[lld] 82b3da6 - [lld-macho] Extract embedded addends for arm64 UNSIGNED relocations

[Jez Ng via llvm-commits]

Author: Jez Ng
Date: 2021-02-27T12:31:34-05:00
New Revision: 82b3da6f6f0e91e47074f454907e82b284b8beda

URL: https://github.com/llvm/llvm-project/commit/82b3da6f6f0e91e47074f454907e82b284b8beda
DIFF: https://github.com/llvm/llvm-project/commit/82b3da6f6f0e91e47074f454907e82b284b8beda.diff

LOG: [lld-macho] Extract embedded addends for arm64 UNSIGNED relocations

On arm64, UNSIGNED relocs are the only ones that use embedded addends
instead of the ADDEND relocation.

Also ensure that the addend works when UNSIGNED is part of a SUBTRACTOR
pair.

Reviewed By: #lld-macho, alexshap

Differential Revision: https://reviews.llvm.org/D97105

Added: 
    

Modified: 
    lld/MachO/Arch/ARM64.cpp
    lld/MachO/InputFiles.cpp
    lld/test/MachO/arm64-relocs.s
    lld/test/MachO/reloc-subtractor.s

Removed: 
    


################################################################################
diff  --git a/lld/MachO/Arch/ARM64.cpp b/lld/MachO/Arch/ARM64.cpp
index 8428ef480b03..18139503877e 100644
--- a/lld/MachO/Arch/ARM64.cpp
+++ b/lld/MachO/Arch/ARM64.cpp
@@ -79,8 +79,23 @@ const TargetInfo::RelocAttrs &ARM64::getRelocAttrs(uint8_t type) const {
 
 uint64_t ARM64::getEmbeddedAddend(MemoryBufferRef mb, const section_64 &sec,
                                   const relocation_info rel) const {
-  // TODO(gkm): extract embedded addend just so we can assert that it is 0
-  return 0;
+  if (rel.r_type != ARM64_RELOC_UNSIGNED) {
+    // All other reloc types should use the ADDEND relocation to store their
+    // addends.
+    // TODO(gkm): extract embedded addend just so we can assert that it is 0
+    return 0;
+  }
+
+  auto *buf = reinterpret_cast<const uint8_t *>(mb.getBufferStart());
+  const uint8_t *loc = buf + sec.offset + rel.r_address;
+  switch (rel.r_length) {
+  case 2:
+    return read32le(loc);
+  case 3:
+    return read64le(loc);
+  default:
+    llvm_unreachable("invalid r_length");
+  }
 }
 
 inline uint64_t bitField(uint64_t value, int right, int width, int left) {

diff  --git a/lld/MachO/InputFiles.cpp b/lld/MachO/InputFiles.cpp
index 92030222a589..57126117c30c 100644
--- a/lld/MachO/InputFiles.cpp
+++ b/lld/MachO/InputFiles.cpp
@@ -278,9 +278,6 @@ void ObjFile::parseRelocations(const section_64 &sec,
       continue;
     if (relInfo.r_address & R_SCATTERED)
       fatal("TODO: Scattered relocations not supported");
-    uint64_t embeddedAddend = target->getEmbeddedAddend(mb, sec, relInfo);
-    assert(!(embeddedAddend && pairedAddend));
-    uint64_t totalAddend = pairedAddend + embeddedAddend;
 
     Reloc p;
     if (target->hasAttr(relInfo.r_type, RelocAttrBits::SUBTRAHEND)) {
@@ -292,6 +289,9 @@ void ObjFile::parseRelocations(const section_64 &sec,
       assert(target->hasAttr(relInfo.r_type, RelocAttrBits::UNSIGNED) &&
              relInfo.r_extern);
     }
+    uint64_t embeddedAddend = target->getEmbeddedAddend(mb, sec, relInfo);
+    assert(!(embeddedAddend && pairedAddend));
+    uint64_t totalAddend = pairedAddend + embeddedAddend;
     Reloc r;
     r.type = relInfo.r_type;
     r.pcrel = relInfo.r_pcrel;

diff  --git a/lld/test/MachO/arm64-relocs.s b/lld/test/MachO/arm64-relocs.s
index 0f3dd87ef113..1ce5e10bd0be 100644
--- a/lld/test/MachO/arm64-relocs.s
+++ b/lld/test/MachO/arm64-relocs.s
@@ -18,8 +18,8 @@
 # CHECK-NEXT:  ret
 
 # CHECK-LABEL: Contents of (__DATA_CONST,__const) section
-# CHECK:       [[#PTR_1]]	{{0*}}[[#BAZ]] 00000000 00000000 00000000
-# CHECK:       [[#PTR_2]]	{{0*}}[[#BAZ]] 00000000 00000000 00000000
+# CHECK:       [[#PTR_1]]	{{0*}}[[#BAZ]]     00000000 00000000 00000000
+# CHECK:       [[#PTR_2]]	{{0*}}[[#BAZ+123]] 00000000 00000000 00000000
 
 .text
 .globl _foo, _bar, _baz
@@ -50,7 +50,7 @@ _ptr_1:
   .quad _baz
   .space 8
 _ptr_2:
-  .quad _baz
+  .quad _baz + 123
   .space 8
 
 .subsections_via_symbols

diff  --git a/lld/test/MachO/reloc-subtractor.s b/lld/test/MachO/reloc-subtractor.s
index e445184e44b1..dead12f06766 100644
--- a/lld/test/MachO/reloc-subtractor.s
+++ b/lld/test/MachO/reloc-subtractor.s
@@ -14,9 +14,9 @@
 # CHECK:       {{0*}}[[#%x, SUB4ADDR:]] l {{.*}} __DATA,__data _sub4
 # CHECK-LABEL: Contents of section __DATA,__data:
 # CHECK:       [[#SUB1ADDR]] 10000000
-# CHECK-NEXT:  [[#SUB2ADDR]] f0ffffff
-# CHECK-NEXT:  [[#SUB3ADDR]] 10000000 00000000
-# CHECK-NEXT:  [[#SUB4ADDR]] f0ffffff ffffffff
+# CHECK-NEXT:  [[#SUB2ADDR]] f2ffffff
+# CHECK-NEXT:  [[#SUB3ADDR]] 14000000 00000000
+# CHECK-NEXT:  [[#SUB4ADDR]] f6ffffff ffffffff
 # CHECK:       Rebase table:
 # CHECK-NEXT:  segment  section            address     type
 # CHECK-EMPTY:
@@ -36,13 +36,13 @@ _sub1:
   .long _minuend_1 - _subtrahend_1
   .space 12
 _sub2:
-  .long _minuend_2 - _subtrahend_2
+  .long _minuend_2 - _subtrahend_2 + 2
   .space 12
 _sub3:
-  .quad _minuend_1 - _subtrahend_1
+  .quad _minuend_1 - _subtrahend_1 + 4
   .space 8
 _sub4:
-  .quad _minuend_2 - _subtrahend_2
+  .quad _minuend_2 - _subtrahend_2 + 6
 
 .text
 .p2align 2