treewide: remove redundant IS_ERR() before error code check

[linux/fpc-iii.git] / arch / x86 / kernel / fpu / xstate.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * xsave/xrstor support.
 *
 * Author: Suresh Siddha <suresh.b.siddha@intel.com>
 */
#include <linux/compat.h>
#include <linux/cpu.h>
#include <linux/mman.h>
#include <linux/pkeys.h>
#include <linux/seq_file.h>
#include <linux/proc_fs.h>

#include <asm/fpu/api.h>
#include <asm/fpu/internal.h>
#include <asm/fpu/signal.h>
#include <asm/fpu/regset.h>
#include <asm/fpu/xstate.h>

#include <asm/tlbflush.h>
#include <asm/cpufeature.h>

/*
 * Although we spell it out in here, the Processor Trace
 * xfeature is completely unused.  We use other mechanisms
 * to save/restore PT state in Linux.
 */
static const char *xfeature_names[] =
{
        "x87 floating point registers"  ,
        "SSE registers"                 ,
        "AVX registers"                 ,
        "MPX bounds registers"          ,
        "MPX CSR"                       ,
        "AVX-512 opmask"                ,
        "AVX-512 Hi256"                 ,
        "AVX-512 ZMM_Hi256"             ,
        "Processor Trace (unused)"      ,
        "Protection Keys User registers",
        "unknown xstate feature"        ,
};

static short xsave_cpuid_features[] __initdata = {
        X86_FEATURE_FPU,
        X86_FEATURE_XMM,
        X86_FEATURE_AVX,
        X86_FEATURE_MPX,
        X86_FEATURE_MPX,
        X86_FEATURE_AVX512F,
        X86_FEATURE_AVX512F,
        X86_FEATURE_AVX512F,
        X86_FEATURE_INTEL_PT,
        X86_FEATURE_PKU,
};

/*
 * Mask of xstate features supported by the CPU and the kernel:
 */
u64 xfeatures_mask __read_mostly;

static unsigned int xstate_offsets[XFEATURE_MAX] = { [ 0 ... XFEATURE_MAX - 1] = -1};
static unsigned int xstate_sizes[XFEATURE_MAX]   = { [ 0 ... XFEATURE_MAX - 1] = -1};
static unsigned int xstate_comp_offsets[XFEATURE_MAX] = { [ 0 ... XFEATURE_MAX - 1] = -1};

/*
 * The XSAVE area of kernel can be in standard or compacted format;
 * it is always in standard format for user mode. This is the user
 * mode standard format size used for signal and ptrace frames.
 */
unsigned int fpu_user_xstate_size;

/*
 * Return whether the system supports a given xfeature.
 *
 * Also return the name of the (most advanced) feature that the caller requested:
 */
int cpu_has_xfeatures(u64 xfeatures_needed, const char **feature_name)
{
        u64 xfeatures_missing = xfeatures_needed & ~xfeatures_mask;

        if (unlikely(feature_name)) {
                long xfeature_idx, max_idx;
                u64 xfeatures_print;
                /*
                 * So we use FLS here to be able to print the most advanced
                 * feature that was requested but is missing. So if a driver
                 * asks about "XFEATURE_MASK_SSE | XFEATURE_MASK_YMM" we'll print the
                 * missing AVX feature - this is the most informative message
                 * to users:
                 */
                if (xfeatures_missing)
                        xfeatures_print = xfeatures_missing;
                else
                        xfeatures_print = xfeatures_needed;

                xfeature_idx = fls64(xfeatures_print)-1;
                max_idx = ARRAY_SIZE(xfeature_names)-1;
                xfeature_idx = min(xfeature_idx, max_idx);

                *feature_name = xfeature_names[xfeature_idx];
        }

        if (xfeatures_missing)
                return 0;

        return 1;
}
EXPORT_SYMBOL_GPL(cpu_has_xfeatures);

static bool xfeature_is_supervisor(int xfeature_nr)
{
        /*
         * Extended State Enumeration Sub-leaves (EAX = 0DH, ECX = n, n > 1)
         * returns ECX[0] set to (1) for a supervisor state, and cleared (0)
         * for a user state.
         */
        u32 eax, ebx, ecx, edx;

        cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);
        return ecx & 1;
}

static bool xfeature_is_user(int xfeature_nr)
{
        return !xfeature_is_supervisor(xfeature_nr);
}

/*
 * When executing XSAVEOPT (or other optimized XSAVE instructions), if
 * a processor implementation detects that an FPU state component is still
 * (or is again) in its initialized state, it may clear the corresponding
 * bit in the header.xfeatures field, and can skip the writeout of registers
 * to the corresponding memory layout.
 *
 * This means that when the bit is zero, the state component might still contain
 * some previous - non-initialized register state.
 *
 * Before writing xstate information to user-space we sanitize those components,
 * to always ensure that the memory layout of a feature will be in the init state
 * if the corresponding header bit is zero. This is to ensure that user-space doesn't
 * see some stale state in the memory layout during signal handling, debugging etc.
 */
void fpstate_sanitize_xstate(struct fpu *fpu)
{
        struct fxregs_state *fx = &fpu->state.fxsave;
        int feature_bit;
        u64 xfeatures;

        if (!use_xsaveopt())
                return;

        xfeatures = fpu->state.xsave.header.xfeatures;

