[Bug 1907210] [NEW] QEMU gdbstub command "?" issue

[Bug 1907210] [NEW] QEMU gdbstub command "?" issue

[Matic Kres]

Public bug reported:

I am using some third party GDB client, and I have noticed that every time "?" command is send from the client, QEMU gdbstub removes all break points. This behaviour is not expected since "?" command should only return stop reason.
Here is documentation from official gdb:
‘?’ Indicate the reason the target halted. The reply is the same as for step and
continue. This packet has a special interpretation when the target is in non-stop
mode; see Section E.10 [Remote Non-Stop], page 733.
Reply: See Section E.3 [Stop Reply Packets], page 693, for the reply specifications.

With some help on the irc, we have been able to pin point the failure point(in attachement file gdbstub.c).
Function that handles "?" command has this comment in it:
    /*
     * Remove all the breakpoints when this query is issued,
     * because gdb is doing an initial connect and the state
     * should be cleaned up.
     */
>From which it is clear that developer that wrote that code assumed, that because most popular gdb client only uses "?" command at initial connect, it is safe to also remove all BPs.
In my opinion initial connect should be detected in some other way, and not with "?" command.
Also note that official gdbserver does not remove the BPs when this command is send, this issue is present in QEMU and apparently also on kgdb(I was told that on irc, have not tested it myself)

** Affects: qemu
     Importance: Undecided
         Status: New

** Attachment added: "qemuissue.jpg"
   https://bugs.launchpad.net/bugs/1907210/+attachment/5441925/+files/qemuissue.jpg

** Description changed:

  I am using some third party GDB client, and I have noticed that every time "?" command is send from the client, QEMU gdbstub removes all break points. This behaviour is not expected since "?" command should only return stop reason.
  Here is documentation from official gdb:
  ‘?’ Indicate the reason the target halted. The reply is the same as for step and
  continue. This packet has a special interpretation when the target is in non-stop
  mode; see Section E.10 [Remote Non-Stop], page 733.
  Reply: See Section E.3 [Stop Reply Packets], page 693, for the reply specifications.
  
  With some help on the irc, we have been able to pin point the failure point(in attachement file gdbstub.c).
  Function that handles "?" command has this comment in it:
-     /*
-      * Remove all the breakpoints when this query is issued,
-      * because gdb is doing an initial connect and the state
-      * should be cleaned up.
-      */
- From which it is clear that developer that wrote that code assumed, that because most popular gdb client only uses "?" command at initial connect, it is safe to also remove all BPs. 
+     /*
+      * Remove all the breakpoints when this query is issued,
+      * because gdb is doing an initial connect and the state
+      * should be cleaned up.
+      */
+ From which it is clear that developer that wrote that code assumed, that because most popular gdb client only uses "?" command at initial connect, it is safe to also remove all BPs.
  In my opinion initial connect should be detected in some other way, and not with "?" command.
+ Also note that official gdbserver does not remove the BPs when this command is send, this issue is present in QEMU and apparently also on kgdb(I was told that on irc, have not tested it myself)

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Title:
  QEMU gdbstub command "?" issue

Status in QEMU:
  New

Bug description:
  I am using some third party GDB client, and I have noticed that every time "?" command is send from the client, QEMU gdbstub removes all break points. This behaviour is not expected since "?" command should only return stop reason.
  Here is documentation from official gdb:
  ‘?’ Indicate the reason the target halted. The reply is the same as for step and
  continue. This packet has a special interpretation when the target is in non-stop
  mode; see Section E.10 [Remote Non-Stop], page 733.
  Reply: See Section E.3 [Stop Reply Packets], page 693, for the reply specifications.

  With some help on the irc, we have been able to pin point the failure point(in attachement file gdbstub.c).
  Function that handles "?" command has this comment in it:
      /*
       * Remove all the breakpoints when this query is issued,
       * because gdb is doing an initial connect and the state
       * should be cleaned up.
       */
  From which it is clear that developer that wrote that code assumed, that because most popular gdb client only uses "?" command at initial connect, it is safe to also remove all BPs.
  In my opinion initial connect should be detected in some other way, and not with "?" command.
  Also note that official gdbserver does not remove the BPs when this command is send, this issue is present in QEMU and apparently also on kgdb(I was told that on irc, have not tested it myself)

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[Bug 1907210] Re: QEMU gdbstub command "?" issue

[Thomas Huth]

The QEMU project is currently moving its bug tracking to another system.
For this we need to know which bugs are still valid and which could be
closed already. Thus we are setting the bug state to "Incomplete" now.

