On 07/26/15 01:21, Gabriel L. Somlo wrote:
> On Tue, Jul 21, 2015 at 12:07:08AM +0200, Laszlo Ersek wrote:
>> On 07/20/15 23:19, Gabriel L. Somlo wrote:
>>
>> ... I just love "find", sorry. :) Anyway, I don't envision myself as a
>> user of this feature any time soon, so please feel free to ignore me.
>
> How about this: I create /sys/firmware/fw_cfg/by_select with *all*
> entries, named after their selector key, in a flat folder.
I think this is nice. The fw_cfg directory blob itself is available at a
fixed key (FW_CFG_FILE_DIR, 0x0019, and it is even documented :)), so
for a fool-proof, non-interactive lookup, a C language program can
search the 0x0019 blob, grab the relevant key value, and then open
/sys/firmware/fw_cfg/by_select/<THAT_KEY>.
For interactive use or scripting, "by_name" can be used with "find" etc.
I think this is really nice.
Thanks
Laszlo
> Then, I also create /sys/firmware/fw_cfg/by_name/... where I try to
> build the folder hierarchy given by whatever the file names end up
> being, *on a best effort basis*, i.e. I may fail to create *some* of
> them, if they have brain-damaged names :)
>
> The kernel will issue big scary warnings if a symlink already exists
> where I'm trying to add a new subdirectory of the same name, or the
> other way around.
>
> The whole thing is below, tested and working on x86 and arm (so one
> example of IOPort and one example of MMIO).
>
> I'm out all of next week, but will submit this to the kernel (and cc
> Greg-K-H as advised by Matt) once I get back.
>
> In the mean time, any final words of wisdom, advice, testing, etc.
> much much appreciated !
>
> Cheers,
> --Gabriel
>
>
> /*
> * drivers/firmware/fw_cfg.c
> *
> * Expose entries from QEMU's firmware configuration (fw_cfg) device in
> * sysfs (read-only, under "/sys/firmware/fw_cfg/...").
> *
> * Copyright 2015 Gabriel L. Somlo <so...@cmu.edu>
> *
> * This program is free software; you can redistribute it and/or modify
> * it under the terms of the GNU General Public License v2 as published
> * by the Free Software Foundation.
> *
> * This program is distributed in the hope that it will be useful, but
> * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
> * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
> * for more details.
> *
> * You should have received a copy of the GNU General Public License along
> * with this program; if not, write to the Free Software Foundation, Inc.,
> * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
> */
>
> #include <linux/module.h>
> #include <linux/capability.h>
> #include <linux/slab.h>
> #include <linux/io.h>
> #include <linux/ioport.h>
> #include <linux/ctype.h>
>
> /* selector values for "well-known" fw_cfg entries */
> #define FW_CFG_SIGNATURE 0x00
> #define FW_CFG_FILE_DIR 0x19
>
> /* size in bytes of fw_cfg signature */
> #define FW_CFG_SIG_SIZE 4
>
> /* fw_cfg "file name" is up to 56 characters (including terminating nul) */
> #define FW_CFG_MAX_FILE_PATH 56
>
> /* fw_cfg file directory entry type */
> struct fw_cfg_file {
> uint32_t size;
> uint16_t select;
> uint16_t reserved;
> char name[FW_CFG_MAX_FILE_PATH];
> };
>
> /* fw_cfg device i/o access options type */
> struct fw_cfg_access {
> phys_addr_t start;
> uint8_t size;
> uint8_t ctrl_offset;
> uint8_t data_offset;
> bool is_mmio;
> const char *name;
> };
>
> /* fw_cfg device i/o access available options for known architectures */
> static struct fw_cfg_access fw_cfg_modes[] = {
> { 0x510, 2, 0, 1, false, "fw_cfg on i386, sun4u" },
> { 0x9020000, 10, 8, 0, true, "fw_cfg on arm" },
> { 0xd00000510, 3, 0, 2, true, "fw_cfg on sun4m" },
> { 0xf0000510, 3, 0, 2, true, "fw_cfg on ppc/mac" },
> { }
> };
>
> /* fw_cfg device i/o currently selected option set */