        /*
         * None of the feature bits are in init state. So nothing else
         * to do for us, as the memory layout is up to date.
         */
        if ((xfeatures & xfeatures_mask) == xfeatures_mask)
                return;

        /*
         * FP is in init state
         */
        if (!(xfeatures & XFEATURE_MASK_FP)) {
                fx->cwd = 0x37f;
                fx->swd = 0;
                fx->twd = 0;
                fx->fop = 0;
                fx->rip = 0;
                fx->rdp = 0;
                memset(&fx->st_space[0], 0, 128);
        }

        /*
         * SSE is in init state
         */
        if (!(xfeatures & XFEATURE_MASK_SSE))
                memset(&fx->xmm_space[0], 0, 256);

        /*
         * First two features are FPU and SSE, which above we handled
         * in a special way already:
         */
        feature_bit = 0x2;
        xfeatures = (xfeatures_mask & ~xfeatures) >> 2;

        /*
         * Update all the remaining memory layouts according to their
         * standard xstate layout, if their header bit is in the init
         * state:
         */
        while (xfeatures) {
                if (xfeatures & 0x1) {
                        int offset = xstate_comp_offsets[feature_bit];
                        int size = xstate_sizes[feature_bit];

                        memcpy((void *)fx + offset,
                               (void *)&init_fpstate.xsave + offset,
                               size);
                }

                xfeatures >>= 1;
                feature_bit++;
        }
}

/*
 * Enable the extended processor state save/restore feature.
 * Called once per CPU onlining.
 */
void fpu__init_cpu_xstate(void)
{
        if (!boot_cpu_has(X86_FEATURE_XSAVE) || !xfeatures_mask)
                return;
        /*
         * Make it clear that XSAVES supervisor states are not yet
         * implemented should anyone expect it to work by changing
         * bits in XFEATURE_MASK_* macros and XCR0.
         */
        WARN_ONCE((xfeatures_mask & XFEATURE_MASK_SUPERVISOR),
                "x86/fpu: XSAVES supervisor states are not yet implemented.\n");

        xfeatures_mask &= ~XFEATURE_MASK_SUPERVISOR;

        cr4_set_bits(X86_CR4_OSXSAVE);
        xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask);
}

/*
 * Note that in the future we will likely need a pair of
 * functions here: one for user xstates and the other for
 * system xstates.  For now, they are the same.
 */
static int xfeature_enabled(enum xfeature xfeature)
{
        return !!(xfeatures_mask & (1UL << xfeature));
}

/*
 * Record the offsets and sizes of various xstates contained
 * in the XSAVE state memory layout.
 */
static void __init setup_xstate_features(void)
{
        u32 eax, ebx, ecx, edx, i;
        /* start at the beginnning of the "extended state" */
        unsigned int last_good_offset = offsetof(struct xregs_state,
                                                 extended_state_area);
        /*
         * The FP xstates and SSE xstates are legacy states. They are always
         * in the fixed offsets in the xsave area in either compacted form
         * or standard form.
         */
        xstate_offsets[XFEATURE_FP]     = 0;
        xstate_sizes[XFEATURE_FP]       = offsetof(struct fxregs_state,
                                                   xmm_space);

        xstate_offsets[XFEATURE_SSE]    = xstate_sizes[XFEATURE_FP];
        xstate_sizes[XFEATURE_SSE]      = sizeof_field(struct fxregs_state,
                                                       xmm_space);

        for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
                if (!xfeature_enabled(i))
                        continue;

                cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx);

                /*
                 * If an xfeature is supervisor state, the offset
                 * in EBX is invalid. We leave it to -1.
                 */
                if (xfeature_is_user(i))
                        xstate_offsets[i] = ebx;

                xstate_sizes[i] = eax;
                /*
                 * In our xstate size checks, we assume that the
                 * highest-numbered xstate feature has the
                 * highest offset in the buffer.  Ensure it does.
                 */
                WARN_ONCE(last_good_offset > xstate_offsets[i],
                        "x86/fpu: misordered xstate at %d\n", last_good_offset);
                last_good_offset = xstate_offsets[i];
        }
}

static void __init print_xstate_feature(u64 xstate_mask)
{
        const char *feature_name;

        if (cpu_has_xfeatures(xstate_mask, &feature_name))
                pr_info("x86/fpu: Supporting XSAVE feature 0x%03Lx: '%s'\n", xstate_mask, feature_name);
}

/*
 * Print out all the supported xstate features:
 */
static void __init print_xstate_features(void)
{
        print_xstate_feature(XFEATURE_MASK_FP);
        print_xstate_feature(XFEATURE_MASK_SSE);
        print_xstate_feature(XFEATURE_MASK_YMM);
        print_xstate_feature(XFEATURE_MASK_BNDREGS);
        print_xstate_feature(XFEATURE_MASK_BNDCSR);
        print_xstate_feature(XFEATURE_MASK_OPMASK);
        print_xstate_feature(XFEATURE_MASK_ZMM_Hi256);
        print_xstate_feature(XFEATURE_MASK_Hi16_ZMM);
        print_xstate_feature(XFEATURE_MASK_PKRU);
}

