LLVM automatically places __arena variables into ".arena.1" ELF section.
In order to use such global variables bpf program must include definition
of arena map in ".maps" section, like:
struct {
__uint(type, BPF_MAP_TYPE_ARENA);
__uint(map_flags, BPF_F_MMAPABLE);
__uint(max_entries, 1000); /* number of pages */
__ulong(map_extra, 2ull << 44); /* start of mmap() region */
} arena SEC(".maps");
libbpf recognizes both uses of arena and creates single `struct bpf_map *`
instance in libbpf APIs.
".arena.1" ELF section data is used as initial data image, which is exposed
through skeleton and bpf_map__initial_value() to the user, if they need to tune
it before the load phase. During load phase, this initial image is copied over
into mmap()'ed region corresponding to arena, and discarded.
Few small checks here and there had to be added to make sure this
approach works with bpf_map__initial_value(), mostly due to hard-coded
assumption that map->mmaped is set up with mmap() syscall and should be
munmap()'ed. For arena, .arena.1 can be (much) smaller than maximum
arena size, so this smaller data size has to be tracked separately.
Given it is enforced that there is only one arena for entire bpf_object
instance, we just keep it in a separate field. This can be generalized
if necessary later.
All global variables from ".arena.1" section are accessible from user space
via skel->arena->name_of_var.
For bss/data/rodata the skeleton/libbpf perform the following sequence:
1. addr = mmap(MAP_ANONYMOUS)
2. user space optionally modifies global vars
3. map_fd = bpf_create_map()
4. bpf_update_map_elem(map_fd, addr) // to store values into the kernel
5. mmap(addr, MAP_FIXED, map_fd)
after step 5 user spaces see the values it wrote at step 2 at the same addresses
arena doesn't support update_map_elem. Hence skeleton/libbpf do:
1. addr = malloc(sizeof SEC ".arena.1")
2. user space optionally modifies global vars
3. map_fd = bpf_create_map(MAP_TYPE_ARENA)
4. real_addr = mmap(map->map_extra, MAP_SHARED | MAP_FIXED, map_fd)
5. memcpy(real_addr, addr) // this will fault-in and allocate pages
At the end look and feel of global data vs __arena global data is the same from
bpf prog pov.
Another complication is:
struct {
__uint(type, BPF_MAP_TYPE_ARENA);
} arena SEC(".maps");
int __arena foo;
int bar;
ptr1 = &foo; // relocation against ".arena.1" section
ptr2 = &arena; // relocation against ".maps" section
ptr3 = &bar; // relocation against ".bss" section
Fo the kernel ptr1 and ptr2 has point to the same arena's map_fd
while ptr3 points to a different global array's map_fd.
For the verifier:
ptr1->type == unknown_scalar
ptr2->type == const_ptr_to_map
ptr3->type == ptr_to_map_value
After verification, from JIT pov all 3 ptr-s are normal ld_imm64 insns.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/bpf/20240308010812.89848-11-alexei.starovoitov@gmail.com
To allow external admin authority to override default BPF FS location
(/sys/fs/bpf) for implicit BPF token creation, teach libbpf to recognize
LIBBPF_BPF_TOKEN_PATH envvar. If it is specified and user application
didn't explicitly specify bpf_token_path option, it will be treated
exactly like bpf_token_path option, overriding default /sys/fs/bpf
location and making BPF token mandatory.
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20240124022127.2379740-29-andrii@kernel.org
Add BPF token support to BPF object-level functionality.
BPF token is supported by BPF object logic either as an explicitly
provided BPF token from outside (through BPF FS path), or implicitly
(unless prevented through bpf_object_open_opts).
Implicit mode is assumed to be the most common one for user namespaced
unprivileged workloads. The assumption is that privileged container
manager sets up default BPF FS mount point at /sys/fs/bpf with BPF token
delegation options (delegate_{cmds,maps,progs,attachs} mount options).
BPF object during loading will attempt to create BPF token from
/sys/fs/bpf location, and pass it for all relevant operations
(currently, map creation, BTF load, and program load).
In this implicit mode, if BPF token creation fails due to whatever
reason (BPF FS is not mounted, or kernel doesn't support BPF token,
etc), this is not considered an error. BPF object loading sequence will
proceed with no BPF token.
