From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35915) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cTVZb-0004sV-JY for qemu-devel@nongnu.org; Tue, 17 Jan 2017 10:21:24 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cTVZY-000234-FF for qemu-devel@nongnu.org; Tue, 17 Jan 2017 10:21:23 -0500 From: Ziyue Yang Date: Tue, 17 Jan 2017 23:19:51 +0800 Message-Id: <1484666391-15089-1-git-send-email-skiver.cloud.yzy@gmail.com> Subject: [Qemu-devel] [PATCH] gdbstub.c: fix GDB connection segfault caused by empty machines List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org, qemu-trivial@nongnu.org Cc: Paolo Bonzini , Anthony Liguori , Ziyue Yang , Ziyue Yang From: Ziyue Yang This patch is to fix the segmentation fault caused by attaching GDB to a QEMU instance initialized with "-M none" option. The bug can be reproduced by > ./qemu-system-x86_64 -M none -nographic -S -s and attach a GDB to it by > gdb -ex 'target remote :1234 The segmentation fault was originally caused by trying to read the information about CPU when communicating with GDB. However, it's impossible for any control flow to exist on an empty machine, nor can CPU's be hot plugged to an empty machine later by QOM commands. So I think simply disabling GDB connections on empty machines makes sense. Signed-off-by: Ziyue Yang --- gdbstub.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/gdbstub.c b/gdbstub.c index de62d26..413e817 100644 --- a/gdbstub.c +++ b/gdbstub.c @@ -1731,6 +1731,12 @@ int gdbserver_start(const char *device) CharDriverState *mon_chr; ChardevCommon common = { 0 }; + if (!first_cpu) { + fprintf(stderr, "gdbstub: meaningless to attach gdb to a " + "machine without any CPU.\n"); + return -1; + } + if (!device) return -1; if (strcmp(device, "none") != 0) { -- 2.7.4