/*
 * This check is important because it is easy to get XSTATE_*
 * confused with XSTATE_BIT_*.
 */
#define CHECK_XFEATURE(nr) do {         \
        WARN_ON(nr < FIRST_EXTENDED_XFEATURE);  \
        WARN_ON(nr >= XFEATURE_MAX);    \
} while (0)

/*
 * We could cache this like xstate_size[], but we only use
 * it here, so it would be a waste of space.
 */
static int xfeature_is_aligned(int xfeature_nr)
{
        u32 eax, ebx, ecx, edx;

        CHECK_XFEATURE(xfeature_nr);
        cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);
        /*
         * The value returned by ECX[1] indicates the alignment
         * of state component 'i' when the compacted format
         * of the extended region of an XSAVE area is used:
         */
        return !!(ecx & 2);
}

/*
 * This function sets up offsets and sizes of all extended states in
 * xsave area. This supports both standard format and compacted format
 * of the xsave aread.
 */
static void __init setup_xstate_comp(void)
{
        unsigned int xstate_comp_sizes[XFEATURE_MAX];
        int i;

        /*
         * The FP xstates and SSE xstates are legacy states. They are always
         * in the fixed offsets in the xsave area in either compacted form
         * or standard form.
         */
        xstate_comp_offsets[XFEATURE_FP] = 0;
        xstate_comp_offsets[XFEATURE_SSE] = offsetof(struct fxregs_state,
                                                     xmm_space);

        if (!boot_cpu_has(X86_FEATURE_XSAVES)) {
                for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
                        if (xfeature_enabled(i)) {
                                xstate_comp_offsets[i] = xstate_offsets[i];
                                xstate_comp_sizes[i] = xstate_sizes[i];
                        }
                }
                return;
        }

        xstate_comp_offsets[FIRST_EXTENDED_XFEATURE] =
                FXSAVE_SIZE + XSAVE_HDR_SIZE;

        for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
                if (xfeature_enabled(i))
                        xstate_comp_sizes[i] = xstate_sizes[i];
                else
                        xstate_comp_sizes[i] = 0;

                if (i > FIRST_EXTENDED_XFEATURE) {
                        xstate_comp_offsets[i] = xstate_comp_offsets[i-1]
                                        + xstate_comp_sizes[i-1];

                        if (xfeature_is_aligned(i))
                                xstate_comp_offsets[i] =
                                        ALIGN(xstate_comp_offsets[i], 64);
                }
        }
}

/*
 * Print out xstate component offsets and sizes
 */
static void __init print_xstate_offset_size(void)
{
        int i;

        for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
                if (!xfeature_enabled(i))
                        continue;
                pr_info("x86/fpu: xstate_offset[%d]: %4d, xstate_sizes[%d]: %4d\n",
                         i, xstate_comp_offsets[i], i, xstate_sizes[i]);
        }
}

/*
 * setup the xstate image representing the init state
 */
static void __init setup_init_fpu_buf(void)
{
        static int on_boot_cpu __initdata = 1;

        WARN_ON_FPU(!on_boot_cpu);
        on_boot_cpu = 0;

        if (!boot_cpu_has(X86_FEATURE_XSAVE))
                return;

        setup_xstate_features();
        print_xstate_features();

        if (boot_cpu_has(X86_FEATURE_XSAVES))
                init_fpstate.xsave.header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT |
                                                     xfeatures_mask;

        /*
         * Init all the features state with header.xfeatures being 0x0
         */
        copy_kernel_to_xregs_booting(&init_fpstate.xsave);

        /*
         * Dump the init state again. This is to identify the init state
         * of any feature which is not represented by all zero's.
         */
        copy_xregs_to_kernel_booting(&init_fpstate.xsave);
}

static int xfeature_uncompacted_offset(int xfeature_nr)
{
        u32 eax, ebx, ecx, edx;

        /*
         * Only XSAVES supports supervisor states and it uses compacted
         * format. Checking a supervisor state's uncompacted offset is
         * an error.
         */
        if (XFEATURE_MASK_SUPERVISOR & BIT_ULL(xfeature_nr)) {
                WARN_ONCE(1, "No fixed offset for xstate %d\n", xfeature_nr);
                return -1;
        }

        CHECK_XFEATURE(xfeature_nr);
        cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);
        return ebx;
}

static int xfeature_size(int xfeature_nr)
{
        u32 eax, ebx, ecx, edx;

        CHECK_XFEATURE(xfeature_nr);
        cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);
        return eax;
}

/*
 * 'XSAVES' implies two different things:
 * 1. saving of supervisor/system state
 * 2. using the compacted format
 *
 * Use this function when dealing with the compacted format so
 * that it is obvious which aspect of 'XSAVES' is being handled
 * by the calling code.
 */
int using_compacted_format(void)
{
        return boot_cpu_has(X86_FEATURE_XSAVES);
}

/* Validate an xstate header supplied by userspace (ptrace or sigreturn) */
int validate_xstate_header(const struct xstate_header *hdr)
{
        /* No unknown or supervisor features may be set */
        if (hdr->xfeatures & (~xfeatures_mask | XFEATURE_MASK_SUPERVISOR))
                return -EINVAL;

