RE: [PATCH] efivars update

* RE: [PATCH] efivars update
@ 2003-08-30  0:16 Tolentino, Matthew E
  0 siblings, 0 replies; 6+ messages in thread
From: Tolentino, Matthew E @ 2003-08-30  0:16 UTC (permalink / raw)
  To: Matt Domsch; +Cc: linux-kernel, linux-ia64, Matt Tolentino

[-- Attachment #1: Type: text/plain, Size: 488 bytes --]

Matt,

> Move the unlock up above the status test, else you return while
> holding the lock on failure.

Ouch. Thanks...

> level on printk please.

Fixed.

> Might as well just force the deletion by setting Attributes=0 or
> DataSize=0 or both.  Less chance for userspace error.

Good idea.
 
> Please kill this chunk.  I shouldn't have had it there in the first 
> place. :-)
> 
> Looks great to me!  Thanks again.

Sure thing.  Updated patch attached....

matt

[-- Attachment #2: linux-2.6.0-test4-efivars2.patch --]
[-- Type: application/octet-stream, Size: 37980 bytes --]

diff -urN linux-2.6.0-test4/arch/ia64/defconfig linux-2.6.0-test4-all/arch/ia64/defconfig

--- linux-2.6.0-test4/arch/ia64/defconfig	2003-08-22 16:51:44.000000000 -0700
+++ linux-2.6.0-test4-all/arch/ia64/defconfig	2003-08-29 11:45:12.000000000 -0700
@@ -76,6 +76,7 @@
 CONFIG_COMPAT=y
 CONFIG_PERFMON=y
 CONFIG_IA64_PALINFO=y
+CONFIG_EFI=y
 CONFIG_EFI_VARS=y
 CONFIG_NR_CPUS=16
 CONFIG_BINFMT_ELF=y
diff -urN linux-2.6.0-test4/arch/ia64/Kconfig linux-2.6.0-test4-all/arch/ia64/Kconfig
--- linux-2.6.0-test4/arch/ia64/Kconfig	2003-08-22 17:00:49.000000000 -0700
+++ linux-2.6.0-test4-all/arch/ia64/Kconfig	2003-08-29 11:45:12.000000000 -0700
@@ -433,15 +433,7 @@
 	  To use this option, you have to ensure that the "/proc file system
 	  support" (CONFIG_PROC_FS) is enabled, too.
 
-config EFI_VARS
-	tristate "/proc/efi/vars support"
-	help
-	  If you say Y here, you are able to get EFI (Extensible Firmware
-	  Interface) variable information in /proc/efi/vars.  You may read,
-	  write, create, and destroy EFI variables through this interface.
-
-	  To use this option, you have to check that the "/proc file system
-	  support" (CONFIG_PROC_FS) is enabled, too.
+source "drivers/efi/Kconfig"
 
