We want all iomem mmaps to consistently revoke ptes when the kernel
takes over and CONFIG_IO_STRICT_DEVMEM is enabled. This includes the
pci bar mmaps available through procfs and sysfs, which currently do
not revoke mappings.
To prepare for this, move the code from the /dev/kmem driver to
kernel/resource.c.
Reviewed-by: Greg Kroah-Hartman <[email protected]>
Signed-off-by: Daniel Vetter <[email protected]>
Cc: Jason Gunthorpe <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: John Hubbard <[email protected]>
Cc: Jérôme Glisse <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: Arnd Bergmann <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Daniel Vetter <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Signed-off-by: Daniel Vetter <[email protected]>
--
v3:
- add barrier for consistency and document why we don't have to check
for NULL (Jason)
---
drivers/char/mem.c | 85 +---------------------------------
include/linux/ioport.h | 6 +--
kernel/resource.c | 101 ++++++++++++++++++++++++++++++++++++++++-
3 files changed, 102 insertions(+), 90 deletions(-)
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 5502f56f3655..53338aad8d28 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -31,9 +31,6 @@
#include <linux/uio.h>
#include <linux/uaccess.h>
#include <linux/security.h>
-#include <linux/pseudo_fs.h>
-#include <uapi/linux/magic.h>
-#include <linux/mount.h>
#ifdef CONFIG_IA64
# include <linux/efi.h>
@@ -809,42 +806,6 @@ static loff_t memory_lseek(struct file *file, loff_t offset, int orig)
return ret;
}
-static struct inode *devmem_inode;
-
-#ifdef CONFIG_IO_STRICT_DEVMEM
-void revoke_devmem(struct resource *res)
-{
- /* pairs with smp_store_release() in devmem_init_inode() */
- struct inode *inode = smp_load_acquire(&devmem_inode);
-
- /*
- * Check that the initialization has completed. Losing the race
- * is ok because it means drivers are claiming resources before
- * the fs_initcall level of init and prevent /dev/mem from
- * establishing mappings.
- */
- if (!inode)
- return;
-
- /*
- * The expectation is that the driver has successfully marked
- * the resource busy by this point, so devmem_is_allowed()
- * should start returning false, however for performance this
- * does not iterate the entire resource range.
- */
- if (devmem_is_allowed(PHYS_PFN(res->start)) &&
- devmem_is_allowed(PHYS_PFN(res->end))) {
- /*
- * *cringe* iomem=relaxed says "go ahead, what's the
- * worst that can happen?"
- */
- return;
- }
-
- unmap_mapping_range(inode->i_mapping, res->start, resource_size(res), 1);
-}
-#endif
-
static int open_port(struct inode *inode, struct file *filp)
{
int rc;
@@ -864,7 +825,7 @@ static int open_port(struct inode *inode, struct file *filp)
* revocations when drivers want to take over a /dev/mem mapped
* range.
*/
- filp->f_mapping = inode->i_mapping;
+ filp->f_mapping = iomem_get_mapping();
return 0;
}
@@ -995,48 +956,6 @@ static char *mem_devnode(struct device *dev, umode_t *mode)
static struct class *mem_class;
-static int devmem_fs_init_fs_context(struct fs_context *fc)
-{
- return init_pseudo(fc, DEVMEM_MAGIC) ? 0 : -ENOMEM;
-}
-
-static struct file_system_type devmem_fs_type = {
- .name = "devmem",
- .owner = THIS_MODULE,
- .init_fs_context = devmem_fs_init_fs_context,
- .kill_sb = kill_anon_super,
-};
-
-static int devmem_init_inode(void)
-{
- static struct vfsmount *devmem_vfs_mount;
- static int devmem_fs_cnt;
- struct inode *inode;
- int rc;
-
- rc = simple_pin_fs(&devmem_fs_type, &devmem_vfs_mount, &devmem_fs_cnt);
- if (rc < 0) {
- pr_err("Cannot mount /dev/mem pseudo filesystem: %d\n", rc);
- return rc;
- }
-
- inode = alloc_anon_inode(devmem_vfs_mount->mnt_sb);
- if (IS_ERR(inode)) {
- rc = PTR_ERR(inode);
- pr_err("Cannot allocate inode for /dev/mem: %d\n", rc);
- simple_release_fs(&devmem_vfs_mount, &devmem_fs_cnt);
- return rc;
- }
-
- /*
- * Publish /dev/mem initialized.
