vsk updated this revision to Diff 241602.
vsk retitled this revision from "[lldb/Value] Report size of Value as size of
underlying data buffer" to "[lldb/Value] Avoid reading more data than the host
has available".
vsk edited the summary of this revision.
vsk added a comment.
Address review feedback:
- Add a test that doesn't depend on the compiler.
- Convert the old test into a simpler regression test.
- Based on feedback from Jim, don't try to change the definition of a Value's
size, as the expectation that the type is correct is baked in deeply.
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D73148/new/
https://reviews.llvm.org/D73148
Files:
lldb/packages/Python/lldbsuite/test/functionalities/optimized_code/Makefile
lldb/packages/Python/lldbsuite/test/functionalities/optimized_code/TestNoASanExceptionAfterEvalOP_piece.py
lldb/packages/Python/lldbsuite/test/functionalities/optimized_code/main.cpp
lldb/source/Core/Value.cpp
lldb/test/Shell/SymbolFile/DWARF/DW_OP_piece-smaller-than-struct.s
Index: lldb/test/Shell/SymbolFile/DWARF/DW_OP_piece-smaller-than-struct.s
===================================================================
--- /dev/null
+++ lldb/test/Shell/SymbolFile/DWARF/DW_OP_piece-smaller-than-struct.s
@@ -0,0 +1,110 @@
+# RUN: llvm-mc -filetype=obj -o %t -triple x86_64-pc-linux %s
+# RUN: %lldb %t -o "target variable reset" -b | FileCheck %s
+
+# CHECK: (lldb) target variable reset
+# CHECK: (auto_reset) reset = {
+# CHECK: ptr = 0x{{0+$}}
+# Note: We need to find some way to represent "prev" as unknown/undefined.
+# CHECK: prev = false
+# CHECK: }
+
+ .section .debug_abbrev,"",@progbits
+ .byte 1 # Abbreviation Code
+ .byte 17 # DW_TAG_compile_unit
+ .byte 1 # DW_CHILDREN_yes
+ .byte 0 # EOM(1)
+ .byte 0 # EOM(2)
+ .byte 2 # Abbreviation Code
+ .byte 52 # DW_TAG_variable
+ .byte 0 # DW_CHILDREN_no
+ .byte 3 # DW_AT_name
+ .byte 8 # DW_FORM_string
+ .byte 73 # DW_AT_type
+ .byte 19 # DW_FORM_ref4
+ .byte 2 # DW_AT_location
+ .byte 24 # DW_FORM_exprloc
+ .byte 0 # EOM(1)
+ .byte 0 # EOM(2)
+ .byte 3 # Abbreviation Code
+ .byte 36 # DW_TAG_base_type
+ .byte 0 # DW_CHILDREN_no
+ .byte 3 # DW_AT_name
+ .byte 8 # DW_FORM_string
+ .byte 62 # DW_AT_encoding
+ .byte 11 # DW_FORM_data1
+ .byte 11 # DW_AT_byte_size
+ .byte 11 # DW_FORM_data1
+ .byte 0 # EOM(1)
+ .byte 0 # EOM(2)
+ .byte 4 # Abbreviation Code
+ .byte 19 # DW_TAG_structure_type
+ .byte 1 # DW_CHILDREN_yes
+ .byte 3 # DW_AT_name
+ .byte 8 # DW_FORM_string
+ .byte 11 # DW_AT_byte_size
+ .byte 11 # DW_FORM_data1
+ .byte 0 # EOM(1)
+ .byte 0 # EOM(2)
+ .byte 5 # Abbreviation Code
+ .byte 13 # DW_TAG_member
+ .byte 0 # DW_CHILDREN_no
+ .byte 3 # DW_AT_name
+ .byte 8 # DW_FORM_string
+ .byte 73 # DW_AT_type
+ .byte 19 # DW_FORM_ref4
+ .byte 56 # DW_AT_data_member_location
+ .byte 11 # DW_FORM_data1
+ .byte 0 # EOM(1)
+ .byte 0 # EOM(2)
+ .byte 6 # Abbreviation Code
+ .byte 15 # DW_TAG_pointer_type
+ .byte 0 # DW_CHILDREN_no
+ .byte 73 # DW_AT_type
+ .byte 19 # DW_FORM_ref4
+ .byte 0 # EOM(1)
+ .byte 0 # EOM(2)
+ .byte 0 # EOM(3)
+
+ .section .debug_info,"",@progbits
+.Lcu_begin0:
+ .long .Lcu_end-.Lcu_start # Length of Unit
+.Lcu_start:
+ .short 4 # DWARF version number
+ .long .debug_abbrev # Offset Into Abbrev. Section
+ .byte 8 # Address Size (in bytes)
+ .byte 1 # Abbrev [1] 0xb:0x6c DW_TAG_compile_unit
+.Lbool:
+ .byte 3 # Abbrev [3] 0x33:0x7 DW_TAG_base_type
+ .asciz "bool" # DW_AT_name
+ .byte 2 # DW_AT_encoding
+ .byte 1 # DW_AT_byte_size
+ .byte 2 # Abbrev [2] 0x3a:0x15 DW_TAG_variable
+ .asciz "reset" # DW_AT_name
+ .long .Lstruct # DW_AT_type
+ .byte 2f-1f # DW_AT_location
+1:
+ .byte 0xe # DW_OP_constu
+ .quad 0xdeadbeefbaadf00d
+ .byte 0x9f # DW_OP_stack_value
+ .byte 0x93 # DW_OP_piece
+ .uleb128 8
+ # Note: Only the first 8 bytes of the struct are described.