 config NR_CPUS
 	int "Maximum number of CPUs (2-64)"
diff -urN linux-2.6.0-test4/arch/ia64/kernel/efivars.c linux-2.6.0-test4-all/arch/ia64/kernel/efivars.c
--- linux-2.6.0-test4/arch/ia64/kernel/efivars.c	2003-08-22 16:55:33.000000000 -0700
+++ linux-2.6.0-test4-all/arch/ia64/kernel/efivars.c	1969-12-31 16:00:00.000000000 -0800
@@ -1,508 +0,0 @@
-/*
- * EFI Variables - efivars.c
- *
- * Copyright (C) 2001 Dell Computer Corporation <Matt_Domsch@dell.com>
- *
- * This code takes all variables accessible from EFI runtime and
- *  exports them via /proc
- *
- * Reads to /proc/efi/vars/varname return an efi_variable_t structure.
- * Writes to /proc/efi/vars/varname must be an efi_variable_t structure.
- * Writes with DataSize = 0 or Attributes = 0 deletes the variable.
- * Writes with a new value in VariableName+VendorGuid creates
- * a new variable.
- *
- *
- *  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.
- *
- *  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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
- *
- * Changelog:
- *
- *  10 Dec 2002 - Matt Domsch <Matt_Domsch@dell.com>
- *   fix locking per Peter Chubb's findings
- * 
- *  25 Mar 2002 - Matt Domsch <Matt_Domsch@dell.com>
- *   move uuid_unparse() to include/asm-ia64/efi.h:efi_guid_unparse()
- *
- *  12 Feb 2002 - Matt Domsch <Matt_Domsch@dell.com>
- *   use list_for_each_safe when deleting vars.
- *   remove ifdef CONFIG_SMP around include <linux/smp.h>
- *   v0.04 release to linux-ia64@linuxia64.org
- *
- *  20 April 2001 - Matt Domsch <Matt_Domsch@dell.com>
- *   Moved vars from /proc/efi to /proc/efi/vars, and made
- *   efi.c own the /proc/efi directory.
- *   v0.03 release to linux-ia64@linuxia64.org
- *
- *  26 March 2001 - Matt Domsch <Matt_Domsch@dell.com>
- *   At the request of Stephane, moved ownership of /proc/efi
- *   to efi.c, and now efivars lives under /proc/efi/vars.
- *
- *  12 March 2001 - Matt Domsch <Matt_Domsch@dell.com>
- *   Feedback received from Stephane Eranian incorporated.
- *   efivar_write() checks copy_from_user() return value.
- *   efivar_read/write() returns proper errno.
- *   v0.02 release to linux-ia64@linuxia64.org
- *
- *  26 February 2001 - Matt Domsch <Matt_Domsch@dell.com>
- *   v0.01 release to linux-ia64@linuxia64.org
- */
-
-#include <linux/config.h>
-#include <linux/types.h>
-#include <linux/errno.h>
-#include <linux/init.h>
-#include <linux/proc_fs.h>
-#include <linux/sched.h>		/* for capable() */
-#include <linux/mm.h>
-#include <linux/module.h>
-#include <linux/smp.h>
-#include <linux/efi.h>
-
-#include <asm/uaccess.h>
-
-MODULE_AUTHOR("Matt Domsch <Matt_Domsch@Dell.com>");
-MODULE_DESCRIPTION("/proc interface to EFI Variables");
-MODULE_LICENSE("GPL");
-
-#define EFIVARS_VERSION "0.06 2002-Dec-10"
-
-static int
-efivar_read(char *page, char **start, off_t off,
-	    int count, int *eof, void *data);
-static int
-efivar_write(struct file *file, const char *buffer,
-	     unsigned long count, void *data);
-
-
-/*
- * The maximum size of VariableName + Data = 1024
- * Therefore, it's reasonable to save that much
- * space in each part of the structure,
- * and we use a page for reading/writing.
- */
-
-typedef struct _efi_variable_t {
-	efi_char16_t  VariableName[1024/sizeof(efi_char16_t)];
-	efi_guid_t    VendorGuid;
-	unsigned long DataSize;
-	__u8          Data[1024];
-	efi_status_t  Status;
-	__u32         Attributes;
-} __attribute__((packed)) efi_variable_t;
-
-
-typedef struct _efivar_entry_t {
-	efi_variable_t          var;
-	struct proc_dir_entry   *entry;
-	struct list_head        list;
-} efivar_entry_t;
-
-/*
-  efivars_lock protects two things:
-  1) efivar_list - adds, removals, reads, writes
-  2) efi.[gs]et_variable() calls.
-  It must not be held when creating proc entries or calling kmalloc.
-  efi.get_next_variable() is only called from efivars_init(),
-  which is protected by the BKL, so that path is safe.
-*/
-static spinlock_t efivars_lock = SPIN_LOCK_UNLOCKED;
-static LIST_HEAD(efivar_list);
-static struct proc_dir_entry *efi_vars_dir;
-
-#define efivar_entry(n) list_entry(n, efivar_entry_t, list)
-
-/* Return the number of unicode characters in data */
-static unsigned long
-utf8_strlen(efi_char16_t *data, unsigned long maxlength)
-{
-	unsigned long length = 0;
-	while (*data++ != 0 && length < maxlength)
-		length++;
-	return length;
-}
-
-/* Return the number of bytes is the length of this string */
-/* Note: this is NOT the same as the number of unicode characters */
-static inline unsigned long
-utf8_strsize(efi_char16_t *data, unsigned long maxlength)
-{
-	return utf8_strlen(data, maxlength/sizeof(efi_char16_t)) * sizeof(efi_char16_t);
-}
-
-
-static int
-proc_calc_metrics(char *page, char **start, off_t off,
-		  int count, int *eof, int len)
-{
-	if (len <= off+count) *eof = 1;
-	*start = page + off;
-	len -= off;
-	if (len>count) len = count;
-	if (len<0) len = 0;
-	return len;
-}
-
-/*
- * efivar_create_proc_entry()
- * Requires:
- *    variable_name_size = number of bytes required to hold
- *                         variable_name (not counting the NULL
