This patch is to make libbpf able to handle the following extern
kernel function declaration and do the needed relocations before
loading the bpf program to the kernel.
extern int foo(struct sock *) __attribute__((section(".ksyms")))
In the collect extern phase, needed changes is made to
bpf_object__collect_externs() and find_extern_btf_id() to collect
extern function in ".ksyms" section. The func in the BTF datasec also
needs to be replaced by an int var. The idea is similar to the existing
handling in extern var. In case the BTF may not have a var, a dummy ksym
var is added at the beginning of bpf_object__collect_externs()
if there is func under ksyms datasec. It will also change the
func linkage from extern to global which the kernel can support.
It also assigns a param name if it does not have one.
In the collect relo phase, it will record the kernel function
call as RELO_EXTERN_FUNC.
bpf_object__resolve_ksym_func_btf_id() is added to find the func
btf_id of the running kernel.
During actual relocation, it will patch the BPF_CALL instruction with
src_reg = BPF_PSEUDO_FUNC_CALL and insn->imm set to the running
kernel func's btf_id.
The required LLVM patch: https://reviews.llvm.org/D93563
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210325015234.1548923-1-kafai@fb.com
This patch records the extern sym relocs first before recording
subprog relocs. The later patch will have relocs for extern
kernel function call which is also using BPF_JMP | BPF_CALL.
It will be easier to handle the extern symbols first in
the later patch.
is_call_insn() helper is added. The existing is_ldimm64() helper
is renamed to is_ldimm64_insn() for consistency.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210325015227.1548623-1-kafai@fb.com
This patch refactors most of the logic from
bpf_object__resolve_ksyms_btf_id() into a new function
bpf_object__resolve_ksym_var_btf_id().
It is to get ready for a later patch adding
bpf_object__resolve_ksym_func_btf_id() which resolves
a kernel function to the running kernel btf_id.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210325015207.1546749-1-kafai@fb.com
This patch adds support to BPF verifier to allow bpf program calling
kernel function directly.
The use case included in this set is to allow bpf-tcp-cc to directly
call some tcp-cc helper functions (e.g. "tcp_cong_avoid_ai()"). Those
functions have already been used by some kernel tcp-cc implementations.
This set will also allow the bpf-tcp-cc program to directly call the
kernel tcp-cc implementation, For example, a bpf_dctcp may only want to
implement its own dctcp_cwnd_event() and reuse other dctcp_*() directly
from the kernel tcp_dctcp.c instead of reimplementing (or
copy-and-pasting) them.
The tcp-cc kernel functions mentioned above will be white listed
for the struct_ops bpf-tcp-cc programs to use in a later patch.
The white listed functions are not bounded to a fixed ABI contract.
Those functions have already been used by the existing kernel tcp-cc.
If any of them has changed, both in-tree and out-of-tree kernel tcp-cc
implementations have to be changed. The same goes for the struct_ops
bpf-tcp-cc programs which have to be adjusted accordingly.
This patch is to make the required changes in the bpf verifier.
First change is in btf.c, it adds a case in "btf_check_func_arg_match()".
When the passed in "btf->kernel_btf == true", it means matching the
verifier regs' states with a kernel function. This will handle the
PTR_TO_BTF_ID reg. It also maps PTR_TO_SOCK_COMMON, PTR_TO_SOCKET,
and PTR_TO_TCP_SOCK to its kernel's btf_id.
In the later libbpf patch, the insn calling a kernel function will
look like:
insn->code == (BPF_JMP | BPF_CALL)
insn->src_reg == BPF_PSEUDO_KFUNC_CALL /* <- new in this patch */
insn->imm == func_btf_id /* btf_id of the running kernel */
[ For the future calling function-in-kernel-module support, an array
of module btf_fds can be passed at the load time and insn->off
can be used to index into this array. ]
At the early stage of verifier, the verifier will collect all kernel
function calls into "struct bpf_kfunc_desc". Those
descriptors are stored in "prog->aux->kfunc_tab" and will
be available to the JIT. Since this "add" operation is similar
to the current "add_subprog()" and looking for the same insn->code,
they are done together in the new "add_subprog_and_kfunc()".
