Tweak existing map_kptr test to check kptr_rcu.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/bpf/20230303041446.3630-5-alexei.starovoitov@gmail.com

The life time of certain kernel structures like 'struct cgroup' is protected by RCU.
Hence it's safe to dereference them directly from __kptr tagged pointers in bpf maps.
The resulting pointer is MEM_RCU and can be passed to kfuncs that expect KF_RCU.
Derefrence of other kptr-s returns PTR_UNTRUSTED.

For example:
struct map_value {
   struct cgroup __kptr *cgrp;
};

SEC("tp_btf/cgroup_mkdir")
int BPF_PROG(test_cgrp_get_ancestors, struct cgroup *cgrp_arg, const char *path)
{
  struct cgroup *cg, *cg2;

  cg = bpf_cgroup_acquire(cgrp_arg); // cg is PTR_TRUSTED and ref_obj_id > 0
  bpf_kptr_xchg(&v->cgrp, cg);

  cg2 = v->cgrp; // This is new feature introduced by this patch.
  // cg2 is PTR_MAYBE_NULL | MEM_RCU.
  // When cg2 != NULL, it's a valid cgroup, but its percpu_ref could be zero

  if (cg2)
    bpf_cgroup_ancestor(cg2, level); // safe to do.
}
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/bpf/20230303041446.3630-4-alexei.starovoitov@gmail.com

bpf programs sometimes do:
bpf_cgrp_storage_get(&map, task->cgroups->dfl_cgrp, ...);
It is safe to do, because cgroups->dfl_cgrp pointer is set diring init and
never changes. The task->cgroups is also never NULL. It is also set during init
and will change when task switches cgroups. For any trusted task pointer
dereference of cgroups and dfl_cgrp should yield trusted pointers. The verifier
wasn't aware of this. Hence in gcc compiled kernels task->cgroups dereference
was producing PTR_TO_BTF_ID without modifiers while in clang compiled kernels
the verifier recognizes __rcu tag in cgroups field and produces
PTR_TO_BTF_ID | MEM_RCU | MAYBE_NULL.
Tag cgroups and dfl_cgrp as trusted to equalize clang and gcc behavior.
When GCC supports btf_type_tag such tagging will done directly in the type.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: David Vernet <void@manifault.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/bpf/20230303041446.3630-3-alexei.starovoitov@gmail.com

__kptr meant to store PTR_UNTRUSTED kernel pointers inside bpf maps.
The concept felt useful, but didn't get much traction,
since bpf_rdonly_cast() was added soon after and bpf programs received
a simpler way to access PTR_UNTRUSTED kernel pointers
without going through restrictive __kptr usage.

Rename __kptr_ref -> __kptr and __kptr -> __kptr_untrusted to indicate
its intended usage.
The main goal of __kptr_untrusted was to read/write such pointers
directly while bpf_kptr_xchg was a mechanism to access refcnted
kernel pointers. The next patch will allow RCU protected __kptr access
with direct read. At that point __kptr_untrusted will be deprecated.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/bpf/20230303041446.3630-2-alexei.starovoitov@gmail.com

Add test for the absolute BPF timer under the existing timer tests. This
will run the timer two times with 1us expiration time, and then re-arm
the timer at ~35s in the future. At the end, it is verified that the
absolute timer expired exactly two times.
Signed-off-by: Tero Kristo <tero.kristo@linux.intel.com>
Link: https://lore.kernel.org/r/20230302114614.2985072-3-tero.kristo@linux.intel.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

Add a new flag BPF_F_TIMER_ABS that can be passed to bpf_timer_start()
to start an absolute value timer instead of the default relative value.
This makes the timer expire at an exact point in time, instead of a time
with latencies induced by both the BPF and timer subsystems.
Suggested-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: Tero Kristo <tero.kristo@linux.intel.com>
Link: https://lore.kernel.org/r/20230302114614.2985072-2-tero.kristo@linux.intel.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

Per C99 standard [0], Section 6.7.8, Paragraph 10:

  If an object that has automatic storage duration is not initialized
  explicitly, its value is indeterminate.

And in the same document, in appendix "J.2 Undefined behavior":

  The behavior is undefined in the following circumstances:
  [...]
  The value of an object with automatic storage duration is used while
  it is indeterminate (6.2.4, 6.7.8, 6.8).

