Add support for new kinds to libbpf. BTF_KIND_LOC_PARAM and
BTF_KIND_LOC_PROTO are dedup-able so add support for their
deduplication, whereas since BTF_KIND_LOCSEC contains a unique
offset it is not. LOC_PARAM is considered a primary type
since it contains no external references; LOC_PROTO is a
reference type consisting of LOC_PARAM references so they
are handled in the primary and reference dedup phases
respectively.
For BTF field iteration, BTF_KIND_LOCSEC needs 2 m_offs[] values
for the associated KIND_FUNC and KIND_LOC_PROTO type ids in
each LOCSEC entry.
Add APIs to add location param, location prototypes and location
sections and btf_is_* tests, data accessors for each.
For BTF distillation we add location info to split BTF.
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://patch.msgid.link/20260924111428.75957-3-alan.maguire@oracle.com
Add BTF_KIND_LOC_PARAM, BTF_KIND_LOC_PROTO and BTF_KIND_LOCSEC
to help represent location information for functions.
BTF_KIND_LOC_PARAM is used to represent how we retrieve data at a
location; either via register(s), or register+offset, a dereference
of a register+offset or a constant value.
BTF_KIND_LOC_PROTO represents location information about a location
with multiple BTF_KIND_LOC_PARAMs.
And finally BTF_KIND_LOCSEC is a set of location sites, each
of which has
- a BTF_KIND_FUNC function associated with the inline site
- a location prototype specifying where to find the function
parameters
- an address offset relative to the kernel base address
This can be used to support representing
- a fully-inlined function at potentially multiple inline sites
with potentially different parameter availability
- a partially-inlined function where some _LOC_PROTOs represent
inlined sites as above and others have normal _FUNC representations
Also BTF_KIND_LOCSEC struct btf_loc will have two type id
references; one for the associated func, the other for the loc_proto.
Accordingly increase the number of m_offs references in btf_field_desc
to 2.
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://patch.msgid.link/20260924111428.75957-2-alan.maguire@oracle.com
BTF maximum vlen is encoded using 16 bits with a maximum vlen
of 65535. This has sufficed for structs, function parameters
and enumerated type values. However, with upcoming BTF location
information - in particular information about inline sites -
this limit is surpassed. Use bits 16-23 - currently unused in
BTF info - to extend to 24 bits, giving a max vlen of (2^24 - 1),
or 16 million.
Also extend BTF kind encoding from 5 to 7 bits, giving a maximum
available number of kinds of 128. Since with the BTF location work
we use another 3 kinds, we are fast approaching the current limit
of 32.
Convert BTF_MAX_* values to enums to allow them to be encoded in
kernel BTF; this will allow us to detect if the running kernel
supports a 24-bit vlen or not. Add one for max _possible_
(not used) kind.
Fix up a few places in the kernel where a 16-bit vlen is assumed;
remove BTF_INFO_MASK as now all bits are used.
The vlen expansion was suggested by Andrii in [1]; the kind expansion
is tackled here too as it may be needed also to support new kinds
in BTF.
[1] https://lore.kernel.org/bpf/CAEf4BzZx=X6vGqcA8SPU6D+v6k+TR=ZewebXMuXtpmML058piw@mail.gmail.com/
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Acked-by: Mykyta Yatsenko <yatsenko@meta.com>
Link: https://lore.kernel.org/r/20260417143023.1551481-2-alan.maguire@oracle.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Allow bpf object feat_cache assignment in BPF selftests
to simulate missing features via inclusion of libbpf_internal.h
and use of bpf_object_set_feat_cache() and bpf_object__sanitize_btf() to
test BTF sanitization for cases where missing features are simulated.
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Link: https://lore.kernel.org/r/20260408165735.843763-2-alan.maguire@oracle.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Add a FEAT_BTF_LAYOUT feature check which checks if the
kernel supports BTF layout information. Also sanitize
BTF if it contains layout data but the kernel does not
support it. The sanitization requires rewriting raw
BTF data to update the header and eliminate the layout
section (since it lies between the types and strings),
so refactor sanitization to do the raw BTF retrieval
and creation of updated BTF, returning that new BTF
on success.
