[PATCH bpf-next 3/4] riscv, bpf: Add RV_TAILCALL_OFFSET macro to format tailcall offset

Pu Lehui
2023-09-19T03:57:13Z

From: Pu Lehui <pulehui@huawei.com>

Add RV_TAILCALL_OFFSET macro to format tailcall offset, and correct the
relevant comments.

Signed-off-by: Pu Lehui <pulehui@huawei.com>
---
arch/riscv/net/bpf_jit_comp64.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
index 57535cfe1..f2ded1151 100644
--- a/arch/riscv/net/bpf_jit_comp64.c
+++ b/arch/riscv/net/bpf_jit_comp64.c
@@ -13,7 +13,9 @@
#include <asm/patch.h>
#include "bpf_jit.h"

-#define RV_FENTRY_NINSNS 2
+#define RV_FENTRY_NINSNS 2
+/* fentry and TCC init insns will be skipped on tailcall */
+#define RV_TAILCALL_OFFSET ((RV_FENTRY_NINSNS + 1) * 4)

#define RV_REG_TCC RV_REG_A6
#define RV_REG_TCC_SAVED RV_REG_S6 /* Store A6 in S6 if program do calls */
@@ -243,8 +245,7 @@ static void __build_epilogue(bool is_tail_call, struct rv_jit_context *ctx)
if (!is_tail_call)
emit_mv(RV_REG_A0, RV_REG_A5, ctx);
emit_jalr(RV_REG_ZERO, is_tail_call ? RV_REG_T3 : RV_REG_RA,
- is_tail_call ? (RV_FENTRY_NINSNS + 1) * 4 : 0, /* skip reserved nops and TCC init */
- ctx);
+ is_tail_call ? RV_TAILCALL_OFFSET : 0, ctx);
}

static void emit_bcc(u8 cond, u8 rd, u8 rs, int rvoff,
@@ -371,7 +372,7 @@ static int emit_bpf_tail_call(int insn, struct rv_jit_context *ctx)
off = ninsns_rvoff(tc_ninsn - (ctx->ninsns - start_insn));
emit_branch(BPF_JEQ, RV_REG_T2, RV_REG_ZERO, off, ctx);

- /* goto *(prog->bpf_func + 4); */
+ /* goto *(prog->bpf_func + RV_TAILCALL_OFFSET); */
off = offsetof(struct bpf_prog, bpf_func);
if (is_12b_check(off, insn))
return -1;
--
2.25.1