In explicit BPF token mode, user provides explicitly custom BPF FS mount
point path. In such case, BPF object will attempt to create BPF token
from provided BPF FS location. If BPF token creation fails, that is
considered a critical error and BPF object load fails with an error.
Libbpf provides a way to disable implicit BPF token creation, if it
causes any troubles (BPF token is designed to be completely optional and
shouldn't cause any problems even if provided, but in the world of BPF
LSM, custom security logic can be installed that might change outcome
depending on the presence of BPF token). To disable libbpf's default BPF
token creation behavior user should provide either invalid BPF token FD
(negative), or empty bpf_token_path option.
BPF token presence can influence libbpf's feature probing, so if BPF
object has associated BPF token, feature probing is instructed to use
BPF object-specific feature detection cache and token FD.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20240124022127.2379740-26-andrii@kernel.org
To allow external admin authority to override default BPF FS location
(/sys/fs/bpf) for implicit BPF token creation, teach libbpf to recognize
LIBBPF_BPF_TOKEN_PATH envvar. If it is specified and user application
didn't explicitly specify neither bpf_token_path nor bpf_token_fd
option, it will be treated exactly like bpf_token_path option,
overriding default /sys/fs/bpf location and making BPF token mandatory.
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20231213190842.3844987-10-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Add BPF token support to BPF object-level functionality.
BPF token is supported by BPF object logic either as an explicitly
provided BPF token from outside (through BPF FS path or explicit BPF
token FD), or implicitly (unless prevented through
bpf_object_open_opts).
Implicit mode is assumed to be the most common one for user namespaced
unprivileged workloads. The assumption is that privileged container
manager sets up default BPF FS mount point at /sys/fs/bpf with BPF token
delegation options (delegate_{cmds,maps,progs,attachs} mount options).
BPF object during loading will attempt to create BPF token from
/sys/fs/bpf location, and pass it for all relevant operations
(currently, map creation, BTF load, and program load).
In this implicit mode, if BPF token creation fails due to whatever
reason (BPF FS is not mounted, or kernel doesn't support BPF token,
etc), this is not considered an error. BPF object loading sequence will
proceed with no BPF token.
In explicit BPF token mode, user provides explicitly either custom BPF
FS mount point path or creates BPF token on their own and just passes
token FD directly. In such case, BPF object will either dup() token FD
(to not require caller to hold onto it for entire duration of BPF object
lifetime) or will attempt to create BPF token from provided BPF FS
location. If BPF token creation fails, that is considered a critical
error and BPF object load fails with an error.
Libbpf provides a way to disable implicit BPF token creation, if it
causes any troubles (BPF token is designed to be completely optional and
shouldn't cause any problems even if provided, but in the world of BPF
LSM, custom security logic can be installed that might change outcome
dependin on the presence of BPF token). To disable libbpf's default BPF
token creation behavior user should provide either invalid BPF token FD
(negative), or empty bpf_token_path option.
BPF token presence can influence libbpf's feature probing, so if BPF
object has associated BPF token, feature probing is instructed to use
BPF object-specific feature detection cache and token FD.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20231213190842.3844987-7-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This adds bpf_program__attach_netkit() API to libbpf. Overall it is very
similar to tcx. The API looks as following:
LIBBPF_API struct bpf_link *
bpf_program__attach_netkit(const struct bpf_program *prog, int ifindex,
const struct bpf_netkit_opts *opts);
The struct bpf_netkit_opts is done in similar way as struct bpf_tcx_opts
for supporting bpf_mprog control parameters. The attach location for the
primary and peer device is derived from the program section "netkit/primary"
and "netkit/peer", respectively.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/r/20231024214904.29825-4-daniel@iogearbox.net
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
For bpf_object__pin_programs() there is bpf_object__unpin_programs().
Likewise bpf_object__unpin_maps() for bpf_object__pin_maps().
But no bpf_object__unpin() for bpf_object__pin(). Adding the former adds
symmetry to the API.
It's also convenient for cleanup in application code. It's an API I
would've used if it was available for a repro I was writing earlier.
Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/bpf/b2f9d41da4a350281a0b53a804d11b68327e14e5.1692832478.git.dxu@dxuuu.xyz
Adding bpf_program__attach_uprobe_multi function that
allows to attach multiple uprobes with uprobe_multi link.