> static struct fw_cfg_access *fw_cfg_mode;
>
> /* fw_cfg device i/o register addresses */
> static void __iomem *fw_cfg_dev_base;
> static void __iomem *fw_cfg_dev_ctrl;
> static void __iomem *fw_cfg_dev_data;
>
> /* atomic access to fw_cfg device (potentially slow i/o, so using mutex) */
> static DEFINE_MUTEX(fw_cfg_dev_lock);
>
> /* pick apropriate endianness for selector key */
> static inline uint16_t fw_cfg_sel_endianness(uint16_t select)
> {
> return fw_cfg_mode->is_mmio ? cpu_to_be16(select) : cpu_to_le16(select);
> }
>
> /* type for fw_cfg "directory scan" visitor/callback function */
> typedef int (*fw_cfg_file_callback)(const struct fw_cfg_file *f);
>
> /* run a given callback on each fw_cfg directory entry */
> static int fw_cfg_scan_dir(fw_cfg_file_callback callback)
> {
> int ret = 0;
> uint32_t count, i;
> struct fw_cfg_file f;
>
> mutex_lock(&fw_cfg_dev_lock);
> iowrite16(fw_cfg_sel_endianness(FW_CFG_FILE_DIR), fw_cfg_dev_ctrl);
> ioread8_rep(fw_cfg_dev_data, &count, sizeof(count));
> for (i = 0; i < be32_to_cpu(count); i++) {
> ioread8_rep(fw_cfg_dev_data, &f, sizeof(f));
> ret = callback(&f);
> if (ret)
> break;
> }
> mutex_unlock(&fw_cfg_dev_lock);
> return ret;
> }
>
> /* read chunk of given fw_cfg blob (caller responsible for sanity-check) */
> static inline void fw_cfg_read_blob(uint16_t select,
> void *buf, loff_t pos, size_t count)
> {
> mutex_lock(&fw_cfg_dev_lock);
> iowrite16(fw_cfg_sel_endianness(select), fw_cfg_dev_ctrl);
> while (pos-- > 0)
> ioread8(fw_cfg_dev_data);
> ioread8_rep(fw_cfg_dev_data, buf, count);
> mutex_unlock(&fw_cfg_dev_lock);
> }
>
> /* clean up fw_cfg device i/o setup */
> static void fw_cfg_io_cleanup(void)
> {
> if (fw_cfg_mode->is_mmio) {
> iounmap(fw_cfg_dev_base);
> release_mem_region(fw_cfg_mode->start, fw_cfg_mode->size);
> } else {
> ioport_unmap(fw_cfg_dev_base);
> release_region(fw_cfg_mode->start, fw_cfg_mode->size);
> }
> }
>
> /* probe and map fw_cfg device */
> static int __init fw_cfg_io_probe(void)
> {
> char sig[FW_CFG_SIG_SIZE];
>
> for (fw_cfg_mode = &fw_cfg_modes[0];
> fw_cfg_mode->start; fw_cfg_mode++) {
>
> phys_addr_t start = fw_cfg_mode->start;
> uint8_t size = fw_cfg_mode->size;
>
> /* reserve and map mmio or ioport region */
> if (fw_cfg_mode->is_mmio) {
> if (!request_mem_region(start, size, fw_cfg_mode->name))
> continue;
> fw_cfg_dev_base = ioremap(start, size);
> if (!fw_cfg_dev_base) {
> release_mem_region(start, size);
> continue;
> }
> } else {
> if (!request_region(start, size, fw_cfg_mode->name))
> continue;
> fw_cfg_dev_base = ioport_map(start, size);
> if (!fw_cfg_dev_base) {
> release_region(start, size);
> continue;
> }
> }
>
> /* set control and data register addresses */
> fw_cfg_dev_ctrl = fw_cfg_dev_base + fw_cfg_mode->ctrl_offset;
> fw_cfg_dev_data = fw_cfg_dev_base + fw_cfg_mode->data_offset;
>
> /* verify fw_cfg device signature */
> fw_cfg_read_blob(FW_CFG_SIGNATURE, sig, 0, FW_CFG_SIG_SIZE);
> if (memcmp(sig, "QEMU", FW_CFG_SIG_SIZE) == 0)
> /* success, we're done */
> return 0;
>
> /* clean up before probing next access mode */
> fw_cfg_io_cleanup();
> }
>
> return -ENODEV;
> }
>
> /* fw_cfg_sysfs_entry type */
> struct fw_cfg_sysfs_entry {
> struct kobject kobj;
> struct fw_cfg_file f;
> struct list_head list;
> };
>
> /* get fw_cfg_sysfs_entry from kobject member */
> static inline struct fw_cfg_sysfs_entry *to_entry(struct kobject *kobj)
> {
> return container_of(kobj, struct fw_cfg_sysfs_entry, kobj);
> }
>
> /* fw_cfg_sysfs_attribute type */
> struct fw_cfg_sysfs_attribute {
> struct attribute attr;
> ssize_t (*show)(struct fw_cfg_sysfs_entry *entry, char *buf);
> };
>
> /* get fw_cfg_sysfs_attribute from attribute member */
