[PATCH] D60414: [RISCV] Fix range check for HI20/LO12/RVC_LUI relocations

[Chih-Mao Chen via Phabricator via llvm-commits]

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The code previously specified a 32-bit range for `R_RISCV_HI20` and `R_RISCV_LO12_[IS]`, however this is incorrect as the maximum offset on RV64 that can be formed from the immediate of `lui` and the displacement of an I-type or S-type instruction is `-0x80000800` to `0x7ffff7ff`. There is also the same issue with a `c.lui` and LO12 pair, whose actual addressable range should be `-0x20800` to `0x1f7ff`.

The tests will be included in the next patch that converts all RISC-V tests to use `llvm-mc` instead of `yaml2obj`, as assembler support has matured enough to write tests in them.


Repository:
  rLLD LLVM Linker

https://reviews.llvm.org/D60414

Files:
  ELF/Arch/RISCV.cpp


Index: ELF/Arch/RISCV.cpp
===================================================================
--- ELF/Arch/RISCV.cpp
+++ ELF/Arch/RISCV.cpp
@@ -88,6 +88,8 @@
 
 void RISCV::relocateOne(uint8_t *Loc, const RelType Type,
                         const uint64_t Val) const {
+  const unsigned Bits = Config->Wordsize * 8;
+
   switch (Type) {
   case R_RISCV_32:
     write32le(Loc, Val);
@@ -130,8 +132,8 @@
   }
 
   case R_RISCV_RVC_LUI: {
-    int32_t Imm = ((Val + 0x800) >> 12);
-    checkUInt(Loc, Imm, 6, Type);
+    int64_t Imm = SignExtend64(Val + 0x800, Bits) >> 12;
+    checkInt(Loc, Imm, 6, Type);
     if (Imm == 0) { // `c.lui rd, 0` is illegal, convert to `c.li rd, 0`
       write16le(Loc, (read16le(Loc) & 0x0F83) | 0x4000);
     } else {
@@ -174,8 +176,9 @@
 
   // auipc + jalr pair
   case R_RISCV_CALL: {
-    checkInt(Loc, Val, 32, Type);
-    if (isInt<32>(Val)) {
+    int64_t Hi = SignExtend64(Val + 0x800, Bits) >> 12;
+    checkInt(Loc, Hi, 20, Type);
+    if (isInt<20>(Hi)) {
       relocateOne(Loc, R_RISCV_PCREL_HI20, Val);
       relocateOne(Loc + 4, R_RISCV_PCREL_LO12_I, Val);
     }
@@ -184,26 +187,24 @@
 
   case R_RISCV_PCREL_HI20:
   case R_RISCV_HI20: {
-    checkInt(Loc, Val, 32, Type);
-    uint32_t Hi = Val + 0x800;
+    uint64_t Hi = Val + 0x800;
+    checkInt(Loc, SignExtend64(Hi, Bits) >> 12, 20, Type);
     write32le(Loc, (read32le(Loc) & 0xFFF) | (Hi & 0xFFFFF000));
     return;
   }
 
   case R_RISCV_PCREL_LO12_I:
   case R_RISCV_LO12_I: {
-    checkInt(Loc, Val, 32, Type);
-    uint32_t Hi = Val + 0x800;
-    uint32_t Lo = Val - (Hi & 0xFFFFF000);
+    uint64_t Hi = (Val + 0x800) >> 12;
+    uint64_t Lo = Val - (Hi << 12);
     write32le(Loc, (read32le(Loc) & 0xFFFFF) | ((Lo & 0xFFF) << 20));
     return;
   }
 
   case R_RISCV_PCREL_LO12_S:
   case R_RISCV_LO12_S: {
-    checkInt(Loc, Val, 32, Type);
-    uint32_t Hi = Val + 0x800;
-    uint32_t Lo = Val - (Hi & 0xFFFFF000);
+    uint64_t Hi = (Val + 0x800) >> 12;
+    uint64_t Lo = Val - (Hi << 12);
     uint32_t Imm11_5 = extractBits(Lo, 11, 5) << 25;
     uint32_t Imm4_0 = extractBits(Lo, 4, 0) << 7;
     write32le(Loc, (read32le(Loc) & 0x1FFF07F) | Imm11_5 | Imm4_0);


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