linux.git/kernel/bpf/Makefile, branch v6.18.21 Clone of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git bpf: callchain sensitive stack liveness tracking using CFG 2025-09-19T16:27:23+00:00 Eduard Zingerman eddyz87@gmail.com 2025-09-19T02:18:39+00:00 b3698c356ad92bcdb9920655bc9df02a2a8946f9 This commit adds a flow-sensitive, context-sensitive, path-insensitive data flow analysis for live stack slots: - flow-sensitive: uses program control flow graph to compute data flow values; - context-sensitive: collects data flow values for each possible call chain in a program; - path-insensitive: does not distinguish between separate control flow graph paths reaching the same instruction. Compared to the current path-sensitive analysis, this approach trades some precision for not having to enumerate every path in the program. This gives a theoretical capability to run the analysis before main verification pass. See cover letter for motivation. The basic idea is as follows: - Data flow values indicate stack slots that might be read and stack slots that are definitely written. - Data flow values are collected for each (call chain, instruction number) combination in the program. - Within a subprogram, data flow values are propagated using control flow graph. - Data flow values are transferred from entry instructions of callee subprograms to call sites in caller subprograms. In other words, a tree of all possible call chains is constructed. Each node of this tree represents a subprogram. Read and write marks are collected for each instruction of each node. Live stack slots are first computed for lower level nodes. Then, information about outer stack slots that might be read or are definitely written by a subprogram is propagated one level up, to the corresponding call instructions of the upper nodes. Procedure repeats until root node is processed. In the absence of value range analysis, stack read/write marks are collected during main verification pass, and data flow computation is triggered each time verifier.c:states_equal() needs to query the information. Implementation details are documented in kernel/bpf/liveness.c. Quantitative data about verification performance changes and memory consumption is in the cover letter. Signed-off-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/r/20250918-callchain-sensitive-liveness-v3-6-c3cd27bacc60@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> 
This commit adds a flow-sensitive, context-sensitive, path-insensitive
data flow analysis for live stack slots:
- flow-sensitive: uses program control flow graph to compute data flow
  values;
- context-sensitive: collects data flow values for each possible call
  chain in a program;
- path-insensitive: does not distinguish between separate control flow
  graph paths reaching the same instruction.

Compared to the current path-sensitive analysis, this approach trades
some precision for not having to enumerate every path in the program.
This gives a theoretical capability to run the analysis before main
verification pass. See cover letter for motivation.

The basic idea is as follows:
- Data flow values indicate stack slots that might be read and stack
  slots that are definitely written.
- Data flow values are collected for each
  (call chain, instruction number) combination in the program.
- Within a subprogram, data flow values are propagated using control
  flow graph.
- Data flow values are transferred from entry instructions of callee
  subprograms to call sites in caller subprograms.

In other words, a tree of all possible call chains is constructed.
Each node of this tree represents a subprogram. Read and write marks
are collected for each instruction of each node. Live stack slots are
first computed for lower level nodes. Then, information about outer
stack slots that might be read or are definitely written by a
subprogram is propagated one level up, to the corresponding call
instructions of the upper nodes. Procedure repeats until root node is
processed.

In the absence of value range analysis, stack read/write marks are
collected during main verification pass, and data flow computation is
triggered each time verifier.c:states_equal() needs to query the
information.