> static inline struct fw_cfg_sysfs_attribute *to_attr(struct attribute *attr)
> {
> return container_of(attr, struct fw_cfg_sysfs_attribute, attr);
> }
>
> /* global cache of fw_cfg_sysfs_entry objects */
> static LIST_HEAD(fw_cfg_entry_cache);
>
> /* kobjects removed lazily by kernel, mutual exclusion needed */
> static DEFINE_SPINLOCK(fw_cfg_cache_lock);
>
> static inline void fw_cfg_sysfs_cache_enlist(struct fw_cfg_sysfs_entry *entry)
> {
> spin_lock(&fw_cfg_cache_lock);
> list_add_tail(&entry->list, &fw_cfg_entry_cache);
> spin_unlock(&fw_cfg_cache_lock);
> }
>
> static inline void fw_cfg_sysfs_cache_delist(struct fw_cfg_sysfs_entry *entry)
> {
> spin_lock(&fw_cfg_cache_lock);
> list_del(&entry->list);
> spin_unlock(&fw_cfg_cache_lock);
> }
>
> static void fw_cfg_sysfs_cache_cleanup(void)
> {
> struct fw_cfg_sysfs_entry *entry, *next;
>
> list_for_each_entry_safe(entry, next, &fw_cfg_entry_cache, list) {
> /* will end up invoking fw_cfg_sysfs_cache_delist()
> * via each object's release() method (i.e. destructor) */
> kobject_put(&entry->kobj);
> }
> }
>
> /* default_attrs: per-entry attributes and show methods */
>
> #define FW_CFG_SYSFS_ATTR(_attr) \
> struct fw_cfg_sysfs_attribute fw_cfg_sysfs_attr_##_attr = { \
> .attr = { .name = __stringify(_attr), .mode = 0400 }, \
> .show = fw_cfg_sysfs_show_##_attr, \
> }
>
> static ssize_t fw_cfg_sysfs_show_size(struct fw_cfg_sysfs_entry *e, char *buf)
> {
> return sprintf(buf, "%d\n", e->f.size);
> }
>
> static ssize_t fw_cfg_sysfs_show_select(struct fw_cfg_sysfs_entry *e, char
> *buf)
> {
> return sprintf(buf, "%d\n", e->f.select);
> }
>
> static ssize_t fw_cfg_sysfs_show_name(struct fw_cfg_sysfs_entry *e, char *buf)
> {
> return sprintf(buf, "%s\n", e->f.name);
> }
>
> static FW_CFG_SYSFS_ATTR(size);
> static FW_CFG_SYSFS_ATTR(select);
> static FW_CFG_SYSFS_ATTR(name);
>
> static struct attribute *fw_cfg_sysfs_entry_attrs[] = {
> &fw_cfg_sysfs_attr_size.attr,
> &fw_cfg_sysfs_attr_select.attr,
> &fw_cfg_sysfs_attr_name.attr,
> NULL,
> };
>
> /* sysfs_ops: find fw_cfg_[entry, attribute] and call appropriate show method
> */
> static ssize_t fw_cfg_sysfs_attr_show(struct kobject *kobj, struct attribute
> *a,
> char *buf)
> {
> struct fw_cfg_sysfs_entry *entry = to_entry(kobj);
> struct fw_cfg_sysfs_attribute *attr = to_attr(a);
>
> if (!capable(CAP_SYS_ADMIN))
> return -EACCES;
>
> return attr->show(entry, buf);
> }
>
> static const struct sysfs_ops fw_cfg_sysfs_attr_ops = {
> .show = fw_cfg_sysfs_attr_show,
> };
>
> /* release: destructor, to be called via kobject_put() */
> static void fw_cfg_sysfs_release_entry(struct kobject *kobj)
> {
> struct fw_cfg_sysfs_entry *entry = to_entry(kobj);
>
> fw_cfg_sysfs_cache_delist(entry);
> kfree(entry);
> }
>
> /* kobj_type: ties together all properties required to register an entry */
> static struct kobj_type fw_cfg_sysfs_entry_ktype = {
> .default_attrs = fw_cfg_sysfs_entry_attrs,
> .sysfs_ops = &fw_cfg_sysfs_attr_ops,
> .release = fw_cfg_sysfs_release_entry,
> };
>
> /* raw-read method and attribute */
> static ssize_t fw_cfg_sysfs_read_raw(struct file *filp, struct kobject *kobj,
> struct bin_attribute *bin_attr,
> char *buf, loff_t pos, size_t count)
> {
> struct fw_cfg_sysfs_entry *entry = to_entry(kobj);
>
> if (!capable(CAP_SYS_ADMIN))
> return -EACCES;
>
> if (pos > entry->f.size)
> return -EINVAL;
>
> if (count > entry->f.size - pos)
> count = entry->f.size - pos;
>
> fw_cfg_read_blob(entry->f.select, buf, pos, count);
> return count;
> }
>
> static struct bin_attribute fw_cfg_sysfs_attr_raw = {
> .attr = { .name = "raw", .mode = 0400 },
> .read = fw_cfg_sysfs_read_raw,
> };
>
> /*
> * kset_find_obj() is not EXPORTed from lib/kobject.c, clone it here for now.
