[Lldb-commits] [lldb] [lldb] Step over non-lldb breakpoints (PR #174348)

[Duncan McBain via lldb-commits]

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@@ -82,6 +83,41 @@ bool StopInfo::HasTargetRunSinceMe() {
   return false;
 }
 
+void StopInfo::SkipOverTrapInstruction() {
+  Status error;
+  Log *log = GetLog(LLDBLog::Process);
+
+  // We don't expect to see byte sequences longer than four bytes long for
+  // any breakpoint instructions known to LLDB.
+  std::array<uint8_t, 4> bytes_at_pc = {0, 0, 0, 0};
+  auto reg_ctx_sp = GetThread()->GetRegisterContext();
+  auto process_sp = GetThread()->GetProcess();
+  addr_t pc = reg_ctx_sp->GetPC();
+  if (!process_sp->ReadMemory(pc, bytes_at_pc.data(), bytes_at_pc.size(),
+                              error)) {
+    // If this fails, we simply don't handle the step-over-break logic.
+    LLDB_LOG(log, "failed to read program bytes at pc address {}, error {}", pc,
+             error);
+    return;
+  }
+
+  auto &target = process_sp->GetTarget();
+  auto platform_sp = target.GetPlatform();
+  auto size_hint = platform_sp->GetTrapOpcodeSizeHint(target, pc, bytes_at_pc);
+  auto platform_opcode =
+      platform_sp->SoftwareTrapOpcodeBytes(target.GetArchitecture(), size_hint);
+
+  if (auto *arch_plugin = target.GetArchitecturePlugin();
+      arch_plugin &&
+      arch_plugin->IsValidTrapInstruction(
+          platform_opcode,
+          llvm::ArrayRef<uint8_t>(bytes_at_pc.data(), bytes_at_pc.size()))) {
+    LLDB_LOG(log, "stepping over breakpoint in inferior to new pc: {}",
+             pc + platform_opcode.size());
+    reg_ctx_sp->SetPC(pc + platform_opcode.size());
----------------
DuncanMcBain wrote:

That's correct in so far as we should never hit this on x86(_64) platforms, but ideally we should never run into this code when hitting a "real" breakpoint regardless. This should (to my understanding) only be hit when lldb gets a stop signal where it can't attribute this to a breakpoint it set. Therefore, I expect that this will *always* do the right size step, because the trap instruction  must be present in the binary (i.e. as output by the compiler).

https://github.com/llvm/llvm-project/pull/174348