feat: add relocation header and implementation for RISC-V architecture

2 files changed, 153 insertions, 0 deletions

diff --git a/na/arch/riscv/relocate.cc b/na/arch/riscv/relocate.cc
new file mode 100644
index 0000000..0216827
--- /dev/null
+++ b/na/arch/riscv/relocate.cc
@@ -0,0 +1,100 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Copyright (C) 2026 Richard Qin */
+
+#include <lume/relocate.h>
+
+static inline bool range_ok(uint64 offset, uint64 size, uint64 image_size)
+{
+    if (offset > image_size) {
+        return false;
+    }
+    if (size > image_size - offset) {
+        return false;
+    }
+    return true;
+}
+
+RelocStatus relocate_apply(uint64 load_base, uint64 image_size,
+                           uint64 link_base, const void* reloc_blob,
+                           uint64 reloc_size)
+{
+    if (!reloc_blob || reloc_size == 0) {
+        return RELOC_OK;
+    }
+    if (reloc_size < sizeof(RelocTableHeader)) {
+        return RELOC_ERR_SIZE;
+    }
+
+    const auto* hdr = reinterpret_cast<const RelocTableHeader*>(reloc_blob);
+    if (hdr->magic != kRelocTableMagic) {
+        return RELOC_ERR_MAGIC;
+    }
+    if (hdr->version != kRelocTableVersion) {
+        return RELOC_ERR_VERSION;
+    }
+    if (hdr->arch != RELOC_ARCH_RISCV) {
+        return RELOC_ERR_ARCH;
+    }
+    if (hdr->entry_size < sizeof(RelocEntry) || (hdr->entry_size % 8) != 0) {
+        return RELOC_ERR_SIZE;
+    }
+
+    uint64 max_entries = (reloc_size - sizeof(RelocTableHeader)) /
+        static_cast<uint64>(hdr->entry_size);
+    if (hdr->entry_count > max_entries) {
+        return RELOC_ERR_SIZE;
+    }
+
+    if (image_size < sizeof(uint64)) {
+        return RELOC_ERR_RANGE;
+    }
+
+    const uint64 delta = load_base - link_base;
+    const uint8* p = reinterpret_cast<const uint8*>(reloc_blob) +
+                     sizeof(RelocTableHeader);
+
+    for (uint32 i = 0; i < hdr->entry_count; ++i) {
+        const auto* ent = reinterpret_cast<const RelocEntry*>(p);
+        if ((ent->offset & 0x7) != 0 ||
+            !range_ok(ent->offset, sizeof(uint64), image_size)) {
+            return RELOC_ERR_RANGE;
+        }
+
+        uint64* target = reinterpret_cast<uint64*>(load_base + ent->offset);
+        switch (ent->type) {
+        case RELOC_RISCV_RELATIVE:
+            *target = load_base + ent->addend;
+            break;
+        case RELOC_RISCV_64:
+            *target = ent->addend + delta;
+            break;
+        default:
+            return RELOC_ERR_UNSUPPORTED;
+        }
+        p += hdr->entry_size;
+    }
+
+    return RELOC_OK;
+}
+
+const char* reloc_status_str(RelocStatus st)
+{
+    switch (st) {
+    case RELOC_OK:
+        return "ok";
+    case RELOC_ERR_MAGIC:
+        return "bad magic";
+    case RELOC_ERR_VERSION:
+        return "bad version";
+    case RELOC_ERR_ARCH:
+        return "arch mismatch";
+    case RELOC_ERR_SIZE:
+        return "size mismatch";
+    case RELOC_ERR_RANGE:
+        return "range";
+    case RELOC_ERR_UNSUPPORTED:
+        return "unsupported";
+    default:
+        return "unknown";
+    }
+}
diff --git a/na/include/lume/relocate.h b/na/include/lume/relocate.h
new file mode 100644
index 0000000..120824f
--- /dev/null
+++ b/na/include/lume/relocate.h
@@ -0,0 +1,53 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Copyright (C) 2026 Richard Qin */
+
+#pragma once
+
+#include <lume/types.h>
+
+inline constexpr uint64 kRelocTableMagic = 0x4C554D45524C4F43ULL; /* LUMERLOC */
+inline constexpr uint16 kRelocTableVersion = 1;
+
+enum RelocArch : uint16 {
+    RELOC_ARCH_RISCV = 1,
+    RELOC_ARCH_AARCH64 = 2,
+    RELOC_ARCH_X86_64 = 3,
+};
+
+enum RelocType : uint32 {
+    RELOC_RISCV_RELATIVE = 1,
+    RELOC_RISCV_64 = 2,
+};
+
+struct RelocTableHeader {
+    uint64 magic;
+    uint16 version;
+    uint16 arch;
+    uint32 entry_size;
+    uint32 entry_count;
+    uint32 reserved;
+};
+
+struct RelocEntry {
+    uint64 offset;
+    uint64 addend;
+    uint32 type;
+    uint32 reserved;
+};
+
+enum RelocStatus : uint32 {
+    RELOC_OK = 0,
+    RELOC_ERR_MAGIC,
+    RELOC_ERR_VERSION,
+    RELOC_ERR_ARCH,
+    RELOC_ERR_SIZE,
+    RELOC_ERR_RANGE,
+    RELOC_ERR_UNSUPPORTED,
+};
+
+/* Apply relocations to the image loaded at load_base. */
+RelocStatus relocate_apply(uint64 load_base, uint64 image_size,
+                           uint64 link_base, const void* reloc_blob,
+                           uint64 reloc_size);
+
+const char* reloc_status_str(RelocStatus st);