This means that use of an uninitialized stack variable is undefined
behavior, and therefore that clang can choose to do a variety of scary
things, such as not generating bytecode for "bunch of useful code" in
the below example:

  void some_func()
  {
    int i;
    if (!i)
      return;
    // bunch of useful code
  }

To add insult to injury, if some_func above is a helper function for
some BPF program, clang can choose to not generate an "exit" insn,
causing verifier to fail with "last insn is not an exit or jmp". Going
from that verification failure to the root cause of uninitialized use
is certain to be frustrating.

This patch adds -Wuninitialized to the cflags for selftest BPF progs and
fixes up existing instances of uninitialized use.

  [0]: https://www.open-std.org/jtc1/sc22/WG14/www/docs/n1256.pdfSigned-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Cc: David Vernet <void@manifault.com>
Cc: Tejun Heo <tj@kernel.org>
Acked-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20230303005500.1614874-1-davemarchevsky@fb.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

These helpers are safe to call from any context and there's no reason to
restrict access to them. Remove them from bpf_trace and filter lists and add
to bpf_base_func_proto() under perfmon_capable().

v2: After consulting with Andrii, relocated in bpf_base_func_proto() so that
    they require bpf_capable() but not perfomon_capable() as it doesn't read
    from or affect others on the system.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/ZAD8QyoszMZiTzBY@slm.duckdns.orgSigned-off-by: Alexei Starovoitov <ast@kernel.org>

maps.rst in the BPF documentation links to the
/userspace-api/ebpf/syscall document
(Documentation/userspace-api/ebpf/syscall.rst). For some reason, if you
try to reference the document with :doc:, the docs build emits the
following warning:

./Documentation/bpf/maps.rst:13: WARNING: \
    unknown document: '/userspace-api/ebpf/syscall'

It appears that other places in the docs tree also don't support using
:doc:. Elsewhere in the BPF documentation, we just reference the kernel
docs page directly. Let's do that here to clean up the last remaining
noise in the docs build.
Signed-off-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20230302183918.54190-2-void@manifault.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

The BPF devel Q&A documentation page makes frequent reference to the
netdev-QA page via the netdev-FAQ rst link. This link is currently
broken, as is evidenced by the build output when making BPF docs:

./Documentation/bpf/bpf_devel_QA.rst:150: WARNING: undefined label: 'netdev-faq'
./Documentation/bpf/bpf_devel_QA.rst:206: WARNING: undefined label: 'netdev-faq'
./Documentation/bpf/bpf_devel_QA.rst:231: WARNING: undefined label: 'netdev-faq'
./Documentation/bpf/bpf_devel_QA.rst:396: WARNING: undefined label: 'netdev-faq'
./Documentation/bpf/bpf_devel_QA.rst:412: WARNING: undefined label: 'netdev-faq'

Fix the links to point to the actual netdev-faq page.
Signed-off-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20230302183918.54190-1-void@manifault.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

Change bpf_dynptr_slice and bpf_dynptr_slice_rdwr to return NULL instead
of 0, in accordance with the codebase guidelines.

Fixes: 66e3a13e ("bpf: Add bpf_dynptr_slice and bpf_dynptr_slice_rdwr")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230302053014.1726219-1-joannelkoong@gmail.com

Daniel Müller says:

====================

On Android, APKs (android packages; zip packages with somewhat
prescriptive contents) are first class citizens in the system: the
shared objects contained in them don't exist in unpacked form on the
file system. Rather, they are mmaped directly from within the archive
and the archive is also what the kernel is aware of.

For users that complicates the process of attaching a uprobe to a
function contained in a shared object in one such APK: they'd have to
find the byte offset of said function from the beginning of the archive.
That is cumbersome to do manually and can be fragile, because various
changes could invalidate said offset.

That is why for uprobes inside ELF files (not inside an APK), commit
d112c9ce249b ("libbpf: Support function name-based attach uprobes") added
support for attaching to symbols by name. On Android, that mechanism
currently does not work, because this logic is not APK aware.

This patch set introduces first class support for attaching uprobes to
functions inside ELF objects contained in APKs via function names. We
add support for recognizing the following syntax for a binary path:
  <archive>!/<binary-in-archive>

  (e.g., /system/app/test-app.apk!/lib/arm64-v8a/libc++.so)

This syntax is common in the Android eco system and used by tools such
as simpleperf. It is also what is being proposed for bcc [0].

