// SPDX-License-Identifier: GPL-2.0
/*
 * FPU signal frame handling routines.
 */

#include <linux/compat.h>
#include <linux/cpu.h>
#include <linux/pagemap.h>

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

#include <asm/sigframe.h>
#include <asm/trace/fpu.h>

static struct _fpx_sw_bytes fx_sw_reserved __ro_after_init;
static struct _fpx_sw_bytes fx_sw_reserved_ia32 __ro_after_init;

/*
 * Check for the presence of extended state information in the
 * user fpstate pointer in the sigcontext.
 */
static inline int check_xstate_in_sigframe(struct fxregs_state __user *fxbuf,
                                           struct _fpx_sw_bytes *fx_sw)
{
        int min_xstate_size = sizeof(struct fxregs_state) +
                              sizeof(struct xstate_header);
        void __user *fpstate = fxbuf;
        unsigned int magic2;

        if (__copy_from_user(fx_sw, &fxbuf->sw_reserved[0], sizeof(*fx_sw)))
                return -EFAULT;

        /* Check for the first magic field and other error scenarios. */
        if (fx_sw->magic1 != FP_XSTATE_MAGIC1 ||
            fx_sw->xstate_size < min_xstate_size ||
            fx_sw->xstate_size > fpu_user_xstate_size ||
            fx_sw->xstate_size > fx_sw->extended_size)
                goto setfx;

        /*
         * Check for the presence of second magic word at the end of memory
         * layout. This detects the case where the user just copied the legacy
         * fpstate layout with out copying the extended state information
         * in the memory layout.
         */
        if (__get_user(magic2, (__u32 __user *)(fpstate + fx_sw->xstate_size)))
                return -EFAULT;

        if (likely(magic2 == FP_XSTATE_MAGIC2))
                return 0;
setfx:
        trace_x86_fpu_xstate_check_failed(&current->thread.fpu);

        /* Set the parameters for fx only state */
        fx_sw->magic1 = 0;
        fx_sw->xstate_size = sizeof(struct fxregs_state);
        fx_sw->xfeatures = XFEATURE_MASK_FPSSE;
        return 0;
}

/*
 * Signal frame handlers.
 */
static inline int save_fsave_header(struct task_struct *tsk, void __user *buf)
{
        if (use_fxsr()) {
                struct xregs_state *xsave = &tsk->thread.fpu.state.xsave;
                struct user_i387_ia32_struct env;
                struct _fpstate_32 __user *fp = buf;

                fpregs_lock();
                if (!test_thread_flag(TIF_NEED_FPU_LOAD))
                        fxsave(&tsk->thread.fpu.state.fxsave);
                fpregs_unlock();

                convert_from_fxsr(&env, tsk);

                if (__copy_to_user(buf, &env, sizeof(env)) ||
                    __put_user(xsave->i387.swd, &fp->status) ||
                    __put_user(X86_FXSR_MAGIC, &fp->magic))
                        return -1;
        } else {
                struct fregs_state __user *fp = buf;
                u32 swd;
                if (__get_user(swd, &fp->swd) || __put_user(swd, &fp->status))
                        return -1;
        }

        return 0;
}

static inline int save_xstate_epilog(void __user *buf, int ia32_frame)
{
        struct xregs_state __user *x = buf;
        struct _fpx_sw_bytes *sw_bytes;
        u32 xfeatures;
        int err;

        /* Setup the bytes not touched by the [f]xsave and reserved for SW. */
        sw_bytes = ia32_frame ? &fx_sw_reserved_ia32 : &fx_sw_reserved;
        err = __copy_to_user(&x->i387.sw_reserved, sw_bytes, sizeof(*sw_bytes));

        if (!use_xsave())
                return err;

        err |= __put_user(FP_XSTATE_MAGIC2,
                          (__u32 __user *)(buf + fpu_user_xstate_size));

        /*
         * Read the xfeatures which we copied (directly from the cpu or
         * from the state in task struct) to the user buffers.
         */
        err |= __get_user(xfeatures, (__u32 __user *)&x->header.xfeatures);

        /*
         * For legacy compatible, we always set FP/SSE bits in the bit
         * vector while saving the state to the user context. This will
         * enable us capturing any changes(during sigreturn) to
         * the FP/SSE bits by the legacy applications which don't touch
         * xfeatures in the xsave header.
         *
         * xsave aware apps can change the xfeatures in the xsave
         * header as well as change any contents in the memory layout.
         * xrestore as part of sigreturn will capture all the changes.
         */
        xfeatures |= XFEATURE_MASK_FPSSE;

        err |= __put_user(xfeatures, (__u32 __user *)&x->header.xfeatures);

        return err;
}

static inline int copy_fpregs_to_sigframe(struct xregs_state __user *buf)
{
        int err;

        if (use_xsave())
                err = xsave_to_user_sigframe(buf);
        else if (use_fxsr())
                err = fxsave_to_user_sigframe((struct fxregs_state __user *) buf);
        else
                err = fnsave_to_user_sigframe((struct fregs_state __user *) buf);

        if (unlikely(err) && __clear_user(buf, fpu_user_xstate_size))
                err = -EFAULT;
        return err;
}