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20260326145444.2076244-7-alan.maguire@oracle.com
Support encoding of BTF layout data via btf__new_empty_opts().
Current supported opts are base_btf and add_layout.
Layout information is maintained in btf.c in the layouts[] array;
when BTF is created with the add_layout option it represents the
current view of supported BTF kinds.
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20260326145444.2076244-5-alan.maguire@oracle.com
Support reading in layout fixing endian issues on reading;
also support writing layout section to raw BTF object.
There is not yet an API to populate the layout with meaningful
information.
As part of this, we need to consider multiple valid BTF header
sizes; the original or the layout-extended headers.
So to support this, the "struct btf" representation is modified
to contain a "struct btf_header" and we copy the valid
portion from the raw data to it; this means we can always safely
check fields like btf->hdr.layout_len .
Note if parsed-in BTF has extra header information beyond
sizeof(struct btf_header) - if so we make that BTF ineligible
for modification by setting btf->has_hdr_extra .
Ensure that we handle endianness issues for BTF layout section,
though currently only field that needs this (flags) is unused.
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20260326145444.2076244-3-alan.maguire@oracle.com
We have seen a number of issues like [1]; failures to deduplicate
key kernel data structures like task_struct. These are often hard
to debug from pahole even with verbose output, especially when
identity/equivalence checks fail deep in a nested struct comparison.
Here we add debug messages of the form
libbpf: STRUCT 'task_struct' size=2560 vlen=194 cand_id[54222] canon_id[102820] shallow-equal but not equiv for field#23 'sched_class': 0
These will be emitted during dedup from pahole when --verbose/-V
is specified. This greatly helps identify exactly where dedup
failures are experienced.
[1] https://lore.kernel.org/bpf/b8e8b560-bce5-414b-846d-0da6d22a9983@oracle.com/
Changes since v1:
- updated debug messages to refer to shallow-equal, added ids (Andrii)
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20251203191507.55565-1-alan.maguire@oracle.com
When creating multi-split BTF we correctly set the start string offset
to be the size of the base string section plus the base BTF start
string offset; the latter is needed for multi-split BTF since the
offset is non-zero there.
Unfortunately the BTF parsing case needed that logic and it was
missed.
Fixes: 4e29128a9ace ("libbpf/btf: Fix string handling to support multi-split BTF")
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20251104203309.318429-2-alan.maguire@oracle.com
libbpf handling of split BTF has been written largely with the
assumption that multiple splits are possible, i.e. split BTF on top of
split BTF on top of base BTF. One area where this does not quite work
is string handling in split BTF; the start string offset should be the
base BTF string section length + the base BTF string offset. This
worked in the past because for a single split BTF with base the start
string offset was always 0.
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20250519165935.261614-2-alan.maguire@oracle.com
Recently as a side-effect of
commit ac053946f5c4 ("compiler.h: introduce TYPEOF_UNQUAL() macro")
issues were observed in deduplication between modules and kernel BTF
such that a large number of kernel types were not deduplicated so
were found in module BTF (task_struct, bpf_prog etc). The root cause
appeared to be a failure to dedup struct types, specifically those
with members that were pointers with __percpu annotations.
The issue in dedup is at the point that we are deduplicating structures,
we have not yet deduplicated reference types like pointers. If multiple
copies of a pointer point at the same (deduplicated) integer as in this
case, we do not see them as identical. Special handling already exists
to deal with structures and arrays, so add pointer handling here too.
Reported-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20250429161042.2069678-1-alan.maguire@oracle.com
Currently the only opportunity to set sock ops flags dictating
which callbacks fire for a socket is from within a TCP-BPF sockops
program. This is problematic if the connection is already set up
as there is no further chance to specify callbacks for that socket.
