[Mesa-dev] [PATCH 2/2] draw: fix overflows in the indexed rendering paths
Roland Scheidegger
sroland at vmware.com
Wed Jul 3 14:52:16 PDT 2013
Am 03.07.2013 07:42, schrieb Zack Rusin:
> The semantics for overflow detection are a bit tricky with
> indexed rendering. If the base index in the elements array
> overflows, then the index of the first element should be used,
> if the index with bias overflows then it should be treated
> like a normal overflow. Also overflows need to be checked for
> in all paths that either the bias, or the starting index location.
>
> Signed-off-by: Zack Rusin <zackr at vmware.com>
> ---
> src/gallium/auxiliary/draw/draw_private.h | 19 +++-
> src/gallium/auxiliary/draw/draw_pt.c | 6 +-
> src/gallium/auxiliary/draw/draw_pt_vsplit.c | 108 ++++++++++++++++++++---
> src/gallium/auxiliary/draw/draw_pt_vsplit_tmp.h | 54 +++++++-----
> 4 files changed, 146 insertions(+), 41 deletions(-)
>
> diff --git a/src/gallium/auxiliary/draw/draw_private.h b/src/gallium/auxiliary/draw/draw_private.h
> index f42cded..a20bfdf 100644
> --- a/src/gallium/auxiliary/draw/draw_private.h
> +++ b/src/gallium/auxiliary/draw/draw_private.h
> @@ -472,10 +472,10 @@ draw_stats_clipper_primitives(struct draw_context *draw,
> /**
> * Return index i from the index buffer.
> * If the index buffer would overflow we return the
> - * index of the first element in the vb.
> + * maximum possible index.
> */
> #define DRAW_GET_IDX(_elts, _i) \
> - (((_i) >= draw->pt.user.eltMax) ? 0 : (_elts)[_i])
> + (((_i) >= draw->pt.user.eltMax) ? 0xffffffff : (_elts)[_i])
>
> /**
> * Return index of the given viewport clamping it
> @@ -487,5 +487,20 @@ draw_clamp_viewport_idx(int idx)
> return ((PIPE_MAX_VIEWPORTS > idx || idx < 0) ? idx : 0);
> }
>
> +/**
> + * Adds two unsigned integers and if the addition
> + * overflows then it returns the value from
> + * from the overflow_value variable.
> + */
> +static INLINE unsigned
> +draw_overflow_uadd(unsigned a, unsigned b,
> + unsigned overflow_value)
> +{
> + unsigned res = a + b;
> + if (res < a || res < b) {
> + res = overflow_value;
> + }
> + return res;
> +}
>
> #endif /* DRAW_PRIVATE_H */
> diff --git a/src/gallium/auxiliary/draw/draw_pt.c b/src/gallium/auxiliary/draw/draw_pt.c
> index e89ccd2..5b41ea8 100644
> --- a/src/gallium/auxiliary/draw/draw_pt.c
> +++ b/src/gallium/auxiliary/draw/draw_pt.c
> @@ -345,7 +345,8 @@ draw_print_arrays(struct draw_context *draw, uint prim, int start, uint count)
> /** Helper code for below */
> #define PRIM_RESTART_LOOP(elements) \
> do { \
> - for (i = start; i < end; i++) { \
> + for (j = 0; j < count; j++) { \
> + i = draw_overflow_uadd(start, j, 0xffffffff); \
> if (i < elt_max && elements[i] == info->restart_index) { \
> if (cur_count > 0) { \
> /* draw elts up to prev pos */ \
> @@ -377,9 +378,8 @@ draw_pt_arrays_restart(struct draw_context *draw,
> const unsigned prim = info->mode;
> const unsigned start = info->start;
> const unsigned count = info->count;
> - const unsigned end = start + count;
> const unsigned elt_max = draw->pt.user.eltMax;
> - unsigned i, cur_start, cur_count;
> + unsigned i, j, cur_start, cur_count;
>
> assert(info->primitive_restart);
>
> diff --git a/src/gallium/auxiliary/draw/draw_pt_vsplit.c b/src/gallium/auxiliary/draw/draw_pt_vsplit.c
> index 114c89c..02f5c89 100644
> --- a/src/gallium/auxiliary/draw/draw_pt_vsplit.c
> +++ b/src/gallium/auxiliary/draw/draw_pt_vsplit.c
> @@ -33,6 +33,8 @@
> #define SEGMENT_SIZE 1024
> #define MAP_SIZE 256
>
> +#define MAX_ELT_IDX 0xffffffff
> +
> struct vsplit_frontend {
> struct draw_pt_front_end base;
> struct draw_context *draw;
> @@ -82,16 +84,15 @@ vsplit_flush_cache(struct vsplit_frontend *vsplit, unsigned flags)
> * Add a fetch element and add it to the draw elements.
