Rather than incurring a division or requesting too many random bytes for
the given range, use the prandom_u32_max() function, which only takes
the minimum required bytes from the RNG and avoids divisions. This was
done mechanically with this coccinelle script:
@basic@
expression E;
type T;
identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32";
typedef u64;
@@
(
- ((T)get_random_u32() % (E))
+ prandom_u32_max(E)
|
- ((T)get_random_u32() & ((E) - 1))
+ prandom_u32_max(E * XXX_MAKE_SURE_E_IS_POW2)
|
- ((u64)(E) * get_random_u32() >> 32)
+ prandom_u32_max(E)
|
- ((T)get_random_u32() & ~PAGE_MASK)
+ prandom_u32_max(PAGE_SIZE)
)
@multi_line@
identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32";
identifier RAND;
expression E;
@@
- RAND = get_random_u32();
... when != RAND
- RAND %= (E);
+ RAND = prandom_u32_max(E);
// Find a potential literal
@literal_mask@
expression LITERAL;
type T;
identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32";
position p;
@@
((T)get_random_u32()@p & (LITERAL))
// Add one to the literal.
@script:python add_one@
literal << literal_mask.LITERAL;
RESULT;
@@
value = None
if literal.startswith('0x'):
value = int(literal, 16)
elif literal[0] in '123456789':
value = int(literal, 10)
if value is None:
print("I don't know how to handle %s" % (literal))
cocci.include_match(False)
elif value == 2**32 - 1 or value == 2**31 - 1 or value == 2**24 - 1 or value == 2**16 - 1 or value == 2**8 - 1:
print("Skipping 0x%x for cleanup elsewhere" % (value))
cocci.include_match(False)
elif value & (value + 1) != 0:
print("Skipping 0x%x because it's not a power of two minus one" % (value))
cocci.include_match(False)
elif literal.startswith('0x'):
coccinelle.RESULT = cocci.make_expr("0x%x" % (value + 1))
else:
coccinelle.RESULT = cocci.make_expr("%d" % (value + 1))
// Replace the literal mask with the calculated result.
@plus_one@
expression literal_mask.LITERAL;
position literal_mask.p;
expression add_one.RESULT;
identifier FUNC;
@@
- (FUNC()@p & (LITERAL))
+ prandom_u32_max(RESULT)
@collapse_ret@
type T;
identifier VAR;
expression E;
@@
{
- T VAR;
- VAR = (E);
- return VAR;
+ return E;
}
@drop_var@
type T;
identifier VAR;
@@
{
- T VAR;
... when != VAR
}
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Yury Norov <yury.norov@gmail.com>
Reviewed-by: KP Singh <kpsingh@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz> # for ext4 and sbitmap
Reviewed-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com> # for drbd
Acked-by: Jakub Kicinski <kuba@kernel.org>
Acked-by: Heiko Carstens <hca@linux.ibm.com> # for s390
Acked-by: Ulf Hansson <ulf.hansson@linaro.org> # for mmc
Acked-by: Darrick J. Wong <djwong@kernel.org> # for xfs
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Fixes: 2a734bb8d5 ("UBI: use debugfs for the extra checks knobs")
There is a mistake in docstrings, it should be ubi_debugfs_exit_dev
instead of dbg_debug_exit_dev.
Signed-off-by: Kai Song <songkai01@inspur.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
The snprintf() function returns the number of characters (not
counting the NUL terminator) that it would have printed if we
had space.
This buffer has UBIFS_DFS_DIR_LEN characters plus one extra for
the terminator. Printing UBIFS_DFS_DIR_LEN is okay but anything
higher will result in truncation. Thus the comparison needs to be
change from == to >.
These strings are compile time constants so this patch doesn't
affect runtime.
Fixes: ae380ce047 ("UBIFS: lessen the size of debugging info data structure")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Alexander Dahl <ada@thorsis.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
3bfa7e141b ("fs/seq_file.c: seq_read(): add info message about buggy .next functions")
showed that we don't use seq_file correctly.
So make sure that our ->next function always updates the position.
Fixes: 7bccd12d27 ("ubi: Add debugfs file for tracking PEB state")
Signed-off-by: Richard Weinberger <richard@nod.at>
UBI:
- Fix a regression around producing a anchor PEB for fastmap.
Due to a change in our locking fastmap was unable to produce
fresh anchors an re-used the existing one a way to often.
