From: Richard Henderson <richard.henderson@linaro.org>
To: Laurent Vivier <laurent@vivier.eu>,
Lucien Murray-Pitts <lucienmp_antispam@yahoo.com>,
qemu-devel@nongnu.org
Cc: "Thomas Huth" <huth@tuxfamily.org>,
"Alex Bennée" <alex.bennee@linaro.org>,
"Emilio G . Cota" <cota@braap.org>,
"Luc Michel" <luc.michel@greensocs.com>
Subject: Re: [Qemu-devel] [PATCH] Regression for m68k causing Single-Step via GDB/RSP to not single step
Date: Tue, 18 Jun 2019 12:39:50 -0700 [thread overview]
Message-ID: <1c3d400a-7ea2-2bdd-8301-8f6c85075b24@linaro.org> (raw)
In-Reply-To: <ab1edfe7-8498-eee6-096c-d66d6122d133@vivier.eu>
On 6/18/19 11:44 AM, Laurent Vivier wrote:
> Le 26/05/2019 à 09:50, Lucien Murray-Pitts a écrit :
>> A regression that was introduced, with the refactor to TranslatorOps,
>> drops two lines that update the PC when single-stepping is being performed.
>> ( short commit 11ab74b )
>>
>> This patch resolves that issue.
>
> Fixes: 11ab74b01e0a ("target/m68k: Convert to TranslatorOps")
>
>> Signed-off-by: Lucien Murray-Pitts <lucienmp_antispam@yahoo.com>
>> ---
>> target/m68k/translate.c | 2 ++
>> 1 file changed, 2 insertions(+)
>>
>> diff --git a/target/m68k/translate.c b/target/m68k/translate.c
>> index f0534a4ba0..2922ea79c3 100644
>> --- a/target/m68k/translate.c
>> +++ b/target/m68k/translate.c
>> @@ -6130,6 +6130,8 @@ static void m68k_tr_tb_stop(DisasContextBase *dcbase, CPUState *cpu)
>> return;
>> }
>> if (dc->base.singlestep_enabled) {
>> + update_cc_op(dc);
>> + tcg_gen_movi_i32(QREG_PC, dc->pc);
>> gen_helper_raise_exception(cpu_env, tcg_const_i32(EXCP_DEBUG));
>> return;
>> }
>>
>
> I've tested this fix single-stepping on a kernel, these two lines are
> not enough to fix the problem. In fact four lines have been dropped and
> we must re-add them all:
>
> iff --git a/target/m68k/translate.c b/target/m68k/translate.c
> index d0f6d1f5cc..6c78001501 100644
> --- a/target/m68k/translate.c
> +++ b/target/m68k/translate.c
> @@ -6200,6 +6200,10 @@ static void m68k_tr_tb_stop(DisasContextBase *dcbase, CPUState *cpu)
> return;
> }
> if (dc->base.singlestep_enabled) {
> + if (dc->base.is_jmp != DISAS_JUMP) {
> + update_cc_op(dc);
> + tcg_gen_movi_i32(QREG_PC, dc->pc);
> + }
> gen_helper_raise_exception(cpu_env, tcg_const_i32(EXCP_DEBUG));
> return;
> }
Even this isn't quite right, according to the comments in the switch that
follows. I think it'd be best written like so.
r~
diff --git a/target/m68k/translate.c b/target/m68k/translate.c
index 2ae537461f..b61c7ea0f1 100644
--- a/target/m68k/translate.c
+++ b/target/m68k/translate.c
@@ -6124,27 +6124,34 @@ static void m68k_tr_tb_stop(DisasContextBase *dcbase,
CPUState *cpu)
{
DisasContext *dc = container_of(dcbase, DisasContext, base);
- if (dc->base.is_jmp == DISAS_NORETURN) {
- return;
- }
- if (dc->base.singlestep_enabled) {
- gen_helper_raise_exception(cpu_env, tcg_const_i32(EXCP_DEBUG));
- return;
- }
-
switch (dc->base.is_jmp) {
+ case DISAS_NORETURN:
+ break;
case DISAS_TOO_MANY:
update_cc_op(dc);
- gen_jmp_tb(dc, 0, dc->pc);
+ if (dc->base.singlestep_enabled) {
+ tcg_gen_movi_i32(QREG_PC, dc->pc);
+ gen_helper_raise_exception(cpu_env, tcg_const_i32(EXCP_DEBUG));
+ } else {
+ gen_jmp_tb(dc, 0, dc->pc);
+ }
break;
case DISAS_JUMP:
/* We updated CC_OP and PC in gen_jmp/gen_jmp_im. */
- tcg_gen_lookup_and_goto_ptr();
+ if (dc->base.singlestep_enabled) {
+ gen_helper_raise_exception(cpu_env, tcg_const_i32(EXCP_DEBUG));
+ } else {
+ tcg_gen_lookup_and_goto_ptr();
+ }
break;
case DISAS_EXIT:
/* We updated CC_OP and PC in gen_exit_tb, but also modified
other state that may require returning to the main loop. */
- tcg_gen_exit_tb(NULL, 0);
+ if (dc->base.singlestep_enabled) {
+ gen_helper_raise_exception(cpu_env, tcg_const_i32(EXCP_DEBUG));
+ } else {
+ tcg_gen_exit_tb(NULL, 0);
+ }
break;
default:
g_assert_not_reached();
next prev parent reply other threads:[~2019-06-18 19:41 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-26 7:50 [Qemu-devel] [PATCH] Regression for m68k causing Single-Step via GDB/RSP to not single step Lucien Murray-Pitts via Qemu-devel
2019-05-26 8:27 ` no-reply
2019-05-26 13:07 ` Laurent Vivier
2019-06-18 18:44 ` Laurent Vivier
2019-06-18 19:39 ` Richard Henderson [this message]
2019-06-18 19:58 ` Laurent Vivier
2019-06-26 11:24 ` Lucien Anti-Spam via Qemu-devel
2019-06-26 11:38 ` Laurent Vivier
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