[JITLink] Fix i686 R_386_32 and other relocation values (#111091)

vtjnash · web-flow · commit 5716f836d25e · 2024-10-16T15:48:43.000+11:00
Fix R_386_32 and other relocations by correcting Addend computations.
diff --git a/llvm/include/llvm/ExecutionEngine/JITLink/i386.h b/llvm/include/llvm/ExecutionEngine/JITLink/i386.h
@@ -39,12 +39,8 @@ enum EdgeKind_i386 : Edge::Kind {
   /// Represents a data/control flow instruction using PC-relative addressing
   /// to a target.
   ///
-  /// The fixup expression for this kind includes an implicit offset to account
-  /// for the PC (unlike the Delta edges) so that a PCRel32 with a target
-  /// T and addend zero is a call/branch to the start (offset zero) of T.
-  ///
   /// Fixup expression:
-  ///   Fixup <- Target - (Fixup + 4) + Addend : int32
+  ///   Fixup <- Target - Fixup + Addend : int32
   ///
   /// Errors:
   ///   - The result of the fixup expression must fit into an int32, otherwise
@@ -68,12 +64,8 @@ enum EdgeKind_i386 : Edge::Kind {
   /// Represents a data/control flow instruction using PC-relative addressing
   /// to a target.
   ///
-  /// The fixup expression for this kind includes an implicit offset to account
-  /// for the PC (unlike the Delta edges) so that a PCRel16 with a target
-  /// T and addend zero is a call/branch to the start (offset zero) of T.
-  ///
   /// Fixup expression:
-  ///   Fixup <- Target - (Fixup + 4) + Addend : int16
+  ///   Fixup <- Target - Fixup + Addend : int16
   ///
   /// Errors:
   ///   - The result of the fixup expression must fit into an int16, otherwise
@@ -86,7 +78,7 @@ enum EdgeKind_i386 : Edge::Kind {
   /// Delta from the fixup to the target.
   ///
   /// Fixup expression:
-  ///   Fixup <- Target - Fixup + Addend : int64
+  ///   Fixup <- Target - Fixup + Addend : int32
   ///
   /// Errors:
   ///   - The result of the fixup expression must fit into an int32, otherwise
@@ -130,12 +122,8 @@ enum EdgeKind_i386 : Edge::Kind {
   /// Represents a PC-relative call or branch to a target. This can be used to
   /// identify, record, and/or patch call sites.
   ///
-  /// The fixup expression for this kind includes an implicit offset to account
-  /// for the PC (unlike the Delta edges) so that a Branch32PCRel with a target
-  /// T and addend zero is a call/branch to the start (offset zero) of T.
-  ///
   /// Fixup expression:
-  ///   Fixup <- Target - (Fixup + 4) + Addend : int32
+  ///   Fixup <- Target - Fixup + Addend : int32
   ///
   /// Errors:
   ///   - The result of the fixup expression must fit into an int32, otherwise
@@ -164,7 +152,7 @@ enum EdgeKind_i386 : Edge::Kind {
   /// target may be recorded to allow manipulation at runtime.
   ///
   /// Fixup expression:
-  ///   Fixup <- Target - Fixup + Addend - 4 : int32
+  ///   Fixup <- Target - Fixup + Addend : int32
   ///
   /// Errors:
   ///   - The result of the fixup expression must fit into an int32, otherwise
@@ -180,7 +168,7 @@ enum EdgeKind_i386 : Edge::Kind {
   /// is within range of the fixup location.
   ///
   /// Fixup expression:
-  ///   Fixup <- Target - Fixup + Addend - 4: int32
+  ///   Fixup <- Target - Fixup + Addend : int32
   ///
   /// Errors:
   ///   - The result of the fixup expression must fit into an int32, otherwise
@@ -215,8 +203,7 @@ inline Error applyFixup(LinkGraph &G, Block &B, const Edge &E,
   }
 
   case i386::PCRel32: {
-    int32_t Value =
-        E.getTarget().getAddress() - (FixupAddress + 4) + E.getAddend();
+    int32_t Value = E.getTarget().getAddress() - FixupAddress + E.getAddend();
     *(little32_t *)FixupPtr = Value;
     break;
   }
@@ -231,8 +218,7 @@ inline Error applyFixup(LinkGraph &G, Block &B, const Edge &E,
   }
 