> */
> static INLINE void
> -vsplit_add_cache(struct vsplit_frontend *vsplit, unsigned fetch)
> +vsplit_add_cache(struct vsplit_frontend *vsplit, unsigned fetch, unsigned ofbias)
> {
> - struct draw_context *draw = vsplit->draw;
> unsigned hash;
>
> - fetch = MIN2(fetch, draw->pt.max_index);
> -
> hash = fetch % MAP_SIZE;
>
> - if (vsplit->cache.fetches[hash] != fetch) {
> + /* If the value isn't in the cache of it's an overflow due to the
> + * element bias */
> + if (vsplit->cache.fetches[hash] != fetch || ofbias) {
> /* update cache */
> vsplit->cache.fetches[hash] = fetch;
> vsplit->cache.draws[hash] = vsplit->cache.num_fetch_elts;
> @@ -104,22 +105,105 @@ vsplit_add_cache(struct vsplit_frontend *vsplit, unsigned fetch)
> vsplit->draw_elts[vsplit->cache.num_draw_elts++] = vsplit->cache.draws[hash];
> }
>
> +/**
> + * Returns the base index to the elements array.
> + * The value is checked for overflows (both integer overflows
> + * and the elements array overflow).
> + */
> +static INLINE unsigned
> +vsplit_get_base_idx(struct vsplit_frontend *vsplit,
> + unsigned start, unsigned fetch, unsigned *ofbit)
> +{
> + struct draw_context *draw = vsplit->draw;
> + unsigned elt_idx = draw_overflow_uadd(start, fetch, MAX_ELT_IDX);
> + if (ofbit) *ofbit = 0;
> +
> + /* Overflown indices need to wrap to the first element
> + * in the index buffer */
> + if (elt_idx >= draw->pt.user.eltMax) {
> + if (ofbit) *ofbit = 1;
> + elt_idx = 0;
> + }
> +
> + return elt_idx;
> +}
> +
> +/**
> + * Returns the element index adjust for the element bias.
> + * The final element index is created from the actual element
> + * index, plus the element bias, clamped to maximum elememt
> + * index if that addition overflows.
> + */
> +static INLINE unsigned
> +vsplit_get_bias_idx(struct vsplit_frontend *vsplit,
> + int idx, int bias, unsigned *ofbias)
> +{
> + int res = idx + bias;
> +
> + if (ofbias) *ofbias = 0;
> +
> + if (idx > 0 && bias > 0) {
> + if (res < idx || res < bias) {
> + res = MAX_ELT_IDX;
> + if (ofbias) *ofbias = 1;
> + }
> + } else if (idx < 0 && bias < 0) {
> + if (res > idx || res > bias) {
> + res = MAX_ELT_IDX;
> + if (ofbias) *ofbias = 1;
> + }
> + }
> +
> + return res;
> +}
> +
> +#define VSPLIT_CREATE_IDX(elts, start, fetch, elt_bias) \
> + unsigned elt_idx; \
> + unsigned ofbit; \
> + unsigned ofbias; \
> + elt_idx = vsplit_get_base_idx(vsplit, start, fetch, &ofbit); \
> + elt_idx = vsplit_get_bias_idx(vsplit, ofbit ? 0 : DRAW_GET_IDX(elts, elt_idx), elt_bias, &ofbias)
> +
> +static INLINE void
> +vsplit_add_cache_ubyte(struct vsplit_frontend *vsplit, const ubyte *elts,
> + unsigned start, unsigned fetch, int elt_bias)
> +{
> + struct draw_context *draw = vsplit->draw;
> + VSPLIT_CREATE_IDX(elts, start, fetch, elt_bias);
> +
> + vsplit_add_cache(vsplit, elt_idx, ofbias);
> +}
> +
> +static INLINE void
> +vsplit_add_cache_ushort(struct vsplit_frontend *vsplit, const ushort *elts,
> + unsigned start, unsigned fetch, int elt_bias)
> +{
> + struct draw_context *draw = vsplit->draw;
> + VSPLIT_CREATE_IDX(elts, start, fetch, elt_bias);
> + vsplit_add_cache(vsplit, elt_idx, ofbias);
> +}
> +
>
> /**
> * Add a fetch element and add it to the draw elements. The fetch element is
> * in full range (uint).
