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Re: um: PTRACE_SETREGSET failure with XSTATE on Kabylake CPU

From Richard Weinberger <richard@nod.at>
Newsgroups linux.kernel
Subject Re: um: PTRACE_SETREGSET failure with XSTATE on Kabylake CPU
Date 2017-06-20 20:20 +0200
Message-ID <tUvUR-3DD-19@gated-at.bofh.it> (permalink)
References <tUgCu-27M-9@gated-at.bofh.it> <tUliO-5a4-11@gated-at.bofh.it> <tUnaZ-6kQ-93@gated-at.bofh.it> <tUnkC-6DB-15@gated-at.bofh.it> <tUvLc-3zj-19@gated-at.bofh.it>
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Yu-cheng,

Am 20.06.2017 um 20:04 schrieb Yu-cheng Yu:
>>> So to summarize:
>>>
>>> - PTRACE_GETREGSET with NT_X86_XSTATE gets 832 and return 832, with no
>>> error.
>>>
>>> - PTRACE_SETREGSET get 832 (sizeof struct _xstate) but wants at least
>>> 1088, otherwise it will fail with -EFAULT (why not -EINVAL?)
>>>
>>> Ideas?
> 
> We considered allowing a partial XSAVE buffer for PTRACE_SETREGSET, but
> it was that the XSAVE instruction requires a full-size buffer led to
> this choice.  Using a smaller buffer for XSAVE causes a fault.

So, this code is not supposed to work?

iov.iov_base = fp_regs;
iov.iov_len = sizeof(struct _xstate);
ptrace(PTRACE_GETREGSET, pid, NT_X86_XSTATE, &iov);
ptrace(PTRACE_SETREGSET, pid, NT_X86_XSTATE, &iov);

This is what UML does and on Thomas's new Laptop PTRACE_SETREGSET is failing.

Thanks,
//richard

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Thread

um: PTRACE_SETREGSET failure with XSTATE on Kabylake CPU Thomas Meyer <thomas@m3y3r.de> - 2017-06-20 04:00 +0200
  Re: um: PTRACE_SETREGSET failure with XSTATE on Kabylake CPU Richard Weinberger <richard@nod.at> - 2017-06-20 09:00 +0200
    Re: um: PTRACE_SETREGSET failure with XSTATE on Kabylake CPU Thomas Meyer <thomas@m3y3r.de> - 2017-06-20 11:00 +0200
      Re: um: PTRACE_SETREGSET failure with XSTATE on Kabylake CPU Richard Weinberger <richard@nod.at> - 2017-06-20 11:10 +0200
        Re: um: PTRACE_SETREGSET failure with XSTATE on Kabylake CPU Yu-cheng Yu <yu-cheng.yu@intel.com> - 2017-06-20 20:10 +0200
          Re: um: PTRACE_SETREGSET failure with XSTATE on Kabylake CPU Richard Weinberger <richard@nod.at> - 2017-06-20 20:20 +0200
            Re: um: PTRACE_SETREGSET failure with XSTATE on Kabylake CPU Richard Weinberger <richard@nod.at> - 2017-06-20 21:00 +0200
              Re: um: PTRACE_SETREGSET failure with XSTATE on Kabylake CPU Yu-cheng Yu <yu-cheng.yu@intel.com> - 2017-06-20 22:00 +0200
                Re: um: PTRACE_SETREGSET failure with XSTATE on Kabylake CPU Thomas Meyer <thomas@m3y3r.de> - 2017-06-20 22:20 +0200

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