// SPDX-License-Identifier: GPL-2.0
/*
 * PCI Backend - Functions for creating a virtual configuration space for
 *               exported PCI Devices.
 *               It's dangerous to allow PCI Driver Domains to change their
 *               device's resources (memory, i/o ports, interrupts). We need to
 *               restrict changes to certain PCI Configuration registers:
 *               BARs, INTERRUPT_PIN, most registers in the header...
 *
 * Author: Ryan Wilson <hap9@epoch.ncsc.mil>
 */

#include <linux/kernel.h>
#include <linux/moduleparam.h>
#include <linux/pci.h>
#include "pciback.h"
#include "conf_space.h"
#include "conf_space_quirks.h"

bool xen_pcibk_permissive;
module_param_named(permissive, xen_pcibk_permissive, bool, 0644);

/* This is where xen_pcibk_read_config_byte, xen_pcibk_read_config_word,
 * xen_pcibk_write_config_word, and xen_pcibk_write_config_byte are created. */
#define DEFINE_PCI_CONFIG(op, size, type)                       \
int xen_pcibk_##op##_config_##size                              \
(struct pci_dev *dev, int offset, type value, void *data)       \
{                                                               \
        return pci_##op##_config_##size(dev, offset, value);    \
}

DEFINE_PCI_CONFIG(read, byte, u8 *)
DEFINE_PCI_CONFIG(read, word, u16 *)
DEFINE_PCI_CONFIG(read, dword, u32 *)

DEFINE_PCI_CONFIG(write, byte, u8)
DEFINE_PCI_CONFIG(write, word, u16)
DEFINE_PCI_CONFIG(write, dword, u32)

static int conf_space_read(struct pci_dev *dev,
                           const struct config_field_entry *entry,
                           int offset, u32 *value)
{
        int ret = 0;
        const struct config_field *field = entry->field;

        *value = 0;

        switch (field->size) {
        case 1:
                if (field->u.b.read)
                        ret = field->u.b.read(dev, offset, (u8 *) value,
                                              entry->data);
                break;
        case 2:
                if (field->u.w.read)
                        ret = field->u.w.read(dev, offset, (u16 *) value,
                                              entry->data);
                break;
        case 4:
                if (field->u.dw.read)
                        ret = field->u.dw.read(dev, offset, value, entry->data);
                break;
        }
        return ret;
}

static int conf_space_write(struct pci_dev *dev,
                            const struct config_field_entry *entry,
                            int offset, u32 value)
{
        int ret = 0;
        const struct config_field *field = entry->field;

        switch (field->size) {
        case 1:
                if (field->u.b.write)
                        ret = field->u.b.write(dev, offset, (u8) value,
                                               entry->data);
                break;
        case 2:
                if (field->u.w.write)
                        ret = field->u.w.write(dev, offset, (u16) value,
                                               entry->data);
                break;
        case 4:
                if (field->u.dw.write)
                        ret = field->u.dw.write(dev, offset, value,
                                                entry->data);
                break;
        }
        return ret;
}

static inline u32 get_mask(int size)
{
        if (size == 1)
                return 0xff;
        else if (size == 2)
                return 0xffff;
        else
                return 0xffffffff;
}

static inline int valid_request(int offset, int size)
{
        /* Validate request (no un-aligned requests) */
        if ((size == 1 || size == 2 || size == 4) && (offset % size) == 0)
                return 1;
        return 0;
}

static inline u32 merge_value(u32 val, u32 new_val, u32 new_val_mask,
                              int offset)
{
        if (offset >= 0) {
                new_val_mask <<= (offset * 8);
                new_val <<= (offset * 8);
        } else {
                new_val_mask >>= (offset * -8);
                new_val >>= (offset * -8);
        }
        val = (val & ~new_val_mask) | (new_val & new_val_mask);

        return val;
}

static int xen_pcibios_err_to_errno(int err)
{
        switch (err) {
        case PCIBIOS_SUCCESSFUL:
                return XEN_PCI_ERR_success;
        case PCIBIOS_DEVICE_NOT_FOUND:
                return XEN_PCI_ERR_dev_not_found;
        case PCIBIOS_BAD_REGISTER_NUMBER:
                return XEN_PCI_ERR_invalid_offset;
        case PCIBIOS_FUNC_NOT_SUPPORTED:
                return XEN_PCI_ERR_not_implemented;
        case PCIBIOS_SET_FAILED:
                return XEN_PCI_ERR_access_denied;
        }
        return err;
}