If the user provides such a binary path, we find <binary-in-archive>
(lib/arm64-v8a/libc++.so in the example) inside of <archive>
(/system/app/test-app.apk). We perform the regular ELF offset search
inside the binary and add that to the offset within the archive itself,
to retrieve the offset at which to attach the uprobe.

[0] https://github.com/iovisor/bcc/pull/4440

Changelog
---------
v3->v4:
- use ERR_PTR instead of libbpf_err_ptr() in zip_archive_open()
- eliminated err variable from elf_find_func_offset_from_archive()

v2->v3:
- adjusted zip_archive_open() to report errno
- fixed provided libbpf_strlcpy() buffer size argument
- adjusted find_cd() to handle errors better
- use fewer local variables in get_entry_at_offset()

v1->v2:
- removed unaligned_* types
- switched to using __u32 and __u16
- switched to using errno constants instead of hard-coded negative values
- added another pr_debug() message
- shortened central_directory_* to cd_*
- inlined cd_file_header_at_offset() function
- bunch of syntactical changes
====================
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

This change adds support for attaching uprobes to shared objects located
in APKs, which is relevant for Android systems where various libraries
may reside in APKs. To make that happen, we extend the syntax for the
"binary path" argument to attach to with that supported by various
Android tools:
  <archive>!/<binary-in-archive>

For example:
  /system/app/test-app/test-app.apk!/lib/arm64-v8a/libc++_shared.so

APKs need to be specified via full path, i.e., we do not attempt to
resolve mere file names by searching system directories.

We cannot currently test this functionality end-to-end in an automated
fashion, because it relies on an Android system being present, but there
is no support for that in CI. I have tested the functionality manually,
by creating a libbpf program containing a uretprobe, attaching it to a
function inside a shared object inside an APK, and verifying the sanity
of the returned values.
Signed-off-by: Daniel Müller <deso@posteo.net>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230301212308.1839139-4-deso@posteo.net

This change splits the elf_find_func_offset() function in two:
elf_find_func_offset(), which now accepts an already opened Elf object
instead of a path to a file that is to be opened, as well as
elf_find_func_offset_from_file(), which opens a binary based on a
path and then invokes elf_find_func_offset() on the Elf object. Having
this split in responsibilities will allow us to call
elf_find_func_offset() from other code paths on Elf objects that did not
necessarily come from a file on disk.
Signed-off-by: Daniel Müller <deso@posteo.net>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230301212308.1839139-3-deso@posteo.net

This change implements support for reading zip archives, including
opening an archive, finding an entry based on its path and name in it,
and closing it.
The code was copied from https://github.com/iovisor/bcc/pull/4440, which
implements similar functionality for bcc. The author confirmed that he
is fine with this usage and the corresponding relicensing. I adjusted it
to adhere to libbpf coding standards.
Signed-off-by: Daniel Müller <deso@posteo.net>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Michał Gregorczyk <michalgr@meta.com>
Link: https://lore.kernel.org/bpf/20230301212308.1839139-2-deso@posteo.net

In commit d96d937d ("bpf: Add __uninit kfunc annotation"), the
__uninit kfunc annotation was documented in kfuncs.rst. You have to
fully underline a section in rst, or the build will issue a warning that
the title underline is too short:

./Documentation/bpf/kfuncs.rst:104: WARNING: Title underline too short.

2.2.2 __uninit Annotation
--------------------

This patch fixes that title underline.

Fixes: d96d937d ("bpf: Add __uninit kfunc annotation")
Signed-off-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20230301194910.602738-2-void@manifault.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

In commit 66e3a13e ("bpf: Add bpf_dynptr_slice and
bpf_dynptr_slice_rdwr"), the bpf_dynptr_slice() and
bpf_dynptr_slice_rdwr() kfuncs were added to BPF. These kfuncs included
doxygen headers, but unfortunately those headers are not properly
formatted according to [0], and causes the following warnings during the
docs build:

./kernel/bpf/helpers.c:2225: warning: \
    Excess function parameter 'returns' description in 'bpf_dynptr_slice'
./kernel/bpf/helpers.c:2303: warning: \
    Excess function parameter 'returns' description in 'bpf_dynptr_slice_rdwr'
...

This patch fixes those doxygen comments.

