On Tue, 25 Nov 2014 16:50:15 +0200 , Pantelis Antoniou <[email protected]> wrote: > Hi Grant, > > > On Nov 25, 2014, at 12:28 , Grant Likely <[email protected]> wrote: > > > > Hi Pantelis, > > > > Comments below... > > > > On Tue, 28 Oct 2014 22:36:00 +0200 > > , Pantelis Antoniou <[email protected]> > > wrote: > >> Add a runtime interface to using configfs for generic device tree overlay > >> usage. > >> > >> A device-tree configfs entry is created in /config/device-tree/overlays > >> > >> * To create an overlay you mkdir the directory: > >> > >> # mkdir /config/device-tree/overlays/foo > >> > >> * Either you echo the overlay firmware file to the path property file. > >> > >> # echo foo.dtbo >/config/device-tree/overlays/foo/path > >> > >> * Or you cat the contents of the overlay to the dtbo file > >> > >> # cat foo.dtbo >/config/device-tree/overlays/foo/dtbo > >> > >> The overlay file will be applied. > >> > >> To remove it simply rmdir the directory. > >> > >> # rmdir /config/device-tree/overlays/foo > > > > The above is documentation on how to use it, but it isn't a good commit > > message. The above should be moved into a documentation file (if it > > isn't already and I've missed it) and the commit message should give > > detail about what was needed, what was changed to make it happen, and > > what the result of the new code is. > > > > Hmm, okie dokie. > > >> > >> Changes since v1: > >> * of_resolve() -> of_resolve_phandles(). > >> > >> Signed-off-by: Pantelis Antoniou <[email protected]> > >> --- > >> drivers/of/Kconfig | 7 ++ > >> drivers/of/Makefile | 1 + > >> drivers/of/configfs.c | 340 > >> ++++++++++++++++++++++++++++++++++++++++++++++++++ > >> 3 files changed, 348 insertions(+) > >> create mode 100644 drivers/of/configfs.c > >> > >> diff --git a/drivers/of/Kconfig b/drivers/of/Kconfig > >> index aa315c4..d59ba40 100644 > >> --- a/drivers/of/Kconfig > >> +++ b/drivers/of/Kconfig > >> @@ -90,4 +90,11 @@ config OF_OVERLAY > >> select OF_DEVICE > >> select OF_RESOLVE > >> > >> +config OF_CONFIGFS > >> + bool "OpenFirmware Overlay ConfigFS interface" > > > > Despite all the APIs being prefixed with OpenFirmware, this isn't an > > OpenFirmware interface, it is a device tree interface. > > > > OK, so device tree config fs interface?
Yes > > >> + select CONFIGFS_FS > >> + select OF_OVERLAY > >> + help > >> + Enable a simple user-space driver DT overlay interface. > >> + > >> endmenu # OF > >> diff --git a/drivers/of/Makefile b/drivers/of/Makefile > >> index 1bfe462..6d12949 100644 > >> --- a/drivers/of/Makefile > >> +++ b/drivers/of/Makefile > >> @@ -15,6 +15,7 @@ obj-$(CONFIG_OF_MTD) += of_mtd.o > >> obj-$(CONFIG_OF_RESERVED_MEM) += of_reserved_mem.o > >> obj-$(CONFIG_OF_RESOLVE) += resolver.o > >> obj-$(CONFIG_OF_OVERLAY) += overlay.o > >> +obj-$(CONFIG_OF_CONFIGFS) += configfs.o > > > > Tip: Insert lines in the middle of the block, roughly alphabetically > > sorted. It cuts down on merge conflicts that way. > > > > k > > >> > >> CFLAGS_fdt.o = -I$(src)/../../scripts/dtc/libfdt > >> CFLAGS_fdt_address.o = -I$(src)/../../scripts/dtc/libfdt > >> diff --git a/drivers/of/configfs.c b/drivers/of/configfs.c > >> new file mode 100644 > >> index 0000000..932f572 > >> --- /dev/null > >> +++ b/drivers/of/configfs.c > >> @@ -0,0 +1,340 @@ > >> +/* > >> + * Configfs entries for device-tree > >> + * > >> + * Copyright (C) 2013 - Pantelis Antoniou <[email protected]> > >> + * > >> + * This program is free software; you can redistribute