* [PATCH v4 1/4] firmware: introduce sysfs driver for QEMU's fw_cfg device
2015-11-14 3:03 [PATCH v4 0/4] SysFS driver for QEMU fw_cfg device Gabriel L. Somlo
@ 2015-11-14 3:03 ` Gabriel L. Somlo
2015-11-14 3:03 ` [PATCH v4 2/4] kobject: export kset_find_obj() for module use Gabriel L. Somlo
` (2 subsequent siblings)
3 siblings, 0 replies; 12+ messages in thread
From: Gabriel L. Somlo @ 2015-11-14 3:03 UTC (permalink / raw)
To: gregkh, robh+dt, pawel.moll, mark.rutland, ijc+devicetree, galak,
arnd, lersek, ralf, rmk+kernel, eric, hanjun.guo, zajec5,
sudeep.holla, agross, linux-api, linux-kernel, devicetree
Cc: peter.maydell, matt.fleming, mst, jordan.l.justen, kernelnewbies,
qemu-devel, leif.lindholm, luto, ard.biesheuvel, kraxel, stefanha,
pbonzini
From: Gabriel Somlo <somlo@cmu.edu>
Make fw_cfg entries of type "file" available via sysfs. Entries
are listed under /sys/firmware/qemu_fw_cfg/by_key, in folders
named after each entry's selector key. Filename, selector value,
and size read-only attributes are included for each entry. Also,
a "raw" attribute allows retrieval of the full binary content of
each entry.
This patch also provides a documentation file outlining the
guest-side "hardware" interface exposed by the QEMU fw_cfg device.
The fw_cfg device can be instantiated automatically from ACPI or
the Device Tree, or manually by using a kernel module (or command
line) parameter, with a syntax outlined in the documentation file.
Signed-off-by: Gabriel Somlo <somlo@cmu.edu>
---
.../ABI/testing/sysfs-firmware-qemu_fw_cfg | 198 +++++++
drivers/firmware/Kconfig | 19 +
drivers/firmware/Makefile | 1 +
drivers/firmware/qemu_fw_cfg.c | 611 +++++++++++++++++++++
4 files changed, 829 insertions(+)
create mode 100644 Documentation/ABI/testing/sysfs-firmware-qemu_fw_cfg
create mode 100644 drivers/firmware/qemu_fw_cfg.c
diff --git a/Documentation/ABI/testing/sysfs-firmware-qemu_fw_cfg b/Documentation/ABI/testing/sysfs-firmware-qemu_fw_cfg
new file mode 100644
index 0000000..b908b6d
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-firmware-qemu_fw_cfg
@@ -0,0 +1,198 @@
+What: /sys/firmware/qemu_fw_cfg/
+Date: August 2015
+Contact: Gabriel Somlo <somlo@cmu.edu>
+Description:
+ Several different architectures supported by QEMU (x86, arm,
+ sun4*, ppc/mac) are provisioned with a firmware configuration
+ (fw_cfg) device, originally intended as a way for the host to
+ provide configuration data to the guest firmware. Starting
+ with QEMU v2.4, arbitrary fw_cfg file entries may be specified
+ by the user on the command line, which makes fw_cfg additionally
+ useful as an out-of-band, asynchronous mechanism for providing
+ configuration data to the guest userspace.
+
+ === Guest-side Hardware Interface ===
+
+ The fw_cfg device is available to guest VMs as a register pair
+ (control and data), accessible as either a IO ports or as MMIO
+ addresses, depending on the architecture.
+
+ --- Control Register ---
+
+ Width: 16-bit
+ Access: Write-Only
+ Endianness: LE (if IOport) or BE (if MMIO)
+
+ A write to the control register selects the index for one of
+ the firmware configuration items (or "blobs") available on the
+ fw_cfg device, which can subsequently be read from the data
+ register.
+
+ Each time the control register is written, an data offset
+ internal to the fw_cfg device will be set to zero. This data
+ offset impacts which portion of the selected fw_cfg blob is
+ accessed by reading the data register, as explained below.
+
+ --- Data Register ---
+
+ Width: 8-bit (if IOport), or 8/16/32/64-bit (if MMIO)
+ Access: Read-Only
+ Endianness: string preserving
+
+ The data register allows access to an array of bytes which
+ represent the fw_cfg blob last selected by a write to the
+ control register.
+
+ Immediately following a write to the control register, the data
+ offset will be set to zero. Each successful read access to the
+ data register will increment the data offset by the appropriate
+ access width.
+
+ Each fw_cfg blob has a maximum associated data length. Once the
+ data offset exceeds this maximum length, any subsequent reads
+ via the data register will return 0x00.
+
+ An N-byte wide read of the data register will return the next
+ available N bytes of the selected fw_cfg blob, as a substring,
+ in increasing address order, similar to memcpy(), zero-padded
+ if necessary should the maximum data length of the selected
+ item be reached, as described above.
+
+ --- Per-arch Register Details ---
+
+ -------------------------------------------------------------
+ arch access base ctrl ctrl data max.