        /* Userspace must use the uncompacted format */
        if (hdr->xcomp_bv)
                return -EINVAL;

        /*
         * If 'reserved' is shrunken to add a new field, make sure to validate
         * that new field here!
         */
        BUILD_BUG_ON(sizeof(hdr->reserved) != 48);

        /* No reserved bits may be set */
        if (memchr_inv(hdr->reserved, 0, sizeof(hdr->reserved)))
                return -EINVAL;

        return 0;
}

static void __xstate_dump_leaves(void)
{
        int i;
        u32 eax, ebx, ecx, edx;
        static int should_dump = 1;

        if (!should_dump)
                return;
        should_dump = 0;
        /*
         * Dump out a few leaves past the ones that we support
         * just in case there are some goodies up there
         */
        for (i = 0; i < XFEATURE_MAX + 10; i++) {
                cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx);
                pr_warn("CPUID[%02x, %02x]: eax=%08x ebx=%08x ecx=%08x edx=%08x\n",
                        XSTATE_CPUID, i, eax, ebx, ecx, edx);
        }
}

#define XSTATE_WARN_ON(x) do {                                                  \
        if (WARN_ONCE(x, "XSAVE consistency problem, dumping leaves")) {        \
                __xstate_dump_leaves();                                         \
        }                                                                       \
} while (0)

#define XCHECK_SZ(sz, nr, nr_macro, __struct) do {                      \
        if ((nr == nr_macro) &&                                         \
            WARN_ONCE(sz != sizeof(__struct),                           \
                "%s: struct is %zu bytes, cpu state %d bytes\n",        \
                __stringify(nr_macro), sizeof(__struct), sz)) {         \
                __xstate_dump_leaves();                                 \
        }                                                               \
} while (0)

/*
 * We have a C struct for each 'xstate'.  We need to ensure
 * that our software representation matches what the CPU
 * tells us about the state's size.
 */
static void check_xstate_against_struct(int nr)
{
        /*
         * Ask the CPU for the size of the state.
         */
        int sz = xfeature_size(nr);
        /*
         * Match each CPU state with the corresponding software
         * structure.
         */
        XCHECK_SZ(sz, nr, XFEATURE_YMM,       struct ymmh_struct);
        XCHECK_SZ(sz, nr, XFEATURE_BNDREGS,   struct mpx_bndreg_state);
        XCHECK_SZ(sz, nr, XFEATURE_BNDCSR,    struct mpx_bndcsr_state);
        XCHECK_SZ(sz, nr, XFEATURE_OPMASK,    struct avx_512_opmask_state);
        XCHECK_SZ(sz, nr, XFEATURE_ZMM_Hi256, struct avx_512_zmm_uppers_state);
        XCHECK_SZ(sz, nr, XFEATURE_Hi16_ZMM,  struct avx_512_hi16_state);
        XCHECK_SZ(sz, nr, XFEATURE_PKRU,      struct pkru_state);

        /*
         * Make *SURE* to add any feature numbers in below if
         * there are "holes" in the xsave state component
         * numbers.
         */
        if ((nr < XFEATURE_YMM) ||
            (nr >= XFEATURE_MAX) ||
            (nr == XFEATURE_PT_UNIMPLEMENTED_SO_FAR)) {
                WARN_ONCE(1, "no structure for xstate: %d\n", nr);
                XSTATE_WARN_ON(1);
        }
}

/*
 * This essentially double-checks what the cpu told us about
 * how large the XSAVE buffer needs to be.  We are recalculating
 * it to be safe.
 */
static void do_extra_xstate_size_checks(void)
{
        int paranoid_xstate_size = FXSAVE_SIZE + XSAVE_HDR_SIZE;
        int i;

        for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
                if (!xfeature_enabled(i))
                        continue;

                check_xstate_against_struct(i);
                /*
                 * Supervisor state components can be managed only by
                 * XSAVES, which is compacted-format only.
                 */
                if (!using_compacted_format())
                        XSTATE_WARN_ON(xfeature_is_supervisor(i));

                /* Align from the end of the previous feature */
                if (xfeature_is_aligned(i))
                        paranoid_xstate_size = ALIGN(paranoid_xstate_size, 64);
                /*
                 * The offset of a given state in the non-compacted
                 * format is given to us in a CPUID leaf.  We check
                 * them for being ordered (increasing offsets) in
                 * setup_xstate_features().
                 */
                if (!using_compacted_format())
                        paranoid_xstate_size = xfeature_uncompacted_offset(i);
                /*
                 * The compacted-format offset always depends on where
                 * the previous state ended.
                 */
                paranoid_xstate_size += xfeature_size(i);
        }
        XSTATE_WARN_ON(paranoid_xstate_size != fpu_kernel_xstate_size);
}