[0]: https://docs.kernel.org/doc-guide/kernel-doc.html#function-documentation

Fixes: 66e3a13e ("bpf: Add bpf_dynptr_slice and bpf_dynptr_slice_rdwr")
Signed-off-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20230301194910.602738-1-void@manifault.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

Eduard Zingerman says:

====================

This patch allows to specify program flags and multiple verifier log
messages for the test_loader kind of tests. For example:

  tools/testing/selftets/bpf/progs/foobar.c:

    SEC("tc")
    __success __log_level(7)
    __msg("first message")
    __msg("next message")
    __flag(BPF_F_ANY_ALIGNMENT)
    int buz(struct __sk_buff *skb)
    { ... }

It was developed by Andrii Nakryiko ([1]), I reused it in a
"test_verifier tests migration to inline assembly" patch series ([2]),
but the series is currently stuck on my side.
Andrii asked to spin this particular patch separately ([3]).

[1] https://lore.kernel.org/bpf/CAEf4BzZH0ZxorCi7nPDbRqSK9f+410RooNwNJGwfw8=0a5i1nw@mail.gmail.com/
[2] https://lore.kernel.org/bpf/20230123145148.2791939-1-eddyz87@gmail.com/
[3] https://lore.kernel.org/bpf/20230123145148.2791939-1-eddyz87@gmail.com/T/#m52e806c5a679a2aa8f484d011be7ec105939127a
====================
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

Extend __flag attribute by allowing to specify one of the following:
 * BPF_F_STRICT_ALIGNMENT
 * BPF_F_ANY_ALIGNMENT
 * BPF_F_TEST_RND_HI32
 * BPF_F_TEST_STATE_FREQ
 * BPF_F_SLEEPABLE
 * BPF_F_XDP_HAS_FRAGS
 * Some numeric value

Extend __msg attribute by allowing to specify multiple exepcted messages.
All messages are expected to be present in the verifier log in the
order of application.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230301175417.3146070-2-eddyz87@gmail.com

[ Eduard: added commit message, formatting, comments ]

Viktor Malik says:

====================

Fixing several issues reported by Coverity and Clang Static Analyzer
(scan-build) for libbpf, mostly removing unnecessary symbols and
assignments.

No functional changes should be introduced.
====================
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

Clang Static Analyser (scan-build) reports some unused symbols and dead
assignments in the linker_append_elf_relos function. Clean these up.
Signed-off-by: Viktor Malik <vmalik@redhat.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/c5c8fe9f411b69afada8399d23bb048ef2a70535.1677658777.git.vmalik@redhat.com

Clang Static Analyzer (scan-build) reports several dead assignments in
libbpf where the assigned value is unconditionally overridden by another
value before it is read. Remove these assignments.
Signed-off-by: Viktor Malik <vmalik@redhat.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/5503d18966583e55158471ebbb2f67374b11bf5e.1677658777.git.vmalik@redhat.com

Coverity reports that the first check of 'err' in bpf_object__init_maps
is always false as 'err' is initialized to 0 at that point. Remove the
unnecessary ternary operator.
Signed-off-by: Viktor Malik <vmalik@redhat.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/78a3702f2ea9f32a84faaae9b674c56269d330a7.1677658777.git.vmalik@redhat.com

If target is bpf, there is no __loongarch__ definition, __BITS_PER_LONG
defaults to 32, __NR_nanosleep is not defined:

  #if defined(__ARCH_WANT_TIME32_SYSCALLS) || __BITS_PER_LONG != 32
  #define __NR_nanosleep 101
  __SC_3264(__NR_nanosleep, sys_nanosleep_time32, sys_nanosleep)
  #endif

Work around this problem, by explicitly setting __BITS_PER_LONG to
__loongarch_grlen which is defined by compiler as 64 for LA64.

This is similar with commit 36e70b9b ("selftests, bpf: Fix broken
riscv build").
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/1677585781-21628-1-git-send-email-yangtiezhu@loongson.cn

Kumar Kartikeya Dwivedi says:

====================

This set adds support for kptrs in percpu hashmaps, percpu LRU hashmaps,
and local storage maps (covering sk, cgrp, task, inode).

Tests are expanded to test more existing maps at runtime and also test
the code path for the local storage maps (which is shared by all
implementations).

A question for reviewers is what the position of the BPF runtime should
be on dealing with reference cycles that can be created by BPF programs
at runtime using this additional support. For instance, one can store
the kptr of the task in its own task local storage, creating a cycle
which prevents destruction of task local storage. Cycles can be formed
using arbitrarily long kptr ownership chains. Therefore, just preventing
storage of such kptrs in some maps is not a sufficient solution, and is
more likely to hurt usability.

