From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B84B423B8 for ; Fri, 28 Jul 2023 18:59:08 +0000 (UTC) Received: from 69-171-232-181.mail-mxout.facebook.com (69-171-232-181.mail-mxout.facebook.com [69.171.232.181]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DEEC130F5 for ; Fri, 28 Jul 2023 11:59:06 -0700 (PDT) Received: by devbig309.ftw3.facebook.com (Postfix, from userid 128203) id E451723D27EB4; Fri, 28 Jul 2023 11:58:52 -0700 (PDT) From: Yonghong Song To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , kernel-team@fb.com, Martin KaFai Lau , bpf@ietf.org, David Vernet Subject: [PATCH bpf-next] docs/bpf: Improve documentation for cpu=v4 instructions Date: Fri, 28 Jul 2023 11:58:52 -0700 Message-Id: <20230728185852.3572290-1-yonghong.song@linux.dev> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Spam-Status: No, score=-0.3 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_BLOCKED,RDNS_DYNAMIC,SPF_HELO_PASS,SPF_SOFTFAIL, TVD_RCVD_IP,T_SCC_BODY_TEXT_LINE autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Improve documentation for cpu=3Dv4 instructions based on David's suggestions. Cc: bpf@ietf.org Suggested-by: David Vernet Signed-off-by: Yonghong Song --- .../bpf/standardization/instruction-set.rst | 54 +++++++++++-------- 1 file changed, 32 insertions(+), 22 deletions(-) diff --git a/Documentation/bpf/standardization/instruction-set.rst b/Docu= mentation/bpf/standardization/instruction-set.rst index 23e880a83a1f..95079a53a35b 100644 --- a/Documentation/bpf/standardization/instruction-set.rst +++ b/Documentation/bpf/standardization/instruction-set.rst @@ -174,7 +174,7 @@ BPF_MOV 0xb0 0 dst =3D src BPF_MOVSX 0xb0 8/16/32 dst =3D (s8,s16,s32)src BPF_ARSH 0xc0 0 sign extending dst >>=3D (src & mask) BPF_END 0xd0 0 byte swap operations (see `Byte swap instructi= ons`_ below) -=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D +=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D =3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D =20 Underflow and overflow are allowed during arithmetic operations, meaning the 64-bit or 32-bit value will wrap. If eBPF program execution would @@ -201,26 +201,32 @@ where '(u32)' indicates that the upper 32 bits are = zeroed. =20 dst =3D dst ^ imm32 =20 -Note that most instructions have instruction offset of 0. But three inst= ructions -(BPF_SDIV, BPF_SMOD, BPF_MOVSX) have non-zero offset. +Note that most instructions have instruction offset of 0. Only three ins= tructions +(``BPF_SDIV``, ``BPF_SMOD``, ``BPF_MOVSX``) have a non-zero offset. =20 The devision and modulo operations support both unsigned and signed flav= ors. -For unsigned operation (BPF_DIV and BPF_MOD), for ``BPF_ALU``, 'imm' is = first -interpreted as an unsigned 32-bit value, whereas for ``BPF_ALU64``, 'imm= ' is -first sign extended to 64 bits and the result interpreted as an unsigned= 64-bit -value. For signed operation (BPF_SDIV and BPF_SMOD), for ``BPF_ALU``, '= imm' is -interpreted as a signed value. For ``BPF_ALU64``, the 'imm' is sign exte= nded -from 32 to 64 and interpreted as a signed 64-bit value. =20 -Instruction BPF_MOVSX does move operation with sign extension. -``BPF_ALU | MOVSX`` sign extendes 8-bit and 16-bit into 32-bit and upper= 32-bit are zeroed. -``BPF_ALU64 | MOVSX`` sign extends 8-bit, 16-bit and 32-bit into 64-bit. +For unsigned operations (``BPF_DIV`` and ``BPF_MOD``), for ``BPF_ALU``, +'imm' is interpreted as a 32-bit unsigned value. For ``BPF_ALU64``, +'imm' is first sign extended from 32 to 64 bits, and then interpreted as +a 64-bit unsigned value. + +For signed operations (``BPF_SDIV`` and ``BPF_SMOD``), for ``BPF_ALU``, +'imm' is interpreted as a 32-bit signed value. For ``BPF_ALU64``, 'imm' +is first sign extended from 32 to 64 bits, and then interpreted as a +64-bit signed value. + +The ``BPF_MOVSX`` instruction does a move operation with sign extension. +``BPF_ALU | BPF_MOVSX`` sign extends 8-bit and 16-bit operands into 32 +bit operands, and zeroes the remaining upper 32 bits. +``BPF_ALU64 | BPF_MOVSX`` sign extends 8-bit, 16-bit, and 32-bit +operands into 