[PATCH] D113509: [lld][ELF] Support for R_ARM_THM_JUMP8

[Petr Hosek via Phabricator via llvm-commits]

phosek created this revision.
phosek added reviewers: MaskRay, mcgrathr.
Herald added subscribers: kristof.beyls, arichardson, emaste.
phosek requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

This change implements support for R_ARM_THM_JUMP8 relocation in
addition to R_ARM_THM_JUMP11 which is already supported by LLD.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D113509

Files:
  lld/ELF/Arch/ARM.cpp
  lld/ELF/InputSection.cpp
  lld/test/ELF/arm-thumb-undefined-weak-narrow.test


Index: lld/test/ELF/arm-thumb-undefined-weak-narrow.test
===================================================================
--- lld/test/ELF/arm-thumb-undefined-weak-narrow.test
+++ lld/test/ELF/arm-thumb-undefined-weak-narrow.test
@@ -7,11 +7,12 @@
 # CHECK-EMPTY:
 # CHECK-NEXT: <_start>:
 # CHECK-NEXT:    ff e7   b       0x200b6 <_start+0x2> @ imm = #-2
+# CHECK-NEXT:    ff e7   b       0x200b8 <_start+0x4> @ imm = #-2
 
-# Test the R_ARM_THM_JUMP11 relocation (102) to an undefined weak reference
-# It should resolve to the next instruction, which is an offset of -2 which
-# when added to the Thumb PC-bias of 4 is +2. We can't use llvm-mc to construct
-# the object as it relaxes b.n to b.w (R_ARM_JUMP24).
+# Test the R_ARM_THM_JUMP11 (102) and R_ARM_THM_JUMP8 (103) relocations to an
+# undefined weak reference.  It should resolve to the next instruction, which
+# is an offset of -2 which when added to the Thumb PC-bias of 4 is +2. We can't
+# use llvm-mc to construct the object as it relaxes b.n to b.w (R_ARM_JUMP24).
 
 !ELF
 FileHeader:
@@ -23,7 +24,7 @@
   - Type:            SHT_PROGBITS
     Name:            .text
     Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
-    Content:         "fee7"
+    Content:         "fee7ffe7"
   - Type:            SHT_REL
     Name:            .rel.text
     Link:            .symtab
@@ -31,6 +32,8 @@
     Relocations:
       - Symbol:          undefined_weak
         Type:            R_ARM_THM_JUMP11
+      - Symbol:          undefined_weak
+        Type:            R_ARM_THM_JUMP8
 
 Symbols:
   - Type:             STT_NOTYPE
Index: lld/ELF/InputSection.cpp
===================================================================
--- lld/ELF/InputSection.cpp
+++ lld/ELF/InputSection.cpp
@@ -495,6 +495,7 @@
   switch (type) {
   // Unresolved branch relocations to weak references resolve to next
   // instruction, this will be either 2 or 4 bytes on from P.
+  case R_ARM_THM_JUMP8:
   case R_ARM_THM_JUMP11:
     return p + 2 + a;
   case R_ARM_CALL:
Index: lld/ELF/Arch/ARM.cpp
===================================================================
--- lld/ELF/Arch/ARM.cpp
+++ lld/ELF/Arch/ARM.cpp
@@ -90,6 +90,7 @@
   case R_ARM_THM_MOVW_ABS_NC:
   case R_ARM_THM_MOVT_ABS:
     return R_ABS;
+  case R_ARM_THM_JUMP8:
   case R_ARM_THM_JUMP11:
     return R_PC;
   case R_ARM_CALL:
@@ -520,7 +521,13 @@
     checkInt(loc, val, 26, rel);
     write32le(loc, (read32le(loc) & ~0x00ffffff) | ((val >> 2) & 0x00ffffff));
     break;
+  case R_ARM_THM_JUMP8:
+    // We do a 9 bit check because val is right-shifted by 1 bit.
+    checkInt(loc, val, 9, rel);
+    write16le(loc, (read32le(loc) & 0xff00) | ((val >> 1) & 0x00ff));
+    break;
   case R_ARM_THM_JUMP11:
+    // We do a 12 bit check because val is right-shifted by 1 bit.
     checkInt(loc, val, 12, rel);
     write16le(loc, (read32le(loc) & 0xf800) | ((val >> 1) & 0x07ff));
     break;
@@ -748,6 +755,8 @@
   case R_ARM_PC24:
   case R_ARM_PLT32:
     return SignExtend64<26>(read32le(buf) << 2);
+  case R_ARM_THM_JUMP8:
+    return SignExtend64<9>(read16le(buf) << 1);
   case R_ARM_THM_JUMP11:
     return SignExtend64<12>(read16le(buf) << 1);
   case R_ARM_THM_JUMP19: {


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