In the "do_check()" stage, the new "check_kfunc_call()" is added
to verify the kernel function call instruction:
1. Ensure the kernel function can be used by a particular BPF_PROG_TYPE.
A new bpf_verifier_ops "check_kfunc_call" is added to do that.
The bpf-tcp-cc struct_ops program will implement this function in
a later patch.
2. Call "btf_check_kfunc_args_match()" to ensure the regs can be
used as the args of a kernel function.
3. Mark the regs' type, subreg_def, and zext_dst.
At the later do_misc_fixups() stage, the new fixup_kfunc_call()
will replace the insn->imm with the function address (relative
to __bpf_call_base). If needed, the jit can find the btf_func_model
by calling the new bpf_jit_find_kfunc_model(prog, insn).
With the imm set to the function address, "bpftool prog dump xlated"
will be able to display the kernel function calls the same way as
it displays other bpf helper calls.
gpl_compatible program is required to call kernel function.
This feature currently requires JIT.
The verifier selftests are adjusted because of the changes in
the verbose log in add_subprog_and_kfunc().
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210325015142.1544736-1-kafai@fb.com
Ensure that BPF static linker preserves all DATASEC BTF types, even if some of
them might not have any variable information at all. This may happen if the
compiler promotes local initialized variable contents into .rodata section and
there are no global or static functions in the program.
For example,
$ cat t.c
struct t { char a; char b; char c; };
void bar(struct t*);
void find() {
struct t tmp = {1, 2, 3};
bar(&tmp);
}
$ clang -target bpf -O2 -g -S t.c
.long 104 # BTF_KIND_DATASEC(id = 8)
.long 251658240 # 0xf000000
.long 0
.ascii ".rodata" # string offset=104
$ clang -target bpf -O2 -g -c t.c
$ readelf -S t.o | grep data
[ 4] .rodata PROGBITS 0000000000000000 00000090
Fixes: 8fd27bf69b86 ("libbpf: Add BPF static linker BTF and BTF.ext support")
Reported-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210326043036.3081011-1-andrii@kernel.org
Update links to point to blog posts that have some new updates and are
generally kept more up-to-date.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
libbpf_util.h was removed in 7e8bbe24cb8b ("libbpf: xsk: Move barriers from
libbpf_util.h to xsk.h") upstream, so remove it from the list of installable
headers.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Similar to
https://lore.kernel.org/bpf/20210313210920.1959628-2-andrii@kernel.org/
When DECLARE_LIBBPF_OPTS is used with inline field initialization, e.g:
DECLARE_LIBBPF_OPTS(btf_dump_emit_type_decl_opts, opts,
.field_name = var_ident,
.indent_level = 2,
.strip_mods = strip_mods,
);
and compiled in debug mode, the compiler generates code which
leaves the padding uninitialized and triggers errors within libbpf APIs
which require strict zero initialization of OPTS structs.
Adding anonymous padding field fixes the issue.
Fixes: 9f81654eebe8 ("libbpf: Expose BTF-to-C type declaration emitting API")
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: KP Singh <kpsingh@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210319192117.2310658-1-kpsingh@kernel.org
Add .BTF and .BTF.ext static linking logic.
When multiple BPF object files are linked together, their respective .BTF and
.BTF.ext sections are merged together. BTF types are not just concatenated,
but also deduplicated. .BTF.ext data is grouped by type (func info, line info,
core_relos) and target section names, and then all the records are
concatenated together, preserving their relative order. All the BTF type ID
references and string offsets are updated as necessary, to take into account
possibly deduplicated strings and types.
BTF DATASEC types are handled specially. Their respective var_secinfos are
accumulated separately in special per-section data and then final DATASEC
types are emitted at the very end during bpf_linker__finalize() operation,
just before emitting final ELF output file.
BTF data can also provide "section annotations" for some extern variables.
Such concept is missing in ELF, but BTF will have DATASEC types for such
special extern datasections (e.g., .kconfig, .ksyms). Such sections are called
"ephemeral" internally. Internally linker will keep metadata for each such
section, collecting variables information, but those sections won't be emitted
into the final ELF file.
