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[Bug 1913913] [NEW] i386-linux-user returns -1 in sigcontext->trapno
From: |
Dirk A Niggemann |
Subject: |
[Bug 1913913] [NEW] i386-linux-user returns -1 in sigcontext->trapno |
Date: |
Sun, 31 Jan 2021 00:11:08 -0000 |
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.
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- [Bug 1913913] [NEW] i386-linux-user returns -1 in sigcontext->trapno,
Dirk A Niggemann <=