- * Pairs with smp_load_acquire() in revoke_devmem().
- */
- smp_store_release(&devmem_inode, inode);
-
- return 0;
-}
-
static int __init chr_dev_init(void)
{
int minor;
@@ -1058,8 +977,6 @@ static int __init chr_dev_init(void)
*/
if ((minor == DEVPORT_MINOR) && !arch_has_dev_port())
continue;
- if ((minor == DEVMEM_MINOR) && devmem_init_inode() != 0)
- continue;
device_create(mem_class, NULL, MKDEV(MEM_MAJOR, minor),
NULL, devlist[minor].name);
diff --git a/include/linux/ioport.h b/include/linux/ioport.h
index 6c2b06fe8beb..8ffb61b36606 100644
--- a/include/linux/ioport.h
+++ b/include/linux/ioport.h
@@ -302,11 +302,7 @@ struct resource *devm_request_free_mem_region(struct device *dev,
struct resource *request_free_mem_region(struct resource *base,
unsigned long size, const char *name);
-#ifdef CONFIG_IO_STRICT_DEVMEM
-void revoke_devmem(struct resource *res);
-#else
-static inline void revoke_devmem(struct resource *res) { };
-#endif
+extern struct address_space *iomem_get_mapping(void);
#endif /* __ASSEMBLY__ */
#endif /* _LINUX_IOPORT_H */
diff --git a/kernel/resource.c b/kernel/resource.c
index 841737bbda9e..a92fed5b9997 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -18,12 +18,15 @@
#include <linux/spinlock.h>
#include <linux/fs.h>
#include <linux/proc_fs.h>
+#include <linux/pseudo_fs.h>
#include <linux/sched.h>
#include <linux/seq_file.h>
#include <linux/device.h>
#include <linux/pfn.h>
#include <linux/mm.h>
+#include <linux/mount.h>
#include <linux/resource_ext.h>
+#include <uapi/linux/magic.h>
#include <asm/io.h>
@@ -1112,6 +1115,58 @@ resource_size_t resource_alignment(struct resource *res)
static DECLARE_WAIT_QUEUE_HEAD(muxed_resource_wait);
+static struct inode *iomem_inode;
+
+#ifdef CONFIG_IO_STRICT_DEVMEM
+static void revoke_iomem(struct resource *res)
+{
+ /* pairs with smp_store_release() in iomem_init_inode() */
+ struct inode *inode = smp_load_acquire(&iomem_inode);
+
+ /*
+ * Check that the initialization has completed. Losing the race
+ * is ok because it means drivers are claiming resources before
+ * the fs_initcall level of init and prevent /dev/mem from
+ * establishing mappings.
+ */
+ if (!inode)
+ return;
+
+ /*
+ * The expectation is that the driver has successfully marked
+ * the resource busy by this point, so devmem_is_allowed()
+ * should start returning false, however for performance this
+ * does not iterate the entire resource range.
+ */
+ if (devmem_is_allowed(PHYS_PFN(res->start)) &&
+ devmem_is_allowed(PHYS_PFN(res->end))) {
+ /*
+ * *cringe* iomem=relaxed says "go ahead, what's the
+ * worst that can happen?"
+ */
+ return;
+ }
+
+ unmap_mapping_range(inode->i_mapping, res->start, resource_size(res), 1);
+}
+struct address_space *iomem_get_mapping(void)
+{
+ /*
+ * This function is only called from file open paths, hence guaranteed
+ * that fs_initcalls have completed and no need to check for NULL. But
+ * since revoke_iomem can be called before the initcall we still need
+ * the barrier to appease checkers.