UBIFS:
- Fixes for endianness. A few places blindly assumed little endian.
- Fix for a memory leak in the orphan code.
- Fix for a possible crash during a commit.
- Revert a wrong bugfix.
JFFS2:
- Revert a bad bugfix in (false positive from a code checking
tool).
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Merge tag 'upstream-5.5-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/ubifs
Pull UBI/UBIFS/JFFS2 updates from Richard Weinberger:
"This pull request contains mostly fixes for UBI, UBIFS and JFFS2:
UBI:
- Fix a regression around producing a anchor PEB for fastmap.
Due to a change in our locking fastmap was unable to produce fresh
anchors an re-used the existing one a way to often.
UBIFS:
- Fixes for endianness. A few places blindly assumed little endian.
- Fix for a memory leak in the orphan code.
- Fix for a possible crash during a commit.
- Revert a wrong bugfix.
JFFS2:
- Revert a bad bugfix (false positive from a code checking tool)"
* tag 'upstream-5.5-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/ubifs:
Revert "jffs2: Fix possible null-pointer dereferences in jffs2_add_frag_to_fragtree()"
ubi: Fix producing anchor PEBs
ubifs: ubifs_tnc_start_commit: Fix OOB in layout_in_gaps
ubifs: do_kill_orphans: Fix a memory leak bug
Revert "ubifs: Fix memory leak bug in alloc_ubifs_info() error path"
ubifs: Fix type of sup->hash_algo
ubifs: Fixed missed le64_to_cpu() in journal
ubifs: Force prandom result to __le32
ubifs: Remove obsolete TODO from dfs_file_write()
ubi: Fix warning static is not at beginning of declaration
ubi: Print skip_check in ubi_dump_vol_info()
It might be interesting, if "skip_check" is set or not, so lets print
this flag in ubi_dump_vol_info() as well.
Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Richard Weinberger <richard@nod.at>
Cc: Boris Brezillon <boris.brezillon@collabora.com>
Cc: Heiko Schocher <hs@denx.de>
Signed-off-by: Richard Weinberger <richard@nod.at>
When calling debugfs functions, there is no need to ever check the
return value. The function can work or not, but the code logic should
never do something different based on this.
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Brian Norris <computersforpeace@gmail.com>
Cc: Marek Vasut <marek.vasut@gmail.com>
Cc: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Vignesh Raghavendra <vigneshr@ti.com>
Cc: Artem Bityutskiy <dedekind1@gmail.com>
Cc: linux-mtd@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Based on 1 normalized pattern(s):
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
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-or-later
has been chosen to replace the boilerplate/reference in 1334 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Richard Fontana <rfontana@redhat.com>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190527070033.113240726@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Add a file under debugfs to allow easy access to the erase count for
each physical erase block on an UBI device. This is useful when
debugging data integrity issues with UBIFS on NAND flash devices.
Signed-off-by: Ben Shelton <ben.shelton@ni.com>
Signed-off-by: Zach Brown <zach.brown@ni.com>
v2:
* If ubi_io_is_bad eraseblk_count_seq_show just returns the err.
* if ubi->lookuptbl returns null, its no longer treated as an error
instead info for that block is not printeded
* Removed check for UBI_MAX_ERASECOUNTER since it is impossible to hit
* Removed block state from print, if a block is printed then it is good and
if it is not printed, then it is bad.
v3:
* Remove errant ! symbol from if statement checking if erase count is valid.
Signed-off-by: Richard Weinberger <richard@nod.at>
My static checker complains that "val" is uninitialized when kstrtoint()
fails.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
We are checking dfs_rootdir for error value or NULL. But in the
conditional ternary operator we returned -ENODEV if dfs_rootdir contains
an error value and returned PTR_ERR(dfs_rootdir) if dfs_rootdir is NULL.
So in the case of dfs_rootdir being NULL we actually assigned 0 to err
and returned it to the caller implying a success.
Lets return -ENODEV when dfs_rootdir is NULL else return
PTR_ERR(dfs_rootdir).
Signed-off-by: Sudip Mukherjee <sudip@vectorindia.org>
Signed-off-by: Richard Weinberger <richard@nod.at>
Emulate random power cuts by switching device to ro after a number of
writes to allow simple power cut testing with nand-sim.
Maximum and minimum number of successful writes before power cut and
what kind of writes (EC header, VID header or none) to interrupt
configurable via debugfs.
Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
Signed-off-by: Richard Weinberger <richard@nod.at>
Using this debugfs knob fastmap self checks can be controlled.
Signed-off-by: Richard Weinberger <richard@nod.at>
Reviewed-by: Tanya Brokhman <tlinder@codeaurora.org>
If there is more then one UBI device mounted, there is no way to
distinguish between messages from different UBI devices.
Add device number to all ubi layer message types.
The R/O block driver messages were replaced by pr_* since
ubi_device structure is not used by it.
Amended a bit by Artem.
Signed-off-by: Tanya Brokhman <tlinder@codeaurora.org>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
ubi_debug_info struct was dynamically allocated which
is always suboptimal, for it tends to fragment memory
and make the code error-prone.
Fix this by embedding it in ubi_device struct.
Signed-off-by: Ezequiel Garcia <elezegarcia@gmail.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Commit "e9b4cf2 UBI: fix debugfs-less systems support" fixed one
regression but introduced a different regression - the debugfs is now always
compiled out. Root cause: IS_ENABLED() arguments should be used with the
CONFIG_* prefix.
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Commit "aa44d1d UBI: remove Kconfig debugging option" broke UBI and it
refuses to initialize if debugfs (CONFIG_DEBUG_FS) is disabled. I incorrectly
assumed that debugfs files creation function will return success if debugfs
is disabled, but they actually return -ENODEV. This patch fixes the issue.
Reported-by: Paul Parsons <lost.distance@yahoo.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Tested-by: Paul Parsons <lost.distance@yahoo.com>
After re-naming the 'struct ubi_scan_volume' we should adjust all variables
named 'sv' to something else, because 'sv' stands for "scanning volume".
Let's rename it to 'av' which stands for "attaching volume" which is
a bit more consistent and has the same length, which makes re-naming easy.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@linux.intel.com>
After re-naming the 'struct ubi_scan_info' we should adjust all variables
named 'si' to something else, because 'si' stands for "scanning info".
Let's rename it to 'ai' which stands for "attaching info" which is
a bit more consistent and has the same length, which makes re-naming easy.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@linux.intel.com>
After re-naming the 'struct ubi_scan_leb' we should adjust all variables
named 'seb' to something else, because 'seb' stands for "scanning eraseblock".
Let's rename it to 'aeb' which stands for "attaching eraseblock" which is
a bit more consistend and has the same length.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@linux.intel.com>
Rename 'struct ubi_scan_volume' to 'struct ubi_ainf_volume'. This is part
of the code re-structuring I am trying to do in order to add fastmap
in a more logical way. Fastmap can share a lot with scanning, including
the attach-time data structures, which all now have "scan" word in the
name. Let's get rid of this word and use "ainf" instead which stands
for "attach information". It has the same length as "scan" so re-naming
is trivial.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@linux.intel.com>
Rename 'struct ubi_scan_leb' to 'struct ubi_ainf_leb'. This is part
of the code re-structuring I am trying to do in order to add fastmap
in a more logical way. Fastmap can share a lot with scanning, including
the attach-time data structures, which all now have "scan" word in the
name. Let's get rid of this word and use "ainf" instead which stands
for "attach information". It has the same length as "scan" so re-naming
is trivial.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@linux.intel.com>
This patch kills the UBI debugging Kconfig option completely and makes all the
debugging stuff to be always compiled-in. It was pain in the neck to maintain
this useless option because all users I am aware of have debugging enabled
anyway - how else will you diagnose errors otherwise?
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
I am going to remove the "UBI debugging" compilation option and make the
debugging stuff to be always compiled it. This patch is a preparation
which renames 'ubi_dbg_dump_mkvol_req()' to 'ubi_dump_mkvol_req()'.
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
I am going to remove the "UBI debugging" compilation option and make the
debugging stuff to be always compiled it. This patch is a preparation
which renames 'ubi_dbg_dump_seb()' to 'ubi_dump_seb()'.
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
I am going to remove the "UBI debugging" compilation option and make the
debugging stuff to be always compiled it. This patch is a preparation
which renames 'ubi_dbg_dump_sv()' to 'ubi_dump_sv()'.
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
I am going to remove the "UBI debugging" compilation option and make the
debugging stuff to be always compiled it. This patch is a preparation
which renames 'ubi_dbg_dump_vtbl_record()' to 'ubi_dump_vtbl_record()'.
