* [Bug 1913913] [NEW] i386-linux-user returns -1 in sigcontext->trapno
@ 2021-01-31 0:11 Dirk A Niggemann
2021-01-31 19:49 ` [Bug 1913913] " Dirk A Niggemann
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: Dirk A Niggemann @ 2021-01-31 0:11 UTC (permalink / raw)
To: qemu-devel
Public bug reported:
QEMU development version, git commit
74208cd252c5da9d867270a178799abd802b9338. Behaviour has been noted in
5.2.0 generally.
Certain 16-bit windows programs crash WINE under QEMU linux-user with:
0084:err:seh:segv_handler Got unexpected trap -1
wine: Unhandled illegal instruction at address 00006D65 (thread 0084), starting debugger...
They run correctly on native i386.
Upon further inspection,it becomes clear these programs are failing at
addresses where they are making DOS calls (int 21h ie CD 21 for
instance).
It is also clear that WINE is expecting an exception/signal at this
point, to patch in the actual int21h handling code inside WINE.
However, wine uses sigcontext output extensively to do its structured
exception handling. sigcontext->trapno being set to -1 seems to confuse
it, causing it to treat the exception as an actual unhandled error.
I do not know if exception_index is being left at -1 due to the case of
privileged instructions being executed in 16-bit ldts not being handled
specifically, or if there is some other illegal instruction case causing
this.
** Affects: qemu
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1913913
Title:
i386-linux-user returns -1 in sigcontext->trapno
Status in QEMU:
New
Bug description:
QEMU development version, git commit
74208cd252c5da9d867270a178799abd802b9338. Behaviour has been noted in
5.2.0 generally.
Certain 16-bit windows programs crash WINE under QEMU linux-user with:
0084:err:seh:segv_handler Got unexpected trap -1
wine: Unhandled illegal instruction at address 00006D65 (thread 0084), starting debugger...
They run correctly on native i386.
Upon further inspection,it becomes clear these programs are failing at
addresses where they are making DOS calls (int 21h ie CD 21 for
instance).
It is also clear that WINE is expecting an exception/signal at this
point, to patch in the actual int21h handling code inside WINE.
However, wine uses sigcontext output extensively to do its structured
exception handling. sigcontext->trapno being set to -1 seems to
confuse it, causing it to treat the exception as an actual unhandled
error.
I do not know if exception_index is being left at -1 due to the case
of privileged instructions being executed in 16-bit ldts not being
handled specifically, or if there is some other illegal instruction
case causing this.
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1913913/+subscriptions
^ permalink raw reply [flat|nested] 4+ messages in thread* [Bug 1913913] Re: i386-linux-user returns -1 in sigcontext->trapno
2021-01-31 0:11 [Bug 1913913] [NEW] i386-linux-user returns -1 in sigcontext->trapno Dirk A Niggemann
@ 2021-01-31 19:49 ` Dirk A Niggemann
2021-05-12 18:07 ` Thomas Huth
2021-07-12 4:17 ` Launchpad Bug Tracker
2 siblings, 0 replies; 4+ messages in thread
From: Dirk A Niggemann @ 2021-01-31 19:49 UTC (permalink / raw)
To: qemu-devel
I have identified the core issue:
Synchronous exceptions/traps in linux-user/i386/cpu_loop.c are handled as a return value from cpu_exec().
cpu_exec() resets exception_index to -1 in cpu_handle_exception()
This means that queue_signal() (called from gen_signal() in the cpu
loop) does not store the actual CPU trap value anywhere.
If we abuse env->exception_nr to store the trapnr, and retrieve it from
there in setup_sigcontext() in linux-user/i386/signal.c instead of using
exception_index (which will be set to -1 for all synchronous excptions).
The main issue is if this breaks asynchronous signals, and under what
conditions exception_nr should be set to -1.
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1913913
Title:
i386-linux-user returns -1 in sigcontext->trapno
Status in QEMU:
New
Bug description:
QEMU development version, git commit
74208cd252c5da9d867270a178799abd802b9338. Behaviour has been noted in
5.2.0 generally.
Certain 16-bit windows programs crash WINE under QEMU linux-user with:
0084:err:seh:segv_handler Got unexpected trap -1
wine: Unhandled illegal instruction at address 00006D65 (thread 0084), starting debugger...
They run correctly on native i386.
Upon further inspection,it becomes clear these programs are failing at
addresses where they are making DOS calls (int 21h ie CD 21 for
instance).
It is also clear that WINE is expecting an exception/signal at this
point, to patch in the actual int21h handling code inside WINE.
