vsk created this revision.
vsk added reviewers: labath, zturner, jingham, aprantl.
vsk edited the summary of this revision.
This prevents Malloc from allocating the same chunk of memory twice, as
a byproduct of an alignment adjustment which gave the client access to
unallocated memory.
Prior to this patch, the newly-added test failed with:
$ lldb-test ir-memory-map ... ir-memory-map-overlap1.test
Command: malloc(size=8, alignment=16)
Malloc: address = 0x1000cd000
Command: malloc(size=16, alignment=8)
Malloc: address = 0x1000cd010
Command: malloc(size=64, alignment=32)
Malloc: address = 0x1000cd020
Command: malloc(size=1, alignment=8)
Malloc: address = 0x1000cd060
Command: malloc(size=64, alignment=32)
Malloc: address = 0x1000cd080
Command: malloc(size=64, alignment=8)
Malloc: address = 0x1000cd0b0
Malloc error: overlapping allocation detected, previous allocation at
[0x1000cd080, 0x1000cd0c0)
I don't see anything controversial here (in fact Jim lgtm'd part of this patch
off-list), but as this is unfamiliar territory for me I think it'd help to have
a proper review. Depends on https://reviews.llvm.org/D47508.
https://reviews.llvm.org/D47551
Files:
lit/Expr/Inputs/ir-memory-map-basic.test
lit/Expr/Inputs/ir-memory-map-overlap1.test
lit/Expr/TestIRMemoryMap.test
source/Expression/IRMemoryMap.cpp
Index: source/Expression/IRMemoryMap.cpp
===================================================================
--- source/Expression/IRMemoryMap.cpp
+++ source/Expression/IRMemoryMap.cpp
@@ -304,12 +304,25 @@
size_t alignment_mask = alignment - 1;
size_t allocation_size;
- if (size == 0)
+ if (size == 0) {
+ // FIXME: Malloc(0) should either return an invalid address or assert, in
+ // order to cut down on unnecessary allocations.
allocation_size = alignment;
- else
- allocation_size = (size & alignment_mask)
- ? ((size + alignment) & (~alignment_mask))
- : size;
+ } else {
+ // Round up the requested size to an aligned value, if needed.
+ if (size & alignment_mask)
+ allocation_size = ((size + alignment) & (~alignment_mask));
+ else
+ allocation_size = size;
+
+ // The process page cache does not see the requested alignment. We can't
+ // assume its result will be any more than 1-byte aligned. To work around
+ // this, request `alignment` additional bytes.
+ //
+ // FIXME: Pass the requested alignment into the process page cache to
+ // reduce internal fragmentation.
+ allocation_size += alignment;
+ }
switch (policy) {
default:
Index: lit/Expr/TestIRMemoryMap.test
===================================================================
--- lit/Expr/TestIRMemoryMap.test
+++ lit/Expr/TestIRMemoryMap.test
@@ -1,28 +1,3 @@
# RUN: %cxx %p/Inputs/call-function.cpp -g -o %t
-# RUN: lldb-test ir-memory-map %t %s
-
-malloc 0 1
-malloc 1 1
-
-malloc 2 1
-malloc 2 2
-malloc 2 4
-
-malloc 3 1
-malloc 3 2
-malloc 3 4
-
-malloc 128 1
-malloc 128 2
-malloc 128 4
-malloc 128 128
-
-malloc 2048 1
-malloc 2048 2
-malloc 2048 4
-
-malloc 3968 1
-malloc 3968 2
-malloc 3968 4
-
-malloc 0 1
+# RUN: lldb-test ir-memory-map %t %S/Inputs/ir-memory-map-basic.test
+# RUN: lldb-test ir-memory-map %t %S/Inputs/ir-memory-map-overlap1.test
Index: lit/Expr/Inputs/ir-memory-map-overlap1.test
===================================================================
--- /dev/null
+++ lit/Expr/Inputs/ir-memory-map-overlap1.test
@@ -0,0 +1,10 @@
+malloc 8 16
+malloc 16 8
+malloc 64 32
+malloc 1 8
+malloc 64 32
+malloc 64 8
+malloc 1024 32
+malloc 1 16
+malloc 8 16
+malloc 1024 16
\ No newline at end of file
Index: lit/Expr/Inputs/ir-memory-map-basic.test
===================================================================
--- /dev/null
+++ lit/Expr/Inputs/ir-memory-map-basic.test
@@ -0,0 +1,25 @@
+malloc 0 1
+malloc 1 1
+
+malloc 2 1
+malloc 2 2
+malloc 2 4
+
+malloc 3 1
+malloc 3 2
+malloc 3 4
+
+malloc 128 1
+malloc 128 2
+malloc 128 4
+malloc 128 128
+
+malloc 2048 1
+malloc 2048 2
+malloc 2048 4
+
+malloc 3968 1
+malloc 3968 2
+malloc 3968 4
+
+malloc 0 1
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