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[Qemu-devel] [PATCH 0/3] scripts/qemu-gdb: Add event tracing support

From: Peter Maydell
Subject: [Qemu-devel] [PATCH 0/3] scripts/qemu-gdb: Add event tracing support
Date: Thu, 14 May 2015 17:43:52 +0100

This patchset adds support for two new commands to our
gdb scripts, which allow dynamically enabling and disabling
tracing of events, like this:

(gdb) source scripts/qemu-gdb.py 
(gdb) qemu trace-enable translate_block
Enabled trace event translate_block
Breakpoint 1 at 0xb634f: file ../trace/generated-tracers.h, line 4734.
(gdb) run
translate_block: tb:0x7fffc69ce010, pc:0x40000000, tb_code:0x7fffd39ce000
translate_block: tb:0x7fffc69ce078, pc:0x40010000, tb_code:0x7fffd39ce140
translate_block: tb:0x7fffc69ce0e0, pc:0x40010034, tb_code:0x7fffd39ce180
translate_block: tb:0x7fffc69ce148, pc:0x40013700, tb_code:0x7fffd39ce1d0
translate_block: tb:0x7fffc69ce1b0, pc:0x40013710, tb_code:0x7fffd39ce270
translate_block: tb:0x7fffc69ce218, pc:0x4001003c, tb_code:0x7fffd39ce310

This works by setting custom breakpoints on the stub functions
trace_<eventname> that the null tracing backend creates. It
probably doesn't work with an optimised build, but on the other
hand because it's purely implemented within gdb you can use a
tool like 'rr' (http://rr-project.org/) to record a run with no
tracing enabled and then turn the tracing on and off as you desire
during the replay.

Patches one and two do some initial splitting of qemu-gdb.py into
separate modules just to keep it from growing unhelpfully large.

-- PMM

Peter Maydell (3):
  scripts/qemu-gdb: Split MtreeCommand into its own module
  scripts/qemu-gdb: Split CoroutineCommand into its own file
  scripts/qemu-gdb: Add support for printing trace events

 scripts/qemu-gdb.py          | 144 +++------------------------------
 scripts/qemugdb/__init__.py  |  28 +++++++
 scripts/qemugdb/coroutine.py |  91 +++++++++++++++++++++
 scripts/qemugdb/mtree.py     |  82 +++++++++++++++++++
 scripts/qemugdb/trace.py     | 188 +++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 398 insertions(+), 135 deletions(-)
 create mode 100644 scripts/qemugdb/__init__.py
 create mode 100644 scripts/qemugdb/coroutine.py
 create mode 100644 scripts/qemugdb/mtree.py
 create mode 100644 scripts/qemugdb/trace.py


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