Daniel Borkmann says:

====================
pull-request: bpf-next 2023-04-13

We've added 260 non-merge commits during the last 36 day(s) which contain
a total of 356 files changed, 21786 insertions(+), 11275 deletions(-).

The main changes are:

1) Rework BPF verifier log behavior and implement it as a rotating log
   by default with the option to retain old-style fixed log behavior,
   from Andrii Nakryiko.

2) Adds support for using {FOU,GUE} encap with an ipip device operating
   in collect_md mode and add a set of BPF kfuncs for controlling encap
   params, from Christian Ehrig.

3) Allow BPF programs to detect at load time whether a particular kfunc
   exists or not, and also add support for this in light skeleton,
   from Alexei Starovoitov.

4) Optimize hashmap lookups when key size is multiple of 4,
   from Anton Protopopov.

5) Enable RCU semantics for task BPF kptrs and allow referenced kptr
   tasks to be stored in BPF maps, from David Vernet.

6) Add support for stashing local BPF kptr into a map value via
   bpf_kptr_xchg(). This is useful e.g. for rbtree node creation
   for new cgroups, from Dave Marchevsky.

7) Fix BTF handling of is_int_ptr to skip modifiers to work around
   tracing issues where a program cannot be attached, from Feng Zhou.

8) Migrate a big portion of test_verifier unit tests over to
   test_progs -a verifier_* via inline asm to ease {read,debug}ability,
   from Eduard Zingerman.

9) Several updates to the instruction-set.rst documentation
   which is subject to future IETF standardization
   (https://lwn.net/Articles/926882/), from Dave Thaler.

10) Fix BPF verifier in the __reg_bound_offset's 64->32 tnum sub-register
    known bits information propagation, from Daniel Borkmann.

11) Add skb bitfield compaction work related to BPF with the overall goal
    to make more of the sk_buff bits optional, from Jakub Kicinski.

12) BPF selftest cleanups for build id extraction which stand on its own
    from the upcoming integration work of build id into struct file object,
    from Jiri Olsa.

13) Add fixes and optimizations for xsk descriptor validation and several
    selftest improvements for xsk sockets, from Kal Conley.

14) Add BPF links for struct_ops and enable switching implementations
    of BPF TCP cong-ctls under a given name by replacing backing
    struct_ops map, from Kui-Feng Lee.

15) Remove a misleading BPF verifier env->bypass_spec_v1 check on variable
    offset stack read as earlier Spectre checks cover this,
    from Luis Gerhorst.

16) Fix issues in copy_from_user_nofault() for BPF and other tracers
    to resemble copy_from_user_nmi() from safety PoV, from Florian Lehner
    and Alexei Starovoitov.

17) Add --json-summary option to test_progs in order for CI tooling to
    ease parsing of test results, from Manu Bretelle.

18) Batch of improvements and refactoring to prep for upcoming
    bpf_local_storage conversion to bpf_mem_cache_{alloc,free} allocator,
    from Martin KaFai Lau.

19) Improve bpftool's visual program dump which produces the control
    flow graph in a DOT format by adding C source inline annotations,
    from Quentin Monnet.

20) Fix attaching fentry/fexit/fmod_ret/lsm to modules by extracting
    the module name from BTF of the target and searching kallsyms of
    the correct module, from Viktor Malik.

21) Improve BPF verifier handling of '<const> <cond> <non_const>'
    to better detect whether in particular jmp32 branches are taken,
    from Yonghong Song.

22) Allow BPF TCP cong-ctls to write app_limited of struct tcp_sock.
    A built-in cc or one from a kernel module is already able to write
    to app_limited, from Yixin Shen.

Conflicts:

Documentation/bpf/bpf_devel_QA.rst
  b7abcd9c656b ("bpf, doc: Link to submitting-patches.rst for general patch submission info")
  0f10f647f455 ("bpf, docs: Use internal linking for link to netdev subsystem doc")
https://lore.kernel.org/all/20230307095812.236eb1be@canb.auug.org.au/

include/net/ip_tunnels.h
  bc9d003dc48c3 ("ip_tunnel: Preserve pointer const in ip_tunnel_info_opts")
  ac931d4cdec3d ("ipip,ip_tunnel,sit: Add FOU support for externally controlled ipip devices")
https://lore.kernel.org/all/20230413161235.4093777-1-broonie@kernel.org/

net/bpf/test_run.c
  e5995bc7e2ba ("bpf, test_run: fix crashes due to XDP frame overwriting/corruption")
  294635a8165a ("bpf, test_run: fix &xdp_frame misplacement for LIVE_FRAMES")
https://lore.kernel.org/all/20230320102619.05b80a98@canb.auug.org.au/
====================

Link: https://lore.kernel.org/r/20230413191525.7295-1-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

8 files changed, 451 insertions, 141 deletions

diff --git a/Documentation/bpf/bpf_devel_QA.rst b/Documentation/bpf/bpf_devel_QA.rst
index 7403f81c995c..609b71f5747d 100644
--- a/Documentation/bpf/bpf_devel_QA.rst
+++ b/Documentation/bpf/bpf_devel_QA.rst
@@ -128,7 +128,8 @@ into the bpf-next tree will make their way into net-next tree. net and
 net-next are both run by David S. Miller. From there, they will go
 into the kernel mainline tree run by Linus Torvalds. To read up on the
 process of net and net-next being merged into the mainline tree, see
-the `netdev-FAQ`_.
+the documentation on netdev subsystem at
+Documentation/process/maintainer-netdev.rst.
 
