zturner created this revision.
zturner added reviewers: labath, clayborg, aprantl, probinson.
Herald added a subscriber: jdoerfert.
The goal here is to improve our error handling and error recovery while parsing
DWARF, while at the same time getting us closer to being able to merge LLDB's
DWARF parser with LLVM's. To this end, I've udpated several of the low-level
parsing functions in LLDB to return `llvm::Error` and `llvm::Expected`.
For now, this only updates LLDB parsing functions and not LLVM. In some ways,
this actually gets us *farther* from parity with the two interfaces, because
prior to this patch, at least the parsing interfaces were the same (i.e. they
all just returned bools, and now with this patch they're diverging). But, I
chose to do this for two primary reasons.
1. LLDB has error logging code engrained deep within some of its parsing
functions. We don't want to lose this logging information, but obviously LLVM
has no logging mechanism at all. So if we're to merge the interfaces, we have
to find a way to still allow LLDB to properly report parsing errors while not
having the reporting code be inside of LLVM.
2. LLDB (and indeed, LLVM) overload the meaning of the `false` return value
from all of these extraction functions to mean both "We reached the null entry
at the end of a list of items, therefore everything was successful" as well as
"something bad and unrecoverable happened during parsing". So you would have a
lot code that would do something like:
while (foo.extract(...)) {
...
}
But when the loop stops, why did it stop? Did it stop because it finished
parsing, or because there was an error? Because of this, in some cases we
don't always know whether it is ok to proceed, or how to proceed, but we were
doing it anyway.
In this patch, I solve the second problem by introducing an enumeration called
`DWARFEnumState` which has two values `MoreItems and `Complete`. Both of these
indicate success, but the latter indicates that we reached the null entry.
Then, I return this value instead of bool, and convey parsing failure
separately.
To solve the first problem (and convey parsing failure) these functions now
return either `llvm::Error` or `llvm::Expected<DWARFEnumState>`. Having this
extra bit of information allows us to properly convey all 3 of us "error, bail
out", "success, call this function again", and "success, don't call this
function again".
In subsequent patches I plan to extend this pattern to the rest of the parsing
interfaces, which will ultimately get all of the log statements and error
reporting out of the low level parsing code and into the high level parsing
code (e.g. `SymbolFileDWARF`, `DWARFASTParserClang`, etc).
Eventually, these same changes will have to be backported to LLVM's DWARF
parser, but I feel like diverging in the short term is the quickest way to
converge in the long term.
https://reviews.llvm.org/D59370
Files:
lldb/source/Plugins/SymbolFile/DWARF/DWARFAbbreviationDeclaration.cpp
lldb/source/Plugins/SymbolFile/DWARF/DWARFAbbreviationDeclaration.h
lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugAbbrev.cpp
lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugAbbrev.h
lldb/source/Plugins/SymbolFile/DWARF/DWARFDefines.h
lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
Index: lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
===================================================================
--- lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
+++ lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
@@ -660,14 +660,23 @@
}
DWARFDebugAbbrev *SymbolFileDWARF::DebugAbbrev() {
- if (m_abbr == NULL) {
- const DWARFDataExtractor &debug_abbrev_data = get_debug_abbrev_data();
- if (debug_abbrev_data.GetByteSize() > 0) {
- m_abbr.reset(new DWARFDebugAbbrev());
- if (m_abbr)
- m_abbr->Parse(debug_abbrev_data);
- }
+ if (m_abbr)
+ return m_abbr.get();
+
+ const DWARFDataExtractor &debug_abbrev_data = get_debug_abbrev_data();
+ if (debug_abbrev_data.GetByteSize() == 0)
+ return nullptr;
+
+ auto abbr = llvm::make_unique<DWARFDebugAbbrev>();
+ llvm::Error error = abbr->parse(debug_abbrev_data);
