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SubjectRe: [PATCH v22 07/24] x86/sgx: Add wrappers for ENCLS leaf functions
On Fri, Oct 04, 2019 at 11:45:13AM +0200, Borislav Petkov wrote:
> On Tue, Sep 03, 2019 at 05:26:38PM +0300, Jarkko Sakkinen wrote:
> > ENCLS is a ring 0 instruction that contains a set of leaf functions for
> > managing enclaves [1]. Enclaves SGX hosted measured and signed software
> > entities, which are protected by asserting the outside memory accesses and
> > memory encryption.
> >
> > Add a two-layer macro system along with an encoding scheme to allow
> > wrappers to return trap numbers along ENCLS-specific error codes. The
> > bottom layer of the macro system splits between the leafs that return an
> > error code and those that do not. The second layer generates the correct
> > input/output annotations based on the number of operands for each leaf
> > function.
> >
> > [1] Intel SDM: 36.6 ENCLAVE INSTRUCTIONS AND INTEL®
> >
> > Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
>
> This SOB needs to come...
>
> > Co-developed-by: Sean Christopherson <sean.j.christopherson@intel.com>
> > Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
>
> <--- ... here.

This issue might persists in a few commits. I'll go through all of
them.

>
> > +/**
> > + * ENCLS_FAULT_FLAG - flag signifying an ENCLS return code is a trapnr
> > + *
> > + * ENCLS has its own (positive value) error codes and also generates
> > + * ENCLS specific #GP and #PF faults. And the ENCLS values get munged
> > + * with system error codes as everything percolates back up the stack.
> > + * Unfortunately (for us), we need to precisely identify each unique
> > + * error code, e.g. the action taken if EWB fails varies based on the
> > + * type of fault and on the exact SGX error code, i.e. we can't simply
> > + * convert all faults to -EFAULT.
> > + *
> > + * To make all three error types coexist, we set bit 30 to identify an
> > + * ENCLS fault. Bit 31 (technically bits N:31) is used to differentiate
> > + * between positive (faults and SGX error codes) and negative (system
> > + * error codes) values.
> > + */
> > +#define ENCLS_FAULT_FLAG 0x40000000
>
> BIT(30)
>
> > +
> > +/**
> > + * Retrieve the encoded trapnr from the specified return code.
> > + */
> > +#define ENCLS_TRAPNR(r) ((r) & ~ENCLS_FAULT_FLAG)
> > +
> > +/* Issue a WARN() about an ENCLS leaf. */
> > +#define ENCLS_WARN(r, name) { \
> > + do { \
> > + int _r = (r); \
> > + WARN(_r, "sgx: %s returned %d (0x%x)\n", (name), _r, \
> > + _r); \
>
> Let that line stick out a bit:
>
> WARN(_r, "sgx: %s returned %d (0x%x)\n", (name), _r, _r); \
>
> > + } while (0); \
> > +}
> > +
> > +/**
> > + * encls_faulted() - Check if ENCLS leaf function faulted
> > + * @ret: the return value of an ENCLS leaf function call
> > + *
> > + * Return: true if the fault flag is set
> > + */
> > +static inline bool encls_faulted(int ret)
> > +{
> > + return (ret & ENCLS_FAULT_FLAG) != 0;
>
> return ret & ENCLS_FAULT_FLAG;

Great, thanks once more for great review comments. Highly appreciated.

/Jarkko

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