- 19 Jun, 2019 10 commits
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Alexei Starovoitov authored
Introduce precision tracking logic that helps cilium programs the most: old clang old clang new clang new clang with all patches with all patches bpf_lb-DLB_L3.o 1838 2283 1923 1863 bpf_lb-DLB_L4.o 3218 2657 3077 2468 bpf_lb-DUNKNOWN.o 1064 545 1062 544 bpf_lxc-DDROP_ALL.o 26935 23045 166729 22629 bpf_lxc-DUNKNOWN.o 34439 35240 174607 28805 bpf_netdev.o 9721 8753 8407 6801 bpf_overlay.o 6184 7901 5420 4754 bpf_lxc_jit.o 39389 50925 39389 50925 Consider code: 654: (85) call bpf_get_hash_recalc#34 655: (bf) r7 = r0 656: (15) if r8 == 0x0 goto pc+29 657: (bf) r2 = r10 658: (07) r2 += -48 659: (18) r1 = 0xffff8881e41e1b00 661: (85) call bpf_map_lookup_elem#1 662: (15) if r0 == 0x0 goto pc+23 663: (69) r1 = *(u16 *)(r0 +0) 664: (15) if r1 == 0x0 goto pc+21 665: (bf) r8 = r7 666: (57) r8 &= 65535 667: (bf) r2 = r8 668: (3f) r2 /= r1 669: (2f) r2 *= r1 670: (bf) r1 = r8 671: (1f) r1 -= r2 672: (57) r1 &= 255 673: (25) if r1 > 0x1e goto pc+12 R0=map_value(id=0,off=0,ks=20,vs=64,imm=0) R1_w=inv(id=0,umax_value=30,var_off=(0x0; 0x1f)) 674: (67) r1 <<= 1 675: (0f) r0 += r1 At this point the verifier will notice that scalar R1 is used in map pointer adjustment. R1 has to be precise for later operations on R0 to be validated properly. The verifier will backtrack the above code in the following way: last_idx 675 first_idx 664 regs=2 stack=0 before 675: (0f) r0 += r1 // started backtracking R1 regs=2 is a bitmask regs=2 stack=0 before 674: (67) r1 <<= 1 regs=2 stack=0 before 673: (25) if r1 > 0x1e goto pc+12 regs=2 stack=0 before 672: (57) r1 &= 255 regs=2 stack=0 before 671: (1f) r1 -= r2 // now both R1 and R2 has to be precise -> regs=6 mask regs=6 stack=0 before 670: (bf) r1 = r8 // after this insn R8 and R2 has to be precise regs=104 stack=0 before 669: (2f) r2 *= r1 // after this one R8, R2, and R1 regs=106 stack=0 before 668: (3f) r2 /= r1 regs=106 stack=0 before 667: (bf) r2 = r8 regs=102 stack=0 before 666: (57) r8 &= 65535 regs=102 stack=0 before 665: (bf) r8 = r7 regs=82 stack=0 before 664: (15) if r1 == 0x0 goto pc+21 // this is the end of verifier state. The following regs will be marked precised: R1_rw=invP(id=0,umax_value=65535,var_off=(0x0; 0xffff)) R7_rw=invP(id=0) parent didn't have regs=82 stack=0 marks // so backtracking continues into parent state last_idx 663 first_idx 655 regs=82 stack=0 before 663: (69) r1 = *(u16 *)(r0 +0) // R1 was assigned no need to track it further regs=80 stack=0 before 662: (15) if r0 == 0x0 goto pc+23 // keep tracking R7 regs=80 stack=0 before 661: (85) call bpf_map_lookup_elem#1 // keep tracking R7 regs=80 stack=0 before 659: (18) r1 = 0xffff8881e41e1b00 regs=80 stack=0 before 658: (07) r2 += -48 regs=80 stack=0 before 657: (bf) r2 = r10 regs=80 stack=0 before 656: (15) if r8 == 0x0 goto pc+29 regs=80 stack=0 before 655: (bf) r7 = r0 // here the assignment into R7 // mark R0 to be precise: R0_rw=invP(id=0) parent didn't have regs=1 stack=0 marks // regs=1 -> tracking R0 last_idx 654 first_idx 644 regs=1 stack=0 before 654: (85) call bpf_get_hash_recalc#34 // and in the parent frame it was a return value // nothing further to backtrack Two scalar registers not marked precise are equivalent from state pruning point of view. More details in the patch comments. It doesn't support bpf2bpf calls yet and enabled for root only. Signed-off-by:Alexei Starovoitov <ast@kernel.org> Acked-by:
Andrii Nakryiko <andriin@fb.com> Signed-off-by:
Daniel Borkmann <daniel@iogearbox.net>
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Alexei Starovoitov authored
Add a bunch of loop tests. Most of them are created by replacing '#pragma unroll' with '#pragma clang loop unroll(disable)' Several tests are artificially large: /* partial unroll. llvm will unroll loop ~150 times. * C loop count -> 600. * Asm loop count -> 4. * 16k insns in loop body. * Total of 5 such loops. Total program size ~82k insns. */ "./pyperf600.o", /* no unroll at all. * C loop count -> 600. * ASM loop count -> 600. * ~110 insns in loop body. * Total of 5 such loops. Total program size ~1500 insns. */ "./pyperf600_nounroll.o", /* partial unroll. 19k insn in a loop. * Total program size 20.8k insn. * ~350k processed_insns */ "./strobemeta.o", Signed-off-by:
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Alexei Starovoitov authored
