Beginnings of pinpoint plugin
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343
playground/spslr_pinpoint.cpp
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343
playground/spslr_pinpoint.cpp
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#include <iostream>
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#include <string>
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#include <unordered_map>
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#include <unordered_set>
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#include <map>
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#include <list>
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#include <gcc-plugin.h>
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#include <plugin-version.h>
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#include <tree.h>
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#include <langhooks.h>
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int plugin_is_GPL_compatible;
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#define SPSLR_OFFSETOF "__spslr_offsetof"
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// Recognize __attribute__((spslr)) on structures and track their layout
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struct Member {
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using OFF = unsigned long;
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using SIZE = unsigned long;
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static constexpr int FLAG_DANGERZONE = 1;
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OFF offset = 0;
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SIZE size = 0;
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int flags = 0;
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};
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struct Target {
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using UID = unsigned long;
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UID uid;
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std::map<Member::OFF, Member> members;
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void log_member(const Member& member);
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const Member* get_member(Member::OFF offset) const;
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};
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struct TargetTree {
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tree t;
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Target::UID uid;
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};
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static Target::UID next_target_uid = 0;
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static std::unordered_map<Target::UID, Target> targets;
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static std::list<TargetTree> target_trees;
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static std::unordered_set<tree> target_markings;
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static bool find_target_log(tree t, Target::UID& uid) {
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for (const TargetTree& tt : target_trees) {
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if (lang_hooks.types_compatible_p(tt.t, t)) {
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uid = tt.uid;
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return true;
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}
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}
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return false;
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}
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void Target::log_member(const Member& member) {
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Member tmp_member;
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tmp_member.offset = member.offset;
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tmp_member.size = (member.size == 0 ? 1 : member.size);
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tmp_member.flags = (member.size == 0 ? Member::FLAG_DANGERZONE : 0) | member.flags;
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// Overlaps are dangerous -> remove and integrate into member
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auto overlap_end = members.lower_bound(tmp_member.offset + tmp_member.size);
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for (auto it = std::make_reverse_iterator(overlap_end); it != members.rend();) {
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const Member& existing_member = it->second;
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if (existing_member.offset + existing_member.size <= tmp_member.offset)
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break;
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Member::OFF combined_end = std::max<Member::OFF>(tmp_member.offset + tmp_member.size,
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existing_member.offset + existing_member.size);
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Member::OFF combined_offset = std::min<Member::OFF>(tmp_member.offset, existing_member.offset);
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Member::SIZE combined_size = combined_end - combined_offset;
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tmp_member.flags |= (existing_member.flags | Member::FLAG_DANGERZONE);
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tmp_member.offset = combined_offset;
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tmp_member.size = combined_size;
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// Erase overlapping member
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auto tmp_forward = std::prev(it.base());
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tmp_forward = members.erase(tmp_forward);
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it = std::make_reverse_iterator(tmp_forward);
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}
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members.emplace(tmp_member.offset, tmp_member);
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}
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const Member* Target::get_member(Member::OFF offset) const {
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auto it = members.find(offset);
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if (it == members.end())
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return nullptr;
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return &it->second;
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}
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static void log_target(tree node) {
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if (TREE_CODE(node) != RECORD_TYPE)
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return;
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auto marking = target_markings.find(node);
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if (marking == target_markings.end())
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return;
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Target::UID existing_target;
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if (find_target_log(node, existing_target))
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return;
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Target::UID tuid = next_target_uid++;
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TargetTree new_tt;
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new_tt.t = node;
