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Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mOAoW-00893u-CI; Thu, 09 Sep 2021 03:33:24 +0000 Received: from mail.loongson.cn ([114.242.206.163] helo=loongson.cn) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mOAoR-008939-0a; Thu, 09 Sep 2021 03:33:21 +0000 Received: from linux.localdomain (unknown [113.200.148.30]) by mail.loongson.cn (Coremail) with SMTP id AQAAf9DxheVPgDlhDyYCAA--.9478S2; Thu, 09 Sep 2021 11:32:32 +0800 (CST) From: Tiezhu Yang To: Shubham Bansal , Russell King , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Zi Shen Lim , Catalin Marinas , Will Deacon , Paul Burton , Thomas Bogendoerfer , naveen.n.rao@linux.ibm.com, Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , Luke Nelson , Xi Wang , Paul Walmsley , Palmer Dabbelt , Albert Ou , bjorn@kernel.org, davem@davemloft.net, Johan Almbladh , Paul Chaignon Cc: netdev@vger.kernel.org, bpf@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, sparclinux@vger.kernel.org Subject: [PATCH bpf-next] bpf: Change value of MAX_TAIL_CALL_CNT from 32 to 33 Date: Thu, 9 Sep 2021 11:32:30 +0800 Message-Id: <1631158350-3661-1-git-send-email-yangtiezhu@loongson.cn> X-Mailer: git-send-email 2.1.0 X-CM-TRANSID: AQAAf9DxheVPgDlhDyYCAA--.9478S2 X-Coremail-Antispam: 1UD129KBjvJXoWxtr13GF1ftFyfWF45Zr4kCrg_yoWftF1rpr 18twnakrWvqw15Aa4xKayUWw4UKF4vgF47KFn8CrWSyanFvr9rWr13Kw15ZFZ0vrW8Jw4r WFZ0kr43C3WkXwUanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUvKb7Iv0xC_Kw4lb4IE77IF4wAFF20E14v26rWj6s0DM7CY07I2 0VC2zVCF04k26cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rw A2F7IY1VAKz4vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_Xr0_Ar1l84ACjcxK6xII jxv20xvEc7CjxVAFwI0_Gr1j6F4UJwA2z4x0Y4vEx4A2jsIE14v26r4UJVWxJr1l84ACjc xK6I8E87Iv6xkF7I0E14v26F4UJVW0owAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40E FcxC0VAKzVAqx4xG6I80ewAv7VC0I7IYx2IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Gr 0_Cr1lOx8S6xCaFVCjc4AY6r1j6r4UM4x0Y48IcxkI7VAKI48JM4IIrI8v6xkF7I0E8cxa n2IY04v7MxkIecxEwVAFwVW8GwCF04k20xvY0x0EwIxGrwCFx2IqxVCFs4IE7xkEbVWUJV W8JwC20s026c02F40E14v26r1j6r18MI8I3I0E7480Y4vE14v26r106r1rMI8E67AF67kF 1VAFwI0_Wrv_Gr1UMIIYrxkI7VAKI48JMIIF0xvE2Ix0cI8IcVAFwI0_Jr0_JF4lIxAIcV C0I7IYx2IY6xkF7I0E14v26r4j6F4UMIIF0xvE42xK8VAvwI8IcIk0rVWrZr1j6s0DMIIF 0xvEx4A2jsIE14v26r1j6r4UMIIF0xvEx4A2jsIEc7CjxVAFwI0_Gr0_Gr1UYxBIdaVFxh VjvjDU0xZFpf9x07bz4SrUUUUU= X-CM-SenderInfo: p1dqw3xlh2x3gn0dqz5rrqw2lrqou0/ X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210908_203319_522153_0F2BE31B X-CRM114-Status: GOOD ( 18.82 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org In the current code, the actual max tail call count is 33 which is greater than MAX_TAIL_CALL_CNT (defined as 32), the actual limit is not consistent with the meaning of MAX_TAIL_CALL_CNT, there