Implementation details are documented in kernel/bpf/liveness.c.
Quantitative data about verification performance changes and memory
consumption is in the cover letter.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20250918-callchain-sensitive-liveness-v3-6-c3cd27bacc60@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
rqspinlock: Choose trylock fallback for NMI waiters 2025-09-09T22:10:28+00:00 Kumar Kartikeya Dwivedi memxor@gmail.com 2025-09-09T18:49:59+00:00 0d80e7f951be1bdd08d328fd87694be0d6e8aaa8 Currently, out of all 3 types of waiters in the rqspinlock slow path (i.e., pending bit waiter, wait queue head waiter, and wait queue non-head waiter), only the pending bit waiter and wait queue head waiters apply deadlock checks and a timeout on their waiting loop. The assumption here was that the wait queue head's forward progress would be sufficient to identify cases where the lock owner or pending bit waiter is stuck, and non-head waiters relying on the head waiter would prove to be sufficient for their own forward progress. However, the head waiter itself can be preempted by a non-head waiter for the same lock (AA) or a different lock (ABBA) in a manner that impedes its forward progress. In such a case, non-head waiters not performing deadlock and timeout checks becomes insufficient, and the system can enter a state of lockup. This is typically not a concern with non-NMI lock acquisitions, as lock holders which in run in different contexts (IRQ, non-IRQ) use "irqsave" variants of the lock APIs, which naturally excludes such lock holders from preempting one another on the same CPU. It might seem likely that a similar case may occur for rqspinlock when programs are attached to contention tracepoints (begin, end), however, these tracepoints either precede the enqueue into the wait queue, or succeed it, therefore cannot be used to preempt a head waiter's waiting loop. We must still be careful against nested kprobe and fentry programs that may attach to the middle of the head's waiting loop to stall forward progress and invoke another rqspinlock acquisition that proceeds as a non-head waiter. To this end, drop CC_FLAGS_FTRACE from the rqspinlock.o object file. For now, this issue is resolved by falling back to a repeated trylock on the lock word from NMI context, while performing the deadlock checks to break out early in case forward progress is impossible, and use the timeout as a final fallback. A more involved fix to terminate the queue when such a condition occurs will be made as a follow up. A selftest to stress this aspect of nested NMI/non-NMI locking attempts will be added in a subsequent patch to the bpf-next tree when this fix lands and trees are synchronized. Reported-by: Josef Bacik <josef@toxicpanda.com> Fixes: 164c246571e9 ("rqspinlock: Protect waiters in queue from stalls") Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20250909184959.3509085-1-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> 
Currently, out of all 3 types of waiters in the rqspinlock slow path
(i.e., pending bit waiter, wait queue head waiter, and wait queue
non-head waiter), only the pending bit waiter and wait queue head
waiters apply deadlock checks and a timeout on their waiting loop. The
assumption here was that the wait queue head's forward progress would be
sufficient to identify cases where the lock owner or pending bit waiter
is stuck, and non-head waiters relying on the head waiter would prove to
be sufficient for their own forward progress.

However, the head waiter itself can be preempted by a non-head waiter
for the same lock (AA) or a different lock (ABBA) in a manner that
impedes its forward progress. In such a case, non-head waiters not
performing deadlock and timeout checks becomes insufficient, and the
system can enter a state of lockup.

This is typically not a concern with non-NMI lock acquisitions, as lock
holders which in run in different contexts (IRQ, non-IRQ) use "irqsave"
variants of the lock APIs, which naturally excludes such lock holders
from preempting one another on the same CPU.

It might seem likely that a similar case may occur for rqspinlock when
programs are attached to contention tracepoints (begin, end), however,
these tracepoints either precede the enqueue into the wait queue, or
succeed it, therefore cannot be used to preempt a head waiter's waiting
loop.

We must still be careful against nested kprobe and fentry programs that
may attach to the middle of the head's waiting loop to stall forward
progress and invoke another rqspinlock acquisition that proceeds as a
non-head waiter. To this end, drop CC_FLAGS_FTRACE from the rqspinlock.o
object file.

For now, this issue is resolved by falling back to a repeated trylock on
the lock word from NMI context, while performing the deadlock checks to
break out early in case forward progress is impossible, and use the
timeout as a final fallback.

A more involved fix to terminate the queue when such a condition occurs
will be made as a follow up. A selftest to stress this aspect of nested
NMI/non-NMI locking attempts will be added in a subsequent patch to the
bpf-next tree when this fix lands and trees are synchronized.