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new_tt.uid = tuid;
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target_trees.push_back(new_tt);
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targets.emplace(tuid, Target{});
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Target& target = targets.at(tuid);
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target.uid = tuid;
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// Log all members
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for (tree field = TYPE_FIELDS(node); field; field = DECL_CHAIN(field)) {
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if (TREE_CODE(field) != FIELD_DECL)
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continue;
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HOST_WIDE_INT field_byte_offset = 0;
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if (TREE_CODE(DECL_FIELD_OFFSET(field)) == INTEGER_CST)
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field_byte_offset = tree_to_uhwi(DECL_FIELD_OFFSET(field));
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HOST_WIDE_INT field_bit_offset = 0;
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if (TREE_CODE(DECL_FIELD_BIT_OFFSET(field)) == INTEGER_CST)
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field_bit_offset = tree_to_uhwi(DECL_FIELD_BIT_OFFSET(field));
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HOST_WIDE_INT field_bit_offset_bytes = field_bit_offset / 8;
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field_byte_offset += field_bit_offset_bytes;
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field_bit_offset -= field_bit_offset_bytes * 8;
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HOST_WIDE_INT field_bit_size = 0;
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if (TREE_CODE(DECL_SIZE(field)) == INTEGER_CST)
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field_bit_size = tree_to_uhwi(DECL_SIZE(field));
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bool is_bitfield = (DECL_BIT_FIELD_TYPE(field) != NULL_TREE);
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bool is_multibyte = (field_bit_size % 8 == 0 && field_bit_offset == 0);
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bool is_dangerous = (is_bitfield || !is_multibyte);
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HOST_WIDE_INT field_offset_bit_size = field_bit_offset + field_bit_size;
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HOST_WIDE_INT effective_field_size = field_offset_bit_size / 8;
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if (field_offset_bit_size % 8 != 0)
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effective_field_size += 1;
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Member member;
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member.offset = (Member::OFF)field_byte_offset;
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member.size = (Member::SIZE)effective_field_size;
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member.flags = (is_dangerous ? Member::FLAG_DANGERZONE : 0);
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target.log_member(member);
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}
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}
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static tree log_target_attribute(tree* node, tree name, tree args, int flags, bool* no_add_attrs) {
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if (!node)
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return NULL_TREE;
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if (TREE_CODE(*node) != RECORD_TYPE)
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return NULL_TREE;
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tree type_main_variant = TYPE_MAIN_VARIANT(*node);
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if (!type_main_variant)
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return NULL_TREE;
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target_markings.insert(type_main_variant);
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return NULL_TREE;
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}
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static struct attribute_spec spslr_attribute = {
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"spslr", 0, 0, false, false, false, false, log_target_attribute, NULL
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};
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void on_register_attributes(void* event_data, void* data) {
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register_attribute(&spslr_attribute);
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}
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static void on_type_complete(void* event_data, void* user_data) {
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tree type = (tree)event_data;
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log_target(TYPE_MAIN_VARIANT(type));
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}
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// Early hook to make COMPONENT_REF nodes survice front end
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struct SPSLROffsetofCallData {
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using UID = unsigned long;
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UID uid;
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Target::UID target;
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Member::OFF member;
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};
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static tree spslr_offsetof_decl = NULL_TREE;
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static SPSLROffsetofCallData::UID spslr_offsetof_next_uid = 0;
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static std::unordered_map<SPSLROffsetofCallData::UID, SPSLROffsetofCallData> spslr_offsetof_calls;
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static bool require_spslr_offsetof_decl() {
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if (spslr_offsetof_decl)
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return true;
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tree param_types = tree_cons(NULL_TREE, long_unsigned_type_node, NULL_TREE);
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tree fntype = build_function_type(sizetype, param_types);
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spslr_offsetof_decl = build_fn_decl(SPSLR_OFFSETOF, fntype);
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if (!spslr_offsetof_decl)
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return false;
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DECL_EXTERNAL (spslr_offsetof_decl) = 1;
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TREE_PUBLIC (spslr_offsetof_decl) = 1;
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DECL_ARTIFICIAL (spslr_offsetof_decl) = 1;
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// Prevent VOP problems later when removing calls
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// Explanation -> VOPs mark memory side-effects, which these calls have none of anyways
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DECL_PURE_P(spslr_offsetof_decl) = 1;
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DECL_IS_NOVOPS(spslr_offsetof_decl) = 1;
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return true;
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}
