From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 6121 invoked by alias); 17 Nov 2014 07:23:12 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Received: (qmail 6111 invoked by uid 89); 17 Nov 2014 07:23:10 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.1 required=5.0 tests=AWL,BAYES_00,FREEMAIL_ENVFROM_END_DIGIT,FREEMAIL_FROM,RCVD_IN_DNSWL_LOW,SPF_PASS autolearn=ham version=3.3.2 X-HELO: mail-yk0-f180.google.com Received: from mail-yk0-f180.google.com (HELO mail-yk0-f180.google.com) (209.85.160.180) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES128-SHA encrypted) ESMTPS; Mon, 17 Nov 2014 07:23:09 +0000 Received: by mail-yk0-f180.google.com with SMTP id 9so3822566ykp.11 for ; Sun, 16 Nov 2014 23:23:07 -0800 (PST) MIME-Version: 1.0 X-Received: by 10.236.61.6 with SMTP id v6mr824970yhc.44.1416208986902; Sun, 16 Nov 2014 23:23:06 -0800 (PST) Received: by 10.170.81.68 with HTTP; Sun, 16 Nov 2014 23:23:06 -0800 (PST) In-Reply-To: References: <1409238683-17886-1-git-send-email-teawater@gmail.com> Date: Mon, 17 Nov 2014 07:23:00 -0000 Message-ID: Subject: Re: [PATCH] Add gdbarch_sizeof_g_packet to "struct remote_arch_state" to handle the issue that get error "Remote 'g' packet reply is too long" with qemu-system-x86_64 From: Doug Evans To: Hui Zhu Cc: gdb-patches ml Content-Type: text/plain; charset=UTF-8 X-IsSubscribed: yes X-SW-Source: 2014-11/txt/msg00396.txt.bz2 On Sun, Nov 16, 2014 at 11:08 PM, Hui Zhu wrote: > Ping. > > Or I just enjoy it with myself. :P > > Thanks, > Hui > > On Tue, Sep 2, 2014 at 11:26 AM, Hui Zhu wrote: >> Ping. >> >> Thanks, >> Hui >> >> On Thu, Aug 28, 2014 at 11:11 PM, Hui Zhu wrote: >>> If qemu-system-x86_64 start with -S, gdb will get error "Remote 'g' packet reply >>> is too long", for example: >>> sudo qemu-system-x86_64 -nographic -k en-us -kernel /boot/vmlinuz-3.13.0-34-generic -gdb tcp::12345 -append "console=ttyS0,115200 root=/dev/sda rw kmemleak=off" -S -m 512 -smp 1 >>> gdb /usr/lib/debug/boot/vmlinux-$(uname -r) >>> (gdb) set debug remote 1 >>> (gdb) target remote :12345 >>> ... >>> ... >>> Sending packet: $g#67...Ack >>> Packet received: 0000000000000000630600000000000000000000000000000000000 >>> 000000000f0ff00000200000000f00000000000000000000000000000000000000000000 >>> 000000000000000000000000000000000000000000000000000000000000000000000000 >>> 000000000000000000000000000000000000000000000000000000000000000000000000 >>> 000000000000000007f03000000000000000000000000000000000000000000000000000 >>> 000000000000000000000000000000000000000000000000000000000000000000000000 >>> 000000000000000000000000000000000000000000000000000000000000000000000000 >>> 000000000000000000000000000000000000000000000000000000000000000000000000 >>> 0000000000000000000000000000000000000000000000000801f0000 >>> (gdb) b start_kernel >>> (gdb) c >>> Continuing. >>> ... >>> ... >>> Sending packet: $g#67...Ack >>> Packet received: 0000000000000000d381ffffffff000040000000000000000010060 >>> 00000000000f009000000000010f4ce81ffffffff981fc081ffffffff901fc081fffffff >>> f0030c1010000000000000000000000000000000000000000a869270200000000fffffff >>> f0000000020000000000000002051d381ffffffffb01fc081ffffffff385bd381fffffff >>> f96000000100000000000000000000000000000000000000000000000000000000000000 >>> 000000000000000000000000000000000000000000000000000000000000000000000000 >>> 000000000000000000000000000000000000000000000000000000000000000000000000 >>> 07f030000000000000000000000000000000000000000000000000000000000000000000 >>> 