64 bit operands. =20 Shift operations use a mask of 0x3F (63) for 64-bit operations and 0x1F = (31) for 32-bit operations. =20 Byte swap instructions -~~~~~~~~~~~~~~~~~~~~~~ +---------------------- =20 The byte swap instructions use instruction classes of ``BPF_ALU`` and ``= BPF_ALU64`` and a 4-bit 'code' field of ``BPF_END``. @@ -228,16 +234,17 @@ and a 4-bit 'code' field of ``BPF_END``. The byte swap instructions operate on the destination register only and do not use a separate source register or immediate value. =20 -For ``BPF_ALU``, the 1-bit source operand field in the opcode is used to= select what byte -order the operation convert from or to. For ``BPF_ALU64``, the 1-bit sou= rce operand -field in the opcode is not used and must be 0. +For ``BPF_ALU``, the 1-bit source operand field in the opcode is used to +select what byte order the operation converts from or to. For +``BPF_ALU64``, the 1-bit source operand field in the opcode is reserved +and must be set to 0. =20 =3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D class source value description =3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D BPF_ALU BPF_TO_LE 0x00 convert between host byte order and little = endian BPF_ALU BPF_TO_BE 0x08 convert between host byte order and big end= ian -BPF_ALU64 BPF_TO_LE 0x00 do byte swap unconditionally +BPF_ALU64 Reserved 0x00 do byte swap unconditionally =3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =20 The 'imm' field encodes the width of the swap operations. The following= widths @@ -305,9 +312,12 @@ where 's>=3D' indicates a signed '>=3D' comparison. =20 where 'imm' means the branch offset comes from insn 'imm' field. =20 -Note there are two flavors of BPF_JA instrions. BPF_JMP class permits 16= -bit jump offset while -BPF_JMP32 permits 32-bit jump offset. A >16bit conditional jmp can be co= nverted to a <16bit -conditional jmp plus a 32-bit unconditional jump. +Note that there are two flavors of ``BPF_JA`` instructions. The +``BPF_JMP`` class permits a 16-bit jump offset specified by 'offset' +field, whereas the ``BPF_JMP32`` class permits a 32-bit jump offset +specified by the 'imm' field. A > 16-bit conditional jump may be +converted to a < 16-bit conditional jump plus a 32-bit unconditional +jump. =20 Helper functions ~~~~~~~~~~~~~~~~ @@ -385,7 +395,7 @@ instructions that transfer data between a register an= d memory. dst =3D *(unsigned size *) (src + offset) =20 Where size is one of: ``BPF_B``, ``BPF_H``, ``BPF_W``, or ``BPF_DW`` and -'unsigned size' is one of u8, u16, u32 and u64. +'unsigned size' is one of u8, u16, u32 or u64. =20 The ``BPF_MEMSX`` mode modifier is used to encode sign-extension load instructions that transfer data between a register and memory. @@ -395,7 +405,7 @@ instructions that transfer data between a register an= d memory. dst =3D *(signed size *) (src + offset) =20 Where size is one of: ``BPF_B``, ``BPF_H`` or ``BPF_W``, and -'signed size' is one of s8, s16 and s32. +'signed size' is one of s8, s16 or s32. =20 Atomic operations ----------------- --=20 2.34.1 From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AF2A923B8 for ; Fri, 28 Jul 2023 18:59:19 +0000 (UTC) Received: from mail.ietf.org (mail.ietf.org [50.223.129.194]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 353B830F7 for ; Fri, 28 Jul 2023 11:59:18 -0700 (PDT) Received: from ietfa.amsl.com (localhost [IPv6:::1]) by ietfa.amsl.com (Postfix) with ESMTP id 01B44C16951F for ; Fri, 28 Jul 2023 11:59:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ietf.org; s=ietf1; t=1690570758; bh=a0vIwSsZOicQK1imobI4lXb9MbNeAzXw4xSq+USQYD4=; h=From:To:Cc:Date:Subject:List-Id:List-Unsubscribe:List-Archive: List-Post:List-Help:List-Subscribe; b=f4P4QAXPSDxxIp1EENskYAZZAdu6hP0ToLjzpJ7788xFDQbilE53luJIcqqwEgi6S Yjg4DvCXCRpY8qF27/v1EYy/O7cXf3s9ck6LZ7BVsKkwiwkiaExgihwDjPn1C6yP1w TrvExVY382ty4iTMftJSDVHZGc/5QMzjhs7C7nj8= X-Mailbox-Line: From bpf-bounces@ietf.org Fri Jul 28 11:59:17 2023 Received: from ietfa.amsl.com (localhost [IPv6:::1]) by ietfa.amsl.com (Postfix) with ESMTP id C1543C1519A3; Fri, 28 Jul 2023 