Add TCP_BPF_SOCK_OPS_CB_FLAGS to bpf_setsockopt() and bpf_getsockopt()
to allow users to specify callbacks later, either via an iterator
over sockets or via a socket-specific program triggered by a
setsockopt() on the socket.
Previous discussion on this here [1].
[1] https://lore.kernel.org/bpf/f42f157b-6e52-dd4d-3d97-9b86c84c0b00@oracle.com/
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Link: https://lore.kernel.org/r/20240808150558.1035626-2-alan.maguire@oracle.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
When building with clang for ARCH=i386, the following errors are
observed:
CC kernel/bpf/btf_relocate.o
./tools/lib/bpf/btf_relocate.c:206:23: error: implicit truncation from 'int' to a one-bit wide bit-field changes value from 1 to -1 [-Werror,-Wsingle-bit-bitfield-constant-conversion]
206 | info[id].needs_size = true;
| ^ ~
./tools/lib/bpf/btf_relocate.c:256:25: error: implicit truncation from 'int' to a one-bit wide bit-field changes value from 1 to -1 [-Werror,-Wsingle-bit-bitfield-constant-conversion]
256 | base_info.needs_size = true;
| ^ ~
2 errors generated.
The problem is we use 1-bit, 31-bit bitfields in a signed int.
Changing to
bool needs_size: 1;
unsigned int size:31;
...resolves the error and pahole reports that 4 bytes are used
for the underlying representation:
$ pahole btf_name_info tools/lib/bpf/btf_relocate.o
struct btf_name_info {
const char * name; /* 0 8 */
unsigned int needs_size:1; /* 8: 0 4 */
unsigned int size:31; /* 8: 1 4 */
__u32 id; /* 12 4 */
/* size: 16, cachelines: 1, members: 4 */
/* last cacheline: 16 bytes */
};
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240624192903.854261-1-alan.maguire@oracle.com
Share relocation implementation with the kernel. As part of this,
we also need the type/string iteration functions so also share
btf_iter.c file. Relocation code in kernel and userspace is identical
save for the impementation of the reparenting of split BTF to the
relocated base BTF and retrieval of the BTF header from "struct btf";
these small functions need separate user-space and kernel implementations
for the separate "struct btf"s they operate upon.
One other wrinkle on the kernel side is we have to map .BTF.ids in
modules as they were generated with the type ids used at BTF encoding
time. btf_relocate() optionally returns an array mapping from old BTF
ids to relocated ids, so we use that to fix up these references where
needed for kfuncs.
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/bpf/20240620091733.1967885-5-alan.maguire@oracle.com
Map distilled base BTF type ids referenced in split BTF and their
references to the base BTF passed in, and if the mapping succeeds,
reparent the split BTF to the base BTF.
Relocation is done by first verifying that distilled base BTF
only consists of named INT, FLOAT, ENUM, FWD, STRUCT and
UNION kinds; then we sort these to speed lookups. Once sorted,
the base BTF is iterated, and for each relevant kind we check
for an equivalent in distilled base BTF. When found, the
mapping from distilled -> base BTF id and string offset is recorded.
In establishing mappings, we need to ensure we check STRUCT/UNION
size when the STRUCT/UNION is embedded in a split BTF STRUCT/UNION,
and when duplicate names exist for the same STRUCT/UNION. Otherwise
size is ignored in matching STRUCT/UNIONs.
Once all mappings are established, we can update type ids
and string offsets in split BTF and reparent it to the new base.
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/bpf/20240613095014.357981-4-alan.maguire@oracle.com
To support more robust split BTF, adding supplemental context for the
base BTF type ids that split BTF refers to is required. Without such
references, a simple shuffling of base BTF type ids (without any other
significant change) invalidates the split BTF. Here the attempt is made
to store additional context to make split BTF more robust.
This context comes in the form of distilled base BTF providing minimal
information (name and - in some cases - size) for base INTs, FLOATs,
STRUCTs, UNIONs, ENUMs and ENUM64s along with modified split BTF that
points at that base and contains any additional types needed (such as
TYPEDEF, PTR and anonymous STRUCT/UNION declarations). This
information constitutes the minimal BTF representation needed to
disambiguate or remove split BTF references to base BTF. The rules
are as follows:
- INT, FLOAT, FWD are recorded in full.
