Re: [PATCH v36 05/24] x86/sgx: Add wrappers for ENCLS leaf functions
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
>
> Acked-by: Jethro Beekman
> Co-developed-by: Sean Christopherson
> Signed-off-by: Sean Christopherson
> Signed-off-by: Jarkko Sakkinen
> ---
> 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 ..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
> +#include
> +#include
> +#include
> +#include
> +#include
> +#include
> +#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 0x4000
> +
> +/* 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" \
> +
[PATCH v36 05/24] x86/sgx: Add wrappers for ENCLS leaf functions
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®
Acked-by: Jethro Beekman
Co-developed-by: Sean Christopherson
Signed-off-by: Sean Christopherson
Signed-off-by: Jarkko Sakkinen
---
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 ..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
+#include
+#include
+#include
+#include
+#include
+#include
+#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 0x4000
+
+/* 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