11:59:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ietf.org; s=ietf1; t=1690570757; bh=a0vIwSsZOicQK1imobI4lXb9MbNeAzXw4xSq+USQYD4=; h=From:To:Cc:Date:Subject:List-Id:List-Unsubscribe:List-Archive: List-Post:List-Help:List-Subscribe; b=nauWTQT1N1Ldkz6arEvlYbEvqiLElB2PC7Uzi5XSJ1DKZ5NQv584M91UGY22fnn27 VJ0DTxBIAKaX0/nysCwQDFEP5QAYNxx8s1ypzR7pn6O2qWnsytXofDPGHxYOvNPBI/ aEk64WJqvmpwK8Eom/m5X5dP86rouwjRczq/3HuA= Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 56C6FC1516F2 for ; Fri, 28 Jul 2023 11:59:16 -0700 (PDT) X-Virus-Scanned: amavisd-new at amsl.com X-Spam-Score: -0.261 X-Spam-Level: X-Spam-Status: No, score=-2.8 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_EF,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_BLOCKED,RCVD_IN_MSPIKE_H4, RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 Received: from mail.ietf.org ([50.223.129.194]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id d87fq1sXxqtm for ; Fri, 28 Jul 2023 11:59:11 -0700 (PDT) Received: from 69-171-232-180.mail-mxout.facebook.com (69-171-232-180.mail-mxout.facebook.com [69.171.232.180]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 170A8C151B18 for ; Fri, 28 Jul 2023 11:59:07 -0700 (PDT) Received: by devbig309.ftw3.facebook.com (Postfix, from userid 128203) id E451723D27EB4; Fri, 28 Jul 2023 11:58:52 -0700 (PDT) From: Yonghong Song To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , kernel-team@fb.com, Martin KaFai Lau , bpf@ietf.org, David Vernet Date: Fri, 28 Jul 2023 11:58:52 -0700 Message-ID: <20230728185852.3572290-1-yonghong.song@linux.dev> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Archived-At: Subject: [Bpf] [PATCH bpf-next] docs/bpf: Improve documentation for cpu=v4 instructions X-BeenThere: bpf@ietf.org X-Mailman-Version: 2.1.39 Precedence: list List-Id: Discussion of BPF/eBPF standardization efforts within the IETF List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: bpf-bounces@ietf.org Sender: "Bpf" X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Message-ID: <20230728185852.MLpGtfTEYGsaj2ELkUSGso9QnTYngWcstwZMu8FBd3M@z> Improve documentation for cpu=v4 instructions based on David's suggestions. Cc: bpf@ietf.org Suggested-by: David Vernet Signed-off-by: Yonghong Song --- .../bpf/standardization/instruction-set.rst | 54 +++++++++++-------- 1 file changed, 32 insertions(+), 22 deletions(-) diff --git a/Documentation/bpf/standardization/instruction-set.rst b/Documentation/bpf/standardization/instruction-set.rst index 23e880a83a1f..95079a53a35b 100644 --- a/Documentation/bpf/standardization/instruction-set.rst +++ b/Documentation/bpf/standardization/instruction-set.rst @@ -174,7 +174,7 @@ BPF_MOV 0xb0 0 dst = src BPF_MOVSX 0xb0 8/16/32 dst = (s8,s16,s32)src BPF_ARSH 0xc0 0 sign extending dst >>= (src & mask) BPF_END 0xd0 0 byte swap operations (see `Byte swap instructions`_ below) -======== ===== ============ ========================================================== +======== ===== ======= ========================================================== Underflow and overflow are allowed during arithmetic operations, meaning the 64-bit or 32-bit value will wrap. If eBPF program execution would @@ -201,26 +201,32 @@ where '(u32)' indicates that the upper 32 bits are zeroed. dst = dst ^ imm32 -Note that most instructions have instruction offset of 0. But three instructions -(BPF_SDIV, BPF_SMOD, BPF_MOVSX) have non-zero offset. +Note that most instructions have instruction offset of 0. Only three instructions +(``BPF_SDIV``, ``BPF_SMOD``, ``BPF_MOVSX``) have a non-zero offset. The devision and modulo operations support both unsigned and signed flavors. -For unsigned operation (BPF_DIV and BPF_MOD), for ``BPF_ALU``, 'imm' is first -interpreted as an unsigned 32-bit value, whereas for ``BPF_ALU64``, 'imm' is -first sign extended to 64 bits and the result interpreted as an unsigned 64-bit -value. For signed operation (BPF_SDIV and BPF_SMOD), for ``BPF_ALU``, 'imm' is -interpreted as a signed value. For ``BPF_ALU64``, the 'imm' is sign extended -from 32 to 64 and interpreted as a signed 64-bit value. -Instruction