The user can specify uprobes with direct arguments:
binary_path/func_pattern/pid
or with struct bpf_uprobe_multi_opts opts argument fields:
const char **syms;
const unsigned long *offsets;
const unsigned long *ref_ctr_offsets;
const __u64 *cookies;
User can specify 2 mutually exclusive set of inputs:
1) use only path/func_pattern/pid arguments
2) use path/pid with allowed combinations of:
syms/offsets/ref_ctr_offsets/cookies/cnt
- syms and offsets are mutually exclusive
- ref_ctr_offsets and cookies are optional
Any other usage results in error.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20230809083440.3209381-15-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Implement tcx BPF link support for libbpf.
The bpf_program__attach_fd() API has been refactored slightly in order to pass
bpf_link_create_opts pointer as input.
A new bpf_program__attach_tcx() has been added on top of this which allows for
passing all relevant data via extensible struct bpf_tcx_opts.
The program sections tcx/ingress and tcx/egress correspond to the hook locations
for tc ingress and egress, respectively.
For concrete usage examples, see the extensive selftests that have been
developed as part of this series.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230719140858.13224-5-daniel@iogearbox.net
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Introduce new netlink attribute NETDEV_A_DEV_XDP_ZC_MAX_SEGS that will
carry maximum fragments that underlying ZC driver is able to handle on
TX side. It is going to be included in netlink response only when driver
supports ZC. Any value higher than 1 implies multi-buffer ZC support on
underlying device.
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Link: https://lore.kernel.org/r/20230719132421.584801-11-maciej.fijalkowski@intel.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This patch updates bpf_map__set_value_size() so that if the given map is
memory mapped, it will attempt to resize the mapped region. Initial
contents of the mapped region are preserved. BTF is not required, but
after the mapping is resized an attempt is made to adjust the associated
BTF information if the following criteria is met:
- BTF info is present
- the map is a datasec
- the final variable in the datasec is an array
... the resulting BTF info will be updated so that the final array
variable is associated with a new BTF array type sized to cover the
requested size.
Note that the initial resizing of the memory mapped region can succeed
while the subsequent BTF adjustment can fail. In this case, BTF info is
dropped from the map by clearing the key and value type.
Signed-off-by: JP Kobryn <inwardvessel@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/bpf/20230524004537.18614-2-inwardvessel@gmail.com
Signed-off-by: Daniel Müller <deso@posteo.net>
By default, libbpf will attach the kprobe/uprobe BPF program in the
latest mode that supported by kernel. In this patch, we add the support
to let users manually attach kprobe/uprobe in legacy or perf mode.
There are 3 mode that supported by the kernel to attach kprobe/uprobe:
LEGACY: create perf event in legacy way and don't use bpf_link
PERF: create perf event with perf_event_open() and don't use bpf_link
Signed-off-by: Menglong Dong <imagedong@tencent.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Biao Jiang <benbjiang@tencent.com>
Link: create perf event with perf_event_open() and use bpf_link
Link: https://lore.kernel.org/bpf/20230113093427.1666466-1-imagedong@tencent.com/
Link: https://lore.kernel.org/bpf/20230306064833.7932-2-imagedong@tencent.com
Users now can manually choose the mode with
bpf_program__attach_uprobe_opts()/bpf_program__attach_kprobe_opts().
Add option to set when the perf buffer should wake up, by default the
perf buffer becomes signaled for every event that is being pushed to it.
In case of a high throughput of events it will be more efficient to wake
up only once you have X events ready to be read.
So your application can wakeup once and drain the entire perf buffer.
Signed-off-by: Jon Doron <jond@wiz.io>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230207081916.3398417-1-arilou@gmail.com
When attach_prog_fd field was removed in libbpf 1.0 and replaced with
`long: 0` placeholder, it actually shifted all the subsequent fields by
8 byte. This is due to `long: 0` promising to adjust next field's offset
to long-aligned offset. But in this case we were already long-aligned
as pin_root_path is a pointer. So `long: 0` had no effect, and thus
didn't feel the gap created by removed attach_prog_fd.
Non-zero bitfield should have been used instead. I validated using
pahole. Originally kconfig field was at offset 40. With `long: 0` it's
at offset 32, which is wrong. With this change it's back at offset 40.
While technically libbpf 1.0 is allowed to break backwards
compatibility and applications should have been recompiled against
libbpf 1.0 headers, but given how trivial it is to preserve memory
layout, let's fix this.
