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/* SPDX-License-Identifier: GPL-2.0-only */
#include <stdint.h>
#include <cpu/x86/lapic.h>
#include <cpu/x86/cr.h>
#include <cpu/x86/cache.h>
#include <cpu/x86/mp.h>
#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;
}
/**
* 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;
}
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