From: Pu Lehui <pulehui@xxxxxxxxxx>
There are many extension helpers in the current branch instructions, and
the implementation is a bit complicated. We simplify this logic through
two simple extension helpers with alternate register.
Signed-off-by: Pu Lehui <pulehui@xxxxxxxxxx>
---
arch/riscv/net/bpf_jit_comp64.c | 82 +++++++++++++--------------------
1 file changed, 31 insertions(+), 51 deletions(-)
diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
index 4a649e195..0c6ffe11a 100644
--- a/arch/riscv/net/bpf_jit_comp64.c
+++ b/arch/riscv/net/bpf_jit_comp64.c
@@ -141,6 +141,19 @@ static bool in_auipc_jalr_range(s64 val)
val < ((1L << 31) - (1L << 11));
}
+/* Modify rd pointer to alternate reg to avoid corrupting original reg */
+static void emit_sextw_alt(u8 *rd, u8 ra, struct rv_jit_context *ctx)
+{
+ emit_sextw(ra, *rd, ctx);
+ *rd = ra;
+}
+
+static void emit_zextw_alt(u8 *rd, u8 ra, struct rv_jit_context *ctx)
+{
+ emit_zextw(ra, *rd, ctx);
+ *rd = ra;
+}
+
/* Emit fixed-length instructions for address */
static int emit_addr(u8 rd, u64 addr, bool extra_pass, struct rv_jit_context *ctx)
{
@@ -395,38 +408,6 @@ static void init_regs(u8 *rd, u8 *rs, const struct bpf_insn *insn,
*rs = bpf_to_rv_reg(insn->src_reg, ctx);
}
-static void emit_zext_32_rd_rs(u8 *rd, u8 *rs, struct rv_jit_context *ctx)
-{
- emit_mv(RV_REG_T2, *rd, ctx);
- emit_zextw(RV_REG_T2, RV_REG_T2, ctx);
- emit_mv(RV_REG_T1, *rs, ctx);
- emit_zextw(RV_REG_T1, RV_REG_T1, ctx);
- *rd = RV_REG_T2;
- *rs = RV_REG_T1;
-}
-
-static void emit_sext_32_rd_rs(u8 *rd, u8 *rs, struct rv_jit_context *ctx)
-{
- emit_sextw(RV_REG_T2, *rd, ctx);
- emit_sextw(RV_REG_T1, *rs, ctx);
- *rd = RV_REG_T2;
- *rs = RV_REG_T1;
-}
-
-static void emit_zext_32_rd_t1(u8 *rd, struct rv_jit_context *ctx)
-{
- emit_mv(RV_REG_T2, *rd, ctx);
- emit_zextw(RV_REG_T2, RV_REG_T2, ctx);
- emit_zextw(RV_REG_T1, RV_REG_T2, ctx);
- *rd = RV_REG_T2;
-}
-
-static void emit_sext_32_rd(u8 *rd, struct rv_jit_context *ctx)
-{
- emit_sextw(RV_REG_T2, *rd, ctx);
- *rd = RV_REG_T2;
-}
-
static int emit_jump_and_link(u8 rd, s64 rvoff, bool fixed_addr,
struct rv_jit_context *ctx)
{
@@ -1372,22 +1353,22 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
rvoff = rv_offset(i, off, ctx);
if (!is64) {
s = ctx->ninsns;
- if (is_signed_bpf_cond(BPF_OP(code)))
- emit_sext_32_rd_rs(&rd, &rs, ctx);
- else
- emit_zext_32_rd_rs(&rd, &rs, ctx);
+ if (is_signed_bpf_cond(BPF_OP(code))) {
+ emit_sextw_alt(&rs, RV_REG_T1, ctx);
+ emit_sextw_alt(&rd, RV_REG_T2, ctx);
+ } else {
+ emit_zextw_alt(&rs, RV_REG_T1, ctx);
+ emit_zextw_alt(&rd, RV_REG_T2, ctx);
+ }
e = ctx->ninsns;
-
/* Adjust for extra insns */
rvoff -= ninsns_rvoff(e - s);
}
-
if (BPF_OP(code) == BPF_JSET) {
/* Adjust for and */
rvoff -= 4;
emit_and(RV_REG_T1, rd, rs, ctx);
- emit_branch(BPF_JNE, RV_REG_T1, RV_REG_ZERO, rvoff,
- ctx);
+ emit_branch(BPF_JNE, RV_REG_T1, RV_REG_ZERO, rvoff, ctx);
} else {
emit_branch(BPF_OP(code), rd, rs, rvoff, ctx);
}
@@ -1416,21 +1397,20 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
case BPF_JMP32 | BPF_JSLE | BPF_K:
rvoff = rv_offset(i, off, ctx);
s = ctx->ninsns;
- if (imm) {
+ if (imm)
emit_imm(RV_REG_T1, imm, ctx);
- rs = RV_REG_T1;
- } else {
- /* If imm is 0, simply use zero register. */
- rs = RV_REG_ZERO;
- }
+ rs = imm ? RV_REG_T1 : RV_REG_ZERO;
if (!is64) {
- if (is_signed_bpf_cond(BPF_OP(code)))
- emit_sext_32_rd(&rd, ctx);
- else
- emit_zext_32_rd_t1(&rd, ctx);
+ if (is_signed_bpf_cond(BPF_OP(code))) {
+ emit_sextw_alt(&rd, RV_REG_T2, ctx);
+ /* rs has been sign extended */
+ } else {
+ emit_zextw_alt(&rd, RV_REG_T2, ctx);
+ if (imm)
+ emit_zextw(rs, rs, ctx);
+ }
}
e = ctx->ninsns;
-
/* Adjust for extra insns */
rvoff -= ninsns_rvoff(e - s);
emit_branch(BPF_OP(code), rd, rs, rvoff, ctx);
--
2.25.1
