// SPDX-License-Identifier: GPL-2.0-only
#include <linux/export.h>
#include <linux/slab.h>
#include <linux/regset.h>

static int __regset_get(struct task_struct *target,
                        const struct user_regset *regset,
                        unsigned int size,
                        void **data)
{
        void *p = *data, *to_free = NULL;
        int res;

        if (!regset->regset_get)
                return -EOPNOTSUPP;
        if (size > regset->n * regset->size)
                size = regset->n * regset->size;
        if (!p) {
                to_free = p = kvzalloc(size, GFP_KERNEL);
                if (!p)
                        return -ENOMEM;
        }
        res = regset->regset_get(target, regset,
                           (struct membuf){.p = p, .left = size});
        if (res < 0) {
                kvfree(to_free);
                return res;
        }
        *data = p;
        return size - res;
}

int regset_get(struct task_struct *target,
               const struct user_regset *regset,
               unsigned int size,
               void *data)
{
        return __regset_get(target, regset, size, &data);
}
EXPORT_SYMBOL(regset_get);

int regset_get_alloc(struct task_struct *target,
                     const struct user_regset *regset,
                     unsigned int size,
                     void **data)
{
        *data = NULL;
        return __regset_get(target, regset, size, data);
}
EXPORT_SYMBOL(regset_get_alloc);

/**
 * copy_regset_to_user - fetch a thread's user_regset data into user memory
 * @target:     thread to be examined
 * @view:       &struct user_regset_view describing user thread machine state
 * @setno:      index in @view->regsets
 * @offset:     offset into the regset data, in bytes
 * @size:       amount of data to copy, in bytes
 * @data:       user-mode pointer to copy into
 */
int copy_regset_to_user(struct task_struct *target,
                        const struct user_regset_view *view,
                        unsigned int setno,
                        unsigned int offset, unsigned int size,
                        void __user *data)
{
        const struct user_regset *regset = &view->regsets[setno];
        void *buf;
        int ret;

        ret = regset_get_alloc(target, regset, size, &buf);
        if (ret > 0)
                ret = copy_to_user(data, buf, ret) ? -EFAULT : 0;
        kvfree(buf);
        return ret;
}