+ mode address offset endian offset data
+ (bytes) (bytes)
+ -------------------------------------------------------------
+ x86 IOport 0x510 0 LE 1 1
+ arm MMIO 0x9020000 8 BE 0 8
+ sun4u IOport 0x510 0 LE 1 1
+ sun4m MMIO 0xd00000510 0 BE 2 1
+ ppc/mac MMIO 0xf0000510 0 BE 2 1
+ -------------------------------------------------------------
+
+ NOTE 1. On platforms where the fw_cfg registers are exposed as
+ IO ports, the data port number will always be one greater than
+ the port number of the control register. I.e., the two ports
+ are overlapping, and can not be mapped separately.
+
+ NOTE 2. QEMU publishes the base and size of the register set
+ in ACPI (as _HID "QEMU0002", on x86 and select aarch64 subsets)
+ and in the Device Tree (as compatible = "qemu,fw-cfg-mmio", on
+ arm guests).
+
+ NOTE 3. On architectures where automatic detection of fw_cfg
+ "hardware" (via ACPI or DT) is not supported, the guest side
+ kernel driver allows configuration using a command line
+ parameter, with the following syntax:
+
+ [fw_cfg.]ioport=<size>@<base>[:<ctrl_off>:<data_off>]
+ or
+ [fw_cfg.]mmio=<size>@<base>[:<ctrl_off>:<data_off>]
+
+ where:
+ <size> : size of ioport or mmio range
+ <base> : physical base address of ioport or mmio range
+ and, optionally:
+ <ctrl_off> : offset of control register
+ <data_off> : offset of data register
+
+ Since neither ACPI nor DT provide specific details on register
+ offsets within the overall specified register set range, using
+ <ctrl_off> and <data_off> allows the arm-specific default MMIO
+ offset values (8 and 0, respectively) to be overridden for e.g.
+ sun4m and ppc/mac, where the ofsets should be 0 and 2,
+ respectively. Using ppc/mac as an example:
+
+ fw_cfg.mmio=3@0xf0000510:0:2
+
+ === Firmware Configuration Items of Interest ===
+
+ Originally, the index key, size, and formatting of blobs in
+ fw_cfg was hard coded by mutual agreement between QEMU on the
+ host side, and the guest-side firmware. Later on, a file
+ transfer interface was added: by reading a special blob, the
+ fw_cfg consumer can retrieve a list of records containing the
+ name, selector key, and size of further fw_cfg blobs made
+ available by the host. Below we describe three fw_cfg blobs
+ of interest to the sysfs driver.
+
+ --- Signature (Key 0x0000, FW_CFG_SIGNATURE) ---
+
+ The presence of the fw_cfg device can be verified by selecting
+ the signature blob by writing 0x0000 to the control register,
+ and reading four bytes from the data register. If the fw_cfg
+ device is present, the four bytes read will match the ASCII
+ characters "QEMU".
+
+ --- Revision (Key 0x0001, FW_CFG_ID) ---
+
+ A 32-bit little-endian unsigned integer, this item is used as
+ an interface revision number.
+
+ --- File Directory (Key 0x0019, FW_CFG_FILE_DIR) ---
+
+ Any fw_cfg blobs stored at key 0x0020 FW_CFG_FILE_FIRST() or
+ higher will have an associated entry in this "directory" blob,
+ which facilitates the discovery of available items by software
+ (e.g. BIOS) running on the guest. The format of the directory
+ blob is shown below.
+
+ NOTE: All integers are stored in big-endian format!
+
+ /* the entire file directory "blob" */
+ struct FWCfgFiles {
+ u32 count; /* total number of entries */
+ struct FWCfgFile f[]; /* entry array, see below */
+ };
+
+ /* an individual directory entry, 64 bytes total */
+ struct FWCfgFile {
+ u32 size; /* size of referenced blob */
+ u16 select; /* selector key for referenced blob */
+ u16 reserved;
+ char name[56]; /* blob name, nul-terminated ASCII */
+ };
+
+ === SysFS fw_cfg Interface ===
+
+ The fw_cfg sysfs interface described in this document is only
+ intended to display discoverable blobs (i.e., those registered
+ with the file directory), as there is no way to determine the
+ presence or size of "legacy" blobs (with selector keys between
+ 0x0002 and 0x0018) programmatically.
+
+ All fw_cfg information is shown under:
+
+ /sys/firmware/qemu_fw_cfg/
+
+ The only legacy blob displayed is the fw_cfg device revision:
+
+ /sys/firmware/qemu_fw_cfg/rev
+
+ --- Discoverable fw_cfg blobs by selector key ---
+
+ All discoverable blobs listed in the fw_cfg file directory are
+ displayed as entries named after their unique selector key
+ value, e.g.:
+
+ /sys/firmware/qemu_fw_cfg/by_key/32
+ /sys/firmware/qemu_fw_cfg/by_key/33
+ /sys/firmware/qemu_fw_cfg/by_key/34
+ ...
+
+ Each such fw_cfg sysfs entry has the following values exported
+ as attributes:
+
+ name : The 56-byte nul-terminated ASCII string used as the
+ blob's 'file name' in the fw_cfg directory.