+ */
+ return smp_load_acquire(&iomem_inode)->i_mapping;
+}
+#else
+static void revoke_iomem(struct resource *res) {}
+struct address_space *iomem_get_mapping(void)
+{
+ return NULL;
+}
+#endif
+
/**
* __request_region - create a new busy resource region
* @parent: parent resource descriptor
@@ -1179,7 +1234,7 @@ struct resource * __request_region(struct resource *parent,
write_unlock(&resource_lock);
if (res && orig_parent == &iomem_resource)
- revoke_devmem(res);
+ revoke_iomem(res);
return res;
}
@@ -1713,4 +1768,48 @@ static int __init strict_iomem(char *str)
return 1;
}
+static int iomem_fs_init_fs_context(struct fs_context *fc)
+{
+ return init_pseudo(fc, DEVMEM_MAGIC) ? 0 : -ENOMEM;
+}
+
+static struct file_system_type iomem_fs_type = {
+ .name = "iomem",
+ .owner = THIS_MODULE,
+ .init_fs_context = iomem_fs_init_fs_context,
+ .kill_sb = kill_anon_super,
+};
+
+static int __init iomem_init_inode(void)
+{
+ static struct vfsmount *iomem_vfs_mount;
+ static int iomem_fs_cnt;
+ struct inode *inode;
+ int rc;
+
+ rc = simple_pin_fs(&iomem_fs_type, &iomem_vfs_mount, &iomem_fs_cnt);
+ if (rc < 0) {
+ pr_err("Cannot mount iomem pseudo filesystem: %d\n", rc);
+ return rc;
+ }
+
+ inode = alloc_anon_inode(iomem_vfs_mount->mnt_sb);
+ if (IS_ERR(inode)) {
+ rc = PTR_ERR(inode);
+ pr_err("Cannot allocate inode for iomem: %d\n", rc);
+ simple_release_fs(&iomem_vfs_mount, &iomem_fs_cnt);
+ return rc;
+ }
+
+ /*
+ * Publish /dev/mem initialized.
+ * Pairs with smp_load_acquire() in revoke_iomem().
+ */
+ smp_store_release(&iomem_inode, inode);
+
+ return 0;
+}
+
+fs_initcall(iomem_init_inode);
+
__setup("iomem=", strict_iomem);
--
2.28.0
On Wed, Oct 21, 2020 at 1:57 AM Daniel Vetter <[email protected]> wrote:
>
> We want all iomem mmaps to consistently revoke ptes when the kernel
> takes over and CONFIG_IO_STRICT_DEVMEM is enabled. This includes the
> pci bar mmaps available through procfs and sysfs, which currently do
> not revoke mappings.
>
> To prepare for this, move the code from the /dev/kmem driver to
> kernel/resource.c.
>
> Reviewed-by: Greg Kroah-Hartman <[email protected]>
> Signed-off-by: Daniel Vetter <[email protected]>
> Cc: Jason Gunthorpe <[email protected]>
> Cc: Kees Cook <[email protected]>
> Cc: Dan Williams <[email protected]>
> Cc: Andrew Morton <[email protected]>
> Cc: John Hubbard <[email protected]>
> Cc: Jérôme Glisse <[email protected]>
> Cc: Jan Kara <[email protected]>
> Cc: Dan Williams <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Cc: Arnd Bergmann <[email protected]>
> Cc: Greg Kroah-Hartman <[email protected]>
> Cc: Daniel Vetter <[email protected]>
> Cc: David Hildenbrand <[email protected]>
> Cc: "Rafael J. Wysocki" <[email protected]>
> Signed-off-by: Daniel Vetter <[email protected]>
> --
> v3:
> - add barrier for consistency and document why we don't have to check
> for NULL (Jason)
> ---
> drivers/char/mem.c | 85 +---------------------------------
> include/linux/ioport.h | 6 +--
> kernel/resource.c | 101 ++++++++++++++++++++++++++++++++++++++++-
> 3 files changed, 102 insertions(+), 90 deletions(-)
>
> diff --git a/drivers/char/mem.c b/drivers/char/mem.c
> index 5502f56f3655..53338aad8d28 100644
> --- a/drivers/char/mem.c
> +++ b/drivers/char/mem.c
> @@ -31,9 +31,6 @@
> #include <linux/uio.h>
> #include <linux/uaccess.h>
> #include <linux/security.h>
> -#include <linux/pseudo_fs.h>
> -#include <uapi/linux/magic.h>
> -#include <linux/mount.h>
>
> #ifdef CONFIG_IA64
> # include <linux/efi.h>
> @@ -809,42 +806,6 @@ static loff_t memory_lseek(struct file *file, loff_t offset, int orig)
> return ret;
> }
>
> -static struct inode *devmem_inode;
> -
> -#ifdef CONFIG_IO_STRICT_DEVMEM
> -void revoke_devmem(struct resource *res)
> -{
> - /* pairs with smp_store_release() in devmem_init_inode() */
> - struct inode *inode = smp_load_acquire(&devmem_inode);
> -
> - /*
> - * Check that the initialization has completed. Losing the race
> - * is ok because it means drivers are claiming resources before
> - * the fs_initcall level of init and prevent /dev/mem from
> - * establishing mappings.