Also, given LLVM/Clang during compilation emits BTF DATASECS that are
incomplete, missing section size and variable offsets for static variables,
BPF static linker will initially fix up such DATASECs, using ELF symbols data.
The final DATASECs will preserve section sizes and all variable offsets. This
is handled correctly by libbpf already, so won't cause any new issues. On the
other hand, it's actually a nice property to have a complete BTF data without
runtime adjustments done during bpf_object__open() by libbpf. In that sense,
BPF static linker is also a BTF normalizer.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210318194036.3521577-8-andrii@kernel.org
Introduce BPF static linker APIs to libbpf. BPF static linker allows to
perform static linking of multiple BPF object files into a single combined
resulting object file, preserving all the BPF programs, maps, global
variables, etc.
Data sections (.bss, .data, .rodata, .maps, maps, etc) with the same name are
concatenated together. Similarly, code sections are also concatenated. All the
symbols and ELF relocations are also concatenated in their respective ELF
sections and are adjusted accordingly to the new object file layout.
Static variables and functions are handled correctly as well, adjusting BPF
instructions offsets to reflect new variable/function offset within the
combined ELF section. Such relocations are referencing STT_SECTION symbols and
that stays intact.
Data sections in different files can have different alignment requirements, so
that is taken care of as well, adjusting sizes and offsets as necessary to
satisfy both old and new alignment requirements.
DWARF data sections are stripped out, currently. As well as LLLVM_ADDRSIG
section, which is ignored by libbpf in bpf_object__open() anyways. So, in
a way, BPF static linker is an analogue to `llvm-strip -g`, which is a pretty
nice property, especially if resulting .o file is then used to generate BPF
skeleton.
Original string sections are ignored and instead we construct our own set of
unique strings using libbpf-internal `struct strset` API.
To reduce the size of the patch, all the .BTF and .BTF.ext processing was
moved into a separate patch.
The high-level API consists of just 4 functions:
- bpf_linker__new() creates an instance of BPF static linker. It accepts
output filename and (currently empty) options struct;
- bpf_linker__add_file() takes input filename and appends it to the already
processed ELF data; it can be called multiple times, one for each BPF
ELF object file that needs to be linked in;
- bpf_linker__finalize() needs to be called to dump final ELF contents into
the output file, specified when bpf_linker was created; after
bpf_linker__finalize() is called, no more bpf_linker__add_file() and
bpf_linker__finalize() calls are allowed, they will return error;
- regardless of whether bpf_linker__finalize() was called or not,
bpf_linker__free() will free up all the used resources.
Currently, BPF static linker doesn't resolve cross-object file references
(extern variables and/or functions). This will be added in the follow up patch
set.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210318194036.3521577-7-andrii@kernel.org
Add btf__add_type() API that performs shallow copy of a given BTF type from
the source BTF into the destination BTF. All the information and type IDs are
preserved, but all the strings encountered are added into the destination BTF
and corresponding offsets are rewritten. BTF type IDs are assumed to be
correct or such that will be (somehow) modified afterwards.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210318194036.3521577-6-andrii@kernel.org
Extract BTF logic for maintaining a set of strings data structure, used for
BTF strings section construction in writable mode, into separate re-usable
API. This data structure is going to be used by bpf_linker to maintains ELF
STRTAB section, which has the same layout as BTF strings section.
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/20210318194036.3521577-5-andrii@kernel.org
Extract and generalize the logic to iterate BTF type ID and string offset
fields within BTF types and .BTF.ext data. Expose this internally in libbpf
for re-use by bpf_linker.
Additionally, complete strings deduplication handling for BTF.ext (e.g., CO-RE
access strings), which was previously missing. There previously was no
case of deduplicating .BTF.ext data, but bpf_linker is going to use it.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210318194036.3521577-3-andrii@kernel.org
Given that vmlinux.h is not compatible with headers like stddef.h, NULL poses
an annoying problem: it is defined as #define, so is not captured in BTF, so
is not emitted into vmlinux.h. This leads to users either sticking to explicit
0, or defining their own NULL (as progs/skb_pkt_end.c does).