/*
 * Save the fpu, extended register state to the user signal frame.
 *
 * 'buf_fx' is the 64-byte aligned pointer at which the [f|fx|x]save
 *  state is copied.
 *  'buf' points to the 'buf_fx' or to the fsave header followed by 'buf_fx'.
 *
 *      buf == buf_fx for 64-bit frames and 32-bit fsave frame.
 *      buf != buf_fx for 32-bit frames with fxstate.
 *
 * Try to save it directly to the user frame with disabled page fault handler.
 * If this fails then do the slow path where the FPU state is first saved to
 * task's fpu->state and then copy it to the user frame pointed to by the
 * aligned pointer 'buf_fx'.
 *
 * If this is a 32-bit frame with fxstate, put a fsave header before
 * the aligned state at 'buf_fx'.
 *
 * For [f]xsave state, update the SW reserved fields in the [f]xsave frame
 * indicating the absence/presence of the extended state to the user.
 */
int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
{
        struct task_struct *tsk = current;
        int ia32_fxstate = (buf != buf_fx);
        int ret;

        ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) ||
                         IS_ENABLED(CONFIG_IA32_EMULATION));

        if (!static_cpu_has(X86_FEATURE_FPU)) {
                struct user_i387_ia32_struct fp;
                fpregs_soft_get(current, NULL, (struct membuf){.p = &fp,
                                                .left = sizeof(fp)});
                return copy_to_user(buf, &fp, sizeof(fp)) ? -EFAULT : 0;
        }

        if (!access_ok(buf, size))
                return -EACCES;
retry:
        /*
         * Load the FPU registers if they are not valid for the current task.
         * With a valid FPU state we can attempt to save the state directly to
         * userland's stack frame which will likely succeed. If it does not,
         * resolve the fault in the user memory and try again.
         */
        fpregs_lock();
        if (test_thread_flag(TIF_NEED_FPU_LOAD))
                fpregs_restore_userregs();

        pagefault_disable();
        ret = copy_fpregs_to_sigframe(buf_fx);
        pagefault_enable();
        fpregs_unlock();

        if (ret) {
                if (!fault_in_pages_writeable(buf_fx, fpu_user_xstate_size))
                        goto retry;
                return -EFAULT;
        }

        /* Save the fsave header for the 32-bit frames. */
        if ((ia32_fxstate || !use_fxsr()) && save_fsave_header(tsk, buf))
                return -1;

        if (use_fxsr() && save_xstate_epilog(buf_fx, ia32_fxstate))
                return -1;

        return 0;
}

static int __restore_fpregs_from_user(void __user *buf, u64 xrestore,
                                      bool fx_only)
{
        if (use_xsave()) {
                u64 init_bv = xfeatures_mask_uabi() & ~xrestore;
                int ret;

                if (likely(!fx_only))
                        ret = xrstor_from_user_sigframe(buf, xrestore);
                else
                        ret = fxrstor_from_user_sigframe(buf);

                if (!ret && unlikely(init_bv))
                        os_xrstor(&init_fpstate.xsave, init_bv);
                return ret;
        } else if (use_fxsr()) {
                return fxrstor_from_user_sigframe(buf);
        } else {
                return frstor_from_user_sigframe(buf);
        }
}

/*
 * Attempt to restore the FPU registers directly from user memory.
 * Pagefaults are handled and any errors returned are fatal.
 */
static int restore_fpregs_from_user(void __user *buf, u64 xrestore,
                                    bool fx_only, unsigned int size)
{
        struct fpu *fpu = &current->thread.fpu;
        int ret;

retry:
        fpregs_lock();
        pagefault_disable();
        ret = __restore_fpregs_from_user(buf, xrestore, fx_only);
        pagefault_enable();

        if (unlikely(ret)) {
                /*
                 * The above did an FPU restore operation, restricted to
                 * the user portion of the registers, and failed, but the
                 * microcode might have modified the FPU registers
                 * nevertheless.
                 *
                 * If the FPU registers do not belong to current, then
                 * invalidate the FPU register state otherwise the task
                 * might preempt current and return to user space with
                 * corrupted FPU registers.
                 */
                if (test_thread_flag(TIF_NEED_FPU_LOAD))
                        __cpu_invalidate_fpregs_state();
                fpregs_unlock();

