[v24,06/24] x86/sgx: Add wrappers for ENCLS leaf functions
diff mbox series

Message ID 20191129231326.18076-7-jarkko.sakkinen@linux.intel.com
State New
Headers show
Series
  • Intel SGX foundations
Related show

Commit Message

Jarkko Sakkinen Nov. 29, 2019, 11:13 p.m. UTC
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 INTELĀ®

Co-developed-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
---
 arch/x86/kernel/cpu/sgx/encls.h | 251 ++++++++++++++++++++++++++++++++
 1 file changed, 251 insertions(+)
 create mode 100644 arch/x86/kernel/cpu/sgx/encls.h

Comments

Borislav Petkov Dec. 17, 2019, 2:45 p.m. UTC | #1
On Sat, Nov 30, 2019 at 01:13:08AM +0200, Jarkko Sakkinen wrote:
> +/**
> + * 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 =
> +		boot_cpu_has(X86_FEATURE_SGX2) ? X86_TRAP_PF : X86_TRAP_GP;
> +	bool fault = ret & ENCLS_FAULT_FLAG;
> +
> +	return (fault && ENCLS_TRAPNR(ret) != epcm_trapnr) || (!fault && ret);
> +}

Can we make this function more readable?

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;
}

I hope I've converted it correctly but I might've missed some corner
case...

Thx.
Jarkko Sakkinen Dec. 19, 2019, 12:39 a.m. UTC | #2
On Tue, 2019-12-17 at 15:45 +0100, Borislav Petkov wrote:
> On Sat, Nov 30, 2019 at 01:13:08AM +0200, Jarkko Sakkinen wrote:
> > +/**
> > + * 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 =
> > +		boot_cpu_has(X86_FEATURE_SGX2) ? X86_TRAP_PF : X86_TRAP_GP;
> > +	bool fault = ret & ENCLS_FAULT_FLAG;
> > +
> > +	return (fault && ENCLS_TRAPNR(ret) != epcm_trapnr) || (!fault && ret);
> > +}
> 
> Can we make this function more readable?
> 
> 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;
> }
> 
> I hope I've converted it correctly but I might've missed some corner
> case...
> 
> Thx.

Absolutely. I absolutely hate too "clever code".

/Jarkko

Patch
diff mbox series

diff --git a/arch/x86/kernel/cpu/sgx/encls.h b/arch/x86/kernel/cpu/sgx/encls.h
new file mode 100644
index 000000000000..d6381e4f6eb2
--- /dev/null
+++ b/arch/x86/kernel/cpu/sgx/encls.h
@@ -0,0 +1,251 @@ 
+/* 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 - ENCLS leaf function type
+ * %ECREATE:	Create an uninitialized enclave.
+ * %EADD:	Add a page to an uninitialized enclave.
+ * %EINIT:	Change enclave to initialized state.
+ * %EREMOVE:	Remove a page from an enclave.
+ * %EDBGRD:	Read a word from an enclave.
+ * %EDBGWR:	Write a word to an enclave.
+ * %EEXTEND:	Measure 256 bytes of an added page.
+ * %ELDU:	Load a reclaimed page in unblocked state.
+ * %EBLOCK:	Change page state to blocked, which means that hardware threads
+ *		cannot access it and create new TLB entries to it.
+ * %EPA:	Create a Version Array (VA) page used to store the version
+ *		numbers for 512 reclaimed EPC pages.
+ * %EWB:	Reclaim a page to the regular memory.
+ * %ETRACK:	Start a new shoot down sequence. Used to together with EBLOCK to
+ *		make sure that a page is safe to swap.
+ */
+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(_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 =
+		boot_cpu_has(X86_FEATURE_SGX2) ? X86_TRAP_PF : X86_TRAP_GP;
+	bool fault = ret & ENCLS_FAULT_FLAG;
+
+	return (fault && ENCLS_TRAPNR(ret) != epcm_trapnr) || (!fault && 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, struct sgx_einittoken *einittoken,
+			  void *secs)
+{
+	return __encls_ret_3(EINIT, sigstruct, secs, einittoken);
+}
+
+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 */