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| author |   Andy Lutomirski <luto@kernel.org> | 2016-03-09 19:00:27 -0800 |
|---|---|---|
| committer |   Ingo Molnar <mingo@kernel.org> | 2016-03-10 09:48:12 +0100 |
| commit | c2c9b52fab0d0cf993476ed4c34f24da5a1205ae (patch) | |
| tree | 8941a792ec1a7bb1a30d0d89df553a5c693a7d96 /arch | |
| parent | x86/entry/32: Filter NT and speed up AC filtering in SYSENTER (diff) | |
| download | linux-dev-c2c9b52fab0d0cf993476ed4c34f24da5a1205ae.tar.xz linux-dev-c2c9b52fab0d0cf993476ed4c34f24da5a1205ae.zip | |
x86/entry/32: Restore FLAGS on SYSEXIT
We weren't restoring FLAGS at all on SYSEXIT. Apparently no one cared.
With this patch applied, native kernels should always honor
task_pt_regs()->flags, which opens the door for some sys_iopl()
cleanups. I'll do those as a separate series, though, since getting
it right will involve tweaking some paravirt ops.
( The short version is that, before this patch, sys_iopl(), invoked via
SYSENTER, wasn't guaranteed to ever transfer the updated
regs->flags, so sys_iopl() had to change the hardware flags register
as well. )
Reported-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/3f98b207472dc9784838eb5ca2b89dcc845ce269.1457578375.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/entry/entry_32.S | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index 8daa8127f578..76109068149f 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -343,6 +343,15 @@ sysenter_past_esp: popl %eax /* pt_regs->ax */ /* + * Restore all flags except IF. (We restore IF separately because + * STI gives a one-instruction window in which we won't be interrupted, + * whereas POPF does not.) + */ + addl $PT_EFLAGS-PT_DS, %esp /* point esp at pt_regs->flags */ + btr $X86_EFLAGS_IF_BIT, (%esp) + popfl + + /* * Return back to the vDSO, which will pop ecx and edx. * Don't bother with DS and ES (they already contain __USER_DS). */ |