[PATCH DO NOT REVIEW v4 4/7] riscv: errata: andes: Fix auipc-jalr addresses in patched alternatives

[Prabhakar]

From: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>

This patch is added just for building purpose, as patch [0] will export
this in its next version.

https://patchwork.kernel.org/project/linux-riscv/patch/20221110164924.529386-6-heiko@xxxxxxxxx/

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
---
Note, as Heiko will be exporting riscv_alternative_fix_auipc_jalr() function
so that it can be used other erratas Ive just included for compilation.
---
 arch/riscv/errata/andes/errata.c | 71 ++++++++++++++++++++++++++++++++
 1 file changed, 71 insertions(+)

diff --git a/arch/riscv/errata/andes/errata.c b/arch/riscv/errata/andes/errata.c
index ec3e052ca8c7..4061ad4983bc 100644
--- a/arch/riscv/errata/andes/errata.c
+++ b/arch/riscv/errata/andes/errata.c
@@ -13,9 +13,80 @@
 #include <asm/alternative.h>
 #include <asm/cacheflush.h>
 #include <asm/errata_list.h>
+#include <asm/parse_asm.h>
 #include <asm/patch.h>
+#include <asm/sbi.h>
 #include <asm/vendorid_list.h>
 
+/* Copy of Heiko's code from patch [0]
+ * [0] https://patchwork.kernel.org/project/linux-riscv/patch/20221110164924.529386-6-heiko@xxxxxxxxx/
+ */
+DECLARE_INSN(jalr, MATCH_JALR, MASK_JALR)
+DECLARE_INSN(auipc, MATCH_AUIPC, MASK_AUIPC)
+
+static inline bool is_auipc_jalr_pair(long insn1, long insn2)
+{
+	return is_auipc_insn(insn1) && is_jalr_insn(insn2);
+}
+
+#define JALR_SIGN_MASK		BIT(I_IMM_SIGN_OPOFF - I_IMM_11_0_OPOFF)
+#define JALR_OFFSET_MASK	I_IMM_11_0_MASK
+#define AUIPC_OFFSET_MASK	U_IMM_31_12_MASK
+#define AUIPC_PAD		(0x00001000)
+#define JALR_SHIFT		I_IMM_11_0_OPOFF
+
+#define to_jalr_imm(offset)						\
+	((offset & I_IMM_11_0_MASK) << I_IMM_11_0_OPOFF)
+
+#define to_auipc_imm(offset)						\
+	((offset & JALR_SIGN_MASK) ?					\
+	((offset & AUIPC_OFFSET_MASK) + AUIPC_PAD) :			\
+	(offset & AUIPC_OFFSET_MASK))
+
+static void riscv_alternative_fix_auipc_jalr(unsigned int *alt_ptr,
+					     unsigned int len, int patch_offset)
+{
+	int num_instr = len / sizeof(u32);
+	unsigned int call[2];
+	int i;
+	int imm1;
+	u32 rd1;
+
+	for (i = 0; i < num_instr; i++) {
+		/* is there a further instruction? */
+		if (i + 1 >= num_instr)
+			continue;
+
+		if (!is_auipc_jalr_pair(*(alt_ptr + i), *(alt_ptr + i + 1)))
+			continue;
+
+		/* call will use ra register */
+		rd1 = EXTRACT_RD_REG(*(alt_ptr + i));
+		if (rd1 != 1)
+			continue;
+
+		/* get and adjust new target address */
+		imm1 = EXTRACT_UTYPE_IMM(*(alt_ptr + i));
+		imm1 += EXTRACT_ITYPE_IMM(*(alt_ptr + i + 1));
+		imm1 -= patch_offset;
+
+		/* pick the original auipc + jalr */
+		call[0] = *(alt_ptr + i);
+		call[1] = *(alt_ptr + i + 1);
+
+		/* drop the old IMMs */
+		call[0] &= ~(U_IMM_31_12_MASK);
+		call[1] &= ~(I_IMM_11_0_MASK << I_IMM_11_0_OPOFF);
+
+		/* add the adapted IMMs */
+		call[0] |= to_auipc_imm(imm1);
+		call[1] |= to_jalr_imm(imm1);
+
+		/* patch the call place again */
+		patch_text_nosync(alt_ptr + i, call, 8);
+	}
+}
+
 static bool errata_probe_iocp(unsigned int stage, unsigned long arch_id, unsigned long impid)
 {
 	if (!IS_ENABLED(CONFIG_ERRATA_ANDES_CMO))
-- 
2.25.1