 
 
@@ -147,7 +148,8 @@ request)::
 Q: How do I indicate which tree (bpf vs. bpf-next) my patch should be applied to?
 ---------------------------------------------------------------------------------
 
-A: The process is the very same as described in the `netdev-FAQ`_,
+A: The process is the very same as described in the netdev subsystem
+documentation at Documentation/process/maintainer-netdev.rst,
 so please read up on it. The subject line must indicate whether the
 patch is a fix or rather "next-like" content in order to let the
 maintainers know whether it is targeted at bpf or bpf-next.
@@ -206,8 +208,9 @@ ii) run extensive BPF test suite and
 Once the BPF pull request was accepted by David S. Miller, then
 the patches end up in net or net-next tree, respectively, and
 make their way from there further into mainline. Again, see the
-`netdev-FAQ`_ for additional information e.g. on how often they are
-merged to mainline.
+documentation for netdev subsystem at
+Documentation/process/maintainer-netdev.rst for additional information
+e.g. on how often they are merged to mainline.
 
 Q: How long do I need to wait for feedback on my BPF patches?
 -------------------------------------------------------------
@@ -230,7 +233,8 @@ Q: Are patches applied to bpf-next when the merge window is open?
 -----------------------------------------------------------------
 A: For the time when the merge window is open, bpf-next will not be
 processed. This is roughly analogous to net-next patch processing,
-so feel free to read up on the `netdev-FAQ`_ about further details.
+so feel free to read up on the netdev docs at
+Documentation/process/maintainer-netdev.rst about further details.
 
 During those two weeks of merge window, we might ask you to resend
 your patch series once bpf-next is open again. Once Linus released
@@ -394,7 +398,8 @@ netdev kernel mailing list in Cc and ask for the fix to be queued up:
   netdev@vger.kernel.org
 
 The process in general is the same as on netdev itself, see also the
-`netdev-FAQ`_.
+the documentation on networking subsystem at
+Documentation/process/maintainer-netdev.rst.
 
 Q: Do you also backport to kernels not currently maintained as stable?
 ----------------------------------------------------------------------
@@ -410,7 +415,7 @@ Q: The BPF patch I am about to submit needs to go to stable as well
 What should I do?
 
 A: The same rules apply as with netdev patch submissions in general, see
-the `netdev-FAQ`_.
+the netdev docs at Documentation/process/maintainer-netdev.rst.
 
 Never add "``Cc: stable@vger.kernel.org``" to the patch description, but
 ask the BPF maintainers to queue the patches instead. This can be done
@@ -684,7 +689,6 @@ when:
 
 
 .. Links
-.. _netdev-FAQ: https://www.kernel.org/doc/html/latest/process/maintainer-netdev.html
 .. _selftests:
    https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/testing/selftests/bpf/
 
diff --git a/Documentation/bpf/clang-notes.rst b/Documentation/bpf/clang-notes.rst
index 528feddf2db9..2c872a1ee08e 100644
--- a/Documentation/bpf/clang-notes.rst
+++ b/Documentation/bpf/clang-notes.rst
@@ -20,6 +20,12 @@ Arithmetic instructions
 For CPU versions prior to 3, Clang v7.0 and later can enable ``BPF_ALU`` support with
 ``-Xclang -target-feature -Xclang +alu32``.  In CPU version 3, support is automatically included.
 
+Jump instructions
+=================
+
+If ``-O0`` is used, Clang will generate the ``BPF_CALL | BPF_X | BPF_JMP`` (0x8d)
+instruction, which is not supported by the Linux kernel verifier.
+
 Atomic operations
 =================
 
diff --git a/Documentation/bpf/cpumasks.rst b/Documentation/bpf/cpumasks.rst
index 75344cd230e5..41efd8874eeb 100644
--- a/Documentation/bpf/cpumasks.rst
+++ b/Documentation/bpf/cpumasks.rst
@@ -117,12 +117,7 @@ For example:
 As mentioned and illustrated above, these ``struct bpf_cpumask *`` objects can
 also be stored in a map and used as kptrs. If a ``struct bpf_cpumask *`` is in
 a map, the reference can be removed from the map with bpf_kptr_xchg(), or
-opportunistically acquired with bpf_cpumask_kptr_get():
-
-.. kernel-doc:: kernel/bpf/cpumask.c
-  :identifiers: bpf_cpumask_kptr_get
-
-Here is an example of a ``struct bpf_cpumask *`` being retrieved from a map:
+opportunistically acquired using RCU:
 
