// SPDX-License-Identifier: GPL-2.0
/*
 * For architectures where we want to allow direct access to the PCI config
 * stuff - it would probably be preferable on PCs too, but there people
 * just do it by hand with the magic northbridge registers.
 */

#include <linux/errno.h>
#include <linux/pci.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/uaccess.h>
#include "pci.h"

SYSCALL_DEFINE5(pciconfig_read, unsigned long, bus, unsigned long, dfn,
                unsigned long, off, unsigned long, len, void __user *, buf)
{
        struct pci_dev *dev;
        u8 byte;
        u16 word;
        u32 dword;
        int err, cfg_ret;

        err = -EPERM;
        dev = NULL;
        if (!capable(CAP_SYS_ADMIN))
                goto error;

        err = -ENODEV;
        dev = pci_get_domain_bus_and_slot(0, bus, dfn);
        if (!dev)
                goto error;

        switch (len) {
        case 1:
                cfg_ret = pci_user_read_config_byte(dev, off, &byte);
                break;
        case 2:
                cfg_ret = pci_user_read_config_word(dev, off, &word);
                break;
        case 4:
                cfg_ret = pci_user_read_config_dword(dev, off, &dword);
                break;
        default:
                err = -EINVAL;
                goto error;
        }

        err = -EIO;
        if (cfg_ret)
                goto error;

        switch (len) {
        case 1:
                err = put_user(byte, (u8 __user *)buf);
                break;
        case 2:
                err = put_user(word, (u16 __user *)buf);
                break;
        case 4:
                err = put_user(dword, (u32 __user *)buf);
                break;
        }
        pci_dev_put(dev);
        return err;

error:
        /* ??? XFree86 doesn't even check the return value.  They
           just look for 0xffffffff in the output, since that's what
           they get instead of a machine check on x86.  */
        switch (len) {
        case 1:
                put_user(-1, (u8 __user *)buf);
                break;
        case 2:
                put_user(-1, (u16 __user *)buf);
                break;
        case 4:
                put_user(-1, (u32 __user *)buf);
                break;
        }
        pci_dev_put(dev);
        return err;
}

SYSCALL_DEFINE5(pciconfig_write, unsigned long, bus, unsigned long, dfn,
                unsigned long, off, unsigned long, len, void __user *, buf)
{
        struct pci_dev *dev;
        u8 byte;
        u16 word;
        u32 dword;
        int err = 0;

        if (!capable(CAP_SYS_ADMIN) ||
            security_locked_down(LOCKDOWN_PCI_ACCESS))
                return -EPERM;

        dev = pci_get_domain_bus_and_slot(0, bus, dfn);
        if (!dev)
                return -ENODEV;

        switch (len) {
        case 1:
                err = get_user(byte, (u8 __user *)buf);
                if (err)
                        break;
                err = pci_user_write_config_byte(dev, off, byte);
                if (err)
                        err = -EIO;
                break;

        case 2:
                err = get_user(word, (u16 __user *)buf);
                if (err)
                        break;
                err = pci_user_write_config_word(dev, off, word);
                if (err)
                        err = -EIO;
                break;

        case 4:
                err = get_user(dword, (u32 __user *)buf);
                if (err)
                        break;
                err = pci_user_write_config_dword(dev, off, dword);
                if (err)
                        err = -EIO;
                break;

        default:
                err = -EINVAL;
                break;
        }
        pci_dev_put(dev);
        return err;
}