+ size : The length of the blob, as given in the fw_cfg
+ directory.
+ key : The value of the blob's selector key as given in the
+ fw_cfg directory. This value is the same as used in
+ the parent directory name.
+ raw : The raw bytes of the blob, obtained by selecting the
+ entry via the control register, and reading a number
+ of bytes equal to the blob size from the data
+ register.
diff --git a/drivers/firmware/Kconfig b/drivers/firmware/Kconfig
index cf478fe..3cf920a 100644
--- a/drivers/firmware/Kconfig
+++ b/drivers/firmware/Kconfig
@@ -161,6 +161,25 @@ config RASPBERRYPI_FIRMWARE
This option enables support for communicating with the firmware on the
Raspberry Pi.
+config FW_CFG_SYSFS
+ tristate "QEMU fw_cfg device support in sysfs"
+ depends on SYSFS
+ default n
+ help
+ Say Y or M here to enable the exporting of the QEMU firmware
+ configuration (fw_cfg) file entries via sysfs. Entries are
+ found under /sys/firmware/fw_cfg when this option is enabled
+ and loaded.
+
+config FW_CFG_SYSFS_CMDLINE
+ bool "QEMU fw_cfg device parameter parsing"
+ depends on FW_CFG_SYSFS
+ help
+ Allow the qemu_fw_cfg device to be initialized via the kernel
+ command line or using a module parameter.
+ WARNING: Using incorrect parameters (base address in particular)
+ may crash your system.
+
config QCOM_SCM
bool
depends on ARM || ARM64
diff --git a/drivers/firmware/Makefile b/drivers/firmware/Makefile
index 48dd417..474bada 100644
--- a/drivers/firmware/Makefile
+++ b/drivers/firmware/Makefile
@@ -14,6 +14,7 @@ obj-$(CONFIG_ISCSI_IBFT_FIND) += iscsi_ibft_find.o
obj-$(CONFIG_ISCSI_IBFT) += iscsi_ibft.o
obj-$(CONFIG_FIRMWARE_MEMMAP) += memmap.o
obj-$(CONFIG_RASPBERRYPI_FIRMWARE) += raspberrypi.o
+obj-$(CONFIG_FW_CFG_SYSFS) += qemu_fw_cfg.o
obj-$(CONFIG_QCOM_SCM) += qcom_scm.o
obj-$(CONFIG_QCOM_SCM_64) += qcom_scm-64.o
obj-$(CONFIG_QCOM_SCM_32) += qcom_scm-32.o
diff --git a/drivers/firmware/qemu_fw_cfg.c b/drivers/firmware/qemu_fw_cfg.c
new file mode 100644
index 0000000..618304a
--- /dev/null
+++ b/drivers/firmware/qemu_fw_cfg.c
@@ -0,0 +1,611 @@
+/*
+ * drivers/firmware/qemu_fw_cfg.c
+ *
+ * Copyright 2015 Carnegie Mellon University
+ *
+ * Expose entries from QEMU's firmware configuration (fw_cfg) device in
+ * sysfs (read-only, under "/sys/firmware/qemu_fw_cfg/...").
+ *
+ * The fw_cfg device may be instantiated via either an ACPI node (on x86
+ * and select subsets of aarch64), a Device Tree node (on arm), or using
+ * a kernel module (or command line) parameter with the following syntax:
+ *
+ * [fw_cfg.]ioport=<size>@<base>[:<ctrl_off>:<data_off>]
+ * or
+ * [fw_cfg.]mmio=<size>@<base>[:<ctrl_off>:<data_off>]
+ *
+ * where:
+ * <size> := size of ioport or mmio range
+ * <base> := physical base address of ioport or mmio range
+ * <ctrl_off> := (optional) offset of control register
+ * <data_off> := (optional) offset of data register
+ *
+ * e.g.:
+ * fw_cfg.ioport=2@0x510:0:1 (the default on x86)
+ * or
+ * fw_cfg.mmio=0xA@0x9020000:8:0 (the default on arm)
+ */
+
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/acpi.h>
+#include <linux/slab.h>
+#include <linux/io.h>
+#include <linux/ioport.h>
+
+MODULE_AUTHOR("Gabriel L. Somlo <somlo@cmu.edu>");
+MODULE_DESCRIPTION("QEMU fw_cfg sysfs support");
+MODULE_LICENSE("GPL");
+
+/* selector key values for "well-known" fw_cfg entries */
+#define FW_CFG_SIGNATURE 0x00
+#define FW_CFG_ID 0x01
+#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 {
+ u32 size;
+ u16 select;
+ u16 reserved;
+ char name[FW_CFG_MAX_FILE_PATH];
+};
+
+/* fw_cfg device i/o register addresses */
+static bool fw_cfg_is_mmio;
+static phys_addr_t fw_cfg_p_base;
+static resource_size_t fw_cfg_p_size;
+static void __iomem *fw_cfg_dev_base;
+static void __iomem *fw_cfg_reg_ctrl;
+static void __iomem *fw_cfg_reg_data;
+
+/* atomic access to fw_cfg device (potentially slow i/o, so using mutex) */
+static DEFINE_MUTEX(fw_cfg_dev_lock);
+