Reported-by: Grant Seltzer Richman <grantseltzer@gmail.com>
Fixes: 146bf811f5ac ("libbpf: remove most other deprecated high-level APIs")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20220923230559.666608-1-andrii@kernel.org
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Now that all of the logic is in place in the kernel to support user-space
produced ring buffers, we can add the user-space logic to libbpf. This
patch therefore adds the following public symbols to libbpf:
struct user_ring_buffer *
user_ring_buffer__new(int map_fd,
const struct user_ring_buffer_opts *opts);
void *user_ring_buffer__reserve(struct user_ring_buffer *rb, __u32 size);
void *user_ring_buffer__reserve_blocking(struct user_ring_buffer *rb,
__u32 size, int timeout_ms);
void user_ring_buffer__submit(struct user_ring_buffer *rb, void *sample);
void user_ring_buffer__discard(struct user_ring_buffer *rb,
void user_ring_buffer__free(struct user_ring_buffer *rb);
A user-space producer must first create a struct user_ring_buffer * object
with user_ring_buffer__new(), and can then reserve samples in the
ring buffer using one of the following two symbols:
void *user_ring_buffer__reserve(struct user_ring_buffer *rb, __u32 size);
void *user_ring_buffer__reserve_blocking(struct user_ring_buffer *rb,
__u32 size, int timeout_ms);
With user_ring_buffer__reserve(), a pointer to a 'size' region of the ring
buffer will be returned if sufficient space is available in the buffer.
user_ring_buffer__reserve_blocking() provides similar semantics, but will
block for up to 'timeout_ms' in epoll_wait if there is insufficient space
in the buffer. This function has the guarantee from the kernel that it will
receive at least one event-notification per invocation to
bpf_ringbuf_drain(), provided that at least one sample is drained, and the
BPF program did not pass the BPF_RB_NO_WAKEUP flag to bpf_ringbuf_drain().
Once a sample is reserved, it must either be committed to the ring buffer
with user_ring_buffer__submit(), or discarded with
user_ring_buffer__discard().
Signed-off-by: David Vernet <void@manifault.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220920000100.477320-4-void@manifault.com
Add SEC("ksyscall")/SEC("ksyscall/<syscall_name>") and corresponding
kretsyscall variants (for return kprobes) to allow users to kprobe
syscall functions in kernel. These special sections allow to ignore
complexities and differences between kernel versions and host
architectures when it comes to syscall wrapper and corresponding
__<arch>_sys_<syscall> vs __se_sys_<syscall> differences, depending on
whether host kernel has CONFIG_ARCH_HAS_SYSCALL_WRAPPER (though libbpf
itself doesn't rely on /proc/config.gz for detecting this, see
BPF_KSYSCALL patch for how it's done internally).
Combined with the use of BPF_KSYSCALL() macro, this allows to just
specify intended syscall name and expected input arguments and leave
dealing with all the variations to libbpf.
In addition to SEC("ksyscall+") and SEC("kretsyscall+") add
bpf_program__attach_ksyscall() API which allows to specify syscall name
at runtime and provide associated BPF cookie value.
At the moment SEC("ksyscall") and bpf_program__attach_ksyscall() do not
handle all the calling convention quirks for mmap(), clone() and compat
syscalls. It also only attaches to "native" syscall interfaces. If host
system supports compat syscalls or defines 32-bit syscalls in 64-bit
kernel, such syscall interfaces won't be attached to by libbpf.
These limitations may or may not change in the future. Therefore it is
recommended to use SEC("kprobe") for these syscalls or if working with
compat and 32-bit interfaces is required.
Tested-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20220714070755.3235561-5-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Add support for writing a custom event reader, by exposing the ring
buffer.
With the new API perf_buffer__buffer() you will get access to the
raw mmaped()'ed per-cpu underlying memory of the ring buffer.
This region contains both the perf buffer data and header
(struct perf_event_mmap_page), which manages the ring buffer
state (head/tail positions, when accessing the head/tail position
it's important to take into consideration SMP).
With this type of low level access one can implement different types of
consumers here are few simple examples where this API helps with:
1. perf_event_read_simple is allocating using malloc, perhaps you want
to handle the wrap-around in some other way.
