Commit-ID: c2c9b52fab0d0cf993476ed4c34f24da5a1205ae Gitweb: http://git.kernel.org/tip/c2c9b52fab0d0cf993476ed4c34f24da5a1205ae Author: Andy Lutomirski <luto@xxxxxxxxxx> AuthorDate: Wed, 9 Mar 2016 19:00:27 -0800 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitDate: Thu, 10 Mar 2016 09:48:12 +0100 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@xxxxxxxxx> Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxxxx> Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx> Cc: H. Peter Anvin <hpa@xxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Oleg Nesterov <oleg@xxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Link: http://lkml.kernel.org/r/3f98b207472dc9784838eb5ca2b89dcc845ce269.1457578375.git.luto@xxxxxxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- arch/x86/entry/entry_32.S | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index 8daa812..7610906 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). */ -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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