kernel/git/stable/linux.git/drivers/firmware/efivars.c, branch master

efi: split efisubsystem from efivars

2013-04-17T12:27:06+00:00

This registers /sys/firmware/efi/{,systab,efivars/} whenever EFI is enabled and the system is booted with EFI. This allows *) userspace to check for the existence of /sys/firmware/efi as a way to determine whether or it is running on an EFI system. *) 'mount -t efivarfs none /sys/firmware/efi/efivars' without manually loading any modules. [ Also, move the efivar API into vars.c and unconditionally compile it. This allows us to move efivars.c, which now only contains the sysfs variable code, into the firmware/efi directory. Note that the efivars.c filename is kept to maintain backwards compatability with the old efivars.ko module. With this patch it is now possible for efivarfs to be built without CONFIG_EFI_VARS - Matt ] Cc: Seiji Aguchi Cc: Tony Luck Cc: Mike Waychison Cc: Kay Sievers Cc: Jeremy Kerr Cc: Matthew Garrett Cc: Chun-Yi Lee Cc: Andy Whitcroft Cc: Tobias Powalowski Signed-off-by: Tom Gundersen Signed-off-by: Matt Fleming

efivarfs: Move to fs/efivarfs

2013-04-17T12:25:09+00:00

Now that efivarfs uses the efivar API, move it out of efivars.c and into fs/efivarfs where it belongs. This move will eventually allow us to enable the efivarfs code without having to also enable CONFIG_EFI_VARS built, and vice versa. Furthermore, things like, mount -t efivarfs none /sys/firmware/efi/efivars will now work if efivarfs is built as a module without requiring the use of MODULE_ALIAS(), which would have been necessary when the efivarfs code was part of efivars.c. Cc: Matthew Garrett Cc: Jeremy Kerr Reviewed-by: Tom Gundersen Tested-by: Tom Gundersen Signed-off-by: Matt Fleming

efivars: Move pstore code into the new EFI directory

2013-04-17T12:24:01+00:00

efivars.c has grown far too large and needs to be divided up. Create a new directory and move the persistence storage code to efi-pstore.c now that it uses the new efivar API. This helps us to greatly reduce the size of efivars.c and paves the way for moving other code out of efivars.c. Note that because CONFIG_EFI_VARS can be built as a module efi-pstore must also include support for building as a module. Reviewed-by: Tom Gundersen Tested-by: Tom Gundersen Cc: Seiji Aguchi Cc: Anton Vorontsov Cc: Colin Cross Cc: Kees Cook Cc: Matthew Garrett Cc: Tony Luck Signed-off-by: Matt Fleming

efivars: efivar_entry API

2013-04-17T12:23:59+00:00

There isn't really a formal interface for dealing with EFI variables or struct efivar_entry. Historically, this has led to various bits of code directly accessing the generic EFI variable ops, which inherently ties it to specific EFI variable operations instead of indirectly using whatever ops were registered with register_efivars(). This lead to the efivarfs code only working with the generic EFI variable ops and not CONFIG_GOOGLE_SMI. Encapsulate everything that needs to access '__efivars' inside an efivar_entry_* API and use the new API in the pstore, sysfs and efivarfs code. Much of the efivars code had to be rewritten to use this new API. For instance, it is now up to the users of the API to build the initial list of EFI variables in their efivar_init() callback function. The variable list needs to be passed to efivar_init() which allows us to keep work arounds for things like implementation bugs in GetNextVariable() in a central location. Allowing users of the API to use a callback function to build the list greatly benefits the efivarfs code which needs to allocate inodes and dentries for every variable. It previously did this in a racy way because the code ran without holding the variable spinlock. Both the sysfs and efivarfs code maintain their own lists which means the two interfaces can be running simultaneously without interference, though it should be noted that because no synchronisation is performed it is very easy to create inconsistencies. efibootmgr doesn't currently use efivarfs and users are likely to also require the old sysfs interface, so it makes sense to allow both to be built. Reviewed-by: Tom Gundersen Tested-by: Tom Gundersen Cc: Seiji Aguchi Cc: Matthew Garrett Cc: Jeremy Kerr Cc: Tony Luck Cc: Mike Waychison Signed-off-by: Matt Fleming

