On Mon, 2021-07-05 at 11:36 +0200, David Hildenbrand wrote:
On 23.06.21 04:32, Ilya Leoshkevich wrote:
For SIGILL, SIGFPE and SIGTRAP the PSW must point after the
instruction, and at the instruction for other signals. Currently
under
qemu-user it always points at the instruction.
Fix by advancing psw.addr for these signals.
Buglink: https://gitlab.com/qemu-project/qemu/-/issues/319
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Co-developed-by: Ulrich Weigand <ulrich.weigand@de.ibm.com>
---
linux-user/s390x/cpu_loop.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/linux-user/s390x/cpu_loop.c b/linux-
user/s390x/cpu_loop.c
index 30568139df..230217feeb 100644
--- a/linux-user/s390x/cpu_loop.c
+++ b/linux-user/s390x/cpu_loop.c
@@ -133,6 +133,11 @@ void cpu_loop(CPUS390XState *env)
do_signal_pc:
addr = env->psw.addr;
+ /*
+ * For SIGILL, SIGFPE and SIGTRAP the PSW must point
after the
+ * instruction.
+ */
+ env->psw.addr += env->int_pgm_ilen;
We also reach this path via EXCP_DEBUG. How can we expect
env->int_pgm_ilen to contain something sensible in that case?
You are right, this breaks breakpoints after getting any PGM exception
(they turn into "Program received signal SIGTRAP, Trace/breakpoint
trap." instead of the usual "Breakpoint N").
We don't need a PSW rewind here, since it's already incremented
throught the following sequence:
1) GDB asks QEMU to set a breakpoint using a $Z0 packet.
2) translator_loop() notices the breakpoint and calls
s390x_tr_breakpoint_check().
3) s390x_tr_breakpoint_check() sets DisasContextBase.is_jmp to
DISAS_PC_STALE and increments DisasContextBase.pc_next by 2.
4) translator_loop() calls s390x_tr_tb_stop().
5) s390x_tr_tb_stop() calls update_psw_addr(), so the JITed code
increments the PSWA by 2 as well.
6) s390x_tr_tb_stop() calls gen_exception(EXCP_DEBUG).
What do you think about the following amend?
--- a/linux-user/s390x/cpu_loop.c
+++ b/linux-user/s390x/cpu_loop.c
@@ -64,7 +64,13 @@ void cpu_loop(CPUS390XState *env)
case EXCP_DEBUG:
sig = TARGET_SIGTRAP;
n = TARGET_TRAP_BRKPT;
- goto do_signal_pc;
+ /*
+ * For SIGTRAP the PSW must point after the instruction,
which it
+ * already does thanks to s390x_tr_tb_stop(). si_addr
doesn't need
+ * to be filled.
+ */
+ addr = 0;
+ goto do_signal;