To make it possible to put struct bin_attribute into read-only memory,
the sysfs core has to stop passing mutable pointers to the read() and
write() callbacks.
As there are numerous implementors of these callbacks throughout the
tree it's not possible to change all of them at once.
To enable a step-by-step transition, add new variants of the read() and
write() callbacks which differ only in the constness of the struct
bin_attribute argument.
As most binary attributes are defined through macros, extend these
macros to transparently handle both variants of callbacks to minimize
the churn during the transition.
As soon as all handlers are switch to the const variant, the non-const
one can be removed together with the transition machinery.
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Acked-by: Krzysztof Wilczyński <kw@linux.com>
Link: https://lore.kernel.org/r/20241103-sysfs-const-bin_attr-v2-9-71110628844c@weissschuh.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Several drivers need to dynamically calculate the size of an binary
attribute. Currently this is done by assigning attr->size from the
is_bin_visible() callback.
This has drawbacks:
* It is not documented.
* A single attribute can be instantiated multiple times, overwriting the
shared size field.
* It prevents the structure to be moved to read-only memory.
Introduce a new dedicated callback to calculate the size of the
attribute.
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Acked-by: Krzysztof Wilczyński <kw@linux.com>
Link: https://lore.kernel.org/r/20241103-sysfs-const-bin_attr-v2-2-71110628844c@weissschuh.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
When drivers expose a bin_attribute in sysfs which is backed by a buffer
in memory, a common pattern is to set the @private and @size members in
struct bin_attribute to the buffer's location and size.
The ->read() callback then merely consists of a single memcpy() call.
It's not even necessary to perform bounds checks as these are already
handled by sysfs_kf_bin_read().
However each driver is so far providing its own ->read() implementation.
The pattern is sufficiently frequent to merit a public helper, so add
sysfs_bin_attr_simple_read() as well as BIN_ATTR_SIMPLE_RO() and
BIN_ATTR_SIMPLE_ADMIN_RO() macros to ease declaration of such
bin_attributes and reduce LoC and .text section size.
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/5ed62b197a442ec6db53d8746d9d806dd0576e2d.1712410202.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The sysfs_break_active_protection() routine has an obvious reference
leak in its error path. If the call to kernfs_find_and_get() fails then
kn will be NULL, so the companion sysfs_unbreak_active_protection()
routine won't get called (and would only cause an access violation by
trying to dereference kn->parent if it was called). As a result, the
reference to kobj acquired at the start of the function will never be
released.
Fix the leak by adding an explicit kobject_put() call when kn is NULL.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Fixes: 2afc9166f7 ("scsi: sysfs: Introduce sysfs_{un,}break_active_protection()")
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: stable@vger.kernel.org
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/8a4d3f0f-c5e3-4b70-a188-0ca433f9e6f9@rowland.harvard.edu
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
These functions take a struct attribute_group as an input which has an
optional .name field. These functions rely on the .name field being
populated and do not check if its null. They pass this name into other
functions, eventually leading to a null pointer dereference.
This change simply updates the documentation of the function to make
this requirement clear.
Signed-off-by: Rohan Kollambalath <rkollamb@digi.com>
Link: https://lore.kernel.org/r/20240211223634.2103665-1-rohankollambalath@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
It turns out that arch/x86/events/intel/core.c makes use of "empty"
attributes.
static struct attribute *empty_attrs;
__init int intel_pmu_init(void)
{
struct attribute **extra_skl_attr = &empty_attrs;
struct attribute **extra_attr = &empty_attrs;
struct attribute **td_attr = &empty_attrs;
struct attribute **mem_attr = &empty_attrs;
struct attribute **tsx_attr = &empty_attrs;
...
That breaks the assumption __first_visible() that expects that if
grp->attrs is set then grp->attrs[0] must also be set and results in
backtraces like:
BUG: kernel NULL pointer dereference, address: 00rnel mode
#PF: error_code(0x0000) - not-present ] PREEMPT SMP NOPTI
CPU: 1 PID: 1 Comm: swapper/IP: 0010:exra_is_visible+0x14/0x20
? exc_page_fault+0x68/0x190
internal_create_groups+0x42/0xa0
pmu_dev_alloc+0xc0/0xe0
perf_event_sysfs_init+0x580000000000 ]---
RIP: 0010:exra_is_visible+0x14/0
Check for non-empty attributes array before calling is_visible().
