BaseTools GenFw: Add support for RISCV GOT/PLT relocations

Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3096

This patch adds support for R_RISCV_CALL_PLT and R_RISCV_GOT_HI20
relocations generated by PIE enabled compiler. This also needed
changes to R_RISCV_32 and R_RISCV_64 relocations as explained in
https://github.com/riscv/riscv-gnu-toolchain/issues/905#issuecomment-846682710

Testing:
1) Debian GCC 8.3.0 and booted sifive_u and QMEU virt models.
2) Debian 10.2.0 and booted QEMU virt model.
3) riscv-gnu-tool chain 9.2 and booted QEMU virt model.

Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>

Acked-by: Abner Chang <abner.chang@hpe.com>
Reviewed-by: Daniel Schaefer <daniel.schaefer@hpe.com>
Tested-by: Daniel Schaefer <daniel.schaefer@hpe.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>

Cc: Bob Feng <bob.c.feng@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Yuwei Chen <yuwei.chen@intel.com>
Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>

BaseTools/Source/C/GenFw/Elf64Convert.c

@@ -129,6 +129,8 @@ STATIC UINT32 mDebugOffset;
 STATIC UINT8       *mRiscVPass1Targ = NULL;
 STATIC Elf_Shdr    *mRiscVPass1Sym = NULL;
 STATIC Elf64_Half  mRiscVPass1SymSecIndex = 0;
+STATIC INT32       mRiscVPass1Offset;
+STATIC INT32       mRiscVPass1GotFixup;
 
 //
 // Initialization Function
@@ -474,17 +476,18 @@ WriteSectionRiscV64 (
 {
   UINT32      Value;
   UINT32      Value2;
+  Elf64_Addr  GOTEntryRva;
 
   switch (ELF_R_TYPE(Rel->r_info)) {
   case R_RISCV_NONE:
     break;
 
   case R_RISCV_32:
-    *(UINT32 *)Targ = (UINT32)((UINT64)(*(UINT32 *)Targ) - SymShdr->sh_addr + mCoffSectionsOffset[Sym->st_shndx]);
+    *(UINT64 *)Targ = Sym->st_value + Rel->r_addend;
     break;
 
   case R_RISCV_64:
-    *(UINT64 *)Targ = *(UINT64 *)Targ - SymShdr->sh_addr + mCoffSectionsOffset[Sym->st_shndx];
+    *(UINT64 *)Targ = Sym->st_value + Rel->r_addend;
     break;
 
   case R_RISCV_HI20:
@@ -534,6 +537,18 @@ WriteSectionRiscV64 (
     mRiscVPass1SymSecIndex = 0;
     break;
 
+  case R_RISCV_GOT_HI20:
+    GOTEntryRva = (Sym->st_value - Rel->r_offset);
+    mRiscVPass1Offset = RV_X(GOTEntryRva, 0, 12);
+    Value = (UINT32)RV_X(GOTEntryRva, 12, 20);
+    *(UINT32 *)Targ = (Value << 12) | (RV_X(*(UINT32*)Targ, 0, 12));
+
+    mRiscVPass1Targ = Targ;
+    mRiscVPass1Sym = SymShdr;
+    mRiscVPass1SymSecIndex = Sym->st_shndx;
+    mRiscVPass1GotFixup = 1;
+    break;
+
   case R_RISCV_PCREL_HI20:
     mRiscVPass1Targ = Targ;
     mRiscVPass1Sym = SymShdr;
@@ -546,11 +561,17 @@ WriteSectionRiscV64 (
     if (mRiscVPass1Targ != NULL && mRiscVPass1Sym != NULL && mRiscVPass1SymSecIndex != 0) {
       int i;
       Value2 = (UINT32)(RV_X(*(UINT32 *)mRiscVPass1Targ, 12, 20));
-      Value = (UINT32)(RV_X(*(UINT32 *)Targ, 20, 12));
+
-      if(Value & (RISCV_IMM_REACH/2)) {
+      if(mRiscVPass1GotFixup) {
-        Value |= ~(RISCV_IMM_REACH-1);
+        Value = (UINT32)(mRiscVPass1Offset);
+      } else {
+        Value = (UINT32)(RV_X(*(UINT32 *)Targ, 20, 12));
+        if(Value & (RISCV_IMM_REACH/2)) {
+          Value |= ~(RISCV_IMM_REACH-1);
+        }
       }
       Value = Value - (UINT32)mRiscVPass1Sym->sh_addr + mCoffSectionsOffset[mRiscVPass1SymSecIndex];
+
       if(-2048 > (INT32)Value) {
         i = (((INT32)Value * -1) / 4096);
         Value2 -= i;
@@ -570,12 +591,35 @@ WriteSectionRiscV64 (
         }
       }
 
-      *(UINT32 *)Targ = (RV_X(Value, 0, 12) << 20) | (RV_X(*(UINT32*)Targ, 0, 20));
+      if(mRiscVPass1GotFixup) {
+        *(UINT32 *)Targ = (RV_X((UINT32)Value, 0, 12) << 20)
+                            | (RV_X(*(UINT32*)Targ, 0, 20));
+        // Convert LD instruction to ADDI
+        //
+        // |31      20|19  15|14  12|11   7|6       0|
+        // |-----------------------------------------|
+        // |imm[11:0] | rs1  | 011  |  rd  | 0000011 | LD
+        //  -----------------------------------------
+
+        // |-----------------------------------------|
+        // |imm[11:0] | rs1  | 000  |  rd  | 0010011 | ADDI
+        //  -----------------------------------------
+
+        // To convert, let's first reset bits 12-14 and 0-6 using ~0x707f
+        // Then modify the opcode to ADDI (0010011)
+        // All other fields will remain same.
+
+        *(UINT32 *)Targ = ((*(UINT32 *)Targ & ~0x707f) | 0x13);
+      } else {
+        *(UINT32 *)Targ = (RV_X(Value, 0, 12) << 20) | (RV_X(*(UINT32*)Targ, 0, 20));
+      }
       *(UINT32 *)mRiscVPass1Targ = (RV_X(Value2, 0, 20)<<12) | (RV_X(*(UINT32 *)mRiscVPass1Targ, 0, 12));
     }
     mRiscVPass1Sym = NULL;
     mRiscVPass1Targ = NULL;
     mRiscVPass1SymSecIndex = 0;
+    mRiscVPass1Offset = 0;
+    mRiscVPass1GotFixup = 0;
     break;
 
   case R_RISCV_ADD64:
@@ -587,6 +631,7 @@ WriteSectionRiscV64 (
   case R_RISCV_GPREL_I:
   case R_RISCV_GPREL_S:
   case R_RISCV_CALL:
+  case R_RISCV_CALL_PLT:
   case R_RISCV_RVC_BRANCH:
   case R_RISCV_RVC_JUMP:
   case R_RISCV_RELAX:
@@ -1530,6 +1575,7 @@ WriteRelocations64 (
             case R_RISCV_GPREL_I:
             case R_RISCV_GPREL_S:
             case R_RISCV_CALL:
+            case R_RISCV_CALL_PLT:
             case R_RISCV_RVC_BRANCH:
             case R_RISCV_RVC_JUMP:
             case R_RISCV_RELAX:
@@ -1539,6 +1585,7 @@ WriteRelocations64 (
             case R_RISCV_SET16:
             case R_RISCV_SET32:
             case R_RISCV_PCREL_HI20:
+            case R_RISCV_GOT_HI20:
             case R_RISCV_PCREL_LO12_I:
               break;