Reported-by: Josef Bacik <josef@toxicpanda.com>
Fixes: 164c246571e9 ("rqspinlock: Protect waiters in queue from stalls")
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20250909184959.3509085-1-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
bpf: Introduce BPF standard streams 2025-07-04T02:30:06+00:00 Kumar Kartikeya Dwivedi memxor@gmail.com 2025-07-03T20:48:08+00:00 5ab154f1463a111e1dc8fd5d31eaa7a2a71fe2e6 Add support for a stream API to the kernel and expose related kfuncs to BPF programs. Two streams are exposed, BPF_STDOUT and BPF_STDERR. These can be used for printing messages that can be consumed from user space, thus it's similar in spirit to existing trace_pipe interface. The kernel will use the BPF_STDERR stream to notify the program of any errors encountered at runtime. BPF programs themselves may use both streams for writing debug messages. BPF library-like code may use BPF_STDERR to print warnings or errors on misuse at runtime. The implementation of a stream is as follows. Everytime a message is emitted from the kernel (directly, or through a BPF program), a record is allocated by bump allocating from per-cpu region backed by a page obtained using alloc_pages_nolock(). This ensures that we can allocate memory from any context. The eventual plan is to discard this scheme in favor of Alexei's kmalloc_nolock() [0]. This record is then locklessly inserted into a list (llist_add()) so that the printing side doesn't require holding any locks, and works in any context. Each stream has a maximum capacity of 4MB of text, and each printed message is accounted against this limit. Messages from a program are emitted using the bpf_stream_vprintk kfunc, which takes a stream_id argument in addition to working otherwise similar to bpf_trace_vprintk. The bprintf buffer helpers are extracted out to be reused for printing the string into them before copying it into the stream, so that we can (with the defined max limit) format a string and know its true length before performing allocations of the stream element. For consuming elements from a stream, we expose a bpf(2) syscall command named BPF_PROG_STREAM_READ_BY_FD, which allows reading data from the stream of a given prog_fd into a user space buffer. The main logic is implemented in bpf_stream_read(). The log messages are queued in bpf_stream::log by the bpf_stream_vprintk kfunc, and then pulled and ordered correctly in the stream backlog. For this purpose, we hold a lock around bpf_stream_backlog_peek(), as llist_del_first() (if we maintained a second lockless list for the backlog) wouldn't be safe from multiple threads anyway. Then, if we fail to find something in the backlog log, we splice out everything from the lockless log, and place it in the backlog log, and then return the head of the backlog. Once the full length of the element is consumed, we will pop it and free it. The lockless list bpf_stream::log is a LIFO stack. Elements obtained using a llist_del_all() operation are in LIFO order, thus would break the chronological ordering if printed directly. Hence, this batch of messages is first reversed. Then, it is stashed into a separate list in the stream, i.e. the backlog_log. The head of this list is the actual message that should always be returned to the caller. All of this is done in bpf_stream_backlog_fill(). From the kernel side, the writing into the stream will be a bit more involved than the typical printk. First, the kernel typically may print a collection of messages into the stream, and parallel writers into the stream may suffer from interleaving of messages. To ensure each group of messages is visible atomically, we can lift the advantage of using a lockless list for pushing in messages. To enable this, we add a bpf_stream_stage() macro, and require kernel users to use bpf_stream_printk statements for the passed expression to write into the stream. Underneath the macro, we have a message staging API, where a bpf_stream_stage object on the stack accumulates the messages being printed into a local llist_head, and then a commit operation splices the whole batch into the stream's lockless log list. This is especially pertinent for rqspinlock deadlock messages printed to program streams. After this change, we see each deadlock invocation as a non-interleaving contiguous message without any confusion on the reader's part, improving their user experience in debugging the fault. While programs cannot benefit from this staged stream writing API, they could just as well hold an rqspinlock around their print statements to serialize messages, hence this is kept kernel-internal for now. Overall, this infrastructure provides NMI-safe any context printing of messages to two dedicated streams. Later patches will add support for printing splats in case of BPF arena page faults, rqspinlock deadlocks, and cond_break timeouts, and integration of this facility into bpftool for dumping messages to user space. [0]: https://lore.kernel.org/bpf/20250501032718.65476-1-alexei.starovoitov@gmail.com Reviewed-by: Eduard Zingerman <eddyz87@gmail.com> Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20250703204818.925464-3-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> 
Add support for a stream API to the kernel and expose related kfuncs to
BPF programs. Two streams are exposed, BPF_STDOUT and BPF_STDERR. These
can be used for printing messages that can be consumed from user space,
thus it's similar in spirit to existing trace_pipe interface.

The kernel will use the BPF_STDERR stream to notify the program of any
errors encountered at runtime. BPF programs themselves may use both
streams for writing debug messages. BPF library-like code may use
BPF_STDERR to print warnings or errors on misuse at runtime.

