From 508b4ecc3935f0cffb6f8e302fb84941dae940c9 Mon Sep 17 00:00:00 2001 From: Ziyue Yang Date: Wed, 18 Jan 2017 16:02:41 +0800 Subject: [PATCH] gdbstub.c: fix GDB connection segfault caused by empty machines 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 Reviewed-by: Thomas Huth Signed-off-by: Michael Tokarev --- gdbstub.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/gdbstub.c b/gdbstub.c index de9b62b8f8..27e0923781 100644 --- a/gdbstub.c +++ b/gdbstub.c @@ -18,6 +18,7 @@ */ #include "qemu/osdep.h" #include "qapi/error.h" +#include "qemu/error-report.h" #include "qemu/cutils.h" #include "cpu.h" #ifdef CONFIG_USER_ONLY @@ -1732,6 +1733,12 @@ int gdbserver_start(const char *device) CharDriverState *mon_chr; ChardevCommon common = { 0 }; + if (!first_cpu) { + error_report("gdbstub: meaningless to attach gdb to a " + "machine without any CPU."); + return -1; + } + if (!device) return -1; if (strcmp(device, "none") != 0) { -- 2.11.4.GIT