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[Qemu-devel] [PATCH v10 18/24] replay: describe reverse debugging in doc
From: |
Pavel Dovgalyuk |
Subject: |
[Qemu-devel] [PATCH v10 18/24] replay: describe reverse debugging in docs/replay.txt |
Date: |
Thu, 17 Jan 2019 10:38:33 +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
-----------------
- [Qemu-devel] [PATCH v10 11/24] replay: introduce info hmp/qmp command, (continued)
- [Qemu-devel] [PATCH v10 11/24] replay: introduce info hmp/qmp command, Pavel Dovgalyuk, 2019/01/17
- [Qemu-devel] [PATCH v10 12/24] replay: introduce breakpoint at the specified step, Pavel Dovgalyuk, 2019/01/17
- [Qemu-devel] [PATCH v10 13/24] replay: implement replay-seek command, Pavel Dovgalyuk, 2019/01/17
- [Qemu-devel] [PATCH v10 14/24] replay: refine replay-time module, Pavel Dovgalyuk, 2019/01/17
- [Qemu-devel] [PATCH v10 15/24] replay: flush rr queue before loading the vmstate, Pavel Dovgalyuk, 2019/01/17
- [Qemu-devel] [PATCH v10 16/24] gdbstub: add reverse step support in replay mode, Pavel Dovgalyuk, 2019/01/17
- [Qemu-devel] [PATCH v10 18/24] replay: describe reverse debugging in docs/replay.txt,
Pavel Dovgalyuk <=
- [Qemu-devel] [PATCH v10 17/24] gdbstub: add reverse continue support in replay mode, Pavel Dovgalyuk, 2019/01/17
- [Qemu-devel] [PATCH v10 19/24] replay: add BH oneshot event for block layer, Pavel Dovgalyuk, 2019/01/17
- [Qemu-devel] [PATCH v10 20/24] replay: init rtc after enabling the replay, Pavel Dovgalyuk, 2019/01/17
- [Qemu-devel] [PATCH v10 21/24] replay: document development rules, Pavel Dovgalyuk, 2019/01/17
- [Qemu-devel] [PATCH v10 22/24] util/qemu-timer: refactor deadline calculation for external timers, Pavel Dovgalyuk, 2019/01/17
- [Qemu-devel] [PATCH v10 23/24] replay: fix replay shutdown, Pavel Dovgalyuk, 2019/01/17
- [Qemu-devel] [PATCH v10 24/24] replay: rename step-related variables and functions, Pavel Dovgalyuk, 2019/01/17
- Re: [Qemu-devel] [PATCH v10 00/24] Fixing record/replay and adding reverse debugging, no-reply, 2019/01/31