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    SubjectRe: [uml-devel] SYSCALL, ptrace and syscall restart breakages (Re: [RFC] weird crap with vdso on uml/i386)
    On Mon, Aug 22, 2011 at 04:27:51PM -0700, Linus Torvalds wrote:

    > So I think the "let's fix the vdso case for sysenter" + "let's remove
    > the 32-bit syscall vdso" is the right solution. If somebody has
    > hardcoded syscall instructions, or generates them dynamically with
    > some JIT, that's their problem. We'll continue to support it as well
    > as we ever have (read: "almost nobody will ever notice").

    Umm... Maybe, but I really wonder if it would be better to do this:
    * check if %ecx is the right one for vdso32 entry. If it isn't,
    act as we act now (and possibly warn). If it is, increment it by 4.
    * slap 0x90, 0x90, 0xcd, 0x80 right after that syscall insn -
    i.e. nop/nop/int 0x80. Followed by what we currently do there.

    Those who do syscall insn in 32bit mode outside of vdso will get
    what they currently get. __kernel_vsyscall() will keep working and do
    that without restart problems. And the price is comparison + branch not
    taken + addition for that path...

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      Last update: 2011-08-23 02:07    [W:0.020 / U:9.992 seconds]
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