[RFC PATCH v2 0/4] x86: Add vDSO exception fixup for SGX

[Sean Christopherson <sean.j.christopherson@intel.com>]

This version is almost entirely about the vDSO function itself,
i.e. patch 4/4.  Feel free to ignore patches 2/4 and 3/4, I need
to do (a lot) more legwork to address feedback and improve their
changelogs.  I'm expecting that to take a fair amount of time and
wanted to get the alternative exit handler idea out there ASAP.

The new vDSO function builds but is otherwise completely untested.

v2:
  - For all intents and purposes, rewrite the SGX vDSO function.
    This version is quite a bit different than anything discussed in
    the past.  Rather than provide separate a separate function or an
    explicit parameter to request ERESUME, e.g. to recover after a
    fault, take an optional "exit handler" that provides the caller
    the opportunity to specify if and how the enclave should be
    resumed.  More details in the changelog.

  - Rename it to __vdso_sgx_enter_enclave() to abstract the details
    of EENTER and ERESUME to some degree.

  - Give the enclave RDI, RSI and RDX to pass data out of the enclave.

  - Call fixup_vdso_exception() in do_int3().


v1: https://lkml.kernel.org/r/20181205232012.28920-1-sean.j.christopherson@intel.com


Sean Christopherson (4):
  x86/vdso: Add support for exception fixup in vDSO functions
  x86/fault: Attempt to fixup unhandled #PF in vDSO before signaling
  x86/traps: Attempt to fixup exceptions in vDSO before signaling
  x86/vdso: Add __vdso_sgx_enter_enclave() to wrap SGX enclave
    transitions

 arch/x86/entry/vdso/Makefile             |   5 +-
 arch/x86/entry/vdso/extable.c            |  37 +++++++
 arch/x86/entry/vdso/extable.h            |  17 ++++
 arch/x86/entry/vdso/vdso-layout.lds.S    |   9 +-
 arch/x86/entry/vdso/vdso.lds.S           |   1 +
 arch/x86/entry/vdso/vdso2c.h             |  58 +++++++++--
 arch/x86/entry/vdso/vsgx_enter_enclave.c | 119 +++++++++++++++++++++++
 arch/x86/include/asm/vdso.h              |   5 +
 arch/x86/kernel/traps.c                  |  15 +++
 arch/x86/mm/fault.c                      |   7 ++
 10 files changed, 262 insertions(+), 11 deletions(-)
 create mode 100644 arch/x86/entry/vdso/extable.c
 create mode 100644 arch/x86/entry/vdso/extable.h
 create mode 100644 arch/x86/entry/vdso/vsgx_enter_enclave.c

-- 
2.19.2