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
I am going to remove the "UBI debugging" compilation option and make the
debugging stuff to be always compiled it. This patch is a preparation
which renames 'ubi_dbg_dump_vol_info()' to 'ubi_dump_vol_info()'.
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
UBI (and UBIFS) are a bit over-engineered WRT debugging. The idea was to
link as few as possible when debugging is disabled, but the downside is
that most people produce bug reports which are difficult to understand.
Always dump the VID and EC headers' contents in case of errors when it
is helpful.
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
UBI (and UBIFS) are a bit over-engineered WRT debugging. The idea was to
link as few as possible when debugging is disabled, but the downside is
that most people produce bug reports which are difficult to understand.
Always dump the flash contents in case of errors, not only when debugging is
enabled.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@linux.intel.com>
Many users of debugfs copy the implementation of default_open() when
they want to support a custom read/write function op. This leads to a
proliferation of the default_open() implementation across the entire
tree.
Now that the common implementation has been consolidated into libfs we
can replace all the users of this function with simple_open().
This replacement was done with the following semantic patch:
<smpl>
@ open @
identifier open_f != simple_open;
identifier i, f;
@@
-int open_f(struct inode *i, struct file *f)
-{
(
-if (i->i_private)
-f->private_data = i->i_private;
|
-f->private_data = i->i_private;
)
-return 0;
-}
@ has_open depends on open @
identifier fops;
identifier open.open_f;
@@
struct file_operations fops = {
...
-.open = open_f,
+.open = simple_open,
...
};
</smpl>
[akpm@linux-foundation.org: checkpatch fixes]
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Julia Lawall <Julia.Lawall@lip6.fr>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Kill the UBI 'debug_tsts' module parameter and switch to debugfs. Create
per-test mode files there. E.g., to enable bit-flips emulation you may just do:
echo 1 > /sys/kernel/debug/ubi/ubi0/tst_emulate_bitflips
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This patch introduces debugfs support to UBI. All the UBI stuff is kept in the
"ubi" debugfs directory, which contains per-UBI device "ubi/ubiX"
sub-directories, containing debugging files. This file also creates
"ubi/ubiX/chk_gen" and "ubi/ubiX/chk_io" knobs for switching general and I/O
extra checks on and off. And it removes the 'debug_chks' UBI module parameters.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Remove custom dynamic prints and the module parameter to toggle them and use
the generic kernel dynamic printk infrastructure.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Fix checkpatch.pl errors and warnings:
* space before tab
* line over 80 characters
* include linux/ioctl.h instead of asm/ioctl.h
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Similarly to the debugging checks and message, make the test modes
be dynamically selected via the "debug_tsts" module parameter or
via the "/sys/module/ubi/parameters/debug_tsts" sysfs file. This
is consistent with UBIFS as well.
And now, since all the Kconfig knobs became dynamic, we can remove
the Kconfig.debug file completely.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This patch adds a possibility to dynamically switch UBI self-checks
on and off, instead of toggling them compile-time from the configuration
menu. This is much more flexible, and consistent with UBIFS, and this
also simplifies UBI Kconfig menu and the code.
This patch introduces two levels of self-checks - general, which
includes all self-checks which are relatively fast, and I/O, which
includes write-verify checks and erase-verify checks, which are
relatively slow and involve flash I/O.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This patch adds a possibility to dynamically select UBI debugging
messages, instead of selecting them compile-time from the configuration
menu. This is much more flexible, and consistent with UBIFS, and this
also simplifies UBI Kconfig menu and the code.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Useful for debugging problems, compiled in only if UBI debugging
is enabled. This patch also makes the UBI writing function dump
the flash if it fails to write.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
An image sequence number is added to the UBI erase-counter header
to be able determine if the root file system contains a mixture
of old and new images (because the flashing failed to complete).
A change to nolo is also needed for this to take effect.
Signed-off-by: Adrian Hunter <adrian.hunter@nokia.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Before UBI got into mainline, there was a slight flash format
change - we did not have sequence number support, then added it.
We have carried full support of those ancient images till this
moment. Now the support is removed, well, not fully removed.
Now UBI will support only _clean_ old images, which were cleanly
detached last time (just before kernel upgrade). This is most
likely the case.
But we will not support unclean ancient images. Surprisingly,
this allows us to remove a big chunk of legacy code.
