Previously, the verifier only tracked positive constant deltas between
linked registers using BPF_ADD. This limitation meant patterns like:
r1 = r0;
r1 += -4;
if r1 s>= 0 goto l0_%=; // r1 >= 0 implies r0 >= 4
// verifier couldn't propagate bounds back to r0
if r0 != 0 goto l0_%=;
r0 /= 0; // Verifier thinks this is reachable
l0_%=:
Similar limitation exists for 32-bit registers.
With this change, the verifier can now track negative deltas in reg->off
enabling bound propagation for the above pattern.
For alu32, we make sure the destination register has the upper 32 bits
as 0s before creating the link. BPF_ADD_CONST is split into
BPF_ADD_CONST64 and BPF_ADD_CONST32, the latter is used in case of alu32
and sync_linked_regs uses this to zext the result if known_reg has this
flag.
Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260204151741.2678118-2-puranjay@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Now BPF_END has bitwise tracking support. This patch adds selftests to
cover various cases of BPF_END (`bswap(16|32|64)`, `be(16|32|64)`,
`le(16|32|64)`) with bitwise propagation.
This patch is based on existing `verifier_bswap.c`, and add several
types of new tests:
1. Unconditional byte swap operations:
- bswap16/bswap32/bswap64 with unknown bytes
2. Endian conversion operations (architecture-aware):
- be16/be32/be64: convert to big-endian
* on little-endian: do swap
* on big-endian: truncation (16/32-bit) or no-op (64-bit)
- le16/le32/le64: convert to little-endian
* on big-endian: do swap
* on little-endian: truncation (16/32-bit) or no-op (64-bit)
Each test simulates realistic networking scenarios where a value is
masked with unknown bits (e.g., var_off=(0x0; 0x3f00), range=[0,0x3f00]),
then byte-swapped, and the verifier must prove the result stays within
expected bounds.
Specifically, these selftests are based on dead code elimination:
If the BPF verifier can precisely track bitwise through byte swap
operations, it can prune the trap path (invalid memory access) that
should be unreachable, allowing the program to pass verification.
If bitwise tracking is incorrect, the verifier cannot prove the trap
is unreachable, causing verification failure.
The tests use preprocessor conditionals (#ifdef __BYTE_ORDER__) to
verify correct behavior on both little-endian and big-endian
architectures, and require Clang 18+ for bswap instruction support.
Co-developed-by: Shenghao Yuan <shenghaoyuan0928@163.com>
Signed-off-by: Shenghao Yuan <shenghaoyuan0928@163.com>
Co-developed-by: Yazhou Tang <tangyazhou518@outlook.com>
Signed-off-by: Yazhou Tang <tangyazhou518@outlook.com>
Signed-off-by: Tianci Cao <ziye@zju.edu.cn>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260204111503.77871-3-ziye@zju.edu.cn
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Add stress tests for BPF timers that run in NMI context using perf_event
programs attached to PERF_COUNT_HW_CPU_CYCLES.
The tests cover three scenarios:
- nmi_race: Tests concurrent timer start and async cancel operations
- nmi_update: Tests updating a map element (effectively deleting and
inserting new for array map) from within a timer callback
- nmi_cancel: Tests timer self-cancellation attempt.
A common test_common() helper is used to share timer setup logic across
all test modes.
The tests spawn multiple threads in a child process to generate
perf events, which trigger the BPF programs in NMI context. Hit counters
verify that the NMI code paths were actually exercised.
Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20260201025403.66625-8-alexei.starovoitov@gmail.com
Scalar register IDs are used by the verifier to track relationships
between registers and enable bounds propagation across those
relationships. Once an ID becomes singular (i.e. only a single
register/stack slot carries it), it can no longer contribute to bounds
propagation and effectively becomes stale. The previous commit makes the
verifier clear such ids before caching the state.
When comparing the current and cached states for pruning, these stale
IDs can cause technically equivalent states to be considered different
and thus prevent pruning.
For example, in the selftest added in the next commit, two registers -
r6 and r7 are not linked to any other registers and get cached with
id=0, in the current state, they are both linked to each other with
id=A. Before this commit, check_scalar_ids would give temporary ids to
r6 and r7 (say tid1 and tid2) and then check_ids() would map tid1->A,
and when it would see tid2->A, it would not consider these state
equivalent.
Relax scalar ID equivalence by treating rold->id == 0 as "independent":
if the old state did not rely on any ID relationships for a register,
then any ID/linking present in the current state only adds constraints
and is always safe to accept for pruning. Implement this by returning
true immediately in check_scalar_ids() when old_id == 0.
Maintain correctness for the opposite direction (old_id != 0 && cur_id
== 0) by still allocating a temporary ID for cur_id == 0. This avoids
incorrectly allowing multiple independent current registers (id==0) to
satisfy a single linked old ID during mapping.
Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
Link: https://lore.kernel.org/r/20260203165102.2302462-5-puranjay@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
The added fsession does not prevent running on those architectures, that
haven't added fsession support.
For example, try to run fsession tests on arm64:
test_fsession_basic:PASS:fsession_test__open_and_load 0 nsec
test_fsession_basic:PASS:fsession_attach 0 nsec
check_result:FAIL:test_run_opts err unexpected error: -14 (errno 14)
In order to prevent such errors, add bpf_jit_supports_fsession() to guard
those architectures.
Fixes: 2d419c4465 ("bpf: add fsession support")
Acked-by: Puranjay Mohan <puranjay@kernel.org>
Tested-by: Puranjay Mohan <puranjay@kernel.org>
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Link: https://lore.kernel.org/r/20260131144950.16294-2-leon.hwang@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Recent x86 kernels export __preempt_count as a ksym, while some old kernels
between v6.1 and v6.14 expose the preemption counter via
pcpu_hot.preempt_count. The existing selftest helper unconditionally
dereferenced __preempt_count, which breaks BPF program loading on such old
kernels.
Make the x86 preemption count lookup version-agnostic by:
- Marking __preempt_count and pcpu_hot as weak ksyms.
- Introducing a BTF-described pcpu_hot___local layout with
preserve_access_index.
- Selecting the appropriate access path at runtime using ksym availability
and bpf_ksym_exists() and bpf_core_field_exists().
This allows a single BPF binary to run correctly across kernel versions
(e.g., v6.18 vs. v6.13) without relying on compile-time version checks.
Signed-off-by: Changwoo Min <changwoo@igalia.com>
Link: https://lore.kernel.org/r/20260130021843.154885-1-changwoo@igalia.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
When building selftests/bpf with EXTRA_LDFLAGS=-static the follwoing
error happens:
LINK /ws/linux/tools/testing/selftests/bpf/tools/build/bpftool/bootstrap/bpftool
/usr/bin/x86_64-linux-gnu-ld.bfd: /usr/lib/gcc/x86_64-linux-gnu/15/../../../x86_64-linux-gnu/libcrypto.a(libcrypto-lib-dso_dlfcn.o): in function `dlfcn_globallookup':
[...]
/usr/bin/x86_64-linux-gnu-ld.bfd: /usr/lib/gcc/x86_64-linux-gnu/15/../../../x86_64-linux-gnu/libcrypto.a(libcrypto-lib-c_zlib.o): in function `zlib_oneshot_expand_block':
(.text+0xc64): undefined reference to `uncompress'
/usr/bin/x86_64-linux-gnu-ld.bfd: /usr/lib/gcc/x86_64-linux-gnu/15/../../../x86_64-linux-gnu/libcrypto.a(libcrypto-lib-c_zlib.o): in function `zlib_oneshot_compress_block':
(.text+0xce4): undefined reference to `compress'
collect2: error: ld returned 1 exit status
make[1]: *** [Makefile:252: /ws/linux/tools/testing/selftests/bpf/tools/build/bpftool/bootstrap/bpftool] Error 1
make: *** [Makefile:327: /ws/linux/tools/testing/selftests/bpf/tools/sbin/bpftool] Error 2
make: *** Waiting for unfinished jobs....
This is caused by wrong order of dependencies in the Makefile. Fix it.
Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20260128211255.376933-1-ihor.solodrai@linux.dev
The verification signature header generation requires converting a
binary certificate to a C array. Previously this only worked with
xxd (part of vim-common package).
As xxd may not be available on some systems building selftests, it makes
sense to substitute it with more common utils: hexdump, wc, sed to
generate equivalent C array output.
Tested by generating header with both xxd and hexdump and comparing
them.
Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Tested-by: Alan Maguire <alan.maguire@oracle.com>
Link: https://lore.kernel.org/bpf/20260128190552.242335-1-mykyta.yatsenko5@gmail.com
Currently, the BPF cgroup iterator supports walking descendants in
either pre-order (BPF_CGROUP_ITER_DESCENDANTS_PRE) or post-order
(BPF_CGROUP_ITER_DESCENDANTS_POST). These modes perform an exhaustive
depth-first search (DFS) of the hierarchy. In scenarios where a BPF
program may need to inspect only the direct children of a given parent
cgroup, a full DFS is unnecessarily expensive.
This patch introduces a new BPF cgroup iterator control option,
BPF_CGROUP_ITER_CHILDREN. This control option restricts the traversal
to the immediate children of a specified parent cgroup, allowing for
more targeted and efficient iteration, particularly when exhaustive
depth-first search (DFS) traversal is not required.
Signed-off-by: Matt Bobrowski <mattbobrowski@google.com>
Link: https://lore.kernel.org/r/20260127085112.3608687-1-mattbobrowski@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
The test_bpftool_map.sh script tests that maps read/write accesses
are being properly allowed/refused by the kernel depending on a specific
fmod_ret program being attached on security_bpf_map function.
