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draw: check for an integer overflow when computing stride 

Our buffer overflow arithmetic was susceptible to integer
overflows which was the buffer overflow logic to break.
Lets use the llvm overflow intrinsics to check for integer
overflows while computing the stride/needed buffer size.

Signed-off-by: Zack Rusin <zackr@vmware.com>
This commit is contained in:
Zack Rusin 2013-06-25 16:14:06 -04:00
parent e742f7788e
commit 2f13f28120
1 changed files with 44 additions and 11 deletions
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55
src/gallium/auxiliary/draw/draw_llvm.c
View File

@ -699,6 +699,13 @@ generate_fetch(struct gallivm_state *gallivm,
LLVMValueRef temp_ptr =
lp_build_alloca(gallivm,
lp_build_vec_type(gallivm, lp_float32_vec4_type()), "");
LLVMValueRef ofbit, oresult;
LLVMTypeRef oelems[2] = {
LLVMInt32TypeInContext(gallivm->context),
LLVMInt1TypeInContext(gallivm->context)
};
LLVMTypeRef otype = LLVMStructTypeInContext(gallivm->context,
oelems, 2, FALSE);
struct lp_build_if_state if_ctx;
if (velem->instance_divisor) {
@ -708,23 +715,49 @@ generate_fetch(struct gallivm_state *gallivm,
"instance_divisor");
}
stride = LLVMBuildMul(builder, vb_stride, index, "");
oresult = lp_build_intrinsic_binary(builder,
"llvm.umul.with.overflow.i32",
otype, vb_stride, index);
ofbit = LLVMBuildExtractValue(builder, oresult, 1, "");
stride = LLVMBuildExtractValue(builder, oresult, 0, "");
stride = LLVMBuildAdd(builder, stride,
vb_buffer_offset,
"");
stride = LLVMBuildAdd(builder, stride,
lp_build_const_int32(gallivm, velem->src_offset),
"");
needed_buffer_size = LLVMBuildAdd(
builder, stride,
lp_build_const_int32(gallivm,
util_format_get_blocksize(velem->src_format)),
oresult = lp_build_intrinsic_binary(builder,
"llvm.uadd.with.overflow.i32",
otype, stride, vb_buffer_offset);
ofbit = LLVMBuildOr(
builder, ofbit,
LLVMBuildExtractValue(builder, oresult, 1, ""),
"");
stride = LLVMBuildExtractValue(builder, oresult, 0, "");
oresult = lp_build_intrinsic_binary(
builder,
"llvm.uadd.with.overflow.i32",
otype, stride,
lp_build_const_int32(gallivm, velem->src_offset));
ofbit = LLVMBuildOr(
builder, ofbit,
LLVMBuildExtractValue(builder, oresult, 1, ""),
"");
stride = LLVMBuildExtractValue(builder, oresult, 0, "");
oresult = lp_build_intrinsic_binary(
builder,
"llvm.uadd.with.overflow.i32",
otype, stride,
lp_build_const_int32(gallivm,
util_format_get_blocksize(velem->src_format)));
ofbit = LLVMBuildOr(
builder, ofbit,
LLVMBuildExtractValue(builder, oresult, 1, ""),
"");
needed_buffer_size = LLVMBuildExtractValue(builder, oresult, 0, "");
buffer_overflowed = LLVMBuildICmp(builder, LLVMIntUGT,
needed_buffer_size, buffer_size,
"buffer_overflowed");
buffer_overflowed = LLVMBuildOr(builder, buffer_overflowed, ofbit, "");
#if 0
lp_build_printf(gallivm, "vbuf index = %u, vb_stride is %u\n",
index, vb_stride);