The implementation of a stream is as follows. Everytime a message is
emitted from the kernel (directly, or through a BPF program), a record
is allocated by bump allocating from per-cpu region backed by a page
obtained using alloc_pages_nolock(). This ensures that we can allocate
memory from any context. The eventual plan is to discard this scheme in
favor of Alexei's kmalloc_nolock() [0].

This record is then locklessly inserted into a list (llist_add()) so
that the printing side doesn't require holding any locks, and works in
any context. Each stream has a maximum capacity of 4MB of text, and each
printed message is accounted against this limit.

Messages from a program are emitted using the bpf_stream_vprintk kfunc,
which takes a stream_id argument in addition to working otherwise
similar to bpf_trace_vprintk.

The bprintf buffer helpers are extracted out to be reused for printing
the string into them before copying it into the stream, so that we can
(with the defined max limit) format a string and know its true length
before performing allocations of the stream element.

For consuming elements from a stream, we expose a bpf(2) syscall command
named BPF_PROG_STREAM_READ_BY_FD, which allows reading data from the
stream of a given prog_fd into a user space buffer. The main logic is
implemented in bpf_stream_read(). The log messages are queued in
bpf_stream::log by the bpf_stream_vprintk kfunc, and then pulled and
ordered correctly in the stream backlog.

For this purpose, we hold a lock around bpf_stream_backlog_peek(), as
llist_del_first() (if we maintained a second lockless list for the
backlog) wouldn't be safe from multiple threads anyway. Then, if we
fail to find something in the backlog log, we splice out everything from
the lockless log, and place it in the backlog log, and then return the
head of the backlog. Once the full length of the element is consumed, we
will pop it and free it.

The lockless list bpf_stream::log is a LIFO stack. Elements obtained
using a llist_del_all() operation are in LIFO order, thus would break
the chronological ordering if printed directly. Hence, this batch of
messages is first reversed. Then, it is stashed into a separate list in
the stream, i.e. the backlog_log. The head of this list is the actual
message that should always be returned to the caller. All of this is
done in bpf_stream_backlog_fill().

From the kernel side, the writing into the stream will be a bit more
involved than the typical printk. First, the kernel typically may print
a collection of messages into the stream, and parallel writers into the
stream may suffer from interleaving of messages. To ensure each group of
messages is visible atomically, we can lift the advantage of using a
lockless list for pushing in messages.

To enable this, we add a bpf_stream_stage() macro, and require kernel
users to use bpf_stream_printk statements for the passed expression to
write into the stream. Underneath the macro, we have a message staging
API, where a bpf_stream_stage object on the stack accumulates the
messages being printed into a local llist_head, and then a commit
operation splices the whole batch into the stream's lockless log list.

This is especially pertinent for rqspinlock deadlock messages printed to
program streams. After this change, we see each deadlock invocation as a
non-interleaving contiguous message without any confusion on the
reader's part, improving their user experience in debugging the fault.

While programs cannot benefit from this staged stream writing API, they
could just as well hold an rqspinlock around their print statements to
serialize messages, hence this is kept kernel-internal for now.

Overall, this infrastructure provides NMI-safe any context printing of
messages to two dedicated streams.

Later patches will add support for printing splats in case of BPF arena
page faults, rqspinlock deadlocks, and cond_break timeouts, and
integration of this facility into bpftool for dumping messages to user
space.

  [0]: https://lore.kernel.org/bpf/20250501032718.65476-1-alexei.starovoitov@gmail.com

Reviewed-by: Eduard Zingerman <eddyz87@gmail.com>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20250703204818.925464-3-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
bpf: Add dmabuf iterator 2025-05-27T16:51:25+00:00 T.J. Mercier tjmercier@google.com 2025-05-22T23:04:26+00:00 76ea95534995adde1aa3cb1aa97ef33f50a617a9 The dmabuf iterator traverses the list of all DMA buffers. DMA buffers are refcounted through their associated struct file. A reference is taken on each buffer as the list is iterated to ensure each buffer persists for the duration of the bpf program execution without holding the list mutex. Signed-off-by: T.J. Mercier <tjmercier@google.com> Reviewed-by: Christian König <christian.koenig@amd.com> Acked-by: Song Liu <song@kernel.org> Link: https://lore.kernel.org/r/20250522230429.941193-3-tjmercier@google.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> 
The dmabuf iterator traverses the list of all DMA buffers.

