Add support for Register extern to PSA/eBPF backend (#3202)

* Add support for Register extern to PSA/eBPF backend Co-authored-by: Mateusz Kossakowski <[email protected]> Co-authored-by: Jan Palimąka <[email protected]>
p4lang · Apr 14, 2022 · 5ab6998 · 5ab6998
1 parent 1794c3b
commit 5ab6998
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Showing 17 changed files with 1,326 additions and 6 deletions.
diff --git a/backends/ebpf/CMakeLists.txt b/backends/ebpf/CMakeLists.txt
@@ -47,7 +47,8 @@ set (P4C_EBPF_SRCS
   psa/externs/ebpfPsaCounter.cpp
   psa/externs/ebpfPsaChecksum.cpp
   psa/externs/ebpfPsaHashAlgorithm.cpp
-  psa/externs/ebpfPsaTableImplementation.cpp)
+  psa/externs/ebpfPsaTableImplementation.cpp
+  psa/externs/ebpfPsaRegister.cpp)
 
 set (P4C_EBPF_HDRS
   codeGen.h
@@ -79,6 +80,7 @@ set (P4C_EBPF_HDRS
   psa/externs/ebpfPsaChecksum.h
   psa/externs/ebpfPsaHashAlgorithm.h
   psa/externs/ebpfPsaTableImplementation.h
+  psa/externs/ebpfPsaRegister.h
 )
 
 add_cpplint_files(${CMAKE_CURRENT_SOURCE_DIR} "${P4C_EBPF_SRCS};${P4C_EBPF_HDRS}")

diff --git a/backends/ebpf/ebpfControl.cpp b/backends/ebpf/ebpfControl.cpp
@@ -564,6 +564,27 @@ void EBPFControl::emitDeclaration(CodeBuilder* builder, const IR::Declaration* d
         bool isPointer = codeGen->isPointerVariable(decl->name.name);
         etype->declareInit(builder, vd->name, isPointer);
         builder->endOfStatement(true);
+
+        if (!isPointer) {
+            if (auto type = etype->to<EBPFTypeName>()) {
+                if (type->canonicalTypeIs<EBPFStructType>()) {
+                    // A struct type might be used as a lookup key.
+                    // When a data structure is aligned and is not packed,
+                    // the compiler might generate offsets between fields.
+                    // The BPF verifier may reject using such structures with
+                    // uninitialized offsets as lookup keys.
+                    // Therefore, this piece of code zero-initialize structures
+                    // that might be used as keys.
+                    builder->emitIndent();
+                    builder->appendFormat("__builtin_memset((void *) &%s, 0, sizeof(",
+                                          vd->name.name);
+                    etype->declare(builder, cstring::empty, false);
+                    builder->append("))");
+                    builder->endOfStatement(true);
+                }
+            }
+        }
+
         BUG_CHECK(vd->initializer == nullptr,
                   "%1%: declarations with initializers not supported", decl);
         return;

diff --git a/backends/ebpf/ebpfTable.cpp b/backends/ebpf/ebpfTable.cpp
@@ -24,8 +24,8 @@ namespace EBPF {
 
 bool ActionTranslationVisitor::preorder(const IR::PathExpression* expression) {
     if (isActionParameter(expression)) {
-        cstring paramStr = getActionParamStr(expression);
-        builder->append(paramStr.c_str());
+        cstring paramInstanceName = getParamInstanceName(expression);
+        builder->append(paramInstanceName.c_str());
         return false;
     }
     visit(expression->path);
@@ -41,7 +41,8 @@ bool ActionTranslationVisitor::isActionParameter(const IR::PathExpression *expre
     return false;
 }
 