> */
> static INLINE void
> -vsplit_add_cache_uint(struct vsplit_frontend *vsplit, unsigned fetch)
> +vsplit_add_cache_uint(struct vsplit_frontend *vsplit, const uint *elts,
> + unsigned start, unsigned fetch, int elt_bias)
> {
> + struct draw_context *draw = vsplit->draw;
> + unsigned raw_elem_idx = start + fetch + elt_bias;
> + VSPLIT_CREATE_IDX(elts, start, fetch, elt_bias);
> +
> /* special care for 0xffffffff */
> - if (fetch == 0xffffffff && !vsplit->cache.has_max_fetch) {
> + if (raw_elem_idx == 0xffffffff && !vsplit->cache.has_max_fetch) {
> unsigned hash = fetch % MAP_SIZE;
> - vsplit->cache.fetches[hash] = fetch - 1; /* force update */
> + vsplit->cache.fetches[hash] = raw_elem_idx - 1; /* force update */
> vsplit->cache.has_max_fetch = TRUE;
> }
>
> - vsplit_add_cache(vsplit, fetch);
> + vsplit_add_cache(vsplit, elt_idx, ofbias);
> }
>
>
> @@ -128,17 +212,17 @@ vsplit_add_cache_uint(struct vsplit_frontend *vsplit, unsigned fetch)
>
> #define FUNC vsplit_run_ubyte
> #define ELT_TYPE ubyte
> -#define ADD_CACHE(vsplit, fetch) vsplit_add_cache(vsplit, fetch)
> +#define ADD_CACHE(vsplit, ib, start, fetch, bias) vsplit_add_cache_ubyte(vsplit,ib,start,fetch,bias)
> #include "draw_pt_vsplit_tmp.h"
>
> #define FUNC vsplit_run_ushort
> #define ELT_TYPE ushort
> -#define ADD_CACHE(vsplit, fetch) vsplit_add_cache(vsplit, fetch)
> +#define ADD_CACHE(vsplit, ib, start, fetch, bias) vsplit_add_cache_ushort(vsplit,ib,start,fetch, bias)
> #include "draw_pt_vsplit_tmp.h"
>
> #define FUNC vsplit_run_uint
> #define ELT_TYPE uint
> -#define ADD_CACHE(vsplit, fetch) vsplit_add_cache_uint(vsplit, fetch)
> +#define ADD_CACHE(vsplit, ib, start, fetch, bias) vsplit_add_cache_uint(vsplit, ib, start, fetch, bias)
> #include "draw_pt_vsplit_tmp.h"
>
>
> diff --git a/src/gallium/auxiliary/draw/draw_pt_vsplit_tmp.h b/src/gallium/auxiliary/draw/draw_pt_vsplit_tmp.h
> index 34c210c..5d72ac6 100644
> --- a/src/gallium/auxiliary/draw/draw_pt_vsplit_tmp.h
> +++ b/src/gallium/auxiliary/draw/draw_pt_vsplit_tmp.h
> @@ -47,13 +47,20 @@ CONCAT(vsplit_primitive_, ELT_TYPE)(struct vsplit_frontend *vsplit,
> const unsigned start = istart;
> const unsigned end = istart + icount;
>
> + /* If the index buffer overflows we'll need to run
> + * through the normal paths */
> + if (start >= draw->pt.user.eltMax ||
> + end > draw->pt.user.eltMax ||
> + end < istart || end < icount)
> + return FALSE;
> +
> /* use the ib directly */
> if (min_index == 0 && sizeof(ib[0]) == sizeof(draw_elts[0])) {
> if (icount > vsplit->max_vertices)
> return FALSE;
>
> - for (i = start; i < end; i++) {
> - ELT_TYPE idx = DRAW_GET_IDX(ib, i);
> + for (i = 0; i < icount; i++) {
> + ELT_TYPE idx = DRAW_GET_IDX(ib, start + i);
> if (idx < min_index || idx > max_index) {
> debug_printf("warning: index out of range\n");
> }
