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Re: [for-5.0 PATCH 00/11] Support for reverse debugging with GDB
From: |
Alex Bennée |
Subject: |
Re: [for-5.0 PATCH 00/11] Support for reverse debugging with GDB |
Date: |
Thu, 16 Jan 2020 11:11:11 +0000 |
User-agent: |
mu4e 1.3.6; emacs 28.0.50 |
Pavel Dovgalyuk <address@hidden> writes:
> GDB remote protocol supports reverse debugging of the targets.
> It includes 'reverse step' and 'reverse continue' operations.
> The first one finds the previous step of the execution,
> and the second one is intended to stop at the last breakpoint that
> would happen when the program is executed normally.
>
> Reverse debugging is possible in the replay mode, when at least
> one snapshot was created at the record or replay phase.
> QEMU can use these snapshots for travelling back in time with GDB.
>
> Running the execution in replay mode allows using GDB reverse debugging
> commands:
> - reverse-stepi (or rsi): Steps one instruction to the past.
> QEMU loads on of the prior snapshots and proceeds to the desired
> instruction forward. When that step is reaches, execution stops.
> - reverse-continue (or rc): Runs execution "backwards".
> QEMU tries to find breakpoint or watchpoint by loaded prior snapshot
> and replaying the execution. Then QEMU loads snapshots again and
> replays to the latest breakpoint. When there are no breakpoints in
> the examined section of the execution, QEMU finds one more snapshot
> and tries again. After the first snapshot is processed, execution
> stops at this snapshot.
>
> The set of patches include the following modifications:
> - gdbstub update for reverse debugging support
> - functions that automatically perform reverse step and reverse
> continue operations
> - hmp/qmp commands for manipulating the replay process
> - improvement of the snapshotting for saving the execution step
> in the snapshot parameters
>
> The patches are available in the repository:
> https://github.com/ispras/qemu/tree/rr-191223
So I tried with your additional patch. Launching QEMU as:
./aarch64-softmmu//qemu-system-aarch64 -monitor none \
-display none -M virt -cpu max -display none \
-semihosting-config enable=on \
-kernel ./tests/tcg/aarch64-softmmu/memory \
-icount shift=5,rr=replay,rrfile=record.bin \
-s -S -d trace:gdbstub\*
And gdb:
gdb tests/tcg/aarch64-softmmu/memory \
-ex "target remote localhost:1234"
I get the following log:
(gdb) x/3i $pc
=> 0x400037b0 <__start>: adr x0, 0x40003000 <vector_table>
0x400037b4 <__start+4>: msr vbar_el1, x0
0x400037b8 <__start+8>: adrp x0, 0x40200000
(gdb) p/x $x0
$1 = 0x0
(gdb) si
92 msr vbar_el1, x0
(gdb) p/x $x0
$2 = 0x40003000
(gdb) rsi
warning: Remote failure reply: E14
Program stopped.
__start () at
/home/alex.bennee/lsrc/qemu.git/tests/tcg/aarch64/system/boot.S:92
92 msr vbar_el1, x0
(gdb) p/x $x0
$3 = 0x40003000
So it doesn't seem to be working.
>
> ---
>
> Pavel Dovgaluk (11):
> replay: provide an accessor for rr filename
> qcow2: introduce icount field for snapshots
> migration: introduce icount field for snapshots
> qapi: introduce replay.json for record/replay-related stuff
> replay: introduce info hmp/qmp command
> replay: introduce breakpoint at the specified step
> replay: implement replay-seek command
> replay: flush rr queue before loading the vmstate
> gdbstub: add reverse step support in replay mode
> gdbstub: add reverse continue support in replay mode
> replay: describe reverse debugging in docs/replay.txt
>
>
> MAINTAINERS | 1
> accel/tcg/translator.c | 1
> block/qapi.c | 18 ++
> block/qcow2-snapshot.c | 9 +
> block/qcow2.h | 3
> blockdev.c | 10 +
> cpus.c | 19 ++-
> docs/interop/qcow2.txt | 4 +
> docs/replay.txt | 33 +++++
> exec.c | 8 +
> gdbstub.c | 64 ++++++++-
> hmp-commands-info.hx | 14 ++
> hmp-commands.hx | 53 +++++++
> include/block/snapshot.h | 1
> include/monitor/hmp.h | 4 +
> include/sysemu/replay.h | 24 +++
> migration/savevm.c | 17 ++
> qapi/Makefile.objs | 2
> qapi/block-core.json | 8 +
> qapi/block.json | 3
> qapi/misc.json | 18 --
> qapi/qapi-schema.json | 1
> qapi/replay.json | 121 +++++++++++++++++
> replay/Makefile.objs | 1
> replay/replay-debugging.c | 325
> +++++++++++++++++++++++++++++++++++++++++++++
> replay/replay-internal.h | 6 +
> replay/replay.c | 22 +++
> stubs/replay.c | 10 +
> 28 files changed, 761 insertions(+), 39 deletions(-)
> create mode 100644 qapi/replay.json
> create mode 100644 replay/replay-debugging.c
--
Alex Bennée
- RE: [for-5.0 PATCH 00/11] Support for reverse debugging with GDB, Pavel Dovgalyuk, 2020/01/09
- Re: [for-5.0 PATCH 00/11] Support for reverse debugging with GDB, Kevin Wolf, 2020/01/09
- RE: [for-5.0 PATCH 00/11] Support for reverse debugging with GDB, Pavel Dovgalyuk, 2020/01/09
- Re: [for-5.0 PATCH 00/11] Support for reverse debugging with GDB, Markus Armbruster, 2020/01/13
- RE: [for-5.0 PATCH 00/11] Support for reverse debugging with GDB, Pavel Dovgalyuk, 2020/01/13
- Re: [for-5.0 PATCH 00/11] Support for reverse debugging with GDB, Kevin Wolf, 2020/01/13
- Re: [for-5.0 PATCH 00/11] Support for reverse debugging with GDB, Peter Maydell, 2020/01/13
- Re: [for-5.0 PATCH 00/11] Support for reverse debugging with GDB, Kevin Wolf, 2020/01/13
- Re: [for-5.0 PATCH 00/11] Support for reverse debugging with GDB, Peter Maydell, 2020/01/13
- Re: [for-5.0 PATCH 00/11] Support for reverse debugging with GDB, Alex Bennée, 2020/01/13
- Re: [for-5.0 PATCH 00/11] Support for reverse debugging with GDB,
Alex Bennée <=