+/* pick appropriate endianness for selector key */
+static inline u16 fw_cfg_sel_endianness(u16 key)
+{
+ return fw_cfg_is_mmio ? cpu_to_be16(key) : cpu_to_le16(key);
+}
+
+/* read chunk of given fw_cfg blob (caller responsible for sanity-check) */
+static inline void fw_cfg_read_blob(u16 key,
+ void *buf, loff_t pos, size_t count)
+{
+ mutex_lock(&fw_cfg_dev_lock);
+ iowrite16(fw_cfg_sel_endianness(key), fw_cfg_reg_ctrl);
+ while (pos-- > 0)
+ ioread8(fw_cfg_reg_data);
+ ioread8_rep(fw_cfg_reg_data, buf, count);
+ mutex_unlock(&fw_cfg_dev_lock);
+}
+
+/* clean up fw_cfg device i/o */
+static void fw_cfg_io_cleanup(void)
+{
+ if (fw_cfg_is_mmio) {
+ iounmap(fw_cfg_dev_base);
+ release_mem_region(fw_cfg_p_base, fw_cfg_p_size);
+ } else {
+ ioport_unmap(fw_cfg_dev_base);
+ release_region(fw_cfg_p_base, fw_cfg_p_size);
+ }
+}
+
+/* initialize fw_cfg device i/o from platform data */
+static int fw_cfg_do_platform_probe(struct platform_device *pdev)
+{
+ char sig[FW_CFG_SIG_SIZE];
+ struct resource *range, *ctrl, *data;
+
+ /* acquire i/o range details */
+ fw_cfg_is_mmio = false;
+ range = platform_get_resource(pdev, IORESOURCE_IO, 0);
+ if (!range) {
+ fw_cfg_is_mmio = true;
+ range = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ if (!range)
+ return -EINVAL;
+ }
+ fw_cfg_p_base = range->start;
+ fw_cfg_p_size = resource_size(range);
+
+ if (fw_cfg_is_mmio) {
+ if (!request_mem_region(fw_cfg_p_base,
+ fw_cfg_p_size, "fw_cfg_mem"))
+ return -EBUSY;
+ fw_cfg_dev_base = ioremap(fw_cfg_p_base, fw_cfg_p_size);
+ if (!fw_cfg_dev_base) {
+ release_mem_region(fw_cfg_p_base, fw_cfg_p_size);
+ return -EFAULT;
+ }
+ /* set register addresses (using arm/mmio offsets) */
+ fw_cfg_reg_ctrl = fw_cfg_dev_base + 0x08;
+ fw_cfg_reg_data = fw_cfg_dev_base + 0x00;
+ } else {
+ if (!request_region(fw_cfg_p_base,
+ fw_cfg_p_size, "fw_cfg_io"))
+ return -EBUSY;
+ fw_cfg_dev_base = ioport_map(fw_cfg_p_base, fw_cfg_p_size);
+ if (!fw_cfg_dev_base) {
+ release_region(fw_cfg_p_base, fw_cfg_p_size);
+ return -EFAULT;
+ }
+ /* set register addresses (using pc/i386/ioport offsets) */
+ fw_cfg_reg_ctrl = fw_cfg_dev_base + 0x00;
+ fw_cfg_reg_data = fw_cfg_dev_base + 0x01;
+ }
+
+ /* were custom register offsets provided (e.g. on the command line)? */
+ ctrl = platform_get_resource_byname(pdev, IORESOURCE_REG, "ctrl");
+ data = platform_get_resource_byname(pdev, IORESOURCE_REG, "data");
+ if (ctrl && data) {
+ fw_cfg_reg_ctrl = fw_cfg_dev_base + ctrl->start;
+ fw_cfg_reg_data = fw_cfg_dev_base + data->start;
+ }
+
+ /* 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) {
+ fw_cfg_io_cleanup();
+ return -ENODEV;
+ }
+
+ return 0;
+}
+
+/* fw_cfg revision attribute, in /sys/firmware/qemu_fw_cfg top-level dir. */
+static u32 fw_cfg_rev;
+
+static ssize_t fw_cfg_showrev(struct kobject *k, struct attribute *a, char *buf)
+{
+ return sprintf(buf, "%u\n", fw_cfg_rev);
+}
+
+static const struct {
+ struct attribute attr;
+ ssize_t (*show)(struct kobject *k, struct attribute *a, char *buf);
+} fw_cfg_rev_attr = {
+ .attr = { .name = "rev", .mode = S_IRUSR },
+ .show = fw_cfg_showrev,
+};
+
+/* 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 = S_IRUSR }, \
+ .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, "%u\n", e->f.size);
+}
+
+static ssize_t fw_cfg_sysfs_show_key(struct fw_cfg_sysfs_entry *e, char *buf)
+{
+ return sprintf(buf, "%u\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(key);
+static FW_CFG_SYSFS_ATTR(name);
+
+static struct attribute *fw_cfg_sysfs_entry_attrs[] = {
+ &fw_cfg_sysfs_attr_size.attr,
+ &fw_cfg_sysfs_attr_key.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);
+
+ 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 (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 = S_IRUSR },
+ .read = fw_cfg_sysfs_read_raw,
+};
+
+/* kobjects representing top-level and by_key folders */
+static struct kobject *fw_cfg_top_ko;
+static struct kobject *fw_cfg_sel_ko;