/*
 * Get total size of enabled xstates in XCR0/xfeatures_mask.
 *
 * Note the SDM's wording here.  "sub-function 0" only enumerates
 * the size of the *user* states.  If we use it to size a buffer
 * that we use 'XSAVES' on, we could potentially overflow the
 * buffer because 'XSAVES' saves system states too.
 *
 * Note that we do not currently set any bits on IA32_XSS so
 * 'XCR0 | IA32_XSS == XCR0' for now.
 */
static unsigned int __init get_xsaves_size(void)
{
        unsigned int eax, ebx, ecx, edx;
        /*
         * - CPUID function 0DH, sub-function 1:
         *    EBX enumerates the size (in bytes) required by
         *    the XSAVES instruction for an XSAVE area
         *    containing all the state components
         *    corresponding to bits currently set in
         *    XCR0 | IA32_XSS.
         */
        cpuid_count(XSTATE_CPUID, 1, &eax, &ebx, &ecx, &edx);
        return ebx;
}

static unsigned int __init get_xsave_size(void)
{
        unsigned int eax, ebx, ecx, edx;
        /*
         * - CPUID function 0DH, sub-function 0:
         *    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.
         */
        cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
        return ebx;
}

/*
 * Will the runtime-enumerated 'xstate_size' fit in the init
 * task's statically-allocated buffer?
 */
static bool is_supported_xstate_size(unsigned int test_xstate_size)
{
        if (test_xstate_size <= sizeof(union fpregs_state))
                return true;

        pr_warn("x86/fpu: xstate buffer too small (%zu < %d), disabling xsave\n",
                        sizeof(union fpregs_state), test_xstate_size);
        return false;
}

static int __init init_xstate_size(void)
{
        /* Recompute the context size for enabled features: */
        unsigned int possible_xstate_size;
        unsigned int xsave_size;

        xsave_size = get_xsave_size();

        if (boot_cpu_has(X86_FEATURE_XSAVES))
                possible_xstate_size = get_xsaves_size();
        else
                possible_xstate_size = xsave_size;

        /* Ensure we have the space to store all enabled: */
        if (!is_supported_xstate_size(possible_xstate_size))
                return -EINVAL;

        /*
         * The size is OK, we are definitely going to use xsave,
         * make it known to the world that we need more space.
         */
        fpu_kernel_xstate_size = possible_xstate_size;
        do_extra_xstate_size_checks();

        /*
         * User space is always in standard format.
         */
        fpu_user_xstate_size = xsave_size;
        return 0;
}

/*
 * We enabled the XSAVE hardware, but something went wrong and
 * we can not use it.  Disable it.
 */
static void fpu__init_disable_system_xstate(void)
{
        xfeatures_mask = 0;
        cr4_clear_bits(X86_CR4_OSXSAVE);
        setup_clear_cpu_cap(X86_FEATURE_XSAVE);
}

/*
 * Enable and initialize the xsave feature.
 * Called once per system bootup.
 */
void __init fpu__init_system_xstate(void)
{
        unsigned int eax, ebx, ecx, edx;
        static int on_boot_cpu __initdata = 1;
        int err;
        int i;

        WARN_ON_FPU(!on_boot_cpu);
        on_boot_cpu = 0;

        if (!boot_cpu_has(X86_FEATURE_FPU)) {
                pr_info("x86/fpu: No FPU detected\n");
                return;
        }

        if (!boot_cpu_has(X86_FEATURE_XSAVE)) {
                pr_info("x86/fpu: x87 FPU will use %s\n",
                        boot_cpu_has(X86_FEATURE_FXSR) ? "FXSAVE" : "FSAVE");
                return;
        }

        if (boot_cpu_data.cpuid_level < XSTATE_CPUID) {
                WARN_ON_FPU(1);
                return;
        }

        cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
        xfeatures_mask = eax + ((u64)edx << 32);

        if ((xfeatures_mask & XFEATURE_MASK_FPSSE) != XFEATURE_MASK_FPSSE) {
                /*
                 * This indicates that something really unexpected happened
                 * with the enumeration.  Disable XSAVE and try to continue
                 * booting without it.  This is too early to BUG().
                 */
                pr_err("x86/fpu: FP/SSE not present amongst the CPU's xstate features: 0x%llx.\n", xfeatures_mask);
                goto out_disable;
        }

        /*
         * Clear XSAVE features that are disabled in the normal CPUID.
         */
        for (i = 0; i < ARRAY_SIZE(xsave_cpuid_features); i++) {
                if (!boot_cpu_has(xsave_cpuid_features[i]))
                        xfeatures_mask &= ~BIT(i);
        }

        xfeatures_mask &= fpu__get_supported_xfeatures_mask();

        /* Enable xstate instructions to be able to continue with initialization: */
        fpu__init_cpu_xstate();
        err = init_xstate_size();
        if (err)
                goto out_disable;

        /*
         * Update info used for ptrace frames; use standard-format size and no
         * supervisor xstates:
         */
        update_regset_xstate_info(fpu_user_xstate_size, xfeatures_mask & ~XFEATURE_MASK_SUPERVISOR);

        fpu__init_prepare_fx_sw_frame();
        setup_init_fpu_buf();
        setup_xstate_comp();
        print_xstate_offset_size();

        pr_info("x86/fpu: Enabled xstate features 0x%llx, context size is %d bytes, using '%s' format.\n",
                xfeatures_mask,
                fpu_kernel_xstate_size,
                boot_cpu_has(X86_FEATURE_XSAVES) ? "compacted" : "standard");
        return;

out_disable:
        /* something went wrong, try to boot without any XSAVE support */
        fpu__init_disable_system_xstate();
}

