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[Qemu-devel] [PATCH v9 18/21] replay: describe reverse debugging in docs
From: |
Pavel Dovgalyuk |
Subject: |
[Qemu-devel] [PATCH v9 18/21] replay: describe reverse debugging in docs/replay.txt |
Date: |
Wed, 09 Jan 2019 15:13:04 +0300 |
User-agent: |
StGit/0.17.1-dirty |
This patch updates the documentation and describes usage of the reverse
debugging in QEMU+GDB.
Signed-off-by: Pavel Dovgalyuk <address@hidden>
---
docs/replay.txt | 33 +++++++++++++++++++++++++++++++++
1 file changed, 33 insertions(+)
diff --git a/docs/replay.txt b/docs/replay.txt
index 2c2c5f6..8447fdd 100644
--- a/docs/replay.txt
+++ b/docs/replay.txt
@@ -293,6 +293,39 @@ for recording and replaying must contain identical number
of ports in record
and replay modes, but their backends may differ.
E.g., '-serial stdio' in record mode, and '-serial null' in replay mode.
+Reverse debugging
+-----------------
+
+Reverse debugging allows "executing" the program in reverse direction.
+GDB remote protocol supports "reverse step" and "reverse continue"
+commands. The first one steps single instruction backwards in time,
+and the second one finds the last breakpoint in the past.
+
+Recorded executions may be used to enable reverse debugging. QEMU can't
+execute the code in backwards direction, but can load a snapshot and
+replay forward to find the desired position or breakpoint.
+
+The following GDB commands are supported:
+ - reverse-stepi (or rsi) - step one instruction backwards
+ - reverse-continue (or rc) - find last breakpoint in the past
+
+Reverse step loads the nearest snapshot and replays the execution until
+the required instruction is met.
+
+Reverse continue may include several passes of examining the execution
+between the snapshots. Each of the passes include the following steps:
+ 1. loading the snapshot
+ 2. replaying to examine the breakpoints
+ 3. if breakpoint or watchpoint was met
+ - loading the snaphot again
+ - replaying to the required breakpoint
+ 4. else
+ - proceeding to the p.1 with the earlier snapshot
+
+Therefore usage of the reverse debugging requires at least one snapshot
+created in advance. See the "Snapshotting" section to learn about running
+record/replay and creating the snapshot in these modes.
+
Replay log format
-----------------
- Re: [Qemu-devel] [PATCH v9 11/21] replay: introduce info hmp/qmp command, (continued)
- [Qemu-devel] [PATCH v9 12/21] replay: introduce breakpoint at the specified step, Pavel Dovgalyuk, 2019/01/09
- [Qemu-devel] [PATCH v9 13/21] replay: implement replay-seek command to proceed to the desired step, Pavel Dovgalyuk, 2019/01/09
- [Qemu-devel] [PATCH v9 14/21] replay: refine replay-time module, Pavel Dovgalyuk, 2019/01/09
- [Qemu-devel] [PATCH v9 15/21] replay: flush rr queue before loading the vmstate, Pavel Dovgalyuk, 2019/01/09
- [Qemu-devel] [PATCH v9 16/21] gdbstub: add reverse step support in replay mode, Pavel Dovgalyuk, 2019/01/09
- [Qemu-devel] [PATCH v9 17/21] gdbstub: add reverse continue support in replay mode, Pavel Dovgalyuk, 2019/01/09
- [Qemu-devel] [PATCH v9 18/21] replay: describe reverse debugging in docs/replay.txt,
Pavel Dovgalyuk <=
- [Qemu-devel] [PATCH v9 19/21] replay: add BH oneshot event for block layer, Pavel Dovgalyuk, 2019/01/09
[Qemu-devel] [PATCH v9 20/21] replay: init rtc after enabling the replay, Pavel Dovgalyuk, 2019/01/09
[Qemu-devel] [PATCH v9 21/21] replay: document development rules, Pavel Dovgalyuk, 2019/01/09
Re: [Qemu-devel] [PATCH v9 00/21] Fixing record/replay and adding reverse debugging, no-reply, 2019/01/13