Added support for relocations R_RISCV_JAL and R_RISCV_RVC_JUMP

coldav · Jul 26, 2024 · 8a40116 · 8a40116
1 parent acb9c17
commit 8a40116
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diff --git a/modules/loader/include/loader/relocation_types.h b/modules/loader/include/loader/relocation_types.h
@@ -472,6 +472,7 @@ enum Type : uint32_t {
   R_RISCV_NONE = 0,
   R_RISCV_64 = 2,
   R_RISCV_BRANCH = 16,
+  R_RISCV_JAL = 17,
   R_RISCV_CALL = 18,
   R_RISCV_CALL_PLT = 19,
   R_RISCV_PCREL_HI20 = 23,
@@ -482,6 +483,7 @@ enum Type : uint32_t {
   R_RISCV_ADD32 = 35,
   R_RISCV_SUB32 = 39,
   R_RISCV_ALIGN = 43,
+  R_RISCV_RVC_BRANCH = 44,
   R_RISCV_RVC_JUMP = 45,
 };
 }  // namespace RISCV

diff --git a/modules/loader/source/relocations.cpp b/modules/loader/source/relocations.cpp
@@ -878,6 +878,39 @@ bool resolveRISCV(const loader::Relocation &r, loader::ElfMap &map,
       break;
     }
 
+    case R_RISCV_JAL: {
+      // R_RISCV_JAL immediate is for J-Type instructions and is split
+      // across 20 bits spread across the instruction and skips the bottom bit
+      // of the input relative offset. See conditional branches in the isa spec.
+
+      // Check that the value, when sign-extended back up to a 64-bit number
+      // will not lose bits.
+      if (signExtendN(relative_value, 21) !=
+          static_cast<int64_t>(relative_value & (~1))) {
+#ifndef NDEBUG
+        auto name =
+            map.getSymbolName(r.symbol_index).value_or("<unknown symbol>");
+        (void)fprintf(stderr,
+                      "Error: relocation R_RISCV_BRANCH branch > 13 bits or "
+                      "not even for symbol '%.*s'\n",
+                      (int)name.size(), name.data());
+#endif
+        return false;
+      }
+      uint32_t value;
+      const uint32_t trunc_value = static_cast<uint32_t>(relative_value);
+      cargo::read_little_endian(&value, relocation_address);
+      // imm bits 1-10 at bit 21
+      value = setBitRange(value, trunc_value >> 1, 21, 30);
+      // imm bit 11 at bit 22
+      value = setBitRange(value, trunc_value >> 11, 22, 22);
+      // imm bits 12-19 at bit 12
+      value = setBitRange(value, trunc_value >> 12, 12, 19);
+      // imm bit 20 at bit 31
+      value = setBitRange(value, trunc_value >> 20, 31, 31);
+      cargo::write_little_endian(value, relocation_address);
+      break;
+    }
     case R_RISCV_RVC_JUMP: {
       // R_RISCV_RVC_JUMP is for compressed instructions and fits in bits 2-12
       // of a 16 bit value and skips the bottom bit of the input. See CJ format
@@ -905,6 +938,34 @@ bool resolveRISCV(const loader::Relocation &r, loader::ElfMap &map,
       cargo::write_little_endian(value, relocation_address);
       break;
     }
+    case R_RISCV_RVC_BRANCH: {
+      // R_RISCV_RVC_BRANCH is for compressed instructions and fits in bits 2-6
+      // (low) and 10-12 of a 16 bit value and skips the bottom bit of the
+      // input, requiring a total of 8 bits. See CB format in the isa spec.
+
+      // Check that the value, when sign-extended back up to a 64-bit number
+      // will not lose bits.
+      if (signExtendN(relative_value, 9) !=
+          static_cast<int64_t>(relative_value & (~1))) {
+#ifndef NDEBUG
+        auto name =
+            map.getSymbolName(r.symbol_index).value_or("<unknown symbol>");
+        (void)fprintf(stderr,
+                      "Error: relocation R_RISCV_RVC_JUMP > 12 bits or not "
+                      "even for symbol '%.*s'\n",
+                      (int)name.size(), name.data());
+#endif
+        return false;
+      }
+
+      uint16_t value;
+      cargo::read_little_endian(&value, relocation_address);
+      const uint16_t offset_16 = static_cast<uint16_t>(relative_value) >> 1;
+      value = setBitRange(value, getBitRange(offset_16, 0, 4), 1, 6);
+      value = setBitRange(value, getBitRange(offset_16, 5, 7), 10, 12);
+      cargo::write_little_endian(value, relocation_address);
+      break;
+    }
 
     case R_RISCV_ADD32: {
       // 32-bit label addition: V + S + A