linker: Fix ARM_R_COPY relocations

Per http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf
Section 4.7.1.10, ARM_R_COPY relocations are only suppose to reference shared
libraries, not the executable itself.  When resolving an R_ARM_COPY symbol,
ensure we don't look in our own symbol.

This partially addresses
http://code.google.com/p/android/issues/detail?id=28598 .  After this
patch, the printfs generated by the test program are:

global = 0x42 (0x401c7000)
global = 0x42 (0x11000)

before, the output was:

global = 0x42 (0x40071000)
global = 0x0 (0x11000)

I'm still not very happy with this patch, but I think it's an improvement
over where we were at before.

This change was modeled after https://android-review.googlesource.com/38871

Change-Id: Id7ad921e58395e76a36875bcc742ec5eeba53f08

linker/linker.cpp

@@ -434,13 +434,14 @@ static unsigned elfhash(const char *_name)
 
 static Elf32_Sym *
 soinfo_do_lookup(soinfo *si, const char *name, Elf32_Addr *offset,
-                 soinfo *needed[])
+                 soinfo *needed[], bool ignore_local)
 {
     unsigned elf_hash = elfhash(name);
-    Elf32_Sym *s;
+    Elf32_Sym *s = NULL;
     soinfo *lsi = si;
     int i;
 
+    if (!ignore_local) {
         /* Look for symbols in the local scope (the object who is
          * searching). This happens with C++ templates on i386 for some
          * reason.
@@ -454,6 +455,7 @@ soinfo_do_lookup(soinfo *si, const char *name, Elf32_Addr *offset,
         s = soinfo_elf_lookup(si, elf_hash, name);
         if(s != NULL)
             goto done;
+    }
 
     /* Next, look for it in the preloads list */
     for(i = 0; preloads[i] != NULL; i++) {
@@ -684,6 +686,7 @@ verify_elf_header(const Elf32_Ehdr* hdr)
     if (hdr->e_ident[EI_MAG1] != ELFMAG1) return -1;
     if (hdr->e_ident[EI_MAG2] != ELFMAG2) return -1;
     if (hdr->e_ident[EI_MAG3] != ELFMAG3) return -1;
+    if (hdr->e_type != ET_DYN) return -1;
 
     /* TODO: Should we verify anything else in the header? */
 #ifdef ANDROID_ARM_LINKER
@@ -959,7 +962,11 @@ static int soinfo_relocate(soinfo *si, Elf32_Rel *rel, unsigned count,
         }
         if(sym != 0) {
             sym_name = (char *)(strtab + symtab[sym].st_name);
-            s = soinfo_do_lookup(si, sym_name, &offset, needed);
+            bool ignore_local = false;
+#if defined(ANDROID_ARM_LINKER)
+            ignore_local = (type == R_ARM_COPY);
+#endif
+            s = soinfo_do_lookup(si, sym_name, &offset, needed, ignore_local);
             if(s == NULL) {
                 /* We only allow an undefined symbol if this is a weak
                    reference..   */
@@ -1139,10 +1146,29 @@ static int soinfo_relocate(soinfo *si, Elf32_Rel *rel, unsigned count,
 
 #ifdef ANDROID_ARM_LINKER
         case R_ARM_COPY:
+            if ((si->flags & FLAG_EXE) == 0) {
+                /*
+                 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf
+                 *
+                 * Section 4.7.1.10 "Dynamic relocations"
+                 * R_ARM_COPY may only appear in executable objects where e_type is
+                 * set to ET_EXEC.
+                 *
+                 * TODO: FLAG_EXE is set for both ET_DYN and ET_EXEC executables.
+                 * We should explicitly disallow ET_DYN executables from having
+                 * R_ARM_COPY relocations.
+                 */
+                DL_ERR("%s R_ARM_COPY relocations only supported for ET_EXEC", si->name);
+                return -1;
+            }
             count_relocation(kRelocCopy);
             MARK(rel->r_offset);
             TRACE_TYPE(RELO, "%5d RELO %08x <- %d @ %08x %s\n", pid,
                        reloc, s->st_size, sym_addr, sym_name);
+            if (reloc == sym_addr) {
+                DL_ERR("Internal linker error detected. reloc == symaddr");
+                return -1;
+            }
             memcpy((void*)reloc, (void*)sym_addr, s->st_size);
             break;
 #endif /* ANDROID_ARM_LINKER */
@@ -1201,7 +1227,7 @@ static int mips_relocate_got(soinfo* si, soinfo* needed[]) {
 
         /* This is an undefined reference... try to locate it */
         sym_name = si->strtab + sym->st_name;
-        s = soinfo_do_lookup(si, sym_name, &base, needed);
+        s = soinfo_do_lookup(si, sym_name, &base, needed, false);
         if (s == NULL) {
             /* We only allow an undefined symbol if this is a weak
                reference..   */