- *                         character at the end.
- *    efivars_lock is not held on entry or exit.
- * Returns 1 on failure, 0 on success
- */
-static int
-efivar_create_proc_entry(unsigned long variable_name_size,
-			 efi_char16_t *variable_name,
-			 efi_guid_t *vendor_guid)
-{
-	int i, short_name_size = variable_name_size / sizeof(efi_char16_t) + 38;
-	char *short_name;
-	efivar_entry_t *new_efivar;
-
-	short_name = kmalloc(short_name_size+1, GFP_KERNEL);
-	new_efivar = kmalloc(sizeof(efivar_entry_t), GFP_KERNEL);
-
-	if (!short_name || !new_efivar)  {
-		if (short_name)        kfree(short_name);
-		if (new_efivar)        kfree(new_efivar);
-		return 1;
-	}
-	memset(short_name, 0, short_name_size+1);
-	memset(new_efivar, 0, sizeof(efivar_entry_t));
-
-	memcpy(new_efivar->var.VariableName, variable_name,
-	       variable_name_size);
-	memcpy(&(new_efivar->var.VendorGuid), vendor_guid, sizeof(efi_guid_t));
-
-	/* Convert Unicode to normal chars (assume top bits are 0),
-	   ala UTF-8 */
-	for (i=0; i< (int) (variable_name_size / sizeof(efi_char16_t)); i++) {
-		short_name[i] = variable_name[i] & 0xFF;
-	}
-
-	/* This is ugly, but necessary to separate one vendor's
-	   private variables from another's.         */
-
-	*(short_name + strlen(short_name)) = '-';
-	efi_guid_unparse(vendor_guid, short_name + strlen(short_name));
-
-	/* Create the entry in proc */
-	new_efivar->entry = create_proc_entry(short_name, 0600, efi_vars_dir);
-	kfree(short_name); short_name = NULL;
-	if (!new_efivar->entry) return 1;
-
-	new_efivar->entry->owner = THIS_MODULE;
-	new_efivar->entry->data = new_efivar;
-	new_efivar->entry->read_proc = efivar_read;
-	new_efivar->entry->write_proc = efivar_write;
-
-	spin_lock(&efivars_lock);
-	list_add(&new_efivar->list, &efivar_list);
-	spin_unlock(&efivars_lock);
-
-	return 0;
-}
-
-
-
-/***********************************************************
- * efivar_read()
- * Requires:
- * Modifies: page
- * Returns: number of bytes written, or -EINVAL on failure
- ***********************************************************/
-
-static int
-efivar_read(char *page, char **start, off_t off, int count, int *eof, void *data)
-{
-	int len = sizeof(efi_variable_t);
-	efivar_entry_t *efi_var = data;
-	efi_variable_t *var_data = (efi_variable_t *)page;
-
-	if (!page || !data) return -EINVAL;
-
-	spin_lock(&efivars_lock);
-
-	memcpy(var_data, &efi_var->var, len);
-
-	var_data->DataSize = 1024;
-	var_data->Status = efi.get_variable(var_data->VariableName,
-					    &var_data->VendorGuid,
-					    &var_data->Attributes,
-					    &var_data->DataSize,
-					    var_data->Data);
-
-	spin_unlock(&efivars_lock);
-
-	return proc_calc_metrics(page, start, off, count, eof, len);
-}
-
-/***********************************************************
- * efivar_write()
- * Requires: data is an efi_setvariable_t data type,
- *           properly filled in, possibly by a call
- *           first to efivar_read().
- *           Caller must have CAP_SYS_ADMIN
- * Modifies: NVRAM
- * Returns: var_data->DataSize on success, errno on failure
- *
- ***********************************************************/
-static int
-efivar_write(struct file *file, const char *buffer,
-	     unsigned long count, void *data)
-{
-	unsigned long strsize1, strsize2;
-	int found=0;
-	struct list_head *pos, *n;
-	unsigned long size = sizeof(efi_variable_t);
-	efi_status_t status;
-	efivar_entry_t *efivar = data, *search_efivar = NULL;
-	efi_variable_t *var_data;
-	if (!data || count != size) {
-		printk(KERN_WARNING "efivars: improper struct of size 0x%lx passed.\n", count);
-		return -EINVAL;
-	}
-	if (!capable(CAP_SYS_ADMIN))
-		return -EACCES;
-
-	var_data = kmalloc(size, GFP_KERNEL);
-	if (!var_data)
-		return -ENOMEM;
-	if (copy_from_user(var_data, buffer, size)) {
-		kfree(var_data);
-		return -EFAULT;
-	}
-
-	spin_lock(&efivars_lock);
-
-	/* Since the data ptr we've currently got is probably for
-	   a different variable find the right variable.
-	   This allows any properly formatted data structure to
-	   be written to any of the files in /proc/efi/vars and it will work.
-	*/
-	list_for_each_safe(pos, n, &efivar_list) {
-		search_efivar = efivar_entry(pos);
-		strsize1 = utf8_strsize(search_efivar->var.VariableName, 1024);
-		strsize2 = utf8_strsize(var_data->VariableName, 1024);
-		if ( strsize1 == strsize2 &&
-		     !memcmp(&(search_efivar->var.VariableName),
-			     var_data->VariableName, strsize1) &&
-		     !efi_guidcmp(search_efivar->var.VendorGuid,
-				  var_data->VendorGuid)) {
-			found = 1;
-			break;
-		}
-	}
-	if (found) efivar = search_efivar;
-
-	status = efi.set_variable(var_data->VariableName,
-				  &var_data->VendorGuid,
-				  var_data->Attributes,
-				  var_data->DataSize,
-				  var_data->Data);
-
-	if (status != EFI_SUCCESS) {
-		printk(KERN_WARNING "set_variable() failed: status=%lx\n", status);
-		kfree(var_data);
-		spin_unlock(&efivars_lock);
-		return -EIO;
-	}
-
-
-	if (!var_data->DataSize || !var_data->Attributes) {
-		/* We just deleted the NVRAM variable */