> @@ -82,25 +89,29 @@ CONCAT(vsplit_primitive_, ELT_TYPE)(struct vsplit_frontend *vsplit,
> fetch_start = min_index + elt_bias;
> fetch_count = max_index - min_index + 1;
>
> + /* Check for overflow in the fetch_start */
> + if (fetch_start < min_index || fetch_start < elt_bias)
> + return FALSE;
> +
> if (!draw_elts) {
> if (min_index == 0) {
> - for (i = start; i < end; i++) {
> - ELT_TYPE idx = DRAW_GET_IDX(ib, i);
> + for (i = 0; i < icount; i++) {
> + ELT_TYPE idx = DRAW_GET_IDX(ib, i + start);
>
> if (idx < min_index || idx > max_index) {
> debug_printf("warning: index out of range\n");
> }
> - vsplit->draw_elts[i - start] = (ushort) idx;
> + vsplit->draw_elts[i] = (ushort) idx;
> }
> }
> else {
> - for (i = start; i < end; i++) {
> - ELT_TYPE idx = DRAW_GET_IDX(ib, i);
> + for (i = 0; i < icount; i++) {
> + ELT_TYPE idx = DRAW_GET_IDX(ib, i + start);
>
> if (idx < min_index || idx > max_index) {
> debug_printf("warning: index out of range\n");
> }
> - vsplit->draw_elts[i - start] = (ushort) (idx - min_index);
> + vsplit->draw_elts[i] = (ushort) (idx - min_index);
> }
> }
>
> @@ -137,41 +148,36 @@ CONCAT(vsplit_segment_cache_, ELT_TYPE)(struct vsplit_frontend *vsplit,
> spoken = !!spoken;
> if (ibias == 0) {
> if (spoken)
> - ADD_CACHE(vsplit, DRAW_GET_IDX(ib, ispoken));
> + ADD_CACHE(vsplit, ib, 0, ispoken, 0);
>
> - for (i = spoken; i < icount; i++)
> - ADD_CACHE(vsplit, DRAW_GET_IDX(ib, istart + i));
> + for (i = spoken; i < icount; i++) {
> + ADD_CACHE(vsplit, ib, istart, i, 0);
> + }
>
> if (close)
> - ADD_CACHE(vsplit, DRAW_GET_IDX(ib, iclose));
> + ADD_CACHE(vsplit, ib, 0, iclose, 0);
> }
> else if (ibias > 0) {
> if (spoken)
> - ADD_CACHE(vsplit, (uint) DRAW_GET_IDX(ib, ispoken) + ibias);
> + ADD_CACHE(vsplit, ib, 0, ispoken, ibias);
>
> for (i = spoken; i < icount; i++)
> - ADD_CACHE(vsplit, (uint) DRAW_GET_IDX(ib, istart + i) + ibias);
> + ADD_CACHE(vsplit, ib, istart, i, ibias);
>
> if (close)
> - ADD_CACHE(vsplit, (uint) DRAW_GET_IDX(ib, iclose) + ibias);
> + ADD_CACHE(vsplit, ib, 0, iclose, ibias);
> }
> else {
> if (spoken) {
> - if ((int) ib[ispoken] < -ibias)
> - return;
> - ADD_CACHE(vsplit, DRAW_GET_IDX(ib, ispoken) + ibias);
> + ADD_CACHE(vsplit, ib, 0, ispoken, ibias);
> }
>
> for (i = spoken; i < icount; i++) {
> - if ((int) DRAW_GET_IDX(ib, istart + i) < -ibias)
> - return;
> - ADD_CACHE(vsplit, DRAW_GET_IDX(ib, istart + i) + ibias);
> + ADD_CACHE(vsplit, ib, istart, i, ibias);
> }
>
> if (close) {
> - if ((int) DRAW_GET_IDX(ib, iclose) < -ibias)
> - return;
> - ADD_CACHE(vsplit, DRAW_GET_IDX(ib, iclose) + ibias);
> + ADD_CACHE(vsplit, ib, 0, iclose, ibias);
> }
> }
>
>
The necessary handling of overflows gives me a headache just by looking
at it but series looks good to me.
Roland
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