This set of tests is a rewrite of Edward's earlier tests: https://patchwork.ozlabs.org/patch/877221/Signed-off-by:
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Alexei Starovoitov authored
Fix tests that assumed no loops. Signed-off-by:
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Alexei Starovoitov authored
The commit 7640ead9 partially resolved the issue of callees incorrectly pruning the callers. With introduction of bounded loops and jmps_processed heuristic single verifier state may contain multiple branches and calls. It's possible that new verifier state (for future pruning) will be allocated inside callee. Then callee will exit (still within the same verifier state). It will go back to the caller and there R6-R9 registers will be read and will trigger mark_reg_read. But the reg->live for all frames but the top frame is not set to LIVE_NONE. Hence mark_reg_read will fail to propagate liveness into parent and future walking will incorrectly conclude that the states are equivalent because LIVE_READ is not set. In other words the rule for parent/live should be: whenever register parentage chain is set the reg->live should be set to LIVE_NONE. is_state_visited logic already follows this rule for spilled registers. Fixes: 7640ead9 ("bpf: verifier: make sure callees don't prune with caller differences") Fixes: f4d7e40a ("bpf: introduce function calls (verification)") Signed-off-by:
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Alexei Starovoitov authored
Allow the verifier to validate the loops by simulating their execution. Exisiting programs have used '#pragma unroll' to unroll the loops by the compiler. Instead let the verifier simulate all iterations of the loop. In order to do that introduce parentage chain of bpf_verifier_state and 'branches' counter for the number of branches left to explore. See more detailed algorithm description in bpf_verifier.h This algorithm borrows the key idea from Edward Cree approach: https://patchwork.ozlabs.org/patch/877222/ Additional state pruning heuristics make such brute force loop walk practical even for large loops. Signed-off-by:
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Alexei Starovoitov authored
This patch extends is_branch_taken() logic from JMP+K instructions to JMP+X instructions. Conditional branches are often done when src and dst registers contain known scalars. In such case the verifier can follow the branch that is going to be taken when program executes. That speeds up the verification and is essential feature to support bounded loops. Signed-off-by:
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Alexei Starovoitov authored
fix tests that incorrectly assumed that the verifier cannot track constants through stack. Signed-off-by:
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Alexei Starovoitov authored
Compilers often spill induction variables into the stack, hence it is necessary for the verifier to track scalar values of the registers through stack slots. Also few bpf programs were incorrectly rejected in the past, since the verifier was not able to track such constants while they were used to compute offsets into packet headers. Tracking constants through the stack significantly decreases the chances of state pruning, since two different constants are considered to be different by state equivalency. End result that cilium tests suffer serious degradation in the number of states processed and corresponding verification time increase. before after bpf_lb-DLB_L3.o 1838 6441 bpf_lb-DLB_L4.o 3218 5908 bpf_lb-DUNKNOWN.o 1064 1064 bpf_lxc-DDROP_ALL.o 26935 93790 bpf_lxc-DUNKNOWN.o 34439 123886 bpf_netdev.o 9721 31413 bpf_overlay.o 6184 18561 bpf_lxc_jit.o 39389 359445 After further debugging turned out that cillium progs are getting hurt by clang due to the same constant tracking issue. Newer clang generates better code by spilling less to the stack. Instead it keeps more constants in the registers which hurts state pruning since the verifier already tracks constants in the registers: old clang new clang (no spill/fill tracking introduced by this patch) bpf_lb-DLB_L3.o 1838 1923 bpf_lb-DLB_L4.o 3218 3077 bpf_lb-DUNKNOWN.o 1064 1062 bpf_lxc-DDROP_ALL.o 26935 166729 bpf_lxc-DUNKNOWN.o 34439 174607 bpf_netdev.o 9721 8407 bpf_overlay.o 6184 5420 bpf_lcx_jit.o 39389 39389 The final table is depressing: old clang old clang new clang new clang const spill/fill const spill/fill bpf_lb-DLB_L3.o 1838 6441 1923 8128 bpf_lb-DLB_L4.o 3218 5908 3077 6707 bpf_lb-DUNKNOWN.o 1064 1064 1062 1062 bpf_lxc-DDROP_ALL.o 26935 93790 166729 380712 bpf_lxc-DUNKNOWN.o 34439 123886 174607 440652 bpf_netdev.o 9721 31413 8407 31904 bpf_overlay.o 6184 18561 5420 23569 bpf_lxc_jit.o 39389 359445 39389 359445 Tracking constants in the registers hurts state pruning already. Adding tracking of constants through stack hurts pruning even more. The later patch address this general constant tracking issue with coarse/precise logic. Signed-off-by: -
