From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from hqnvemgate24.nvidia.com (hqnvemgate24.nvidia.com [216.228.121.143]) by sourceware.org (Postfix) with ESMTPS id E25EB3947C24 for ; Thu, 11 Jun 2020 22:56:42 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org E25EB3947C24 Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate24.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Thu, 11 Jun 2020 15:55:08 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Thu, 11 Jun 2020 15:56:42 -0700 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Thu, 11 Jun 2020 15:56:42 -0700 Received: from nvbus.nvidia.com (10.124.1.5) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Thu, 11 Jun 2020 22:56:41 +0000 From: Victor Collod To: Subject: [PATCH v2 2/2] Refactor amd64_analyze_prologue Date: Thu, 11 Jun 2020 15:54:55 -0700 Message-ID: <20200611225455.9354-3-vcollod@nvidia.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200611225455.9354-1-vcollod@nvidia.com> References: <0c2e7c13-3a10-0f83-955b-e08dcd628d17@simark.ca> <20200611225455.9354-1-vcollod@nvidia.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL101.nvidia.com (172.20.187.10) To HQMAIL107.nvidia.com (172.20.187.13) X-Spam-Status: No, score=-10.6 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: gdb-patches@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gdb-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 11 Jun 2020 22:56:44 -0000 * merge op and the buf array, which were both used for storing code * invert conditions to avoid long nested ifs * use target_read_code instead of read_code to gracefully handle errors * `if (current_pc <=3D pc)' felt backwards, as current_pc doesn't change, and the test could be described as "stop if pc went past current_pc" 2020-06-11 Victor Collod * amd64-tdep.c (amd64_analyze_prologue): Make the function more readable. --- gdb/amd64-tdep.c | 93 ++++++++++++++++++++++++++---------------------- 1 file changed, 50 insertions(+), 43 deletions(-) diff --git a/gdb/amd64-tdep.c b/gdb/amd64-tdep.c index 0ce9fbc2997..6c1a4a138de 100644 --- a/gdb/amd64-tdep.c +++ b/gdb/amd64-tdep.c @@ -2374,7 +2374,6 @@ amd64_analyze_prologue (struct gdbarch *gdbarch, CORE_ADDR pc, CORE_ADDR current_pc, struct amd64_frame_cache *cache) { - enum bfd_endian byte_order =3D gdbarch_byte_order (gdbarch); /* The `endbr64` instruction. */ static const gdb_byte endbr64[4] =3D { 0xf3, 0x0f, 0x1e, 0xfa }; /* There are two variations of movq %rsp, %rbp. */ @@ -2384,10 +2383,10 @@ amd64_analyze_prologue (struct gdbarch *gdbarch, static const gdb_byte mov_esp_ebp_1[2] =3D { 0x89, 0xe5 }; static const gdb_byte mov_esp_ebp_2[2] =3D { 0x8b, 0xec }; =20 - gdb_byte buf[3]; - gdb_byte op; + gdb_byte buf[4]; =20 - if (current_pc <=3D pc) + /* Analysis must not go past current_pc */ + if (pc >=3D current_pc) return current_pc; =20 if (gdbarch_ptr_bit (gdbarch) =3D=3D 32) @@ -2395,57 +2394,65 @@ amd64_analyze_prologue (struct gdbarch *gdbarch, else pc =3D amd64_analyze_stack_align (pc, current_pc, cache); =20 - op =3D read_code_unsigned_integer (pc, 1, byte_order); - - /* Check for the `endbr64` instruction, skip it if found. */ - if (op =3D=3D endbr64[0]) + /* Try to read enough bytes to check for `endbr64' */ + if (target_read_code (pc, buf, 4) !=3D 0) + { + /* If it fails, read just enough data for `pushq %rbp' */ + if (target_read_code (pc, buf, 1) !=3D 0) + return pc; + } + /* If reading succeeded, check for the `endbr64' instruction and skip it= if found. */ + else if (memcmp (buf, endbr64, sizeof (endbr64)) =3D=3D 0) { - read_code (pc + 1, buf, 3); + pc +=3D sizeof (endbr64); + /* If we went past the allowed bound, stop */ + if (pc >=3D current_pc) + return current_pc; + /* update the code buffer, as pc changed */ + if (target_read_code (pc, buf, 1) !=3D 0) + return pc; + } =20 - if (memcmp (buf, &endbr64[1], 3) =3D=3D 0) - pc +=3D 4; + /* stop right now if there's no `pushq %rbp' */ + if (buf[0] !=3D 0x55) + return pc; =20 - op =3D read_code_unsigned_integer (pc, 1, byte_order); - } + /* Take into account that we've executed the `pushq %rbp' that + starts this instruction sequence. */ + cache->saved_regs[AMD64_RBP_REGNUM] =3D 0; + cache->sp_offset +=3D 8; =20 - if (current_pc <=3D pc) - return current_pc; + pc +=3D 1; =20 - if (op =3D=3D 0x55) /* pushq %rbp */ - { - /* Take into account that we've executed the `pushq %rbp' that - starts this instruction sequence. */ - cache->saved_regs[AMD64_RBP_REGNUM] =3D 0; - cache->sp_offset +=3D 8; + /* If we went past the allowed bound, stop */ + if (pc >=3D current_pc) + return current_pc; =20 - /* If that's all, return now. */ - if (current_pc <=3D pc + 1) - return current_pc; + /* Try to read the code for the stack base move */ + if (target_read_code (pc, buf, 3) !=3D 0) + return pc; =20 - read_code (pc + 1, buf, 3); + /* Check for `movq %rsp, %rbp'. */ + if (memcmp (buf, mov_rsp_rbp_1, 3) =3D=3D 0 + || memcmp (buf, mov_rsp_rbp_2, 3) =3D=3D 0) + { + pc +=3D 3; + /* OK, we actually have a frame. */ + cache->frameless_p =3D 0; + return pc; + } =20 - /* Check for `movq %rsp, %rbp'. */ - if (memcmp (buf, mov_rsp_rbp_1, 3) =3D=3D 0 - || memcmp (buf, mov_rsp_rbp_2, 3) =3D=3D 0) + /* For X32, also check for `movl %esp, %ebp'. */ + if (gdbarch_ptr_bit (gdbarch) =3D=3D 32) + { + if (memcmp (buf, mov_esp_ebp_1, 2) =3D=3D 0 + || memcmp (buf, mov_esp_ebp_2, 2) =3D=3D 0) { + pc +=3D 2; /* OK, we actually have a frame. */ cache->frameless_p =3D 0; - return pc + 4; + return pc; } - - /* For X32, also check for `movq %esp, %ebp'. */ - if (gdbarch_ptr_bit (gdbarch) =3D=3D 32) - { - if (memcmp (buf, mov_esp_ebp_1, 2) =3D=3D 0 - || memcmp (buf, mov_esp_ebp_2, 2) =3D=3D 0) - { - /* OK, we actually have a frame. */ - cache->frameless_p =3D 0; - return pc + 3; - } - } - - return pc + 1; } =20 return pc; --=20 2.20.1