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

[Minsoo Choo 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);
----------------
mchoo7 wrote:

Yes.

On arm32, the psr field in struct trapframe determines if the frame was in user mode or in kernel mode, and SP and LR are at different offset based on the value of psr. i386 does similar thing but with SS/ESP registers. Other architectures don't have this mechanism.

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