> - */
> - if (!inode)
> - return;
> -
> - /*
> - * The expectation is that the driver has successfully marked
> - * the resource busy by this point, so devmem_is_allowed()
> - * should start returning false, however for performance this
> - * does not iterate the entire resource range.
> - */
> - if (devmem_is_allowed(PHYS_PFN(res->start)) &&
> - devmem_is_allowed(PHYS_PFN(res->end))) {
> - /*
> - * *cringe* iomem=relaxed says "go ahead, what's the
> - * worst that can happen?"
> - */
> - return;
> - }
> -
> - unmap_mapping_range(inode->i_mapping, res->start, resource_size(res), 1);
> -}
> -#endif
> -
> static int open_port(struct inode *inode, struct file *filp)
> {
> int rc;
> @@ -864,7 +825,7 @@ static int open_port(struct inode *inode, struct file *filp)
> * revocations when drivers want to take over a /dev/mem mapped
> * range.
> */
> - filp->f_mapping = inode->i_mapping;
> + filp->f_mapping = iomem_get_mapping();
>
> return 0;
> }
> @@ -995,48 +956,6 @@ static char *mem_devnode(struct device *dev, umode_t *mode)
>
> static struct class *mem_class;
>
> -static int devmem_fs_init_fs_context(struct fs_context *fc)
> -{
> - return init_pseudo(fc, DEVMEM_MAGIC) ? 0 : -ENOMEM;
> -}
> -
> -static struct file_system_type devmem_fs_type = {
> - .name = "devmem",
> - .owner = THIS_MODULE,
> - .init_fs_context = devmem_fs_init_fs_context,
> - .kill_sb = kill_anon_super,
> -};
> -
> -static int devmem_init_inode(void)
> -{
> - static struct vfsmount *devmem_vfs_mount;
> - static int devmem_fs_cnt;
> - struct inode *inode;
> - int rc;
> -
> - rc = simple_pin_fs(&devmem_fs_type, &devmem_vfs_mount, &devmem_fs_cnt);
> - if (rc < 0) {
> - pr_err("Cannot mount /dev/mem pseudo filesystem: %d\n", rc);
> - return rc;
> - }
> -
> - inode = alloc_anon_inode(devmem_vfs_mount->mnt_sb);
> - if (IS_ERR(inode)) {
> - rc = PTR_ERR(inode);
> - pr_err("Cannot allocate inode for /dev/mem: %d\n", rc);
> - simple_release_fs(&devmem_vfs_mount, &devmem_fs_cnt);
> - return rc;
> - }
> -
> - /*
> - * Publish /dev/mem initialized.
> - * Pairs with smp_load_acquire() in revoke_devmem().
> - */
> - smp_store_release(&devmem_inode, inode);
> -
> - return 0;
> -}
> -
> static int __init chr_dev_init(void)
> {
> int minor;
> @@ -1058,8 +977,6 @@ static int __init chr_dev_init(void)
> */
> if ((minor == DEVPORT_MINOR) && !arch_has_dev_port())
> continue;
> - if ((minor == DEVMEM_MINOR) && devmem_init_inode() != 0)
> - continue;
>
> device_create(mem_class, NULL, MKDEV(MEM_MAJOR, minor),
> NULL, devlist[minor].name);
> diff --git a/include/linux/ioport.h b/include/linux/ioport.h
> index 6c2b06fe8beb..8ffb61b36606 100644
> --- a/include/linux/ioport.h
> +++ b/include/linux/ioport.h
> @@ -302,11 +302,7 @@ struct resource *devm_request_free_mem_region(struct device *dev,
> struct resource *request_free_mem_region(struct resource *base,
> unsigned long size, const char *name);
>
> -#ifdef CONFIG_IO_STRICT_DEVMEM
> -void revoke_devmem(struct resource *res);
> -#else
> -static inline void revoke_devmem(struct resource *res) { };
> -#endif
> +extern struct address_space *iomem_get_mapping(void);
>
> #endif /* __ASSEMBLY__ */
> #endif /* _LINUX_IOPORT_H */
> diff --git a/kernel/resource.c b/kernel/resource.c
> index 841737bbda9e..a92fed5b9997 100644
> --- a/kernel/resource.c
> +++ b/kernel/resource.c
> @@ -18,12 +18,15 @@
> #include <linux/spinlock.h>
> #include <linux/fs.h>
> #include <linux/proc_fs.h>
> +#include <linux/pseudo_fs.h>
> #include <linux/sched.h>
> #include <linux/seq_file.h>
> #include <linux/device.h>
> #include <linux/pfn.h>
> #include <linux/mm.h>
> +#include <linux/mount.h>
> #include <linux/resource_ext.h>
> +#include <uapi/linux/magic.h>
> #include <asm/io.h>
>
>
> @@ -1112,6 +1115,58 @@ resource_size_t resource_alignment(struct resource *res)
>
> static DECLARE_WAIT_QUEUE_HEAD(muxed_resource_wait);
>
> +static struct inode *iomem_inode;
> +
> +#ifdef CONFIG_IO_STRICT_DEVMEM
> +static void revoke_iomem(struct resource *res)
> +{
> + /* pairs with smp_store_release() in iomem_init_inode() */
> + struct inode *inode = smp_load_acquire(&iomem_inode);
> +
> + /*
> + * Check that the initialization has completed. Losing the race
> + * is ok because it means drivers are claiming resources before
> + * the fs_initcall level of init and prevent /dev/mem from
How about:
s,/dev/mem,iomem_get_mapping() users,
...now that this facility is generalized?