+ if (error) {
+ Log *log = LogChannelDWARF::GetLogIfAll(DWARF_LOG_DEBUG_INFO);
+ LLDB_LOG_ERROR(log, std::move(error),
+ "Unable to read .debug_abbrev section: {0}");
+ return nullptr;
}
+
+ m_abbr = std::move(abbr);
return m_abbr.get();
}
Index: lldb/source/Plugins/SymbolFile/DWARF/DWARFDefines.h
===================================================================
--- lldb/source/Plugins/SymbolFile/DWARF/DWARFDefines.h
+++ lldb/source/Plugins/SymbolFile/DWARF/DWARFDefines.h
@@ -14,6 +14,8 @@
namespace lldb_private {
+enum class DWARFEnumState { MoreItems, Complete };
+
typedef uint32_t DRC_class; // Holds DRC_* class bitfields
enum DW_TAG_Category {
Index: lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugAbbrev.h
===================================================================
--- lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugAbbrev.h
+++ lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugAbbrev.h
@@ -35,8 +35,8 @@
void Clear();
dw_offset_t GetOffset() const { return m_offset; }
void Dump(lldb_private::Stream *s) const;
- bool Extract(const lldb_private::DWARFDataExtractor &data,
- lldb::offset_t *offset_ptr);
+ llvm::Error extract(const lldb_private::DWARFDataExtractor &data,
+ lldb::offset_t *offset_ptr);
// void Encode(BinaryStreamBuf& debug_abbrev_buf) const;
dw_uleb128_t
AppendAbbrevDeclSequential(const DWARFAbbreviationDeclaration &abbrevDecl);
@@ -64,7 +64,7 @@
const DWARFAbbreviationDeclarationSet *
GetAbbreviationDeclarationSet(dw_offset_t cu_abbr_offset) const;
void Dump(lldb_private::Stream *s) const;
- void Parse(const lldb_private::DWARFDataExtractor &data);
+ llvm::Error parse(const lldb_private::DWARFDataExtractor &data);
void GetUnsupportedForms(std::set<dw_form_t> &invalid_forms) const;
protected:
Index: lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugAbbrev.cpp
===================================================================
--- lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugAbbrev.cpp
+++ lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugAbbrev.cpp
@@ -25,14 +25,22 @@
//----------------------------------------------------------------------
// DWARFAbbreviationDeclarationSet::Extract()
//----------------------------------------------------------------------
-bool DWARFAbbreviationDeclarationSet::Extract(const DWARFDataExtractor &data,
- lldb::offset_t *offset_ptr) {
+llvm::Error
+DWARFAbbreviationDeclarationSet::extract(const DWARFDataExtractor &data,
+ lldb::offset_t *offset_ptr) {
const lldb::offset_t begin_offset = *offset_ptr;
m_offset = begin_offset;
Clear();
DWARFAbbreviationDeclaration abbrevDeclaration;
dw_uleb128_t prev_abbr_code = 0;
- while (abbrevDeclaration.Extract(data, offset_ptr)) {
+ DWARFEnumState state = DWARFEnumState::MoreItems;
+ while (state == DWARFEnumState::MoreItems) {
+ llvm::Expected<DWARFEnumState> es =
+ abbrevDeclaration.extract(data, offset_ptr);
+ if (!es)
+ return es.takeError();
+
+ state = *es;
m_decls.push_back(abbrevDeclaration);
if (m_idx_offset == 0)
m_idx_offset = abbrevDeclaration.Code();
@@ -43,7 +51,7 @@
}
prev_abbr_code = abbrevDeclaration.Code();
}
- return begin_offset != *offset_ptr;
+ return llvm::ErrorSuccess();
}
//----------------------------------------------------------------------
@@ -138,19 +146,21 @@
//----------------------------------------------------------------------
// DWARFDebugAbbrev::Parse()
//----------------------------------------------------------------------
-void DWARFDebugAbbrev::Parse(const DWARFDataExtractor &data) {
+llvm::Error DWARFDebugAbbrev::parse(const DWARFDataExtractor &data) {
lldb::offset_t offset = 0;
while (data.ValidOffset(offset)) {
uint32_t initial_cu_offset = offset;
DWARFAbbreviationDeclarationSet abbrevDeclSet;
- if (abbrevDeclSet.Extract(data, &offset))
- m_abbrevCollMap[initial_cu_offset] = abbrevDeclSet;
- else
- break;
+ llvm::Error error = abbrevDeclSet.extract(data, &offset);
+ if (error)
+ return error;
+
+ m_abbrevCollMap[initial_cu_offset] = abbrevDeclSet;
}
m_prev_abbr_offset_pos = m_abbrevCollMap.end();
+ return llvm::ErrorSuccess();
}