000000000000000000000000000000000000000000000000000000000000000000000000 >>> 000000000000000000000000000000000000000000000000000000000000000000000000 >>> 000000000000000000000000000000000000000000000000000000000000000000000000 >>> 000000000000000000000000000000000000000000000000000000000000000000000000 >>> 000000000000000000000000000000000000000000000000000000000000000000000000 >>> 000000000000000000000000000000000000000000000000000000000000000000000000 >>> 000000000000000000000000000000000000000000000000000000000000000000000000 >>> 0801f0000 >>> Remote 'g' packet reply is too long: 0000000000000000d381ffffffff0000400 >>> 0000000000000001006000000000000f009000000000010f4ce81ffffffff981fc081fff >>> fffff901fc081ffffffff0030c1010000000000000000000000000000000000000000a86 >>> 9270200000000ffffffff0000000020000000000000002051d381ffffffffb01fc081fff >>> fffff385bd381ffffffff960000001000000000000000000000000000000000000000000 >>> 000000000000000000000000000000000000000000000000000000000000000000000000 >>> 000000000000000000000000000000000000000000000000000000000000000000000000 >>> 0000000000000000000007f0300000000000000000000000000000000000000000000000 >>> 000000000000000000000000000000000000000000000000000000000000000000000000 >>> 000000000000000000000000000000000000000000000000000000000000000000000000 >>> 000000000000000000000000000000000000000000000000000000000000000000000000 >>> 000000000000000000000000000000000000000000000000000000000000000000000000 >>> 000000000000000000000000000000000000000000000000000000000000000000000000 >>> 000000000000000000000000000000000000000000000000000000000000000000000000 >>> 000000000000000000000000000000000000000000000000000000000000000000000000 >>> 000000000000000000000801f0000 >>> (gdb) c >>> Continuing. >>> Cannot execute this command while the selected thread is running. >>> >>> The root cause of this issue is: >>> When GDB load a debug binary, function init_remote_state will be called and >>> rsa->sizeof_g_packet will be initialized. >>> /* Record the maximum possible size of the g packet - it may turn out >>> to be smaller. */ >>> rsa->sizeof_g_packet = map_regcache_remote_table (gdbarch, rsa->regs); >>> When remote.c get first reply of g that its size is smaller than >>> rsa->sizeof_g_packet in function process_g_packet, sizeof_g_packet will be >>> updated to this smaller size. >>> rsa->sizeof_g_packet = buf_len / 2; >>> When inferior is breaked by breakpoint, because some reason architecture reason, >>> QEMU send a packet for "g" that is more bigger than previous one. Then GDB will >>> get error in function process_g_packet. >>> /* Further sanity checks, with knowledge of the architecture. */ >>> if (buf_len > 2 * rsa->sizeof_g_packet) >>> error (_("Remote 'g' packet reply is too long: %s"), rs->buf); >>> >>> To handle this issue: >>> This patch add "gdbarch_sizeof_g_packet" to "struct remote_arch_state", it will >>> keep the size of g packet that get from gdbarch. And function process_g_packet >>> use it do the check for the reply of "g". And update sizeof_g_packet if it is >>> not same with reply of "g". >>> >>> 2014-08-21 Hui Zhu >>> >>> * remote.c (struct remote_arch_state): Add gdbarch_sizeof_g_packet. >>> (init_remote_state): Initialize rsa->gdbarch_sizeof_g_packet. >>> (process_g_packet): Check buf_len with rsa->gdbarch_sizeof_g_packet. >>> Update code to update rsa->sizeof_g_packet if buf_len is not for it. >>> --- >>> gdb/remote.c | 18 ++++++++++++------ >>> 1 file changed, 12 insertions(+), 6 deletions(-) >>> >>> diff --git a/gdb/remote.c b/gdb/remote.c >>> index 357e9f2..9727915 100644 >>> --- a/gdb/remote.c >>> +++ b/gdb/remote.c >>> @@ -439,6 +439,11 @@ struct remote_arch_state >>> /* Description of the remote protocol registers. */ >>> long sizeof_g_packet; >>> >>> + /* The sizeof_g_packet will be changed in some GDBstub (QEMU) when it executes. >>> + Description of the remote protocol registers that get form current >>> + gdbarch. */ >>> + long gdbarch_sizeof_g_packet; >>> + >>> /* Description of the remote protocol registers indexed by REGNUM >>> (making an array gdbarch_num_regs in size). */ >>> struct packet_reg *regs; >>> @@ -673,7 +678,8 @@ init_remote_state (struct gdbarch *gdbarch) >>> >>> /* Record the maximum possible size of the g packet - it may turn out >>> to be smaller. */ >>> - rsa->sizeof_g_packet = map_regcache_remote_table (gdbarch, rsa->regs); >>> + rsa->gdbarch_sizeof_g_packet = map_regcache_remote_table (gdbarch, rsa->regs); >>> + rsa->sizeof_g_packet = rsa->gdbarch_sizeof_g_packet; >>> >>> /* Default maximum number of characters in a packet body. Many >>> remote stubs have a hardwired buffer size of 400 bytes >>> @@ -693,8 +699,8 @@ init_remote_state (struct gdbarch *gdbarch) >>> header / footer. NOTE: cagney/1999-10-26: I suspect that 8 >>> (``$NN:G...#NN'') is a better guess, the below has been padded a >>> little. */ >>> - if (rsa->sizeof_g_packet > ((rsa->remote_packet_size - 32) / 2)) >>> - rsa->remote_packet_size = (rsa->sizeof_g_packet * 2 + 32); >>> + if (rsa->gdbarch_sizeof_g_packet > ((rsa->remote_packet_size - 32) / 2)) >>> + rsa->remote_packet_size = (rsa->gdbarch_sizeof_g_packet * 2 + 32); >>> >>> /* Make sure that the packet buffer is plenty big enough for >>> this architecture. */ >>> @@ -6070,7 +6076,7 @@ process_g_packet (struct regcache *regcache) >>> buf_len = strlen (rs->buf); >>> >>> /* Further sanity checks, with knowledge of the architecture. */ >>> - if (buf_len > 2 * rsa->sizeof_g_packet) >>> + if (buf_len > 2 * rsa->gdbarch_sizeof_g_packet) >>> error (_("Remote 'g' packet reply is too long: %s"), rs->buf); >>> >>> /* Save the size of the packet sent to us by the target. It is used >>> @@ -6079,11 +6085,11 @@ process_g_packet (struct regcache *regcache) >>> if (rsa->actual_register_packet_size == 0) >>> rsa->actual_register_packet_size = buf_len; >>> >>> - /* If this is smaller than we guessed the 'g' packet would be, >>> + /* If this is not same with we guessed the 'g' packet would be, >>> update our records. A 'g' reply that doesn't include a register's >>> value implies either that the register is not available, or that >>> the 'p' packet must be used. */ >>> - if (buf_len < 2 * rsa->sizeof_g_packet) >>> + if (buf_len != 2 * rsa->sizeof_g_packet) >>> { >>> rsa->sizeof_g_packet = buf_len / 2; >>> >>> -- >>> 1.9.3 >>> Hi. When I've used qemu and seen this issue, it's because the inferior has stopped with the current arch different than what gdb thinks. E.g., if I boot linux on qemu and then Ctrl-C, then when qemu talks to gdb it either presents a 32bit or a 64bit arch to gdb, depending on what program qemu was currently running (the kernel may be 64 bit but the kernel can be running a mix of 32bit and 64bit programs). Thus gdb is being presented, randomly, with 32bit or 64bit arches over the same remote connection, which obviously isn't going to work. So I guess my first question is, is this patch just a bandaid? IOW, the problem here is more than just packet size, isn't it? GDB currently doesn't support debugging of i386 and amd64 arches over one remote debug connection.