There is precedence in existing runtimes which promise memory safety,
like Rust, where reference cycles and memory leaks are permitted.
However, traditionally the safety guarantees of BPF have been stronger.
Thus, more discussion and thought is invited on this topic to ensure we
cover all usage aspects.

Changelog:
----------
v2 -> v3
v2: https://lore.kernel.org/bpf/20230221200646.2500777-1-memxor@gmail.com/

 * Fix a use-after-free bug in local storage patch
 * Fix selftest for aarch64 (don't use fentry/fmod_ret)
 * Wait for RCU Tasks Trace GP along with RCU GP in selftest

v1 -> v2
v1: https://lore.kernel.org/bpf/20230219155249.1755998-1-memxor@gmail.com

 * Simplify selftests, fix a couple of bugs
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Firstly, ensure programs successfully load when using all of the
supported maps. Then, extend existing tests to test more cases at
runtime. We are currently testing both the synchronous freeing of items
and asynchronous destruction when map is freed, but the code needs to be
adjusted a bit to be able to also accomodate support for percpu maps.

We now do a delete on the item (and update for array maps which has a
similar effect for kptrs) to perform a synchronous free of the kptr, and
test destruction both for the synchronous and asynchronous deletion.
Next time the program runs, it should observe the refcount as 1 since
all existing references should have been released by then. By running
the program after both possible paths freeing kptrs, we establish that
they correctly release resources. Next, we augment the existing test to
also test the same code path shared by all local storage maps using a
task local storage map.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20230225154010.391965-4-memxor@gmail.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

Enable support for kptrs in local storage maps by wiring up the freeing
of these kptrs from map value. Freeing of bpf_local_storage_map is only
delayed in case there are special fields, therefore bpf_selem_free_*
path can also only dereference smap safely in that case. This is
recorded using a bool utilizing a hole in bpF_local_storage_elem. It
could have been tagged in the pointer value smap using the lowest bit
(since alignment > 1), but since there was already a hole I went with
the simpler option. Only the map structure freeing is delayed using RCU
barriers, as the buckets aren't used when selem is being freed, so they
can be freed once all readers of the bucket lists can no longer access
it.

Cc: Martin KaFai Lau <martin.lau@kernel.org>
Cc: KP Singh <kpsingh@kernel.org>
Cc: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20230225154010.391965-3-memxor@gmail.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

Enable support for kptrs in percpu BPF hashmap and percpu BPF LRU
hashmap by wiring up the freeing of these kptrs from percpu map
elements.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20230225154010.391965-2-memxor@gmail.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

Joanne Koong says:

====================

This patchset is the 2nd in the dynptr series. The 1st can be found here [0].

This patchset adds skb and xdp type dynptrs, which have two main benefits for
packet parsing:
    * allowing operations on sizes that are not statically known at
      compile-time (eg variable-sized accesses).
    * more ergonomic and less brittle iteration through data (eg does not need
      manual if checking for being within bounds of data_end)

When comparing the differences in runtime for packet parsing without dynptrs
vs. with dynptrs, there is no noticeable difference. Patch 9 contains more
details as well as examples of how to use skb and xdp dynptrs.

[0] https://lore.kernel.org/bpf/20220523210712.3641569-1-joannelkoong@gmail.com/
---
Changelog:

v12 = https://lore.kernel.org/bpf/20230226085120.3907863-1-joannelkoong@gmail.com/
v12 -> v13:
    * Fix missing { } for case statement

v11 = https://lore.kernel.org/bpf/20230222060747.2562549-1-joannelkoong@gmail.com/
v11 -> v12:
    * Change constant mem size checking to use "__szk" kfunc annotation
      for slices
    * Use autoloading for success selftests

v10 = https://lore.kernel.org/bpf/20230216225524.1192789-1-joannelkoong@gmail.com/
v10 -> v11:
    * Reject bpf_dynptr_slice_rdwr() for non-writable progs at load time
      instead of runtime
    * Add additional patch (__uninit kfunc annotation)
    * Expand on documentation
    * Add bpf_dynptr_write() calls for persisting writes in tests