+
+/* register an individual fw_cfg file */
+static int 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 */
+ memcpy(&entry->f, f, sizeof(struct fw_cfg_file));
+
+ /* register entry under "/sys/firmware/qemu_fw_cfg/by_key/" */
+ 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;
+
+ /* 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;
+}
+
+/* iterate over all fw_cfg directory entries, registering each one */
+static int fw_cfg_register_dir_entries(void)
+{
+ int ret = 0;
+ u32 count, i;
+ struct fw_cfg_file *dir;
+ size_t dir_size;
+
+ fw_cfg_read_blob(FW_CFG_FILE_DIR, &count, 0, sizeof(count));
+ count = be32_to_cpu(count);
+ dir_size = count * sizeof(struct fw_cfg_file);
+
+ dir = kmalloc(dir_size, GFP_KERNEL);
+ if (!dir)
+ return -ENOMEM;
+
+ fw_cfg_read_blob(FW_CFG_FILE_DIR, dir, sizeof(count), dir_size);
+
+ for (i = 0; i < count; i++) {
+ dir[i].size = be32_to_cpu(dir[i].size);
+ dir[i].select = be16_to_cpu(dir[i].select);
+ ret = fw_cfg_register_file(&dir[i]);
+ if (ret)
+ break;
+ }
+
+ kfree(dir);
+ return ret;
+}
+
+/* unregister top-level or by_key folder */
+static inline void fw_cfg_kobj_cleanup(struct kobject *kobj)
+{
+ kobject_del(kobj);
+ kobject_put(kobj);
+}
+
+static int fw_cfg_sysfs_probe(struct platform_device *pdev)
+{
+ int err;
+
+ /* NOTE: If we supported multiple fw_cfg devices, we'd first create
+ * a subdirectory named after e.g. pdev->id, then hang per-device
+ * by_key subdirectories underneath it. However, only
+ * one fw_cfg device exist system-wide, so if one was already found
+ * earlier, we might as well stop here.
+ */
+ if (fw_cfg_sel_ko)
+ return -EBUSY;
+
+ /* create by_key subdirectory of /sys/firmware/qemu_fw_cfg/ */
+ err = -ENOMEM;
+ fw_cfg_sel_ko = kobject_create_and_add("by_key", fw_cfg_top_ko);
+ if (!fw_cfg_sel_ko)
+ goto err_sel;
+
+ /* initialize fw_cfg device i/o from platform data */
+ err = fw_cfg_do_platform_probe(pdev);
+ if (err)
+ goto err_probe;
+
+ /* get revision number, add matching top-level attribute */
+ fw_cfg_read_blob(FW_CFG_ID, &fw_cfg_rev, 0, sizeof(fw_cfg_rev));
+ fw_cfg_rev = le32_to_cpu(fw_cfg_rev);
+ err = sysfs_create_file(fw_cfg_top_ko, &fw_cfg_rev_attr.attr);
+ if (err)
+ goto err_rev;
+
+ /* process fw_cfg file directory entry, registering each file */
+ err = fw_cfg_register_dir_entries();
+ if (err)
+ goto err_dir;
+
+ /* success */
+ pr_debug("fw_cfg: loaded.\n");
+ return 0;
+
+err_dir:
+ fw_cfg_sysfs_cache_cleanup();
+ sysfs_remove_file(fw_cfg_top_ko, &fw_cfg_rev_attr.attr);
+err_rev:
+ fw_cfg_io_cleanup();
+err_probe:
+ fw_cfg_kobj_cleanup(fw_cfg_sel_ko);
+err_sel:
+ return err;
+}
+
+static int fw_cfg_sysfs_remove(struct platform_device *pdev)
+{
+ pr_debug("fw_cfg: unloading.\n");
+ fw_cfg_sysfs_cache_cleanup();
+ fw_cfg_kobj_cleanup(fw_cfg_sel_ko);
+ fw_cfg_io_cleanup();
+ return 0;
+}
+
+static const struct of_device_id fw_cfg_sysfs_mmio_match[] = {
+ { .compatible = "qemu,fw-cfg-mmio", },
+ {},
+};
+MODULE_DEVICE_TABLE(of, fw_cfg_sysfs_mmio_match);
+
+#ifdef CONFIG_ACPI
+static const struct acpi_device_id fw_cfg_sysfs_acpi_match[] = {
+ { "QEMU0002", },
+ {},
+};
+MODULE_DEVICE_TABLE(acpi, fw_cfg_sysfs_acpi_match);
+#endif
+
+static struct platform_driver fw_cfg_sysfs_driver = {
+ .probe = fw_cfg_sysfs_probe,
+ .remove = fw_cfg_sysfs_remove,
+ .driver = {
+ .name = "fw_cfg",
+ .of_match_table = fw_cfg_sysfs_mmio_match,
+ .acpi_match_table = ACPI_PTR(fw_cfg_sysfs_acpi_match),
+ },
+};
+
+#ifdef CONFIG_FW_CFG_SYSFS_CMDLINE
+
+static struct platform_device *fw_cfg_cmdline_dev;
+
+static int fw_cfg_cmdline_set(const char *arg, const struct kernel_param *kp)
+{
+ struct resource res[3] = {};
+ char *str;
+ phys_addr_t base;
+ resource_size_t size, ctrl_off, data_off;
+ int processed, consumed = 0;
+
+ /* only one fw_cfg device can exist system-wide, so if one
+ * was processed on the command line already, we might as
+ * well stop here.
