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mesa: new MESA_EXTENSION_MAX_YEAR env var

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If set to year X, only report extensions up to that year.  This is a
work-around for games that try to copy the extensions string to a fixed
size buffer and overflow.  If a game was released in year X, setting
MESA_EXTENSION_MAX_YEAR to that year will likely fix the problem.
This commit is contained in:
Brian Paul
2011-03-24 11:39:21 -06:00
parent 4c75d5ae63
commit 82dd62fb22
2 changed files with 25 additions and 2 deletions
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9
docs/envvars.html
View File

@@ -49,6 +49,15 @@ Setting this variable automatically sets the MESA_TEX_PROG variable as well.
<li>MESA_EXTENSION_OVERRIDE - can be used to enable/disable extensions.
A value such as "GL_EXT_foo -GL_EXT_bar" will enable the GL_EXT_foo extension
and disable the GL_EXT_bar extension.
<li>MESA_EXTENSION_MAX_YEAR - The GL_EXTENSIONS string returned by Mesa is sorted
by extension year.
If this variable is set to year X, only extensions defined on or before year
X will be reported.
This is to work-around a bug in some games where the extension string is
copied into a fixed-size buffer without truncating.
If the extension string is too long, the buffer overrun can cause the game
to crash.
This is a work-around for that.
<li>MESA_GLSL - <a href="shading.html#envvars">shading language compiler options</a>
</ul>

18
src/mesa/main/extensions.c
View File

@@ -875,12 +875,24 @@ _mesa_make_extension_string(struct gl_context *ctx)
GLboolean *base = (GLboolean *) &ctx->Extensions;
const struct extension *i;
unsigned j;
unsigned maxYear = ~0;
/* Check if the MESA_EXTENSION_MAX_YEAR env var is set */
{
const char *env = getenv("MESA_EXTENSION_MAX_YEAR");
if (env) {
maxYear = atoi(env);
_mesa_debug(ctx, "Note: limiting GL extensions to %u or earlier\n",
maxYear);
}
}
/* Compute length of the extension string. */
count = 0;
for (i = extension_table; i->name != 0; ++i) {
if (base[i->offset] && (i->api_set & (1 << ctx->API))) {
if (base[i->offset] &&
i->year <= maxYear &&
(i->api_set & (1 << ctx->API))) {
length += strlen(i->name) + 1; /* +1 for space */
++count;
}
@@ -908,7 +920,9 @@ _mesa_make_extension_string(struct gl_context *ctx)
*/
j = 0;
for (i = extension_table; i->name != 0; ++i) {
if (base[i->offset] && (i->api_set & (1 << ctx->API))) {
if (base[i->offset] &&
i->year <= maxYear &&
(i->api_set & (1 << ctx->API))) {
extension_indices[j++] = i - extension_table;
}
}