> * FIXME: patch adding EXPORT in lib/kobject.c tested working, but then
> * building this module for older kernels wouldn't work anymore...
> */
> struct kobject *my_kset_find_obj(struct kset *kset, const char *name)
> {
> struct kobject *k;
> struct kobject *ret = NULL;
>
> spin_lock(&kset->list_lock);
>
> list_for_each_entry(k, &kset->list, entry) {
> if (kobject_name(k) && !strcmp(kobject_name(k), name)) {
> ret = kobject_get(k);
> break;
> }
> }
>
> spin_unlock(&kset->list_lock);
> return ret;
> }
>
> /*
> * Create a kset subdirectory matching each '/' delimited dirname token
> * in 'name', starting with sysfs kset/folder 'dir'; At the end, create
> * a symlink directed at the given 'target'.
> * NOTE: We do this on a best-effort basis, since 'name' is not guaranteed
> * to be a well-behaved path name. Whenever a symlink vs. kset directory
> * name collision occurs, the kernel will issue big scary warnings while
> * refusing to add the offending link or directory. We follow up with our
> * own, slightly less scary error messages explaining the situation :)
> */
> static void __init fw_cfg_build_symlink(struct kset *dir,
> struct kobject *target,
> const char *name)
> {
> struct kset *subdir;
> struct kobject *ko;
> char *name_copy, *p, *tok;
>
> if (!dir || !target || !name || !*name) {
> pr_err("fw_cfg: invalid argument to fw_cfg_build_symlink\n");
> return;
> }
>
> /* clone a copy of name for parsing */
> name_copy = p = kstrdup(name, GFP_KERNEL);
> if (!name_copy) {
> pr_err("fw_cfg: kstrdup failed while "
> "creating symlink %s\n", name);
> return;
> }
>
> /* create folders for each dirname token, then symlink for basename */
> while ((tok = strsep(&p, "/")) && *tok) {
>
> /* last (basename) token? If so, add symlink here */
> if (!p || !*p) {
> if (sysfs_create_link(&dir->kobj, target, tok)) {
> pr_err("fw_cfg: can't create symlink %s "
> "of %s\n", tok, name);
> }
> break;
> }
>
> /* does the current dir contain an item named after tok ? */
> ko = my_kset_find_obj(dir, tok);
> if (ko) {
> /* drop reference added by kset_find_obj */
> kobject_put(ko);
>
> /* ko MUST be a kset - we're about to use it as one ! */
> if (ko->ktype != dir->kobj.ktype) {
> pr_err("fw_cfg: non-folder token %s already "
> "exists while creating %s\n", tok, name);
> break;
> }
>
> /* descend into already existing subdirectory */
> dir = to_kset(ko);
> } else {
> /* create new subdirectory kset */
> subdir = kzalloc(sizeof(struct kset), GFP_KERNEL);
> if (!subdir) {
> pr_err("fw_cfg: alloc error creating subdir %s "
> "of %s\n", tok, name);
> break;
> }
> subdir->kobj.kset = dir;
> subdir->kobj.ktype = dir->kobj.ktype;
> if (kobject_set_name(&subdir->kobj, "%s", tok)) {
> kfree(subdir);
> pr_err("fw_cfg: set_name failed on subdir %s "
> "of %s\n", tok, name);
> break;
> }
> if (kset_register(subdir)) {
> kfree(subdir);
> pr_err("fw_cfg: register failed on subdir %s "
> "of %s\n", tok, name);
> break;
> }
>
> /* descend into newly created subdirectory */
> dir = subdir;
> }
> }
>
> /* we're done with cloned copy of name */
> kfree(name_copy);
> }
>
> /* recursively unregister fw_cfg/by_name/ kset directory tree */
> static void fw_cfg_kset_unregister_recursive(struct kset *kset)
> {
> struct kobject *k, *next;
>
> list_for_each_entry_safe(k, next, &kset->list, entry)
