Commit 4031ff38 authored Jun 27, 2006 by Aleksey Gorelov Committed by Linus Torvalds Jun 27, 2006

[PATCH] fix broken vm86 interrupt/signal handling

Commit c3ff8ec3 ("[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>

parent c723e084

arch/i386/kernel/entry.S

+9 −2

Original line number	Diff line number	Diff line
		@@ -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

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