From: Yao Qi <qiyaoltc@gmail.com>
To: gdb-patches@sourceware.org
Subject: [RFC 0/3] Use reinsert breakpoint for vCont;s
Date: Fri, 06 May 2016 10:32:00 -0000 [thread overview]
Message-ID: <1462530736-25117-1-git-send-email-yao.qi@linaro.org> (raw)
Nowadays, reinsert breakpoint is used in GDBserver to step over a
breakpoint. I want to use it to handle vCont;s. The motivation
of this work is to exercise software single step in GDBserver side.
In the past two weeks, I am fixing various test fails, but still
can't fix all of them. I want to post something here, and hope
people can help me on this area.
Suppose GDB is able to send vCont;s to GDBserver using software
single step (done by patch 3), what should GDBserver do? It call
function single_step if lwp->resume->kind is resume_step. See
patch 2.
With this change, reinsert breakpoint is used for two purposes,
1) step over GDBserver breakpoint, 2) handle vCont;s. Here are some
facts or assumptions in my mind,
- reinsert breakpoints can be inserted for both step over and
vCont;s together. GDBserver should finish all step-overs
before resuming the threads, see scenario b) below,
- GDB doesn't send more than one vCont s actions in one vCont
packet, although RSP doc doesn't say this.
It is straightforward to insert reinsert breakpoints for vCont;s,
but I am not sure when to delete them. Here are some scenarios,
a) vCont;s thread A, and vCont;c thread B. Thread A hits the reinsert
breakpoints, and GDBserver can remove them. What is the proper
place to remove them?
b) vCont;s thread A, and vCont;c thread B. Thread B hits breakpoints
(not reinsert), do we remove reinsert breakpoints? My answer is
no. In the following step-over, reinsert breakpoints for step-over
are deleted, but reinsert breakpoints for vCont;s (thread A) are still
there.
c) vCont;s thread A, and vCont;c thread B. Thread B hits the reinsert
breakpoints (for thread A vCont;s), do we remove reinsert breakpoints?
I think no, we can just step over it for thread B.
d) vCont;s thread A, and vCont;c thread B. A signal arrives, do we remove
reinsert breakpoints? Yes, I think so.
IMO, b) requires reinsert breakpoint thread specific, so that we can delete
reinsert breakpoints for step-over of thread B, but keep reinsert breakpoints
for vCont;s of thread A. That is what patch 1 does.
I tried different ways to remove reinsert breakpoints in GDBserver, but still
can't fix fails in gdb.threads/schedlock.exp, that the program gets SIGILL or
SIGSEGV. These fails can't happen in every run, and they are disappeared
when I turn on debugging output in GDBserver. I suspect they are about the
improper management to reinsert breakpoints.
(gdb) PASS: gdb.threads/schedlock.exp: schedlock=off: cmd=next: call_function=1: next to increment (5)
next^M
78 while (*myp > 0)^M
(gdb) next^M
^M
Thread 1 "schedlock" received signal SIGILL, Illegal instruction.^M
[Switching to Thread 3797.3797]^M
0x000087f8 in thread_function (arg=0x0) at /home/yao/SourceCode/gnu/gdb/git/gdb/testsuite/gdb.threads/schedlock.c:78^M
78 while (*myp > 0)^M
(gdb) FAIL: gdb.threads/schedlock.exp: schedlock=off: cmd=next: call_function=1: next to increment (6)
Any ideas on the overall design, how to handle vCont;s in GDBserver using
software single step? or is it a completely wrong thing to handle vCont;s
using software single step?
*** BLURB HERE ***
Yao Qi (3):
make reinsert breakpoint thread specific
use reinsert breakpoint for vCont;s
[GDBserver] Support vCont s and S actions with software single step
gdb/gdbserver/linux-low.c | 37 ++++++++++++++++++++++++++++++++-----
gdb/gdbserver/mem-break.c | 29 ++++++++++++++++++++++++++---
gdb/gdbserver/mem-break.h | 13 +++++++++----
gdb/gdbserver/server.c | 13 ++++++++-----
4 files changed, 75 insertions(+), 17 deletions(-)
--
1.9.1
next reply other threads:[~2016-05-06 10:32 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-06 10:32 Yao Qi [this message]
2016-05-06 10:32 ` [RFC 1/3] make reinsert breakpoint thread specific Yao Qi
2016-05-06 10:32 ` [RFC 2/3] use reinsert breakpoint for vCont;s Yao Qi
2016-05-11 10:41 ` Yao Qi
2016-05-12 13:25 ` Antoine Tremblay
2016-05-13 12:12 ` Antoine Tremblay
2016-05-12 14:03 ` Antoine Tremblay
2016-05-12 16:38 ` Yao Qi
2016-05-06 10:32 ` [PATCH 3/3] [GDBserver] Support vCont s and S actions with software single step Yao Qi
2016-05-09 15:17 ` [RFC 0/3] Use reinsert breakpoint for vCont;s Antoine Tremblay
2016-05-10 13:29 ` Antoine Tremblay
2016-05-11 8:35 ` Yao Qi
2016-05-11 12:08 ` Antoine Tremblay
2016-05-17 14:08 ` Antoine Tremblay
2016-05-18 7:50 ` Yao Qi
2016-05-18 11:50 ` Antoine Tremblay
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1462530736-25117-1-git-send-email-yao.qi@linaro.org \
--to=qiyaoltc@gmail.com \
--cc=gdb-patches@sourceware.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).