> + * establishing mappings.
> + */
> + if (!inode)
> + return;
> +
> + /*
> + * The expectation is that the driver has successfully marked
> + * the resource busy by this point, so devmem_is_allowed()
> + * should start returning false, however for performance this
> + * does not iterate the entire resource range.
> + */
> + if (devmem_is_allowed(PHYS_PFN(res->start)) &&
> + devmem_is_allowed(PHYS_PFN(res->end))) {
> + /*
> + * *cringe* iomem=relaxed says "go ahead, what's the
> + * worst that can happen?"
> + */
> + return;
> + }
> +
> + unmap_mapping_range(inode->i_mapping, res->start, resource_size(res), 1);
> +}
> +struct address_space *iomem_get_mapping(void)
> +{
> + /*
> + * This function is only called from file open paths, hence guaranteed
> + * that fs_initcalls have completed and no need to check for NULL. But
> + * since revoke_iomem can be called before the initcall we still need
> + * the barrier to appease checkers.
> + */
> + return smp_load_acquire(&iomem_inode)->i_mapping;
> +}
> +#else
> +static void revoke_iomem(struct resource *res) {}
> +struct address_space *iomem_get_mapping(void)
> +{
> + return NULL;
> +}
> +#endif
> +
> /**
> * __request_region - create a new busy resource region
> * @parent: parent resource descriptor
> @@ -1179,7 +1234,7 @@ struct resource * __request_region(struct resource *parent,
> write_unlock(&resource_lock);
>
> if (res && orig_parent == &iomem_resource)
> - revoke_devmem(res);
> + revoke_iomem(res);
>
> return res;
> }
> @@ -1713,4 +1768,48 @@ static int __init strict_iomem(char *str)
> return 1;
> }
>
> +static int iomem_fs_init_fs_context(struct fs_context *fc)
> +{
> + return init_pseudo(fc, DEVMEM_MAGIC) ? 0 : -ENOMEM;
> +}
> +
> +static struct file_system_type iomem_fs_type = {
> + .name = "iomem",
> + .owner = THIS_MODULE,
> + .init_fs_context = iomem_fs_init_fs_context,
> + .kill_sb = kill_anon_super,
> +};
> +
> +static int __init iomem_init_inode(void)
> +{
> + static struct vfsmount *iomem_vfs_mount;
> + static int iomem_fs_cnt;
> + struct inode *inode;
> + int rc;
> +
> + rc = simple_pin_fs(&iomem_fs_type, &iomem_vfs_mount, &iomem_fs_cnt);
> + if (rc < 0) {
> + pr_err("Cannot mount iomem pseudo filesystem: %d\n", rc);
> + return rc;
> + }
> +
> + inode = alloc_anon_inode(iomem_vfs_mount->mnt_sb);
> + if (IS_ERR(inode)) {
> + rc = PTR_ERR(inode);
> + pr_err("Cannot allocate inode for iomem: %d\n", rc);
> + simple_release_fs(&iomem_vfs_mount, &iomem_fs_cnt);
> + return rc;
> + }
> +
> + /*
> + * Publish /dev/mem initialized.