efivars: Keep a private global pointer to efivars

2013-04-17T07:30:06+00:00

Some machines have an EFI variable interface that does not conform to the UEFI specification, e.g. CONFIG_GOOGLE_SMI. Add the necessary code so that it's only possible to use one implementation of EFI variable operations at runtime. This allows us to keep a single (file-scope) global pointer 'struct efivars', which simplifies access. This will hopefully dissuade developers from accessing the generic operations struct directly in the future, as was done in the efivarfs and pstore code, thereby allowing future code to work with both the generic efivar ops and the google SMI ops. This may seem like a step backwards in terms of modularity, but we don't need to track more than one 'struct efivars' at one time. There is no synchronisation done between multiple EFI variable operations, and according to Mike no one is using both the generic EFI var ops and CONFIG_GOOGLE_SMI simultaneously, though a single kernel build _does_ need to able to support both. It also helps to clearly highlight which functions form the core of the efivars interface - those that require access to __efivars. Reviewed-by: Tom Gundersen Tested-by: Tom Gundersen Acked-by: Mike Waychison Signed-off-by: Matt Fleming

efi: move utf16 string functions to efi.h

2013-04-17T07:28:21+00:00

There are currently two implementations of the utf16 string functions. Somewhat confusingly, they've got different names. Centralise the functions in efi.h. Reviewed-by: Tom Gundersen Tested-by: Tom Gundersen Reviewed-by: Mike Waychison Signed-off-by: Matt Fleming

efivars: Fix check for CONFIG_EFI_VARS_PSTORE_DEFAULT_DISABLE

2013-03-22T20:08:01+00:00

The 'CONFIG_' prefix is not implicit in IS_ENABLED(). Signed-off-by: Ben Hutchings Cc: Seth Forshee Cc: Signed-off-by: Matt Fleming

efivars: Handle duplicate names from get_next_variable()

2013-03-21T12:43:46+00:00

Some firmware exhibits a bug where the same VariableName and VendorGuid values are returned on multiple invocations of GetNextVariableName(). See, https://bugzilla.kernel.org/show_bug.cgi?id=47631 As a consequence of such a bug, Andre reports hitting the following WARN_ON() in the sysfs code after updating the BIOS on his, "Gigabyte Technology Co., Ltd. To be filled by O.E.M./Z77X-UD3H, BIOS F19e 11/21/2012)" machine, [ 0.581554] EFI Variables Facility v0.08 2004-May-17 [ 0.584914] ------------[ cut here ]------------ [ 0.585639] WARNING: at /home/andre/linux/fs/sysfs/dir.c:536 sysfs_add_one+0xd4/0x100() [ 0.586381] Hardware name: To be filled by O.E.M. [ 0.587123] sysfs: cannot create duplicate filename '/firmware/efi/vars/SbAslBufferPtrVar-01f33c25-764d-43ea-aeea-6b5a41f3f3e8' [ 0.588694] Modules linked in: [ 0.589484] Pid: 1, comm: swapper/0 Not tainted 3.8.0+ #7 [ 0.590280] Call Trace: [ 0.591066] [] ? sysfs_add_one+0xd4/0x100 [ 0.591861] [] warn_slowpath_common+0x7f/0xc0 [ 0.592650] [] warn_slowpath_fmt+0x4c/0x50 [ 0.593429] [] ? strlcat+0x65/0x80 [ 0.594203] [] sysfs_add_one+0xd4/0x100 [ 0.594979] [] create_dir+0x78/0xd0 [ 0.595753] [] sysfs_create_dir+0x86/0xe0 [ 0.596532] [] kobject_add_internal+0x9c/0x220 [ 0.597310] [] kobject_init_and_add+0x67/0x90 [ 0.598083] [] ? efivar_create_sysfs_entry+0x61/0x1c0 [ 0.598859] [] efivar_create_sysfs_entry+0x11b/0x1c0 [ 0.599631] [] register_efivars+0xde/0x420 [ 0.600395] [] ? edd_init+0x2f5/0x2f5 [ 0.601150] [] efivars_init+0xb8/0x104 [ 0.601903] [] do_one_initcall+0x12a/0x180 [ 0.602659] [] kernel_init_freeable+0x13e/0x1c6 [ 0.603418] [] ? loglevel+0x31/0x31 [ 0.604183] [] ? rest_init+0x80/0x80 [ 0.604936] [] kernel_init+0xe/0xf0 [ 0.605681] [] ret_from_fork+0x7c/0xb0 [ 0.606414] [] ? rest_init+0x80/0x80 [ 0.607143] ---[ end trace 1609741ab737eb29 ]--- There's not much we can do to work around and keep traversing the variable list once we hit this firmware bug. Our only solution is to terminate the loop because, as Lingzhu reports, some machines get stuck when they encounter duplicate names, > I had an IBM System x3100 M4 and x3850 X5 on which kernel would > get stuck in infinite loop creating duplicate sysfs files because, > for some reason, there are several duplicate boot entries in nvram > getting GetNextVariableName into a circle of iteration (with > period > 2). Also disable the workqueue, as efivar_update_sysfs_entries() uses GetNextVariableName() to figure out which variables have been created since the last iteration. That algorithm isn't going to work if GetNextVariableName() returns duplicates. Note that we don't disable EFI variable creation completely on the affected machines, it's just that any pstore dump-* files won't appear in sysfs until the next boot. Reported-by: Andre Heider Reported-by: Lingzhu Xiang Tested-by: Lingzhu Xiang Cc: Seiji Aguchi Cc: Signed-off-by: Matt Fleming