- if a named base BTF STRUCT or UNION is referred to from split BTF, it
will be encoded as a zero-member sized STRUCT/UNION (preserving
size for later relocation checks). Only base BTF STRUCT/UNIONs
that are either embedded in split BTF STRUCT/UNIONs or that have
multiple STRUCT/UNION instances of the same name will _need_ size
checks at relocation time, but as it is possible a different set of
types will be duplicates in the later to-be-resolved base BTF,
we preserve size information for all named STRUCT/UNIONs.
- if an ENUM[64] is named, a ENUM forward representation (an ENUM
with no values) of the same size is used.
- in all other cases, the type is added to the new split BTF.
Avoiding struct/union/enum/enum64 expansion is important to keep the
distilled base BTF representation to a minimum size.
When successful, new representations of the distilled base BTF and new
split BTF that refers to it are returned. Both need to be freed by the
caller.
So to take a simple example, with split BTF with a type referring
to "struct sk_buff", we will generate distilled base BTF with a
0-member STRUCT sk_buff of the appropriate size, and the split BTF
will refer to it instead.
Tools like pahole can utilize such split BTF to populate the .BTF
section (split BTF) and an additional .BTF.base section. Then
when the split BTF is loaded, the distilled base BTF can be used
to relocate split BTF to reference the current (and possibly changed)
base BTF.
So for example if "struct sk_buff" was id 502 when the split BTF was
originally generated, we can use the distilled base BTF to see that
id 502 refers to a "struct sk_buff" and replace instances of id 502
with the current (relocated) base BTF sk_buff type id.
Distilled base BTF is small; when building a kernel with all modules
using distilled base BTF as a test, overall module size grew by only
5.3Mb total across ~2700 modules.
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/bpf/20240613095014.357981-2-alan.maguire@oracle.com
Seeing the following:
Warning: Kernel ABI header at 'tools/include/uapi/linux/bpf.h' differs from latest version at 'include/uapi/linux/bpf.h'
...so sync tools version missing some list_node/rb_tree fields.
Fixes: c3c510ce431c ("bpf: Add 'owner' field to bpf_{list,rb}_node")
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Link: https://lore.kernel.org/r/20230719162257.20818-1-alan.maguire@oracle.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
When examining module BTF, it is common to see core kernel structures
such as sk_buff, net_device duplicated in the module. After adding
debug messaging to BTF it turned out that much of the problem
was down to the identical struct test failing during deduplication;
sometimes the compiler adds identical structs. However
it turns out sometimes that type ids of identical struct members
can also differ, even when the containing structs are still identical.
To take an example, for struct sk_buff, debug messaging revealed
that the identical struct matching was failing for the anon
struct "headers"; specifically for the first field:
__u8 __pkt_type_offset[0]; /* 128 0 */
Looking at the code in BTF deduplication, we have code that guards
against the possibility of identical struct definitions, down to
type ids, and identical array definitions. However in this case
we have a struct which is being defined twice but does not have
identical type ids since each duplicate struct has separate type
ids for the above array member. A similar problem (though not
observed) could occur for struct-in-struct.
The solution is to make the "identical struct" test check members
not just for matching ids, but to also check if they in turn are
identical structs or arrays.
The results of doing this are quite dramatic (for some modules
at least); I see the number of type ids drop from around 10000
to just over 1000 in one module for example.
For testing use latest pahole or apply [1], otherwise dedups
can fail for the reasons described there.
Also fix return type of btf_dedup_identical_arrays() as
suggested by Andrii to match boolean return type used
elsewhere.