DMA buffers are refcounted through their associated struct file. A
reference is taken on each buffer as the list is iterated to ensure each
buffer persists for the duration of the bpf program execution without
holding the list mutex.

Signed-off-by: T.J. Mercier <tjmercier@google.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Acked-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20250522230429.941193-3-tjmercier@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
rqspinlock: Add entry to Makefile, MAINTAINERS 2025-03-19T15:03:05+00:00 Kumar Kartikeya Dwivedi memxor@gmail.com 2025-03-16T04:05:33+00:00 e2082e32fd57976e811086708043c136ee596978 Ensure that the rqspinlock code is only built when the BPF subsystem is compiled in. Depending on queued spinlock support, we may or may not end up building the queued spinlock slowpath, and instead fallback to the test-and-set implementation. Also add entries to MAINTAINERS file. Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20250316040541.108729-18-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> 
Ensure that the rqspinlock code is only built when the BPF subsystem is
compiled in. Depending on queued spinlock support, we may or may not end
up building the queued spinlock slowpath, and instead fallback to the
test-and-set implementation. Also add entries to MAINTAINERS file.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20250316040541.108729-18-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
bpf: Avoid deadlock caused by nested kprobe and fentry bpf programs 2024-12-14T17:49:27+00:00 Priya Bala Govindasamy pgovind2@uci.edu 2024-12-14T01:58:58+00:00 c83508da5620ef89232cb614fb9e02dfdfef2b8f BPF program types like kprobe and fentry can cause deadlocks in certain situations. If a function takes a lock and one of these bpf programs is hooked to some point in the function's critical section, and if the bpf program tries to call the same function and take the same lock it will lead to deadlock. These situations have been reported in the following bug reports. In percpu_freelist - Link: https://lore.kernel.org/bpf/CAADnVQLAHwsa+2C6j9+UC6ScrDaN9Fjqv1WjB1pP9AzJLhKuLQ@mail.gmail.com/T/ Link: https://lore.kernel.org/bpf/CAPPBnEYm+9zduStsZaDnq93q1jPLqO-PiKX9jy0MuL8LCXmCrQ@mail.gmail.com/T/ In bpf_lru_list - Link: https://lore.kernel.org/bpf/CAPPBnEajj+DMfiR_WRWU5=6A7KKULdB5Rob_NJopFLWF+i9gCA@mail.gmail.com/T/ Link: https://lore.kernel.org/bpf/CAPPBnEZQDVN6VqnQXvVqGoB+ukOtHGZ9b9U0OLJJYvRoSsMY_g@mail.gmail.com/T/ Link: https://lore.kernel.org/bpf/CAPPBnEaCB1rFAYU7Wf8UxqcqOWKmRPU1Nuzk3_oLk6qXR7LBOA@mail.gmail.com/T/ Similar bugs have been reported by syzbot. In queue_stack_maps - Link: https://lore.kernel.org/lkml/0000000000004c3fc90615f37756@google.com/ Link: https://lore.kernel.org/all/20240418230932.2689-1-hdanton@sina.com/T/ In lpm_trie - Link: https://lore.kernel.org/linux-kernel/00000000000035168a061a47fa38@google.com/T/ In ringbuf - Link: https://lore.kernel.org/bpf/20240313121345.2292-1-hdanton@sina.com/T/ Prevent kprobe and fentry bpf programs from attaching to these critical sections by removing CC_FLAGS_FTRACE for percpu_freelist.o, bpf_lru_list.o, queue_stack_maps.o, lpm_trie.o, ringbuf.o files. The bugs reported by syzbot are due to tracepoint bpf programs being called in the critical sections. This patch does not aim to fix deadlocks caused by tracepoint programs. However, it does prevent deadlocks from occurring in similar situations due to kprobe and fentry programs. Signed-off-by: Priya Bala Govindasamy <pgovind2@uci.edu> Link: https://lore.kernel.org/r/CAPPBnEZpjGnsuA26Mf9kYibSaGLm=oF6=12L21X1GEQdqjLnzQ@mail.gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> 
BPF program types like kprobe and fentry can cause deadlocks in certain
situations. If a function takes a lock and one of these bpf programs is
hooked to some point in the function's critical section, and if the
bpf program tries to call the same function and take the same lock it will
lead to deadlock. These situations have been reported in the following
bug reports.