+ */
+ if (fw_cfg_cmdline_dev) {
+ /* avoid leaking previously registered device */
+ platform_device_unregister(fw_cfg_cmdline_dev);
+ return -EINVAL;
+ }
+
+ /* consume "<size>" portion of command line argument */
+ size = memparse(arg, &str);
+
+ /* get "@<base>[:<ctrl_off>:<data_off>]" chunks */
+ processed = sscanf(str, "@%lli%n:%lli:%lli%n",
+ &base, &consumed,
+ &ctrl_off, &data_off, &consumed);
+
+ /* sscanf() must process precisely 1 or 3 chunks:
+ * <base> is mandatory, optionally followed by <ctrl_off>
+ * and <data_off>;
+ * there must be no extra characters after the last chunk,
+ * so str[consumed] must be '\0'.
+ */
+ if (str[consumed] ||
+ (processed != 1 && processed != 3))
+ return -EINVAL;
+
+ res[0].start = base;
+ res[0].end = base + size - 1;
+ res[0].flags = !strcmp(kp->name, "mmio") ? IORESOURCE_MEM :
+ IORESOURCE_IO;
+
+ /* insert register offsets, if provided */
+ if (processed > 1) {
+ res[1].name = "ctrl";
+ res[1].start = ctrl_off;
+ res[1].flags = IORESOURCE_REG;
+ res[2].name = "data";
+ res[2].start = data_off;
+ res[2].flags = IORESOURCE_REG;
+ }
+
+ /* "processed" happens to nicely match the number of resources
+ * we need to pass in to this platform device.
+ */
+ fw_cfg_cmdline_dev = platform_device_register_simple("fw_cfg",
+ PLATFORM_DEVID_NONE, res, processed);
+ if (IS_ERR(fw_cfg_cmdline_dev))
+ return PTR_ERR(fw_cfg_cmdline_dev);
+
+ return 0;
+}
+
+static int fw_cfg_cmdline_get(char *buf, const struct kernel_param *kp)
+{
+ /* stay silent if device was not configured via the command
+ * line, or if the parameter name (ioport/mmio) doesn't match
+ * the device setting
+ */
+ if (!fw_cfg_cmdline_dev ||
+ (!strcmp(kp->name, "mmio") ^
+ (fw_cfg_cmdline_dev->resource[0].flags == IORESOURCE_MEM)))
+ return 0;
+
+ switch (fw_cfg_cmdline_dev->num_resources) {
+ case 1:
+ return snprintf(buf, PAGE_SIZE, "0x%llx@0x%llx",
+ resource_size(&fw_cfg_cmdline_dev->resource[0]),
+ fw_cfg_cmdline_dev->resource[0].start);
+ case 3:
+ return snprintf(buf, PAGE_SIZE, "0x%llx@0x%llx:%llu:%llu",
+ resource_size(&fw_cfg_cmdline_dev->resource[0]),
+ fw_cfg_cmdline_dev->resource[0].start,
+ fw_cfg_cmdline_dev->resource[1].start,
+ fw_cfg_cmdline_dev->resource[2].start);
+ }
+
+ /* Should never get here */
+ WARN(1, "Unexpected number of resources: %d\n",
+ fw_cfg_cmdline_dev->num_resources);
+ return 0;
+}
+
+static const struct kernel_param_ops fw_cfg_cmdline_param_ops = {
+ .set = fw_cfg_cmdline_set,
+ .get = fw_cfg_cmdline_get,
+};
+
+device_param_cb(ioport, &fw_cfg_cmdline_param_ops, NULL, S_IRUSR);
+device_param_cb(mmio, &fw_cfg_cmdline_param_ops, NULL, S_IRUSR);
+
+#endif /* CONFIG_FW_CFG_SYSFS_CMDLINE */
+
+static int __init fw_cfg_sysfs_init(void)
+{
+ /* create /sys/firmware/qemu_fw_cfg/ top level directory */
+ fw_cfg_top_ko = kobject_create_and_add("qemu_fw_cfg", firmware_kobj);
+ if (!fw_cfg_top_ko)
+ return -ENOMEM;
+
+ return platform_driver_register(&fw_cfg_sysfs_driver);
+}
+
+static void __exit fw_cfg_sysfs_exit(void)
+{
+ platform_driver_unregister(&fw_cfg_sysfs_driver);
+
+#ifdef CONFIG_FW_CFG_SYSFS_CMDLINE
+ platform_device_unregister(fw_cfg_cmdline_dev);
+#endif
+
+ /* clean up /sys/firmware/qemu_fw_cfg/ */
+ fw_cfg_kobj_cleanup(fw_cfg_top_ko);
+}
+
+module_init(fw_cfg_sysfs_init);
+module_exit(fw_cfg_sysfs_exit);
--
2.4.3
^ permalink raw reply related [flat|nested] 12+ messages in thread* [PATCH v4 3/4] firmware: create directory hierarchy for sysfs fw_cfg entries
2015-11-14 3:03 [PATCH v4 0/4] SysFS driver for QEMU fw_cfg device Gabriel L. Somlo
