1 files changed, 92 insertions, 0 deletions
diff --git a/arch/riscv/trap/extable.cc b/arch/riscv/trap/extable.cc
new file mode 100644
index 0000000..57a3dc1
--- /dev/null
+++ b/arch/riscv/trap/extable.cc
@@ -0,0 +1,92 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Copyright (C) 2026 Richard Qin */
+
+#include <arch/extable.h>
+#include <lume/types.h>
+
+extern struct ExceptionTableEntry __extable_start[];
+extern struct ExceptionTableEntry __extable_end[];
+
+static void swap_extable_entries(struct ExceptionTableEntry *a, struct ExceptionTableEntry *b) {
+    uint64 a_insn = reinterpret_cast<uint64>(&a->insn) + a->insn;
+    uint64 a_fixup = reinterpret_cast<uint64>(&a->fixup) + a->fixup;
+    uint64 b_insn = reinterpret_cast<uint64>(&b->insn) + b->insn;
+    uint64 b_fixup = reinterpret_cast<uint64>(&b->fixup) + b->fixup;
+
+    a->insn = static_cast<int32>(b_insn - reinterpret_cast<uint64>(&a->insn));
+    a->fixup = static_cast<int32>(b_fixup - reinterpret_cast<uint64>(&a->fixup));
+    b->insn = static_cast<int32>(a_insn - reinterpret_cast<uint64>(&b->insn));
+    b->fixup = static_cast<int32>(a_fixup - reinterpret_cast<uint64>(&b->fixup));
+}
+
+static void sort_extable(size_t left, size_t right) {
+    if (left >= right) return;
+
+    size_t mid_idx = left + (right - left) / 2;
+    struct ExceptionTableEntry *pivot = &__extable_start[mid_idx];
+    uint64 pivot_val = reinterpret_cast<uint64>(&pivot->insn) + pivot->insn;
+
+    size_t i = left;
+    size_t j = right;
+
+    while (i <= j) {
+        while ((reinterpret_cast<uint64>(&__extable_start[i].insn) + __extable_start[i].insn) < pivot_val) {
+            i++;
+        }
+        while ((reinterpret_cast<uint64>(&__extable_start[j].insn) + __extable_start[j].insn) > pivot_val) {
+            if (j == 0) {
+                break;
+            }
+            j--;
+        }
+        if (i <= j) {
+            swap_extable_entries(&__extable_start[i], &__extable_start[j]);
+            i++;
+            if (j == 0) {
+                break;
+            }
+            j--;
+        }
+    }
+
+    if (j > left) {
+        sort_extable(left, j);
+    }
+    if (i < right) {
+        sort_extable(i, right);
+    }
+}
+
+void extable_init() {
+    size_t count = __extable_end - __extable_start;
+    if (count <= 1) return;
+    sort_extable(0, count - 1);
+}
+
+uint64 search_extable(uint64 pc) {
+    size_t count = __extable_end - __extable_start;
+    if (count == 0) return 0;
+
+    size_t left = 0;
+    size_t right = count - 1;
+
+    /* Binary search */
+    while (left <= right) {
+        size_t mid = left + (right - left) / 2;
+        const struct ExceptionTableEntry *entry = &__extable_start[mid];
+        uint64 mid_pc = reinterpret_cast<uint64>(&entry->insn) + entry->insn;
+
+        if (mid_pc == pc) {
+            return reinterpret_cast<uint64>(&entry->fixup) + entry->fixup;
+        }
+
+        if (mid_pc < pc) {
+            left = mid + 1;
+        } else {
+            if (mid == 0) break;
+            right = mid - 1;
+        }
+    }
+
+    return 0;
+}