linux-kernel - [PATCH bpf-next 2/2] bpf, mips: Modify check condition about tail call count

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Message-Id: <1633777076-17256-3-git-send-email-yangtiezhu@loongson.cn>
Date:   Sat,  9 Oct 2021 18:57:56 +0800
From:   Tiezhu Yang <yangtiezhu@...ngson.cn>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Johan Almbladh <johan.almbladh@...finetworks.com>,
        Paul Burton <paulburton@...nel.org>
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        Xuefeng Li <lixuefeng@...ngson.cn>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>
Subject: [PATCH bpf-next 2/2] bpf, mips: Modify check condition about tail call count

In emit_tail_call() of bpf_jit_comp32.c, "blez t2" (t2 <= 0) is not
consistent with the comment "t2 < 0", modify the check condition to
keep consistency.

Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
---
 arch/mips/net/bpf_jit_comp32.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/mips/net/bpf_jit_comp32.c b/arch/mips/net/bpf_jit_comp32.c
index 9d7041a..b887c01 100644
--- a/arch/mips/net/bpf_jit_comp32.c
+++ b/arch/mips/net/bpf_jit_comp32.c
@@ -1312,12 +1312,12 @@ static int emit_tail_call(struct jit_context *ctx)
 	emit(ctx, sltu, t1, ind, t1);            /* t1 = ind < t1            */
 	emit(ctx, beqz, t1, get_offset(ctx, 1)); /* PC += off(1) if t1 == 0  */
 						 /* (next insn delay slot)   */
-	/* if (TCC-- <= 0) goto out */
+	/* if (--TCC < 0) goto out */
 	emit(ctx, lw, t2, ctx->stack_size, MIPS_R_SP);  /* t2 = *(SP + size) */
 	emit_load_delay(ctx);                     /* Load delay slot         */
-	emit(ctx, blez, t2, get_offset(ctx, 1));  /* PC += off(1) if t2 < 0  */
 	emit(ctx, addiu, t2, t2, -1);             /* t2-- (delay slot)       */
 	emit(ctx, sw, t2, ctx->stack_size, MIPS_R_SP);  /* *(SP + size) = t2 */
+	emit(ctx, bltz, t2, get_offset(ctx, 1));  /* PC += off(1) if t2 < 0  */
 
 	/* prog = ary->ptrs[ind] */
 	off = offsetof(struct bpf_array, ptrs);
-- 
2.1.0