[Lldb-commits] [lldb] [lldb][riscv] Fix setting breakpoint for undecoded instruction (PR #90075)

[via lldb-commits]

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@@ -115,8 +148,23 @@ Status NativeProcessSoftwareSingleStep::SetupSoftwareSingleStepping(
   emulator_up->SetWriteMemCallback(&WriteMemoryCallback);
   emulator_up->SetWriteRegCallback(&WriteRegisterCallback);
 
-  if (!emulator_up->ReadInstruction())
-    return Status("Read instruction failed!");
+  if (!emulator_up->ReadInstruction()) {
+    // try to get at least the size of next instruction to set breakpoint.
+    auto instrSizeOpt = emulator_up->GetLastInstrSize();
+    if (!instrSizeOpt)
+      return Status("Read instruction failed!");
+    bool success = false;
+    auto pc = emulator_up->ReadRegisterUnsigned(eRegisterKindGeneric,
+                                                LLDB_REGNUM_GENERIC_PC,
+                                                LLDB_INVALID_ADDRESS, &success);
+    if (!success)
+      return Status("Reading pc failed!");
+    lldb::addr_t next_pc = pc + *instrSizeOpt;
+    auto Result =
+        SetSoftwareBreakPointOnPC(arch, next_pc, /* next_flags */ 0x0, process);
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ita-sc wrote:

Actually, I do not understand fully what you mean. For RISCV software breakpoint size is 4 or 2 (currently LLDB hardcodes only 4). We save memory and restore it later, so it seems we will have no problems here for different instruction sizes on memory regions where we write software breakpoint.

https://github.com/llvm/llvm-project/pull/90075