graphene/Pal/src/host/Linux-SGX/db_misc.c

/* Copyright (C) 2014 Stony Brook University
   This file is part of Graphene Library OS.

   Graphene Library OS is free software: you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public License
   as published by the Free Software Foundation, either version 3 of the
   License, or (at your option) any later version.

   Graphene Library OS is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

/*
 * db_misc.c
 *
 * This file contains APIs for miscellaneous use.
 */

#include <asm/fcntl.h>
#include <linux/time.h>

#include "api.h"
#include "pal.h"
#include "pal_debug.h"
#include "pal_defs.h"
#include "pal_error.h"
#include "pal_internal.h"
#include "pal_linux.h"
#include "pal_linux_defs.h"
#include "pal_security.h"

#include "sgx_api.h"

unsigned long _DkSystemTimeQuery(void) {
    unsigned long microsec;
    int ret = ocall_gettime(&microsec);
    if (ret)
        return -PAL_ERROR_DENIED;
    return microsec;
}

size_t _DkRandomBitsRead(void* buffer, size_t size) {
    uint32_t rand;
    for (size_t i = 0; i < size; i += sizeof(rand)) {
        rand = rdrand();
        memcpy(buffer + i, &rand, MIN(sizeof(rand), size - i));
    }
    return 0;
}

int _DkInstructionCacheFlush(const void* addr, int size) {
    __UNUSED(addr);
    __UNUSED(size);

    return -PAL_ERROR_NOTIMPLEMENTED;
}

int _DkSegmentRegisterSet(int reg, const void* addr) {
    /* GS is internally used, denied any access to it */
    if (reg != PAL_SEGMENT_FS)
        return -PAL_ERROR_DENIED;

    SET_ENCLAVE_TLS(fsbase, (void*)addr);
    wrfsbase((uint64_t)addr);
    return 0;
}

int _DkSegmentRegisterGet(int reg, void** addr) {
    /* GS is internally used, denied any access to it */
    if (reg != PAL_SEGMENT_FS)
        return -PAL_ERROR_DENIED;

    *addr = (void*)GET_ENCLAVE_TLS(fsbase);
    return 0;
}

#define CPUID_CACHE_SIZE    64
#define CPUID_CACHE_INVALID ((unsigned int)-1)

static PAL_LOCK cpuid_cache_lock = LOCK_INIT;

static struct pal_cpuid {
    unsigned int recently;
    unsigned int leaf, subleaf;
    unsigned int values[4];
} pal_cpuid_cache[CPUID_CACHE_SIZE];

static int pal_cpuid_cache_top      = 0;
static unsigned int pal_cpuid_clock = 0;

int get_cpuid_from_cache(unsigned int leaf, unsigned int subleaf, unsigned int values[4]) {
    _DkInternalLock(&cpuid_cache_lock);

    for (int i = 0; i < pal_cpuid_cache_top; i++)
        if (pal_cpuid_cache[i].leaf == leaf && pal_cpuid_cache[i].subleaf == subleaf) {
            values[0]                   = pal_cpuid_cache[i].values[0];
            values[1]                   = pal_cpuid_cache[i].values[1];
            values[2]                   = pal_cpuid_cache[i].values[2];
            values[3]                   = pal_cpuid_cache[i].values[3];
            pal_cpuid_cache[i].recently = ++pal_cpuid_clock;
            _DkInternalUnlock(&cpuid_cache_lock);
            return 0;
        }

    _DkInternalUnlock(&cpuid_cache_lock);
    return -PAL_ERROR_DENIED;
}

void add_cpuid_to_cache(unsigned int leaf, unsigned int subleaf, unsigned int values[4]) {
    struct pal_cpuid* chosen;
    _DkInternalLock(&cpuid_cache_lock);

    if (pal_cpuid_cache_top < CPUID_CACHE_SIZE) {
        for (int i = 0; i < pal_cpuid_cache_top; i++)
            if (pal_cpuid_cache[i].leaf == leaf && pal_cpuid_cache[i].subleaf == subleaf) {
                _DkInternalUnlock(&cpuid_cache_lock);
                return;
            }

        chosen = &pal_cpuid_cache[pal_cpuid_cache_top++];
    } else {
        unsigned int oldest_clock = pal_cpuid_cache[0].recently;
        chosen                    = &pal_cpuid_cache[0];

        if (pal_cpuid_cache[0].leaf == leaf && pal_cpuid_cache[0].subleaf == subleaf) {
            _DkInternalUnlock(&cpuid_cache_lock);
            return;
        }

        for (int i = 1; i < pal_cpuid_cache_top; i++) {
            if (pal_cpuid_cache[i].leaf == leaf && pal_cpuid_cache[i].subleaf == subleaf) {
                _DkInternalUnlock(&cpuid_cache_lock);
                return;
            }

            if (pal_cpuid_cache[i].recently > oldest_clock) {
                chosen       = &pal_cpuid_cache[i];
                oldest_clock = pal_cpuid_cache[i].recently;
            }
        }
    }

    chosen->leaf      = leaf;
    chosen->subleaf   = subleaf;
    chosen->values[0] = values[0];
    chosen->values[1] = values[1];
    chosen->values[2] = values[2];
    chosen->values[3] = values[3];
    chosen->recently  = ++pal_cpuid_clock;

    _DkInternalUnlock(&cpuid_cache_lock);
}

static inline uint32_t extension_enabled(uint32_t xfrm, uint32_t bit_idx) {
    uint32_t feature_bit = 1U << bit_idx;
    return xfrm & feature_bit;
}

static __sgx_mem_aligned sgx_report_t report;
static __sgx_mem_aligned sgx_target_info_t target_info;
static __sgx_mem_aligned sgx_report_data_t report_data;