v9 = https://lore.kernel.org/bpf/20230127191703.3864860-1-joannelkoong@gmail.com/
v9 -> v10:
    * Add bpf_dynptr_slice and bpf_dynptr_slice_rdwr interface
    * Add some more tests
    * Split up patchset into more parts to make it easier to review

v8 = https://lore.kernel.org/bpf/20230126233439.3739120-1-joannelkoong@gmail.com/
v8 -> v9:
    * Fix dynptr_get_type() to check non-stack dynptrs

v7 = https://lore.kernel.org/bpf/20221021011510.1890852-1-joannelkoong@gmail.com/
v7 -> v8:
    * Change helpers to kfuncs
    * Add 2 new patches (1/5 and 2/5)

v6 = https://lore.kernel.org/bpf/20220907183129.745846-1-joannelkoong@gmail.com/
v6 -> v7
    * Change bpf_dynptr_data() to return read-only data slices if the skb prog
      is read-only (Martin)
    * Add test "skb_invalid_write" to test that writes to rd-only data slices
      are rejected

v5 = https://lore.kernel.org/bpf/20220831183224.3754305-1-joannelkoong@gmail.com/
v5 -> v6
    * Address kernel test robot errors by static inlining

v4 = https://lore.kernel.org/bpf/20220822235649.2218031-1-joannelkoong@gmail.com/
v4 -> v5
    * Address kernel test robot errors for configs w/out CONFIG_NET set
    * For data slices, return PTR_TO_MEM instead of PTR_TO_PACKET (Kumar)
    * Split selftests into subtests (Andrii)
    * Remove insn patching. Use rdonly and rdwr protos for dynptr skb
      construction (Andrii)
    * bpf_dynptr_data() returns NULL for rd-only dynptrs. There will be a
      separate bpf_dynptr_data_rdonly() added later (Andrii and Kumar)

v3 = https://lore.kernel.org/bpf/20220822193442.657638-1-joannelkoong@gmail.com/
v3 -> v4
    * Forgot to commit --amend the kernel test robot error fixups

v2 = https://lore.kernel.org/bpf/20220811230501.2632393-1-joannelkoong@gmail.com/
v2 -> v3
    * Fix kernel test robot build test errors

v1 = https://lore.kernel.org/bpf/20220726184706.954822-1-joannelkoong@gmail.com/
v1 -> v2
  * Return data slices to rd-only skb dynptrs (Martin)
  * bpf_dynptr_write allows writes to frags for skb dynptrs, but always
    invalidates associated data slices (Martin)
  * Use switch casing instead of ifs (Andrii)
  * Use 0xFD for experimental kind number in the selftest (Zvi)
  * Put selftest conversions w/ dynptrs into new files (Alexei)
  * Add new selftest "test_cls_redirect_dynptr.c"
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Test skb and xdp dynptr functionality in the following ways:

1) progs/test_cls_redirect_dynptr.c
   * Rewrite "progs/test_cls_redirect.c" test to use dynptrs to parse
     skb data

   * This is a great example of how dynptrs can be used to simplify a
     lot of the parsing logic for non-statically known values.

     When measuring the user + system time between the original version
     vs. using dynptrs, and averaging the time for 10 runs (using
     "time ./test_progs -t cls_redirect"):
         original version: 0.092 sec
         with dynptrs: 0.078 sec

2) progs/test_xdp_dynptr.c
   * Rewrite "progs/test_xdp.c" test to use dynptrs to parse xdp data

     When measuring the user + system time between the original version
     vs. using dynptrs, and averaging the time for 10 runs (using
     "time ./test_progs -t xdp_attach"):
         original version: 0.118 sec
         with dynptrs: 0.094 sec

3) progs/test_l4lb_noinline_dynptr.c
   * Rewrite "progs/test_l4lb_noinline.c" test to use dynptrs to parse
     skb data

     When measuring the user + system time between the original version
     vs. using dynptrs, and averaging the time for 10 runs (using
     "time ./test_progs -t l4lb_all"):
         original version: 0.062 sec
         with dynptrs: 0.081 sec

     For number of processed verifier instructions:
         original version: 6268 insns
         with dynptrs: 2588 insns

4) progs/test_parse_tcp_hdr_opt_dynptr.c
   * Add sample code for parsing tcp hdr opt lookup using dynptrs.
     This logic is lifted from a real-world use case of packet parsing
     in katran [0], a layer 4 load balancer. The original version
     "progs/test_parse_tcp_hdr_opt.c" (not using dynptrs) is included
     here as well, for comparison.