 .. code-block:: c
 
@@ -144,7 +139,7 @@ Here is an example of a ``struct bpf_cpumask *`` being retrieved from a map:
 	/**
 	 * A simple example tracepoint program showing how a
 	 * struct bpf_cpumask * kptr that is stored in a map can
-	 * be acquired using the bpf_cpumask_kptr_get() kfunc.
+	 * be passed to kfuncs using RCU protection.
 	 */
 	SEC("tp_btf/cgroup_mkdir")
 	int BPF_PROG(cgrp_ancestor_example, struct cgroup *cgrp, const char *path)
@@ -158,26 +153,21 @@ Here is an example of a ``struct bpf_cpumask *`` being retrieved from a map:
 		if (!v)
 			return -ENOENT;
 
+		bpf_rcu_read_lock();
 		/* Acquire a reference to the bpf_cpumask * kptr that's already stored in the map. */
-		kptr = bpf_cpumask_kptr_get(&v->cpumask);
-		if (!kptr)
+		kptr = v->cpumask;
+		if (!kptr) {
 			/* If no bpf_cpumask was present in the map, it's because
 			 * we're racing with another CPU that removed it with
 			 * bpf_kptr_xchg() between the bpf_map_lookup_elem()
-			 * above, and our call to bpf_cpumask_kptr_get().
-			 * bpf_cpumask_kptr_get() internally safely handles this
-			 * race, and will return NULL if the cpumask is no longer
-			 * present in the map by the time we invoke the kfunc.
+			 * above, and our load of the pointer from the map.
 			 */
+			bpf_rcu_read_unlock();
 			return -EBUSY;
+		}
 
-		/* Free the reference we just took above. Note that the
-		 * original struct bpf_cpumask * kptr is still in the map. It will
-		 * be freed either at a later time if another context deletes
-		 * it from the map, or automatically by the BPF subsystem if
-		 * it's still present when the map is destroyed.
-		 */
-		bpf_cpumask_release(kptr);
+		bpf_cpumask_setall(kptr);
+		bpf_rcu_read_unlock();
 
 		return 0;
 	}
diff --git a/Documentation/bpf/instruction-set.rst b/Documentation/bpf/instruction-set.rst
index db8789e6969e..492980ece1ab 100644
--- a/Documentation/bpf/instruction-set.rst
+++ b/Documentation/bpf/instruction-set.rst
@@ -11,7 +11,8 @@ Documentation conventions
 =========================
 
 For brevity, this document uses the type notion "u64", "u32", etc.
-to mean an unsigned integer whose width is the specified number of bits.
+to mean an unsigned integer whose width is the specified number of bits,
+and "s32", etc. to mean a signed integer of the specified number of bits.
 
 Registers and calling convention
 ================================
@@ -242,28 +243,58 @@ Jump instructions
 otherwise identical operations.
 The 'code' field encodes the operation as below:
 
-========  =====  =========================  ============
-code      value  description                notes
-========  =====  =========================  ============
-BPF_JA    0x00   PC += off                  BPF_JMP only
-BPF_JEQ   0x10   PC += off if dst == src
-BPF_JGT   0x20   PC += off if dst > src     unsigned
-BPF_JGE   0x30   PC += off if dst >= src    unsigned
-BPF_JSET  0x40   PC += off if dst & src
-BPF_JNE   0x50   PC += off if dst != src
-BPF_JSGT  0x60   PC += off if dst > src     signed
-BPF_JSGE  0x70   PC += off if dst >= src    signed
-BPF_CALL  0x80   function call
-BPF_EXIT  0x90   function / program return  BPF_JMP only
-BPF_JLT   0xa0   PC += off if dst < src     unsigned
-BPF_JLE   0xb0   PC += off if dst <= src    unsigned
-BPF_JSLT  0xc0   PC += off if dst < src     signed
-BPF_JSLE  0xd0   PC += off if dst <= src    signed
-========  =====  =========================  ============
+========  =====  ===  ===========================================  =========================================
+code      value  src  description                                  notes
+========  =====  ===  ===========================================  =========================================
+BPF_JA    0x0    0x0  PC += offset                                 BPF_JMP only
+BPF_JEQ   0x1    any  PC += offset if dst == src
+BPF_JGT   0x2    any  PC += offset if dst > src                    unsigned
+BPF_JGE   0x3    any  PC += offset if dst >= src                   unsigned
+BPF_JSET  0x4    any  PC += offset if dst & src
+BPF_JNE   0x5    any  PC += offset if dst != src
+BPF_JSGT  0x6    any  PC += offset if dst > src                    signed
+BPF_JSGE  0x7    any  PC += offset if dst >= src                   signed
+BPF_CALL  0x8    0x0  call helper function by address              see `Helper functions`_
+BPF_CALL  0x8    0x1  call PC += offset                            see `Program-local functions`_
+BPF_CALL  0x8    0x2  call helper function by BTF ID               see `Helper functions`_
+BPF_EXIT  0x9    0x0  return                                       BPF_JMP only
+BPF_JLT   0xa    any  PC += offset if dst < src                    unsigned
+BPF_JLE   0xb    any  PC += offset if dst <= src                   unsigned
+BPF_JSLT  0xc    any  PC += offset if dst < src                    signed
+BPF_JSLE  0xd    any  PC += offset if dst <= src                   signed
+========  =====  ===  ===========================================  =========================================
 
 The eBPF program needs to store the return value into register R0 before doing a
-BPF_EXIT.
+``BPF_EXIT``.
 