   case i386::PCRel16: {
-    int32_t Value =
-        E.getTarget().getAddress() - (FixupAddress + 4) + E.getAddend();
+    int32_t Value = E.getTarget().getAddress() - FixupAddress + E.getAddend();
     if (LLVM_LIKELY(isInt<16>(Value)))
       *(little16_t *)FixupPtr = Value;
     else
@@ -257,8 +243,7 @@ inline Error applyFixup(LinkGraph &G, Block &B, const Edge &E,
   case i386::BranchPCRel32:
   case i386::BranchPCRel32ToPtrJumpStub:
   case i386::BranchPCRel32ToPtrJumpStubBypassable: {
-    int32_t Value =
-        E.getTarget().getAddress() - (FixupAddress + 4) + E.getAddend();
+    int32_t Value = E.getTarget().getAddress() - FixupAddress + E.getAddend();
     *(little32_t *)FixupPtr = Value;
     break;
   }
diff --git a/llvm/lib/ExecutionEngine/JITLink/ELF_i386.cpp b/llvm/lib/ExecutionEngine/JITLink/ELF_i386.cpp
@@ -186,15 +186,29 @@ class ELFLinkGraphBuilder_i386 : public ELFLinkGraphBuilder<ELFT> {
     int64_t Addend = 0;
 
     switch (*Kind) {
-    case i386::EdgeKind_i386::Delta32: {
+    case i386::EdgeKind_i386::None:
+      break;
+    case i386::EdgeKind_i386::Pointer32:
+    case i386::EdgeKind_i386::PCRel32:
+    case i386::EdgeKind_i386::RequestGOTAndTransformToDelta32FromGOT:
+    case i386::EdgeKind_i386::Delta32:
+    case i386::EdgeKind_i386::Delta32FromGOT:
+    case i386::EdgeKind_i386::BranchPCRel32:
+    case i386::EdgeKind_i386::BranchPCRel32ToPtrJumpStub:
+    case i386::EdgeKind_i386::BranchPCRel32ToPtrJumpStubBypassable: {
       const char *FixupContent = BlockToFix.getContent().data() +
                                  (FixupAddress - BlockToFix.getAddress());
-      Addend = *(const support::ulittle32_t *)FixupContent;
+      Addend = *(const support::little32_t *)FixupContent;
       break;
     }
-    default:
+    case i386::EdgeKind_i386::Pointer16:
+    case i386::EdgeKind_i386::PCRel16: {
+      const char *FixupContent = BlockToFix.getContent().data() +
+                                 (FixupAddress - BlockToFix.getAddress());
+      Addend = *(const support::little16_t *)FixupContent;
       break;
     }
+    }
 
     Edge::OffsetT Offset = FixupAddress - BlockToFix.getAddress();
     Edge GE(*Kind, Offset, *GraphSymbol, Addend);
diff --git a/llvm/test/ExecutionEngine/JITLink/i386/ELF_i386_absolute_relocations_16.s b/llvm/test/ExecutionEngine/JITLink/i386/ELF_i386_absolute_relocations_16.s
@@ -22,4 +22,12 @@ main:
         .type   bar,@function
 bar:
         retw    $external_data
-        .size   bar, .-bar
+        .size   bar, .-bar
+
+# jitlink-check: decode_operand(baz, 0) = external_data + 23
+        .globl  baz
+        .align        2, 0x90
+        .type   baz,@function
+baz:
+        retw    $external_data+23
+        .size   baz, .-baz
diff --git a/llvm/test/ExecutionEngine/JITLink/i386/ELF_i386_absolute_relocations_32.s b/llvm/test/ExecutionEngine/JITLink/i386/ELF_i386_absolute_relocations_32.s
@@ -7,17 +7,25 @@
 # Test ELF 32 bit absolute relocations
 
         .text
-        .globl  main     
+        .globl  main
         .p2align        4, 0x90
         .type   main,@function
-main:                                   
+main:
         retl
         .size   main, .-main
 
 # jitlink-check: decode_operand(foo, 0) = external_data
-        .globl  foo     
+        .globl  foo
         .p2align        4, 0x90
         .type   foo,@function
 foo:
         movl    external_data, %eax
-        .size   foo, .-foo
+        .size   foo, .-foo
+
+# jitlink-check: decode_operand(bar, 0) = external_data + 4000
+        .globl  bar
+        .p2align        4, 0x90
+        .type   bar,@function
+bar:
+        movl    external_data + 4000, %eax
+        .size   bar, .-bar
diff --git a/llvm/test/ExecutionEngine/JITLink/i386/ELF_i386_pc_relative_relocations_32.s b/llvm/test/ExecutionEngine/JITLink/i386/ELF_i386_pc_relative_relocations_32.s
@@ -33,17 +33,18 @@ foo:
 