efivars: explicitly calculate length of VariableName

2013-03-21T12:43:46+00:00

It's not wise to assume VariableNameSize represents the length of VariableName, as not all firmware updates VariableNameSize in the same way (some don't update it at all if EFI_SUCCESS is returned). There are even implementations out there that update VariableNameSize with values that are both larger than the string returned in VariableName and smaller than the buffer passed to GetNextVariableName(), which resulted in the following bug report from Michael Schroeder, > On HP z220 system (firmware version 1.54), some EFI variables are > incorrectly named : > > ls -d /sys/firmware/efi/vars/*8be4d* | grep -v -- -8be returns > /sys/firmware/efi/vars/dbxDefault-pport8be4df61-93ca-11d2-aa0d-00e098032b8c > /sys/firmware/efi/vars/KEKDefault-pport8be4df61-93ca-11d2-aa0d-00e098032b8c > /sys/firmware/efi/vars/SecureBoot-pport8be4df61-93ca-11d2-aa0d-00e098032b8c > /sys/firmware/efi/vars/SetupMode-Information8be4df61-93ca-11d2-aa0d-00e098032b8c The issue here is that because we blindly use VariableNameSize without verifying its value, we can potentially read garbage values from the buffer containing VariableName if VariableNameSize is larger than the length of VariableName. Since VariableName is a string, we can calculate its size by searching for the terminating NULL character. Reported-by: Frederic Crozat Cc: Matthew Garrett Cc: Josh Boyer Cc: Michael Schroeder Cc: Lee, Chun-Yi Cc: Lingzhu Xiang Cc: Seiji Aguchi Signed-off-by: Matt Fleming

efivars: Add module parameter to disable use as a pstore backend

2013-03-21T12:43:46+00:00

We know that with some firmware implementations writing too much data to UEFI variables can lead to bricking machines. Recent changes attempt to address this issue, but for some it may still be prudent to avoid writing large amounts of data until the solution has been proven on a wide variety of hardware. Crash dumps or other data from pstore can potentially be a large data source. Add a pstore_module parameter to efivars to allow disabling its use as a backend for pstore. Also add a config option, CONFIG_EFI_VARS_PSTORE_DEFAULT_DISABLE, to allow setting the default value of this paramter to true (i.e. disabled by default). Signed-off-by: Seth Forshee Cc: Josh Boyer Cc: Matthew Garrett Cc: Seiji Aguchi Cc: Tony Luck Cc: Signed-off-by: Matt Fleming