     When measuring the user + system time between the original version
     vs. using dynptrs, and averaging the time for 10 runs (using
     "time ./test_progs -t parse_tcp_hdr_opt"):
         original version: 0.031 sec
         with dynptrs: 0.045 sec

5) progs/dynptr_success.c
   * Add test case "test_skb_readonly" for testing attempts at writes
     on a prog type with read-only skb ctx.
   * Add "test_dynptr_skb_data" for testing that bpf_dynptr_data isn't
     supported for skb progs.

6) progs/dynptr_fail.c
   * Add test cases "skb_invalid_data_slice{1,2,3,4}" and
     "xdp_invalid_data_slice{1,2}" for testing that helpers that modify the
     underlying packet buffer automatically invalidate the associated
     data slice.
   * Add test cases "skb_invalid_ctx" and "xdp_invalid_ctx" for testing
     that prog types that do not support bpf_dynptr_from_skb/xdp don't
     have access to the API.
   * Add test case "dynptr_slice_var_len{1,2}" for testing that
     variable-sized len can't be passed in to bpf_dynptr_slice
   * Add test case "skb_invalid_slice_write" for testing that writes to a
     read-only data slice are rejected by the verifier.
   * Add test case "data_slice_out_of_bounds_skb" for testing that
     writes to an area outside the slice are rejected.
   * Add test case "invalid_slice_rdwr_rdonly" for testing that prog
     types that don't allow writes to packet data don't accept any calls
     to bpf_dynptr_slice_rdwr.

[0] https://github.com/facebookincubator/katran/blob/main/katran/lib/bpf/pckt_parsing.hSigned-off-by: Joanne Koong <joannelkoong@gmail.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230301154953.641654-11-joannelkoong@gmail.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

Two new kfuncs are added, bpf_dynptr_slice and bpf_dynptr_slice_rdwr.
The user must pass in a buffer to store the contents of the data slice
if a direct pointer to the data cannot be obtained.

For skb and xdp type dynptrs, these two APIs are the only way to obtain
a data slice. However, for other types of dynptrs, there is no
difference between bpf_dynptr_slice(_rdwr) and bpf_dynptr_data.

For skb type dynptrs, the data is copied into the user provided buffer
if any of the data is not in the linear portion of the skb. For xdp type
dynptrs, the data is copied into the user provided buffer if the data is
between xdp frags.

If the skb is cloned and a call to bpf_dynptr_data_rdwr is made, then
the skb will be uncloned (see bpf_unclone_prologue()).

Please note that any bpf_dynptr_write() automatically invalidates any prior
data slices of the skb dynptr. This is because the skb may be cloned or
may need to pull its paged buffer into the head. As such, any
bpf_dynptr_write() will automatically have its prior data slices
invalidated, even if the write is to data in the skb head of an uncloned
skb. Please note as well that any other helper calls that change the
underlying packet buffer (eg bpf_skb_pull_data()) invalidates any data
slices of the skb dynptr as well, for the same reasons.
Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Link: https://lore.kernel.org/r/20230301154953.641654-10-joannelkoong@gmail.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

Add xdp dynptrs, which are dynptrs whose underlying pointer points
to a xdp_buff. The dynptr acts on xdp data. xdp dynptrs have two main
benefits. One is that they allow operations on sizes that are not
statically known at compile-time (eg variable-sized accesses).
Another is that parsing the packet data through dynptrs (instead of
through direct access of xdp->data and xdp->data_end) can be more
ergonomic and less brittle (eg does not need manual if checking for
being within bounds of data_end).

For reads and writes on the dynptr, this includes reading/writing
from/to and across fragments. Data slices through the bpf_dynptr_data
API are not supported; instead bpf_dynptr_slice() and
bpf_dynptr_slice_rdwr() should be used.

For examples of how xdp dynptrs can be used, please see the attached
selftests.
Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Link: https://lore.kernel.org/r/20230301154953.641654-9-joannelkoong@gmail.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

Add skb dynptrs, which are dynptrs whose underlying pointer points
to a skb. The dynptr acts on skb data. skb dynptrs have two main
benefits. One is that they allow operations on sizes that are not
statically known at compile-time (eg variable-sized accesses).
Another is that parsing the packet data through dynptrs (instead of
through direct access of skb->data and skb->data_end) can be more
ergonomic and less brittle (eg does not need manual if checking for
being within bounds of data_end).

