Basic 32-bit SYMTAB and REL (not RELA) support

[centaur.git] / src / model / relocate.c

diff --git a/src/model/relocate.c b/src/model/relocate.c
new file mode 100644 (file)
index 0000000..1b4f9ff
--- /dev/null
+++ b/src/model/relocate.c
@@ -0,0 +1,85 @@
+#include <assert.h>
+#include <stdlib.h>
+#include <libelfu/libelfu.h>
+
+
+static GElf_Word symtabLookupVal(ElfuElf *metarget, ElfuScn *msst, GElf_Word entry)
+{
+  GElf_Word i;
+  ElfuSym *sym;
+
+  assert(metarget);
+  assert(msst);
+  assert(msst->symtab);
+  assert(entry > 0);
+  assert(!CIRCLEQ_EMPTY(&msst->symtab->syms));
+
+  sym = CIRCLEQ_FIRST(&msst->symtab->syms);
+  for (i = 1; i < entry; i++) {
+    sym = CIRCLEQ_NEXT(sym, elem);
+  }
+
+  switch (sym->type) {
+    case STT_NOTYPE:
+    case STT_OBJECT:
+    case STT_FUNC:
+      if (sym->scnptr) {
+        assert(elfu_mScnByOldscn(metarget, sym->scnptr));
+        return elfu_mScnByOldscn(metarget, sym->scnptr)->shdr.sh_addr + sym->value;
+      } else {
+        // TODO: UNDEF, ABS, or COMMON
+        ELFU_WARN("symtabLookupVal: Returning 0 for UNDEF, ABS, or COMMON symbol.\n");
+      }
+      break;
+    case STT_SECTION:
+      assert(sym->scnptr);
+      assert(elfu_mScnByOldscn(metarget, sym->scnptr));
+      return elfu_mScnByOldscn(metarget, sym->scnptr)->shdr.sh_addr;
+    case STT_FILE:
+      // TODO
+      ELFU_WARN("symtabLookupVal: Returning 0 for FILE symbol.\n");
+      break;
+    default:
+      ELFU_WARN("symtabLookupVal: Unknown symbol type %d.\n", sym->type);
+      return 0;
+  }
+}
+
+void elfu_mRelocate32(ElfuElf *metarget, ElfuScn *mstarget, ElfuScn *msrt)
+{
+  ElfuRel *rel;
+
+  assert(mstarget);
+  assert(msrt);
+
+  ELFU_DEBUG("Relocating in section of type %d size %jx\n",
+             mstarget->shdr.sh_type,
+             mstarget->shdr.sh_size);
+
+  CIRCLEQ_FOREACH(rel, &msrt->reltab->rels, elem) {
+    Elf32_Word *dest = (Elf32_Word*)(((char*)(mstarget->data.d_buf)) + rel->offset);
+    Elf32_Word a = rel->addendUsed ? rel->addend : *dest;
+    Elf32_Addr p = mstarget->shdr.sh_addr + rel->offset;
+    Elf32_Addr s = symtabLookupVal(metarget, msrt->linkptr, rel->sym);
+    Elf32_Word newval = *dest;
+
+    switch(rel->type) {
+      case R_386_NONE:
+        ELFU_DEBUG("Skipping relocation: R_386_NONE");
+        break;
+      case R_386_32:
+        ELFU_DEBUG("Relocation: R_386_32");
+        newval = s + a;
+        break;
+      case R_386_PC32:
+        ELFU_DEBUG("Relocation: R_386_PC32");
+        newval = s + a - p;
+        break;
+
+      default:
+        ELFU_DEBUG("Skipping relocation: Unknown type %d", rel->type);
+    }
+    ELFU_DEBUG(", overwriting %x with %x.\n", *dest, newval);
+    *dest = newval;
+  }
+}