From c32d85ea2d88a26d7d2b5853f1c788c8676ed970 Mon Sep 17 00:00:00 2001
From: Nikita Smith <git.nikita.smith@gmail.com>
Date: Mon, 13 Oct 2025 12:02:33 -0700
Subject: [PATCH] DWARF helper

---
 src/dwarf/dwarf_help.c | 71 ++++++++++++++++++++++++++++++++++++++++++
 src/dwarf/dwarf_help.h | 18 +++++++++++
 2 files changed, 89 insertions(+)
 create mode 100644 src/dwarf/dwarf_help.c
 create mode 100644 src/dwarf/dwarf_help.h

diff --git a/src/dwarf/dwarf_help.c b/src/dwarf/dwarf_help.c
new file mode 100644
index 00000000..547c171f
--- /dev/null
+++ b/src/dwarf/dwarf_help.c
@@ -0,0 +1,71 @@
+// Copyright (c) Epic Games Tools
+// Licensed under the MIT license (https://opensource.org/license/mit/)
+
+internal
+DW_CIE_FROM_OFFSET_FUNC(dw_call_frame_info_cie_from_offset)
+{
+  return hash_table_search_u64_raw(ud, offset);
+}
+
+internal DW_CallFrameInfo
+dw_call_frame_info_from_data(Arena *arena, Arch arch, U64 rebase, String8 debug_frame)
+{
+  Temp scratch = scratch_begin(&arena, 1);
+
+  // count CIE and FDE entries
+  U64 cie_count = 0, fde_count = 0;
+  for (U64 cursor = 0, desc_size; cursor < debug_frame.size; cursor += desc_size) {
+    DW_DescriptorEntry desc = {0};
+    desc_size = dw_parse_descriptor_entry_header(debug_frame, cursor, &desc);
+    if (desc_size == 0) { break; }
+    if (desc.type == DW_DescriptorEntryType_CIE) {
+      cie_count += 1;
+    } else if (desc.type == DW_DescriptorEntryType_FDE) {
+      fde_count += 1;
+    }
+  }
+
+  // parse CIEs and build (offset -> CIE) hash table
+  HashTable *cie_ht = hash_table_init(scratch.arena, (U64)(cie_count * 1.3));
+  DW_CIE *cie = push_array(arena, DW_CIE, cie_count);
+  U64 parse_cie_count = 0;
+  for (U64 cursor = 0, desc_size; cursor < debug_frame.size; cursor += desc_size) {
+    DW_DescriptorEntry desc = {0};
+    desc_size = dw_parse_descriptor_entry_header(debug_frame, cursor, &desc);
+    if (desc_size == 0) { break; }
+    if (desc.type == DW_DescriptorEntryType_CIE) {
+      if (dw_parse_cie(str8_skip(debug_frame, cursor), desc.format, arch, &cie[parse_cie_count])) {
+        hash_table_push_u64_raw(scratch.arena, cie_ht, cursor, &cie[parse_cie_count]);
+        parse_cie_count += 1;
+      }
+    }
+  }
+
+  // parse FDEs
+  DW_FDE *fde = push_array(arena, DW_FDE, fde_count);
+  U64 parse_fde_count = 0;
+  for (U64 cursor = 0, desc_size; cursor < debug_frame.size; cursor += desc_size) {
+    DW_DescriptorEntry desc = {0};
+    desc_size = dw_parse_descriptor_entry_header(debug_frame, cursor, &desc);
+    if (desc_size == 0) { break; }
+    if (desc.type == DW_DescriptorEntryType_FDE) {
+      if (dw_parse_fde(str8_skip(debug_frame, cursor), desc.format, dw_call_frame_info_cie_from_offset, cie_ht, &fde[parse_fde_count])) {
+        fde[parse_fde_count].pc_range.min += rebase;
+        fde[parse_fde_count].pc_range.max += rebase;
+        parse_fde_count += 1;
+      }
+    }
+  }
+
+  // fill out result
+  DW_CallFrameInfo cfi = {0};
+  cfi.cie_count = parse_cie_count;
+  cfi.fde_count = parse_fde_count;
+  cfi.cie       = cie;
+  cfi.fde       = fde;
+
+  scratch_end(scratch);
+  return cfi;
+}
+
+
diff --git a/src/dwarf/dwarf_help.h b/src/dwarf/dwarf_help.h
new file mode 100644
index 00000000..2882c6b6
--- /dev/null
+++ b/src/dwarf/dwarf_help.h
@@ -0,0 +1,18 @@
+// Copyright (c) Epic Games Tools
+// Licensed under the MIT license (https://opensource.org/license/mit/)
+
+#ifndef DWARF_HELP_H
+#define DWARF_HELP_H
+
+typedef struct DW_CallFrameInfo
+{
+  U64 cie_count;
+  U64 fde_count;
+  DW_CIE *cie;
+  DW_FDE *fde;
+} DW_CallFrameInfo;
+
+internal DW_CallFrameInfo dw_call_frame_info_from_data(Arena *arena, Arch arch, U64 rebase, String8 debug_frame);
+
+#endif // DWARF_HELP_H
+