+Example:
+
+``BPF_JSGE | BPF_X | BPF_JMP32`` (0x7e) means::
+
+  if (s32)dst s>= (s32)src goto +offset
+
+where 's>=' indicates a signed '>=' comparison.
+
+Helper functions
+~~~~~~~~~~~~~~~~
+
+Helper functions are a concept whereby BPF programs can call into a
+set of function calls exposed by the underlying platform.
+
+Historically, each helper function was identified by an address
+encoded in the imm field.  The available helper functions may differ
+for each program type, but address values are unique across all program types.
+
+Platforms that support the BPF Type Format (BTF) support identifying
+a helper function by a BTF ID encoded in the imm field, where the BTF ID
+identifies the helper name and type.
+
+Program-local functions
+~~~~~~~~~~~~~~~~~~~~~~~
+Program-local functions are functions exposed by the same BPF program as the
+caller, and are referenced by offset from the call instruction, similar to
+``BPF_JA``.  A ``BPF_EXIT`` within the program-local function will return to
+the caller.
 
 Load and store instructions
 ===========================
@@ -385,14 +416,56 @@ and loaded back to ``R0``.
 -----------------------------
 
 Instructions with the ``BPF_IMM`` 'mode' modifier use the wide instruction
-encoding for an extra imm64 value.
-
-There is currently only one such instruction.
-
-``BPF_LD | BPF_DW | BPF_IMM`` means::
-
-  dst = imm64
-
+encoding defined in `Instruction encoding`_, and use the 'src' field of the
+basic instruction to hold an opcode subtype.
+
+The following table defines a set of ``BPF_IMM | BPF_DW | BPF_LD`` instructions
+with opcode subtypes in the 'src' field, using new terms such as "map"
+defined further below:
+
+=========================  ======  ===  =========================================  ===========  ==============
+opcode construction        opcode  src  pseudocode                                 imm type     dst type
+=========================  ======  ===  =========================================  ===========  ==============
+BPF_IMM | BPF_DW | BPF_LD  0x18    0x0  dst = imm64                                integer      integer
+BPF_IMM | BPF_DW | BPF_LD  0x18    0x1  dst = map_by_fd(imm)                       map fd       map
+BPF_IMM | BPF_DW | BPF_LD  0x18    0x2  dst = map_val(map_by_fd(imm)) + next_imm   map fd       data pointer
+BPF_IMM | BPF_DW | BPF_LD  0x18    0x3  dst = var_addr(imm)                        variable id  data pointer
+BPF_IMM | BPF_DW | BPF_LD  0x18    0x4  dst = code_addr(imm)                       integer      code pointer
+BPF_IMM | BPF_DW | BPF_LD  0x18    0x5  dst = map_by_idx(imm)                      map index    map
+BPF_IMM | BPF_DW | BPF_LD  0x18    0x6  dst = map_val(map_by_idx(imm)) + next_imm  map index    data pointer
+=========================  ======  ===  =========================================  ===========  ==============
+
+where
+
+* map_by_fd(imm) means to convert a 32-bit file descriptor into an address of a map (see `Maps`_)
+* map_by_idx(imm) means to convert a 32-bit index into an address of a map
+* map_val(map) gets the address of the first value in a given map
+* var_addr(imm) gets the address of a platform variable (see `Platform Variables`_) with a given id
+* code_addr(imm) gets the address of the instruction at a specified relative offset in number of (64-bit) instructions
+* the 'imm type' can be used by disassemblers for display
+* the 'dst type' can be used for verification and JIT compilation purposes
+
+Maps
+~~~~
+
+Maps are shared memory regions accessible by eBPF programs on some platforms.
+A map can have various semantics as defined in a separate document, and may or
+may not have a single contiguous memory region, but the 'map_val(map)' is
+currently only defined for maps that do have a single contiguous memory region.
+
+Each map can have a file descriptor (fd) if supported by the platform, where
+'map_by_fd(imm)' means to get the map with the specified file descriptor. Each
+BPF program can also be defined to use a set of maps associated with the
+program at load time, and 'map_by_idx(imm)' means to get the map with the given
+index in the set associated with the BPF program containing the instruction.
+
+Platform Variables
+~~~~~~~~~~~~~~~~~~
+
+Platform variables are memory regions, identified by integer ids, exposed by
+the runtime and accessible by BPF programs on some platforms.  The
+'var_addr(imm)' operation means to get the address of the memory region
+identified by the given id.
 