Fixes: efdd3eb8015e ("libbpf: Accommodate DWARF/compiler bug with duplicated structs")
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/1666622309-22289-1-git-send-email-alan.maguire@oracle.com
[1] https://lore.kernel.org/bpf/1666364523-9648-1-git-send-email-alan.maguire
Parsing of USDT arguments is architecture-specific. On aarch64 it is
relatively easy since registers used are x[0-31] and sp. Format is
slightly different compared to x86_64. Possible forms are:
- "size@[reg[,offset]]" for dereferences, e.g. "-8@[sp,76]" and "-4@[sp]";
- "size@reg" for register values, e.g. "-4@x0";
- "size@value" for raw values, e.g. "-8@1".
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/1649690496-1902-2-git-send-email-alan.maguire@oracle.com
In the process of doing path resolution for uprobe attach, libraries are
identified by matching a ".so" substring in the binary_path.
This matches a lot of patterns that do not conform to library.so[.version]
format, so instead match a ".so" _suffix_, and if that fails match a
".so." substring for the versioned library case.
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/1649245431-29956-2-git-send-email-alan.maguire@oracle.com
Now that u[ret]probes can use name-based specification, it makes
sense to add support for auto-attach based on SEC() definition.
The format proposed is
SEC("u[ret]probe/binary:[raw_offset|[function_name[+offset]]")
For example, to trace malloc() in libc:
SEC("uprobe/libc.so.6:malloc")
...or to trace function foo2 in /usr/bin/foo:
SEC("uprobe//usr/bin/foo:foo2")
Auto-attach is done for all tasks (pid -1). prog can be an absolute
path or simply a program/library name; in the latter case, we use
PATH/LD_LIBRARY_PATH to resolve the full path, falling back to
standard locations (/usr/bin:/usr/sbin or /usr/lib64:/usr/lib) if
the file is not found via environment-variable specified locations.
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/1648654000-21758-4-git-send-email-alan.maguire@oracle.com
kprobe attach is name-based, using lookups of kallsyms to translate
a function name to an address. Currently uprobe attach is done
via an offset value as described in [1]. Extend uprobe opts
for attach to include a function name which can then be converted
into a uprobe-friendly offset. The calcualation is done in
several steps:
1. First, determine the symbol address using libelf; this gives us
the offset as reported by objdump
2. If the function is a shared library function - and the binary
provided is a shared library - no further work is required;
the address found is the required address
3. Finally, if the function is local, subtract the base address
associated with the object, retrieved from ELF program headers.
The resultant value is then added to the func_offset value passed
in to specify the uprobe attach address. So specifying a func_offset
of 0 along with a function name "printf" will attach to printf entry.
The modes of operation supported are then
1. to attach to a local function in a binary; function "foo1" in
"/usr/bin/foo"
2. to attach to a shared library function in a shared library -
function "malloc" in libc.
[1] https://www.kernel.org/doc/html/latest/trace/uprobetracer.html
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/1648654000-21758-3-git-send-email-alan.maguire@oracle.com
bpf_program__attach_uprobe_opts() requires a binary_path argument
specifying binary to instrument. Supporting simply specifying
"libc.so.6" or "foo" should be possible too.
Library search checks LD_LIBRARY_PATH, then /usr/lib64, /usr/lib.
This allows users to run BPF programs prefixed with
LD_LIBRARY_PATH=/path2/lib while still searching standard locations.
Similarly for non .so files, we check PATH and /usr/bin, /usr/sbin.
Path determination will be useful for auto-attach of BPF uprobe programs
using SEC() definition.
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/1648654000-21758-2-git-send-email-alan.maguire@oracle.com
When compiling libbpf with gcc 4.8.5, we see:
CC staticobjs/btf_dump.o
btf_dump.c: In function ‘btf_dump_dump_type_data.isra.24’:
btf_dump.c:2296:5: error: ‘err’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
if (err < 0)
^
cc1: all warnings being treated as errors
make: *** [staticobjs/btf_dump.o] Error 1
While gcc 4.8.5 is too old to build the upstream kernel, it's possible it
could be used to build standalone libbpf which suffers from the same problem.