Rewrite this test to integrate it in the test_progs. The
new test spawns a few subtests:
#36/1 bpftool_maps_access/unprotected_unpinned:OK
#36/2 bpftool_maps_access/unprotected_pinned:OK
#36/3 bpftool_maps_access/protected_unpinned:OK
#36/4 bpftool_maps_access/protected_pinned:OK
#36/5 bpftool_maps_access/nested_maps:OK
#36/6 bpftool_maps_access/btf_list:OK
#36 bpftool_maps_access:OK
Summary: 1/6 PASSED, 0 SKIPPED, 0 FAILED
Signed-off-by: Alexis Lothoré (eBPF Foundation) <alexis.lothore@bootlin.com>
Acked-by: Quentin Monnet <qmo@kernel.org>
Link: https://lore.kernel.org/r/20260123-bpftool-tests-v4-3-a6653a7f28e7@bootlin.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
The test_bpftool_metadata.sh script validates that bpftool properly
returns in its ouptput any metadata generated by bpf programs through
some .rodata sections.
Port this test to the test_progs framework so that it can be executed
automatically in CI. The new test, similarly to the former script,
checks that valid data appears both for textual output and json output,
as well as for both data not used at all and used data. For the json
check part, the expected json string is hardcoded to avoid bringing a
new external dependency (eg: a json deserializer) for test_progs.
As the test is now converted into test_progs, remove the former script.
The newly converted test brings two new subtests:
#37/1 bpftool_metadata/metadata_unused:OK
#37/2 bpftool_metadata/metadata_used:OK
#37 bpftool_metadata:OK
Summary: 1/2 PASSED, 0 SKIPPED, 0 FAILED
Signed-off-by: Alexis Lothoré (eBPF Foundation) <alexis.lothore@bootlin.com>
Link: https://lore.kernel.org/r/20260123-bpftool-tests-v4-2-a6653a7f28e7@bootlin.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
In order to integrate some bpftool tests into test_progs, define a few
specific helpers that allow to execute bpftool commands, while possibly
retrieving the command output. Those helpers most notably set the
path to the bpftool binary under test. This version checks different
possible paths relative to the directories where the different
test_progs runners are executed, as we want to make sure not to
accidentally use a bootstrap version of the binary.
Signed-off-by: Alexis Lothoré (eBPF Foundation) <alexis.lothore@bootlin.com>
Link: https://lore.kernel.org/r/20260123-bpftool-tests-v4-1-a6653a7f28e7@bootlin.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
CI occasionally reports failures in the
percpu_alloc/cpu_flag_lru_percpu_hash selftest, for example:
First test_progs failure (test_progs_no_alu32-x86_64-llvm-21):
#264/15 percpu_alloc/cpu_flag_lru_percpu_hash
...
test_percpu_map_op_cpu_flag:FAIL:bpf_map_lookup_batch value on specified cpu unexpected bpf_map_lookup_batch value on specified cpu: actual 0 != expected 3735929054
The unexpected value indicates that an element was removed from the map.
However, the test never calls delete_elem(), so the only possible cause
is LRU eviction.
This can happen when the current task migrates to another CPU: an
update_elem() triggers eviction because there is no available LRU node
on local freelist and global freelist.
Harden the test against this behavior by provisioning sufficient spare
elements. Set max_entries to 'nr_cpus * 2' and restrict the test to using
the first nr_cpus entries, ensuring that updates do not spuriously trigger
LRU eviction.
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://patch.msgid.link/20260119133417.19739-1-leon.hwang@linux.dev
Add a new selftest suite `exe_ctx` to verify the accuracy of the
bpf_in_task(), bpf_in_hardirq(), and bpf_in_serving_softirq() helpers
introduced in bpf_experimental.h.
Testing these execution contexts deterministically requires crossing
context boundaries within a single CPU. To achieve this, the test
implements a "Trigger-Observer" pattern using bpf_testmod:
1. Trigger: A BPF syscall program calls a new bpf_testmod kfunc
bpf_kfunc_trigger_ctx_check().
2. Task to HardIRQ: The kfunc uses irq_work_queue() to trigger a
self-IPI on the local CPU.
3. HardIRQ to SoftIRQ: The irq_work handler calls a dummy function
(observed by BPF fentry) and then schedules a tasklet to
transition into SoftIRQ context.
The user-space runner ensures determinism by pinning itself to CPU 0
before execution, forcing the entire interrupt chain to remain on a
single core. Dummy noinline functions with compiler barriers are
added to bpf_testmod.c to serve as stable attachment points for
fentry programs. A retry loop is used in user-space to wait for the
asynchronous SoftIRQ to complete.