 Legacy BPF Packet access instructions
 -------------------------------------
diff --git a/Documentation/bpf/kfuncs.rst b/Documentation/bpf/kfuncs.rst
index 69eccf6f98ef..3b42cfe12437 100644
--- a/Documentation/bpf/kfuncs.rst
+++ b/Documentation/bpf/kfuncs.rst
@@ -179,9 +179,10 @@ both are orthogonal to each other.
 ---------------------
 
 The KF_RELEASE flag is used to indicate that the kfunc releases the pointer
-passed in to it. There can be only one referenced pointer that can be passed in.
-All copies of the pointer being released are invalidated as a result of invoking
-kfunc with this flag.
+passed in to it. There can be only one referenced pointer that can be passed
+in. All copies of the pointer being released are invalidated as a result of
+invoking kfunc with this flag. KF_RELEASE kfuncs automatically receive the
+protection afforded by the KF_TRUSTED_ARGS flag described below.
 
 2.4.4 KF_KPTR_GET flag
 ----------------------
@@ -470,13 +471,50 @@ struct_ops callback arg. For example:
 		struct task_struct *acquired;
 
 		acquired = bpf_task_acquire(task);
+		if (acquired)
+			/*
+			 * In a typical program you'd do something like store
+			 * the task in a map, and the map will automatically
+			 * release it later. Here, we release it manually.
+			 */
+			bpf_task_release(acquired);
+		return 0;
+	}
+
+
+References acquired on ``struct task_struct *`` objects are RCU protected.
+Therefore, when in an RCU read region, you can obtain a pointer to a task
+embedded in a map value without having to acquire a reference:
+
+.. code-block:: c
+
+	#define private(name) SEC(".data." #name) __hidden __attribute__((aligned(8)))
+	private(TASK) static struct task_struct *global;
+
+	/**
+	 * A trivial example showing how to access a task stored
+	 * in a map using RCU.
+	 */
+	SEC("tp_btf/task_newtask")
+	int BPF_PROG(task_rcu_read_example, struct task_struct *task, u64 clone_flags)
+	{
+		struct task_struct *local_copy;
+
+		bpf_rcu_read_lock();
+		local_copy = global;
+		if (local_copy)
+			/*
+			 * We could also pass local_copy to kfuncs or helper functions here,
+			 * as we're guaranteed that local_copy will be valid until we exit
+			 * the RCU read region below.
+			 */
+			bpf_printk("Global task %s is valid", local_copy->comm);
+		else
+			bpf_printk("No global task found");
+		bpf_rcu_read_unlock();
+
+		/* At this point we can no longer reference local_copy. */
 
-		/*
-		 * In a typical program you'd do something like store
-		 * the task in a map, and the map will automatically
-		 * release it later. Here, we release it manually.
-		 */
-		bpf_task_release(acquired);
 		return 0;
 	}
 
@@ -534,74 +572,6 @@ bpf_task_release() respectively, so we won't provide examples for them.
 
 ----
 
-You may also acquire a reference to a ``struct cgroup`` kptr that's already
-stored in a map using bpf_cgroup_kptr_get():
-
-.. kernel-doc:: kernel/bpf/helpers.c
-   :identifiers: bpf_cgroup_kptr_get
-
-Here's an example of how it can be used:
-
-.. code-block:: c
-
-	/* struct containing the struct task_struct kptr which is actually stored in the map. */
-	struct __cgroups_kfunc_map_value {
-		struct cgroup __kptr * cgroup;
-	};
-
-	/* The map containing struct __cgroups_kfunc_map_value entries. */
-	struct {
-		__uint(type, BPF_MAP_TYPE_HASH);
-		__type(key, int);
-		__type(value, struct __cgroups_kfunc_map_value);
-		__uint(max_entries, 1);
-	} __cgroups_kfunc_map SEC(".maps");
-
-	/* ... */
-
-	/**
-	 * A simple example tracepoint program showing how a
-	 * struct cgroup kptr that is stored in a map can
-	 * be acquired using the bpf_cgroup_kptr_get() kfunc.
-	 */
-	 SEC("tp_btf/cgroup_mkdir")
-	 int BPF_PROG(cgroup_kptr_get_example, struct cgroup *cgrp, const char *path)
-	 {
-		struct cgroup *kptr;
-		struct __cgroups_kfunc_map_value *v;
-		s32 id = cgrp->self.id;
-
-		/* Assume a cgroup kptr was previously stored in the map. */
-		v = bpf_map_lookup_elem(&__cgroups_kfunc_map, &id);
-		if (!v)
-			return -ENOENT;
-
-		/* Acquire a reference to the cgroup kptr that's already stored in the map. */
-		kptr = bpf_cgroup_kptr_get(&v->cgroup);
-		if (!kptr)
-			/* If no cgroup was present in the map, it's because
-			 * we're racing with another CPU that removed it with
-			 * bpf_kptr_xchg() between the bpf_map_lookup_elem()
-			 * above, and our call to bpf_cgroup_kptr_get().
-			 * bpf_cgroup_kptr_get() internally safely handles this
-			 * race, and will return NULL if the task is no longer
-			 * present in the map by the time we invoke the kfunc.
-			 */
-			return -EBUSY;
-
-		/* Free the reference we just took above. Note that the
-		 * original struct cgroup kptr is still in the map. It will
-		 * be freed either at a later time if another context deletes
-		 * it from the map, or automatically by the BPF subsystem if
-		 * it's still present when the map is destroyed.
-		 */
-		bpf_cgroup_release(kptr);
-
-		return 0;
-        }
-
-----
-
 Other kfuncs available for interacting with ``struct cgroup *`` objects are
 bpf_cgroup_ancestor() and bpf_cgroup_from_id(), allowing callers to access
 the ancestor of a cgroup and find a cgroup by its ID, respectively. Both
diff --git a/Documentation/bpf/libbpf/index.rst b/Documentation/bpf/libbpf/index.rst
index f9b3b252e28f..7545a2049692 100644
--- a/Documentation/bpf/libbpf/index.rst
+++ b/Documentation/bpf/libbpf/index.rst
@@ -2,23 +2,32 @@
 
