[PATCH v12 06/13] x86/sgx: detect Intel SGX

[Jarkko Sakkinen]

From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>

Intel(R) SGX is a set of CPU instructions that can be used by applications
to set aside private regions of code and data. The code outside the enclave
is disallowed to access the memory inside the enclave by the CPU access
control.

This commit adds the check for SGX to arch/x86 and a new config option,
INTEL_SGX_CORE. Exposes a boolean variable 'sgx_enabled' to query whether
or not the SGX support is available.

Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
Co-developed-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
Co-developed-by: Suresh Siddha <suresh.b.siddha@xxxxxxxxx>
---
 arch/x86/Kconfig                | 19 ++++++++++++
 arch/x86/include/asm/sgx.h      | 12 ++++++++
 arch/x86/include/asm/sgx_pr.h   | 13 ++++++++
 arch/x86/kernel/cpu/Makefile    |  1 +
 arch/x86/kernel/cpu/intel_sgx.c | 54 +++++++++++++++++++++++++++++++++
 5 files changed, 99 insertions(+)
 create mode 100644 arch/x86/include/asm/sgx.h
 create mode 100644 arch/x86/include/asm/sgx_pr.h
 create mode 100644 arch/x86/kernel/cpu/intel_sgx.c

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index c07f492b871a..d2c7e7a2b2ac 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1925,6 +1925,25 @@ config X86_INTEL_MEMORY_PROTECTION_KEYS
 
 	  If unsure, say y.
 
+config INTEL_SGX_CORE
+	prompt "Intel SGX core functionality"
+	def_bool n
+	depends on X86_64 && CPU_SUP_INTEL
+	help
+	Intel Software Guard eXtensions (SGX) is a set of CPU instructions
+	that allows ring 3 applications to create enclaves, private regions
+	of memory that are protected, by hardware, from unauthorized access
+	and/or modification.
+
+	This option enables kernel recognition of SGX, high-level management
+	of the Enclave Page Cache (EPC), tracking and writing of SGX Launch
+	Enclave Hash MSRs, and allows for virtualization of SGX via KVM. By
+	iteslf, this option does not provide SGX support to userspace.
+
+	For details, see Documentation/x86/intel_sgx.rst
+
+	If unsure, say N.
+
 config EFI
 	bool "EFI runtime service support"
 	depends on ACPI
diff --git a/arch/x86/include/asm/sgx.h b/arch/x86/include/asm/sgx.h
new file mode 100644
index 000000000000..2130e639ab49
--- /dev/null
+++ b/arch/x86/include/asm/sgx.h
@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause)
+// Copyright(c) 2016-18 Intel Corporation.
+
+#ifndef _ASM_X86_SGX_H
+#define _ASM_X86_SGX_H
+
+#include <linux/types.h>
+
+extern bool sgx_enabled;
+extern bool sgx_lc_enabled;
+
+#endif /* _ASM_X86_SGX_H */
diff --git a/arch/x86/include/asm/sgx_pr.h b/arch/x86/include/asm/sgx_pr.h
new file mode 100644
index 000000000000..42a4185d4bc9
--- /dev/null
+++ b/arch/x86/include/asm/sgx_pr.h
@@ -0,0 +1,13 @@
+// SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause)
+// Copyright(c) 2016-17 Intel Corporation.
+
+#ifndef _ASM_X86_SGX_PR_H
+#define _ASM_X86_SGX_PR_H
+
+#include <linux/printk.h>
+#include <linux/ratelimit.h>
+
+#undef pr_fmt
+#define pr_fmt(fmt) "intel_sgx: " fmt
+
+#endif /* _ASM_X86_SGX_PR_H */
diff --git a/arch/x86/kernel/cpu/Makefile b/arch/x86/kernel/cpu/Makefile
index a66229f51b12..9552ff5b4ec3 100644
--- a/arch/x86/kernel/cpu/Makefile
+++ b/arch/x86/kernel/cpu/Makefile
@@ -36,6 +36,7 @@ obj-$(CONFIG_CPU_SUP_TRANSMETA_32)	+= transmeta.o
 obj-$(CONFIG_CPU_SUP_UMC_32)		+= umc.o
 
 obj-$(CONFIG_INTEL_RDT)	+= intel_rdt.o intel_rdt_rdtgroup.o intel_rdt_monitor.o intel_rdt_ctrlmondata.o
+obj-$(CONFIG_INTEL_SGX_CORE)		+= intel_sgx.o
 
 obj-$(CONFIG_X86_MCE)			+= mcheck/
 obj-$(CONFIG_MTRR)			+= mtrr/
diff --git a/arch/x86/kernel/cpu/intel_sgx.c b/arch/x86/kernel/cpu/intel_sgx.c
new file mode 100644
index 000000000000..77d94115c4cf
--- /dev/null
+++ b/arch/x86/kernel/cpu/intel_sgx.c
@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause)
+// Copyright(c) 2016-17 Intel Corporation.
+
+#include <asm/sgx.h>
+#include <asm/sgx_pr.h>
+#include <linux/freezer.h>
+#include <linux/highmem.h>
+#include <linux/kthread.h>
+#include <linux/ratelimit.h>
+#include <linux/sched/signal.h>
+#include <linux/slab.h>
+
+bool sgx_enabled __ro_after_init;
+EXPORT_SYMBOL(sgx_enabled);
+bool sgx_lc_enabled __ro_after_init;
+EXPORT_SYMBOL(sgx_lc_enabled);
+
+static __init bool sgx_is_enabled(bool *lc_enabled)
+{
+	unsigned long fc;
+
+	if (!boot_cpu_has(X86_FEATURE_SGX))
+		return false;
+
+	if (!boot_cpu_has(X86_FEATURE_SGX1))
+		return false;
+
+	rdmsrl(MSR_IA32_FEATURE_CONTROL, fc);
+	if (!(fc & FEATURE_CONTROL_LOCKED)) {
+		pr_info("IA32_FEATURE_CONTROL MSR is not locked\n");
+		return false;
+	}
+
+	if (!(fc & FEATURE_CONTROL_SGX_ENABLE)) {
+		pr_info("disabled by the firmware\n");
+		return false;
+	}
+
+	if (!(fc & FEATURE_CONTROL_SGX_LE_WR)) {
+		pr_info("IA32_SGXLEPUBKEYHASHn MSRs are not writable\n");
+		return false;
+	}
+
+	*lc_enabled = !!(fc & FEATURE_CONTROL_SGX_LE_WR);
+	return true;
+}
+
+static __init int sgx_init(void)
+{
+	sgx_enabled = sgx_is_enabled(&sgx_lc_enabled);
+	return 0;
+}
+
+arch_initcall(sgx_init);
-- 
2.17.1