Similar potential fixup:
"Publish iomem revocation inode initialized"
Other than that:
Reviewed-by: Dan Williams <[email protected]>
On Wed, Oct 21, 2020 at 8:59 PM Dan Williams <[email protected]> wrote:
>
> On Wed, Oct 21, 2020 at 1:57 AM Daniel Vetter <[email protected]> wrote:
> >
> > We want all iomem mmaps to consistently revoke ptes when the kernel
> > takes over and CONFIG_IO_STRICT_DEVMEM is enabled. This includes the
> > pci bar mmaps available through procfs and sysfs, which currently do
> > not revoke mappings.
> >
> > To prepare for this, move the code from the /dev/kmem driver to
> > kernel/resource.c.
> >
> > Reviewed-by: Greg Kroah-Hartman <[email protected]>
> > Signed-off-by: Daniel Vetter <[email protected]>
> > Cc: Jason Gunthorpe <[email protected]>
> > Cc: Kees Cook <[email protected]>
> > Cc: Dan Williams <[email protected]>
> > Cc: Andrew Morton <[email protected]>
> > Cc: John Hubbard <[email protected]>
> > Cc: Jérôme Glisse <[email protected]>
> > Cc: Jan Kara <[email protected]>
> > Cc: Dan Williams <[email protected]>
> > Cc: [email protected]
> > Cc: [email protected]
> > Cc: [email protected]
> > Cc: [email protected]
> > Cc: Arnd Bergmann <[email protected]>
> > Cc: Greg Kroah-Hartman <[email protected]>
> > Cc: Daniel Vetter <[email protected]>
> > Cc: David Hildenbrand <[email protected]>
> > Cc: "Rafael J. Wysocki" <[email protected]>
> > Signed-off-by: Daniel Vetter <[email protected]>
> > --
> > v3:
> > - add barrier for consistency and document why we don't have to check
> > for NULL (Jason)
> > ---
> > drivers/char/mem.c | 85 +---------------------------------
> > include/linux/ioport.h | 6 +--
> > kernel/resource.c | 101 ++++++++++++++++++++++++++++++++++++++++-
> > 3 files changed, 102 insertions(+), 90 deletions(-)
> >
> > diff --git a/drivers/char/mem.c b/drivers/char/mem.c
> > index 5502f56f3655..53338aad8d28 100644
> > --- a/drivers/char/mem.c
> > +++ b/drivers/char/mem.c
> > @@ -31,9 +31,6 @@
> > #include <linux/uio.h>
> > #include <linux/uaccess.h>
> > #include <linux/security.h>
> > -#include <linux/pseudo_fs.h>
> > -#include <uapi/linux/magic.h>
> > -#include <linux/mount.h>
> >
> > #ifdef CONFIG_IA64
> > # include <linux/efi.h>
> > @@ -809,42 +806,6 @@ static loff_t memory_lseek(struct file *file, loff_t offset, int orig)
> > return ret;
> > }
> >
> > -static struct inode *devmem_inode;
> > -
> > -#ifdef CONFIG_IO_STRICT_DEVMEM
> > -void revoke_devmem(struct resource *res)
> > -{
> > - /* pairs with smp_store_release() in devmem_init_inode() */
> > - struct inode *inode = smp_load_acquire(&devmem_inode);
> > -
> > - /*
> > - * Check that the initialization has completed. Losing the race
> > - * is ok because it means drivers are claiming resources before
> > - * the fs_initcall level of init and prevent /dev/mem from
> > - * establishing mappings.
> > - */
> > - if (!inode)
> > - return;
> > -
> > - /*
> > - * The expectation is that the driver has successfully marked
> > - * the resource busy by this point, so devmem_is_allowed()
> > - * should start returning false, however for performance this
> > - * does not iterate the entire resource range.
> > - */
> > - if (devmem_is_allowed(PHYS_PFN(res->start)) &&
> > - devmem_is_allowed(PHYS_PFN(res->end))) {
> > - /*
> > - * *cringe* iomem=relaxed says "go ahead, what's the
> > - * worst that can happen?"
> > - */
> > - return;
> > - }
> > -
> > - unmap_mapping_range(inode->i_mapping, res->start, resource_size(res), 1);
> > -}
> > -#endif
> > -
> > static int open_port(struct inode *inode, struct file *filp)
> > {
> > int rc;
> > @@ -864,7 +825,7 @@ static int open_port(struct inode *inode, struct file *filp)
> > * revocations when drivers want to take over a /dev/mem mapped
> > * range.
