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_antis...@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;
}
The problem happens when we single-step over an "rts" instruction,
instead of returning to the caller the PC points to the following
instruction (PC + 2):
0x00002e26 in arch_cpu_idle ()
1: x/i $pc 0x2e26 <arch_cpu_idle+4>: rts
(gdb) si
0x00002e28 in machine_restart ()
1: x/i $pc 0x2e28 <machine_restart>: moveal 0x438ae4 <mach_reset>,%a0
The good instruction stream is:
0x00002e26 in arch_cpu_idle ()
1: x/i $pc 0x2e26 <arch_cpu_idle+4>: rts
(gdb) si
0x0002be6a in do_idle ()
1: x/i $pc 0x2be6a <do_idle+114>: movew %sr,%d0
Thanks,
Laurent