 .. _libbpf:
 
+======
 libbpf
 ======
 
+If you are looking to develop BPF applications using the libbpf library, this
+directory contains important documentation that you should read.
+
+To get started, it is recommended to begin with the :doc:`libbpf Overview
+<libbpf_overview>` document, which provides a high-level understanding of the
+libbpf APIs and their usage. This will give you a solid foundation to start
+exploring and utilizing the various features of libbpf to develop your BPF
+applications.
+
 .. toctree::
    :maxdepth: 1
 
+   libbpf_overview
    API Documentation <https://libbpf.readthedocs.io/en/latest/api.html>
    program_types
    libbpf_naming_convention
    libbpf_build
 
-This is documentation for libbpf, a userspace library for loading and
-interacting with bpf programs.
 
-All general BPF questions, including kernel functionality, libbpf APIs and
-their application, should be sent to bpf@vger.kernel.org mailing list.
-You can `subscribe <http://vger.kernel.org/vger-lists.html#bpf>`_ to the
-mailing list search its `archive <https://lore.kernel.org/bpf/>`_.
-Please search the archive before asking new questions. It very well might
-be that this was already addressed or answered before.
+All general BPF questions, including kernel functionality, libbpf APIs and their
+application, should be sent to bpf@vger.kernel.org mailing list.  You can
+`subscribe <http://vger.kernel.org/vger-lists.html#bpf>`_ to the mailing list
+search its `archive <https://lore.kernel.org/bpf/>`_.  Please search the archive
+before asking new questions. It may be that this was already addressed or
+answered before.
diff --git a/Documentation/bpf/libbpf/libbpf_overview.rst b/Documentation/bpf/libbpf/libbpf_overview.rst
new file mode 100644
index 000000000000..f36a2d4ffea2
--- /dev/null
+++ b/Documentation/bpf/libbpf/libbpf_overview.rst
@@ -0,0 +1,228 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===============
+libbpf Overview
+===============
+
+libbpf is a C-based library containing a BPF loader that takes compiled BPF
+object files and prepares and loads them into the Linux kernel. libbpf takes the
+heavy lifting of loading, verifying, and attaching BPF programs to various
+kernel hooks, allowing BPF application developers to focus only on BPF program
+correctness and performance.
+
+The following are the high-level features supported by libbpf:
+
+* Provides high-level and low-level APIs for user space programs to interact
+  with BPF programs. The low-level APIs wrap all the bpf system call
+  functionality, which is useful when users need more fine-grained control
+  over the interactions between user space and BPF programs.
+* Provides overall support for the BPF object skeleton generated by bpftool.
+  The skeleton file simplifies the process for the user space programs to access
+  global variables and work with BPF programs.
+* Provides BPF-side APIS, including BPF helper definitions, BPF maps support,
+  and tracing helpers, allowing developers to simplify BPF code writing.
+* Supports BPF CO-RE mechanism, enabling BPF developers to write portable
+  BPF programs that can be compiled once and run across different kernel
+  versions.
+
+This document will delve into the above concepts in detail, providing a deeper
+understanding of the capabilities and advantages of libbpf and how it can help
+you develop BPF applications efficiently.
+
+BPF App Lifecycle and libbpf APIs
+==================================
+
+A BPF application consists of one or more BPF programs (either cooperating or
+completely independent), BPF maps, and global variables. The global
+variables are shared between all BPF programs, which allows them to cooperate on
+a common set of data. libbpf provides APIs that user space programs can use to
+manipulate the BPF programs by triggering different phases of a BPF application
+lifecycle.
+
+The following section provides a brief overview of each phase in the BPF life
+cycle:
+
+* **Open phase**: In this phase, libbpf parses the BPF
+  object file and discovers BPF maps, BPF programs, and global variables. After
+  a BPF app is opened, user space apps can make additional adjustments
+  (setting BPF program types, if necessary; pre-setting initial values for
+  global variables, etc.) before all the entities are created and loaded.
+
+* **Load phase**: In the load phase, libbpf creates BPF
+  maps, resolves various relocations, and verifies and loads BPF programs into
+  the kernel. At this point, libbpf validates all the parts of a BPF application
+  and loads the BPF program into the kernel, but no BPF program has yet been
+  executed. After the load phase, it’s possible to set up the initial BPF map
+  state without racing with the BPF program code execution.
+
+* **Attachment phase**: In this phase, libbpf
+  attaches BPF programs to various BPF hook points (e.g., tracepoints, kprobes,
+  cgroup hooks, network packet processing pipeline, etc.). During this
+  phase, BPF programs perform useful work such as processing
+  packets, or updating BPF maps and global variables that can be read from user
+  space.
+
+* **Tear down phase**: In the tear down phase,
+  libbpf detaches BPF programs and unloads them from the kernel. BPF maps are
+  destroyed, and all the resources used by the BPF app are freed.
+
+BPF Object Skeleton File
+========================
+
+BPF skeleton is an alternative interface to libbpf APIs for working with BPF
+objects. Skeleton code abstract away generic libbpf APIs to significantly
+simplify code for manipulating BPF programs from user space. Skeleton code
+includes a bytecode representation of the BPF object file, simplifying the
+process of distributing your BPF code. With BPF bytecode embedded, there are no
+extra files to deploy along with your application binary.
+
+You can generate the skeleton header file ``(.skel.h)`` for a specific object
+file by passing the BPF object to the bpftool. The generated BPF skeleton
+provides the following custom functions that correspond to the BPF lifecycle,
+each of them prefixed with the specific object name:
+
+* ``<name>__open()`` – creates and opens BPF application (``<name>`` stands for
+  the specific bpf object name)
+* ``<name>__load()`` – instantiates, loads,and verifies BPF application parts
+* ``<name>__attach()`` – attaches all auto-attachable BPF programs (it’s
+  optional, you can have more control by using libbpf APIs directly)
+* ``<name>__destroy()`` – detaches all BPF programs and
+  frees up all used resources
+
+Using the skeleton code is the recommended way to work with bpf programs. Keep
+in mind, BPF skeleton provides access to the underlying BPF object, so whatever