In percpu_freelist -
Link: https://lore.kernel.org/bpf/CAADnVQLAHwsa+2C6j9+UC6ScrDaN9Fjqv1WjB1pP9AzJLhKuLQ@mail.gmail.com/T/
Link: https://lore.kernel.org/bpf/CAPPBnEYm+9zduStsZaDnq93q1jPLqO-PiKX9jy0MuL8LCXmCrQ@mail.gmail.com/T/
In bpf_lru_list -
Link: https://lore.kernel.org/bpf/CAPPBnEajj+DMfiR_WRWU5=6A7KKULdB5Rob_NJopFLWF+i9gCA@mail.gmail.com/T/
Link: https://lore.kernel.org/bpf/CAPPBnEZQDVN6VqnQXvVqGoB+ukOtHGZ9b9U0OLJJYvRoSsMY_g@mail.gmail.com/T/
Link: https://lore.kernel.org/bpf/CAPPBnEaCB1rFAYU7Wf8UxqcqOWKmRPU1Nuzk3_oLk6qXR7LBOA@mail.gmail.com/T/

Similar bugs have been reported by syzbot.
In queue_stack_maps -
Link: https://lore.kernel.org/lkml/0000000000004c3fc90615f37756@google.com/
Link: https://lore.kernel.org/all/20240418230932.2689-1-hdanton@sina.com/T/
In lpm_trie -
Link: https://lore.kernel.org/linux-kernel/00000000000035168a061a47fa38@google.com/T/
In ringbuf -
Link: https://lore.kernel.org/bpf/20240313121345.2292-1-hdanton@sina.com/T/

Prevent kprobe and fentry bpf programs from attaching to these critical
sections by removing CC_FLAGS_FTRACE for percpu_freelist.o,
bpf_lru_list.o, queue_stack_maps.o, lpm_trie.o, ringbuf.o files.

The bugs reported by syzbot are due to tracepoint bpf programs being
called in the critical sections. This patch does not aim to fix deadlocks
caused by tracepoint programs. However, it does prevent deadlocks from
occurring in similar situations due to kprobe and fentry programs.

Signed-off-by: Priya Bala Govindasamy <pgovind2@uci.edu>
Link: https://lore.kernel.org/r/CAPPBnEZpjGnsuA26Mf9kYibSaGLm=oF6=12L21X1GEQdqjLnzQ@mail.gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
bpf: Introduce range_tree data structure and use it in bpf arena 2024-11-13T21:52:45+00:00 Alexei Starovoitov ast@kernel.org 2024-11-08T02:56:15+00:00 b795379757eb054925fbb6783559c86f01c1a614 Introduce range_tree data structure and use it in bpf arena to track ranges of allocated pages. range_tree is a large bitmap that is implemented as interval tree plus rbtree. The contiguous sequence of bits represents unallocated pages. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/bpf/20241108025616.17625-2-alexei.starovoitov@gmail.com 
Introduce range_tree data structure and use it in bpf arena to track
ranges of allocated pages. range_tree is a large bitmap that is
implemented as interval tree plus rbtree. The contiguous sequence of
bits represents unallocated pages.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/bpf/20241108025616.17625-2-alexei.starovoitov@gmail.com
bpf: Add kmem_cache iterator 2024-10-15T01:33:04+00:00 Namhyung Kim namhyung@kernel.org 2024-10-10T23:25:03+00:00 4971266e1595f76be3f844c834c1f9357a97dbde The new "kmem_cache" iterator will traverse the list of slab caches and call attached BPF programs for each entry. It should check the argument (ctx.s) if it's NULL before using it. Now the iteration grabs the slab_mutex only if it traverse the list and releases the mutex when it runs the BPF program. The kmem_cache entry is protected by a refcount during the execution. Signed-off-by: Namhyung Kim <namhyung@kernel.org> Acked-by: Vlastimil Babka <vbabka@suse.cz> #slab Link: https://lore.kernel.org/r/20241010232505.1339892-2-namhyung@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> 
The new "kmem_cache" iterator will traverse the list of slab caches
and call attached BPF programs for each entry.  It should check the
argument (ctx.s) if it's NULL before using it.