For bpf prog types that don't support writes on skb data, the dynptr is
read-only (bpf_dynptr_write() will return an error)

For reads and writes through the bpf_dynptr_read() and bpf_dynptr_write()
interfaces, reading and writing from/to data in the head as well as from/to
non-linear paged buffers is supported. Data slices through the
bpf_dynptr_data API are not supported; instead bpf_dynptr_slice() and
bpf_dynptr_slice_rdwr() (added in subsequent commit) should be used.

For examples of how skb dynptrs can be used, please see the attached
selftests.
Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Link: https://lore.kernel.org/r/20230301154953.641654-8-joannelkoong@gmail.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

This patch adds __uninit as a kfunc annotation.

This will be useful for scenarios such as for example in dynptrs,
indicating whether the dynptr should be checked by the verifier as an
initialized or an uninitialized dynptr.

Without this annotation, the alternative would be needing to hard-code
in the verifier the specific kfunc to indicate that arg should be
treated as an uninitialized arg.
Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Link: https://lore.kernel.org/r/20230301154953.641654-7-joannelkoong@gmail.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

This commit refactors the logic for determining which register in a
function is the dynptr into "get_dynptr_arg_reg". This will be used
in the future when the dynptr reg for BPF_FUNC_dynptr_write will need
to be obtained in order to support writes for skb dynptrs.
Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Link: https://lore.kernel.org/r/20230301154953.641654-6-joannelkoong@gmail.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

Some bpf dynptr functions will be called from places where
if CONFIG_BPF_SYSCALL is not set, then the dynptr function is
undefined. For example, when skb type dynptrs are added in the
next commit, dynptr functions are called from net/core/filter.c

This patch defines no-op implementations of these dynptr functions
so that they do not break compilation by being an undefined reference.
Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Link: https://lore.kernel.org/r/20230301154953.641654-5-joannelkoong@gmail.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

This change allows kfuncs to take in an uninitialized dynptr as a
parameter. Before this change, only helper functions could successfully
use uninitialized dynptrs. This change moves the memory access check
(including stack state growing and slot marking) into
process_dynptr_func(), which both helpers and kfuncs call into.
Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Link: https://lore.kernel.org/r/20230301154953.641654-4-joannelkoong@gmail.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

This change cleans up process_dynptr_func's flow to be more intuitive
and updates some comments with more context.
Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Link: https://lore.kernel.org/r/20230301154953.641654-3-joannelkoong@gmail.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

The bpf mirror of the in-kernel sk_buff and xdp_buff data structures are
__sk_buff and xdp_md. Currently, when we pass in the program ctx to a
kfunc where the program ctx is a skb or xdp buffer, we reject the
program if the in-kernel definition is sk_buff/xdp_buff instead of
__sk_buff/xdp_md.

This change allows "sk_buff <--> __sk_buff" and "xdp_buff <--> xdp_md"
to be recognized as valid matches. The user program may pass in their
program ctx as a __sk_buff or xdp_md, and the in-kernel definition
of the kfunc may define this arg as a sk_buff or xdp_buff.
Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Link: https://lore.kernel.org/r/20230301154953.641654-2-joannelkoong@gmail.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

[Changes from V4:
- s/regs:16/regs:8 in figure.]

[Changes from V3:
- Back to src_reg and dst_reg, since they denote register numbers
  as opposed to the values stored in these registers.]

[Changes from V2:
- Use src and dst consistently in the document.
- Use a more graphical depiction of the 128-bit instruction.
- Remove `Where:' fragment.
- Clarify that unused bits are reserved and shall be zeroed.]

[Changes from V1:
- Use rst literal blocks for figures.
- Avoid using | in the basic instruction/pseudo instruction figure.
- Rebased to today's bpf-next master branch.]

This patch modifies instruction-set.rst so it documents the encoding
of BPF instructions in terms of how the bytes are stored (be it in an
ELF file or as bytes in a memory buffer to be loaded into the kernel
or some other BPF consumer) as opposed to how the instruction looks
like once loaded.

This is hopefully easier to understand by implementors looking to
generate and/or consume bytes conforming BPF instructions.

The patch also clarifies that the unused bytes in a pseudo-instruction
shall be cleared with zeros.
Signed-off-by: Jose E. Marchesi <jose.marchesi@oracle.com>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/87h6v6i0da.fsf_-_@oracle.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>