-cstring ActionTranslationVisitor::getActionParamStr(const IR::Expression *expression) const {
+cstring ActionTranslationVisitor::getParamInstanceName(
+        const IR::Expression *expression) const {
     cstring actionName = EBPFObject::externalName(action);
     auto paramStr = Util::printf_format("%s->u.%s.%s",
                                         valueName, actionName,

diff --git a/backends/ebpf/ebpfTable.h b/backends/ebpf/ebpfTable.h
@@ -38,7 +38,7 @@ class ActionTranslationVisitor : public virtual CodeGenInspector {
     bool preorder(const IR::PathExpression* expression);
 
     bool preorder(const IR::P4Action* act);
-    virtual cstring getActionParamStr(const IR::Expression *expression) const;
+    virtual cstring getParamInstanceName(const IR::Expression *expression) const;
     bool isActionParameter(const IR::PathExpression *expression) const;
 };  // ActionTranslationVisitor
 

diff --git a/backends/ebpf/ebpfType.h b/backends/ebpf/ebpfType.h
@@ -126,6 +126,9 @@ class EBPFTypeName : public EBPFType, public IHasWidth {
     unsigned widthInBits() override;
     unsigned implementationWidthInBits() override;
     void declareArray(CodeBuilder* builder, cstring id, unsigned size) override;
+
+    template<typename T> bool canonicalTypeIs() const
+    { return dynamic_cast<const T*>(this->canonical) != nullptr; }
 };
 
 // Also represents headers and unions

diff --git a/backends/ebpf/psa/ebpfPsaControl.cpp b/backends/ebpf/psa/ebpfPsaControl.cpp
@@ -23,6 +23,28 @@ ControlBodyTranslatorPSA::ControlBodyTranslatorPSA(const EBPFControlPSA* control
         CodeGenInspector(control->program->refMap, control->program->typeMap),
         ControlBodyTranslator(control) {}
 
+bool ControlBodyTranslatorPSA::preorder(const IR::AssignmentStatement* a) {
+    if (auto methodCallExpr = a->right->to<IR::MethodCallExpression>()) {
+        auto mi = P4::MethodInstance::resolve(methodCallExpr,
+                                              control->program->refMap,
+                                              control->program->typeMap);
+        auto ext = mi->to<P4::ExternMethod>();
+        if (ext == nullptr) {
+            return false;
+        }
+
+        if (ext->originalExternType->name.name == "Register" &&
+            ext->method->type->name == "read") {
+            cstring name = EBPFObject::externalName(ext->object);
+            auto reg = control->to<EBPFControlPSA>()->getRegister(name);
+            reg->emitRegisterRead(builder, ext, this, a->left);
+            return false;
+        }
+    }
+
+    return CodeGenInspector::preorder(a);
+}
+
 void ControlBodyTranslatorPSA::processMethod(const P4::ExternMethod* method) {
     auto decl = method->object;
     auto declType = method->originalExternType;
@@ -32,9 +54,48 @@ void ControlBodyTranslatorPSA::processMethod(const P4::ExternMethod* method) {
         auto counterMap = control->getCounter(name);
         counterMap->to<EBPFCounterPSA>()->emitMethodInvocation(builder, method, this);
         return;
+    } else if (declType->name.name == "Register") {
+        auto reg = control->to<EBPFControlPSA>()->getRegister(name);
+        if (method->method->type->name == "write") {
+            reg->emitRegisterWrite(builder, method, this);
+        } else if (method->method->type->name == "read") {
+            ::warning(ErrorType::WARN_UNUSED, "This Register(%1%) read value is not used!", name);
+            reg->emitRegisterRead(builder, method, this, nullptr);
+        }
+        return;
+    } else {
+        ::error(ErrorType::ERR_UNSUPPORTED_ON_TARGET,
+                "%1%: Unexpected method call", method->expr);
     }
+}
+
+cstring ControlBodyTranslatorPSA::getParamName(const IR::PathExpression *expr) {
+    return expr->path->name.name;
+}
+
+void EBPFControlPSA::emitTableTypes(CodeBuilder *builder) {
+    EBPFControl::emitTableTypes(builder);
+
+    for (auto it : registers)
+        it.second->emitTypes(builder);
+}
 
-    ControlBodyTranslator::processMethod(method);
+void EBPFControlPSA::emitTableInstances(CodeBuilder* builder) {
+    for (auto it : tables)
+        it.second->emitInstance(builder);
+    for (auto it : counters)
+        it.second->emitInstance(builder);
+    for (auto it : registers)
+        it.second->emitInstance(builder);
+}
+
+void EBPFControlPSA::emitTableInitializers(CodeBuilder* builder) {
+    for (auto it : tables) {
+        it.second->emitInitializer(builder);
+    }
+    for (auto it : registers) {
+        it.second->emitInitializer(builder);
+    }
 }
 
 }
diff --git a/backends/ebpf/psa/ebpfPsaControl.h b/backends/ebpf/psa/ebpfPsaControl.h
@@ -19,6 +19,7 @@ limitations under the License.
 