If the bug has already been fixed in the latest upstream version of QEMU,
then please close this ticket as "Fix released".

If it is not fixed yet and you think that this bug report here is still
valid, then you have two options:

1) If you already have an account on gitlab.com, please open a new ticket
for this problem in our new tracker here:

    https://gitlab.com/qemu-project/qemu/-/issues

and then close this ticket here on Launchpad (or let it expire auto-
matically after 60 days). Please mention the URL of this bug ticket on
Launchpad in the new ticket on GitLab.

2) If you don't have an account on gitlab.com and don't intend to get
one, but still would like to keep this ticket opened, then please switch
the state back to "New" or "Confirmed" within the next 60 days (other-
wise it will get closed as "Expired"). We will then eventually migrate
the ticket automatically to the new system (but you won't be the reporter
of the bug in the new system and thus you won't get notified on changes
anymore).

Thank you and sorry for the inconvenience.


** Changed in: qemu
       Status: New => Incomplete

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You received this bug notification because you are a member of qemu-
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https://bugs.launchpad.net/bugs/1907210

Title:
  QEMU gdbstub command "?" issue

Status in QEMU:
  Incomplete

Bug description:
  I am using some third party GDB client, and I have noticed that every time "?" command is send from the client, QEMU gdbstub removes all break points. This behaviour is not expected since "?" command should only return stop reason.
  Here is documentation from official gdb:
  ‘?’ Indicate the reason the target halted. The reply is the same as for step and
  continue. This packet has a special interpretation when the target is in non-stop
  mode; see Section E.10 [Remote Non-Stop], page 733.
  Reply: See Section E.3 [Stop Reply Packets], page 693, for the reply specifications.

  With some help on the irc, we have been able to pin point the failure point(in attachement file gdbstub.c).
  Function that handles "?" command has this comment in it:
      /*
       * Remove all the breakpoints when this query is issued,
       * because gdb is doing an initial connect and the state
       * should be cleaned up.
       */
  From which it is clear that developer that wrote that code assumed, that because most popular gdb client only uses "?" command at initial connect, it is safe to also remove all BPs.
  In my opinion initial connect should be detected in some other way, and not with "?" command.
  Also note that official gdbserver does not remove the BPs when this command is send, this issue is present in QEMU and apparently also on kgdb(I was told that on irc, have not tested it myself)

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[Bug 1907210] Re: QEMU gdbstub command "?" issue

[Launchpad Bug Tracker]

[Expired for QEMU because there has been no activity for 60 days.]

** Changed in: qemu
       Status: Incomplete => Expired

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Title:
  QEMU gdbstub command "?" issue

Status in QEMU:
  Expired

Bug description:
  I am using some third party GDB client, and I have noticed that every time "?" command is send from the client, QEMU gdbstub removes all break points. This behaviour is not expected since "?" command should only return stop reason.
  Here is documentation from official gdb:
  ‘?’ Indicate the reason the target halted. The reply is the same as for step and
  continue. This packet has a special interpretation when the target is in non-stop
  mode; see Section E.10 [Remote Non-Stop], page 733.
  Reply: See Section E.3 [Stop Reply Packets], page 693, for the reply specifications.

  With some help on the irc, we have been able to pin point the failure point(in attachement file gdbstub.c).
  Function that handles "?" command has this comment in it:
      /*
       * Remove all the breakpoints when this query is issued,
       * because gdb is doing an initial connect and the state
       * should be cleaned up.
       */
  From which it is clear that developer that wrote that code assumed, that because most popular gdb client only uses "?" command at initial connect, it is safe to also remove all BPs.
  In my opinion initial connect should be detected in some other way, and not with "?" command.
  Also note that official gdbserver does not remove the BPs when this command is send, this issue is present in QEMU and apparently also on kgdb(I was told that on irc, have not tested it myself)

To manage notifications about this bug go to:
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