//----------------------------------------------------------------------
Index: lldb/source/Plugins/SymbolFile/DWARF/DWARFAbbreviationDeclaration.h
===================================================================
--- lldb/source/Plugins/SymbolFile/DWARF/DWARFAbbreviationDeclaration.h
+++ lldb/source/Plugins/SymbolFile/DWARF/DWARFAbbreviationDeclaration.h
@@ -10,7 +10,9 @@
#define liblldb_DWARFAbbreviationDeclaration_h_
#include "DWARFAttribute.h"
+#include "DWARFDefines.h"
#include "SymbolFileDWARF.h"
+#include "llvm/Support/Error.h"
class DWARFAbbreviationDeclaration {
public:
@@ -44,10 +46,11 @@
return m_attributes[idx].get_form();
}
uint32_t FindAttributeIndex(dw_attr_t attr) const;
- bool Extract(const lldb_private::DWARFDataExtractor &data,
- lldb::offset_t *offset_ptr);
- bool Extract(const lldb_private::DWARFDataExtractor &data,
- lldb::offset_t *offset_ptr, dw_uleb128_t code);
+
+ /// Extract one a
+ llvm::Expected<lldb_private::DWARFEnumState>
+ extract(const lldb_private::DWARFDataExtractor &data,
+ lldb::offset_t *offset_ptr);
bool IsValid();
void Dump(lldb_private::Stream *s) const;
bool operator==(const DWARFAbbreviationDeclaration &rhs) const;
Index: lldb/source/Plugins/SymbolFile/DWARF/DWARFAbbreviationDeclaration.cpp
===================================================================
--- lldb/source/Plugins/SymbolFile/DWARF/DWARFAbbreviationDeclaration.cpp
+++ lldb/source/Plugins/SymbolFile/DWARF/DWARFAbbreviationDeclaration.cpp
@@ -11,6 +11,8 @@
#include "lldb/Core/dwarf.h"
#include "lldb/Utility/Stream.h"
+#include "llvm/Object/Error.h"
+
#include "DWARFFormValue.h"
using namespace lldb_private;
@@ -23,41 +25,48 @@
: m_code(InvalidCode), m_tag(tag), m_has_children(has_children),
m_attributes() {}
-bool DWARFAbbreviationDeclaration::Extract(const DWARFDataExtractor &data,
- lldb::offset_t *offset_ptr) {
- return Extract(data, offset_ptr, data.GetULEB128(offset_ptr));
-}
+llvm::Expected<DWARFEnumState>
+DWARFAbbreviationDeclaration::extract(const DWARFDataExtractor &data,
+ lldb::offset_t *offset_ptr) {
+ m_code = data.GetULEB128(offset_ptr);
+ if (m_code == 0)
+ return DWARFEnumState::Complete;
-bool DWARFAbbreviationDeclaration::Extract(const DWARFDataExtractor &data,
- lldb::offset_t *offset_ptr,
- dw_uleb128_t code) {
- m_code = code;
m_attributes.clear();
- if (m_code) {
- m_tag = data.GetULEB128(offset_ptr);
- m_has_children = data.GetU8(offset_ptr);
-
- while (data.ValidOffset(*offset_ptr)) {
- dw_attr_t attr = data.GetULEB128(offset_ptr);
- dw_form_t form = data.GetULEB128(offset_ptr);
- DWARFFormValue::ValueType val;
-
- if (form == DW_FORM_implicit_const)
- val.value.sval = data.GetULEB128(offset_ptr);
-
- if (attr && form)
- m_attributes.push_back(DWARFAttribute(attr, form, val));
- else
- break;
- }
-
- return m_tag != 0;
- } else {
- m_tag = 0;
- m_has_children = 0;
+ m_tag = data.GetULEB128(offset_ptr);
+ if (m_tag == DW_TAG_null) {
+ // FIXME: According to the DWARF spec this may actually be malformed.
+ // Should this return an error instead?
+ return DWARFEnumState::Complete;
+ }
+
+ m_has_children = data.GetU8(offset_ptr);
+
+ while (data.ValidOffset(*offset_ptr)) {
+ dw_attr_t attr = data.GetULEB128(offset_ptr);
+ dw_form_t form = data.GetULEB128(offset_ptr);
+
+ // This is the last attribute for this abbrev decl, but there may still be
+ // more abbrev decls, so return MoreItems to indicate to the caller that
+ // they should call this function again.
+ if (!attr && !form)
+ return DWARFEnumState::MoreItems;
+
+ if (!attr || !form)
+ return llvm::make_error<llvm::object::GenericBinaryError>(
+ "malformed abbreviation declaration attribute");
+
+ DWARFFormValue::ValueType val;
+
+ if (form == DW_FORM_implicit_const)
+ val.value.sval = data.GetULEB128(offset_ptr);
+
+ m_attributes.push_back(DWARFAttribute(attr, form, val));
}
- return false;
+ return llvm::make_error<llvm::object::GenericBinaryError>(
+ "abbreviation declaration attribute list not terminated with a null "
+ "entry");
}
void DWARFAbbreviationDeclaration::Dump(Stream *s) const {
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