/*
 * Restore minimal FPU state after suspend:
 */
void fpu__resume_cpu(void)
{
        /*
         * Restore XCR0 on xsave capable CPUs:
         */
        if (boot_cpu_has(X86_FEATURE_XSAVE))
                xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask);
}

/*
 * Given an xstate feature nr, calculate where in the xsave
 * buffer the state is.  Callers should ensure that the buffer
 * is valid.
 */
static void *__raw_xsave_addr(struct xregs_state *xsave, int xfeature_nr)
{
        if (!xfeature_enabled(xfeature_nr)) {
                WARN_ON_FPU(1);
                return NULL;
        }

        return (void *)xsave + xstate_comp_offsets[xfeature_nr];
}
/*
 * Given the xsave area and a state inside, this function returns the
 * address of the state.
 *
 * This is the API that is called to get xstate address in either
 * standard format or compacted format of xsave area.
 *
 * Note that if there is no data for the field in the xsave buffer
 * this will return NULL.
 *
 * Inputs:
 *      xstate: the thread's storage area for all FPU data
 *      xfeature_nr: state which is defined in xsave.h (e.g. XFEATURE_FP,
 *      XFEATURE_SSE, etc...)
 * Output:
 *      address of the state in the xsave area, or NULL if the
 *      field is not present in the xsave buffer.
 */
void *get_xsave_addr(struct xregs_state *xsave, int xfeature_nr)
{
        /*
         * Do we even *have* xsave state?
         */
        if (!boot_cpu_has(X86_FEATURE_XSAVE))
                return NULL;

        /*
         * We should not ever be requesting features that we
         * have not enabled.  Remember that xfeatures_mask is
         * what we write to the XCR0 register.
         */
        WARN_ONCE(!(xfeatures_mask & BIT_ULL(xfeature_nr)),
                  "get of unsupported state");
        /*
         * This assumes the last 'xsave*' instruction to
         * have requested that 'xfeature_nr' be saved.
         * If it did not, we might be seeing and old value
         * of the field in the buffer.
         *
         * This can happen because the last 'xsave' did not
         * request that this feature be saved (unlikely)
         * or because the "init optimization" caused it
         * to not be saved.
         */
        if (!(xsave->header.xfeatures & BIT_ULL(xfeature_nr)))
                return NULL;

        return __raw_xsave_addr(xsave, xfeature_nr);
}
EXPORT_SYMBOL_GPL(get_xsave_addr);

/*
 * This wraps up the common operations that need to occur when retrieving
 * data from xsave state.  It first ensures that the current task was
 * using the FPU and retrieves the data in to a buffer.  It then calculates
 * the offset of the requested field in the buffer.
 *
 * This function is safe to call whether the FPU is in use or not.
 *
 * Note that this only works on the current task.
 *
 * Inputs:
 *      @xfeature_nr: state which is defined in xsave.h (e.g. XFEATURE_FP,
 *      XFEATURE_SSE, etc...)
 * Output:
 *      address of the state in the xsave area or NULL if the state
 *      is not present or is in its 'init state'.
 */
const void *get_xsave_field_ptr(int xfeature_nr)
{
        struct fpu *fpu = &current->thread.fpu;

        /*
         * fpu__save() takes the CPU's xstate registers
         * and saves them off to the 'fpu memory buffer.
         */
        fpu__save(fpu);

        return get_xsave_addr(&fpu->state.xsave, xfeature_nr);
}

#ifdef CONFIG_ARCH_HAS_PKEYS

#define NR_VALID_PKRU_BITS (CONFIG_NR_PROTECTION_KEYS * 2)
#define PKRU_VALID_MASK (NR_VALID_PKRU_BITS - 1)
/*
 * This will go out and modify PKRU register to set the access
 * rights for @pkey to @init_val.
 */
int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
                unsigned long init_val)
{
        u32 old_pkru;
        int pkey_shift = (pkey * PKRU_BITS_PER_PKEY);
        u32 new_pkru_bits = 0;

        /*
         * This check implies XSAVE support.  OSPKE only gets
         * set if we enable XSAVE and we enable PKU in XCR0.
         */
        if (!boot_cpu_has(X86_FEATURE_OSPKE))
                return -EINVAL;

        /* Set the bits we need in PKRU:  */
        if (init_val & PKEY_DISABLE_ACCESS)
                new_pkru_bits |= PKRU_AD_BIT;
        if (init_val & PKEY_DISABLE_WRITE)
                new_pkru_bits |= PKRU_WD_BIT;

        /* Shift the bits in to the correct place in PKRU for pkey: */
        new_pkru_bits <<= pkey_shift;

        /* Get old PKRU and mask off any old bits in place: */
        old_pkru = read_pkru();
        old_pkru &= ~((PKRU_AD_BIT|PKRU_WD_BIT) << pkey_shift);