-		remove_proc_entry(efivar->entry->name, efi_vars_dir);
-		list_del(&efivar->list);
-		kfree(efivar);
-	}
-
-	spin_unlock(&efivars_lock);
-
-	/* If this is a new variable, set up the proc entry for it. */
-	if (!found) {
-		efivar_create_proc_entry(utf8_strsize(var_data->VariableName,
-						      1024),
-					 var_data->VariableName,
-					 &var_data->VendorGuid);
-	}
-
-	kfree(var_data);
-	return size;
-}
-
-/*
- * The EFI system table contains pointers to the SAL system table,
- * HCDP, ACPI, SMBIOS, etc, that may be useful to applications.
- */
-static ssize_t
-efi_systab_read(struct file *file, char *buffer, size_t count, loff_t *ppos)
-{
-	void *data;
-	u8 *proc_buffer;
-	ssize_t size, length;
-	int ret;
-	const int max_nr_entries = 7; 	/* num ptrs to tables we could expose */
-	const int max_line_len = 80;
-
-	if (!efi.systab)
-		return 0;
-
-	proc_buffer = kmalloc(max_nr_entries * max_line_len, GFP_KERNEL);
-	if (!proc_buffer)
-		return -ENOMEM;
-
-	length = 0;
-	if (efi.mps)
-		length += sprintf(proc_buffer + length, "MPS=0x%lx\n", __pa(efi.mps));
-	if (efi.acpi20)
-		length += sprintf(proc_buffer + length, "ACPI20=0x%lx\n", __pa(efi.acpi20));
-	if (efi.acpi)
-		length += sprintf(proc_buffer + length, "ACPI=0x%lx\n", __pa(efi.acpi));
-	if (efi.smbios)
-		length += sprintf(proc_buffer + length, "SMBIOS=0x%lx\n", __pa(efi.smbios));
-	if (efi.sal_systab)
-		length += sprintf(proc_buffer + length, "SAL=0x%lx\n", __pa(efi.sal_systab));
-	if (efi.hcdp)
-		length += sprintf(proc_buffer + length, "HCDP=0x%lx\n", __pa(efi.hcdp));
-	if (efi.boot_info)
-		length += sprintf(proc_buffer + length, "BOOTINFO=0x%lx\n", __pa(efi.boot_info));
-
-	if (*ppos >= length) {
-		ret = 0;
-		goto out;
-	}
-
-	data = proc_buffer + file->f_pos;
-	size = length - file->f_pos;
-	if (size > count)
-		size = count;
-	if (copy_to_user(buffer, data, size)) {
-		ret = -EFAULT;
-		goto out;
-	}
-
-	*ppos += size;
-	ret = size;
-
-out:
-	kfree(proc_buffer);
-	return ret;
-}
-
-static struct proc_dir_entry *efi_systab_entry;
-static struct file_operations efi_systab_fops = {
-	.read = efi_systab_read,
-};
-
-static int __init
-efivars_init(void)
-{
-	efi_status_t status;
-	efi_guid_t vendor_guid;
-	efi_char16_t *variable_name = kmalloc(1024, GFP_KERNEL);
-	unsigned long variable_name_size = 1024;
-
-	printk(KERN_INFO "EFI Variables Facility v%s\n", EFIVARS_VERSION);
-
-	/* Since efi.c happens before procfs is available,
-	   we create the directory here if it doesn't
-	   already exist.  There's probably a better way
-	   to do this.
-	*/
-	if (!efi_dir)
-		efi_dir = proc_mkdir("efi", NULL);
-
-	efi_systab_entry = create_proc_entry("systab", S_IRUSR | S_IRGRP, efi_dir);
-	if (efi_systab_entry)
-		efi_systab_entry->proc_fops = &efi_systab_fops;
-
-	efi_vars_dir = proc_mkdir("vars", efi_dir);
-
-	/* Per EFI spec, the maximum storage allocated for both
-	   the variable name and variable data is 1024 bytes.
-	*/
-
-	memset(variable_name, 0, 1024);
-
-	do {
-		variable_name_size=1024;
-
-		status = efi.get_next_variable(&variable_name_size,
-					       variable_name,
-					       &vendor_guid);
-
-
-		switch (status) {
-		case EFI_SUCCESS:
-			efivar_create_proc_entry(variable_name_size,
-						 variable_name,
-						 &vendor_guid);
-			break;
-		case EFI_NOT_FOUND:
-			break;
-		default:
-			printk(KERN_WARNING "get_next_variable: status=%lx\n", status);
-			status = EFI_NOT_FOUND;
-			break;
-		}
-
-	} while (status != EFI_NOT_FOUND);
-
-	kfree(variable_name);
-	return 0;
-}
-
-static void __exit
-efivars_exit(void)
-{
-	struct list_head *pos, *n;
-	efivar_entry_t *efivar;
-
-	spin_lock(&efivars_lock);
-	if (efi_systab_entry)
-		remove_proc_entry(efi_systab_entry->name, efi_dir);
-	list_for_each_safe(pos, n, &efivar_list) {
-		efivar = efivar_entry(pos);
-		remove_proc_entry(efivar->entry->name, efi_vars_dir);
-		list_del(&efivar->list);
-		kfree(efivar);
-	}
-	spin_unlock(&efivars_lock);
-
-	remove_proc_entry(efi_vars_dir->name, efi_dir);
-}
-
-module_init(efivars_init);
-module_exit(efivars_exit);
-
-/*
- * Overrides for Emacs so that we follow Linus's tabbing style.
- * Emacs will notice this stuff at the end of the file and automatically
- * adjust the settings for this buffer only.  This must remain at the end
- * of the file.
- * ---------------------------------------------------------------------------
- * Local variables:
- * c-indent-level: 4
- * c-brace-imaginary-offset: 0
- * c-brace-offset: -4
- * c-argdecl-indent: 4
- * c-label-offset: -4
- * c-continued-statement-offset: 4
- * c-continued-brace-offset: 0
- * indent-tabs-mode: nil
- * tab-width: 8
- * End:
- */
diff -urN linux-2.6.0-test4/arch/ia64/kernel/Makefile linux-2.6.0-test4-all/arch/ia64/kernel/Makefile
--- linux-2.6.0-test4/arch/ia64/kernel/Makefile	2003-08-22 17:02:32.000000000 -0700
+++ linux-2.6.0-test4-all/arch/ia64/kernel/Makefile	2003-08-29 11:45:12.000000000 -0700
@@ -8,7 +8,6 @@
 	 irq_lsapic.o ivt.o machvec.o pal.o patch.o process.o perfmon.o ptrace.o sal.o		\
 	 semaphore.o setup.o signal.o sys_ia64.o time.o traps.o unaligned.o unwind.o
 