Silence the error by initializing 'err' to 0. The warning/error seems to be
a false positive since err is set early in the function. Regardless we
shouldn't prevent libbpf from building for this.
Fixes: 920d16af9b42 ("libbpf: BTF dumper support for typed data")
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/1638180040-8037-1-git-send-email-alan.maguire@oracle.com
When retrieving the enum value associated with typed data during
"is data zero?" checking in btf_dump_type_data_check_zero(), the
return value of btf_dump_get_enum_value() is not passed to the caller
if the function returns a non-zero (error) value. Currently, 0
is returned if the function returns an error. We should instead
propagate the error to the caller.
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/1626770993-11073-4-git-send-email-alan.maguire@oracle.com
__int128 is not supported for some 32-bit platforms (arm and i386).
__int128 was used in carrying out computations on bitfields which
aid display, but the same calculations could be done with __u64
with the small effect of not supporting 128-bit bitfields.
With these changes, a big-endian issue with casting 128-bit integers
to 64-bit for enum bitfields is solved also, as we now use 64-bit
integers for bitfield calculations.
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/1626770993-11073-2-git-send-email-alan.maguire@oracle.com
__s64 can be defined as either long or long long, depending on the
architecture. On ppc64le it's defined as long, giving this error:
In file included from btf_dump.c:22:
btf_dump.c: In function 'btf_dump_type_data_check_overflow':
libbpf_internal.h:111:22: error: format '%lld' expects argument of
type 'long long int', but argument 3 has type '__s64' {aka 'long int'}
[-Werror=format=]
111 | libbpf_print(level, "libbpf: " fmt, ##__VA_ARGS__); \
| ^~~~~~~~~~
libbpf_internal.h:114:27: note: in expansion of macro '__pr'
114 | #define pr_warn(fmt, ...) __pr(LIBBPF_WARN, fmt, ##__VA_ARGS__)
| ^~~~
btf_dump.c:1992:3: note: in expansion of macro 'pr_warn'
1992 | pr_warn("unexpected size [%lld] for id [%u]\n",
| ^~~~~~~
btf_dump.c:1992:32: note: format string is defined here
1992 | pr_warn("unexpected size [%lld] for id [%u]\n",
| ~~~^
| |
| long long int
| %ld
Cast to size_t and use %zu instead.
Reported-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/1626475617-25984-3-git-send-email-alan.maguire@oracle.com
If data is packed, data structures can store it outside of usual
boundaries. For example a 4-byte int can be stored on a unaligned
boundary in a case like this:
struct s {
char f1;
int f2;
} __attribute((packed));
...the int is stored at an offset of one byte. Some platforms have
problems dereferencing data that is not aligned with its size, and
code exists to handle most cases of this for BTF typed data display.
However pointer display was missed, and a simple function to test if
"ptr_is_aligned(data, data_sz)" would help clarify this code.
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/1626475617-25984-2-git-send-email-alan.maguire@oracle.com
Add a BTF dumper for typed data, so that the user can dump a typed
version of the data provided.
The API is
int btf_dump__dump_type_data(struct btf_dump *d, __u32 id,
void *data, size_t data_sz,
const struct btf_dump_type_data_opts *opts);
...where the id is the BTF id of the data pointed to by the "void *"
argument; for example the BTF id of "struct sk_buff" for a
"struct skb *" data pointer. Options supported are
- a starting indent level (indent_lvl)
- a user-specified indent string which will be printed once per
indent level; if NULL, tab is chosen but any string <= 32 chars
can be provided.
- a set of boolean options to control dump display, similar to those
used for BPF helper bpf_snprintf_btf(). Options are
- compact : omit newlines and other indentation
- skip_names: omit member names
- emit_zeroes: show zero-value members
Default output format is identical to that dumped by bpf_snprintf_btf(),
for example a "struct sk_buff" representation would look like this:
struct sk_buff){
(union){
(struct){
.next = (struct sk_buff *)0xffffffffffffffff,
.prev = (struct sk_buff *)0xffffffffffffffff,
(union){
.dev = (struct net_device *)0xffffffffffffffff,
.dev_scratch = (long unsigned int)18446744073709551615,
},
},
...