2015-11-14 3:03 ` [PATCH v4 1/4] firmware: introduce sysfs driver for QEMU's " Gabriel L. Somlo
2015-11-14 3:03 ` [PATCH v4 2/4] kobject: export kset_find_obj() for module use Gabriel L. Somlo
@ 2015-11-14 3:03 ` Gabriel L. Somlo
2015-11-14 3:03 ` [PATCH v4 4/4] devicetree: update documentation for fw_cfg ARM bindings Gabriel L. Somlo
3 siblings, 0 replies; 12+ messages in thread
From: Gabriel L. Somlo @ 2015-11-14 3:03 UTC (permalink / raw)
To: gregkh, robh+dt, pawel.moll, mark.rutland, ijc+devicetree, galak,
arnd, lersek, ralf, rmk+kernel, eric, hanjun.guo, zajec5,
sudeep.holla, agross, linux-api, linux-kernel, devicetree
Cc: peter.maydell, matt.fleming, mst, jordan.l.justen, kernelnewbies,
qemu-devel, leif.lindholm, luto, ard.biesheuvel, kraxel, stefanha,
pbonzini
From: Gabriel Somlo <somlo@cmu.edu>
Each fw_cfg entry of type "file" has an associated 56-char,
nul-terminated ASCII string which represents its name. While
the fw_cfg device doesn't itself impose any specific naming
convention, QEMU developers have traditionally used path name
semantics (i.e. "etc/acpi/rsdp") to descriptively name the
various fw_cfg "blobs" passed into the guest.
This patch attempts, on a best effort basis, to create a
directory hierarchy representing the content of fw_cfg file
names, under /sys/firmware/qemu_fw_cfg/by_name.
Upon successful creation of all directories representing the
"dirname" portion of a fw_cfg file, a symlink will be created
to represent the "basename", pointing at the appropriate
/sys/firmware/qemu_fw_cfg/by_key entry. If a file name is not
suitable for this procedure (e.g., if its basename or dirname
components collide with an already existing dirname component
or basename, respectively) the corresponding fw_cfg blob is
skipped and will remain available in sysfs only by its selector
key value.
Signed-off-by: Gabriel Somlo <somlo@cmu.edu>
Cc: Andy Lutomirski <luto@amacapital.net>
---
.../ABI/testing/sysfs-firmware-qemu_fw_cfg | 42 ++++++++
drivers/firmware/qemu_fw_cfg.c | 109 ++++++++++++++++++++-
2 files changed, 148 insertions(+), 3 deletions(-)
diff --git a/Documentation/ABI/testing/sysfs-firmware-qemu_fw_cfg b/Documentation/ABI/testing/sysfs-firmware-qemu_fw_cfg
index b908b6d..a346ee0 100644
--- a/Documentation/ABI/testing/sysfs-firmware-qemu_fw_cfg
+++ b/Documentation/ABI/testing/sysfs-firmware-qemu_fw_cfg
@@ -196,3 +196,45 @@ Description:
entry via the control register, and reading a number
of bytes equal to the blob size from the data
register.
+
+ --- Listing fw_cfg blobs by file name ---
+
+ While the fw_cfg device does not impose any specific naming
+ convention on the blobs registered in the file directory,
+ QEMU developers have traditionally used path name semantics
+ to give each blob a descriptive name. For example:
+
+ "bootorder"
+ "genroms/kvmvapic.bin"
+ "etc/e820"
+ "etc/boot-fail-wait"
+ "etc/system-states"
+ "etc/table-loader"
+ "etc/acpi/rsdp"
+ "etc/acpi/tables"
+ "etc/smbios/smbios-tables"
+ "etc/smbios/smbios-anchor"
+ ...
+
+ In addition to the listing by unique selector key described
+ above, the fw_cfg sysfs driver also attempts to build a tree
+ of directories matching the path name components of fw_cfg
+ blob names, ending in symlinks to the by_key entry for each
+ "basename", as illustrated below (assume current directory is
+ /sys/firmware):
+
+ qemu_fw_cfg/by_name/bootorder -> ../by_key/38
+ qemu_fw_cfg/by_name/etc/e820 -> ../../by_key/35
+ qemu_fw_cfg/by_name/etc/acpi/rsdp -> ../../../by_key/41
+ ...