-obj-$(CONFIG_EFI_VARS)		+= efivars.o
 obj-$(CONFIG_IA64_BRL_EMU)	+= brl_emu.o
 obj-$(CONFIG_IA64_GENERIC)	+= acpi-ext.o
 obj-$(CONFIG_IA64_HP_ZX1)	+= acpi-ext.o
diff -urN linux-2.6.0-test4/drivers/efi/efivars.c linux-2.6.0-test4-all/drivers/efi/efivars.c
--- linux-2.6.0-test4/drivers/efi/efivars.c	1969-12-31 16:00:00.000000000 -0800
+++ linux-2.6.0-test4-all/drivers/efi/efivars.c	2003-08-29 16:33:55.000000000 -0700
@@ -0,0 +1,677 @@
+/*
+ * EFI Variables - efivars.c
+ *
+ * Copyright (C) 2001 Dell Computer Corporation <Matt_Domsch@dell.com>
+ *
+ * This code takes all variables accessible from EFI runtime and
+ *  exports them via sysfs
+ *
+ *  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.
+ *
+ *  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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ * Changelog:
+ *
+ *  29 Aug 2003 - Matt Tolentino <matthew.e.tolentino@intel.com)
+ *   converted driver to export variable information via sysfs 
+ *   move to drivers/efi directory
+ *   bumped revision number to v0.07 to reflect conversion & move
+ *
+ *  10 Dec 2002 - Matt Domsch <Matt_Domsch@dell.com>
+ *   fix locking per Peter Chubb's findings
+ * 
+ *  25 Mar 2002 - Matt Domsch <Matt_Domsch@dell.com>
+ *   move uuid_unparse() to include/asm-ia64/efi.h:efi_guid_unparse()
+ *
+ *  12 Feb 2002 - Matt Domsch <Matt_Domsch@dell.com>
+ *   use list_for_each_safe when deleting vars.
+ *   remove ifdef CONFIG_SMP around include <linux/smp.h>
+ *   v0.04 release to linux-ia64@linuxia64.org
+ *
+ *  20 April 2001 - Matt Domsch <Matt_Domsch@dell.com>
+ *   Moved vars from /proc/efi to /proc/efi/vars, and made
+ *   efi.c own the /proc/efi directory.
+ *   v0.03 release to linux-ia64@linuxia64.org
+ *
+ *  26 March 2001 - Matt Domsch <Matt_Domsch@dell.com>
+ *   At the request of Stephane, moved ownership of /proc/efi
+ *   to efi.c, and now efivars lives under /proc/efi/vars.
+ *
+ *  12 March 2001 - Matt Domsch <Matt_Domsch@dell.com>
+ *   Feedback received from Stephane Eranian incorporated.
+ *   efivar_write() checks copy_from_user() return value.
+ *   efivar_read/write() returns proper errno.
+ *   v0.02 release to linux-ia64@linuxia64.org
+ *
+ *  26 February 2001 - Matt Domsch <Matt_Domsch@dell.com>
+ *   v0.01 release to linux-ia64@linuxia64.org
+ */
+
+#include <linux/config.h>
+#include <linux/types.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/sched.h>		/* for capable() */
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/string.h>
+#include <linux/smp.h>
+#include <linux/efi.h>
+#include <linux/sysfs.h>
+#include <linux/kobject.h>
+#include <linux/device.h>
+
+#include <asm/uaccess.h>
+
+MODULE_AUTHOR("Matt Domsch <Matt_Domsch@Dell.com>");
+MODULE_DESCRIPTION("sysfs interface to EFI Variables");
+MODULE_LICENSE("GPL");
+
+#define EFIVARS_VERSION "0.07 2003-Aug-29"
+
+/*
+ * efivars_lock protects two things:
+ * 1) efivar_list - adds, removals, reads, writes
+ * 2) efi.[gs]et_variable() calls.
+ * It must not be held when creating sysfs entries or calling kmalloc.
+ * efi.get_next_variable() is only called from efivars_init(),
+ * which is protected by the BKL, so that path is safe.
+ */
+static spinlock_t efivars_lock = SPIN_LOCK_UNLOCKED;
+static LIST_HEAD(efivar_list);
+
+/*
+ * The maximum size of VariableName + Data = 1024
+ * Therefore, it's reasonable to save that much
+ * space in each part of the structure,
+ * and we use a page for reading/writing.
+ */
+
+struct efi_variable {
+	efi_char16_t  VariableName[1024/sizeof(efi_char16_t)];
+	efi_guid_t    VendorGuid;
+	unsigned long DataSize;
+	__u8          Data[1024];
+	efi_status_t  Status;
+	__u32         Attributes;
+} __attribute__((packed));
+
+
+struct efivar_entry {
+	struct efi_variable var;
+	struct list_head list;
+	struct kobject kobj;
+};
+
+#define get_efivar_entry(n) list_entry(n, struct efivar_entry, list)
+
+struct efivar_attribute {
+	struct attribute attr;
+	ssize_t (*show) (struct efivar_entry *entry, char *buf);
+	ssize_t (*store)(struct efivar_entry *entry, const char *buf, size_t count);
+};
+
+#define EFIVAR_ATTR(_name, _mode, _show, _store) \
+struct efivar_attribute efivar_attr_##_name = { \
+	.attr = {.name = __stringify(_name), .mode = _mode }, \
+	.show = _show, \
+	.store = _store, \
+};
+
+#define VAR_SUBSYS_ATTR(_name, _mode, _show, _store) \
+struct subsys_attribute var_subsys_attr_##_name = { \
+	.attr = {.name = __stringify(_name), .mode = _mode }, \
+	.show = _show, \
+	.store = _store, \
+};
+
+#define to_efivar_attr(_attr) container_of(_attr, struct efivar_attribute, attr)
+#define to_efivar_entry(obj)  container_of(obj, struct efivar_entry, kobj)
+
+/* 
+ * Prototype for sysfs creation function 
+ */
+static int
+efivar_create_sysfs_entry(unsigned long variable_name_size,
+			  efi_char16_t *variable_name,
+			  efi_guid_t *vendor_guid);
+
+/* Return the number of unicode characters in data */
+static unsigned long
+utf8_strlen(efi_char16_t *data, unsigned long maxlength)
+{
+	unsigned long length = 0;
+
+	while (*data++ != 0 && length < maxlength)
+		length++;
+	return length;
+}
+
