diff --git a/lld/MachO/InputFiles.cpp b/lld/MachO/InputFiles.cpp
--- a/lld/MachO/InputFiles.cpp
+++ b/lld/MachO/InputFiles.cpp
@@ -134,6 +134,7 @@
   for (const section_64 &sec : sections) {
     InputSection *isec = make<InputSection>();
     isec->file = this;
+    isec->header = &sec;
     isec->name = StringRef(sec.sectname, strnlen(sec.sectname, 16));
     isec->segname = StringRef(sec.segname, strnlen(sec.segname, 16));
     isec->data = {buf + sec.offset, static_cast<size_t>(sec.size)};
@@ -165,11 +166,13 @@
       r.type = rel.r_type;
       r.offset = rel.r_address;
       r.addend = target->getImplicitAddend(buf + sec.offset + r.offset, r.type);
-      if (rel.r_extern)
+      if (rel.r_extern) {
         r.target = symbols[rel.r_symbolnum];
-      else {
-        error("TODO: Non-extern relocations are not supported");
-        continue;
+      } else {
+        uint32_t sectIdx = rel.r_symbolnum - 1;
+        if (sectIdx >= sections.size())
+          fatal("Relocation section index is greater than number of sections");
+        r.target = sections[sectIdx];
       }
     }
     relocs.push_back(r);
diff --git a/lld/MachO/InputSection.h b/lld/MachO/InputSection.h
--- a/lld/MachO/InputSection.h
+++ b/lld/MachO/InputSection.h
@@ -46,6 +46,8 @@
   StringRef name;
   StringRef segname;
 
+  // This provides access to the address of the section in the input file.
+  const llvm::MachO::section_64 *header;
   ArrayRef<uint8_t> data;
 
   // TODO these properties ought to live in an OutputSection class.
diff --git a/lld/MachO/InputSection.cpp b/lld/MachO/InputSection.cpp
--- a/lld/MachO/InputSection.cpp
+++ b/lld/MachO/InputSection.cpp
@@ -30,6 +30,7 @@
 
   for (Reloc &r : relocs) {
     uint64_t va = 0;
+    uint64_t addend = r.addend;
     if (auto *s = r.target.dyn_cast<Symbol *>()) {
       if (auto *dylibSymbol = dyn_cast<DylibSymbol>(s)) {
         va = target->getDylibSymbolVA(*dylibSymbol, r.type);
@@ -38,11 +39,14 @@
       }
     } else if (auto *isec = r.target.dyn_cast<InputSection *>()) {
       va = isec->addr;
-    } else {
-      llvm_unreachable("Unknown relocation target");
+      // The implicit addend for pcrel section relocations is the pcrel offset
+      // in terms of the addresses in the input file. Here we adjust it so that
+      // it describes the offset from the start of the relocated section.
+      // TODO: Figure out what to do for non-pcrel section relocations.
+      addend -= isec->header->addr - (r.offset + 4);
     }
 
-    uint64_t val = va + r.addend;
+    uint64_t val = va + addend;
     if (1) // TODO: handle non-pcrel relocations
       val -= addr + r.offset;
     target->relocateOne(buf + r.offset, r.type, val);
diff --git a/lld/test/MachO/relocations.s b/lld/test/MachO/relocations.s
--- a/lld/test/MachO/relocations.s
+++ b/lld/test/MachO/relocations.s
@@ -12,9 +12,12 @@
 # CHECK-LABEL: <_main>:
 ## Test X86_64_RELOC_BRANCH
 # CHECK:       callq 0x[[#%x, F_ADDR]] <_f>
-## Test X86_64_RELOC_SIGNED
+## Test extern (symbol) X86_64_RELOC_SIGNED
 # CHECK:       leaq [[#%u, STR_OFF:]](%rip), %rsi
 # CHECK-NEXT:  [[#%x, CSTRING_ADDR - STR_OFF]]
+## Test non-extern (section) X86_64_RELOC_SIGNED
+# CHECK:       leaq [[#%u, LSTR_OFF:]](%rip), %rsi
+# CHECK-NEXT:  [[#%x, CSTRING_ADDR + 22 - LSTR_OFF]]
 
 .section __TEXT,__text
 .globl _main, _f
@@ -26,11 +29,21 @@
 _f:
   movl $0x2000004, %eax # write() syscall
   mov $1, %rdi # stdout
-  leaq str(%rip), %rsi
-  mov $13, %rdx # length of str
+  leaq _str(%rip), %rsi
+  mov $21, %rdx # length of str
+  syscall
+
+  movl $0x2000004, %eax # write() syscall
+  mov $1, %rdi # stdout
+  leaq L_.str(%rip), %rsi
+  mov $15, %rdx # length of str
   syscall
   ret
 
 .section __TEXT,__cstring
-str:
-  .asciz "Hello world!\n"
+## References to this generate a symbol relocation
+_str:
+  .asciz "Local defined symbol\n"
+## References to this generate a section relocation
+L_.str:
+  .asciz "Private symbol\n"