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Tue, 18 Mar 2025 07:29:53 -0700 (PDT) Received: from localhost.localdomain ([2a04:ee41:4:b2de:1ac0:4dff:fe0f:3782]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-395cb40cdd0sm18348071f8f.77.2025.03.18.07.29.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 18 Mar 2025 07:29:53 -0700 (PDT) From: Anton Protopopov To: bpf@vger.kernel.org, Andrii Nakryiko , Daniel Borkmann , Eduard Zingerman , Yonghong Song , Quentin Monnet , Anton Protopopov , Alexei Starovoitov Subject: [RFC PATCH bpf-next 08/14] bpf, x86: implement static key support Date: Tue, 18 Mar 2025 14:33:12 +0000 Message-Id: <20250318143318.656785-9-aspsk@isovalent.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20250318143318.656785-1-aspsk@isovalent.com> References: <20250318143318.656785-1-aspsk@isovalent.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net X-Patchwork-State: RFC Implement bpf_arch_poke_static_branch() for x86. Namely, during each JIT loop, save IP values and sizes of jump instructions pointed by static keys. Then use the text_poke_bp() to toggle jumps/nops. Signed-off-by: Anton Protopopov --- arch/x86/net/bpf_jit_comp.c | 46 +++++++++++++++++++++++++++++++++++++ 1 file changed, 46 insertions(+) diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index 5856ac1aab80..31cadded820b 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -1569,6 +1569,8 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, u8 *rw_image const s32 imm32 = insn->imm; u32 dst_reg = insn->dst_reg; u32 src_reg = insn->src_reg; + int adjust_off = 0; + int abs_xlated_off; u8 b2 = 0, b3 = 0; u8 *start_of_ldx; s64 jmp_offset; @@ -1724,6 +1726,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, u8 *rw_image emit_mov_imm64(&prog, dst_reg, insn[1].imm, insn[0].imm); insn++; i++; + adjust_off = 1; break; /* dst %= src, dst /= src, dst %= imm32, dst /= imm32 */ @@ -2595,6 +2598,14 @@ st: if (is_imm8(insn->off)) return -EFAULT; } memcpy(rw_image + proglen, temp, ilen); + + /* + * Static keys need to know how the xlated code + * of static ja instructions maps to jited code + */ + abs_xlated_off = bpf_prog->aux->subprog_start + i - 1 - adjust_off; + bpf_prog_update_insn_ptr(bpf_prog, abs_xlated_off, proglen, ilen, + jmp_offset, image + proglen); } proglen += ilen; addrs[i] = proglen; @@ -3880,3 +3891,38 @@ bool bpf_jit_supports_timed_may_goto(void) { return true; } + +int bpf_arch_poke_static_branch(struct bpf_insn_ptr *ptr, bool on) +{ + int jmp_offset = ptr->jitted_jump_offset; + void *ip = ptr->jitted_ip; + u32 len = ptr->jitted_len; + u8 op[5]; + + if (WARN_ON_ONCE(!ip)) + return -EINVAL; + + if (WARN_ON_ONCE(is_imm8(jmp_offset) && len != 2)) + return -EINVAL; + + if (WARN_ON_ONCE(!is_imm8(jmp_offset) && len != 5)) + return -EINVAL; + + if (on) { + if (len == 2) { + op[0] = 0xEB; + op[1] = jmp_offset; + } else { + op[0] = 0xE9; + memcpy(&op[1], &jmp_offset, 4); + } + } else { + memcpy(op, x86_nops[len], len); + } + + mutex_lock(&text_mutex); + text_poke_bp(ip, op, len, NULL); + mutex_unlock(&text_mutex); + + return 0; +}