+/* 
+ * Return the number of bytes is the length of this string 
+ * Note: this is NOT the same as the number of unicode characters 
+ */
+static inline unsigned long
+utf8_strsize(efi_char16_t *data, unsigned long maxlength)
+{
+	return utf8_strlen(data, maxlength/sizeof(efi_char16_t)) * sizeof(efi_char16_t);
+}
+
+/*
+ * Convenience function to call GetVariable/SetVariable
+ */
+static int
+get_var_data(struct efi_variable *var)
+{
+	efi_status_t status = EFI_NOT_FOUND;
+	
+	spin_lock(&efivars_lock);
+	status = efi.get_variable(var->VariableName,
+			 	  &var->VendorGuid,
+			 	  &var->Attributes,
+			 	  &var->DataSize,
+			 	  var->Data);
+	spin_unlock(&efivars_lock);
+	
+	return status;
+}
+
+static ssize_t
+efivar_guid_read(struct efivar_entry *entry, char *buf)
+{
+	struct efi_variable *var = &entry->var;
+	char *str = buf;
+
+	if (!entry || !var || !buf) 
+		return 0;
+
+	efi_guid_unparse(&var->VendorGuid, str);
+	str += strlen(str);
+	str += sprintf(str, "\n");
+
+	return str - buf;	
+}
+
+static int 
+efivar_attr_read(struct efivar_entry *entry, char *buf)
+{
+	struct efi_variable *var = &entry->var;
+	char *str = buf;
+	efi_status_t status = EFI_NOT_FOUND;
+	
+	if (!entry || !var || !buf)
+		return 0;
+
+	if (!var->Attributes) {
+		status = get_var_data(var);
+		if (status != EFI_SUCCESS) {
+			printk(KERN_WARNING "GetVariable() failed 0x%lx!\n",
+					     status);
+			return -EIO;
+		}
+	}
+
+	if (var->Attributes & 0x1)
+		str += sprintf(str, "EFI_VARIABLE_NON_VOLATILE\n");
+	if (var->Attributes & 0x2)
+		str += sprintf(str, "EFI_VARIABLE_BOOTSERVICE_ACCESS\n");
+	if (var->Attributes & 0x4)
+		str += sprintf(str, "EFI_VARIABLE_RUNTIME_ACCESS\n");
+
+	return str - buf;
+	
+}
+static int
+efivar_size_read(struct efivar_entry *entry, char *buf)
+{
+	struct efi_variable *var = &entry->var;
+	char *str = buf;
+	efi_status_t status = EFI_NOT_FOUND;
+	
+	if (!entry || !var || !buf)
+		return 0;
+	
+	if (!var->DataSize) {
+		status = get_var_data(var);
+		if (status != EFI_SUCCESS) {
+			printk(KERN_WARNING "GetVariable() failed 0x%lx!\n",
+					     status);
+			return -EIO;
+		}
+	}
+	str += sprintf(str, "0x%lx\n", var->DataSize);
+	
+	return str - buf;
+}
+
+static int 
+efivar_data_read(struct efivar_entry *entry, char *buf)
+{
+	struct efi_variable *var = &entry->var;
+	efi_status_t status;
+	
+	if (!entry || !buf)
+		return 0;
+
+	if (!var->Data) {
+		status = get_var_data(var);
+		if (status != EFI_SUCCESS) {
+			printk(KERN_WARNING "GetVariable() failed 0x%lx!\n",
+					     status);
+			return -EIO;
+		}
+	}
+	memcpy(buf, var->Data, var->DataSize);
+	return 0;
+}
+/* 
+ * We allow each variable to be edited via rewriting the 
+ * entire efi variable structure.
+ */
+static ssize_t 
+efivar_edit(struct efivar_entry *entry, const char *buf, size_t count)
+{
+	struct efi_variable *new_var, *var = &entry->var;
+	efi_status_t status = EFI_NOT_FOUND;
+	
+	if (count != sizeof(struct efi_variable))
+		return -1;
+
+	new_var = (struct efi_variable *)buf;
+	/* 
+	 * If only updating the variable data, then the name 
+	 * and guid should remain the same 
+	 */
+	if (new_var->VariableName != var->VariableName) {
+		return -EINVAL;
+	}
+
+	if ((new_var->DataSize <= 0) || (new_var->Attributes == 0)){
+		printk(KERN_ERR "DataSize & Attributes must be valid!\n");
+		return -EINVAL;
+	}
+
+	spin_lock(&efivars_lock);
+	status = efi.set_variable(new_var->VariableName,
+				  &new_var->VendorGuid,
+				  new_var->Attributes,
+				  new_var->DataSize,
+				  new_var->Data);
+
+	spin_unlock(&efivars_lock);
+
+	if (status != EFI_SUCCESS) {
+		printk(KERN_WARNING "set_variable() failed: status=%lx\n", 
+				status);
+		return -EIO;
+	}
+
+	memcpy(&entry->var, new_var, sizeof(struct efi_variable));
+
+	return status;
+}
+
+/* 
+ * Generic read/write functions that call the specific functions of 
+ * the atttributes...
+ */
+static ssize_t efivar_attr_show(struct kobject *kobj, struct attribute *attr,
+			        char *buf) 
+{
+	struct efivar_entry *var =  to_efivar_entry(kobj);
+	struct efivar_attribute *efivar_attr = to_efivar_attr(attr);
+	ssize_t ret = 0;
+	
+	if (efivar_attr->show) {
+		ret = efivar_attr->show(var, buf);
+	}
+	return ret;
+}
+
+static ssize_t efivar_attr_store(struct kobject *kobj, struct attribute *attr,
+				 const char *buf, size_t count)
+{
+	struct efivar_entry *var = to_efivar_entry(kobj);
+	struct efivar_attribute *efivar_attr = to_efivar_attr(attr);
+	ssize_t ret = 0;
+	
+	if (efivar_attr->store)
+		ret = efivar_attr->store(var, buf, count);
+
+	return ret;
+}
+
+static struct sysfs_ops efivar_attr_ops = {
+	.show = efivar_attr_show,
+	.store = efivar_attr_store,
+};
+
+static void efivar_release(struct kobject *kobj)
+{
+	struct efivar_entry *var = container_of(kobj, struct efivar_entry, kobj);
+	list_del(&var->list);
+	kfree(var);
+}
+
+static EFIVAR_ATTR(guid, 0644, efivar_guid_read, NULL);
+static EFIVAR_ATTR(attributes, 0644, efivar_attr_read, NULL);
+static EFIVAR_ATTR(size, 0644, efivar_size_read, NULL);
+static EFIVAR_ATTR(data, 0644, efivar_data_read, NULL); 