However, wine uses sigcontext output extensively to do its structured
exception handling. sigcontext->trapno being set to -1 seems to
confuse it, causing it to treat the exception as an actual unhandled
error.
I do not know if exception_index is being left at -1 due to the case
of privileged instructions being executed in 16-bit ldts not being
handled specifically, or if there is some other illegal instruction
case causing this.
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1913913/+subscriptions
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug 1913913] Re: i386-linux-user returns -1 in sigcontext->trapno
2021-01-31 0:11 [Bug 1913913] [NEW] i386-linux-user returns -1 in sigcontext->trapno Dirk A Niggemann
2021-01-31 19:49 ` [Bug 1913913] " Dirk A Niggemann
@ 2021-05-12 18:07 ` Thomas Huth
2021-07-12 4:17 ` Launchpad Bug Tracker
2 siblings, 0 replies; 4+ messages in thread
From: Thomas Huth @ 2021-05-12 18:07 UTC (permalink / raw)
To: qemu-devel
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.
** Tags added: linux-user tcg
** Changed in: qemu
Status: New => Incomplete
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1913913
Title:
i386-linux-user returns -1 in sigcontext->trapno
Status in QEMU:
Incomplete
Bug description:
QEMU development version, git commit
74208cd252c5da9d867270a178799abd802b9338. Behaviour has been noted in
5.2.0 generally.
Certain 16-bit windows programs crash WINE under QEMU linux-user with:
0084:err:seh:segv_handler Got unexpected trap -1
wine: Unhandled illegal instruction at address 00006D65 (thread 0084), starting debugger...
They run correctly on native i386.
Upon further inspection,it becomes clear these programs are failing at
addresses where they are making DOS calls (int 21h ie CD 21 for
instance).
It is also clear that WINE is expecting an exception/signal at this
point, to patch in the actual int21h handling code inside WINE.
However, wine uses sigcontext output extensively to do its structured
exception handling. sigcontext->trapno being set to -1 seems to
confuse it, causing it to treat the exception as an actual unhandled
error.
I do not know if exception_index is being left at -1 due to the case
of privileged instructions being executed in 16-bit ldts not being
handled specifically, or if there is some other illegal instruction
case causing this.
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1913913/+subscriptions
^ permalink raw reply [flat|nested] 4+ messages in thread* [Bug 1913913] Re: i386-linux-user returns -1 in sigcontext->trapno
2021-01-31 0:11 [Bug 1913913] [NEW] i386-linux-user returns -1 in sigcontext->trapno Dirk A Niggemann
2021-01-31 19:49 ` [Bug 1913913] " Dirk A Niggemann
2021-05-12 18:07 ` Thomas Huth
@ 2021-07-12 4:17 ` Launchpad Bug Tracker
2 siblings, 0 replies; 4+ messages in thread
From: Launchpad Bug Tracker @ 2021-07-12 4:17 UTC (permalink / raw)
To: qemu-devel
[Expired for QEMU because there has been no activity for 60 days.]
** Changed in: qemu
Status: Incomplete => Expired
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1913913
Title:
i386-linux-user returns -1 in sigcontext->trapno
Status in QEMU:
Expired
Bug description:
QEMU development version, git commit
74208cd252c5da9d867270a178799abd802b9338. Behaviour has been noted in
5.2.0 generally.
Certain 16-bit windows programs crash WINE under QEMU linux-user with:
0084:err:seh:segv_handler Got unexpected trap -1
wine: Unhandled illegal instruction at address 00006D65 (thread 0084), starting debugger...
They run correctly on native i386.
Upon further inspection,it becomes clear these programs are failing at
addresses where they are making DOS calls (int 21h ie CD 21 for
instance).
It is also clear that WINE is expecting an exception/signal at this
point, to patch in the actual int21h handling code inside WINE.
However, wine uses sigcontext output extensively to do its structured
exception handling. sigcontext->trapno being set to -1 seems to
confuse it, causing it to treat the exception as an actual unhandled
error.
I do not know if exception_index is being left at -1 due to the case
of privileged instructions being executed in 16-bit ldts not being
handled specifically, or if there is some other illegal instruction
case causing this.
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1913913/+subscriptions
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2021-07-12 4:31 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2021-01-31 0:11 [Bug 1913913] [NEW] i386-linux-user returns -1 in sigcontext->trapno Dirk A Niggemann
2021-01-31 19:49 ` [Bug 1913913] " Dirk A Niggemann
2021-05-12 18:07 ` Thomas Huth
2021-07-12 4:17 ` Launchpad Bug Tracker
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