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static bool is_relevant_offsetof(tree ref, Target::UID& tuid, Member::OFF& moff) {
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if (!ref || TREE_CODE(ref) != COMPONENT_REF)
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return false;
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tree base = TREE_OPERAND(ref, 0);
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if (!base)
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return false;
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tree base_type = TREE_TYPE(base);
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if (!base_type)
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return false;
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if (!find_target_log(base_type, tuid))
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return false;
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auto target_it = targets.find(tuid);
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if (target_it == targets.end())
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return false;
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const Target& t = target_it->second;
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tree field = TREE_OPERAND(ref, 1);
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HOST_WIDE_INT field_byte_offset = 0;
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if (TREE_CODE(DECL_FIELD_OFFSET(field)) == INTEGER_CST)
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field_byte_offset = tree_to_uhwi(DECL_FIELD_OFFSET(field));
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HOST_WIDE_INT field_bit_offset = 0;
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if (TREE_CODE(DECL_FIELD_BIT_OFFSET(field)) == INTEGER_CST)
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field_bit_offset = tree_to_uhwi(DECL_FIELD_BIT_OFFSET(field));
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Member::OFF effective_field_offset = (field_byte_offset + (field_bit_offset / 8));
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moff = effective_field_offset;
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const Member* m = t.get_member(effective_field_offset);
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if (!m)
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return false;
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return !(m->flags & Member::FLAG_DANGERZONE);
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}
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static tree instrument_offsetof_maybe(tree ref) {
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SPSLROffsetofCallData call_data;
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if (!is_relevant_offsetof(ref, call_data.target, call_data.member))
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return NULL_TREE;
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location_t loc = EXPR_LOCATION(ref);
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tree result_type = TREE_TYPE(ref);
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if (!require_spslr_offsetof_decl()) {
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std::cerr << "spslr_pinpoint -> failed to instrument COMPONENT_REF (" << SPSLR_OFFSETOF << " unavailable)" << std::endl;
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return NULL_TREE;
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}
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call_data.uid = spslr_offsetof_next_uid++;
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spslr_offsetof_calls.emplace(call_data.uid, call_data);
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tree call_uid_tree = build_int_cst(long_unsigned_type_node, call_data.uid);
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tree call_tree = build_call_expr_loc(loc, spslr_offsetof_decl, 1, call_uid_tree);
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// Get base as char*
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tree base = TREE_OPERAND(ref, 0);
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tree base_addr;
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if (TREE_CODE(base) == ADDR_EXPR) {
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// base_addr = base;
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std::cerr << "spslr_pinpoint -> unexpected ADDR_EXPR as COMPONENT_REF base!" << std::endl;
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return NULL_TREE;
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} else {
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base_addr = build_fold_addr_expr(base);
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}
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tree char_ptr_type = build_pointer_type(char_type_node);
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tree base_char_ptr = fold_convert(char_ptr_type, base_addr);
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// Add __spslr_offsetof, cast back to field pointer, then dereference
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tree plus = build2_loc(loc, POINTER_PLUS_EXPR, char_ptr_type, base_char_ptr, call_tree);
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tree field_ptr_type = build_pointer_type(result_type);
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tree cast_back = build1_loc(loc, NOP_EXPR, field_ptr_type, plus);
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tree new_ref = build1_loc(loc, INDIRECT_REF, result_type, cast_back);
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return new_ref;
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}
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static void on_build_component_ref(void* event_data, void* user_data) {
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tree* component_ref_node = (tree*)event_data;
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if (!component_ref_node)
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return;
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tree repl = instrument_offsetof_maybe(*component_ref_node);
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if (repl)
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*component_ref_node = repl;
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}
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// Hook everything up in plugin_init
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int plugin_init (struct plugin_name_args *plugin_info, struct plugin_gcc_version *version) {
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if (!plugin_default_version_check(version, &gcc_version)) {
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fprintf(stderr, "GCC version mismatch!\n");
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std::cerr << "spslr_pinpoint -> GCC version mismatch" << std::endl;
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return 1;
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}
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register_callback(plugin_info->base_name, PLUGIN_ATTRIBUTES, on_register_attributes, NULL);
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register_callback(plugin_info->base_name, PLUGIN_FINISH_TYPE, on_type_complete, NULL);
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register_callback(plugin_info->base_name, PLUGIN_BUILD_COMPONENT_REF, on_build_component_ref, NULL);
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return 0;
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}
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