From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35867) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YAaKZ-0006gv-HV for qemu-devel@nongnu.org; Mon, 12 Jan 2015 03:26:36 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YAaKW-0002Rc-Az for qemu-devel@nongnu.org; Mon, 12 Jan 2015 03:26:35 -0500 Received: from mail.ispras.ru ([83.149.199.45]:43307) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YAaKW-0002QK-39 for qemu-devel@nongnu.org; Mon, 12 Jan 2015 03:26:32 -0500 From: "Pavel Dovgaluk" References: <20141022113831.9548.36452.stgit@PASHA-ISP> <54B37FCA.4020805@siemens.com> In-Reply-To: <54B37FCA.4020805@siemens.com> Date: Mon, 12 Jan 2015 11:26:27 +0300 Message-ID: <000801d02e41$75c1a000$6144e000$@Dovgaluk@ispras.ru> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Content-Language: ru Subject: Re: [Qemu-devel] [PATCH] i386: fix breakpoints handling in icount mode List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: 'Jan Kiszka' , qemu-devel@nongnu.org Cc: mark.burton@greensocs.com, batuzovk@ispras.ru, maria.klimushenkova@ispras.ru, pbonzini@redhat.com, zealot351@gmail.com, fred.konrad@greensocs.com > From: Jan Kiszka [mailto:jan.kiszka@siemens.com] > On 2014-10-22 13:38, Pavel Dovgalyuk wrote: > > This patch fixes instructions counting when execution is stopped on > > breakpoint (e.g. set from gdb). Without a patch extra instruction is translated > > and icount is incremented by invalid value (which equals to number of > > executed instructions + 1). > > > > Signed-off-by: Pavel Dovgalyuk > > --- > > target-i386/translate.c | 3 ++- > > 1 files changed, 2 insertions(+), 1 deletions(-) > > > > diff --git a/target-i386/translate.c b/target-i386/translate.c > > index 1284173..193cf9f 100644 > > --- a/target-i386/translate.c > > +++ b/target-i386/translate.c > > @@ -8000,7 +8000,7 @@ static inline void gen_intermediate_code_internal(X86CPU *cpu, > > if (bp->pc == pc_ptr && > > !((bp->flags & BP_CPU) && (tb->flags & HF_RF_MASK))) { > > gen_debug(dc, pc_ptr - dc->cs_base); > > - break; > > + goto done_generating; > > } > > } > > } > > @@ -8049,6 +8049,7 @@ static inline void gen_intermediate_code_internal(X86CPU *cpu, > > break; > > } > > } > > +done_generating: > > if (tb->cflags & CF_LAST_IO) > > gen_io_end(); > > gen_tb_end(tb, num_insns); > > > > > > > > Didn't looked into why, just bisected that this patch breaks at least > certain guest-originated break- or watchpoints in TCG mode. Can be > triggered by booting a Linux kernel with kgdb self-tests enabled. The > result is some false reporting of a host-originated debug stop to > gdb_set_stop_cpu while gdbserver_state is NULL -> SEGV. It seems that kernel sets some hardware breakpoints and QEMU tries to process them with GDB stub. Modifying gdb_set_stop_cpu should help: diff --git a/gdbstub.c b/gdbstub.c index e4a1a79..e8ef546 100644 --- a/gdbstub.c +++ b/gdbstub.c @@ -1202,8 +1202,10 @@ static int gdb_handle_packet(GDBState *s, const char *line_buf) void gdb_set_stop_cpu(CPUState *cpu) { - gdbserver_state->c_cpu = cpu; - gdbserver_state->g_cpu = cpu; + if (gdbserver_state) { + gdbserver_state->c_cpu = cpu; + gdbserver_state->g_cpu = cpu; + } } #ifndef CONFIG_USER_ONLY Pavel Dovgalyuk