Reported-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Closes: https://github.com/thesofproject/linux/pull/4799#issuecomment-1958537212
Fixes: 70317fd24b ("sysfs: Introduce a mechanism to hide static attribute_groups")
Cc: Marc Herbert <marc.herbert@intel.com>
Cc: Rafael J. Wysocki <rafael@kernel.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Tested-by: Marc Herbert <marc.herbert@intel.com>
Link: https://lore.kernel.org/r/170863445442.1479840.1818801787239831650.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Add a mechanism for named attribute_groups to hide their directory at
sysfs_update_group() time, or otherwise skip emitting the group
directory when the group is first registered. It piggybacks on
is_visible() in a similar manner as SYSFS_PREALLOC, i.e. special flags
in the upper bits of the returned mode. To use it, specify a symbol
prefix to DEFINE_SYSFS_GROUP_VISIBLE(), and then pass that same prefix
to SYSFS_GROUP_VISIBLE() when assigning the @is_visible() callback:
DEFINE_SYSFS_GROUP_VISIBLE($prefix)
struct attribute_group $prefix_group = {
.name = $name,
.is_visible = SYSFS_GROUP_VISIBLE($prefix),
};
SYSFS_GROUP_VISIBLE() expects a definition of $prefix_group_visible()
and $prefix_attr_visible(), where $prefix_group_visible() just returns
true / false and $prefix_attr_visible() behaves as normal.
The motivation for this capability is to centralize PCI device
authentication in the PCI core with a named sysfs group while keeping
that group hidden for devices and platforms that do not meet the
requirements. In a PCI topology, most devices will not support
authentication, a small subset will support just PCI CMA (Component
Measurement and Authentication), a smaller subset will support PCI CMA +
PCIe IDE (Link Integrity and Encryption), and only next generation
server hosts will start to include a platform TSM (TEE Security
Manager).
Without this capability the alternatives are:
* Check if all attributes are invisible and if so, hide the directory.
Beyond trouble getting this to work [1], this is an ABI change for
scenarios if userspace happens to depend on group visibility absent any
attributes. I.e. this new capability avoids regression since it does
not retroactively apply to existing cases.
* Publish an empty /sys/bus/pci/devices/$pdev/tsm/ directory for all PCI
devices (i.e. for the case when TSM platform support is present, but
device support is absent). Unfortunate that this will be a vestigial
empty directory in the vast majority of cases.
* Reintroduce usage of runtime calls to sysfs_{create,remove}_group()
in the PCI core. Bjorn has already indicated that he does not want to
see any growth of pci_sysfs_init() [2].
* Drop the named group and simulate a directory by prefixing all
TSM-related attributes with "tsm_". Unfortunate to not use the naming
capability of a sysfs group as intended.
In comparison, there is a small potential for regression if for some
reason an @is_visible() callback had dependencies on how many times it
was called. Additionally, it is no longer an error to update a group
that does not have its directory already present, and it is no longer a
WARN() to remove a group that was never visible.
Link: https://lore.kernel.org/all/2024012321-envious-procedure-4a58@gregkh/ [1]
Link: https://lore.kernel.org/linux-pci/20231019200110.GA1410324@bhelgaas/ [2]
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/2024013028-deflator-flaring-ec62@gregkh
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
As of now, seeking in sysfs files is handled by generic_file_llseek().
There are situations where one may want to customize seeking logic:
- Many sysfs entries are fixed files while generic_file_llseek() accepts
past-the-end positions. Not only being useless by itself, this
also means a bug in userspace code will trigger not at lseek(), but at
some later point making debugging harder.
- generic_file_llseek() relies on f_mapping->host to get the file size
which might not be correct for all sysfs entries.
See commit 636b21b501 ("PCI: Revoke mappings like devmem") as an example.
Implement llseek method to override this behavior at sysfs attribute
level. The method is optional, and if it is absent,
generic_file_llseek() is called to preserve backwards compatibility.
