[RFC PATCH 2/6] riscv: alternatives: support auipc+load pair

[Bo Gan]

Previously only auipc+jalr pair is supported. Add auipc+load pair
to support PC-relative memory load instruction as well.

Signed-off-by: Bo Gan <ganboing at gmail.com>
---
 arch/riscv/include/asm/insn.h   |  8 ++++++++
 arch/riscv/kernel/alternative.c | 11 ++++++-----
 2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/arch/riscv/include/asm/insn.h b/arch/riscv/include/asm/insn.h
index c3005573e8c99..1c791a8732efc 100644
--- a/arch/riscv/include/asm/insn.h
+++ b/arch/riscv/include/asm/insn.h
@@ -135,6 +135,8 @@
 #define RVC_C2_RS1_MASK		GENMASK(4, 0)
 
 /* parts of opcode for RVG*/
+#define RVG_OPCODE_LOAD		0x03
+#define RVG_OPCODE_STORE	0x23
 #define RVG_OPCODE_FENCE	0x0f
 #define RVG_OPCODE_AUIPC	0x17
 #define RVG_OPCODE_BRANCH	0x63
@@ -198,6 +200,8 @@
 #define RVG_MATCH_BGE		(RV_ENCODE_FUNCT3(BGE) | RVG_OPCODE_BRANCH)
 #define RVG_MATCH_BLTU		(RV_ENCODE_FUNCT3(BLTU) | RVG_OPCODE_BRANCH)
 #define RVG_MATCH_BGEU		(RV_ENCODE_FUNCT3(BGEU) | RVG_OPCODE_BRANCH)
+#define RVG_MATCH_LOAD		(RVG_OPCODE_LOAD)
+#define RVG_MATCH_STORE		(RVG_OPCODE_STORE)
 #define RVG_MATCH_EBREAK	(RV_ENCODE_FUNCT12(EBREAK) | RVG_OPCODE_SYSTEM)
 #define RVG_MATCH_SRET		(RV_ENCODE_FUNCT12(SRET) | RVG_OPCODE_SYSTEM)
 #define RVC_MATCH_C_BEQZ	(RVC_ENCODE_FUNCT3(C_BEQZ) | RVC_OPCODE_C1)
@@ -222,6 +226,8 @@
 #define RVG_MASK_BGE		(RV_INSN_FUNCT3_MASK | RV_INSN_OPCODE_MASK)
 #define RVG_MASK_BLTU		(RV_INSN_FUNCT3_MASK | RV_INSN_OPCODE_MASK)
 #define RVG_MASK_BGEU		(RV_INSN_FUNCT3_MASK | RV_INSN_OPCODE_MASK)
+#define RVG_MASK_LOAD		(RV_INSN_OPCODE_MASK)
+#define RVG_MASK_STORE		(RV_INSN_OPCODE_MASK)
 #define RVC_MASK_C_BEQZ		(RVC_INSN_FUNCT3_MASK | RVC_INSN_OPCODE_MASK)
 #define RVC_MASK_C_BNEZ		(RVC_INSN_FUNCT3_MASK | RVC_INSN_OPCODE_MASK)
 #define RVC_MASK_C_EBREAK	0xffff
@@ -262,6 +268,8 @@ __RISCV_INSN_FUNCS(c_ebreak, RVC_MASK_C_EBREAK, RVC_MATCH_C_EBREAK)
 __RISCV_INSN_FUNCS(ebreak, RVG_MASK_EBREAK, RVG_MATCH_EBREAK)
 __RISCV_INSN_FUNCS(sret, RVG_MASK_SRET, RVG_MATCH_SRET)
 __RISCV_INSN_FUNCS(fence, RVG_MASK_FENCE, RVG_MATCH_FENCE);
+__RISCV_INSN_FUNCS(load, RVG_MASK_LOAD, RVG_MATCH_LOAD);
+__RISCV_INSN_FUNCS(store, RVG_MASK_STORE, RVG_MATCH_STORE);
 
 /* special case to catch _any_ system instruction */
 static __always_inline bool riscv_insn_is_system(u32 code)
diff --git a/arch/riscv/kernel/alternative.c b/arch/riscv/kernel/alternative.c
index 7642704c7f184..04a9d3aed4647 100644
--- a/arch/riscv/kernel/alternative.c
+++ b/arch/riscv/kernel/alternative.c
@@ -74,7 +74,7 @@ static u32 riscv_instruction_at(void *p)
 	return (u32)parcel[0] | (u32)parcel[1] << 16;
 }
 
-static void riscv_alternative_fix_auipc_jalr(void *ptr, u32 auipc_insn,
+static void riscv_alternative_fix_auipc_pair(void *ptr, u32 auipc_insn,
 					     u32 jalr_insn, int patch_offset)
 {
 	u32 call[2] = { auipc_insn, jalr_insn };
@@ -123,14 +123,15 @@ void riscv_alternative_fix_offsets(void *alt_ptr, unsigned int len,
 		if (riscv_insn_is_auipc(insn) && i < num_insn - 1) {
 			u32 insn2 = riscv_instruction_at(alt_ptr + (i + 1) * sizeof(u32));
 
-			if (!riscv_insn_is_jalr(insn2))
+			if (!riscv_insn_is_jalr(insn2) &&
+			    !riscv_insn_is_load(insn2))
 				continue;
 
-			/* if instruction pair is a call, it will use the ra register */
-			if (RV_EXTRACT_RD_REG(insn) != 1)
+			if (RV_EXTRACT_RD_REG(insn) != RV_EXTRACT_RS1_REG(insn2))
 				continue;
 
-			riscv_alternative_fix_auipc_jalr(alt_ptr + i * sizeof(u32),
+			/* insn2 use rd of insn as rs1, patch it */
+			riscv_alternative_fix_auipc_pair(alt_ptr + i * sizeof(u32),
 							 insn, insn2, patch_offset);
 			i++;
 		}
-- 
2.34.1