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mesa: fix display list 8-byte alignment issue

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The _mesa_dlist_alloc() function is only guaranteed to return a pointer
with 4-byte alignment.  On 64-bit systems which don't support unaligned
loads (e.g. SPARC or MIPS) this could lead to a bus error in the VBO code.

The solution is to add a new  _mesa_dlist_alloc_aligned() function which
will return a pointer to an 8-byte aligned address on 64-bit systems.
This is accomplished by inserting a 4-byte NOP instruction in the display
list when needed.

The only place this actually matters is the VBO code where we need to
allocate a 'struct vbo_save_vertex_list' which needs to be 8-byte
aligned (just as if it were malloc'd).

The gears demo and others hit this bug.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=88662
Cc: "10.4" <mesa-stable@lists.freedesktop.org>
Reviewed-by: José Fonseca <jfonseca@vmware.com>
This commit is contained in:
Brian Paul
2015-01-26 20:32:58 -07:00
parent fbc3e030e6
commit 53b01938ed
3 changed files with 74 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/mesa/main/dlist.c
+67 -6
View File
@@ -487,6 +487,7 @@ typedef enum
/* The following three are meta instructions */
OPCODE_ERROR, /* raise compiled-in error */
OPCODE_CONTINUE,
OPCODE_NOP, /* No-op (used for 8-byte alignment */
OPCODE_END_OF_LIST,
OPCODE_EXT_0
} OpCode;
@@ -1012,13 +1013,16 @@ memdup(const void *src, GLsizei bytes)
* Allocate space for a display list instruction (opcode + payload space).
* \param opcode the instruction opcode (OPCODE_* value)
* \param bytes instruction payload size (not counting opcode)
* \return pointer to allocated memory (the opcode space)
* \param align8 does the payload need to be 8-byte aligned?
* This is only relevant in 64-bit environments.
* \return pointer to allocated memory (the payload will be at pointer+1)
*/
static Node *
dlist_alloc(struct gl_context *ctx, OpCode opcode, GLuint bytes)
dlist_alloc(struct gl_context *ctx, OpCode opcode, GLuint bytes, bool align8)
{
const GLuint numNodes = 1 + (bytes + sizeof(Node) - 1) / sizeof(Node);
const GLuint contNodes = 1 + POINTER_DWORDS; /* size of continue info */
GLuint nopNode;
Node *n;
if (opcode < OPCODE_EXT_0) {
@@ -1032,7 +1036,20 @@ dlist_alloc(struct gl_context *ctx, OpCode opcode, GLuint bytes)
}
}
if (ctx->ListState.CurrentPos + numNodes + contNodes > BLOCK_SIZE) {
if (sizeof(void *) > sizeof(Node) && align8
&& ctx->ListState.CurrentPos % 2 == 0) {
/* The opcode would get placed at node[0] and the payload would start
* at node[1]. But the payload needs to be at an even offset (8-byte
* multiple).
*/
nopNode = 1;
}
else {
nopNode = 0;
}
if (ctx->ListState.CurrentPos + nopNode + numNodes + contNodes
> BLOCK_SIZE) {
/* This block is full. Allocate a new block and chain to it */
Node *newblock;
n = ctx->ListState.CurrentBlock + ctx->ListState.CurrentPos;
@@ -1042,13 +1059,34 @@ dlist_alloc(struct gl_context *ctx, OpCode opcode, GLuint bytes)
_mesa_error(ctx, GL_OUT_OF_MEMORY, "Building display list");
return NULL;
}
/* a fresh block should be 8-byte aligned on 64-bit systems */
assert(((GLintptr) newblock) % sizeof(void *) == 0);
save_pointer(&n[1], newblock);
ctx->ListState.CurrentBlock = newblock;
ctx->ListState.CurrentPos = 0;
/* Display list nodes are always 4 bytes. If we need 8-byte alignment
