sandboxed-api/sandboxed_api/tools/clang_generator/emitter.cc

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// Copyright 2020 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include "sandboxed_api/tools/clang_generator/emitter.h"
#include "absl/random/random.h"
#include "absl/strings/ascii.h"
#include "absl/strings/escaping.h"
#include "absl/strings/match.h"
#include "absl/strings/str_cat.h"
#include "absl/strings/str_format.h"
#include "absl/strings/str_join.h"
#include "absl/strings/str_replace.h"
#include "absl/strings/strip.h"
#include "clang/AST/DeclCXX.h"
#include "sandboxed_api/tools/clang_generator/diagnostics.h"
#include "sandboxed_api/util/status_macros.h"
namespace sapi {
// Common file prolog with auto-generation notice.
// Note: The includes will be adjusted by Copybara when converting to/from
// internal code. This is intentional.
// Text template arguments:
// 1. Header guard
constexpr absl::string_view kHeaderProlog =
R"(// AUTO-GENERATED by the Sandboxed API generator.
// Edits will be discarded when regenerating this file.
#ifndef %1$s
#define %1$s
#include <cstdint>
#include <type_traits>
#include "absl/base/macros.h"
#include "absl/status/status.h"
#include "sandboxed_api/sandbox.h"
#include "sandboxed_api/vars.h"
#include "sandboxed_api/util/status_macros.h"
#include "sandboxed_api/util/statusor.h"
)";
constexpr absl::string_view kHeaderEpilog =
R"(
#endif // %1$s)";
// Text template arguments:
// 1. Include for embedded sandboxee objects
constexpr absl::string_view kEmbedInclude = R"(#include "%1$s_embed.h"
)";
// Text template arguments:
// 1. Namespace name
constexpr absl::string_view kNamespaceBeginTemplate =
R"(
namespace %1$s {
)";
constexpr absl::string_view kNamespaceEndTemplate =
R"(
} // namespace %1$s
)";
// Text template arguments:
// 1. Class name
// 2. Embedded object identifier
constexpr absl::string_view kEmbedClassTemplate = R"(
// Sandbox with embedded sandboxee and default policy
class %1$s : public ::sapi::Sandbox {
public:
%1$s() : ::sapi::Sandbox(%2$s_embed_create()) {}
};
)";
// Text template arguments:
// 1. Class name
constexpr absl::string_view kClassHeaderTemplate = R"(
// Sandboxed API
class %1$s {
public:
explicit %1$s(::sapi::Sandbox* sandbox) : sandbox_(sandbox) {}
ABSL_DEPRECATED("Call sandbox() instead")
::sapi::Sandbox* GetSandbox() const { return sandbox(); }
::sapi::Sandbox* sandbox() const { return sandbox_; }
)";
constexpr absl::string_view kClassFooterTemplate = R"(
private:
::sapi::Sandbox* sandbox_;
};
)";
std::string GetIncludeGuard(absl::string_view filename) {
if (filename.empty()) {
static auto* bit_gen = new absl::BitGen();
return absl::StrCat(
// Copybara will transform the string. This is intentional.
"SANDBOXED_API_GENERATED_HEADER_",
absl::AsciiStrToUpper(absl::StrCat(
absl::Hex(absl::Uniform<uint64_t>(*bit_gen), absl::kZeroPad16))),
"_");
}
constexpr absl::string_view kUnderscorePrefix = "SAPI_";
std::string guard;
guard.reserve(filename.size() + kUnderscorePrefix.size() + 1);
for (auto c : filename) {
if (absl::ascii_isalpha(c)) {
guard += absl::ascii_toupper(c);
continue;
}
if (guard.empty()) {
guard = kUnderscorePrefix;
}
if (absl::ascii_isdigit(c)) {
guard += c;
} else if (guard.back() != '_') {
guard += '_';
}
}
if (!absl::EndsWith(guard, "_")) {
guard += '_';
}
return guard;
}
// Returns the namespace components of a declaration's qualified name.