 #include "ebpfPsaTable.h"
 #include "backends/ebpf/ebpfControl.h"
+#include "backends/ebpf/psa/externs/ebpfPsaRegister.h"
 
 namespace EBPF {
 
@@ -28,7 +29,11 @@ class ControlBodyTranslatorPSA : public ControlBodyTranslator {
  public:
     explicit ControlBodyTranslatorPSA(const EBPFControlPSA* control);
 
+    bool preorder(const IR::AssignmentStatement* a) override;
+
     void processMethod(const P4::ExternMethod* method) override;
+
+    virtual cstring getParamName(const IR::PathExpression *);
 };
 
 class ActionTranslationVisitorPSA : public ActionTranslationVisitor,
@@ -44,6 +49,8 @@ class ActionTranslationVisitorPSA : public ActionTranslationVisitor,
     bool isActionParameter(const IR::Expression *expression) const;
 
     void processMethod(const P4::ExternMethod* method) override;
+    cstring getParamInstanceName(const IR::Expression *expression) const override;
+    cstring getParamName(const IR::PathExpression *) override;
 };
 
 class EBPFControlPSA : public EBPFControl {
@@ -55,9 +62,20 @@ class EBPFControlPSA : public EBPFControl {
     const IR::Parameter* inputStandardMetadata;
     const IR::Parameter* outputStandardMetadata;
 
+    std::map<cstring, EBPFRegisterPSA*>  registers;
+
     EBPFControlPSA(const EBPFProgram* program, const IR::ControlBlock* control,
                    const IR::Parameter* parserHeaders) :
         EBPFControl(program, control, parserHeaders) {}
+
+    void emitTableTypes(CodeBuilder* builder) override;
+    void emitTableInstances(CodeBuilder* builder) override;
+    void emitTableInitializers(CodeBuilder* builder) override;
+
+    EBPFRegisterPSA* getRegister(cstring name) const {
+        auto result = ::get(registers, name);
+        BUG_CHECK(result != nullptr, "No register named %1%", name);
+        return result; }
 };
 
 }  // namespace EBPF

diff --git a/backends/ebpf/psa/ebpfPsaGen.cpp b/backends/ebpf/psa/ebpfPsaGen.cpp
@@ -633,6 +633,9 @@ bool ConvertToEBPFControlPSA::preorder(const IR::ExternBlock* instance) {
     } else if (typeName == "Counter") {
         auto ctr = new EBPFCounterPSA(program, di, name, control->codeGen);
         control->counters.emplace(name, ctr);
+    } else if (typeName == "Register") {
+        auto reg = new EBPFRegisterPSA(program, name, di, control->codeGen);
+        control->registers.emplace(name, reg);
     } else if (typeName == "DirectCounter") {
         // instance will be created by table
         return false;

diff --git a/backends/ebpf/psa/ebpfPsaTable.cpp b/backends/ebpf/psa/ebpfPsaTable.cpp
@@ -161,6 +161,22 @@ void ActionTranslationVisitorPSA::processMethod(const P4::ExternMethod* method)
     }
 }
 
+cstring ActionTranslationVisitorPSA::getParamInstanceName(
+        const IR::Expression *expression) const {
+    if (auto cast = expression->to<IR::Cast>())
+        expression = cast->expr;
+
+    return ActionTranslationVisitor::getParamInstanceName(expression);
+}
+
+cstring ActionTranslationVisitorPSA::getParamName(const IR::PathExpression *expr) {
+    if (isActionParameter(expr)) {
+        return getParamInstanceName(expr);
+    }
+
+    return ControlBodyTranslatorPSA::getParamName(expr);
+}
+
 // =====================EBPFTablePSA=============================
 EBPFTablePSA::EBPFTablePSA(const EBPFProgram* program, const IR::TableBlock* table,
                            CodeGenInspector* codeGen) :