Signed-off-by: Valentine Sinitsyn <valesini@yandex-team.ru>
Link: https://lore.kernel.org/r/20230925084013.309399-1-valesini@yandex-team.ru
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Most sysfs attributes are statically defined, the goal with this design
being to be able to move all the filesystem description into read-only
memory. Anyway, it may be relevant in some cases to populate attributes
at run time. This leads to situation where an attribute may or may not be
present depending on conditions which are not known at compile
time, up to the point where no attribute at all gets added in a folder
which then becomes "sometimes" empty. Problem is, providing an attribute
group with a name and without .[bin_]attrs members will be loudly
refused by the core, leading in most cases to a device registration
failure.
The simple way to support such situation right now is to dynamically
allocate an empty attribute array, which is:
* a (small) waste of space
* a waste of time
* disturbing, to say the least, as an empty sysfs folder will be created
anyway.
Another (even worse) possibility would be to dynamically overwrite a
member of the attribute_group list, hopefully the last, which is also
supposed to remain in the read-only section.
In order to avoid these hackish situations, while still giving a little
bit of flexibility, we might just check the validity of the .[bin_]attrs
list and, if empty, just skip the attribute group creation instead of
failing. This way, developers will not be tempted to workaround the
core with useless allocations or strange writes on supposedly read-only
structures.
The content of the WARN() message is kept but turned into a debug
message in order to help developers understanding why their sysfs
folders might now silently fail to be created.
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Message-ID: <20230614063018.2419043-3-miquel.raynal@bootlin.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The purpose of the if/else block is to select the right sysfs directory
entry to be used for the files creation. At a first look when you have
the file in front of you, it really seems like the "create_files()"
lines right after the block are badly indented and the "else" does not
guard. In practice the code is correct but lacks curly brackets to show
where the big if/else block actually ends. Add these brackets to comply
with the current kernel coding style and to ease the understanding of
the whole logic.
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Message-ID: <20230614063018.2419043-2-miquel.raynal@bootlin.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Now that all in-kernel users of default_attrs for the kobj_type are gone
and converted to properly use the default_groups pointer instead, it can
be safely removed.
There is one standard way to create sysfs files in a kobj_type, and not
two like before, causing confusion as to which should be used.
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Link: https://lore.kernel.org/r/20220106133151.607703-1-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
sysfs: Allow deferred execution of iomem_get_mapping()
Tag for toerh trees/branches to pull from in order to have a stable base
to build off of for the "Allow deferred execution of
iomem_get_mapping()" set of sysfs changes
Link: https://lore.kernel.org/r/20210729233235.1508920-1-kw@linux.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tag 'sysfs_defferred_iomem_get_mapping-5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core:
sysfs: Rename struct bin_attribute member to f_mapping
sysfs: Invoke iomem_get_mapping() from the sysfs open callback
There are two users of iomem_get_mapping(), the struct file and struct
bin_attribute. The former has a member called "f_mapping" and the
latter has a member called "mapping", and both are poniters to struct
address_space.
Rename struct bin_attribute member to "f_mapping" to keep both meaning
and the usage consistent with other users of iomem_get_mapping().
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Krzysztof Wilczyński <kw@linux.com>
Link: https://lore.kernel.org/r/20210729233235.1508920-3-kw@linux.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Defer invocation of the iomem_get_mapping() to the sysfs open callback
so that it can be executed as needed when the binary sysfs object has
been accessed.
To do that, convert the "mapping" member of the struct bin_attribute
from a pointer to the struct address_space into a function pointer with
a signature that requires the same return type, and then updates the
sysfs_kf_bin_open() to invoke provided function should the function
pointer be valid.
Also, convert every invocation of iomem_get_mapping() into a function
pointer assignment, therefore allowing for the iomem_get_mapping()
invocation to be deferred to when the sysfs open callback runs.
Thus, this change removes the need for the fs_initcalls to complete
before any other sub-system that uses the iomem_get_mapping() would be
able to invoke it safely without leading to a failure and an Oops
related to an invalid iomem_get_mapping() access.
Suggested-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Krzysztof Wilczyński <kw@linux.com>
Link: https://lore.kernel.org/r/20210729233235.1508920-2-kw@linux.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