+was possible to do with generic libbpf APIs is still possible even when the BPF
+skeleton is used. It's an additive convenience feature, with no syscalls, and no
+cumbersome code.
+
+Other Advantages of Using Skeleton File
+---------------------------------------
+
+* BPF skeleton provides an interface for user space programs to work with BPF
+  global variables. The skeleton code memory maps global variables as a struct
+  into user space. The struct interface allows user space programs to initialize
+  BPF programs before the BPF load phase and fetch and update data from user
+  space afterward.
+
+* The ``skel.h`` file reflects the object file structure by listing out the
+  available maps, programs, etc. BPF skeleton provides direct access to all the
+  BPF maps and BPF programs as struct fields. This eliminates the need for
+  string-based lookups with ``bpf_object_find_map_by_name()`` and
+  ``bpf_object_find_program_by_name()`` APIs, reducing errors due to BPF source
+  code and user-space code getting out of sync.
+
+* The embedded bytecode representation of the object file ensures that the
+  skeleton and the BPF object file are always in sync.
+
+BPF Helpers
+===========
+
+libbpf provides BPF-side APIs that BPF programs can use to interact with the
+system. The BPF helpers definition allows developers to use them in BPF code as
+any other plain C function. For example, there are helper functions to print
+debugging messages, get the time since the system was booted, interact with BPF
+maps, manipulate network packets, etc.
+
+For a complete description of what the helpers do, the arguments they take, and
+the return value, see the `bpf-helpers
+<https://man7.org/linux/man-pages/man7/bpf-helpers.7.html>`_ man page.
+
+BPF CO-RE (Compile Once – Run Everywhere)
+=========================================
+
+BPF programs work in the kernel space and have access to kernel memory and data
+structures. One limitation that BPF applications come across is the lack of
+portability across different kernel versions and configurations. `BCC
+<https://github.com/iovisor/bcc/>`_ is one of the solutions for BPF
+portability. However, it comes with runtime overhead and a large binary size
+from embedding the compiler with the application.
+
+libbpf steps up the BPF program portability by supporting the BPF CO-RE concept.
+BPF CO-RE brings together BTF type information, libbpf, and the compiler to
+produce a single executable binary that you can run on multiple kernel versions
+and configurations.
+
+To make BPF programs portable libbpf relies on the BTF type information of the
+running kernel. Kernel also exposes this self-describing authoritative BTF
+information through ``sysfs`` at ``/sys/kernel/btf/vmlinux``.
+
+You can generate the BTF information for the running kernel with the following
+command:
+
+::
+
+  $ bpftool btf dump file /sys/kernel/btf/vmlinux format c > vmlinux.h
+
+The command generates a ``vmlinux.h`` header file with all kernel types
+(:doc:`BTF types <../btf>`) that the running kernel uses. Including
+``vmlinux.h`` in your BPF program eliminates dependency on system-wide kernel
+headers.
+
+libbpf enables portability of BPF programs by looking at the BPF program’s
+recorded BTF type and relocation information and matching them to BTF
+information (vmlinux) provided by the running kernel. libbpf then resolves and
+matches all the types and fields, and updates necessary offsets and other
+relocatable data to ensure that BPF program’s logic functions correctly for a
+specific kernel on the host. BPF CO-RE concept thus eliminates overhead
+associated with BPF development and allows developers to write portable BPF
+applications without modifications and runtime source code compilation on the
+target machine.
+
+The following code snippet shows how to read the parent field of a kernel
+``task_struct`` using BPF CO-RE and libbf. The basic helper to read a field in a
+CO-RE relocatable manner is ``bpf_core_read(dst, sz, src)``, which will read
+``sz`` bytes from the field referenced by ``src`` into the memory pointed to by
+``dst``.
+
+.. code-block:: C
+   :emphasize-lines: 6
+
+    //...
+    struct task_struct *task = (void *)bpf_get_current_task();
+    struct task_struct *parent_task;
+    int err;
+
+    err = bpf_core_read(&parent_task, sizeof(void *), &task->parent);
+    if (err) {
+      /* handle error */
+    }
+
+    /* parent_task contains the value of task->parent pointer */
+
+In the code snippet, we first get a pointer to the current ``task_struct`` using
+``bpf_get_current_task()``.  We then use ``bpf_core_read()`` to read the parent
+field of task struct into the ``parent_task`` variable. ``bpf_core_read()`` is
+just like ``bpf_probe_read_kernel()`` BPF helper, except it records information
+about the field that should be relocated on the target kernel. i.e, if the
+``parent`` field gets shifted to a different offset within
+``struct task_struct`` due to some new field added in front of it, libbpf will
+automatically adjust the actual offset to the proper value.
+
+Getting Started with libbpf
+===========================
+
+Check out the `libbpf-bootstrap <https://github.com/libbpf/libbpf-bootstrap>`_
+repository with simple examples of using libbpf to build various BPF
+applications.
+
+See also `libbpf API documentation
+<https://libbpf.readthedocs.io/en/latest/api.html>`_.
+
+libbpf and Rust
+===============
+
+If you are building BPF applications in Rust, it is recommended to use the
+`Libbpf-rs <https://github.com/libbpf/libbpf-rs>`_ library instead of bindgen
+bindings directly to libbpf. Libbpf-rs wraps libbpf functionality in
+Rust-idiomatic interfaces and provides libbpf-cargo plugin to handle BPF code
+compilation and skeleton generation. Using Libbpf-rs will make building user
+space part of the BPF application easier. Note that the BPF program themselves
+must still be written in plain C.
+
+Additional Documentation
+========================
+
+* `Program types and ELF Sections <https://libbpf.readthedocs.io/en/latest/program_types.html>`_
+* `API naming convention <https://libbpf.readthedocs.io/en/latest/libbpf_naming_convention.html>`_
+* `Building libbpf <https://libbpf.readthedocs.io/en/latest/libbpf_build.html>`_
+* `API documentation Convention <https://libbpf.readthedocs.io/en/latest/libbpf_naming_convention.html#api-documentation-convention>`_
diff --git a/Documentation/bpf/linux-notes.rst b/Documentation/bpf/linux-notes.rst
index 956b0c86699d..508d009d3bed 100644
--- a/Documentation/bpf/linux-notes.rst
+++ b/Documentation/bpf/linux-notes.rst
@@ -12,6 +12,36 @@ Byte swap instructions
 
