const worker = &cpi->workers[i];