// 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();
}