But it's easy for bpf_helpers.h to provide (conditionally) NULL definition.
Similarly, KERNEL_VERSION is another commonly missed macro that came up
multiple times. So this patch adds both of them, along with offsetof(), that
also is typically defined in stddef.h, just like NULL.
This might cause compilation warning for existing BPF applications defining
their own NULL and/or KERNEL_VERSION already:
progs/skb_pkt_end.c:7:9: warning: 'NULL' macro redefined [-Wmacro-redefined]
#define NULL 0
^
/tmp/linux/tools/testing/selftests/bpf/tools/include/vmlinux.h:4:9: note: previous definition is here
#define NULL ((void *)0)
^
It is trivial to fix, though, so long-term benefits outweight temporary
inconveniences.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20210317200510.1354627-2-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Adding such anonymous padding fixes the issue with uninitialized portions of
bpf_xdp_set_link_opts when using LIBBPF_DECLARE_OPTS macro with inline field
initialization:
DECLARE_LIBBPF_OPTS(bpf_xdp_set_link_opts, opts, .old_fd = -1);
When such code is compiled in debug mode, compiler is generating code that
leaves padding bytes uninitialized, which triggers error inside libbpf APIs
that do strict zero initialization checks for OPTS structs.
Adding anonymous padding field fixes the issue.
Fixes: bd5ca3ef93cd ("libbpf: Add function to set link XDP fd while specifying old program")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210313210920.1959628-2-andrii@kernel.org
Linux headers might pull 'linux/stddef.h' which defines
'__always_inline' as the following:
#ifndef __always_inline
#define __always_inline inline
#endif
This becomes an issue if the program picks up the 'linux/stddef.h'
definition as the macro now just hints inline to clang.
This change now enforces the proper definition for BPF programs
regardless of the include order.
Signed-off-by: Pedro Tammela <pctammela@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210314173839.457768-1-pctammela@gmail.com
In commit 291471dd1559 ("libbpf, xsk: Add libbpf_smp_store_release
libbpf_smp_load_acquire") linux/compiler.h was added as a dependency
to xsk.h, which is the user-facing API. This makes it harder for
userspace application to consume the library. Here the header
inclusion is removed, and instead {READ,WRITE}_ONCE() is added
explicitly.
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210310080929.641212-2-bjorn.topel@gmail.com
The vmlinux.h generated from BTF is invalid when building
drivers/phy/ti/phy-gmii-sel.c with clang:
vmlinux.h:61702:27: error: array type has incomplete element type ‘struct reg_field’
61702 | const struct reg_field (*regfields)[3];
| ^~~~~~~~~
bpftool generates a forward declaration for this struct regfield, which
compilers aren't happy about. Here's a simplified reproducer:
struct inner {
int val;
};
struct outer {
struct inner (*ptr_to_array)[2];
} A;
After build with clang -> bpftool btf dump c -> clang/gcc:
./def-clang.h:11:23: error: array has incomplete element type 'struct inner'
struct inner (*ptr_to_array)[2];
Member ptr_to_array of struct outer is a pointer to an array of struct
inner. In the DWARF generated by clang, struct outer appears before
struct inner, so when converting BTF of struct outer into C, bpftool
issues a forward declaration to struct inner. With GCC the DWARF info is
reversed so struct inner gets fully defined.
That forward declaration is not sufficient when compilers handle an
array of the struct, even when it's only used through a pointer. Note
that we can trigger the same issue with an intermediate typedef:
struct inner {
int val;
};
typedef struct inner inner2_t[2];
struct outer {
inner2_t *ptr_to_array;
} A;
Becomes:
struct inner;
typedef struct inner inner2_t[2];
And causes:
./def-clang.h:10:30: error: array has incomplete element type 'struct inner'
typedef struct inner inner2_t[2];
To fix this, clear through_ptr whenever we encounter an intermediate
array, to make the inner struct part of a strong link and force full
declaration.