Andrii Nakryiko authored
Add const qualifiers to bpf_object/bpf_program/bpf_map arguments for getter APIs. There is no need for them to not be const pointers. Verified that make -C tools/lib/bpf make -C tools/testing/selftests/bpf make -C tools/perf all build without warnings. Signed-off-by:
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- 17 Jun, 2019 13 commits
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Daniel T. Lee authored
Currently, header inclusion in each file is inconsistent. For example, "libbpf.h" header is included as multiple ways. #include "bpf/libbpf.h" #include "libbpf.h" Due to commit b552d33c ("samples/bpf: fix include path in Makefile"), $(srctree)/tools/lib/bpf/ path had been included during build, path "bpf/" in header isn't necessary anymore. This commit removes path "bpf/" in header inclusion. Signed-off-by:Daniel T. Lee <danieltimlee@gmail.com> Signed-off-by:
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Daniel T. Lee authored
Due to recent change of include path at commit b552d33c ("samples/bpf: fix include path in Makefile"), some of the previous include options became unnecessary. This commit removes duplicated include options in Makefile. Signed-off-by:
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Daniel Borkmann authored
Andrii Nakryiko says: ==================== This patch set implements initial version (as discussed at LSF/MM2019 conference) of a new way to specify BPF maps, relying on BTF type information, which allows for easy extensibility, preserving forward and backward compatibility. See details and examples in description for patch #6. [0] contains an outline of follow up extensions to be added after this basic set of features lands. They are useful by itself, but also allows to bring libbpf to feature-parity with iproute2 BPF loader. That should open a path forward for BPF loaders unification. Patch #1 centralizes commonly used min/max macro in libbpf_internal.h. Patch #2 extracts .BTF and .BTF.ext loading loging from elf_collect(). Patch #3 simplifies elf_collect() error-handling logic. Patch #4 refactors map initialization logic into user-provided maps and global data maps, in preparation to adding another way (BTF-defined maps). Patch #5 adds support for map definitions in multiple ELF sections and deprecates bpf_object__find_map_by_offset() API which doesn't appear to be used anymore and makes assumption that all map definitions reside in single ELF section. Patch #6 splits BTF intialization from sanitization/loading into kernel to preserve original BTF at the time of map initialization. Patch #7 adds support for BTF-defined maps. Patch #8 adds new test for BTF-defined map definition. Patches #9-11 convert test BPF map definitions to use BTF way. [0] https://lore.kernel.org/bpf/CAEf4BzbfdG2ub7gCi0OYqBrUoChVHWsmOntWAkJt47=FE+km+A@mail.gmail.com/ v1->v2: - more BTF-sanity checks in parsing map definitions (Song); - removed confusing usage of "attribute", switched to "field; - split off elf_collect() refactor from btf loading refactor (Song); - split selftests conversion into 3 patches (Stanislav): 1. test already relying on BTF; 2. tests w/ custom types as key/value (so benefiting from BTF); 3. all the rest tests (integers as key/value, special maps w/o BTF support). - smaller code improvements (Song); rfc->v1: - error out on unknown field by default (Stanislav, Jakub, Lorenz); ==================== Signed-off-by:
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Andrii Nakryiko authored
Convert a bulk of selftests that have maps with custom (not integer) key and/or value. Signed-off-by:
Song Liu <songliubraving@fb.com> Signed-off-by:
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Andrii Nakryiko authored
Switch tests that already rely on BTF to BTF-defined map definitions. Signed-off-by:
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Andrii Nakryiko authored
Add file test for BTF-defined map definition. Signed-off-by:
