lkml.org 
[lkml]   [2011]   [Aug]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    Date
    SubjectRe: [RFC v2] x86-64: Allow emulated vsyscalls from user addresses
    On Sun, Aug 7, 2011 at 8:19 AM, Borislav Petkov <bp@alien8.de> wrote:
    > On Sat, Aug 06, 2011 at 08:45:52AM +0200, Ingo Molnar wrote:
    >> > diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
    >> > index 9682ec5..6ae5e3a 100644
    >> > --- a/arch/x86/kernel/traps.c
    >> > +++ b/arch/x86/kernel/traps.c
    >> > @@ -873,9 +873,17 @@ void __init trap_init(void)
    >> >  #endif
    >> >
    >> >  #ifdef CONFIG_X86_64
    >> > -   BUG_ON(test_bit(VSYSCALL_EMU_VECTOR, used_vectors));
    >> > -   set_system_intr_gate(VSYSCALL_EMU_VECTOR, &emulate_vsyscall);
    >> > -   set_bit(VSYSCALL_EMU_VECTOR, used_vectors);
    >> > +   BUG_ON(test_bit(VSYSCALL0_EMU_VECTOR, used_vectors));
    >> > +   set_system_intr_gate(VSYSCALL0_EMU_VECTOR, &emulate_vsyscall0);
    >> > +   set_bit(VSYSCALL0_EMU_VECTOR, used_vectors);
    >> > +
    >> > +   BUG_ON(test_bit(VSYSCALL1_EMU_VECTOR, used_vectors));
    >> > +   set_system_intr_gate(VSYSCALL1_EMU_VECTOR, &emulate_vsyscall1);
    >> > +   set_bit(VSYSCALL1_EMU_VECTOR, used_vectors);
    >> > +
    >> > +   BUG_ON(test_bit(VSYSCALL2_EMU_VECTOR, used_vectors));
    >> > +   set_system_intr_gate(VSYSCALL2_EMU_VECTOR, &emulate_vsyscall2);
    >> > +   set_bit(VSYSCALL2_EMU_VECTOR, used_vectors);
    >> >  #endif
    >
    > ..
    >
    >> Surprisingly, this looks a bit cleaner to me than the original code,
    >> as the emulated syscalls separate out so nicely.
    >>
    >> The flip side is using up more of our vector space - but realistically
    >> we could put all this code behind a default-off LEGACY_VSYSCALL switch
    >> a year or two down the line, when distros have ugpraded glibc.
    >
    > This probably needs an entry in <Documentation/feature-removal-schedule.txt>.

    Will do. Maybe that will encourage glibc to stop using them in static binaries.

    I'll wire up sys_getcpu on x86_64 at the same time for good measure.
    It's not currently available as a real syscall.

    >
    > Also, what do we do with userspace which decides to hardcode "int 0x4[012]"
    > somewhere in the meantime?

    Break it? Any code that does that will get an unconditional warning
    with this patch.

    --Andy
    --
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2011-08-07 15:01    [W:0.023 / U:1.612 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site