If the data structure is larger than the *data_sz*
number of bytes that are available in *data*, as much
of the data as possible will be dumped and -E2BIG will
be returned. This is useful as tracers will sometimes
not be able to capture all of the data associated with
a type; for example a "struct task_struct" is ~16k.
Being able to specify that only a subset is available is
important for such cases. On success, the amount of data
dumped is returned.
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/1626362126-27775-2-git-send-email-alan.maguire@oracle.com
kprobes can be placed on most instructions in a function, not
just entry, and ftrace and bpftrace support the function+offset
notification for probe placement. Adding parsing of func_name
into func+offset to bpf_program__attach_kprobe() allows the
user to specify
SEC("kprobe/bpf_fentry_test5+0x6")
...for example, and the offset can be passed to perf_event_open_probe()
to support kprobe attachment.
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210714094400.396467-8-jolsa@kernel.org
When operating on split BTF, btf__find_by_name[_kind] will not
iterate over all types since they use btf->nr_types to show
the number of types to iterate over. For split BTF this is
the number of types _on top of base BTF_, so it will
underestimate the number of types to iterate over, especially
for vmlinux + module BTF, where the latter is much smaller.
Use btf__get_nr_types() instead.
Fixes: ba451366bf44 ("libbpf: Implement basic split BTF support")
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/1605437195-2175-1-git-send-email-alan.maguire@oracle.com
A helper is added to allow seq file writing of kernel data
structures using vmlinux BTF. Its signature is
long bpf_seq_printf_btf(struct seq_file *m, struct btf_ptr *ptr,
u32 btf_ptr_size, u64 flags);
Flags and struct btf_ptr definitions/use are identical to the
bpf_snprintf_btf helper, and the helper returns 0 on success
or a negative error value.
Suggested-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/1601292670-1616-8-git-send-email-alan.maguire@oracle.com
A helper is added to support tracing kernel type information in BPF
using the BPF Type Format (BTF). Its signature is
long bpf_snprintf_btf(char *str, u32 str_size, struct btf_ptr *ptr,
u32 btf_ptr_size, u64 flags);
struct btf_ptr * specifies
- a pointer to the data to be traced
- the BTF id of the type of data pointed to
- a flags field is provided for future use; these flags
are not to be confused with the BTF_F_* flags
below that control how the btf_ptr is displayed; the
flags member of the struct btf_ptr may be used to
disambiguate types in kernel versus module BTF, etc;
the main distinction is the flags relate to the type
and information needed in identifying it; not how it
is displayed.
For example a BPF program with a struct sk_buff *skb
could do the following:
static struct btf_ptr b = { };
b.ptr = skb;
b.type_id = __builtin_btf_type_id(struct sk_buff, 1);
bpf_snprintf_btf(str, sizeof(str), &b, sizeof(b), 0, 0);
Default output looks like this:
(struct sk_buff){
.transport_header = (__u16)65535,
.mac_header = (__u16)65535,
.end = (sk_buff_data_t)192,
.head = (unsigned char *)0x000000007524fd8b,
.data = (unsigned char *)0x000000007524fd8b,
.truesize = (unsigned int)768,
.users = (refcount_t){
.refs = (atomic_t){
.counter = (int)1,
},
},
}
Flags modifying display are as follows:
- BTF_F_COMPACT: no formatting around type information
- BTF_F_NONAME: no struct/union member names/types
- BTF_F_PTR_RAW: show raw (unobfuscated) pointer values;
equivalent to %px.
- BTF_F_ZERO: show zero-valued struct/union members;
they are not displayed by default
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/1601292670-1616-4-git-send-email-alan.maguire@oracle.com
Sync include/uapi/linux/bpf.h with tools/ equivalent to add
BPF_F_ADJ_ROOM_ENCAP_L2(len) macro.
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Alan Maguire