[PATCH v4 3/5] RISC-V: fix jal addresses in patched alternatives

[Heiko Stuebner]

From: Heiko Stuebner <heiko.stuebner at vrull.eu>

Alternatives live in a different section, so addresses used by jal
instructions will point to wrong locations after the patch got applied.

Similar to arm64, adjust the location to consider that offset.

Signed-off-by: Heiko Stuebner <heiko.stuebner at vrull.eu>
---
 arch/riscv/kernel/alternative.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/arch/riscv/kernel/alternative.c b/arch/riscv/kernel/alternative.c
index 6212ea0eed72..985c284fe9f4 100644
--- a/arch/riscv/kernel/alternative.c
+++ b/arch/riscv/kernel/alternative.c
@@ -79,6 +79,21 @@ static void riscv_alternative_fix_auipc_jalr(void *ptr, u32 auipc_insn,
 	patch_text_nosync(ptr, call, sizeof(u32) * 2);
 }
 
+static void riscv_alternative_fix_jal(void *ptr, u32 jal_insn, int patch_offset)
+{
+	s32 imm;
+
+	/* get and adjust new target address */
+	imm = riscv_insn_extract_jtype_imm(jal_insn);
+	imm -= patch_offset;
+
+	/* update instructions */
+	riscv_insn_insert_jtype_imm(&jal_insn, imm);
+
+	/* patch the call place again */
+	patch_text_nosync(ptr, &jal_insn, sizeof(u32));
+}
+
 void riscv_alternative_fix_offsets(void *alt_ptr, unsigned int len,
 				      int patch_offset)
 {
@@ -106,6 +121,18 @@ void riscv_alternative_fix_offsets(void *alt_ptr, unsigned int len,
 			riscv_alternative_fix_auipc_jalr(alt_ptr + i * sizeof(u32),
 							 insn, insn2, patch_offset);
 		}
+
+		if (riscv_insn_is_jal(insn)) {
+			s32 imm = riscv_insn_extract_jtype_imm(insn);
+
+			/* don't modify jumps inside the alternative block */
+			if ((alt_ptr + i * sizeof(u32) + imm) >= alt_ptr &&
+			    (alt_ptr + i * sizeof(u32) + imm) < (alt_ptr + len))
+				continue;
+
+			riscv_alternative_fix_jal(alt_ptr + i * sizeof(u32),
+						  insn, patch_offset);
+		}
 	}
 }
 
-- 
2.35.1