Now the iteration grabs the slab_mutex only if it traverse the list and
releases the mutex when it runs the BPF program.  The kmem_cache entry
is protected by a refcount during the execution.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz> #slab
Link: https://lore.kernel.org/r/20241010232505.1339892-2-namhyung@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
bpf: Remove custom build rule 2024-08-30T15:55:26+00:00 Alexey Gladkov legion@kernel.org 2024-08-30T07:43:50+00:00 1dd7622ef5085e0fd332d1293530b350499c374d According to the documentation, when building a kernel with the C=2 parameter, all source files should be checked. But this does not happen for the kernel/bpf/ directory. $ touch kernel/bpf/core.o $ make C=2 CHECK=true kernel/bpf/core.o Outputs: CHECK scripts/mod/empty.c CALL scripts/checksyscalls.sh DESCEND objtool INSTALL libsubcmd_headers CC kernel/bpf/core.o As can be seen the compilation is done, but CHECK is not executed. This happens because kernel/bpf/Makefile has defined its own rule for compilation and forgotten the macro that does the check. There is no need to duplicate the build code, and this rule can be removed to use generic rules. Acked-by: Masahiro Yamada <masahiroy@kernel.org> Tested-by: Oleg Nesterov <oleg@redhat.com> Tested-by: Alan Maguire <alan.maguire@oracle.com> Signed-off-by: Alexey Gladkov <legion@kernel.org> Link: https://lore.kernel.org/r/20240830074350.211308-1-legion@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> 
According to the documentation, when building a kernel with the C=2
parameter, all source files should be checked. But this does not happen
for the kernel/bpf/ directory.

$ touch kernel/bpf/core.o
$ make C=2 CHECK=true kernel/bpf/core.o

Outputs:

  CHECK   scripts/mod/empty.c
  CALL    scripts/checksyscalls.sh
  DESCEND objtool
  INSTALL libsubcmd_headers
  CC      kernel/bpf/core.o

As can be seen the compilation is done, but CHECK is not executed. This
happens because kernel/bpf/Makefile has defined its own rule for
compilation and forgotten the macro that does the check.

There is no need to duplicate the build code, and this rule can be
removed to use generic rules.

Acked-by: Masahiro Yamada <masahiroy@kernel.org>
Tested-by: Oleg Nesterov <oleg@redhat.com>
Tested-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Alexey Gladkov <legion@kernel.org>
Link: https://lore.kernel.org/r/20240830074350.211308-1-legion@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
libbpf,bpf: Share BTF relocate-related code with kernel 2024-06-21T21:45:07+00:00 Alan Maguire alan.maguire@oracle.com 2024-06-20T09:17:31+00:00 8646db238997df36c6ad71a9d7e0b52ceee221b2 Share relocation implementation with the kernel. As part of this, we also need the type/string iteration functions so also share btf_iter.c file. Relocation code in kernel and userspace is identical save for the impementation of the reparenting of split BTF to the relocated base BTF and retrieval of the BTF header from "struct btf"; these small functions need separate user-space and kernel implementations for the separate "struct btf"s they operate upon. One other wrinkle on the kernel side is we have to map .BTF.ids in modules as they were generated with the type ids used at BTF encoding time. btf_relocate() optionally returns an array mapping from old BTF ids to relocated ids, so we use that to fix up these references where needed for kfuncs. Signed-off-by: Alan Maguire <alan.maguire@oracle.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/bpf/20240620091733.1967885-5-alan.maguire@oracle.com 
Share relocation implementation with the kernel.  As part of this,
we also need the type/string iteration functions so also share
btf_iter.c file. Relocation code in kernel and userspace is identical
save for the impementation of the reparenting of split BTF to the
relocated base BTF and retrieval of the BTF header from "struct btf";
these small functions need separate user-space and kernel implementations
for the separate "struct btf"s they operate upon.

One other wrinkle on the kernel side is we have to map .BTF.ids in
modules as they were generated with the type ids used at BTF encoding
time. btf_relocate() optionally returns an array mapping from old BTF
ids to relocated ids, so we use that to fix up these references where
needed for kfuncs.

Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/bpf/20240620091733.1967885-5-alan.maguire@oracle.com