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[PATCH] fix broken vm86 interrupt/signal handling

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Commit c3ff8ec31c1249d268cd11390649768a12bec1b9 ("[PATCH] i386: Don't
miss pending signals returning to user mode after signal processing")
meant that vm86 interrupt/signal handling got broken for the case when
vm86 is called from kernel space.

In this scenario, if signal is pending because of vm86 interrupt,
do_notify_resume/do_signal exits immediately due to user_mode() check,
without processing any signals.  Thus, resume_userspace handler is spinning
in a tight loop with signal pending and TIF_SIGPENDING is set.  Previously
everything worked Ok.

No in-tree usage of vm86() from kernel space exists, but I've heard
about a number of projects out there which use vm86 calls from kernel,
one of them being this, for instance:

	http://dev.gentoo.org/~spock/projects/vesafb-tng/

The following patch fixes the issue.

Signed-off-by: Aleksey Gorelov <aleksey_gorelov@phoenix.com>
Cc: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Aleksey Gorelov 2006-06-27 02:53:48 -07:00 committed by Linus Torvalds
parent c723e08460
commit 4031ff3881
1 changed files with 9 additions and 2 deletions
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11
arch/i386/kernel/entry.S
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@ -83,6 +83,12 @@ VM_MASK = 0x00020000
#define resume_kernel restore_nocheck
#endif
#ifdef CONFIG_VM86
#define resume_userspace_sig check_userspace
#else
#define resume_userspace_sig resume_userspace
#endif
#define SAVE_ALL \
cld; \
pushl %es; \
@ -211,6 +217,7 @@ ret_from_exception:
preempt_stop
ret_from_intr:
GET_THREAD_INFO(%ebp)
check_userspace:
movl EFLAGS(%esp), %eax # mix EFLAGS and CS
movb CS(%esp), %al
testl $(VM_MASK | 3), %eax
@ -415,7 +422,7 @@ work_notifysig: # deal with pending signals and
# vm86-space
xorl %edx, %edx
call do_notify_resume
jmp resume_userspace
jmp resume_userspace_sig
ALIGN
work_notifysig_v86:
@ -428,7 +435,7 @@ work_notifysig_v86:
movl %eax, %esp
xorl %edx, %edx
call do_notify_resume
jmp resume_userspace
jmp resume_userspace_sig
#endif
# perform syscall exit tracing