+static EFIVAR_ATTR(edit_var, 0200, NULL, efivar_edit);
+
+static struct attribute *def_attrs[] = {
+	&efivar_attr_guid.attr,
+	&efivar_attr_size.attr,
+	&efivar_attr_attributes.attr,
+	&efivar_attr_data.attr,
+	&efivar_attr_edit_var.attr,
+	NULL,
+};
+
+static struct kobj_type ktype_efivar = {
+	.release = efivar_release,
+	.sysfs_ops = &efivar_attr_ops,
+	.default_attrs = def_attrs,
+};
+
+/* Why do I need this? */
+static ssize_t 
+dummy(struct subsystem *sub, char *buf)
+{
+	return 0;
+}
+
+static inline void 
+efivar_unregister(struct efivar_entry *var)
+{
+	kobject_unregister(&var->kobj);
+}
+
+
+static ssize_t 
+efivar_create(struct subsystem *sub, const char *buf, size_t count)
+{
+	struct efi_variable *new_var = (struct efi_variable *)buf;
+	struct efivar_entry *search_efivar = NULL;
+	unsigned long strsize1, strsize2;
+	struct list_head *pos, *n;
+	efi_status_t status = EFI_NOT_FOUND;
+	int found = 0;
+
+	spin_lock(&efivars_lock);
+
+	/* 
+	 * Does this variable already exist?
+	 */
+	list_for_each_safe(pos, n, &efivar_list) {
+		search_efivar = get_efivar_entry(pos);
+		strsize1 = utf8_strsize(search_efivar->var.VariableName, 1024);
+		strsize2 = utf8_strsize(new_var->VariableName, 1024);
+		if ( strsize1 == strsize2 &&
+		     !memcmp(&(search_efivar->var.VariableName),
+			     new_var->VariableName, strsize1) &&
+		     !efi_guidcmp(search_efivar->var.VendorGuid,
+				  new_var->VendorGuid)) {
+			found = 1;
+			break;
+		}
+	}
+	if (found) {
+        	spin_unlock(&efivars_lock);
+		return -EINVAL;
+	} 
+	
+	/* now *really* create the variable via EFI */
+	status = efi.set_variable(new_var->VariableName,
+				  &new_var->VendorGuid,
+				  new_var->Attributes,
+				  new_var->DataSize,
+				  new_var->Data);
+
+	if (status != EFI_SUCCESS) {
+		printk(KERN_WARNING "set_variable() failed: status=%lx\n", 
+			status);
+		spin_unlock(&efivars_lock);
+		return -EIO;
+	}
+        spin_unlock(&efivars_lock);
+
+	/* Create the entry in sysfs.  Locking is not required here */
+	status = efivar_create_sysfs_entry(utf8_strsize(new_var->VariableName, 
+							1024),
+				  new_var->VariableName,
+				  &new_var->VendorGuid);
+	return status;
+}
+
+static ssize_t
+efivar_delete(struct subsystem *sub, const char *buf, size_t count)
+{
+	struct efi_variable *del_var = (struct efi_variable *)buf;
+	struct efivar_entry *search_efivar = NULL;
+	unsigned long strsize1, strsize2;
+	struct list_head *pos, *n;
+	efi_status_t status = EFI_NOT_FOUND;
+	int found = 0;
+
+	spin_lock(&efivars_lock);
+
+	/* 
+	 * Does this variable already exist?
+	 */
+	list_for_each_safe(pos, n, &efivar_list) {
+		search_efivar = get_efivar_entry(pos);
+		strsize1 = utf8_strsize(search_efivar->var.VariableName, 1024);
+		strsize2 = utf8_strsize(del_var->VariableName, 1024);
+		if ( strsize1 == strsize2 &&
+		     !memcmp(&(search_efivar->var.VariableName),
+			     del_var->VariableName, strsize1) &&
+		     !efi_guidcmp(search_efivar->var.VendorGuid,
+				  del_var->VendorGuid)) {
+			found = 1;
+			break;
+		}
+	}
+	if (!found) {
+		spin_unlock(&efivars_lock);
+		return -EINVAL;
+	} 
+	/* force the Attributes/DataSize to 0 to ensure deletion */
+	del_var->Attributes = 0;
+	del_var->DataSize = 0;
+	
+	status = efi.set_variable(del_var->VariableName,
+				  &del_var->VendorGuid,
+				  del_var->Attributes,
+				  del_var->DataSize,
+				  del_var->Data);
+
+	if (status != EFI_SUCCESS) {
+		printk(KERN_WARNING "set_variable() failed: status=%lx\n", 
+			status);
+		spin_unlock(&efivars_lock);
+		return -EIO;
+	}
+	/* complete the eradication... */
+	efivar_unregister(search_efivar);
+
+	/* It's dead Jim.... */
+        spin_unlock(&efivars_lock);
+
+	return status;
+}
+
+static VAR_SUBSYS_ATTR(new_var, 0200, dummy, efivar_create);
+static VAR_SUBSYS_ATTR(del_var, 0200, dummy, efivar_delete);
+
+static struct subsys_attribute *var_subsys_attrs[] = {
+	&var_subsys_attr_new_var,
+	&var_subsys_attr_del_var,
+	NULL,
+};
+
+static decl_subsys(vars, &ktype_efivar, NULL);
+static decl_subsys(efi, NULL, NULL);
+
+
+/*
+ * efivar_create_sysfs_entry()
+ * Requires:
+ *    variable_name_size = number of bytes required to hold
+ *                         variable_name (not counting the NULL
+ *                         character at the end.
+ *    efivars_lock is not held on entry or exit.
+ * Returns 1 on failure, 0 on success
+ */
+static int
+efivar_create_sysfs_entry(unsigned long variable_name_size,
+			  efi_char16_t *variable_name,
+			  efi_guid_t *vendor_guid)
+{
+	int i, short_name_size = variable_name_size / sizeof(efi_char16_t) + 38;
+	char *short_name;
+	struct efivar_entry *new_efivar;
+
+        short_name = kmalloc(short_name_size + 1, GFP_KERNEL);
+        new_efivar = kmalloc(sizeof(struct efivar_entry), GFP_KERNEL);
+
+	if (!short_name || !new_efivar)  {
+		if (short_name)        kfree(short_name);
+		if (new_efivar)        kfree(new_efivar);
+		return 1;
+	}
+	memset(short_name, 0, short_name_size+1);
+	memset(new_efivar, 0, sizeof(struct efivar_entry));
+
+	memcpy(new_efivar->var.VariableName, variable_name,
+	       variable_name_size);