 
 # Tests PC relative relocation for negative offset from PC
-# jitlink-check: decode_operand(baz, 0) = fooz - next_pc(baz)
+# jitlink-check: decode_operand(baz, 0) = fooz - next_pc(baz) + 1
         .globl  fooz
         .p2align        4
         .type   fooz,@function
 fooz:
+    nop
     retl
         .size   fooz, .-fooz
 
         .globl  baz
         .p2align        4
         .type   baz,@function
 baz:
-    calll fooz
-        .size       baz, .-baz
+    calll fooz+1
+        .size       baz, .-baz
diff --git a/llvm/test/ExecutionEngine/JITLink/i386/ELF_i386_small_pic_relocations_got.s b/llvm/test/ExecutionEngine/JITLink/i386/ELF_i386_small_pic_relocations_got.s
@@ -19,29 +19,29 @@ main:
 # Test GOT32 handling.
 # 
 # We want to check both the offset to the GOT entry and its contents. 
-# jitlink-check: decode_operand(test_got, 4) = got_addr(elf_sm_pic_reloc_got.o, named_data1) - _GLOBAL_OFFSET_TABLE_
+# jitlink-check: decode_operand(test_got, 4) = got_addr(elf_sm_pic_reloc_got.o, named_data1) - _GLOBAL_OFFSET_TABLE_ + 42
 # jitlink-check: *{4}(got_addr(elf_sm_pic_reloc_got.o, named_data1)) = named_data1
 # 
-# jitlink-check: decode_operand(test_got+6, 4) = got_addr(elf_sm_pic_reloc_got.o, named_data2) - _GLOBAL_OFFSET_TABLE_
+# jitlink-check: decode_operand(test_got+6, 4) = got_addr(elf_sm_pic_reloc_got.o, named_data2) - _GLOBAL_OFFSET_TABLE_ + 5
 # jitlink-check: *{4}(got_addr(elf_sm_pic_reloc_got.o, named_data2)) = named_data2
 
         .globl test_got
         .p2align      4, 0x90
         .type   test_got,@function
 test_got:
-	leal    named_data1@GOT, %eax
-        leal    named_data2@GOT, %eax
+        leal    named_data1@GOT+42, %eax
+        leal    named_data2@GOT+5, %eax
         .size   test_got, .-test_got
 
 
 
 # Test GOTOFF64 handling.
-# jitlink-check: decode_operand(test_gotoff, 1) = named_func - _GLOBAL_OFFSET_TABLE_
+# jitlink-check: decode_operand(test_gotoff, 1) = named_func - _GLOBAL_OFFSET_TABLE_ + 99
         .globl test_gotoff
         .p2align     4, 0x90
         .type  test_gotoff,@function
 test_gotoff:
-        mov $named_func@GOTOFF, %eax
+        mov $named_func@GOTOFF+99, %eax
         .size   test_gotoff, .-test_gotoff
 
 
diff --git a/llvm/test/ExecutionEngine/JITLink/i386/ELF_i386_small_pic_relocations_plt.s b/llvm/test/ExecutionEngine/JITLink/i386/ELF_i386_small_pic_relocations_plt.s
@@ -27,12 +27,12 @@ main:
 # for position independent code, first, as there may be future use-cases
 # where we would want to disable the optimization.
 # 
-# jitlink-check: decode_operand(test_call_extern_plt, 0) = external_func - next_pc(test_call_extern_plt)
+# jitlink-check: decode_operand(test_call_extern_plt, 0) = external_func - next_pc(test_call_extern_plt) + 53
 # jitlink-check: *{4}(got_addr(elf_sm_pic_reloc_plt.o, external_func))= external_func
         .globl  test_call_extern_plt
         .p2align       4, 0x90
         .type   test_call_extern_plt,@function
 test_call_extern_plt:
-        call   external_func@plt
+        call   external_func@plt + 53
 
-        .size   test_call_extern_plt, .-test_call_extern_plt
+        .size   test_call_extern_plt, .-test_call_extern_plt