int xen_pcibk_config_read(struct pci_dev *dev, int offset, int size,
                          u32 *ret_val)
{
        int err = 0;
        struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);
        const struct config_field_entry *cfg_entry;
        const struct config_field *field;
        int field_start, field_end;
        /* if read fails for any reason, return 0
         * (as if device didn't respond) */
        u32 value = 0, tmp_val;

        if (unlikely(verbose_request))
                printk(KERN_DEBUG DRV_NAME ": %s: read %d bytes at 0x%x\n",
                       pci_name(dev), size, offset);

        if (!valid_request(offset, size)) {
                err = XEN_PCI_ERR_invalid_offset;
                goto out;
        }

        /* Get the real value first, then modify as appropriate */
        switch (size) {
        case 1:
                err = pci_read_config_byte(dev, offset, (u8 *) &value);
                break;
        case 2:
                err = pci_read_config_word(dev, offset, (u16 *) &value);
                break;
        case 4:
                err = pci_read_config_dword(dev, offset, &value);
                break;
        }

        list_for_each_entry(cfg_entry, &dev_data->config_fields, list) {
                field = cfg_entry->field;

                field_start = OFFSET(cfg_entry);
                field_end = OFFSET(cfg_entry) + field->size;

                if (offset + size > field_start && field_end > offset) {
                        err = conf_space_read(dev, cfg_entry, field_start,
                                              &tmp_val);
                        if (err)
                                goto out;

                        value = merge_value(value, tmp_val,
                                            get_mask(field->size),
                                            field_start - offset);
                }
        }

out:
        if (unlikely(verbose_request))
                printk(KERN_DEBUG DRV_NAME ": %s: read %d bytes at 0x%x = %x\n",
                       pci_name(dev), size, offset, value);

        *ret_val = value;
        return xen_pcibios_err_to_errno(err);
}

int xen_pcibk_config_write(struct pci_dev *dev, int offset, int size, u32 value)
{
        int err = 0, handled = 0;
        struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);
        const struct config_field_entry *cfg_entry;
        const struct config_field *field;
        u32 tmp_val;
        int field_start, field_end;

        if (unlikely(verbose_request))
                printk(KERN_DEBUG
                       DRV_NAME ": %s: write request %d bytes at 0x%x = %x\n",
                       pci_name(dev), size, offset, value);

        if (!valid_request(offset, size))
                return XEN_PCI_ERR_invalid_offset;

        list_for_each_entry(cfg_entry, &dev_data->config_fields, list) {
                field = cfg_entry->field;

                field_start = OFFSET(cfg_entry);
                field_end = OFFSET(cfg_entry) + field->size;

                if (offset + size > field_start && field_end > offset) {
                        err = conf_space_read(dev, cfg_entry, field_start,
                                              &tmp_val);
                        if (err)
                                break;

                        tmp_val = merge_value(tmp_val, value, get_mask(size),
                                              offset - field_start);

                        err = conf_space_write(dev, cfg_entry, field_start,
                                               tmp_val);

                        /* handled is set true here, but not every byte
                         * may have been written! Properly detecting if
                         * every byte is handled is unnecessary as the
                         * flag is used to detect devices that need
                         * special helpers to work correctly.
                         */
                        handled = 1;
                }
        }

        if (!handled && !err) {
                /* By default, anything not specificially handled above is
                 * read-only. The permissive flag changes this behavior so
                 * that anything not specifically handled above is writable.
                 * This means that some fields may still be read-only because
                 * they have entries in the config_field list that intercept
                 * the write and do nothing. */
                if (dev_data->permissive || xen_pcibk_permissive) {
                        switch (size) {
                        case 1:
                                err = pci_write_config_byte(dev, offset,
                                                            (u8) value);
                                break;
                        case 2:
                                err = pci_write_config_word(dev, offset,
                                                            (u16) value);
                                break;
                        case 4:
                                err = pci_write_config_dword(dev, offset,
                                                             (u32) value);
                                break;
                        }
                } else if (!dev_data->warned_on_write) {
                        dev_data->warned_on_write = 1;
                        dev_warn(&dev->dev, "Driver tried to write to a "
                                 "read-only configuration space field at offset"
                                 " 0x%x, size %d. This may be harmless, but if "
                                 "you have problems with your device:\n"
                                 "1) see permissive attribute in sysfs\n"
                                 "2) report problems to the xen-devel "
                                 "mailing list along with details of your "
                                 "device obtained from lspci.\n", offset, size);
                }
        }

        return xen_pcibios_err_to_errno(err);
}

void xen_pcibk_config_free_dyn_fields(struct pci_dev *dev)
{
        struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);
        struct config_field_entry *cfg_entry, *t;
        const struct config_field *field;

        dev_dbg(&dev->dev, "free-ing dynamically allocated virtual "
                           "configuration space fields\n");
        if (!dev_data)
                return;

        list_for_each_entry_safe(cfg_entry, t, &dev_data->config_fields, list) {
                field = cfg_entry->field;

                if (field->clean) {
                        field->clean((struct config_field *)field);

                        kfree(cfg_entry->data);

                        list_del(&cfg_entry->list);
                        kfree(cfg_entry);
                }

        }
}

void xen_pcibk_config_reset_dev(struct pci_dev *dev)
{
        struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);
        const struct config_field_entry *cfg_entry;
        const struct config_field *field;

        dev_dbg(&dev->dev, "resetting virtual configuration space\n");
        if (!dev_data)
                return;

        list_for_each_entry(cfg_entry, &dev_data->config_fields, list) {
                field = cfg_entry->field;

                if (field->reset)
                        field->reset(dev, OFFSET(cfg_entry), cfg_entry->data);
        }
}

void xen_pcibk_config_free_dev(struct pci_dev *dev)
{
        struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);
        struct config_field_entry *cfg_entry, *t;
        const struct config_field *field;

        dev_dbg(&dev->dev, "free-ing virtual configuration space fields\n");
        if (!dev_data)
                return;

        list_for_each_entry_safe(cfg_entry, t, &dev_data->config_fields, list) {
                list_del(&cfg_entry->list);

                field = cfg_entry->field;

                if (field->release)
                        field->release(dev, OFFSET(cfg_entry), cfg_entry->data);

                kfree(cfg_entry);
        }
}

int xen_pcibk_config_add_field_offset(struct pci_dev *dev,
                                    const struct config_field *field,
                                    unsigned int base_offset)
{
        int err = 0;
        struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);
        struct config_field_entry *cfg_entry;
        void *tmp;

        cfg_entry = kmalloc(sizeof(*cfg_entry), GFP_KERNEL);
        if (!cfg_entry) {
                err = -ENOMEM;
                goto out;
        }

        cfg_entry->data = NULL;
        cfg_entry->field = field;
        cfg_entry->base_offset = base_offset;

        /* silently ignore duplicate fields */
        err = xen_pcibk_field_is_dup(dev, OFFSET(cfg_entry));
        if (err)
                goto out;

        if (field->init) {
                tmp = field->init(dev, OFFSET(cfg_entry));

                if (IS_ERR(tmp)) {
                        err = PTR_ERR(tmp);
                        goto out;
                }

                cfg_entry->data = tmp;
        }

        dev_dbg(&dev->dev, "added config field at offset 0x%02x\n",
                OFFSET(cfg_entry));
        list_add_tail(&cfg_entry->list, &dev_data->config_fields);

out:
        if (err)
                kfree(cfg_entry);

        return err;
}

/* This sets up the device's virtual configuration space to keep track of
 * certain registers (like the base address registers (BARs) so that we can
 * keep the client from manipulating them directly.
 */
int xen_pcibk_config_init_dev(struct pci_dev *dev)
{
        int err = 0;
        struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);

        dev_dbg(&dev->dev, "initializing virtual configuration space\n");

        INIT_LIST_HEAD(&dev_data->config_fields);

        err = xen_pcibk_config_header_add_fields(dev);
        if (err)
                goto out;

        err = xen_pcibk_config_capability_add_fields(dev);
        if (err)
                goto out;

        err = xen_pcibk_config_quirks_init(dev);

out:
        return err;
}

int xen_pcibk_config_init(void)
{
        return xen_pcibk_config_capability_init();
}