/* SPDX-License-Identifier: GPL-2.0-only */ #include #include #include #include #include #include #include #include #include #include "txt_register.h" #include "txt_getsec.h" /** * Check for SMX support and enable it if possible. * * Returns false on error, true on success. */ static bool getsec_enabled(void) { unsigned int ecx = cpuid_ecx(1); /* * Check if SMX and VMX is supported by CPU. */ if (!(ecx & CPUID_SMX) || !(ecx & CPUID_VMX)) return false; /* * Check if SMX, VMX and GetSec instructions haven't been disabled. */ msr_t msr = rdmsr(IA32_FEATURE_CONTROL); if ((msr.lo & 0xff06) != 0xff06) return false; /* * Enable SMX. Required to execute GetSec instruction. * Chapter 2.2.4.3 * Intel TXT Software Development Guide (Document: 315168-015) */ write_cr4(read_cr4() | CR4_SMXE); return true; } void enable_getsec_or_reset(void) { msr_t msr = rdmsr(IA32_FEATURE_CONTROL); if (!(msr.lo & FEATURE_CONTROL_LOCK_BIT)) { /* * MSR not locked, enable necessary GETSEC and VMX settings. * We do not lock this MSR here, though. */ msr.lo |= 0xff06; wrmsr(IA32_FEATURE_CONTROL, msr); } else if ((msr.lo & 0xff06) != 0xff06) { /* * MSR is locked without necessary GETSEC and VMX settings. * This can happen after internally reflashing a coreboot * image with different settings, and then doing a warm * reboot. Perform a full reset in order to unlock the MSR. */ printk(BIOS_NOTICE, "IA32_FEATURE_CONTROL MSR locked with GETSEC and/or VMX disabled.\n" "Will perform a full reset to unlock this MSR.\n"); full_reset(); } } /** * Get information as returned by getsec[PARAMETER]. * Arguments can be set to NULL if not needed. * * Returns false on error, true on success. */ bool getsec_parameter(uint32_t *version_mask, uint32_t *version_numbers_supported, uint32_t *max_size_acm_area, uint32_t *memory_type_mask, uint32_t *senter_function_disable, uint32_t *txt_feature_flags) { uint32_t i, eax, ebx, ecx; if (!getsec_enabled()) return false; /* * SAFER MODE EXTENSIONS REFERENCE. * Intel 64 and IA-32 Architectures Software Developer Manuals Vol 2D */ for (i = 0; i < 0x1f; i++) { /* Getsec[PARAMETERS] */ asm volatile ("getsec\n" : "=a" (eax), "=b" (ebx), "=c" (ecx) : "a" (IA32_GETSEC_PARAMETERS), "b" (i) :); switch (eax & 0x1f) { case 0: /* NULL - Exit marker */ return true; case 1: /* Supported AC module versions */ if (version_mask) *version_mask = ebx; if (version_numbers_supported) *version_numbers_supported = ecx; break; case 2: /* Max size of authenticated code execution area */ if (max_size_acm_area) *max_size_acm_area = eax & ~0x1f; break; case 3: /* External memory types supported during AC mode */ if (memory_type_mask) *memory_type_mask = eax; break; case 4: /* Selective SENTER functionality control */ if (senter_function_disable) *senter_function_disable = eax & (0x3f00); break; case 5: /* TXT extensions support */ if (txt_feature_flags) *txt_feature_flags = eax & (0x60); break; } } return true; } /** * Get capabilities as returned by getsec[CAPABILITIES]. * * Returns false on error, true on success. */ bool getsec_capabilities(uint32_t *eax) { if (!getsec_enabled()) return false; asm volatile ("getsec\n" : "=a" (*eax) : "a" (IA32_GETSEC_CAPABILITIES), "b" (0) :); return true; }