linux-sgx-trts-modified/sdk/trts/trts_xsave.cpp

/*
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 * modification, are permitted provided that the following conditions
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 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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#include "arch.h"
#include "xsave.h"
#include "trts_inst.h"
#include "util.h"

// 'SYNTHETIC_STATE' buffer size is (512 + 64 + 256) bytes
//   512 for fxsave buffer,
//   64 for xsave header,
//   256 for YMM State (16 * 16 bytes of each YMMH-register)
// and the buffer should be 64 byte aligned.
#define SYNTHETIC_STATE_SIZE   (512 + 64 + 256)

se_static_assert(SYNTHETIC_STATE_SIZE <= SE_PAGE_SIZE);

static SE_DECLSPEC_ALIGN(4096) const uint16_t
SYNTHETIC_STATE[SYNTHETIC_STATE_SIZE/sizeof(uint16_t)] = {
    0x037F, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x1F80, 0, 0xFFFF, 0
};

static int g_xsave_enabled;             // flag to indicate whether xsave is enabled or not

// EENTER will set xcr0 with secs.attr.xfrm, 
// So use the xfeature mask from report instead of calling xgetbv
uint64_t get_xfeature_state()
{
    // target_info and report_data are useless
    // we only need to make sure their alignment and within enclave
    // so set the pointers to SYNTHETIC_STATE
    sgx_target_info_t *target_info = (sgx_target_info_t *)SYNTHETIC_STATE;
    sgx_report_data_t *report_data = (sgx_report_data_t *)SYNTHETIC_STATE;
    uint8_t buffer[sizeof(sgx_report_t) + REPORT_ALIGN_SIZE -1] = {0};
    sgx_report_t *report = (sgx_report_t *)ROUND_TO((size_t)buffer, REPORT_ALIGN_SIZE);

    do_ereport(target_info, report_data, report);

    g_xsave_enabled = (report->body.attributes.xfrm == SGX_XFRM_LEGACY) ? 0 : 1;
    uint64_t xfrm = report->body.attributes.xfrm;

    // no secrets in target_info, report_data, and report. no need to clear them before return
    // tlibc functions cannot be used before calling init_optimized_libs().

    return xfrm;
}

// save_and_clean_xfeature_regs()
//      do fwait, fxsave, and then clean the extended feature registers
// Parameters:
//      buffer - If the pointer is not NULL, save the CPU state to the memory
// Return Value:
//      none
void save_and_clean_xfeature_regs(uint8_t *buffer)
{
    do_fwait();

    if(buffer != 0)
    {
        uint8_t *buf = (uint8_t*)ROUND_TO((size_t)buffer, FXSAVE_ALIGN_SIZE);
        do_fxsave(buf);
    }

    if(g_xsave_enabled)
    {
        do_xrstor(SYNTHETIC_STATE);
    }
    else
    {
        do_fxrstor(SYNTHETIC_STATE);
    }
}
// restore_xfeature_regs()
//      restore the extended feature registers
//
void restore_xfeature_regs(const uint8_t *buffer)
{
    if(buffer != 0)
    {
        uint8_t *buf = (uint8_t*)ROUND_TO((size_t)buffer, FXSAVE_ALIGN_SIZE);
        do_fxrstor(buf);
    }
}