Re: [PATCH v36 05/24] x86/sgx: Add wrappers for ENCLS leaf functions

[Darren Kenny]

On Thursday, 2020-07-16 at 16:52:44 +03, Jarkko Sakkinen wrote:
> ENCLS is a ring 0 instruction, which contains a set of leaf functions for
> managing an enclave. Enclaves are 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.
>
> ENCLS leaf functions are documented in
>
>   Intel SDM: 36.6 ENCLAVE INSTRUCTIONS AND INTEL®

Tested-by: Darren Kenny <darren.kenny@xxxxxxxxxx>

>
> Acked-by: Jethro Beekman <jethro@xxxxxxxxxxxx>
> Co-developed-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
> ---
>  arch/x86/kernel/cpu/sgx/encls.h | 238 ++++++++++++++++++++++++++++++++
>  1 file changed, 238 insertions(+)
>  create mode 100644 arch/x86/kernel/cpu/sgx/encls.h
>
> diff --git a/arch/x86/kernel/cpu/sgx/encls.h b/arch/x86/kernel/cpu/sgx/encls.h
> new file mode 100644
> index 000000000000..f716b4328614
> --- /dev/null
> +++ b/arch/x86/kernel/cpu/sgx/encls.h
> @@ -0,0 +1,238 @@
> +/* SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause) */
> +#ifndef _X86_ENCLS_H
> +#define _X86_ENCLS_H
> +
> +#include <linux/bitops.h>
> +#include <linux/err.h>
> +#include <linux/io.h>
> +#include <linux/rwsem.h>
> +#include <linux/types.h>
> +#include <asm/asm.h>
> +#include <asm/traps.h>
> +#include "sgx.h"
> +
> +enum sgx_encls_leaf {
> +	ECREATE	= 0x00,
> +	EADD	= 0x01,
> +	EINIT	= 0x02,
> +	EREMOVE	= 0x03,
> +	EDGBRD	= 0x04,
> +	EDGBWR	= 0x05,
> +	EEXTEND	= 0x06,
> +	ELDU	= 0x08,
> +	EBLOCK	= 0x09,
> +	EPA	= 0x0A,
> +	EWB	= 0x0B,
> +	ETRACK	= 0x0C,
> +};
> +
> +/**
> + * 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
> +
> +/* 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_ONCE(_r, "%s returned %d (0x%x)\n", (name), _r, _r); \
> +	} while (0);							  \
> +}
> +
> +/**
> + * encls_failed() - Check if an ENCLS leaf function failed
> + * @ret:	the return value of an ENCLS leaf function call
> + *
> + * Check if an ENCLS leaf function failed. This happens when the leaf function
> + * causes a fault that is not caused by an EPCM conflict or when the leaf
> + * function returns a non-zero value.
> + */
> +static inline bool encls_failed(int ret)
> +{
> +	int epcm_trapnr;
> +
> +	if (boot_cpu_has(X86_FEATURE_SGX2))
> +		epcm_trapnr = X86_TRAP_PF;
> +	else
> +		epcm_trapnr = X86_TRAP_GP;
> +
> +	if (ret & ENCLS_FAULT_FLAG)
> +		return ENCLS_TRAPNR(ret) != epcm_trapnr;
> +
> +	return !!ret;
> +}
> +
> +/**
> + * __encls_ret_N - encode an ENCLS leaf that returns an error code in EAX
> + * @rax:	leaf number
> + * @inputs:	asm inputs for the leaf
> + *
> + * Emit assembly for an ENCLS leaf that returns an error code, e.g. EREMOVE.
> + * And because SGX isn't complex enough as it is, leafs that return an error
> + * code also modify flags.
> + *
> + * Return:
> + *	0 on success,
> + *	SGX error code on failure
> + */
> +#define __encls_ret_N(rax, inputs...)				\
> +	({							\
> +	int ret;						\
> +	asm volatile(						\
> +	"1: .byte 0x0f, 0x01, 0xcf;\n\t"			\
> +	"2:\n"							\
> +	".section .fixup,\"ax\"\n"				\
> +	"3: orl $"__stringify(ENCLS_FAULT_FLAG)",%%eax\n"	\
> +	"   jmp 2b\n"						\
> +	".previous\n"						\
> +	_ASM_EXTABLE_FAULT(1b, 3b)				\
> +	: "=a"(ret)						\
> +	: "a"(rax), inputs					\
> +	: "memory", "cc");					\
> +	ret;							\
