From c98ae0925fd0afd87242bee6933fc61dd328bdac Mon Sep 17 00:00:00 2001
From: Nikita Smith <git.nikita.smith@gmail.com>
Date: Sun, 18 May 2025 18:19:10 -0700
Subject: [PATCH] error check relocations

---
 src/coff/coff.h        |  1 +
 src/linker/lnk.c       | 19 ++++++++++++++++++-
 src/linker/lnk_error.h |  1 +
 3 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/src/coff/coff.h b/src/coff/coff.h
index 2dd187b6..a0f18d2e 100644
--- a/src/coff/coff.h
+++ b/src/coff/coff.h
@@ -385,6 +385,7 @@ enum
   COFF_Reloc_X64_Pair       = 0xF,
   COFF_Reloc_X64_SSpan32    = 0x10,
   COFF_Reloc_X64_Unknown_11 = 0x11,
+  COFF_Reloc_X64_Last       = COFF_Reloc_X64_Unknown_11,
 };
 
 typedef COFF_RelocType COFF_Reloc_X86;
diff --git a/src/linker/lnk.c b/src/linker/lnk.c
index 32f771e3..47264f38 100644
--- a/src/linker/lnk.c
+++ b/src/linker/lnk.c
@@ -1101,6 +1101,15 @@ THREAD_POOL_TASK_FUNC(lnk_obj_reloc_patcher)
     for (U64 reloc_idx = 0; reloc_idx < reloc_info.count; reloc_idx += 1) {
       COFF_Reloc *reloc = &relocs[reloc_idx];
 
+      // error check relocation
+      if (obj->header.machine == COFF_MachineType_X64) {
+        if (reloc->type > COFF_Reloc_X64_Last) {
+          lnk_error_obj(LNK_Error_IllegalRelocation, obj, "unknown relocation 0x%x", reloc->type);
+        }
+      } else if (obj->header.machine == COFF_MachineType_Unknown) {
+        NotImplemented;
+      }
+
       // compute relocation file/virtual offsets
       U64 reloc_foff = section_header->foff + reloc->apply_off;
       U64 reloc_voff = section_header->voff + reloc->apply_off;
@@ -1121,8 +1130,16 @@ THREAD_POOL_TASK_FUNC(lnk_obj_reloc_patcher)
         if (interp == COFF_SymbolValueInterp_Regular) {
           symbol_secnum = symbol.section_number;
           symbol_secoff = symbol.value;
-          symbol_voff = task->image_section_table[symbol.section_number]->voff + symbol_secoff;
+          symbol_voff = safe_cast_u32((U64)task->image_section_table[symbol.section_number]->voff + (U64)symbol_secoff);
         } else if (interp == COFF_SymbolValueInterp_Abs) {
+          // error check relocation
+          if (obj->header.machine == COFF_MachineType_X64) {
+            if (reloc->type == COFF_Reloc_X64_SecRel) {
+              lnk_error_obj(LNK_Error_IllegalRelocation, obj, "section-relative relocation (No. 0x%x) cannot be applied to absolute symbol (No. 0x%x)", reloc_idx, reloc->isymbol);
+            }
+          } else if (obj->header.machine != COFF_MachineType_Unknown) {
+            NotImplemented;
+          }
           symbol_secnum = 0;
           symbol_secoff = 0;
           symbol_voff = safe_cast_u32(symbol.value);
diff --git a/src/linker/lnk_error.h b/src/linker/lnk_error.h
index d1fa096c..af146ade 100644
--- a/src/linker/lnk_error.h
+++ b/src/linker/lnk_error.h
@@ -35,6 +35,7 @@ typedef enum
   LNK_Error_MultiplyDefinedSymbol,
   LNK_Error_SectRefsDiscardedMemory,
   LNK_Error_IllegalSectionMerge,
+  LNK_Error_IllegalRelocation,
   LNK_Error_StopLast,
   
   LNK_Error_First,