> /* all set members are ksets too, but check just in case... */
> if (k->ktype == kset->kobj.ktype)
> fw_cfg_kset_unregister_recursive(to_kset(k));
>
> /* symlinks are cleanly and automatically removed with the directory */
> kset_unregister(kset);
> }
>
> /* kobjects & kset representing top-level, by_select, and by_name folders */
> static struct kobject *fw_cfg_top_ko;
> static struct kobject *fw_cfg_sel_ko;
> static struct kset *fw_cfg_fname_kset;
>
> /* callback function to register an individual fw_cfg file */
> static int __init fw_cfg_register_file(const struct fw_cfg_file *f)
> {
> int err;
> struct fw_cfg_sysfs_entry *entry;
>
> /* allocate new entry */
> entry = kzalloc(sizeof(*entry), GFP_KERNEL);
> if (!entry)
> return -ENOMEM;
>
> /* set file entry information */
> entry->f.size = be32_to_cpu(f->size);
> entry->f.select = be16_to_cpu(f->select);
> strcpy(entry->f.name, f->name);
>
> /* register entry under "/sys/firmware/fw_cfg/by_select/" */
> err = kobject_init_and_add(&entry->kobj, &fw_cfg_sysfs_entry_ktype,
> fw_cfg_sel_ko, "%d", entry->f.select);
> if (err)
> goto err_register;
>
> /* add raw binary content access */
> err = sysfs_create_bin_file(&entry->kobj, &fw_cfg_sysfs_attr_raw);
> if (err)
> goto err_add_raw;
>
> /* try adding "/sys/firmware/fw_cfg/by_name/" symlink (best-effort) */
> fw_cfg_build_symlink(fw_cfg_fname_kset, &entry->kobj, entry->f.name);
>
> /* success, add entry to global cache */
> fw_cfg_sysfs_cache_enlist(entry);
> return 0;
>
> err_add_raw:
> kobject_del(&entry->kobj);
> err_register:
> kfree(entry);
> return err;
> }
>
> /* unregister top-level or by_select folder */
> static inline void fw_cfg_kobj_cleanup(struct kobject *kobj)
> {
> kobject_del(kobj);
> kobject_put(kobj);
> }
>
> static int __init fw_cfg_sysfs_init(void)
> {
> int err;
>
> /* probe for the fw_cfg "hardware" */
> err = fw_cfg_io_probe();
> if (err)
> return err;
>
> /* create sysfs toplevel, by_select, and by_name folders */
> err = -ENOMEM;
> fw_cfg_top_ko = kobject_create_and_add("fw_cfg", firmware_kobj);
> if (!fw_cfg_top_ko)
> goto err_sysfs_top;
> fw_cfg_sel_ko = kobject_create_and_add("by_select", fw_cfg_top_ko);
> if (!fw_cfg_sel_ko)
> goto err_sysfs_sel;
> fw_cfg_fname_kset = kset_create_and_add("by_name", NULL, fw_cfg_top_ko);
> if (!fw_cfg_fname_kset)
> goto err_sysfs_name;
>
> /* process fw_cfg file directory entry, registering each file */
> err = fw_cfg_scan_dir(fw_cfg_register_file);
> if (err)
> goto err_scan;
>
> /* success */
> pr_debug("fw_cfg: loaded.\n");
> return 0;
>
> err_scan:
> fw_cfg_sysfs_cache_cleanup();
> fw_cfg_kset_unregister_recursive(fw_cfg_fname_kset);
> err_sysfs_name:
> fw_cfg_kobj_cleanup(fw_cfg_sel_ko);
> err_sysfs_sel:
> fw_cfg_kobj_cleanup(fw_cfg_top_ko);
> err_sysfs_top:
> fw_cfg_io_cleanup();
> return err;
> }
>
> static void __exit fw_cfg_sysfs_exit(void)
> {
> pr_debug("fw_cfg: unloading.\n");
> fw_cfg_sysfs_cache_cleanup();
> fw_cfg_kset_unregister_recursive(fw_cfg_fname_kset);
> fw_cfg_kobj_cleanup(fw_cfg_sel_ko);
> fw_cfg_kobj_cleanup(fw_cfg_top_ko);
> fw_cfg_io_cleanup();
> }
>
> module_init(fw_cfg_sysfs_init);
> module_exit(fw_cfg_sysfs_exit);
> MODULE_AUTHOR("Gabriel L. Somlo <so...@cmu.edu>");
> MODULE_DESCRIPTION("QEMU fw_cfg sysfs support");
> MODULE_LICENSE("GPL");
>