std::vector<std::string> GetNamespacePath(const clang::TypeDecl* decl) {
std::vector<std::string> comps;
for (const auto* ctx = decl->getDeclContext(); ctx; ctx = ctx->getParent()) {
if (const auto* nd = llvm::dyn_cast<clang::NamespaceDecl>(ctx)) {
comps.push_back(nd->getNameAsString());
}
}
std::reverse(comps.begin(), comps.end());
return comps;
}
// Serializes the given Clang AST declaration back into compilable source code.
std::string PrintAstDecl(const clang::Decl* decl) {
// TODO(cblichmann): Make types nicer
// - Rewrite typedef to using
// - Rewrite function pointers using std::add_pointer_t<>;
if (const auto* record = llvm::dyn_cast<clang::CXXRecordDecl>(decl)) {
// For C++ classes/structs, only emit a forward declaration.
return absl::StrCat(record->isClass() ? "class " : "struct ",
std::string(record->getName()));
}
std::string pretty;
llvm::raw_string_ostream os(pretty);
decl->print(os);
return os.str();
}
std::string GetParamName(const clang::ParmVarDecl* decl, int index) {
if (std::string name = decl->getName().str(); !name.empty()) {
return absl::StrCat(name, "_"); // Suffix to avoid collisions
}
return absl::StrCat("unnamed", index, "_");
}
std::string PrintFunctionPrototype(const clang::FunctionDecl* decl) {
// TODO(cblichmann): Fix function pointers and anonymous namespace formatting
std::string out =
absl::StrCat(decl->getDeclaredReturnType().getAsString(), " ",
std::string(decl->getQualifiedNameAsString()), "(");
std::string print_separator;
for (int i = 0; i < decl->getNumParams(); ++i) {
const clang::ParmVarDecl* param = decl->getParamDecl(i);
absl::StrAppend(&out, print_separator);
print_separator = ", ";
absl::StrAppend(&out, param->getType().getAsString());
if (std::string name = param->getName().str(); !name.empty()) {
absl::StrAppend(&out, " ", name);
}
}
absl::StrAppend(&out, ")");
return out;
}
sapi::StatusOr<std::string> EmitFunction(const clang::FunctionDecl* decl) {
std::string out;
absl::StrAppend(&out, "\n// ", PrintFunctionPrototype(decl), "\n");
const std::string function_name = decl->getNameAsString();
const clang::QualType return_type = decl->getDeclaredReturnType();
const bool returns_void = return_type->isVoidType();
const clang::ASTContext& context = decl->getASTContext();
// "Status<OptionalReturn> FunctionName("
absl::StrAppend(&out, MapQualTypeReturn(context, return_type), " ",
function_name, "(");
struct ParameterInfo {
clang::QualType qual;
std::string name;
};
std::vector<ParameterInfo> params;
std::string print_separator;
for (int i = 0; i < decl->getNumParams(); ++i) {
const clang::ParmVarDecl* param = decl->getParamDecl(i);
ParameterInfo& param_info = params.emplace_back();
param_info.qual = param->getType();
param_info.name = GetParamName(param, i);
absl::StrAppend(&out, print_separator);
print_separator = ", ";
absl::StrAppend(&out, MapQualTypeParameter(context, param_info.qual), " ",
param_info.name);
}
absl::StrAppend(&out, ") {\n");
absl::StrAppend(&out, MapQualType(context, return_type), " v_ret_;\n");
for (const auto& [qual, name] : params) {
if (!IsPointerOrReference(qual)) {
absl::StrAppend(&out, MapQualType(context, qual), " v_", name, "(", name,
");\n");
}
}
absl::StrAppend(&out, "\nSAPI_RETURN_IF_ERROR(sandbox_->Call(\"", function_name,
"\", &v_ret_");
for (const auto& [qual, name] : params) {
absl::StrAppend(&out, ", ", IsPointerOrReference(qual) ? "" : "&v_", name);
}
absl::StrAppend(&out, "));\nreturn ",
(returns_void ? "absl::OkStatus()" : "v_ret_.GetValue()"),
";\n}\n");
return out;
}
sapi::StatusOr<std::string> EmitHeader(
std::vector<clang::FunctionDecl*> functions, const QualTypeSet& types,
const GeneratorOptions& options) {
std::string out;
const std::string include_guard = GetIncludeGuard(options.out_file);
absl::StrAppendFormat(&out, kHeaderProlog, include_guard);
// When embedding the sandboxee, add embed header include
if (!options.embed_name.empty()) {
// Not using JoinPath() because even on Windows include paths use plain
// slashes.
