[Lldb-commits] [lldb] [lldb][FreeBSDKernel] Implement trapframe unwinding (PR #192184)

[David Spickett via lldb-commits]

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@@ -0,0 +1,60 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "PlatformFreeBSDKernel.h"
+
+#include <cstddef>
+#if defined(__FreeBSD__) && defined(__aarch64__)
+#include <machine/frame.h>
+#endif
+
+using namespace lldb_private::platform_freebsdkernel;
+
+// DWARF register numbers for AArch64.
+static constexpr uint32_t kDwarfSP = 31;
+static constexpr uint32_t kDwarfPC = 32;
+static constexpr uint32_t kDwarfLR = 30;   // x30
+static constexpr uint32_t kDwarfCPSR = 33; // PSTATE / CPSR
+
+// Trapframe byte offsets.
+// struct trapframe layout (sys/arm64/include/frame.h, FreeBSD 14+):
+static constexpr int32_t kTfSP = 0;
+static constexpr int32_t kTfLR = 8;
+static constexpr int32_t kTfELR = 16;    // saved PC
+static constexpr int32_t kTfSPSR = 24;   // cpsr
+static constexpr int32_t kTfX0Base = 48; // tf_x[0]; tf_x[n] = kTfX0Base + n*8
+
+#if defined(__FreeBSD__) && defined(__aarch64__)
+static_assert(offsetof(struct trapframe, tf_sp) == (size_t)kTfSP,
+              "tf_sp offset mismatch");
+static_assert(offsetof(struct trapframe, tf_lr) == (size_t)kTfLR,
+              "tf_lr offset mismatch");
+static_assert(offsetof(struct trapframe, tf_elr) == (size_t)kTfELR,
+              "tf_elr offset mismatch");
+static_assert(offsetof(struct trapframe, tf_spsr) == (size_t)kTfSPSR,
+              "tf_spsr offset mismatch");
+static_assert(offsetof(struct trapframe, tf_x[0]) == (size_t)kTfX0Base,
+              "tf_x[0] offset mismatch");
+#endif
+
+lldb::UnwindPlanSP
+PlatformFreeBSDKernel::GetTrapframeUnwindPlan_arm64(ConstString name) {
+  std::vector<std::pair<uint32_t, int32_t>> regs;
+  regs.reserve(33);
+
+  regs.push_back({kDwarfSP, kTfSP});
+  regs.push_back({kDwarfLR, kTfLR});
+  regs.push_back({kDwarfPC, kTfELR});
+  regs.push_back({kDwarfCPSR, kTfSPSR});
+
+  for (int i = 0; i <= 29; i++)
+    regs.push_back({(uint32_t)i, kTfX0Base + i * 8});
+
+  return BuildTrapframeUnwindPlan("FreeBSD aarch64 trapframe", kDwarfSP, 0,
+                                  regs);
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DavidSpickett wrote:

Maybe a silly question but how do we know that the layout of registers in the trap frame is the same for all the possible trap handler functions?

And is this why you are not implementing aarch32 and i386, because on those architectures, the layouts do in fact change?

https://github.com/llvm/llvm-project/pull/192184