> +	})
> +
> +#define __encls_ret_1(rax, rcx)		\
> +	({				\
> +	__encls_ret_N(rax, "c"(rcx));	\
> +	})
> +
> +#define __encls_ret_2(rax, rbx, rcx)		\
> +	({					\
> +	__encls_ret_N(rax, "b"(rbx), "c"(rcx));	\
> +	})
> +
> +#define __encls_ret_3(rax, rbx, rcx, rdx)			\
> +	({							\
> +	__encls_ret_N(rax, "b"(rbx), "c"(rcx), "d"(rdx));	\
> +	})
> +
> +/**
> + * __encls_N - encode an ENCLS leaf that doesn't return an error code
> + * @rax:	leaf number
> + * @rbx_out:	optional output variable
> + * @inputs:	asm inputs for the leaf
> + *
> + * Emit assembly for an ENCLS leaf that does not return an error code,
> + * e.g. ECREATE.  Leaves without error codes either succeed or fault.
> + * @rbx_out is an optional parameter for use by EDGBRD, which returns
> + * the the requested value in RBX.
> + *
> + * Return:
> + *   0 on success,
> + *   trapnr with ENCLS_FAULT_FLAG set on fault
> + */
> +#define __encls_N(rax, rbx_out, inputs...)			\
> +	({							\
> +	int ret;						\
> +	asm volatile(						\
> +	"1: .byte 0x0f, 0x01, 0xcf;\n\t"			\
> +	"   xor %%eax,%%eax;\n"					\
> +	"2:\n"							\
> +	".section .fixup,\"ax\"\n"				\
> +	"3: orl $"__stringify(ENCLS_FAULT_FLAG)",%%eax\n"	\
> +	"   jmp 2b\n"						\
> +	".previous\n"						\
> +	_ASM_EXTABLE_FAULT(1b, 3b)				\
> +	: "=a"(ret), "=b"(rbx_out)				\
> +	: "a"(rax), inputs					\
> +	: "memory");						\
> +	ret;							\
> +	})
> +
> +#define __encls_2(rax, rbx, rcx)				\
> +	({							\
> +	unsigned long ign_rbx_out;				\
> +	__encls_N(rax, ign_rbx_out, "b"(rbx), "c"(rcx));	\
> +	})
> +
> +#define __encls_1_1(rax, data, rcx)			\
> +	({						\
> +	unsigned long rbx_out;				\
> +	int ret = __encls_N(rax, rbx_out, "c"(rcx));	\
> +	if (!ret)					\
> +		data = rbx_out;				\
> +	ret;						\
> +	})
> +
> +static inline int __ecreate(struct sgx_pageinfo *pginfo, void *secs)
> +{
> +	return __encls_2(ECREATE, pginfo, secs);
> +}
> +
> +static inline int __eextend(void *secs, void *addr)
> +{
> +	return __encls_2(EEXTEND, secs, addr);
> +}
> +
> +static inline int __eadd(struct sgx_pageinfo *pginfo, void *addr)
> +{
> +	return __encls_2(EADD, pginfo, addr);
> +}
> +
> +static inline int __einit(void *sigstruct, void *token, void *secs)
> +{
> +	return __encls_ret_3(EINIT, sigstruct, secs, token);
> +}
> +
> +static inline int __eremove(void *addr)
> +{
> +	return __encls_ret_1(EREMOVE, addr);
> +}
> +
> +static inline int __edbgwr(void *addr, unsigned long *data)
> +{
> +	return __encls_2(EDGBWR, *data, addr);
> +}
> +
> +static inline int __edbgrd(void *addr, unsigned long *data)
> +{
> +	return __encls_1_1(EDGBRD, *data, addr);
> +}
> +
> +static inline int __etrack(void *addr)
> +{
> +	return __encls_ret_1(ETRACK, addr);
> +}
> +
> +static inline int __eldu(struct sgx_pageinfo *pginfo, void *addr,
> +			 void *va)
> +{
> +	return __encls_ret_3(ELDU, pginfo, addr, va);
> +}
> +
> +static inline int __eblock(void *addr)
> +{
> +	return __encls_ret_1(EBLOCK, addr);
> +}
> +
> +static inline int __epa(void *addr)
> +{
> +	unsigned long rbx = SGX_PAGE_TYPE_VA;
> +
> +	return __encls_2(EPA, rbx, addr);
> +}
> +
> +static inline int __ewb(struct sgx_pageinfo *pginfo, void *addr,
> +			void *va)
> +{
> +	return __encls_ret_3(EWB, pginfo, addr, va);
> +}
> +
> +#endif /* _X86_ENCLS_H */
> -- 
> 2.25.1