std::string include_file(absl::StripSuffix(
absl::StrReplaceAll(options.embed_dir, {{"\\", "/"}}), "/"));
if (!include_file.empty()) {
absl::StrAppend(&include_file, "/");
}
absl::StrAppend(&include_file, options.embed_name);
absl::StrAppendFormat(&out, kEmbedInclude, include_file);
}
// If specified, wrap the generated API in a namespace
if (options.has_namespace()) {
absl::StrAppendFormat(&out, kNamespaceBeginTemplate,
options.namespace_name);
}
// Emit type dependencies
// TODO(cblichmann): Coalesce namespaces
std::string out_types = "// Types this API depends on\n";
bool added_types = false;
for (const clang::QualType& qual : types) {
clang::TypeDecl* decl = nullptr;
if (const auto* typedef_type = qual->getAs<clang::TypedefType>()) {
decl = typedef_type->getDecl();
} else if (const auto* enum_type = qual->getAs<clang::EnumType>()) {
decl = enum_type->getDecl();
} else {
decl = qual->getAsRecordDecl();
}
if (!decl) {
continue;
}
const std::vector<std::string> ns_path = GetNamespacePath(decl);
std::string nested_ns_name;
if (!ns_path.empty()) {
if (const auto& ns_root = ns_path.front();
ns_root == "std" || ns_root == "sapi" || ns_root == "__gnu_cxx") {
// Filter out any and all declarations from the C++ standard library,
// from SAPI itself and from other well-known namespaces. This avoids
// re-declaring things like standard integer types, for example.
continue;
}
nested_ns_name = absl::StrCat(ns_path[0].empty() ? "" : " ",
absl::StrJoin(ns_path, "::"));
absl::StrAppend(&out_types, "namespace", nested_ns_name, " {\n");
}
absl::StrAppend(&out_types, PrintAstDecl(decl), ";");
if (!ns_path.empty()) {
absl::StrAppend(&out_types, "\n} // namespace", nested_ns_name);
}
absl::StrAppend(&out_types, "\n");
added_types = true;
}
if (added_types) {
absl::StrAppend(&out, out_types);
}
// Optionally emit a default sandbox that instantiates an embedded sandboxee
if (!options.embed_name.empty()) {
// TODO(cblichmann): Make the "Sandbox" suffix configurable.
absl::StrAppendFormat(
&out, kEmbedClassTemplate, absl::StrCat(options.name, "Sandbox"),
absl::StrReplaceAll(options.embed_name, {{"-", "_"}}));
}
// Emit the actual Sandboxed API
// TODO(cblichmann): Make the "Api" suffix configurable or at least optional.
absl::StrAppendFormat(&out, kClassHeaderTemplate,
absl::StrCat(options.name, "Api"));
std::string out_func;
for (const clang::FunctionDecl* decl : functions) {
SAPI_ASSIGN_OR_RETURN(out_func, EmitFunction(decl));
absl::StrAppend(&out, out_func);
}
absl::StrAppend(&out, kClassFooterTemplate);
// Close out the header: close namespace (if needed) and end include guard
if (options.has_namespace()) {
absl::StrAppendFormat(&out, kNamespaceEndTemplate, options.namespace_name);
}
absl::StrAppendFormat(&out, kHeaderEpilog, include_guard);
return out;
}
} // namespace sapi