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bpf: Support dumping kfunc prototypes from BTF #7169

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bpf: Support dumping kfunc prototypes from BTF #7169

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kernel-patches-daemon-bpf[bot]
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Pull request for series with
subject: bpf: Support dumping kfunc prototypes from BTF
version: 4
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=860192

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Upstream branch: f85af9d
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=860192
version: 4

@kernel-patches-daemon-bpf
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Upstream branch: 2ebb87f
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=860192
version: 4

@kernel-patches-daemon-bpf
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Upstream branch: bb678f0
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=860192
version: 4

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At least one diff in series https://patchwork.kernel.org/project/netdevbpf/list/?series=860192 expired. Closing PR.

Kernel Patches Daemon and others added 13 commits June 11, 2024 11:45
adding ci files
6a90984
@danobi
kbuild: bpf: Tell pahole to DECL_TAG kfuncs
cbdd868 
With [0], pahole can now discover kfuncs and inject DECL_TAG
into BTF. With this commit, we will start shipping said DECL_TAGs
to downstream consumers if pahole supports it.

This is useful for feature probing kfuncs as well as generating
compilable prototypes. This is particularly important as kfuncs
do not have stable ABI.

[0]: https://git.kernel.org/pub/scm/devel/pahole/pahole.git/commit/?id=72e88f29c6f7e14201756e65bd66157427a61aaf

Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
@danobi
bpf: selftests: Fix bpf_iter_task_vma_new() prototype
c7b7d5b 
bpf_iter_task_vma_new() is defined as taking a u64 as its 3rd argument.
u64 is a unsigned long long. bpf_experimental.h was defining the
prototype as unsigned long.

Fix by using __u64.

Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
@danobi
bpf: selftests: Fix fentry test kfunc prototypes
5235883 
Some prototypes in progs/get_func_ip_test.c were not in line with how the
actual kfuncs are defined in net/bpf/test_run.c. This causes compilation
errors when kfunc prototypes are generated from BTF.

Fix by aligning with actual kfunc definitions.

Also remove two unused prototypes.

Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
@danobi
bpf: selftests: Fix bpf_cpumask_first_zero() kfunc prototype
b9f39eb 
The prototype in progs/nested_trust_common.h is not in line with how the
actual kfuncs are defined in kernel/bpf/cpumask.c. This causes compilation
errors when kfunc prototypes are generated from BTF.

Fix by aligning with actual kfunc definitions.

Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
@danobi
bpf: selftests: Fix bpf_map_sum_elem_count() kfunc prototype
01b15fc 
The prototype in progs/map_percpu_stats.c is not in line with how the
actual kfuncs are defined in kernel/bpf/map_iter.c. This causes
compilation errors when kfunc prototypes are generated from BTF.

Fix by aligning with actual kfunc definitions.

Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
@danobi
bpf: Make bpf_session_cookie() kfunc return long *
d52eed4 
We will soon be generating kfunc prototypes from BTF. As part of that,
we need to align the manual signatures in bpf_kfuncs.h with the actual
kfunc definitions. There is currently a conflicting signature for
bpf_session_cookie() w.r.t. return type.

The original intent was to return long * and not __u64 *. You can see
evidence of that intent in a3a5113 ("selftests/bpf: Add kprobe
session cookie test").

Fix conflict by changing kfunc definition.

Fixes: 5c919ac ("bpf: Add support for kprobe session cookie")
Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
@danobi
bpf: selftests: Namespace struct_opt callbacks in bpf_dctcp
5fd0e18 
With generated kfunc prototypes, the existing callback names will
conflict. Fix by namespacing with a bpf_ prefix.

Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
@danobi
bpf: verifier: Relax caller requirements for kfunc projection type args
80c4166 
Currently, if a kfunc accepts a projection type as an argument (eg
struct __sk_buff *), the caller must exactly provide exactly the same
type with provable provenance.

However in practice, kfuncs that accept projection types _must_ cast to
the underlying type before use b/c projection type layouts are
completely made up. Thus, it is ok to relax the verifier rules around
implicit conversions.

We will use this functionality in the next commit when we align kfuncs
to user-facing types.

Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
@danobi
bpf: treewide: Align kfunc signatures to prog point-of-view
2514d25 
Previously, kfunc declarations in bpf_kfuncs.h (and others) used "user
facing" types for kfuncs prototypes while the actual kfunc definitions
used "kernel facing" types. More specifically: bpf_dynptr vs
bpf_dynptr_kern, __sk_buff vs sk_buff, and xdp_md vs xdp_buff.

It wasn't an issue before, as the verifier allows aliased types.
However, since we are now generating kfunc prototypes in vmlinux.h (in
addition to keeping bpf_kfuncs.h around), this conflict creates
compilation errors.

Fix this conflict by using "user facing" types in kfunc definitions.
This results in more casts, but otherwise has no additional runtime
cost.

Note, similar to 5b268d1 ("bpf: Have bpf_rdonly_cast() take a const
pointer"), we also make kfuncs take const arguments where appropriate in
order to make the kfunc more permissive.

Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
@danobi
bpf: selftests: nf: Opt out of using generated kfunc prototypes
469e45a 
The bpf-nf selftests play various games with aliased types such that
folks with CONFIG_NF_CONNTRACK=m/n configs can still build the
selftests. See commits:

1058b6a ("selftests/bpf: Do not fail build if CONFIG_NF_CONNTRACK=m/n")
92afc53 ("selftests/bpf: Fix build errors if CONFIG_NF_CONNTRACK=m")

Thus, it is simpler if these selftests opt out of using generated kfunc
prototypes. The preprocessor macro this commit uses will be introduced
in the final commit.

Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
@danobi
bpf: selftests: xfrm: Opt out of using generated kfunc prototypes
b1ea458 
The xfrm_info selftest locally defines an aliased type such that folks
with CONFIG_XFRM_INTERFACE=m/n configs can still build the selftests.
See commit aa67961 ("selftests/bpf: Allow building bpf tests with CONFIG_XFRM_INTERFACE=[m|n]").

Thus, it is simpler if this selftest opts out of using enerated kfunc
prototypes. The preprocessor macro this commit uses will be introduced
in the final commit.

Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
@danobi
bpftool: Support dumping kfunc prototypes from BTF
ba41a57 
This patch enables dumping kfunc prototypes from bpftool. This is useful
b/c with this patch, end users will no longer have to manually define
kfunc prototypes. For the kernel tree, this also means we can optionally
drop kfunc prototypes from:

        tools/testing/selftests/bpf/bpf_kfuncs.h
        tools/testing/selftests/bpf/bpf_experimental.h

Example usage:

        $ make PAHOLE=/home/dxu/dev/pahole/build/pahole -j30 vmlinux

        $ ./tools/bpf/bpftool/bpftool btf dump file ./vmlinux format c | rg "__ksym;" | head -3
        extern void cgroup_rstat_updated(struct cgroup *cgrp, int cpu) __weak __ksym;
        extern void cgroup_rstat_flush(struct cgroup *cgrp) __weak __ksym;
        extern struct bpf_key *bpf_lookup_user_key(u32 serial, u64 flags) __weak __ksym;

Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
@kernel-patches-daemon-bpf
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Upstream branch: 98b303c
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=861266
version: 5

@kernel-patches-daemon-bpf
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At least one diff in series https://patchwork.kernel.org/project/netdevbpf/list/?series=861266 irrelevant now. Closing PR.

@kernel-patches-daemon-bpf kernel-patches-daemon-bpf bot deleted the series/860192=>bpf-next branch June 12, 2024 18:16
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@danobi