                /* Try to handle #PF, but anything else is fatal. */
                if (ret != -EFAULT)
                        return -EINVAL;

                ret = fault_in_pages_readable(buf, size);
                if (!ret)
                        goto retry;
                return ret;
        }

        /*
         * Restore supervisor states: previous context switch etc has done
         * XSAVES and saved the supervisor states in the kernel buffer from
         * which they can be restored now.
         *
         * It would be optimal to handle this with a single XRSTORS, but
         * this does not work because the rest of the FPU registers have
         * been restored from a user buffer directly.
         */
        if (test_thread_flag(TIF_NEED_FPU_LOAD) && xfeatures_mask_supervisor())
                os_xrstor(&fpu->state.xsave, xfeatures_mask_supervisor());

        fpregs_mark_activate();
        fpregs_unlock();
        return 0;
}

static int __fpu_restore_sig(void __user *buf, void __user *buf_fx,
                             bool ia32_fxstate)
{
        int state_size = fpu_kernel_xstate_size;
        struct task_struct *tsk = current;
        struct fpu *fpu = &tsk->thread.fpu;
        struct user_i387_ia32_struct env;
        u64 user_xfeatures = 0;
        bool fx_only = false;
        int ret;

        if (use_xsave()) {
                struct _fpx_sw_bytes fx_sw_user;

                ret = check_xstate_in_sigframe(buf_fx, &fx_sw_user);
                if (unlikely(ret))
                        return ret;

                fx_only = !fx_sw_user.magic1;
                state_size = fx_sw_user.xstate_size;
                user_xfeatures = fx_sw_user.xfeatures;
        } else {
                user_xfeatures = XFEATURE_MASK_FPSSE;
        }

        if (likely(!ia32_fxstate)) {
                /*
                 * Attempt to restore the FPU registers directly from user
                 * memory. For that to succeed, the user access cannot cause page
                 * faults. If it does, fall back to the slow path below, going
                 * through the kernel buffer with the enabled pagefault handler.
                 */
                return restore_fpregs_from_user(buf_fx, user_xfeatures, fx_only,
                                                state_size);
        }

        /*
         * Copy the legacy state because the FP portion of the FX frame has
         * to be ignored for histerical raisins. The legacy state is folded
         * in once the larger state has been copied.
         */
        ret = __copy_from_user(&env, buf, sizeof(env));
        if (ret)
                return ret;

        /*
         * By setting TIF_NEED_FPU_LOAD it is ensured that our xstate is
         * not modified on context switch and that the xstate is considered
         * to be loaded again on return to userland (overriding last_cpu avoids
         * the optimisation).
         */
        fpregs_lock();
        if (!test_thread_flag(TIF_NEED_FPU_LOAD)) {
                /*
                 * If supervisor states are available then save the
                 * hardware state in current's fpstate so that the
                 * supervisor state is preserved. Save the full state for
                 * simplicity. There is no point in optimizing this by only
                 * saving the supervisor states and then shuffle them to
                 * the right place in memory. It's ia32 mode. Shrug.
                 */
                if (xfeatures_mask_supervisor())
                        os_xsave(&fpu->state.xsave);
                set_thread_flag(TIF_NEED_FPU_LOAD);
        }
        __fpu_invalidate_fpregs_state(fpu);
        __cpu_invalidate_fpregs_state();
        fpregs_unlock();

        if (use_xsave() && !fx_only) {
                ret = copy_sigframe_from_user_to_xstate(&fpu->state.xsave, buf_fx);
                if (ret)
                        return ret;
        } else {
                if (__copy_from_user(&fpu->state.fxsave, buf_fx,
                                     sizeof(fpu->state.fxsave)))
                        return -EFAULT;

                if (IS_ENABLED(CONFIG_X86_64)) {
                        /* Reject invalid MXCSR values. */
                        if (fpu->state.fxsave.mxcsr & ~mxcsr_feature_mask)
                                return -EINVAL;
                } else {
                        /* Mask invalid bits out for historical reasons (broken hardware). */
                        fpu->state.fxsave.mxcsr &= mxcsr_feature_mask;
                }

                /* Enforce XFEATURE_MASK_FPSSE when XSAVE is enabled */
                if (use_xsave())
                        fpu->state.xsave.header.xfeatures |= XFEATURE_MASK_FPSSE;
        }