And the same should be true for downgrading: clean images should
downgrade fine, but unclean ones will not.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
When volume creation fails, we have to set ubi->volumes[vol_id]
back to NULL.
This patch also tweaks some debugging stuff.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Kill UBI's homegrown endianess handling and replace it with
the standard kernel endianess handling.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
UBI (Latin: "where?") manages multiple logical volumes on a single
flash device, specifically supporting NAND flash devices. UBI provides
a flexible partitioning concept which still allows for wear-levelling
across the whole flash device.
In a sense, UBI may be compared to the Logical Volume Manager
(LVM). Whereas LVM maps logical sector numbers to physical HDD sector
numbers, UBI maps logical eraseblocks to physical eraseblocks.
More information may be found at
http://www.linux-mtd.infradead.org/doc/ubi.html
Partitioning/Re-partitioning
An UBI volume occupies a certain number of erase blocks. This is
limited by a configured maximum volume size, which could also be
viewed as the partition size. Each individual UBI volume's size can
be changed independently of the other UBI volumes, provided that the
sum of all volume sizes doesn't exceed a certain limit.
UBI supports dynamic volumes and static volumes. Static volumes are
read-only and their contents are protected by CRC check sums.
Bad eraseblocks handling
UBI transparently handles bad eraseblocks. When a physical
eraseblock becomes bad, it is substituted by a good physical
eraseblock, and the user does not even notice this.
Scrubbing
On a NAND flash bit flips can occur on any write operation,
sometimes also on read. If bit flips persist on the device, at first
they can still be corrected by ECC, but once they accumulate,
correction will become impossible. Thus it is best to actively scrub
the affected eraseblock, by first copying it to a free eraseblock
and then erasing the original. The UBI layer performs this type of
scrubbing under the covers, transparently to the UBI volume users.
Erase Counts
UBI maintains an erase count header per eraseblock. This frees
higher-level layers (like file systems) from doing this and allows
for centralized erase count management instead. The erase counts are
used by the wear-levelling algorithm in the UBI layer. The algorithm
itself is exchangeable.
Booting from NAND
For booting directly from NAND flash the hardware must at least be
capable of fetching and executing a small portion of the NAND
flash. Some NAND flash controllers have this kind of support. They
usually limit the window to a few kilobytes in erase block 0. This
"initial program loader" (IPL) must then contain sufficient logic to
load and execute the next boot phase.
Due to bad eraseblocks, which may be randomly scattered over the
flash device, it is problematic to store the "secondary program
loader" (SPL) statically. Also, due to bit-flips it may become
corrupted over time. UBI allows to solve this problem gracefully by
storing the SPL in a small static UBI volume.
UBI volumes vs. static partitions
UBI volumes are still very similar to static MTD partitions:
* both consist of eraseblocks (logical eraseblocks in case of UBI
volumes, and physical eraseblocks in case of static partitions;
* both support three basic operations - read, write, erase.
But UBI volumes have the following advantages over traditional
static MTD partitions:
* there are no eraseblock wear-leveling constraints in case of UBI
volumes, so the user should not care about this;
* there are no bit-flips and bad eraseblocks in case of UBI volumes.
So, UBI volumes may be considered as flash devices with relaxed
restrictions.
Where can it be found?
Documentation, kernel code and applications can be found in the MTD
gits.
What are the applications for?
The applications help to create binary flash images for two purposes: pfi
files (partial flash images) for in-system update of UBI volumes, and plain
binary images, with or without OOB data in case of NAND, for a manufacturing
step. Furthermore some tools are/and will be created that allow flash content
analysis after a system has crashed..
Who did UBI?
The original ideas, where UBI is based on, were developed by Andreas
Arnez, Frank Haverkamp and Thomas Gleixner. Josh W. Boyer and some others
were involved too. The implementation of the kernel layer was done by Artem
B. Bityutskiy. The user-space applications and tools were written by Oliver
Lohmann with contributions from Frank Haverkamp, Andreas Arnez, and Artem.
Joern Engel contributed a patch which modifies JFFS2 so that it can be run on
a UBI volume. Thomas Gleixner did modifications to the NAND layer. Alexander
Schmidt made some testing work as well as core functionality improvements.
Signed-off-by: Artem B. Bityutskiy <dedekind@linutronix.de>
Signed-off-by: Frank Haverkamp <haver@vnet.ibm.com>