is some confusion and need to spend some time to think the reason at the first glance. We can see the historical evolution from commit 04fd61ab36ec ("bpf: allow bpf programs to tail-call other bpf programs") and commit f9dabe016b63 ("bpf: Undo off-by-one in interpreter tail call count limit"). In order to avoid changing existing behavior, the actual limit is 33 now, this is resonable. After commit 874be05f525e ("bpf, tests: Add tail call test suite"), we can see there exists failed testcase. On all archs when CONFIG_BPF_JIT_ALWAYS_ON is not set: # echo 0 > /proc/sys/net/core/bpf_jit_enable # modprobe test_bpf # dmesg | grep -w FAIL Tail call error path, max count reached jited:0 ret 34 != 33 FAIL On some archs: # echo 1 > /proc/sys/net/core/bpf_jit_enable # modprobe test_bpf # dmesg | grep -w FAIL Tail call error path, max count reached jited:1 ret 34 != 33 FAIL So it is necessary to change the value of MAX_TAIL_CALL_CNT from 32 to 33, then do some small changes of the related code. With this patch, it does not change the current limit, MAX_TAIL_CALL_CNT can reflect the actual max tail call count, and the above failed testcase can be fixed. Signed-off-by: Tiezhu Yang --- arch/arm/net/bpf_jit_32.c | 11 ++++++----- arch/arm64/net/bpf_jit_comp.c | 7 ++++--- arch/mips/net/ebpf_jit.c | 4 ++-- arch/powerpc/net/bpf_jit_comp32.c | 4 ++-- arch/powerpc/net/bpf_jit_comp64.c | 12 ++++++------ arch/riscv/net/bpf_jit_comp32.c | 4 ++-- arch/riscv/net/bpf_jit_comp64.c | 4 ++-- arch/sparc/net/bpf_jit_comp_64.c | 8 ++++---- include/linux/bpf.h | 2 +- kernel/bpf/core.c | 4 ++-- 10 files changed, 31 insertions(+), 29 deletions(-) diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c index a951276..39d9ae9 100644 --- a/arch/arm/net/bpf_jit_32.c +++ b/arch/arm/net/bpf_jit_32.c @@ -1180,18 +1180,19 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx) /* tmp2[0] = array, tmp2[1] = index */ - /* if (tail_call_cnt > MAX_TAIL_CALL_CNT) - * goto out; + /* * tail_call_cnt++; + * if (tail_call_cnt > MAX_TAIL_CALL_CNT) + * goto out; */ + tc = arm_bpf_get_reg64(tcc, tmp, ctx); + emit(ARM_ADDS_I(tc[1], tc[1], 1), ctx); + emit(ARM_ADC_I(tc[0], tc[0], 0), ctx); lo = (u32)MAX_TAIL_CALL_CNT; hi = (u32)((u64)MAX_TAIL_CALL_CNT >> 32); - tc = arm_bpf_get_reg64(tcc, tmp, ctx); emit(ARM_CMP_I(tc[0], hi), ctx); _emit(ARM_COND_EQ, ARM_CMP_I(tc[1], lo), ctx); _emit(ARM_COND_HI, ARM_B(jmp_offset), ctx); - emit(ARM_ADDS_I(tc[1], tc[1], 1), ctx); - emit(ARM_ADC_I(tc[0], tc[0], 0), ctx); arm_bpf_put_reg64(tcc, tmp, ctx); /* prog = array->ptrs[index] diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index 41c23f4..5d6c843 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -286,14 +286,15 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx) emit(A64_CMP(0, r3, tmp), ctx); emit(A64_B_(A64_COND_CS, jmp_offset), ctx); - /* if (tail_call_cnt > MAX_TAIL_CALL_CNT) - * goto out; + /* * tail_call_cnt++; + * if (tail_call_cnt > MAX_TAIL_CALL_CNT) + * goto out; */ + emit(A64_ADD_I(1, tcc, tcc, 1), ctx); emit_a64_mov_i64(tmp, MAX_TAIL_CALL_CNT, ctx); emit(A64_CMP(1, tcc, tmp), ctx); emit(A64_B_(A64_COND_HI, jmp_offset), ctx); - emit(A64_ADD_I(1, tcc, tcc, 1), ctx); /* prog = array->ptrs[index]; * if (prog == NULL) diff --git a/arch/mips/net/ebpf_jit.c b/arch/mips/net/ebpf_jit.c index 3a73e93..029fc34 100644 --- a/arch/mips/net/ebpf_jit.c +++ b/arch/mips/net/ebpf_jit.c @@ -617,14 +617,14 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx, int this_idx) b_off = b_imm(this_idx + 1, ctx); emit_instr(ctx, bne, MIPS_R_AT, MIPS_R_ZERO, b_off); /* - * if (TCC-- < 0) + * if (--TCC < 0) * goto out; */ /* Delay slot */ tcc_reg = (ctx->flags & EBPF_TCC_IN_V1) ? MIPS_R_V1 : MIPS_R_S4; emit_instr(ctx, daddiu, MIPS_R_T5, tcc_reg, -1); b_off = b_imm(this_idx + 1, ctx); - emit_instr(ctx, bltz, tcc_reg, b_off); + emit_instr(ctx, bltz, MIPS_R_T5, b_off); /* * prog = array->ptrs[index]; * if (prog == NULL) diff --git a/arch/powerpc/net/bpf_jit_comp32.c b/arch/powerpc/net/bpf_jit_comp32.c index beb12cb..b5585ad 100644 --- a/arch/powerpc/net/bpf_jit_comp32.c +++ b/arch/powerpc/net/bpf_jit_comp32.c @@ -221,12 +221,12 @@ static void bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32 PPC_BCC(COND_GE, out); /* + * tail_call_cnt++; * if (tail_call_cnt > MAX_TAIL_CALL_CNT) * goto out; */ - EMIT(PPC_RAW_CMPLWI(_R0, MAX_TAIL_CALL_CNT)); - /* tail_call_cnt++; */ EMIT(PPC_RAW_ADDIC(_R0, _R0, 1)); + EMIT(PPC_RAW_CMPLWI(_R0, MAX_TAIL_CALL_CNT)); PPC_BCC(COND_GT, out); /* prog = array->ptrs[index]; */ diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c index b87a63d..bb15cc4 100644 --- a/arch/powerpc/net/bpf_jit_comp64.c +++ b/arch/powerpc/net/bpf_jit_comp64.c @@ -227,6 +227,12 @@ static void bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32 PPC_BCC(COND_GE, out); /* + * tail_call_cnt++; + */ + EMIT(PPC_RAW_ADDI(b2p[TMP_REG_1], b2p[TMP_REG_1], 1)); + PPC_BPF_STL(b2p[TMP_REG_1], 1, bpf_jit_stack_tailcallcnt(ctx)); + + /* * if (tail_call_cnt > MAX_TAIL_CALL_CNT) * goto out; */ @@ -234,12 +240,6 @@ static void bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32 EMIT(PPC_RAW_CMPLWI(b2p[TMP_REG_1], MAX_TAIL_CALL_CNT)); PPC_BCC(COND_GT, out); - /* - * tail_call_cnt++; - */ - EMIT(PPC_RAW_ADDI(b2p[TMP_REG_1], b2p[TMP_REG_1], 1)); - PPC_BPF_STL(b2p[TMP_REG_1], 1, bpf_jit_stack_tailcallcnt(ctx)); - /* prog = array->ptrs[index]; */ EMIT(PPC_RAW_MULI(b2p[TMP_REG_1], b2p_index, 8)); EMIT(PPC_RAW_ADD(b2p[TMP_REG_1], b2p[TMP_REG_1], b2p_bpf_array)); diff --git a/arch/riscv/net/bpf_jit_comp32.c b/arch/riscv/net/bpf_jit_comp32.c index e649742..1608d94 100644 --- a/arch/riscv/net/bpf_jit_comp32.c +++ b/arch/riscv/net/bpf_jit_comp32.c @@ -800,12 +800,12 @@ static int emit_bpf_tail_call(int insn, struct rv_jit_context *ctx) /* * temp_tcc = tcc - 1; - * if (tcc < 0) + * if (temp_tcc < 0) * goto out; */ emit(rv_addi(RV_REG_T1, RV_REG_TCC, -1), ctx); off = ninsns_rvoff(tc_ninsn - (ctx->ninsns - start_insn)); - emit_bcc(BPF_JSLT, RV_REG_TCC, RV_REG_ZERO, off, ctx); + emit_bcc(BPF_JSLT, RV_REG_T1, RV_REG_ZERO, off, ctx); /* * prog = array->ptrs[index]; diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c index 3af4131..6e9ba83 100644 --- a/arch/riscv/net/bpf_jit_comp64.c +++ b/arch/riscv/net/bpf_jit_comp64.c @@ -311,12 +311,12 @@ 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_JGE, RV_REG_A2, RV_REG_T1, off, ctx); - /* if (TCC-- < 0) + /* if (--TCC < 0) * goto out; */ emit_addi(RV_REG_T1, tcc, -1, ctx); off = ninsns_rvoff(tc_ninsn - (ctx->ninsns - start_insn)); - emit_branch(BPF_JSLT, tcc, RV_REG_ZERO, off, ctx); + emit_branch(BPF_JSLT, RV_REG_T1, RV_REG_ZERO, off, ctx); /* prog = array->ptrs[index]; * if (!prog) diff --git a/arch/sparc/net/bpf_jit_comp_64.c b/arch/sparc/net/bpf_jit_comp_64.c index 9a2f20c..50d914c 100644 --- a/arch/sparc/net/bpf_jit_comp_64.c +++ b/arch/sparc/net/bpf_jit_comp_64.c @@ -863,6 +863,10 @@ static void emit_tail_call(struct jit_ctx *ctx) emit_branch(BGEU, ctx->idx, ctx->idx + OFFSET1, ctx); emit_nop(ctx); + emit_alu_K(ADD, tmp, 1, ctx); + off = BPF_TAILCALL_CNT_SP_OFF; + emit(ST32 | IMMED | RS1(SP) | S13(off) | RD(tmp), ctx); + off = BPF_TAILCALL_CNT_SP_OFF; emit(LD32 | IMMED | RS1(SP) | S13(off) | RD(tmp), ctx); emit_cmpi(tmp, MAX_TAIL_CALL_CNT, ctx); @@ -870,10 +874,6 @@ static void emit_tail_call(struct jit_ctx *ctx) emit_branch(BGU, ctx->idx, ctx->idx + OFFSET2, ctx); emit_nop(ctx); - emit_alu_K(ADD, tmp, 1, ctx); - off = BPF_TAILCALL_CNT_SP_OFF; - emit(ST32 | IMMED | RS1(SP) | S13(off) | RD(tmp), ctx); - emit_alu3_K(SLL, bpf_index, 3, tmp, ctx); emit_alu(ADD, bpf_array, tmp, ctx); off = offsetof(struct bpf_array, ptrs); diff --git a/include/linux/bpf.h b/include/linux/bpf.h index f4c16f1..224cc7e 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1046,7 +1046,7 @@ struct bpf_array { }; #define BPF_COMPLEXITY_LIMIT_INSNS 1000000 /* yes. 1M insns */ -#define MAX_TAIL_CALL_CNT 32 +#define MAX_TAIL_CALL_CNT 33 #define BPF_F_ACCESS_MASK (BPF_F_RDONLY | \ BPF_F_RDONLY_PROG | \ diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index 9f4636d..8edb1c3 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -1564,10 +1564,10 @@ static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn) if (unlikely(index >= array->map.max_entries)) goto out; - if (unlikely(tail_call_cnt > MAX_TAIL_CALL_CNT)) - goto out; tail_call_cnt++; + if (unlikely(tail_call_cnt > MAX_TAIL_CALL_CNT)) + goto out; prog = READ_ONCE(array->ptrs[index]); if (!prog)