riscv, bpf: Fix incorrect runtime stats

[ Upstream commit 10541b374aa05c8118cc6a529a615882e53f261b ]

When __bpf_prog_enter() returns zero, the s1 register is not set to zero,
resulting in incorrect runtime stats. Fix it by setting s1 immediately upon
the return of __bpf_prog_enter().

Fixes: 49b5e77ae3e2 ("riscv, bpf: Add bpf trampoline support for RV64")
Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Pu Lehui <pulehui@huawei.com>
Acked-by: Björn Töpel <bjorn@kernel.org>
Link: https://lore.kernel.org/bpf/20240416064208.2919073-3-xukuohai@huaweicloud.com
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
index 719a97e7edb2c12277a8e08dd214e0eb03be094a..0bd747d1d00fc00a4e1ea117fb033bef8b3f54e5 100644 (file)
--- a/arch/riscv/net/bpf_jit_comp64.c
+++ b/arch/riscv/net/bpf_jit_comp64.c
@@ -740,6 +740,9 @@ static int invoke_bpf_prog(struct bpf_tramp_link *l, int args_off, int retval_of
        if (ret)
                return ret;
 
+       /* store prog start time */
+       emit_mv(RV_REG_S1, RV_REG_A0, ctx);
+
        /* if (__bpf_prog_enter(prog) == 0)
         *      goto skip_exec_of_prog;
         */
@@ -747,9 +750,6 @@ static int invoke_bpf_prog(struct bpf_tramp_link *l, int args_off, int retval_of
        /* nop reserved for conditional jump */
        emit(rv_nop(), ctx);
 
-       /* store prog start time */
-       emit_mv(RV_REG_S1, RV_REG_A0, ctx);
-
        /* arg1: &args_off */
        emit_addi(RV_REG_A0, RV_REG_FP, -args_off, ctx);
        if (!p->jited)