        /* Write old part along with new part: */
        write_pkru(old_pkru | new_pkru_bits);

        return 0;
}
#endif /* ! CONFIG_ARCH_HAS_PKEYS */

/*
 * Weird legacy quirk: SSE and YMM states store information in the
 * MXCSR and MXCSR_FLAGS fields of the FP area. That means if the FP
 * area is marked as unused in the xfeatures header, we need to copy
 * MXCSR and MXCSR_FLAGS if either SSE or YMM are in use.
 */
static inline bool xfeatures_mxcsr_quirk(u64 xfeatures)
{
        if (!(xfeatures & (XFEATURE_MASK_SSE|XFEATURE_MASK_YMM)))
                return false;

        if (xfeatures & XFEATURE_MASK_FP)
                return false;

        return true;
}

/*
 * This is similar to user_regset_copyout(), but will not add offset to
 * the source data pointer or increment pos, count, kbuf, and ubuf.
 */
static inline void
__copy_xstate_to_kernel(void *kbuf, const void *data,
                        unsigned int offset, unsigned int size, unsigned int size_total)
{
        if (offset < size_total) {
                unsigned int copy = min(size, size_total - offset);

                memcpy(kbuf + offset, data, copy);
        }
}

/*
 * Convert from kernel XSAVES compacted format to standard format and copy
 * to a kernel-space ptrace buffer.
 *
 * It supports partial copy but pos always starts from zero. This is called
 * from xstateregs_get() and there we check the CPU has XSAVES.
 */
int copy_xstate_to_kernel(void *kbuf, struct xregs_state *xsave, unsigned int offset_start, unsigned int size_total)
{
        unsigned int offset, size;
        struct xstate_header header;
        int i;

        /*
         * Currently copy_regset_to_user() starts from pos 0:
         */
        if (unlikely(offset_start != 0))
                return -EFAULT;

        /*
         * The destination is a ptrace buffer; we put in only user xstates:
         */
        memset(&header, 0, sizeof(header));
        header.xfeatures = xsave->header.xfeatures;
        header.xfeatures &= ~XFEATURE_MASK_SUPERVISOR;

        /*
         * Copy xregs_state->header:
         */
        offset = offsetof(struct xregs_state, header);
        size = sizeof(header);

        __copy_xstate_to_kernel(kbuf, &header, offset, size, size_total);

        for (i = 0; i < XFEATURE_MAX; i++) {
                /*
                 * Copy only in-use xstates:
                 */
                if ((header.xfeatures >> i) & 1) {
                        void *src = __raw_xsave_addr(xsave, i);

                        offset = xstate_offsets[i];
                        size = xstate_sizes[i];

                        /* The next component has to fit fully into the output buffer: */
                        if (offset + size > size_total)
                                break;

                        __copy_xstate_to_kernel(kbuf, src, offset, size, size_total);
                }

        }

        if (xfeatures_mxcsr_quirk(header.xfeatures)) {
                offset = offsetof(struct fxregs_state, mxcsr);
                size = MXCSR_AND_FLAGS_SIZE;
                __copy_xstate_to_kernel(kbuf, &xsave->i387.mxcsr, offset, size, size_total);
        }

        /*
         * Fill xsave->i387.sw_reserved value for ptrace frame:
         */
        offset = offsetof(struct fxregs_state, sw_reserved);
        size = sizeof(xstate_fx_sw_bytes);

        __copy_xstate_to_kernel(kbuf, xstate_fx_sw_bytes, offset, size, size_total);

        return 0;
}

static inline int
__copy_xstate_to_user(void __user *ubuf, const void *data, unsigned int offset, unsigned int size, unsigned int size_total)
{
        if (!size)
                return 0;

        if (offset < size_total) {
                unsigned int copy = min(size, size_total - offset);

                if (__copy_to_user(ubuf + offset, data, copy))
                        return -EFAULT;
        }
        return 0;
}

/*
 * Convert from kernel XSAVES compacted format to standard format and copy
 * to a user-space buffer. It supports partial copy but pos always starts from
 * zero. This is called from xstateregs_get() and there we check the CPU
 * has XSAVES.
 */
int copy_xstate_to_user(void __user *ubuf, struct xregs_state *xsave, unsigned int offset_start, unsigned int size_total)
{
        unsigned int offset, size;
        int ret, i;
        struct xstate_header header;

        /*
         * Currently copy_regset_to_user() starts from pos 0:
         */
        if (unlikely(offset_start != 0))
                return -EFAULT;

        /*
         * The destination is a ptrace buffer; we put in only user xstates:
         */
        memset(&header, 0, sizeof(header));
        header.xfeatures = xsave->header.xfeatures;
        header.xfeatures &= ~XFEATURE_MASK_SUPERVISOR;

        /*
         * Copy xregs_state->header:
         */
        offset = offsetof(struct xregs_state, header);
        size = sizeof(header);

        ret = __copy_xstate_to_user(ubuf, &header, offset, size, size_total);
        if (ret)
                return ret;

        for (i = 0; i < XFEATURE_MAX; i++) {
                /*
                 * Copy only in-use xstates:
                 */
                if ((header.xfeatures >> i) & 1) {
                        void *src = __raw_xsave_addr(xsave, i);

                        offset = xstate_offsets[i];
                        size = xstate_sizes[i];

                        /* The next component has to fit fully into the output buffer: */
                        if (offset + size > size_total)
                                break;

                        ret = __copy_xstate_to_user(ubuf, src, offset, size, size_total);
                        if (ret)
                                return ret;
                }