* we have to insert a NOP so that the payload of the real opcode lands
* on an even location:
* node[0] = OPCODE_NOP
* node[1] = OPCODE_x;
* node[2] = start of payload
*/
nopNode = sizeof(void *) > sizeof(Node) && align8;
}
n = ctx->ListState.CurrentBlock + ctx->ListState.CurrentPos;
ctx->ListState.CurrentPos += numNodes;
if (nopNode) {
assert(ctx->ListState.CurrentPos % 2 == 0); /* even value */
n[0].opcode = OPCODE_NOP;
n++;
/* The "real" opcode will now be at an odd location and the payload
* will be at an even location.
*/
}
ctx->ListState.CurrentPos += nopNode + numNodes;
n[0].opcode = opcode;
@@ -1069,7 +1107,22 @@ dlist_alloc(struct gl_context *ctx, OpCode opcode, GLuint bytes)
void *
_mesa_dlist_alloc(struct gl_context *ctx, GLuint opcode, GLuint bytes)
{
Node *n = dlist_alloc(ctx, (OpCode) opcode, bytes);
Node *n = dlist_alloc(ctx, (OpCode) opcode, bytes, false);
if (n)
return n + 1; /* return pointer to payload area, after opcode */
else
return NULL;
}
/**
* Same as _mesa_dlist_alloc(), but return a pointer which is 8-byte
* aligned in 64-bit environments, 4-byte aligned otherwise.
*/
void *
_mesa_dlist_alloc_aligned(struct gl_context *ctx, GLuint opcode, GLuint bytes)
{
Node *n = dlist_alloc(ctx, (OpCode) opcode, bytes, true);
if (n)
return n + 1; /* return pointer to payload area, after opcode */
else
@@ -1119,7 +1172,7 @@ _mesa_dlist_alloc_opcode(struct gl_context *ctx,
static inline Node *
alloc_instruction(struct gl_context *ctx, OpCode opcode, GLuint nparams)
{
return dlist_alloc(ctx, opcode, nparams * sizeof(Node));
return dlist_alloc(ctx, opcode, nparams * sizeof(Node), false);
}
@@ -8897,6 +8950,9 @@ execute_list(struct gl_context *ctx, GLuint list)
case OPCODE_CONTINUE:
n = (Node *) get_pointer(&n[1]);
break;
case OPCODE_NOP:
/* no-op */
break;
case OPCODE_END_OF_LIST:
done = GL_TRUE;
break;
@@ -9947,6 +10003,9 @@ print_list(struct gl_context *ctx, GLuint list, const char *fname)
fprintf(f, "DISPLAY-LIST-CONTINUE\n");
n = (Node *) get_pointer(&n[1]);
break;
case OPCODE_NOP:
fprintf(f, "NOP\n");
break;
case OPCODE_END_OF_LIST:
fprintf(f, "END-LIST %u\n", list);
done = GL_TRUE;
@@ -10097,6 +10156,8 @@ _mesa_init_display_list(struct gl_context *ctx)
ctx->List.ListBase = 0;
save_vtxfmt_init(&ctx->ListState.ListVtxfmt);
InstSize[OPCODE_NOP] = 1;
}
src/mesa/main/dlist.h
+3
View File
@@ -60,6 +60,9 @@ extern void _mesa_compile_error( struct gl_context *ctx, GLenum error, const cha
extern void *_mesa_dlist_alloc(struct gl_context *ctx, GLuint opcode, GLuint sz);
extern void *
_mesa_dlist_alloc_aligned(struct gl_context *ctx, GLuint opcode, GLuint bytes);
extern GLint _mesa_dlist_alloc_opcode( struct gl_context *ctx, GLuint sz,
void (*execute)( struct gl_context *, void * ),
void (*destroy)( struct gl_context *, void * ),
src/mesa/vbo/vbo_save_api.c
+4 -1
View File
@@ -375,11 +375,14 @@ _save_compile_vertex_list(struct gl_context *ctx)
* being compiled.
*/
node = (struct vbo_save_vertex_list *)
_mesa_dlist_alloc(ctx, save->opcode_vertex_list, sizeof(*node));
_mesa_dlist_alloc_aligned(ctx, save->opcode_vertex_list, sizeof(*node));
if (!node)
return;
/* Make sure the pointer is aligned to the size of a pointer */
assert((GLintptr) node % sizeof(void *) == 0);
/* Duplicate our template, increment refcounts to the storage structs:
*/
memcpy(node->attrsz, save->attrsz, sizeof(node->attrsz));