> > */
> > - filp->f_mapping = inode->i_mapping;
> > + filp->f_mapping = iomem_get_mapping();
> >
> > return 0;
> > }
> > @@ -995,48 +956,6 @@ static char *mem_devnode(struct device *dev, umode_t *mode)
> >
> > static struct class *mem_class;
> >
> > -static int devmem_fs_init_fs_context(struct fs_context *fc)
> > -{
> > - return init_pseudo(fc, DEVMEM_MAGIC) ? 0 : -ENOMEM;
> > -}
> > -
> > -static struct file_system_type devmem_fs_type = {
> > - .name = "devmem",
> > - .owner = THIS_MODULE,
> > - .init_fs_context = devmem_fs_init_fs_context,
> > - .kill_sb = kill_anon_super,
> > -};
> > -
> > -static int devmem_init_inode(void)
> > -{
> > - static struct vfsmount *devmem_vfs_mount;
> > - static int devmem_fs_cnt;
> > - struct inode *inode;
> > - int rc;
> > -
> > - rc = simple_pin_fs(&devmem_fs_type, &devmem_vfs_mount, &devmem_fs_cnt);
> > - if (rc < 0) {
> > - pr_err("Cannot mount /dev/mem pseudo filesystem: %d\n", rc);
> > - return rc;
> > - }
> > -
> > - inode = alloc_anon_inode(devmem_vfs_mount->mnt_sb);
> > - if (IS_ERR(inode)) {
> > - rc = PTR_ERR(inode);
> > - pr_err("Cannot allocate inode for /dev/mem: %d\n", rc);
> > - simple_release_fs(&devmem_vfs_mount, &devmem_fs_cnt);
> > - return rc;
> > - }
> > -
> > - /*
> > - * Publish /dev/mem initialized.
> > - * Pairs with smp_load_acquire() in revoke_devmem().
> > - */
> > - smp_store_release(&devmem_inode, inode);
> > -
> > - return 0;
> > -}
> > -
> > static int __init chr_dev_init(void)
> > {
> > int minor;
> > @@ -1058,8 +977,6 @@ static int __init chr_dev_init(void)
> > */
> > if ((minor == DEVPORT_MINOR) && !arch_has_dev_port())
> > continue;
> > - if ((minor == DEVMEM_MINOR) && devmem_init_inode() != 0)
> > - continue;
> >
> > device_create(mem_class, NULL, MKDEV(MEM_MAJOR, minor),
> > NULL, devlist[minor].name);
> > diff --git a/include/linux/ioport.h b/include/linux/ioport.h
> > index 6c2b06fe8beb..8ffb61b36606 100644
> > --- a/include/linux/ioport.h
> > +++ b/include/linux/ioport.h
> > @@ -302,11 +302,7 @@ struct resource *devm_request_free_mem_region(struct device *dev,
> > struct resource *request_free_mem_region(struct resource *base,
> > unsigned long size, const char *name);
> >
> > -#ifdef CONFIG_IO_STRICT_DEVMEM
> > -void revoke_devmem(struct resource *res);
> > -#else
> > -static inline void revoke_devmem(struct resource *res) { };
> > -#endif
> > +extern struct address_space *iomem_get_mapping(void);
> >
> > #endif /* __ASSEMBLY__ */
> > #endif /* _LINUX_IOPORT_H */
> > diff --git a/kernel/resource.c b/kernel/resource.c
> > index 841737bbda9e..a92fed5b9997 100644
> > --- a/kernel/resource.c
> > +++ b/kernel/resource.c
> > @@ -18,12 +18,15 @@
> > #include <linux/spinlock.h>
> > #include <linux/fs.h>
> > #include <linux/proc_fs.h>
> > +#include <linux/pseudo_fs.h>
> > #include <linux/sched.h>
> > #include <linux/seq_file.h>
> > #include <linux/device.h>
> > #include <linux/pfn.h>
> > #include <linux/mm.h>
> > +#include <linux/mount.h>
> > #include <linux/resource_ext.h>
> > +#include <uapi/linux/magic.h>
> > #include <asm/io.h>
> >
> >
> > @@ -1112,6 +1115,58 @@ resource_size_t resource_alignment(struct resource *res)
> >
> > static DECLARE_WAIT_QUEUE_HEAD(muxed_resource_wait);
> >
> > +static struct inode *iomem_inode;
> > +
> > +#ifdef CONFIG_IO_STRICT_DEVMEM
> > +static void revoke_iomem(struct resource *res)
> > +{
> > + /* pairs with smp_store_release() in iomem_init_inode() */
> > + struct inode *inode = smp_load_acquire(&iomem_inode);
> > +
> > + /*
> > + * Check that the initialization has completed. Losing the race
> > + * is ok because it means drivers are claiming resources before
> > + * the fs_initcall level of init and prevent /dev/mem from
>
> How about:
>
> s,/dev/mem,iomem_get_mapping() users,
>
> ...now that this facility is generalized?
