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([2804:7f0:b403:ad57:3e7c:3fff:fe7a:e83b]) by smtp.gmail.com with ESMTPSA id n18-20020a170903111200b001e0b5eee802sm1925524plh.123.2024.04.18.13.11.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 18 Apr 2024 13:11:09 -0700 (PDT) From: Gustavo Romero To: gdb-patches@sourceware.org Cc: luis.machado@arm.com, thiago.bauermann@linaro.org, eliz@gnu.org, tom@tromey.com, gustavo.romero@linaro.org Subject: [PATCH v6 6/8] gdb: Add qIsAddressTagged packet Date: Thu, 18 Apr 2024 20:10:37 +0000 Message-Id: <20240418201039.236867-7-gustavo.romero@linaro.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240418201039.236867-1-gustavo.romero@linaro.org> References: <20240418201039.236867-1-gustavo.romero@linaro.org> MIME-Version: 1.0 X-Spam-Status: No, score=-13.1 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: gdb-patches@sourceware.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Gdb-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: gdb-patches-bounces+patchwork=sourceware.org@sourceware.org This commit adds a new packet, qIsAddressTagged, allowing GDB remote targets to use it to query the stub if a given address is tagged. Currently, the memory tagging address check is done via a read query, where the contents of /proc//smaps is read and the flags are inspected for memory tagging-related flags that indicate the address is in a memory tagged region. This is not ideal, for example, for QEMU stub and other cases, such as on bare-metal, where there is no notion of an OS file like 'smaps.' Hence, the introduction of qIsAddressTagged packet allows checking if an address is tagged in an agnostic way. The is_address_tagged target hook in remote.c attempts to use the qIsAddressTagged packet first for checking if an address is tagged and if the stub does not support such a packet (reply is empty) it falls back to using the current mechanism that reads the contents of /proc//smaps via vFile requests. Signed-off-by: Gustavo Romero Tested-By: Luis Machado --- gdb/remote.c | 75 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 75 insertions(+) diff --git a/gdb/remote.c b/gdb/remote.c index cd271c4b493..3d034bb1ef8 100644 --- a/gdb/remote.c +++ b/gdb/remote.c @@ -337,6 +337,9 @@ enum { packets and the tag violation stop replies. */ PACKET_memory_tagging_feature, + /* Support for the qIsAddressTagged packet. */ + PACKET_qIsAddressTagged, + PACKET_MAX }; @@ -15535,6 +15538,50 @@ create_store_memtags_request (gdb::char_vector &packet, CORE_ADDR address, strcpy (packet.data (), request.c_str ()); } +static void +create_is_address_tagged_request (gdbarch *gdbarch, gdb::char_vector &packet, + CORE_ADDR address) +{ + int addr_size; + std::string request; + + addr_size = gdbarch_addr_bit (gdbarch) / 8; + request = string_printf ("qIsAddressTagged:%s", phex_nz (address, addr_size)); + + if (packet.size () < request.length () + 1) + error (_("Contents too big for packet qIsAddressTagged.")); + + strcpy (packet.data (), request.c_str ()); +} + +static bool +check_is_address_tagged_reply (remote_target *remote, gdb::char_vector &packet, + bool &tagged) +{ + gdb_assert (remote != nullptr); + /* Check reply and disable qIsAddressTagged usage if it's not supported. */ + packet_result result = remote->m_features.packet_ok (packet, + PACKET_qIsAddressTagged); + + /* Return false on error (Exx), empty reply (packet not supported), or reply + size doesn't match 2 hex digits. */ + if ((result.status () != PACKET_OK) || (strlen (packet.data ()) != 2)) + return false; + + gdb_byte reply; + /* Convert only 2 hex digits, i.e. 1 byte in hex format. */ + hex2bin (packet.data (), &reply, 1); + + if (reply == 0x00 || reply == 0x01) + { + tagged = !!reply; + return true; + } + + /* Invalid reply. */ + return false; +} + /* Implement the "fetch_memtags" target_ops method. */ bool @@ -15581,6 +15628,31 @@ remote_target::store_memtags (CORE_ADDR address, size_t len, bool remote_target::is_address_tagged (gdbarch *gdbarch, CORE_ADDR address) { + /* Firstly, attempt to check the address using the qIsAddressTagged + packet. */ + if (m_features.packet_support (PACKET_qIsAddressTagged) != PACKET_DISABLE) + { + remote_target *remote = get_current_remote_target (); + struct remote_state *rs = get_remote_state (); + bool is_addr_tagged; + + create_is_address_tagged_request (gdbarch, rs->buf, address); + + putpkt (rs->buf); + getpkt (&rs->buf); + + /* If qIsAddressTagged is not supported PACKET_qIsAddressTagged will be + set to PACKET_DISABLE so no further attempt is made to check addresses + using this packet and the fallback mechanism below will be used + instead. Also, if the check fails due to an error (Exx reply) the + fallback is used too. Otherwise, the qIsAddressTagged query succeeded + and is_addr_tagged is valid. */ + if (check_is_address_tagged_reply (remote, rs->buf, is_addr_tagged)) + return is_addr_tagged; + } + + /* Fallback to arch-specific method of checking whether an address is tagged + in case check via qIsAddressTagged fails. */ return gdbarch_tagged_address_p (gdbarch, address); } @@ -16070,6 +16142,9 @@ Show the maximum size of the address (in bits) in a memory packet."), NULL, add_packet_config_cmd (PACKET_memory_tagging_feature, "memory-tagging-feature", "memory-tagging-feature", 0); + add_packet_config_cmd (PACKET_qIsAddressTagged, + "qIsAddressTagged", "memory-tagging-address-check", 0); + /* Assert that we've registered "set remote foo-packet" commands for all packet configs. */ {