2. Since perf buf is per-cpu then the order of the events is not
guarnteed, for example:
Given 3 events where each event has a timestamp t0 < t1 < t2,
and the events are spread on more than 1 CPU, then we can end
up with the following state in the ring buf:
CPU[0] => [t0, t2]
CPU[1] => [t1]
When you consume the events from CPU[0], you could know there is
a t1 missing, (assuming there are no drops, and your event data
contains a sequential index).
So now one can simply do the following, for CPU[0], you can store
the address of t0 and t2 in an array (without moving the tail, so
there data is not perished) then move on the CPU[1] and set the
address of t1 in the same array.
So you end up with something like:
void **arr[] = [&t0, &t1, &t2], now you can consume it orderely
and move the tails as you process in order.
3. Assuming there are multiple CPUs and we want to start draining the
messages from them, then we can "pick" with which one to start with
according to the remaining free space in the ring buffer.
Signed-off-by: Jon Doron <jond@wiz.io>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220715181122.149224-1-arilou@gmail.com
Remove support for legacy features and behaviors that previously had to
be disabled by calling libbpf_set_strict_mode():
- legacy BPF map definitions are not supported now;
- RLIMIT_MEMLOCK auto-setting, if necessary, is always on (but see
libbpf_set_memlock_rlim());
- program name is used for program pinning (instead of section name);
- cleaned up error returning logic;
- entry BPF programs should have SEC() always.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20220627211527.2245459-15-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Remove a bunch of high-level bpf_object/bpf_map/bpf_program related
APIs. All the APIs related to private per-object/map/prog state,
program preprocessing callback, and generally everything multi-instance
related is removed in a separate patch.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20220627211527.2245459-9-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Add high-level API wrappers for most common and typical BPF map
operations that works directly on instances of struct bpf_map * (so
you don't have to call bpf_map__fd()) and validate key/value size
expectations.
These helpers require users to specify key (and value, where
appropriate) sizes when performing lookup/update/delete/etc. This forces
user to actually think and validate (for themselves) those. This is
a good thing as user is expected by kernel to implicitly provide correct
key/value buffer sizes and kernel will just read/write necessary amount
of data. If it so happens that user doesn't set up buffers correctly
(which bit people for per-CPU maps especially) kernel either randomly
overwrites stack data or return -EFAULT, depending on user's luck and
circumstances. These high-level APIs are meant to prevent such
unpleasant and hard to debug bugs.
This patch also adds bpf_map_delete_elem_flags() low-level API and
requires passing flags to bpf_map__delete_elem() API for consistency
across all similar APIs, even though currently kernel doesn't expect
any extra flags for BPF_MAP_DELETE_ELEM operation.
List of map operations that get these high-level APIs:
- bpf_map_lookup_elem;
- bpf_map_update_elem;
- bpf_map_delete_elem;
- bpf_map_lookup_and_delete_elem;
- bpf_map_get_next_key.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220512220713.2617964-1-andrii@kernel.org
Adding bpf_program__set_insns that allows to set new instructions
for a BPF program.
This is a very advanced libbpf API and users need to know what
they are doing. This should be used from prog_prepare_load_fn
callback only.
We can have changed instructions after calling prog_prepare_load_fn
callback, reloading them.
One of the users of this new API will be perf's internal BPF prologue
generation.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220510074659.2557731-2-jolsa@kernel.org
Add bpf_map__set_autocreate() API that allows user to opt-out from
libbpf automatically creating BPF map during BPF object load.
This is a useful feature when building CO-RE-enabled BPF application
that takes advantage of some new-ish BPF map type (e.g., socket-local
storage) if kernel supports it, but otherwise uses some alternative way
(e.g., extra HASH map). In such case, being able to disable the creation
of a map that kernel doesn't support allows to successfully create and
load BPF object file with all its other maps and programs.
It's still up to user to make sure that no "live" code in any of their BPF
programs are referencing such map instance, which can be achieved by
guarding such code with CO-RE relocation check or by using .rodata
global variables.
If user fails to properly guard such code to turn it into "dead code",
libbpf will helpfully post-process BPF verifier log and will provide
more meaningful error and map name that needs to be guarded properly. As
such, instead of:
; value = bpf_map_lookup_elem(&missing_map, &zero);
4: (85) call unknown#2001000000
invalid func unknown#2001000000
... user will see:
; value = bpf_map_lookup_elem(&missing_map, &zero);
4: <invalid BPF map reference>
BPF map 'missing_map' is referenced but wasn't created
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220428041523.4089853-4-andrii@kernel.org
