Capitalize subject, like other patches in this series and previous drivers/pci history.
On Wed, Oct 07, 2020 at 06:44:23PM +0200, Daniel Vetter wrote:
Since 3234ac664a87 ("/dev/mem: Revoke mappings when a driver claims the region") /dev/kmem zaps ptes when the kernel requests exclusive acccess to an iomem region. And with CONFIG_IO_STRICT_DEVMEM, this is the default for all driver uses.
Except there's two more ways to access pci bars: sysfs and proc mmap support. Let's plug that hole.
s/pci/PCI/ in commit logs and comments.
For revoke_devmem() to work we need to link our vma into the same address_space, with consistent vma->vm_pgoff. ->pgoff is already adjusted, because that's how (io_)remap_pfn_range works, but for the mapping we need to adjust vma->vm_file->f_mapping. Usually that's done at ->open time, but that's a bit tricky here with all the entry points and arch code. So instead create a fake file and adjust vma->vm_file.
Note this only works for ARCH_GENERIC_PCI_MMAP_RESOURCE. But that seems to be a subset of architectures support STRICT_DEVMEM, so we should be good.
The only difference in access checks left is that sysfs pci mmap does not check for CAP_RAWIO. But I think that makes some sense compared to /dev/mem and proc, where one file gives you access to everything and no ownership applies.
--- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -810,6 +810,7 @@ static loff_t memory_lseek(struct file *file, loff_t offset, int orig) }
static struct inode *devmem_inode; +static struct vfsmount *devmem_vfs_mount;
#ifdef CONFIG_IO_STRICT_DEVMEM void revoke_devmem(struct resource *res) @@ -843,6 +844,20 @@ void revoke_devmem(struct resource *res)
unmap_mapping_range(inode->i_mapping, res->start, resource_size(res), 1); }
+struct file *devmem_getfile(void) +{
- struct file *file;
- file = alloc_file_pseudo(devmem_inode, devmem_vfs_mount, "devmem",
O_RDWR, &kmem_fops);- if (IS_ERR(file))
return NULL;- file->f_mapping = devmem_indoe->i_mapping;
"devmem_indoe"? Obviously not compiled, I guess?
--- a/include/linux/ioport.h +++ b/include/linux/ioport.h @@ -304,8 +304,10 @@ struct resource *request_free_mem_region(struct resource *base,
#ifdef CONFIG_IO_STRICT_DEVMEM void revoke_devmem(struct resource *res); +struct file *devm_getfile(void); #else static inline void revoke_devmem(struct resource *res) { }; +static inline struct file *devmem_getfile(void) { return NULL; };
I guess these names are supposed to match?
#endif
#endif /* __ASSEMBLY__ */
2.28.0