        /* Fold the legacy FP storage */
        convert_to_fxsr(&fpu->state.fxsave, &env);

        fpregs_lock();
        if (use_xsave()) {
                /*
                 * Remove all UABI feature bits not set in user_xfeatures
                 * from the memory xstate header which makes the full
                 * restore below bring them into init state. This works for
                 * fx_only mode as well because that has only FP and SSE
                 * set in user_xfeatures.
                 *
                 * Preserve supervisor states!
                 */
                u64 mask = user_xfeatures | xfeatures_mask_supervisor();

                fpu->state.xsave.header.xfeatures &= mask;
                ret = os_xrstor_safe(&fpu->state.xsave, xfeatures_mask_all);
        } else {
                ret = fxrstor_safe(&fpu->state.fxsave);
        }

        if (likely(!ret))
                fpregs_mark_activate();

        fpregs_unlock();
        return ret;
}
static inline int xstate_sigframe_size(void)
{
        return use_xsave() ? fpu_user_xstate_size + FP_XSTATE_MAGIC2_SIZE :
                        fpu_user_xstate_size;
}

/*
 * Restore FPU state from a sigframe:
 */
int fpu__restore_sig(void __user *buf, int ia32_frame)
{
        unsigned int size = xstate_sigframe_size();
        struct fpu *fpu = &current->thread.fpu;
        void __user *buf_fx = buf;
        bool ia32_fxstate = false;
        int ret;

        if (unlikely(!buf)) {
                fpu__clear_user_states(fpu);
                return 0;
        }

        ia32_frame &= (IS_ENABLED(CONFIG_X86_32) ||
                       IS_ENABLED(CONFIG_IA32_EMULATION));

        /*
         * Only FXSR enabled systems need the FX state quirk.
         * FRSTOR does not need it and can use the fast path.
         */
        if (ia32_frame && use_fxsr()) {
                buf_fx = buf + sizeof(struct fregs_state);
                size += sizeof(struct fregs_state);
                ia32_fxstate = true;
        }

        if (!access_ok(buf, size)) {
                ret = -EACCES;
                goto out;
        }

        if (!IS_ENABLED(CONFIG_X86_64) && !cpu_feature_enabled(X86_FEATURE_FPU)) {
                ret = fpregs_soft_set(current, NULL, 0,
                                      sizeof(struct user_i387_ia32_struct),
                                      NULL, buf);
        } else {
                ret = __fpu_restore_sig(buf, buf_fx, ia32_fxstate);
        }

out:
        if (unlikely(ret))
                fpu__clear_user_states(fpu);
        return ret;
}

unsigned long
fpu__alloc_mathframe(unsigned long sp, int ia32_frame,
                     unsigned long *buf_fx, unsigned long *size)
{
        unsigned long frame_size = xstate_sigframe_size();

        *buf_fx = sp = round_down(sp - frame_size, 64);
        if (ia32_frame && use_fxsr()) {
                frame_size += sizeof(struct fregs_state);
                sp -= sizeof(struct fregs_state);
        }

        *size = frame_size;

        return sp;
}

unsigned long fpu__get_fpstate_size(void)
{
        unsigned long ret = xstate_sigframe_size();

        /*
         * This space is needed on (most) 32-bit kernels, or when a 32-bit
         * app is running on a 64-bit kernel. To keep things simple, just
         * assume the worst case and always include space for 'freg_state',
         * even for 64-bit apps on 64-bit kernels. This wastes a bit of
         * space, but keeps the code simple.
         */
        if ((IS_ENABLED(CONFIG_IA32_EMULATION) ||
             IS_ENABLED(CONFIG_X86_32)) && use_fxsr())
                ret += sizeof(struct fregs_state);

        return ret;
}

/*
 * Prepare the SW reserved portion of the fxsave memory layout, indicating
 * the presence of the extended state information in the memory layout
 * pointed by the fpstate pointer in the sigcontext.
 * This will be saved when ever the FP and extended state context is
 * saved on the user stack during the signal handler delivery to the user.
 */
void fpu__init_prepare_fx_sw_frame(void)
{
        int size = fpu_user_xstate_size + FP_XSTATE_MAGIC2_SIZE;

        fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1;
        fx_sw_reserved.extended_size = size;
        fx_sw_reserved.xfeatures = xfeatures_mask_uabi();
        fx_sw_reserved.xstate_size = fpu_user_xstate_size;

        if (IS_ENABLED(CONFIG_IA32_EMULATION) ||
            IS_ENABLED(CONFIG_X86_32)) {
                int fsave_header_size = sizeof(struct fregs_state);

                fx_sw_reserved_ia32 = fx_sw_reserved;
                fx_sw_reserved_ia32.extended_size = size + fsave_header_size;
        }
}