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Andrii Nakryiko authored
This patch adds support for a new way to define BPF maps. It relies on BTF to describe mandatory and optional attributes of a map, as well as captures type information of key and value naturally. This eliminates the need for BPF_ANNOTATE_KV_PAIR hack and ensures key/value sizes are always in sync with the key/value type. Relying on BTF, this approach allows for both forward and backward compatibility w.r.t. extending supported map definition features. By default, any unrecognized attributes are treated as an error, but it's possible relax this using MAPS_RELAX_COMPAT flag. New attributes, added in the future will need to be optional. The outline of the new map definition (short, BTF-defined maps) is as follows: 1. All the maps should be defined in .maps ELF section. It's possible to have both "legacy" map definitions in `maps` sections and BTF-defined maps in .maps sections. Everything will still work transparently. 2. The map declaration and initialization is done through a global/static variable of a struct type with few mandatory and extra optional fields: - type field is mandatory and specified type of BPF map; - key/value fields are mandatory and capture key/value type/size information; - max_entries attribute is optional; if max_entries is not specified or initialized, it has to be provided in runtime through libbpf API before loading bpf_object; - map_flags is optional and if not defined, will be assumed to be 0. 3. Key/value fields should be **a pointer** to a type describing key/value. The pointee type is assumed (and will be recorded as such and used for size determination) to be a type describing key/value of the map. This is done to save excessive amounts of space allocated in corresponding ELF sections for key/value of big size. 4. As some maps disallow having BTF type ID associated with key/value, it's possible to specify key/value size explicitly without associating BTF type ID with it. Use key_size and value_size fields to do that (see example below). Here's an example of simple ARRAY map defintion: struct my_value { int x, y, z; }; struct { int type; int max_entries; int *key; struct my_value *value; } btf_map SEC(".maps") = { .type = BPF_MAP_TYPE_ARRAY, .max_entries = 16, }; This will define BPF ARRAY map 'btf_map' with 16 elements. The key will be of type int and thus key size will be 4 bytes. The value is struct my_value of size 12 bytes. This map can be used from C code exactly the same as with existing maps defined through struct bpf_map_def. Here's an example of STACKMAP definition (which currently disallows BTF type IDs for key/value): struct { __u32 type; __u32 max_entries; __u32 map_flags; __u32 key_size; __u32 value_size; } stackmap SEC(".maps") = { .type = BPF_MAP_TYPE_STACK_TRACE, .max_entries = 128, .map_flags = BPF_F_STACK_BUILD_ID, .key_size = sizeof(__u32), .value_size = PERF_MAX_STACK_DEPTH * sizeof(struct bpf_stack_build_id), }; This approach is naturally extended to support map-in-map, by making a value field to be another struct that describes inner map. This feature is not implemented yet. It's also possible to incrementally add features like pinning with full backwards and forward compatibility. Support for static initialization of BPF_MAP_TYPE_PROG_ARRAY using pointers to BPF programs is also on the roadmap. Signed-off-by: -
Andrii Nakryiko authored
Libbpf does sanitization of BTF before loading it into kernel, if kernel doesn't support some of newer BTF features. This removes some of the important information from BTF (e.g., DATASEC and VAR description), which will be used for map construction. This patch splits BTF processing into initialization step, in which BTF is initialized from ELF and all the original data is still preserved; and sanitization/loading step, which ensures that BTF is safe to load into kernel. This allows to use full BTF information to construct maps, while still loading valid BTF into older kernels. Signed-off-by:
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Andrii Nakryiko authored
To support maps to be defined in multiple sections, it's important to identify map not just by offset within its section, but section index as well. This patch adds tracking of section index. For global data, we record section index of corresponding .data/.bss/.rodata ELF section for uniformity, and thus don't need a special value of offset for those maps. Signed-off-by:
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Andrii Nakryiko authored
User and global data maps initialization has gotten pretty complicated and unnecessarily convoluted. This patch splits out the logic for global data map and user-defined map initialization. It also removes the restriction of pre-calculating how many maps will be initialized, instead allowing to keep adding new maps as they are discovered, which will be used later for BTF-defined map definitions. Signed-off-by:
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Andrii Nakryiko authored
Simplify ELF parsing logic by exiting early, as there is no common clean up path to execute. That makes it unnecessary to track when err was set and when it was cleared. It also reduces nesting in some places. Signed-off-by:
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Andrii Nakryiko authored
As a preparation for adding BTF-based BPF map loading, extract .BTF and .BTF.ext loading logic. Signed-off-by:
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Andrii Nakryiko authored
Multiple files in libbpf redefine their own definitions for min/max. Let's define them in libbpf_internal.h and use those everywhere. Signed-off-by:
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- 14 Jun, 2019 11 commits
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YueHaibing authored
If CONFIG_INET is not set, building fails: kernel/bpf/verifier.o: In function `check_mem_access': verifier.c: undefined reference to `bpf_xdp_sock_is_valid_access' kernel/bpf/verifier.o: In function `convert_ctx_accesses': verifier.c: undefined reference to `bpf_xdp_sock_convert_ctx_access' Reported-by:
Hulk Robot <hulkci@huawei.com> Fixes: fada7fdc ("bpf: Allow bpf_map_lookup_elem() on an xskmap") Signed-off-by:
YueHaibing <yuehaibing@huawei.com> Acked-by:
Jonathan Lemon <jonathan.lemon@gmail.com> Signed-off-by:
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Stanislav Fomichev authored
This lets us test that both BPF_PROG_TYPE_CGROUP_SOCK_ADDR and BPF_PROG_TYPE_SOCK_OPS can access underlying bpf_sock. Cc: Martin Lau <kafai@fb.com> Signed-off-by:
Stanislav Fomichev <sdf@google.com> Signed-off-by:
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Stanislav Fomichev authored
Add sk to struct bpf_sock_addr and struct bpf_sock_ops. Cc: Martin Lau <kafai@fb.com> Signed-off-by:
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Stanislav Fomichev authored
And let it use bpf_sk_storage_{get,delete} helpers to access socket storage. Kernel context (struct bpf_sock_ops_kern) already has sk member, so I just expose it to the BPF hooks. I use PTR_TO_SOCKET_OR_NULL and return NULL in !is_fullsock case. I also export bpf_tcp_sock to make it possible to access tcp socket stats. Cc: Martin Lau <kafai@fb.com> Signed-off-by: -
Stanislav Fomichev authored
And let it use bpf_sk_storage_{get,delete} helpers to access socket storage. Kernel context (struct bpf_sock_addr_kern) already has sk member, so I just expose it to the BPF hooks. Using PTR_TO_SOCKET instead of PTR_TO_SOCK_COMMON should be safe because the hook is called on bind/connect. Cc: Martin Lau <kafai@fb.com> Signed-off-by: -
Martin KaFai Lau authored
This patch adds a test for the new sockopt SO_REUSEPORT_DETACH_BPF. Signed-off-by:
Martin KaFai Lau <kafai@fb.com> Reviewed-by:
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Martin KaFai Lau authored
SO_DETACH_REUSEPORT_BPF is needed for the test in the next patch. It is defined in the socket.h. Signed-off-by:
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Martin KaFai Lau authored
There is SO_ATTACH_REUSEPORT_[CE]BPF but there is no DETACH. This patch adds SO_DETACH_REUSEPORT_BPF sockopt. The same sockopt can be used to undo both SO_ATTACH_REUSEPORT_[CE]BPF. reseport_detach_prog() is added and it is mostly a mirror of the existing reuseport_attach_prog(). The differences are, it does not call reuseport_alloc() and returns -ENOENT when there is no old prog. Cc: Craig Gallek <kraig@google.com> Signed-off-by:
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Andrii Nakryiko authored
Kernel internally checks that either key or value type ID is specified, before using btf_fd. Do the same in libbpf's map creation code for determining when to retry map creation w/o BTF. Reported-by:
Dan Carpenter <dan.carpenter@oracle.com> Fixes: fba01a06 ("libbpf: use negative fd to specify missing BTF") Signed-off-by:
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Dan Carpenter authored
The "len" variable needs to be signed for the error handling to work properly. Fixes: 596092ef ("selftests/bpf: enable all available cgroup v2 controllers") Signed-off-by:
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Prashant Bhole authored
Recent commit included libbpf.h in selftests/bpf/bpf_util.h. Since some samples use bpf_util.h and samples/bpf/Makefile doesn't have libbpf.h path included, build was failing. Let's add the path in samples/bpf/Makefile. Signed-off-by:
Prashant Bhole <prashantbhole.linux@gmail.com> Signed-off-by:
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- 12 Jun, 2019 1 commit
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Valdis Klētnieks authored
Compiling kernel/bpf/core.c with W=1 causes a flood of warnings: kernel/bpf/core.c:1198:65: warning: initialized field overwritten [-Woverride-init] 1198 | #define BPF_INSN_3_TBL(x, y, z) [BPF_##x | BPF_##y | BPF_##z] = true | ^~~~ kernel/bpf/core.c:1087:2: note: in expansion of macro 'BPF_INSN_3_TBL' 1087 | INSN_3(ALU, ADD, X), \ | ^~~~~~ kernel/bpf/core.c:1202:3: note: in expansion of macro 'BPF_INSN_MAP' 1202 | BPF_INSN_MAP(BPF_INSN_2_TBL, BPF_INSN_3_TBL), | ^~~~~~~~~~~~ kernel/bpf/core.c:1198:65: note: (near initialization for 'public_insntable[12]') 1198 | #define BPF_INSN_3_TBL(x, y, z) [BPF_##x | BPF_##y | BPF_##z] = true | ^~~~ kernel/bpf/core.c:1087:2: note: in expansion of macro 'BPF_INSN_3_TBL' 1087 | INSN_3(ALU, ADD, X), \ | ^~~~~~ kernel/bpf/core.c:1202:3: note: in expansion of macro 'BPF_INSN_MAP' 1202 | BPF_INSN_MAP(BPF_INSN_2_TBL, BPF_INSN_3_TBL), | ^~~~~~~~~~~~ 98 copies of the above. The attached patch silences the warnings, because we *know* we're overwriting the default initializer. That leaves bpf/core.c with only 6 other warnings, which become more visible in comparison. Signed-off-by:Valdis Kletnieks <valdis.kletnieks@vt.edu> Acked-by:
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- 11 Jun, 2019 5 commits
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Daniel Borkmann authored
Hechao Li says: ==================== Getting number of possible CPUs is commonly used for per-CPU BPF maps and perf_event_maps. Add a new API libbpf_num_possible_cpus() that helps user with per-CPU related operations and remove duplicate implementations in bpftool and selftests. v2: Save errno before calling pr_warning in case it is changed. v3: Make sure libbpf_num_possible_cpus never returns 0 so that user only has to check if ret value < 0. v4: Fix error code when reading 0 bytes from possible CPU file. v5: Fix selftests compliation issue. v6: Split commit to reuse libbpf_num_possible_cpus() into two commits: One commit to remove bpf_util.h from test BPF C programs. One commit to reuse libbpf_num_possible_cpus() in bpftools and bpf_util.h. ==================== Signed-off-by: -
Hechao Li authored
Use the newly added bpf_num_possible_cpus() in bpftool and selftests and remove duplicate implementations. Signed-off-by:
Hechao Li <hechaol@fb.com> Signed-off-by:
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Hechao Li authored
Though currently there is no problem including bpf_util.h in kernel space BPF C programs, in next patch in this stack, I will reuse libbpf_num_possible_cpus() in bpf_util.h thus include libbpf.h in it, which will cause BPF C programs compile error. Therefore I will first remove bpf_util.h from all test BPF programs. This can also make it clear that bpf_util.h is a user-space utility while bpf_helpers.h is a kernel space utility. Signed-off-by:
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Hechao Li authored
Adding a new API libbpf_num_possible_cpus() that helps user with per-CPU map operations. Signed-off-by:
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Hechao Li authored
An error "implicit declaration of function 'reallocarray'" can be thrown with the following steps: $ cd tools/testing/selftests/bpf $ make clean && make CC=<Path to GCC 4.8.5> $ make clean && make CC=<Path to GCC 7.x> The cause is that the feature folder generated by GCC 4.8.5 is not removed, leaving feature-reallocarray being 1, which causes reallocarray not defined when re-compliing with GCC 7.x. This diff adds feature folder to EXTRA_CLEAN to avoid this problem. v2: Rephrase the commit message. Signed-off-by:
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