Note that testing on s390x is avoided because supporting those helpers
purely in BPF on s390x is not possible at this point.
Reviewed-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Changwoo Min <changwoo@igalia.com>
Link: https://lore.kernel.org/r/20260125115413.117502-3-changwoo@igalia.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Introduce bpf_in_nmi(), bpf_in_hardirq(), bpf_in_serving_softirq(), and
bpf_in_task() inline helpers in bpf_experimental.h. These allow BPF
programs to query the current execution context with higher granularity
than the existing bpf_in_interrupt() helper.
While BPF programs can often infer their context from attachment points,
subsystems like sched_ext may call the same BPF logic from multiple
contexts (e.g., task-to-task wake-ups vs. interrupt-to-task wake-ups).
These helpers provide a reliable way for logic to branch based on
the current CPU execution state.
Implementing these as BPF-native inline helpers wrapping
get_preempt_count() allows the compiler and JIT to inline the logic. The
implementation accounts for differences in preempt_count layout between
standard and PREEMPT_RT kernels.
Reviewed-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Changwoo Min <changwoo@igalia.com>
Link: https://lore.kernel.org/r/20260125115413.117502-2-changwoo@igalia.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Test session cookie for fsession. Multiple fsession BPF progs is attached
to bpf_fentry_test1() and session cookie is read and write in the
testcase.
bpf_get_func_ip() will influence the layout of the session cookies, so we
test the cookie in two case: with and without bpf_get_func_ip().
Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
Link: https://lore.kernel.org/r/20260124062008.8657-13-dongml2@chinatelecom.cn
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
If the argument 'pull_len' of run_test() is 'PULL_MAX' or
'PULL_MAX | PULL_PLUS_ONE', the eventual pull_len size
will close to the page size. On arm64 systems with 64K pages,
the pull_len size will be close to 64K. But the existing buffer
will be close to 9000 which is not enough to pull.
For those failed run_tests(), make buff size to
pg_sz + (pg_sz / 2)
This way, there will be enough buffer space to pull
regardless of page size.
Tested-by: Alan Maguire <alan.maguire@oracle.com>
Cc: Amery Hung <ameryhung@gmail.com>
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Acked-by: Amery Hung <ameryhung@gmail.com>
Link: https://lore.kernel.org/r/20260123055128.495265-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
On arm64 systems with 64K pages, the selftest task_local_data has the following
failures:
...
test_task_local_data_basic:PASS:tld_create_key 0 nsec
test_task_local_data_basic:FAIL:tld_create_key unexpected tld_create_key: actual 0 != expected -28
...
test_task_local_data_basic_thread:PASS:run task_main 0 nsec
test_task_local_data_basic_thread:FAIL:task_main retval unexpected error: 2 (errno 0)
test_task_local_data_basic_thread:FAIL:tld_get_data value0 unexpected tld_get_data value0: actual 0 != expected 6268
...
#447/1 task_local_data/task_local_data_basic:FAIL
...
#447/2 task_local_data/task_local_data_race:FAIL
#447 task_local_data:FAIL
When TLD_DYN_DATA_SIZE is 64K page size, for
struct tld_meta_u {
_Atomic __u8 cnt;
__u16 size;
struct tld_metadata metadata[];
};
field 'cnt' would overflow. For example, for 4K page, 'cnt' will
be 4096/64 = 64. But for 64K page, 'cnt' will be 65536/64 = 1024
and 'cnt' is not enough for 1024. To accommodate 64K page,
'_Atomic __u8 cnt' becomes '_Atomic __u16 cnt'. A few other places
are adjusted accordingly.
In test_task_local_data.c, the value for TLD_DYN_DATA_SIZE is changed
from 4096 to (getpagesize() - 8) since the maximum buffer size for
TLD_DYN_DATA_SIZE is (getpagesize() - 8).
Reviewed-by: Alan Maguire <alan.maguire@oracle.com>
Tested-by: Alan Maguire <alan.maguire@oracle.com>
Cc: Amery Hung <ameryhung@gmail.com>
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Acked-by: Amery Hung <ameryhung@gmail.com>
Link: https://lore.kernel.org/r/20260123055122.494352-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
When wq__attach() fails, serial_test_wq() returns early without calling
wq__destroy(), leaking the skeleton resources allocated by
wq__open_and_load(). This causes ASAN leak reports in selftests runs.
Fix this by jumping to a common clean_up label that calls wq__destroy()
on all exit paths after successful open_and_load.
Note that the early return after wq__open_and_load() failure is correct
and doesn't need fixing, since that function returns NULL on failure
(after internally cleaning up any partial allocations).
Fixes: 8290dba519 ("selftests/bpf: wq: add bpf_wq_start() checks")
Signed-off-by: Kery Qi <qikeyu2017@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/bpf/20260121094114.1801-3-qikeyu2017@gmail.com