 ``BPF_FROM_LE`` and ``BPF_FROM_BE`` exist as aliases for ``BPF_TO_LE`` and ``BPF_TO_BE`` respectively.
 
+Jump instructions
+=================
+
+``BPF_CALL | BPF_X | BPF_JMP`` (0x8d), where the helper function
+integer would be read from a specified register, is not currently supported
+by the verifier.  Any programs with this instruction will fail to load
+until such support is added.
+
+Maps
+====
+
+Linux only supports the 'map_val(map)' operation on array maps with a single element.
+
+Linux uses an fd_array to store maps associated with a BPF program. Thus,
+map_by_idx(imm) uses the fd at that index in the array.
+
+Variables
+=========
+
+The following 64-bit immediate instruction specifies that a variable address,
+which corresponds to some integer stored in the 'imm' field, should be loaded:
+
+=========================  ======  ===  =========================================  ===========  ==============
+opcode construction        opcode  src  pseudocode                                 imm type     dst type
+=========================  ======  ===  =========================================  ===========  ==============
+BPF_IMM | BPF_DW | BPF_LD  0x18    0x3  dst = var_addr(imm)                        variable id  data pointer
+=========================  ======  ===  =========================================  ===========  ==============
+
+On Linux, this integer is a BTF ID.
+
 Legacy BPF Packet access instructions
 =====================================