it and/or > >> + * modify it under the terms of the GNU General Public License > >> + * as published by the Free Software Foundation; either version > >> + * 2 of the License, or (at your option) any later version. > >> + */ > >> +#include <linux/ctype.h> > >> +#include <linux/cpu.h> > >> +#include <linux/module.h> > >> +#include <linux/of.h> > >> +#include <linux/of_fdt.h> > >> +#include <linux/spinlock.h> > >> +#include <linux/slab.h> > >> +#include <linux/proc_fs.h> > >> +#include <linux/configfs.h> > >> +#include <linux/types.h> > >> +#include <linux/stat.h> > >> +#include <linux/limits.h> > >> +#include <linux/file.h> > >> +#include <linux/vmalloc.h> > >> +#include <linux/firmware.h> > >> + > >> +#include "of_private.h" > >> + > >> +#ifdef CONFIG_OF_OVERLAY > > > > ??? > > > > This file shouldn't even be compiled if CONFIG_OF_OVERLAY isn't > > selected. Why is this here? > > > > Err, good question. > > >> + > >> +struct cfs_overlay_item { > >> + struct config_item item; > >> + > >> + char path[PATH_MAX]; > >> + > >> + const struct firmware *fw; > >> + struct device_node *overlay; > >> + int ov_id; > >> + > >> + void *dtbo; > >> + int dtbo_size; > >> +}; > >> + > >> +static int create_overlay(struct cfs_overlay_item *overlay, void *blob) > >> +{ > >> + int err; > >> + > >> + /* unflatten the tree */ > >> + of_fdt_unflatten_tree((void *)blob, &overlay->overlay); > > > > blob is already void* > > > > ok > > >> + if (overlay->overlay == NULL) { > >> + pr_err("%s: failed to unflatten tree\n", __func__); > >> + err = -EINVAL; > >> + goto out_err; > >> + } > >> + pr_debug("%s: unflattened OK\n", __func__); > >> + > >> + /* mark it as detached */ > >> + of_node_set_flag(overlay->overlay, OF_DETACHED); > >> + > >> + /* perform resolution */ > >> + err = of_resolve_phandles(overlay->overlay); > >> + if (err != 0) { > >> + pr_err("%s: Failed to resolve tree\n", __func__); > >> + goto out_err; > >> + } > >> + pr_debug("%s: resolved OK\n", __func__); > >> + > >> + err = of_overlay_create(overlay->overlay); > >> + if (err < 0) { > >> + pr_err("%s: Failed to create overlay (err=%d)\n", > >> + __func__, err); > >> + goto out_err; > >> + } > >> + overlay->ov_id = err; > >> + > >> +out_err: > >> + return err; > >> +} > >> + > >> +static inline struct cfs_overlay_item *to_cfs_overlay_item( > >> + struct config_item *item) > >> +{ > >> + return item ? container_of(item, struct cfs_overlay_item, item) : NULL; > >> +} > >> + > >> +CONFIGFS_ATTR_STRUCT(cfs_overlay_item); > >> +#define CFS_OVERLAY_ITEM_ATTR(_name, _mode, _show, _store) \ > >> +struct cfs_overlay_item_attribute cfs_overlay_item_attr_##_name = \ > >> + __CONFIGFS_ATTR(_name, _mode, _show, _store) > >> +#define CFS_OVERLAY_ITEM_ATTR_RO(_name, _show) \ > >> +struct cfs_overlay_item_attribute cfs_overlay_item_attr_##_name = \ > >> + __CONFIGFS_ATTR_RO(_name, _show) > >> + > >> +CONFIGFS_BIN_ATTR_STRUCT(cfs_overlay_item); > >> +#define CFS_OVERLAY_ITEM_BIN_ATTR(_name, _mode, _read, _write, _priv, > >> _max) \ > >> +struct cfs_overlay_item_bin_attribute cfs_overlay_item_bin_attr_##_name = > >> \ > >> + __CONFIGFS_BIN_ATTR(_name, _mode, _read, _write, _priv, _max) > >> +#define CFS_OVERLAY_ITEM_BIN_ATTR_RO(_name, _read, _priv, _max) \ > >> +struct cfs_overlay_item_bin_attribute cfs_overlay_item_bin_attr_##_name = > >> \ > >> + __CONFIGFS_BIN_ATTR_RO(_name, _read, _priv, _max) > >> + > >> +static ssize_t cfs_overlay_item_path_show(struct cfs_overlay_item > >> *overlay, > >> + char *page) > >> +{ > >> + return sprintf(page, "%s\n", overlay->path); > >> +} > >> + > >> +static ssize_t cfs_overlay_item_path_store(struct cfs_overlay_item > >> *overlay, > >> + const char *page, size_t count) > >> +{ > >> + const char *p = page; > >> + char *s; > >> + int err; > >> + > >> + /* if it's set do not allow changes */ > >> + if (overlay->path[0] != '\0' || overlay->dtbo_size > 0) > >> + return -EPERM; > >> + > >> + /* copy to path buffer (and make sure it's always zero terminated */ > >> + count = snprintf(overlay->path, sizeof(overlay->path) - 1, "%s", p); > >> + overlay->path[sizeof(overlay->path) - 1] = '\0'; > >> + > >> + /* strip trailing newlines */ > >> + s = overlay->path + strlen(overlay->path); > >> + while (s > overlay->path && *--s == '\n') > >> + *s = '\0'; > >> + > >> + pr_debug("%s: path is '%s'\n", __func__, overlay->path); > >> + > >> + err = request_firmware(&overlay->fw, overlay->path, NULL); > >> + if (err != 0) > >> + goto out_err; > >> + > >> + err = create_overlay(overlay, (void *)overlay->fw->data); > >> + if (err != 0) > >> + goto out_err; > >> + > >> + return count; > >> + > >> +out_err: > >> + > >> + release_firmware(overlay->fw); > >> + overlay->fw = NULL; > >> + > >> + overlay->path[0] = '\0'; > >> + return err; > >> +} > >> + > >> +static ssize_t cfs_overlay_item_status_show(struct cfs_overlay_item > >> *overlay, > >> + char *page) > >> +{ > >> + return sprintf(page, "%s\n", > >> + overlay->ov_id >= 0 ? "applied" : "unapplied"); > >> +} > >> + > >> +CFS_OVERLAY_ITEM_ATTR(path, S_IRUGO | S_IWUSR, > >> + cfs_overlay_item_path_show, cfs_overlay_item_path_store); > > > > World writable? Am I reading this correctly? > > > > Err, user writeable, world readable. â-rw-r--râ" Oops, I did read it wrong. Sorry for the noise > > DT modifications are privileged. A user can potentially get arbitrary > > access to i2c, spi, gpio or other things that shouldn't be allowed. This > > feature give access right into the Linux driver model. > > > > Yes, it does. > > > Before this can be merged, it needs to be locked down, and there needs > > to be documentation about how it is locked down. Owned by root is only > > the first step, there also needs to be some rules about which nodes can > > be modified by the configfs interface. By default think no modifications > > should be allowed on a tree unless there are properties somewhere in the > > tree that explicitly allow modifications to be performed. > > > > TBH this is more of a debug level interface. The way I see it a different > overlay manager, thatâs tuned to the platform, should handle the overlay > request and application, in a manner thatâs not directly open to user > control. For example in a beaglebone youâd have a âcapeâ manager reading > the i2c eeproms and request the overlays they match without any user-space > implication. Right. > However, this is an interface that developers will use daily, so I agree > that we need to look into the security model now before itâs too late. > > How do you feel for something like this in chosen: > > overlay-targets = â/ocpâ, â/pinctrlâ; It's a reasonable proposal. I'd like to have some time to think on it though. The other way to do it would be to add properties throughout the tree that mask/unmask modifications by overlay. I think the overlays are more a property of the board than a configurable boot time argument (so not something that would normally go in /chosen) g. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
