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// SPDX-License-Identifier: GPL-2.0
#include <linux/export.h>
#include <linux/fb.h>
#include <linux/module.h>
#include <linux/uaccess.h>
ssize_t fb_io_read(struct fb_info *info, char __user *buf, size_t count, loff_t *ppos)
{
unsigned long p = *ppos;
u8 *buffer, *dst;
u8 __iomem *src;
int c, cnt = 0, err = 0;
unsigned long total_size, trailing;
if (info->flags & FBINFO_VIRTFB)
fb_warn_once(info, "Framebuffer is not in I/O address space.");
if (!info->screen_base)
return -ENODEV;
total_size = info->screen_size;
if (total_size == 0)
total_size = info->fix.smem_len;
/*
* Security Hardening: Defend against buggy legacy drivers that may
* calculate a malformed screen_size. Clamp total_size to the actual
* hardware mapped memory limit (smem_len) to prevent OOB access.
*/
if (info->fix.smem_len && total_size > info->fix.smem_len)
total_size = info->fix.smem_len;
if (p >= total_size)
return 0;
if (count >= total_size)
count = total_size;
if (count + p > total_size)
count = total_size - p;
buffer = kmalloc((count > PAGE_SIZE) ? PAGE_SIZE : count,
GFP_KERNEL);
if (!buffer)
return -ENOMEM;
src = (u8 __iomem *) (info->screen_base + p);
if (info->fbops->fb_sync)
info->fbops->fb_sync(info);
while (count) {
c = (count > PAGE_SIZE) ? PAGE_SIZE : count;
dst = buffer;
fb_memcpy_fromio(dst, src, c);
dst += c;
src += c;
trailing = copy_to_user(buf, buffer, c);
if (trailing == c) {
err = -EFAULT;
break;
}
c -= trailing;
*ppos += c;
buf += c;
cnt += c;
count -= c;
/*
* If there was a partial copy, the user buffer is faulty.
* Break out to avoid over-advancing the src pointer and
* reading out of bounds in the next iteration.
*/
if (trailing)
break;
}
kfree(buffer);
return cnt ? cnt : err;
}
EXPORT_SYMBOL(fb_io_read);
ssize_t fb_io_write(struct fb_info *info, const char __user *buf, size_t count, loff_t *ppos)
{
unsigned long p = *ppos;
u8 *buffer, *src;
u8 __iomem *dst;
int c, cnt = 0, err = 0;
unsigned long total_size, trailing;
if (info->flags & FBINFO_VIRTFB)
fb_warn_once(info, "Framebuffer is not in I/O address space.");
if (!info->screen_base)
return -ENODEV;
total_size = info->screen_size;
if (total_size == 0)
total_size = info->fix.smem_len;
/*
* Security Hardening: Defend against buggy legacy drivers that may
* calculate a malformed screen_size. Clamp total_size to the actual
* hardware mapped memory limit (smem_len) to prevent OOB access.
*/
if (info->fix.smem_len && total_size > info->fix.smem_len)
total_size = info->fix.smem_len;
if (p > total_size)
return -EFBIG;
if (count > total_size) {
err = -EFBIG;
count = total_size;
}
if (count + p > total_size) {
if (!err)
err = -ENOSPC;
count = total_size - p;
}
buffer = kmalloc((count > PAGE_SIZE) ? PAGE_SIZE : count,
GFP_KERNEL);
if (!buffer)
return -ENOMEM;
dst = (u8 __iomem *) (info->screen_base + p);
if (info->fbops->fb_sync)
info->fbops->fb_sync(info);
while (count) {
c = (count > PAGE_SIZE) ? PAGE_SIZE : count;
src = buffer;
trailing = copy_from_user(src, buf, c);
if (trailing == c) {
err = -EFAULT;
break;
}
c -= trailing;
fb_memcpy_toio(dst, src, c);
dst += c;
src += c;
*ppos += c;
buf += c;
cnt += c;
count -= c;
}
kfree(buffer);
return (cnt) ? cnt : err;
}
EXPORT_SYMBOL(fb_io_write);
int fb_io_mmap(struct fb_info *info, struct vm_area_struct *vma)
{
unsigned long start = info->fix.smem_start;
u32 len = info->fix.smem_len;
unsigned long mmio_pgoff = PAGE_ALIGN((start & ~PAGE_MASK) + len) >> PAGE_SHIFT;
if (info->flags & FBINFO_VIRTFB)
fb_warn_once(info, "Framebuffer is not in I/O address space.");
/*
* This can be either the framebuffer mapping, or if pgoff points
* past it, the mmio mapping.
*/
if (vma->vm_pgoff >= mmio_pgoff) {
if (info->var.accel_flags)
return -EINVAL;
vma->vm_pgoff -= mmio_pgoff;
start = info->fix.mmio_start;
len = info->fix.mmio_len;
}
vma->vm_page_prot = vma_get_page_prot(vma);
vma->vm_page_prot = pgprot_framebuffer(vma->vm_page_prot, vma->vm_start,
vma->vm_end, start);
return vm_iomap_memory(vma, start, len);
}
EXPORT_SYMBOL(fb_io_mmap);
MODULE_DESCRIPTION("Fbdev helpers for framebuffers in I/O memory");
MODULE_LICENSE("GPL");
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