        }

        if (xfeatures_mxcsr_quirk(header.xfeatures)) {
                offset = offsetof(struct fxregs_state, mxcsr);
                size = MXCSR_AND_FLAGS_SIZE;
                __copy_xstate_to_user(ubuf, &xsave->i387.mxcsr, offset, size, size_total);
        }

        /*
         * Fill xsave->i387.sw_reserved value for ptrace frame:
         */
        offset = offsetof(struct fxregs_state, sw_reserved);
        size = sizeof(xstate_fx_sw_bytes);

        ret = __copy_xstate_to_user(ubuf, xstate_fx_sw_bytes, offset, size, size_total);
        if (ret)
                return ret;

        return 0;
}

/*
 * Convert from a ptrace standard-format kernel buffer to kernel XSAVES format
 * and copy to the target thread. This is called from xstateregs_set().
 */
int copy_kernel_to_xstate(struct xregs_state *xsave, const void *kbuf)
{
        unsigned int offset, size;
        int i;
        struct xstate_header hdr;

        offset = offsetof(struct xregs_state, header);
        size = sizeof(hdr);

        memcpy(&hdr, kbuf + offset, size);

        if (validate_xstate_header(&hdr))
                return -EINVAL;

        for (i = 0; i < XFEATURE_MAX; i++) {
                u64 mask = ((u64)1 << i);

                if (hdr.xfeatures & mask) {
                        void *dst = __raw_xsave_addr(xsave, i);

                        offset = xstate_offsets[i];
                        size = xstate_sizes[i];

                        memcpy(dst, kbuf + offset, size);
                }
        }

        if (xfeatures_mxcsr_quirk(hdr.xfeatures)) {
                offset = offsetof(struct fxregs_state, mxcsr);
                size = MXCSR_AND_FLAGS_SIZE;
                memcpy(&xsave->i387.mxcsr, kbuf + offset, size);
        }

        /*
         * The state that came in from userspace was user-state only.
         * Mask all the user states out of 'xfeatures':
         */
        xsave->header.xfeatures &= XFEATURE_MASK_SUPERVISOR;

        /*
         * Add back in the features that came in from userspace:
         */
        xsave->header.xfeatures |= hdr.xfeatures;

        return 0;
}

/*
 * Convert from a ptrace or sigreturn standard-format user-space buffer to
 * kernel XSAVES format and copy to the target thread. This is called from
 * xstateregs_set(), as well as potentially from the sigreturn() and
 * rt_sigreturn() system calls.
 */
int copy_user_to_xstate(struct xregs_state *xsave, const void __user *ubuf)
{
        unsigned int offset, size;
        int i;
        struct xstate_header hdr;

        offset = offsetof(struct xregs_state, header);
        size = sizeof(hdr);

        if (__copy_from_user(&hdr, ubuf + offset, size))
                return -EFAULT;

        if (validate_xstate_header(&hdr))
                return -EINVAL;

        for (i = 0; i < XFEATURE_MAX; i++) {
                u64 mask = ((u64)1 << i);

                if (hdr.xfeatures & mask) {
                        void *dst = __raw_xsave_addr(xsave, i);

                        offset = xstate_offsets[i];
                        size = xstate_sizes[i];

                        if (__copy_from_user(dst, ubuf + offset, size))
                                return -EFAULT;
                }
        }

        if (xfeatures_mxcsr_quirk(hdr.xfeatures)) {
                offset = offsetof(struct fxregs_state, mxcsr);
                size = MXCSR_AND_FLAGS_SIZE;
                if (__copy_from_user(&xsave->i387.mxcsr, ubuf + offset, size))
                        return -EFAULT;
        }

        /*
         * The state that came in from userspace was user-state only.
         * Mask all the user states out of 'xfeatures':
         */
        xsave->header.xfeatures &= XFEATURE_MASK_SUPERVISOR;

        /*
         * Add back in the features that came in from userspace:
         */
        xsave->header.xfeatures |= hdr.xfeatures;

        return 0;
}

#ifdef CONFIG_PROC_PID_ARCH_STATUS
/*
 * Report the amount of time elapsed in millisecond since last AVX512
 * use in the task.
 */
static void avx512_status(struct seq_file *m, struct task_struct *task)
{
        unsigned long timestamp = READ_ONCE(task->thread.fpu.avx512_timestamp);
        long delta;

        if (!timestamp) {
                /*
                 * Report -1 if no AVX512 usage
                 */
                delta = -1;
        } else {
                delta = (long)(jiffies - timestamp);
                /*
                 * Cap to LONG_MAX if time difference > LONG_MAX
                 */
                if (delta < 0)
                        delta = LONG_MAX;
                delta = jiffies_to_msecs(delta);
        }

        seq_put_decimal_ll(m, "AVX512_elapsed_ms:\t", delta);
        seq_putc(m, '\n');
}

/*
 * Report architecture specific information
 */
int proc_pid_arch_status(struct seq_file *m, struct pid_namespace *ns,
                        struct pid *pid, struct task_struct *task)
{
        /*
         * Report AVX512 state if the processor and build option supported.
         */
        if (cpu_feature_enabled(X86_FEATURE_AVX512F))
                avx512_status(m, task);

        return 0;
}
#endif /* CONFIG_PROC_PID_ARCH_STATUS */