+2:
+.Lstruct:
+ .byte 4 # Abbrev [4] 0x4f:0x22 DW_TAG_structure_type
+ .asciz "auto_reset" # DW_AT_name
+ .byte 16 # DW_AT_byte_size
+ .byte 5 # Abbrev [5] 0x58:0xc DW_TAG_member
+ .asciz "ptr" # DW_AT_name
+ .long .Lbool_ptr # DW_AT_type
+ .byte 0 # DW_AT_data_member_location
+ .byte 5 # Abbrev [5] 0x64:0xc DW_TAG_member
+ .asciz "prev" # DW_AT_name
+ .long .Lbool # DW_AT_type
+ .byte 8 # DW_AT_data_member_location
+ .byte 0 # End Of Children Mark
+.Lbool_ptr:
+ .byte 6 # Abbrev [6] 0x71:0x5 DW_TAG_pointer_type
+ .long .Lbool # DW_AT_type
+ .byte 0 # End Of Children Mark
+.Lcu_end:
Index: lldb/source/Core/Value.cpp
===================================================================
--- lldb/source/Core/Value.cpp
+++ lldb/source/Core/Value.cpp
@@ -533,13 +533,24 @@
uint8_t *dst = const_cast<uint8_t *>(data.PeekData(0, byte_size));
if (dst != nullptr) {
if (address_type == eAddressTypeHost) {
+ // Don't read more of the Value than what the host has been able to
+ // actually evaluate. The buffer size may be less than the size prescribed
+ // by the type. E.g. this can happen when an expression containing
+ // DW_OP_piece doesn't describe the whole object.
+ byte_size = GetBuffer().GetByteSize();
+
// The address is an address in this process, so just copy it.
if (address == 0) {
error.SetErrorStringWithFormat(
"trying to read from host address of 0.");
return error;
}
- memcpy(dst, reinterpret_cast<uint8_t *>(address), byte_size);
+
+ // Only copy if we have something to copy: otherwise, we still want to
+ // return a buffer of the appropriate size. Note that we ought to find a
+ // way to represent undefined bits and use that instead of printing 0's.
+ if (byte_size)
+ memcpy(dst, reinterpret_cast<uint8_t *>(address), byte_size);
} else if ((address_type == eAddressTypeLoad) ||
(address_type == eAddressTypeFile)) {
if (file_so_addr.IsValid()) {
Index: lldb/packages/Python/lldbsuite/test/functionalities/optimized_code/main.cpp
===================================================================
--- /dev/null
+++ lldb/packages/Python/lldbsuite/test/functionalities/optimized_code/main.cpp
@@ -0,0 +1,31 @@
+// This is a regression test that checks whether lldb can inspect the variables
+// in this program without triggering an ASan exception.
+
+__attribute__((noinline, optnone)) int use(int x) { return x; }
+
+volatile int sink;
+
+struct S1 {
+ int f1;
+ int *f2;
+};
+
+struct S2 {
+ char a, b;
+ int pad;
+ S2(int x) {
+ a = x & 0xff;
+ b = x & 0xff00;
+ }
+};
+
+int main() {
+ S1 v1;
+ v1.f1 = sink;
+ v1.f2 = nullptr;
+ sink++; //% self.expect("frame variable v1", substrs=["S1"])
+ S2 v2(v1.f1);
+ sink += use(v2.a); //% self.expect("frame variable v2", substrs=["S2"])
+ sink += use(v2.pad); //% self.expect("frame variable v2", substrs=["S2"])
+ return 0;
+}
Index: lldb/packages/Python/lldbsuite/test/functionalities/optimized_code/TestNoASanExceptionAfterEvalOP_piece.py
===================================================================
--- /dev/null
+++ lldb/packages/Python/lldbsuite/test/functionalities/optimized_code/TestNoASanExceptionAfterEvalOP_piece.py
@@ -0,0 +1,4 @@
+from lldbsuite.test import lldbinline
+from lldbsuite.test import decorators
+
+lldbinline.MakeInlineTest(__file__, globals())
Index: lldb/packages/Python/lldbsuite/test/functionalities/optimized_code/Makefile
===================================================================
--- /dev/null
+++ lldb/packages/Python/lldbsuite/test/functionalities/optimized_code/Makefile
@@ -0,0 +1,3 @@
+CXX_SOURCES := main.cpp
+CXXFLAGS_EXTRAS := -O2
+include Makefile.rules
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