WCH-Link erase command doesn't erase the whole chip, as initially thought. It only erases the program memory segment.

The boot segment appears to be left untouched.

src/DebugServer/Gdb/RiscVGdb/CommandPackets/FlashErase.cpp

@@ -45,14 +45,27 @@ namespace DebugServer::Gdb::RiscVGdb::CommandPackets
         Logger::info("Handling FlashErase packet");
 
         try {
+            const auto segmentDescriptorOpt = gdbTargetDescriptor.systemAddressSpaceDescriptor.getContainingMemorySegmentDescriptor(
+                this->startAddress
+            );
+
+            if (!segmentDescriptorOpt.has_value()) {
+                throw Exception{"Invalid command - no containing memory segment found for the given start address"};
+            }
+
+            const auto& segmentDescriptor = segmentDescriptorOpt->get();
+            if (!segmentDescriptor.programmingModeAccess.writeable) {
+                throw Exception{"Memory segment (\"" + segmentDescriptor.name + "\") not writable in programming mode"};
+            }
+
+            Logger::warning("Erasing \"" + segmentDescriptor.name + "\" segment, in preparation for programming");
+
             targetControllerService.enableProgrammingMode();
 
-            Logger::warning("Erasing program memory, in preparation for programming");
-
-            // We don't erase a specific address range - we just erase the entire program memory.
+            // We don't erase a specific address range - we just erase the entire segment
             targetControllerService.eraseMemory(
                 gdbTargetDescriptor.systemAddressSpaceDescriptor,
-                gdbTargetDescriptor.programMemorySegmentDescriptor
+                segmentDescriptor
             );
 
             debugSession.connection.writePacket(OkResponsePacket{});

src/DebugToolDrivers/WCH/Protocols/WchLink/Commands/EraseProgramMemory.hpp

@@ -6,10 +6,10 @@
 
 namespace DebugToolDrivers::Wch::Protocols::WchLink::Commands
 {
-    class EraseChip: public Command<std::array<unsigned char, 1>>
+    class EraseProgramMemory: public Command<std::array<unsigned char, 1>>
     {
     public:
-        EraseChip()
+        EraseProgramMemory()
             : Command(0x02)
         {
             this->payload = {

src/DebugToolDrivers/WCH/Protocols/WchLink/WchLinkInterface.cpp

@@ -16,7 +16,7 @@
 #include "Commands/StartRamCodeWrite.hpp"
 #include "Commands/EndRamCodeWrite.hpp"
 #include "Commands/WriteFlash.hpp"
-#include "Commands/EraseChip.hpp"
+#include "Commands/EraseProgramMemory.hpp"
 
 #include "src/Helpers/BiMap.hpp"
 #include "src/Services/StringService.hpp"
@@ -243,7 +243,7 @@ namespace DebugToolDrivers::Wch::Protocols::WchLink
         this->sendCommandAndWaitForResponse(Commands::EndProgrammingSession{});
     }
 
-    void WchLinkInterface::eraseChip() {
-        this->sendCommandAndWaitForResponse(Commands::EraseChip{});
+    void WchLinkInterface::eraseProgramMemory() {
+        this->sendCommandAndWaitForResponse(Commands::EraseProgramMemory{});
     }
 }

src/DebugToolDrivers/WCH/Protocols/WchLink/WchLinkInterface.hpp

@@ -52,7 +52,7 @@ namespace DebugToolDrivers::Wch::Protocols::WchLink
             Targets::TargetMemorySize blockSize,
             std::span<const unsigned char> flashProgramOpcodes
         );
-        void eraseChip();
+        void eraseProgramMemory();
 
         template <class CommandType>
         auto sendCommandAndWaitForResponse(const CommandType& command) {

src/DebugToolDrivers/WCH/WchLinkDebugInterface.cpp

@@ -57,6 +57,11 @@ namespace DebugToolDrivers::Wch
                 this->targetConfig
             }
         )
+        , programSegmentDescriptor(
+            this->targetDescriptionFile.getSystemAddressSpaceDescriptor().getMemorySegmentDescriptor(
+                "internal_program_memory"
+            )
+        )
         , flashProgramOpcodes(
             WchLinkDebugInterface::getFlashProgramOpcodes(
                 this->targetDescriptionFile.getProperty("wch_link_interface", "programming_opcode_key").value
@@ -352,11 +357,11 @@ namespace DebugToolDrivers::Wch
         const TargetAddressSpaceDescriptor& addressSpaceDescriptor,
         const TargetMemorySegmentDescriptor& memorySegmentDescriptor
     ) {
-        if (memorySegmentDescriptor.type == TargetMemorySegmentType::FLASH) {
-            return this->eraseFlashMemory();
+        if (memorySegmentDescriptor == this->programSegmentDescriptor) {
+            return this->wchLinkInterface.eraseProgramMemory();
         }
 
-        throw Exception{"Erasing non-flash memory not supported in WchLinkDebugInterface"};
+        // Ignore other (non-program memory) erase requests, for now.
     }
 
     void WchLinkDebugInterface::enableProgrammingMode() {
@@ -471,10 +476,6 @@ namespace DebugToolDrivers::Wch
         this->softwareBreakpointRegistry.remove(softwareBreakpoint);
     }
 
-    void WchLinkDebugInterface::eraseFlashMemory() {
-        this->wchLinkInterface.eraseChip();
-    }
-
     std::span<const unsigned char> WchLinkDebugInterface::getFlashProgramOpcodes(const std::string& key) {
         if (key == "op1") {
             return FlashProgramOpcodes::FLASH_OP1;

src/DebugToolDrivers/WCH/WchLinkDebugInterface.hpp

@@ -89,6 +89,8 @@ namespace DebugToolDrivers::Wch
         Protocols::WchLink::WchLinkInterface& wchLinkInterface;
         DebugToolDrivers::Protocols::RiscVDebugSpec::DebugTranslator riscVTranslator;
 
+        const Targets::TargetMemorySegmentDescriptor& programSegmentDescriptor;
+
         /**
          * The 'target activation' command returns a payload of 5 bytes.
          *
@@ -107,7 +109,6 @@ namespace DebugToolDrivers::Wch
         void setSoftwareBreakpoint(const Targets::TargetProgramBreakpoint& breakpoint);
         void clearSoftwareBreakpoint(const Targets::TargetProgramBreakpoint& breakpoint);
 
-        void eraseFlashMemory();
         static std::span<const unsigned char> getFlashProgramOpcodes(const std::string& key);
     };
 }