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dump_syms: handle forward reference DWARF attributes

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DW_AT_specification and DW_AT_abstract_origin attributes carry
references to other DIEs. Nothing prevents the DIEs referred to from
appearing later in .debug_info than the DIE containing the referring
attribute, but dump_syms incompletly implemented its handling of these
references, and was only able to resolve them when they were
back-references.

This will fix the chronic warnings produced by dump_syms of the form:

dump_syms: the DIE at offset <offset> has a {DW_AT_specification,
DW_AT_abstract_origin} attribute referring to the die at offset
<offset>, which either was not marked as {a declaration, an inline}, or
comes later in the file

Patch by Greg Clayton

Bug: breakpad:441
Change-Id: I98957d64a234c22afb6d0153f1bdc09e6a600b1d
Reviewed-on: https://chromium-review.googlesource.com/c/breakpad/breakpad/+/1946706
Reviewed-by: Mark Mentovai <mark@chromium.org>
This commit is contained in:
Mark Mentovai 2019-12-02 13:45:36 -05:00
parent 1f1d950d6a
commit 47cd498384
2 changed files with 35 additions and 13 deletions
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38
src/common/dwarf_cu_to_module.cc
View file

@ -211,6 +211,10 @@ struct DwarfCUToModule::CUContext {
//
// Destroying this destroys all the functions this vector points to.
vector<Module::Function *> functions;
// Keep a list of forward references from DW_AT_abstract_origin and
// DW_AT_specification attributes so names can be fixed up.
std::map<uint64_t, Module::Function *> forward_ref_die_to_func;
};
// Information about the context of a particular DIE. This is for
@ -242,7 +246,8 @@ class DwarfCUToModule::GenericDIEHandler: public dwarf2reader::DIEHandler {
parent_context_(parent_context),
offset_(offset),
declaration_(false),
specification_(NULL) { }
specification_(NULL),
forward_ref_die_offset_(0) { }
// Derived classes' ProcessAttributeUnsigned can defer to this to
// handle DW_AT_declaration, or simply not override it.
@ -294,6 +299,11 @@ class DwarfCUToModule::GenericDIEHandler: public dwarf2reader::DIEHandler {
// Otherwise, this is NULL.
Specification *specification_;
// If this DIE has a DW_AT_specification or DW_AT_abstract_origin and it is a
// forward reference, no Specification will be available. Track the reference
// to be fixed up when the DIE is parsed.
uint64_t forward_ref_die_offset_;
// The value of the DW_AT_name attribute, or the empty string if the
// DIE has no such attribute.
string name_attribute_;
@ -341,12 +351,8 @@ void DwarfCUToModule::GenericDIEHandler::ProcessAttributeReference(
if (spec != specifications->end()) {
specification_ = &spec->second;
} else {
// Technically, there's no reason a DW_AT_specification
// couldn't be a forward reference, but supporting that would
// be a lot of work (changing to a two-pass structure), and I
// don't think any producers we care about ever emit such
// things.
cu_context_->reporter->UnknownSpecification(offset_, data);
// The DW_AT_specification is a forward reference.
forward_ref_die_offset_ = data;
}
break;
}
@ -539,7 +545,7 @@ void DwarfCUToModule::FuncHandler::ProcessAttributeReference(
if (origin != origins.end()) {
abstract_origin_ = &(origin->second);
} else {
cu_context_->reporter->UnknownAbstractOrigin(offset_, data);
forward_ref_die_offset_ = data;
}
break;
}
@ -571,6 +577,15 @@ static bool IsEmptyRange(const vector<Module::Range>& ranges) {
void DwarfCUToModule::FuncHandler::Finish() {
vector<Module::Range> ranges;
// Check if this DIE was one of the forward references that was not able
// to be processed, and fix up the name of the appropriate Module::Function.
// "name_" will have already been fixed up in EndAttributes().
if (!name_.empty()) {
auto Iter = cu_context_->forward_ref_die_to_func.find(offset_);
if (Iter != cu_context_->forward_ref_die_to_func.end())
Iter->second->name = name_;
}
if (!ranges_) {
// Make high_pc_ an address, if it isn't already.
if (high_pc_form_ != dwarf2reader::DW_FORM_addr &&
@ -606,6 +621,10 @@ void DwarfCUToModule::FuncHandler::Finish() {
if (!name_.empty()) {
name = name_;
} else {
// If we have a forward reference to a DW_AT_specification or
// DW_AT_abstract_origin, then don't warn, the name will be fixed up
// later
if (forward_ref_die_offset_ == 0)
cu_context_->reporter->UnnamedFunction(offset_);
name = "<name omitted>";
}
@ -619,6 +638,9 @@ void DwarfCUToModule::FuncHandler::Finish() {
// If the function address is zero this is a sign that this function
// description is just empty debug data and should just be discarded.
cu_context_->functions.push_back(func.release());
if (forward_ref_die_offset_ != 0)
cu_context_->forward_ref_die_to_func[forward_ref_die_offset_] =
cu_context_->functions.back();
}
} else if (inline_) {
AbstractOrigin origin(name_);

2
src/common/module.h
View file

@ -106,7 +106,7 @@ class Module {
}
// The function's name.
const string name;
string name;
// The start address and the address ranges covered by the function.
const Address address;