Re: [PATCH] Add support for RISCV GOT/PLT relocations


Daniel Schaefer
 

+Maintainers and Reviewers of BaseTools

See my reply below.

On 5/27/21 10:41 PM, Sunil V L wrote:
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.
Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
Cc: Abner Chang <abner.chang@hpe.com>
Cc: Daniel Schaefer <daniel.schaefer@hpe.com>
Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
---
BaseTools/Source/C/GenFw/Elf64Convert.c | 45 +++++++++++++++++++++----
1 file changed, 39 insertions(+), 6 deletions(-)
diff --git a/BaseTools/Source/C/GenFw/Elf64Convert.c b/BaseTools/Source/C/GenFw/Elf64Convert.c
index d097db8632..d05dcf9992 100644
--- a/BaseTools/Source/C/GenFw/Elf64Convert.c
+++ b/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
@@ -479,11 +481,11 @@ WriteSectionRiscV64 (
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:
@@ -533,6 +535,18 @@ WriteSectionRiscV64 (
mRiscVPass1SymSecIndex = 0;
break;
+ case R_RISCV_GOT_HI20:
+ Value = (Sym->st_value - Rel->r_offset);
+ mRiscVPass1Offset = RV_X(Value, 0, 12);
+ Value = RV_X(Value, 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;
@@ -545,11 +559,17 @@ 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)) {
- Value |= ~(RISCV_IMM_REACH-1);
+
+ if(mRiscVPass1GotFixup) {
+ 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;
@@ -569,12 +589,22 @@ 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 */
+ *(UINT32 *)Targ = ((*(UINT32 *)Targ & ~0x707f) | 0x13);
+ }
+ else {
else should be on the line before, like } 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:
@@ -586,6 +616,7 @@ 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:
@@ -1528,6 +1559,7 @@ 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:
@@ -1537,6 +1569,7 @@ 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;
Just one minor nit-pick on the formatting.
Well in my email program the indentation is off, it looks fine on GitHub though. Probably an issue with the displaying on my end.
https://github.com/vlsunil/riscv-edk2/commit/a742fab0d73ab568aa2d2578a5ccfc400ffd2fa5

Reviewed-by: Daniel Schaefer <daniel.schaefer@hpe.com>

Tested with GCC 8.3.0 on Debian Buster.
Can boot -machine sifive_u to UEFI Shell and -machine virt on QEMU to Linux shell.

Sunil tested to compile on GCC 10.2.0 on Debian Buster - don't know if he booted.

Join devel@edk2.groups.io to automatically receive all group messages.