/**
 * Initialize the data structures used for CPUID emulation.
 */
void init_cpuid(void) {
    memset(&report, 0, sizeof(report));
    memset(&target_info, 0, sizeof(target_info));
    memset(&report_data, 0, sizeof(report_data));
    sgx_report(&target_info, &report_data, &report);
}

/**
 * Sanity check untrusted CPUID inputs.
 *
 * The basic idea is that there are only a handful of extensions and we know the size needed to
 * store each extension's state. Use this to sanitize host's untrusted cpuid output. We also know
 * through xfrm what extensions are enabled inside the enclave.
 */
static void sanity_check_cpuid(uint32_t leaf, uint32_t subleaf, uint32_t values[4]) {

    uint64_t xfrm = report.body.attributes.xfrm;

    enum cpu_extension {
        x87 = 0, SSE, AVX, MPX_1, MPX_2, AVX512_1, AVX512_2, AVX512_3, PKRU = 9 };
    const uint32_t extension_sizes_bytes[] =
        { [AVX] = 256, [MPX_1] = 64, [MPX_2] = 64, [AVX512_1] = 64, [AVX512_2] = 512,
          [AVX512_3] = 1024, [PKRU] = 8};
    /* Note that AVX offset is 576 bytes and MPX_1 starts at 960. The AVX state size is 256, leaving
     * 128 bytes unaccounted for. */
    const uint32_t extension_offset_bytes[] =
        { [AVX] = 576, [MPX_1] = 960, [MPX_2] = 1024, [AVX512_1] = 1088, [AVX512_2] = 1152,
          [AVX512_3] = 1664, [PKRU] = 2688};
    enum register_index {
        EAX = 0, EBX, ECX, EDX
    };

    const uint32_t EXTENDED_STATE_LEAF = 0xd;

    if (leaf == EXTENDED_STATE_LEAF) {
        switch (subleaf) {
        case 0x0:
            /* From the SDM: "EDX:EAX is a bitmap of all the user state components that can be
             * managed using the XSAVE feature set. A bit can be set in XCR0 if and only if the
             * corresponding bit is set in this bitmap. Every processor that supports the XSAVE
             * feature set will set EAX[0] (x87 state) and EAX[1] (SSE state)."
             *
             * On EENTER/ERESUME, the system installs xfrm into XCR0. Hence, we return xfrm here in
             * EAX.
             */
            values[EAX] = xfrm;

            /* From the SDM: "EBX enumerates the size (in bytes) required by the XSAVE instruction
             * for an XSAVE area containing all the user state components corresponding to bits
             * currently set in XCR0."
             */
            uint32_t xsave_size = 0;
            /* Start from AVX since x87 and SSE are always captured using XSAVE. Also, x87 and SSE
             * state size is implicitly included in the extension's offset, e.g., AVX's offset is
             * 576 which includes x87 and SSE state as well as the XSAVE header. */
            for (int i = AVX; i <= PKRU; i++) {
                if (extension_enabled(xfrm, i)) {
                    xsave_size = extension_offset_bytes[i] + extension_sizes_bytes[i];
                }
            }
            values[EBX] = xsave_size;

            /* From the SDM: "ECX enumerates the size (in bytes) required by the XSAVE instruction
             * for an XSAVE area containing all the user state components supported by this
             * processor."
             *
             * We are assuming here that inside the enclave, ECX and EBX for leaf 0xD and subleaf
             * 0x1 should always be identical, while outside they can potentially be
             * different. Also, outside of SGX EBX can change at runtime, while ECX is a static
             * property.
             */
            values[ECX] = values[EBX];
            values[EDX] = 0;

            break;
        case 0x1: {
            const uint32_t xsave_legacy_size = 512;
            const uint32_t xsave_header = 64;
            uint32_t save_size_bytes = xsave_legacy_size + xsave_header;

            /* Start with AVX, since x87 and SSE state is already included when initializing
             * `save_size_bytes`. */
            for (int i = AVX; i <= PKRU; i++) {
                if (extension_enabled(xfrm, i)) {
                    save_size_bytes += extension_sizes_bytes[i];
                }
            }
            /* EBX reports the actual size occupied by those extensions irrespective of their
             * offsets within the xsave area.
             */
            values[EBX] = save_size_bytes;

            break;
        }
        case AVX:
        case MPX_1:
        case MPX_2:
        case AVX512_1:
        case AVX512_2:
        case AVX512_3:
        case PKRU:
            if (extension_enabled(xfrm, subleaf)) {
                if (values[EAX] != extension_sizes_bytes[subleaf]) {
                    SGX_DBG(DBG_E, "Unexpected value in host CPUID. Exiting...\n");
                    _DkProcessExit(1);
                }
            } else {
                if (values[EAX] != 0) {
                    SGX_DBG(DBG_E, "Unexpected value in host CPUID. Exiting...\n");
                    _DkProcessExit(1);
                }
            }
            break;
        }
    }
}

int _DkCpuIdRetrieve(unsigned int leaf, unsigned int subleaf, unsigned int values[4]) {
    if (!get_cpuid_from_cache(leaf, subleaf, values))
        return 0;

    if (IS_ERR(ocall_cpuid(leaf, subleaf, values)))
        return -PAL_ERROR_DENIED;

    sanity_check_cpuid(leaf, subleaf, values);

    add_cpuid_to_cache(leaf, subleaf, values);
    return 0;
}