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SubjectRe: [PATCH v22 07/24] x86/sgx: Add wrappers for ENCLS leaf functions
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.

> +/**
> + * 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;

--
Regards/Gruss,
Boris.

https://people.kernel.org/tglx/notes-about-netiquette

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