[ELF] Fix DT_MIPS_LOCAL_GOTNO value for thunks and linker scripts

jh7370 · jh7370 · commit f70c5beb228e · 2017-11-22T12:04:21.000Z
The MIPS GOT section has a number of local entries based on the number of pages needed for output sections referenced by GOT page relocations. The number is recorded in the DT_MIPS_LOCAL_GOTNO dynamic section tag. However, the dynamic tag is added before assignAddresses has been called, meaning that any section size used to calculate the value will not include size modifications caused by, for example, linker scripts and thunks. This change moves the calculation of DT_MIPS_LOCAL_GOTNO until writeTo, by which time the output section sizes have been finalized. Reviewers: ruiu, rafael Differential Revision: https://reviews.llvm.org/D39493 llvm-svn: 318828
diff --git a/lld/ELF/SyntheticSections.cpp b/lld/ELF/SyntheticSections.cpp
@@ -1127,7 +1127,11 @@ template <class ELFT> void DynamicSection<ELFT>::finalizeContents() {
     add({DT_MIPS_FLAGS, RHF_NOTPOT});
     add({DT_MIPS_BASE_ADDRESS, Target->getImageBase()});
     add({DT_MIPS_SYMTABNO, InX::DynSymTab->getNumSymbols()});
-    add({DT_MIPS_LOCAL_GOTNO, InX::MipsGot->getLocalEntriesNum()});
+
+    // The number of local GOT entries has not yet been finalized. This value
+    // will be set in writeTo().
+    add({DT_MIPS_LOCAL_GOTNO, uint64_t(0)});
+
     if (const Symbol *B = InX::MipsGot->getFirstGlobalEntry())
       add({DT_MIPS_GOTSYM, B->DynsymIndex});
     else
@@ -1162,7 +1166,10 @@ template <class ELFT> void DynamicSection<ELFT>::writeTo(uint8_t *Buf) {
       P->d_un.d_ptr = E.Sym->getVA();
       break;
     case Entry::PlainInt:
-      P->d_un.d_val = E.Val;
+      if (Config->EMachine == EM_MIPS && E.Tag == DT_MIPS_LOCAL_GOTNO)
+        P->d_un.d_val = InX::MipsGot->getLocalEntriesNum();
+      else
+        P->d_un.d_val = E.Val;
       break;
     }
     ++P;
diff --git a/lld/test/ELF/mips-got-script.s b/lld/test/ELF/mips-got-script.s
@@ -0,0 +1,47 @@
+# Check number of got entries is adjusted for linker script-added space.
+
+# RUN: llvm-mc -filetype=obj -triple=mips-unknown-linux %s -o %t.o
+# RUN: echo "SECTIONS { .data : { *(.data.1); . += 0x10000; *(.data.2) } }" > %t.script
+# RUN: ld.lld %t.o -shared -o %t.so -T %t.script
+# RUN: llvm-readobj -mips-plt-got -dynamic-table %t.so | FileCheck %s
+
+# REQUIRES: mips
+
+# CHECK: 0x7000000A MIPS_LOCAL_GOTNO 5
+#                                    ^-- 2 * header + 3 local entries
+# CHECK:      Local entries [
+# CHECK-NEXT:   Entry {
+# CHECK-NEXT:     Address:
+# CHECK-NEXT:     Access: -32744
+# CHECK-NEXT:     Initial: 0x0
+#                          ^-- loc1
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Entry {
+# CHECK-NEXT:     Address:
+# CHECK-NEXT:     Access: -32740
+# CHECK-NEXT:     Initial: 0x10000
+#                          ^-- loc2
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Entry {
+# CHECK-NEXT:     Address:
+# CHECK-NEXT:     Access: -32736
+# CHECK-NEXT:     Initial: 0x20000
+#                          ^-- redundant
+# CHECK-NEXT:   }
+# CHECK-NEXT: ]
+
+  .text
+  .globl  foo
+foo:
+  lw      $t0, %got(loc1)($gp)
+  addi    $t0, $t0, %lo(loc1)
+  lw      $t0, %got(loc2)($gp)
+  addi    $t0, $t0, %lo(loc2)
+
+  .section .data.1,"aw",%progbits
+loc1:
+  .word 0
+
+  .section .data.2,"aw",%progbits
+loc2:
+  .word 0