BPF_MOVSX does move operation with sign extension. -``BPF_ALU | MOVSX`` sign extendes 8-bit and 16-bit into 32-bit and upper 32-bit are zeroed. -``BPF_ALU64 | MOVSX`` sign extends 8-bit, 16-bit and 32-bit into 64-bit. +For unsigned operations (``BPF_DIV`` and ``BPF_MOD``), for ``BPF_ALU``, +'imm' is interpreted as a 32-bit unsigned value. For ``BPF_ALU64``, +'imm' is first sign extended from 32 to 64 bits, and then interpreted as +a 64-bit unsigned value. + +For signed operations (``BPF_SDIV`` and ``BPF_SMOD``), for ``BPF_ALU``, +'imm' is interpreted as a 32-bit signed value. For ``BPF_ALU64``, 'imm' +is first sign extended from 32 to 64 bits, and then interpreted as a +64-bit signed value. + +The ``BPF_MOVSX`` instruction does a move operation with sign extension. +``BPF_ALU | BPF_MOVSX`` sign extends 8-bit and 16-bit operands into 32 +bit operands, and zeroes the remaining upper 32 bits. +``BPF_ALU64 | BPF_MOVSX`` sign extends 8-bit, 16-bit, and 32-bit +operands into 64 bit operands. Shift operations use a mask of 0x3F (63) for 64-bit operations and 0x1F (31) for 32-bit operations. Byte swap instructions -~~~~~~~~~~~~~~~~~~~~~~ +---------------------- The byte swap instructions use instruction classes of ``BPF_ALU`` and ``BPF_ALU64`` and a 4-bit 'code' field of ``BPF_END``. @@ -228,16 +234,17 @@ and a 4-bit 'code' field of ``BPF_END``. The byte swap instructions operate on the destination register only and do not use a separate source register or immediate value. -For ``BPF_ALU``, the 1-bit source operand field in the opcode is used to select what byte -order the operation convert from or to. For ``BPF_ALU64``, the 1-bit source operand -field in the opcode is not used and must be 0. +For ``BPF_ALU``, the 1-bit source operand field in the opcode is used to +select what byte order the operation converts from or to. For +``BPF_ALU64``, the 1-bit source operand field in the opcode is reserved +and must be set to 0. ========= ========= ===== ================================================= class source value description ========= ========= ===== ================================================= BPF_ALU BPF_TO_LE 0x00 convert between host byte order and little endian BPF_ALU BPF_TO_BE 0x08 convert between host byte order and big endian -BPF_ALU64 BPF_TO_LE 0x00 do byte swap unconditionally +BPF_ALU64 Reserved 0x00 do byte swap unconditionally ========= ========= ===== ================================================= The 'imm' field encodes the width of the swap operations. The following widths @@ -305,9 +312,12 @@ where 's>=' indicates a signed '>=' comparison. where 'imm' means the branch offset comes from insn 'imm' field. -Note there are two flavors of BPF_JA instrions. BPF_JMP class permits 16-bit jump offset while -BPF_JMP32 permits 32-bit jump offset. A >16bit conditional jmp can be converted to a <16bit -conditional jmp plus a 32-bit unconditional jump. +Note that there are two flavors of ``BPF_JA`` instructions. The +``BPF_JMP`` class permits a 16-bit jump offset specified by 'offset' +field, whereas the ``BPF_JMP32`` class permits a 32-bit jump offset +specified by the 'imm' field. A > 16-bit conditional jump may be +converted to a < 16-bit conditional jump plus a 32-bit unconditional +jump. Helper functions ~~~~~~~~~~~~~~~~ @@ -385,7 +395,7 @@ instructions that transfer data between a register and memory. dst = *(unsigned size *) (src + offset) Where size is one of: ``BPF_B``, ``BPF_H``, ``BPF_W``, or ``BPF_DW`` and -'unsigned size' is one of u8, u16, u32 and u64. +'unsigned size' is one of u8, u16, u32 or u64. The ``BPF_MEMSX`` mode modifier is used to encode sign-extension load instructions that transfer data between a register and memory. @@ -395,7 +405,7 @@ instructions that transfer data between a register and memory. dst = *(signed size *) (src + offset) Where size is one of: ``BPF_B``, ``BPF_H`` or ``BPF_W``, and -'signed size' is one of s8, s16 and s32. +'signed size' is one of s8, s16 or s32. Atomic operations ----------------- -- 2.34.1 -- Bpf mailing list Bpf@ietf.org https://www.ietf.org/mailman/listinfo/bpf