Fixes: 351131b51c7a ("libbpf: add btf_dump API for BTF-to-C conversion")
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210319112554.794552-2-jean-philippe@linaro.org
Allow to pass sk_lookup programs to PROG_TEST_RUN. User space
provides the full bpf_sk_lookup struct as context. Since the
context includes a socket pointer that can't be exposed
to user space we define that PROG_TEST_RUN returns the cookie
of the selected socket or zero in place of the socket pointer.
We don't support testing programs that select a reuseport socket,
since this would mean running another (unrelated) BPF program
from the sk_lookup test handler.
Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210303101816.36774-3-lmb@cloudflare.com
xsk_lookup_bpf_maps, based on prog_fd, looks whether current prog has a
reference to XSKMAP. BPF prog can include insns that work on various BPF
maps and this is covered by iterating through map_ids.
The bpf_map_info that is passed to bpf_obj_get_info_by_fd for filling
needs to be cleared at each iteration, so that it doesn't contain any
outdated fields and that is currently missing in the function of
interest.
To fix that, zero-init map_info via memset before each
bpf_obj_get_info_by_fd call.
Also, since the area of this code is touched, in general strcmp is
considered harmful, so let's convert it to strncmp and provide the
size of the array name for current map_info.
While at it, do s/continue/break/ once we have found the xsks_map to
terminate the search.
Fixes: 5750902a6e9b ("libbpf: proper XSKMAP cleanup")
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Björn Töpel <bjorn.topel@intel.com>
Link: https://lore.kernel.org/bpf/20210303185636.18070-4-maciej.fijalkowski@intel.com
The logic follows that of BTF_KIND_INT most of the time. Sanitization
replaces BTF_KIND_FLOATs with equally-sized empty BTF_KIND_STRUCTs on
older kernels, for example, the following:
[4] FLOAT 'float' size=4
becomes the following:
[4] STRUCT '(anon)' size=4 vlen=0
With dwarves patch [1] and this patch, the older kernels, which were
failing with the floating-point-related errors, will now start working
correctly.
[1] https://github.com/iii-i/dwarves/commit/btf-kind-float-v2
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210226202256.116518-4-iii@linux.ibm.com
Syncing latest libbpf commits from kernel repository.
Baseline bpf-next commit: 86ce322d21eb032ed8fdd294d0fb095d2debb430
Checkpoint bpf-next commit: 303dcc25b5c782547eb13b9f29426de843dd6f34
Baseline bpf commit: 78031381ae9c88f4f914d66154f4745122149c58
Checkpoint bpf commit: 6185266c5a853bb0f2a459e3ff594546f277609b
Alexei Starovoitov (1):
bpf: Count the number of times recursion was prevented
Florent Revest (2):
bpf: Be less specific about socket cookies guarantees
bpf: Expose bpf_get_socket_cookie to tracing programs
Hangbin Liu (1):
bpf: Remove blank line in bpf helper description comment
Jesper Dangaard Brouer (2):
bpf: bpf_fib_lookup return MTU value as output when looked up
bpf: Add BPF-helper for MTU checking
Jonas Bonn (1):
Revert "GTP: add support for flow based tunneling API"
Martin KaFai Lau (1):
libbpf: Ignore non function pointer member in struct_ops
Stanislav Fomichev (1):
libbpf: Use AF_LOCAL instead of AF_INET in xsk.c
Yonghong Song (3):
bpf: Add bpf_for_each_map_elem() helper
libbpf: Move function is_ldimm64() earlier in libbpf.c
libbpf: Support subprog address relocation
include/uapi/linux/bpf.h | 140 +++++++++++++++++++++++++++++++++--
include/uapi/linux/if_link.h | 1 -
src/libbpf.c | 98 +++++++++++++++++++-----
src/xsk.c | 2 +-
4 files changed, 213 insertions(+), 28 deletions(-)
--
2.24.1
A new relocation RELO_SUBPROG_ADDR is added to capture
subprog addresses loaded with ld_imm64 insns. Such ld_imm64
insns are marked with BPF_PSEUDO_FUNC and will be passed to
kernel. For bpf_for_each_map_elem() case, kernel will
check that the to-be-used subprog address must be a static
function and replace it with proper actual jited func address.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210226204930.3885367-1-yhs@fb.com