+	memcpy(&(new_efivar->var.VendorGuid), vendor_guid, sizeof(efi_guid_t));
+
+	/* Convert Unicode to normal chars (assume top bits are 0),
+	   ala UTF-8 */
+	for (i=0; i < (int)(variable_name_size / sizeof(efi_char16_t)); i++) {
+		short_name[i] = variable_name[i] & 0xFF;
+	}
+	/* This is ugly, but necessary to separate one vendor's
+	   private variables from another's.         */
+
+	*(short_name + strlen(short_name)) = '-';
+	efi_guid_unparse(vendor_guid, short_name + strlen(short_name));
+
+	kobject_set_name(&new_efivar->kobj, short_name);
+
+	kobj_set_kset_s(new_efivar, vars_subsys);
+	kobject_register(&new_efivar->kobj);
+
+	kfree(short_name); short_name = NULL;
+	
+        spin_lock(&efivars_lock);
+        list_add(&new_efivar->list, &efivar_list);
+        spin_unlock(&efivars_lock);
+
+	return 0;
+}
+/* 
+ * For now we register the efi subsystem with the firmware subsystem
+ * and the vars subsystem with the efi subsystem.  In the future, it
+ * will probably make sense to split off the efi subsystem into
+ * its own driver, but for now only efivars will register with it,
+ * so just include it here.
+ */
+
+static int __init
+efivars_init(void)
+{
+	efi_status_t status = EFI_NOT_FOUND;
+	efi_guid_t vendor_guid;
+	efi_char16_t *variable_name = kmalloc(1024, GFP_KERNEL);
+	struct subsys_attribute *attr;
+	unsigned long variable_name_size = 1024;
+	int i, rc = 0, error = 0;
+
+	printk(KERN_INFO "EFI Variables Facility v%s\n", EFIVARS_VERSION);
+
+	/* 
+	 * For now we'll register the efi subsys within this driver
+	 */
+	
+	rc = firmware_register(&efi_subsys);
+	
+	if (rc)
+		return rc;
+
+	kset_set_kset_s(&vars_subsys, efi_subsys);
+	subsystem_register(&vars_subsys);
+
+	/* 
+	 * Per EFI spec, the maximum storage allocated for both
+	 * the variable name and variable data is 1024 bytes.
+	 */
+
+	memset(variable_name, 0, 1024);
+
+	do {
+		variable_name_size = 1024;
+
+		status = efi.get_next_variable(&variable_name_size,
+					       variable_name,
+					       &vendor_guid);
+		switch (status) {
+		case EFI_SUCCESS:
+			efivar_create_sysfs_entry(variable_name_size,
+						 variable_name,
+						 &vendor_guid);
+			break;
+		case EFI_NOT_FOUND:
+			break;
+		default:
+			printk(KERN_WARNING "get_next_variable: status=%lx\n", 
+				status);
+			status = EFI_NOT_FOUND;
+			break;
+		}
+	} while (status != EFI_NOT_FOUND);
+
+	/* 
+	 * Now add attributes to allow creation of new vars
+	 * and deletion of existing ones...
+	 */
+
+	for (i = 0; (attr = var_subsys_attrs[i]) && !error; i++) {
+		if (attr->show && attr->store)
+			error = subsys_create_file(&vars_subsys, attr);
+	}
+
+	kfree(variable_name);
+	return 0;
+}
+
+static void __exit
+efivars_exit(void)
+{
+	struct list_head *pos, *n;
+
+        spin_lock(&efivars_lock);
+
+	list_for_each_safe(pos, n, &efivar_list)
+		efivar_unregister(get_efivar_entry(pos));
+
+	spin_unlock(&efivars_lock);
+
+	subsystem_unregister(&vars_subsys);
+	firmware_unregister(&efi_subsys);
+}
+
+module_init(efivars_init);
+module_exit(efivars_exit);
+
diff -urN linux-2.6.0-test4/drivers/efi/Kconfig linux-2.6.0-test4-all/drivers/efi/Kconfig
--- linux-2.6.0-test4/drivers/efi/Kconfig	1969-12-31 16:00:00.000000000 -0800
+++ linux-2.6.0-test4-all/drivers/efi/Kconfig	2003-08-29 11:45:12.000000000 -0700
@@ -0,0 +1,23 @@
+#
+# EFI Configuration
+#
+
+menu "EFI Support"
+
+config EFI
+	bool "EFI Driver Support"
+	---help---
+	  EFI (Extensible Firmware Interface) support for Linux enables 
+	  the use of drivers that provide architecturally independent 
+	  functionality.  This support is applicable to architectures 
+	  that support EFI.  
+
+config EFI_VARS
+	tristate "EFI Variable Support via sysfs"
+	---help---
+	  If you say Y here, you are able to get EFI (Extensible Firmware
+	  Interface) variable information via sysfs.  You may read,
+	  write, create, and destroy EFI variables through this interface.
+
+
+endmenu
diff -urN linux-2.6.0-test4/drivers/efi/Makefile linux-2.6.0-test4-all/drivers/efi/Makefile
--- linux-2.6.0-test4/drivers/efi/Makefile	1969-12-31 16:00:00.000000000 -0800
+++ linux-2.6.0-test4-all/drivers/efi/Makefile	2003-08-29 11:45:12.000000000 -0700
@@ -0,0 +1,4 @@
+# EFI Variable Access
+
+obj-$(CONFIG_EFI_VARS)		+= efivars.o
+
diff -urN linux-2.6.0-test4/drivers/Makefile linux-2.6.0-test4-all/drivers/Makefile
--- linux-2.6.0-test4/drivers/Makefile	2003-08-22 16:58:44.000000000 -0700
+++ linux-2.6.0-test4-all/drivers/Makefile	2003-08-29 11:45:12.000000000 -0700
@@ -49,3 +49,4 @@
 obj-$(CONFIG_MCA)		+= mca/
 obj-$(CONFIG_EISA)		+= eisa/
 obj-$(CONFIG_CPU_FREQ)		+= cpufreq/
+obj-$(CONFIG_EFI)		+= efi/
diff -urN linux-2.6.0-test4/include/linux/efi.h linux-2.6.0-test4-all/include/linux/efi.h
--- linux-2.6.0-test4/include/linux/efi.h	2003-08-29 12:21:01.000000000 -0700
+++ linux-2.6.0-test4-all/include/linux/efi.h	2003-08-29 11:45:12.000000000 -0700
@@ -16,6 +16,7 @@
 #include <linux/time.h>
 #include <linux/types.h>
 #include <linux/proc_fs.h>
+#include <linux/kobject.h>
 #include <linux/rtc.h>
 #include <linux/ioport.h>
 

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