+
+ Construction of the directory tree and symlinks is done on a
+ "best-effort" basis, as there is no guarantee that components
+ of fw_cfg blob names are always "well behaved". I.e., there is
+ the possibility that a symlink (basename) will conflict with
+ a dirname component of another fw_cfg blob, in which case the
+ creation of the offending /sys/firmware/qemu_fw_cfg/by_name
+ entry will be skipped.
+
+ The authoritative list of entries will continue to be found
+ under the /sys/firmware/qemu_fw_cfg/by_key directory.
diff --git a/drivers/firmware/qemu_fw_cfg.c b/drivers/firmware/qemu_fw_cfg.c
index 618304a..9ac1ca7 100644
--- a/drivers/firmware/qemu_fw_cfg.c
+++ b/drivers/firmware/qemu_fw_cfg.c
@@ -318,9 +318,103 @@ static struct bin_attribute fw_cfg_sysfs_attr_raw = {
.read = fw_cfg_sysfs_read_raw,
};
-/* kobjects representing top-level and by_key folders */
+/*
+ * 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 int fw_cfg_build_symlink(struct kset *dir,
+ struct kobject *target, const char *name)
+{
+ int ret;
+ struct kset *subdir;
+ struct kobject *ko;
+ char *name_copy, *p, *tok;
+
+ if (!dir || !target || !name || !*name)
+ return -EINVAL;
+
+ /* clone a copy of name for parsing */
+ name_copy = p = kstrdup(name, GFP_KERNEL);
+ if (!name_copy)
+ return -ENOMEM;
+
+ /* 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) {
+ ret = sysfs_create_link(&dir->kobj, target, tok);
+ break;
+ }
+
+ /* does the current dir contain an item named after tok ? */
+ ko = 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) {
+ ret = -EINVAL;
+ break;
+ }
+
+ /* descend into already existing subdirectory */
+ dir = to_kset(ko);
+ } else {
+ /* create new subdirectory kset */
+ subdir = kzalloc(sizeof(struct kset), GFP_KERNEL);
+ if (!subdir) {
+ ret = -ENOMEM;
+ break;
+ }
+ subdir->kobj.kset = dir;
+ subdir->kobj.ktype = dir->kobj.ktype;
+ ret = kobject_set_name(&subdir->kobj, "%s", tok);
+ if (ret) {
+ kfree(subdir);
+ break;
+ }
+ ret = kset_register(subdir);
+ if (ret) {
+ kfree(subdir);
+ break;
+ }
+
+ /* descend into newly created subdirectory */
+ dir = subdir;
+ }
+ }
+
+ /* we're done with cloned copy of name */
+ kfree(name_copy);
+ return ret;
+}
+
+/* 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_key, 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;
/* register an individual fw_cfg file */
static int fw_cfg_register_file(const struct fw_cfg_file *f)
@@ -347,6 +441,9 @@ static int fw_cfg_register_file(const struct fw_cfg_file *f)
if (err)
goto err_add_raw;
+ /* try adding "/sys/firmware/qemu_fw_cfg/by_name/" symlink */
+ 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;
@@ -401,18 +498,21 @@ static int fw_cfg_sysfs_probe(struct platform_device *pdev)
/* NOTE: If we supported multiple fw_cfg devices, we'd first create
* a subdirectory named after e.g. pdev->id, then hang per-device
- * by_key subdirectories underneath it. However, only
+ * by_key (and by_name) subdirectories underneath it. However, only
* one fw_cfg device exist system-wide, so if one was already found
* earlier, we might as well stop here.
*/
if (fw_cfg_sel_ko)
return -EBUSY;
- /* create by_key subdirectory of /sys/firmware/qemu_fw_cfg/ */
+ /* create by_key and by_name subdirs of /sys/firmware/qemu_fw_cfg/ */
err = -ENOMEM;
fw_cfg_sel_ko = kobject_create_and_add("by_key", fw_cfg_top_ko);
if (!fw_cfg_sel_ko)
goto err_sel;
+ fw_cfg_fname_kset = kset_create_and_add("by_name", NULL, fw_cfg_top_ko);
+ if (!fw_cfg_fname_kset)
+ goto err_name;
/* initialize fw_cfg device i/o from platform data */
err = fw_cfg_do_platform_probe(pdev);
@@ -441,6 +541,8 @@ err_dir:
err_rev:
fw_cfg_io_cleanup();
err_probe:
+ fw_cfg_kset_unregister_recursive(fw_cfg_fname_kset);
+err_name:
fw_cfg_kobj_cleanup(fw_cfg_sel_ko);
err_sel:
return err;
@@ -450,6 +552,7 @@ static int fw_cfg_sysfs_remove(struct platform_device *pdev)
{
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_io_cleanup();
return 0;
--
2.4.3
^ permalink raw reply related [flat|nested] 12+ messages in thread