>
> > + * establishing mappings.
> > + */
> > + if (!inode)
> > + return;
> > +
> > + /*
> > + * The expectation is that the driver has successfully marked
> > + * the resource busy by this point, so devmem_is_allowed()
> > + * should start returning false, however for performance this
> > + * does not iterate the entire resource range.
> > + */
> > + if (devmem_is_allowed(PHYS_PFN(res->start)) &&
> > + devmem_is_allowed(PHYS_PFN(res->end))) {
> > + /*
> > + * *cringe* iomem=relaxed says "go ahead, what's the
> > + * worst that can happen?"
> > + */
> > + return;
> > + }
> > +
> > + unmap_mapping_range(inode->i_mapping, res->start, resource_size(res), 1);
> > +}
> > +struct address_space *iomem_get_mapping(void)
> > +{
> > + /*
> > + * This function is only called from file open paths, hence guaranteed
> > + * that fs_initcalls have completed and no need to check for NULL. But
> > + * since revoke_iomem can be called before the initcall we still need
> > + * the barrier to appease checkers.
> > + */
> > + return smp_load_acquire(&iomem_inode)->i_mapping;
> > +}
> > +#else
> > +static void revoke_iomem(struct resource *res) {}
> > +struct address_space *iomem_get_mapping(void)
> > +{
> > + return NULL;
> > +}
> > +#endif
> > +
> > /**
> > * __request_region - create a new busy resource region
> > * @parent: parent resource descriptor
> > @@ -1179,7 +1234,7 @@ struct resource * __request_region(struct resource *parent,
> > write_unlock(&resource_lock);
> >
> > if (res && orig_parent == &iomem_resource)
> > - revoke_devmem(res);
> > + revoke_iomem(res);
> >
> > return res;
> > }
> > @@ -1713,4 +1768,48 @@ static int __init strict_iomem(char *str)
> > return 1;
> > }
> >
> > +static int iomem_fs_init_fs_context(struct fs_context *fc)
> > +{
> > + return init_pseudo(fc, DEVMEM_MAGIC) ? 0 : -ENOMEM;
> > +}
> > +
> > +static struct file_system_type iomem_fs_type = {
> > + .name = "iomem",
> > + .owner = THIS_MODULE,
> > + .init_fs_context = iomem_fs_init_fs_context,
> > + .kill_sb = kill_anon_super,
> > +};
> > +
> > +static int __init iomem_init_inode(void)
> > +{
> > + static struct vfsmount *iomem_vfs_mount;
> > + static int iomem_fs_cnt;
> > + struct inode *inode;
> > + int rc;
> > +
> > + rc = simple_pin_fs(&iomem_fs_type, &iomem_vfs_mount, &iomem_fs_cnt);
> > + if (rc < 0) {
> > + pr_err("Cannot mount iomem pseudo filesystem: %d\n", rc);
> > + return rc;
> > + }
> > +
> > + inode = alloc_anon_inode(iomem_vfs_mount->mnt_sb);
> > + if (IS_ERR(inode)) {
> > + rc = PTR_ERR(inode);
> > + pr_err("Cannot allocate inode for iomem: %d\n", rc);
> > + simple_release_fs(&iomem_vfs_mount, &iomem_fs_cnt);
> > + return rc;
> > + }
> > +
> > + /*
> > + * Publish /dev/mem initialized.
>
> Similar potential fixup:
>
> "Publish iomem revocation inode initialized"
Yeah makes sense I fix up the comments, I'll do that in v4. Need to
fix up my mangeld sob line anyway :-)
Thanks for taking a careful look at this!
Cheers, Daniel
> Other than that:
>
> Reviewed-by: Dan Williams <[email protected]>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch