- 29 Sep, 2020 40 commits
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Jiri Olsa authored
Adding test that setup following program: SEC("classifier/test_pkt_md_access") int test_pkt_md_access(struct __sk_buff *skb) with its extension: SEC("freplace/test_pkt_md_access") int test_pkt_md_access_new(struct __sk_buff *skb) and tracing that extension with: SEC("fentry/test_pkt_md_access_new") int BPF_PROG(fentry, struct sk_buff *skb) The test verifies that the tracing program can dereference skb argument properly. Signed-off-by:Jiri Olsa <jolsa@kernel.org> Signed-off-by:
Toke Høiland-Jørgensen <toke@redhat.com> Signed-off-by:
Alexei Starovoitov <ast@kernel.org> Acked-by:
Andrii Nakryiko <andriin@fb.com> Link: https://lore.kernel.org/bpf/160138355603.48470.9072073357530773228.stgit@toke.dk
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Toke Høiland-Jørgensen authored
This adds a selftest for attaching an freplace program to multiple targets simultaneously. Signed-off-by:
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Toke Høiland-Jørgensen authored
This adds support for supplying a target btf ID for the bpf_link_create() operation, and adds a new bpf_program__attach_freplace() high-level API for attaching freplace functions with a target. Signed-off-by:
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Toke Høiland-Jørgensen authored
Eelco reported we can't properly access arguments if the tracing program is attached to extension program. Having following program: SEC("classifier/test_pkt_md_access") int test_pkt_md_access(struct __sk_buff *skb) with its extension: SEC("freplace/test_pkt_md_access") int test_pkt_md_access_new(struct __sk_buff *skb) and tracing that extension with: SEC("fentry/test_pkt_md_access_new") int BPF_PROG(fentry, struct sk_buff *skb) It's not possible to access skb argument in the fentry program, with following error from verifier: ; int BPF_PROG(fentry, struct sk_buff *skb) 0: (79) r1 = *(u64 *)(r1 +0) invalid bpf_context access off=0 size=8 The problem is that btf_ctx_access gets the context type for the traced program, which is in this case the extension. But when we trace extension program, we want to get the context type of the program that the extension is attached to, so we can access the argument properly in the trace program. This version of the patch is tweaked slightly from Jiri's original one, since the refactoring in the previous patches means we have to get the target prog type from the new variable in prog->aux instead of directly from the target prog. Reported-by:Eelco Chaudron <echaudro@redhat.com> Suggested-by:
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Toke Høiland-Jørgensen authored
This enables support for attaching freplace programs to multiple attach points. It does this by amending the UAPI for bpf_link_Create with a target btf ID that can be used to supply the new attachment point along with the target program fd. The target must be compatible with the target that was supplied at program load time. The implementation reuses the checks that were factored out of check_attach_btf_id() to ensure compatibility between the BTF types of the old and new attachment. If these match, a new bpf_tracing_link will be created for the new attach target, allowing multiple attachments to co-exist simultaneously. The code could theoretically support multiple-attach of other types of tracing programs as well, but since I don't have a use case for any of those, there is no API support for doing so. Signed-off-by:
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Toke Høiland-Jørgensen authored
In preparation for allowing multiple attachments of freplace programs, move the references to the target program and trampoline into the bpf_tracing_link structure when that is created. To do this atomically, introduce a new mutex in prog->aux to protect writing to the two pointers to target prog and trampoline, and rename the members to make it clear that they are related. With this change, it is no longer possible to attach the same tracing program multiple times (detaching in-between), since the reference from the tracing program to the target disappears on the first attach. However, since the next patch will let the caller supply an attach target, that will also make it possible to attach to the same place multiple times. Signed-off-by:
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Alexei Starovoitov authored
Andrii Nakryiko says: ==================== Add support for loading and storing BTF in either little- or big-endian integer encodings, regardless of host endianness. This allows users of libbpf to not care about endianness when they don't want to and transparently open/load BTF of any endianness. libbpf will preserve original endianness and will convert output raw data as necessary back to original endianness, if necessary. This allows tools like pahole to be ignorant to such issues during cross-compilation. While working with BTF data in memory, the endianness is always native to the host. Convetion can happen only during btf__get_raw_data() call, and only in a raw data copy. Additionally, it's possible to force output BTF endianness through new btf__set_endianness() API. This which allows to create flexible tools doing arbitrary conversions of BTF endianness, just by relying on libbpf. Cc: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com> Cc: Tony Ambardar <tony.ambardar@gmail.com> Cc: Ilya Leoshkevich <iii@linux.ibm.com> Cc: Luka Perkov <luka.perkov@sartura.hr> ==================== Signed-off-by: -
Andrii Nakryiko authored
Add selftests juggling endianness back and forth to validate BTF's handling of endianness convertions internally. Signed-off-by:
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Andrii Nakryiko authored
Teach BTF to recognized wrong endianness and transparently convert it internally to host endianness. Original endianness of BTF will be preserved and used during btf__get_raw_data() to convert resulting raw data to the same endianness and a source raw_data. This means that little-endian host can parse big-endian BTF with no issues, all the type data will be presented to the client application in native endianness, but when it's time for emitting BTF to persist it in a file (e.g., after BTF deduplication), original non-native endianness will be preserved and stored. It's possible to query original endianness of BTF data with new btf__endianness() API. It's also possible to override desired output endianness with btf__set_endianness(), so that if application needs to load, say, big-endian BTF and store it as little-endian BTF, it's possible to manually override this. If btf__set_endianness() was used to change endianness, btf__endianness() will reflect overridden endianness. Given there are no known use cases for supporting cross-endianness for .BTF.ext, loading .BTF.ext in non-native endianness is not supported. Signed-off-by:
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Andrii Nakryiko authored
Move existing ASSERT_xxx() macros out of btf_write selftest into test_progs.h to use across all selftests. Also expand a set of macros for typical cases. Now there are the following macros: - ASSERT_EQ() -- check for equality of two integers; - ASSERT_STREQ() -- check for equality of two C strings; - ASSERT_OK() -- check for successful (zero) return result; - ASSERT_ERR() -- check for unsuccessful (non-zero) return result; - ASSERT_NULL() -- check for NULL pointer; - ASSERT_OK_PTR() -- check for a valid pointer; - ASSERT_ERR_PTR() -- check for NULL or negative error encoded in a pointer. Signed-off-by:
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Toke Høiland-Jørgensen authored
If programs in prog_tests using skeletons declare the 'skel' variable as global but not static, that will lead to linker errors on the final link of the prog_tests binary due to duplicate symbols. Fix a few instances of this. Fixes: b18c1f0a ("bpf: selftest: Adapt sock_fields test to use skel and global variables") Fixes: 9a856cae ("bpf: selftest: Add test_btf_skc_cls_ingress") Signed-off-by:
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Ciara Loftus authored
After 'peeking' the ring, the consumer, not the producer, reads the data. Fix this mistake in the comments. Fixes: 15d8c916 ("xsk: Add function naming comments and reorder functions") Signed-off-by:
Ciara Loftus <ciara.loftus@intel.com> Signed-off-by:
Magnus Karlsson <magnus.karlsson@intel.com> Link: https://lore.kernel.org/bpf/20200928082344.17110-1-ciara.loftus@intel.com
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Toke Høiland-Jørgensen authored
The new test for task iteration in bpf_iter checks (in do_btf_read()) if it should be skipped due to missing __builtin_btf_type_id. However, this 'skip' verdict is not propagated to the caller, so the parent test will still fail. Fix this by also skipping the rest of the parent test if the skip condition was reached. Fixes: b72091bd ("selftests/bpf: Add test for bpf_seq_printf_btf helper") Signed-off-by:
Alan Maguire <alan.maguire@oracle.com> Link: https://lore.kernel.org/bpf/20200929123004.46694-1-toke@redhat.com
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Toke Høiland-Jørgensen authored
The Makefile in bpf/preload builds a local copy of libbpf, but does not properly clean up after itself. This can lead to subsequent compilation failures, since the feature detection cache is kept around which can lead subsequent detection to fail. Fix this by properly setting clean-files, and while we're at it, also add a .gitignore for the directory to ignore the build artifacts. Fixes: d71fa5c9 ("bpf: Add kernel module with user mode driver that populates bpffs.") Signed-off-by:
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Alexei Starovoitov authored
Alan Maguire says: ==================== Resolve issues in bpf selftests introduced with BTF-based kernel data display selftests; these are - a warning introduced in snprintf_btf.c; and - compilation failures with old kernels vmlinux.h ==================== Signed-off-by: -
Alan Maguire authored
Andrii reports that bpf selftests relying on "struct btf_ptr" and BTF_F_* values will not build as vmlinux.h for older kernels will not include "struct btf_ptr" or the BTF_F_* enum values. Undefine and redefine them to work around this. Fixes: b72091bd ("selftests/bpf: Add test for bpf_seq_printf_btf helper") Fixes: 076a95f5 ("selftests/bpf: Add bpf_snprintf_btf helper tests") Reported-by:
Andrii Nakryiko <andrii.nakryiko@gmail.com> Signed-off-by:
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Alan Maguire authored
Daniel reports: + system("ping -c 1 127.0.0.1 > /dev/null"); This generates the following new warning when compiling BPF selftests: [...] EXT-OBJ [test_progs] cgroup_helpers.o EXT-OBJ [test_progs] trace_helpers.o EXT-OBJ [test_progs] network_helpers.o EXT-OBJ [test_progs] testing_helpers.o TEST-OBJ [test_progs] snprintf_btf.test.o /root/bpf-next/tools/testing/selftests/bpf/prog_tests/snprintf_btf.c: In function ‘test_snprintf_btf’: /root/bpf-next/tools/testing/selftests/bpf/prog_tests/snprintf_btf.c:30:2: warning: ignoring return value of ‘system’, declared with attribute warn_unused_result [-Wunused-result] system("ping -c 1 127.0.0.1 > /dev/null"); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ [...] Fixes: 076a95f5 ("selftests/bpf: Add bpf_snprintf_btf helper tests") Reported-by:Daniel Borkmann <daniel@iogearbox.net> Signed-off-by:
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John Fastabend authored
Fix warning in bpf selftests, progs/test_raw_tp_test_run.c:18:10: warning: cast to smaller integer type 'int' from 'struct task_struct *' [-Wpointer-to-int-cast] Change int type cast to long to fix. Discovered with gcc-9 and llvm-11+ where llvm was recent main branch. Fixes: 09d8ad16 ("selftests/bpf: Add raw_tp_test_run") Signed-off-by:
John Fastabend <john.fastabend@gmail.com> Signed-off-by:
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Alexei Starovoitov authored
Andrii Nakryiko says: ==================== This patch set introduces a new set of BTF APIs to libbpf that allow to conveniently produce BTF types and strings. These APIs will allow libbpf to do more intrusive modifications of program's BTF (by rewriting it, at least as of right now), which is necessary for the upcoming libbpf static linking. But they are complete and generic, so can be adopted by anyone who has a need to produce BTF type information. One such example outside of libbpf is pahole, which was actually converted to these APIs (locally, pending landing of these changes in libbpf) completely and shows reduction in amount of custom pahole code necessary and brings nice savings in memory usage (about 370MB reduction at peak for my kernel configuration) and even BTF deduplication times (one second reduction, 23.7s -> 22.7s). Memory savings are due to avoiding pahole's own copy of "uncompressed" raw BTF data. Time reduction comes from faster string search and deduplication by relying on hashmap instead of BST used by pahole's own code. Consequently, these APIs are already tested on real-world complicated kernel BTF, but there is also pretty extensive selftest doing extra validations. Selftests in patch #3 add a set of generic ASSERT_{EQ,STREQ,ERR,OK} macros that are useful for writing shorter and less repretitive selftests. I decided to keep them local to that selftest for now, but if they prove to be useful in more contexts we should move them to test_progs.h. And few more (e.g., inequality tests) macros are probably necessary to have a more complete set. Cc: Arnaldo Carvalho de Melo <acme@redhat.com> v2->v3: - resending original patches #7-9 as patches #1-3 due to merge conflict; v1->v2: - fixed comments (John); - renamed btf__append_xxx() into btf__add_xxx() (Alexei); - added btf__find_str() in addition to btf__add_str(); - btf__new_empty() now sets kernel FD to -1 initially. ==================== Signed-off-by: -
Andrii Nakryiko authored
Add selftests for BTF writer APIs. Signed-off-by:
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Andrii Nakryiko authored
BTF strings are used not just for names, they can be arbitrary strings used for CO-RE relocations, line/func infos, etc. Thus "name_by_offset" terminology is too specific and might be misleading. Instead, introduce btf__str_by_offset() API which uses generic string terminology. Signed-off-by:
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Andrii Nakryiko authored
Add APIs for appending new BTF types at the end of BTF object. Each BTF kind has either one API of the form btf__add_<kind>(). For types that have variable amount of additional items (struct/union, enum, func_proto, datasec), additional API is provided to emit each such item. E.g., for emitting a struct, one would use the following sequence of API calls: btf__add_struct(...); btf__add_field(...); ... btf__add_field(...); Each btf__add_field() will ensure that the last BTF type is of STRUCT or UNION kind and will automatically increment that type's vlen field. All the strings are provided as C strings (const char *), not a string offset. This significantly improves usability of BTF writer APIs. All such strings will be automatically appended to string section or existing string will be re-used, if such string was already added previously. Each API attempts to do all the reasonable validations, like enforcing non-empty names for entities with required names, proper value bounds, various bit offset restrictions, etc. Type ID validation is minimal because it's possible to emit a type that refers to type that will be emitted later, so libbpf has no way to enforce such cases. User must be careful to properly emit all the necessary types and specify type IDs that will be valid in the finally generated BTF. Each of btf__add_<kind>() APIs return new type ID on success or negative value on error. APIs like btf__add_field() that emit additional items return zero on success and negative value on error. Signed-off-by:
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Alexei Starovoitov authored
Alan Maguire says: ==================== This series attempts to provide a simple way for BPF programs (and in future other consumers) to utilize BPF Type Format (BTF) information to display kernel data structures in-kernel. The use case this functionality is applied to here is to support a snprintf()-like helper to copy a BTF representation of kernel data to a string, and a BPF seq file helper to display BTF data for an iterator. There is already support in kernel/bpf/btf.c for "show" functionality; the changes here generalize that support from seq-file specific verifier display to the more generic case and add another specific use case; rather than seq_printf()ing the show data, it is copied to a supplied string using a snprintf()-like function. Other future consumers of the show functionality could include a bpf_printk_btf() function which printk()ed the data instead. Oops messaging in particular would be an interesting application for such functionality. The above potential use case hints at a potential reply to a reasonable objection that such typed display should be solved by tracing programs, where the in-kernel tracing records data and the userspace program prints it out. While this is certainly the recommended approach for most cases, I believe having an in-kernel mechanism would be valuable also. Critically in BPF programs it greatly simplifies debugging and tracing of such data to invoking a simple helper. One challenge raised in an earlier iteration of this work - where the BTF printing was implemented as a printk() format specifier - was that the amount of data printed per printk() was large, and other format specifiers were far simpler. Here we sidestep that concern by printing components of the BTF representation as we go for the seq file case, and in the string case the snprintf()-like operation is intended to be a basis for perf event or ringbuf output. The reasons for avoiding bpf_trace_printk are that 1. bpf_trace_printk() strings are restricted in size and cannot display anything beyond trivial data structures; and 2. bpf_trace_printk() is for debugging purposes only. As Alexei suggested, a bpf_trace_puts() helper could solve this in the future but it still would be limited by the 1000 byte limit for traced strings. Default output for an sk_buff looks like this (zeroed fields are omitted): (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 can modify aspects of output format; see patch 3 for more details. Changes since v6: - Updated safe data size to 32, object name size to 80. This increases the number of safe copies done, but performance is not a key goal here. WRT name size the largest type name length in bpf-next according to "pahole -s" is 64 bytes, so that still gives room for additional type qualifiers, parens etc within the name limit (Alexei, patch 2) - Remove inlines and converted as many #defines to functions as was possible. In a few cases - btf_show_type_value[s]() specifically - I left these as macros as btf_show_type_value[s]() prepends and appends format strings to the format specifier (in order to include indentation, delimiters etc so a macro makes that simpler (Alexei, patch 2) - Handle btf_resolve_size() error in btf_show_obj_safe() (Alexei, patch 2) - Removed clang loop unroll in BTF snprintf test (Alexei) - switched to using bpf_core_type_id_kernel(type) as suggested by Andrii, and Alexei noted that __builtin_btf_type_id(,1) should be used (patch 4) - Added skip logic if __builtin_btf_type_id is not available (patches 4,8) - Bumped limits on bpf iters to support printing larger structures (Alexei, patch 5) - Updated overflow bpf_iter tests to reflect new iter max size (patch 6) - Updated seq helper to use type id only (Alexei, patch 7) - Updated BTF task iter test to use task struct instead of struct fs_struct since new limits allow a task_struct to be displayed (patch 8) - Fixed E2BIG handling in iter task (Alexei, patch 8) Changes since v5: - Moved btf print prepare into patch 3, type show seq with flags into patch 2 (Alexei, patches 2,3) - Fixed build bot warnings around static declarations and printf attributes - Renamed functions to snprintf_btf/seq_printf_btf (Alexei, patches 3-6) Changes since v4: - Changed approach from a BPF trace event-centric design to one utilizing a snprintf()-like helper and an iter helper (Alexei, patches 3,5) - Added tests to verify BTF output (patch 4) - Added support to tests for verifying BTF type_id-based display as well as type name via __builtin_btf_type_id (Andrii, patch 4). - Augmented task iter tests to cover the BTF-based seq helper. Because a task_struct's BTF-based representation would overflow the PAGE_SIZE limit on iterator data, the "struct fs_struct" (task->fs) is displayed for each task instead (Alexei, patch 6). Changes since v3: - Moved to RFC since the approach is different (and bpf-next is closed) - Rather than using a printk() format specifier as the means of invoking BTF-enabled display, a dedicated BPF helper is used. This solves the issue of printk() having to output large amounts of data using a complex mechanism such as BTF traversal, but still provides a way for the display of such data to be achieved via BPF programs. Future work could include a bpf_printk_btf() function to invoke display via printk() where the elements of a data structure are printk()ed one at a time. Thanks to Petr Mladek, Andy Shevchenko and Rasmus Villemoes who took time to look at the earlier printk() format-specifier-focused version of this and provided feedback clarifying the problems with that approach. - Added trace id to the bpf_trace_printk events as a means of separating output from standard bpf_trace_printk() events, ensuring it can be easily parsed by the reader. - Added bpf_trace_btf() helper tests which do simple verification of the various display options. Changes since v2: - Alexei and Yonghong suggested it would be good to use probe_kernel_read() on to-be-shown data to ensure safety during operation. Safe copy via probe_kernel_read() to a buffer object in "struct btf_show" is used to support this. A few different approaches were explored including dynamic allocation and per-cpu buffers. The downside of dynamic allocation is that it would be done during BPF program execution for bpf_trace_printk()s using %pT format specifiers. The problem with per-cpu buffers is we'd have to manage preemption and since the display of an object occurs over an extended period and in printk context where we'd rather not change preemption status, it seemed tricky to manage buffer safety while considering preemption. The approach of utilizing stack buffer space via the "struct btf_show" seemed like the simplest approach. The stack size of the associated functions which have a "struct btf_show" on their stack to support show operation (btf_type_snprintf_show() and btf_type_seq_show()) stays under 500 bytes. The compromise here is the safe buffer we use is small - 256 bytes - and as a result multiple probe_kernel_read()s are needed for larger objects. Most objects of interest are smaller than this (e.g. "struct sk_buff" is 224 bytes), and while task_struct is a notable exception at ~8K, performance is not the priority for BTF-based display. (Alexei and Yonghong, patch 2). - safe buffer use is the default behaviour (and is mandatory for BPF) but unsafe display - meaning no safe copy is done and we operate on the object itself - is supported via a 'u' option. - pointers are prefixed with 0x for clarity (Alexei, patch 2) - added additional comments and explanations around BTF show code, especially around determining whether objects such zeroed. Also tried to comment safe object scheme used. (Yonghong, patch 2) - added late_initcall() to initialize vmlinux BTF so that it would not have to be initialized during printk operation (Alexei, patch 5) - removed CONFIG_BTF_PRINTF config option as it is not needed; CONFIG_DEBUG_INFO_BTF can be used to gate test behaviour and determining behaviour of type-based printk can be done via retrieval of BTF data; if it's not there BTF was unavailable or broken (Alexei, patches 4,6) - fix bpf_trace_printk test to use vmlinux.h and globals via skeleton infrastructure, removing need for perf events (Andrii, patch 8) Changes since v1: - changed format to be more drgn-like, rendering indented type info along with type names by default (Alexei) - zeroed values are omitted (Arnaldo) by default unless the '0' modifier is specified (Alexei) - added an option to print pointer values without obfuscation. The reason to do this is the sysctls controlling pointer display are likely to be irrelevant in many if not most tracing contexts. Some questions on this in the outstanding questions section below... - reworked printk format specifer so that we no longer rely on format %pT<type> but instead use a struct * which contains type information (Rasmus). This simplifies the printk parsing, makes use more dynamic and also allows specification by BTF id as well as name. - removed incorrect patch which tried to fix dereferencing of resolved BTF info for vmlinux; instead we skip modifiers for the relevant case (array element type determination) (Alexei). - fixed issues with negative snprintf format length (Rasmus) - added test cases for various data structure formats; base types, typedefs, structs, etc. - tests now iterate through all typedef, enum, struct and unions defined for vmlinux BTF and render a version of the target dummy value which is either all zeros or all 0xff values; the idea is this exercises the "skip if zero" and "print everything" cases. - added support in BPF for using the %pT format specifier in bpf_trace_printk() - added BPF tests which ensure %pT format specifier use works (Alexei). ==================== Signed-off-by: -
Alan Maguire authored
Add a test verifying iterating over tasks and displaying BTF representation of task_struct succeeds. Suggested-by:
Alexei Starovoitov <alexei.starovoitov@gmail.com> Signed-off-by:
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Alan Maguire authored
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: -
Alan Maguire authored
bpf iter size increase to PAGE_SIZE << 3 means overflow tests assuming page size need to be bumped also. Signed-off-by:
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Alan Maguire authored
BPF iter size is limited to PAGE_SIZE; if we wish to display BTF-based representations of larger kernel data structures such as task_struct, this will be insufficient. Suggested-by:
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Alan Maguire authored
Tests verifying snprintf()ing of various data structures, flags combinations using a tp_btf program. Tests are skipped if __builtin_btf_type_id is not available to retrieve BTF type ids. Signed-off-by:
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Alan Maguire authored
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 authored
generalize the "seq_show" seq file support in btf.c to support a generic show callback of which we support two instances; the current seq file show, and a show with snprintf() behaviour which instead writes the type data to a supplied string. Both classes of show function call btf_type_show() with different targets; the seq file or the string to be written. In the string case we need to track additional data - length left in string to write and length to return that we would have written (a la snprintf). By default show will display type information, field members and their types and values etc, and the information is indented based upon structure depth. Zeroed fields are omitted. Show however supports flags which modify its behaviour: BTF_SHOW_COMPACT - suppress newline/indent. BTF_SHOW_NONAME - suppress show of type and member names. BTF_SHOW_PTR_RAW - do not obfuscate pointer values. BTF_SHOW_UNSAFE - do not copy data to safe buffer before display. BTF_SHOW_ZERO - show zeroed values (by default they are not shown). Signed-off-by:
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Alan Maguire authored
It will be used later for BPF structure display support Signed-off-by:
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Andrii Nakryiko authored
Add an ability to create an empty BTF object from scratch. This is going to be used by pahole for BTF encoding. And also by selftest for convenient creation of BTF objects. Signed-off-by:
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Andrii Nakryiko authored
Allow internal BTF representation to switch from default read-only mode, in which raw BTF data is a single non-modifiable block of memory with BTF header, types, and strings layed out sequentially and contiguously in memory, into a writable representation with types and strings data split out into separate memory regions, that can be dynamically expanded. Such writable internal representation is transparent to users of libbpf APIs, but allows to append new types and strings at the end of BTF, which is a typical use case when generating BTF programmatically. All the basic guarantees of BTF types and strings layout is preserved, i.e., user can get `struct btf_type *` pointer and read it directly. Such btf_type pointers might be invalidated if BTF is modified, so some care is required in such mixed read/write scenarios. Switch from read-only to writable configuration happens automatically the first time when user attempts to modify BTF by either adding a new type or new string. It is still possible to get raw BTF data, which is a single piece of memory that can be persisted in ELF section or into a file as raw BTF. Such raw data memory is also still owned by BTF and will be freed either when BTF object is freed or if another modification to BTF happens, as any modification invalidates BTF raw representation. This patch adds the first two BTF manipulation APIs: btf__add_str(), which allows to add arbitrary strings to BTF string section, and btf__find_str() which allows to find existing string offset, but not add it if it's missing. All the added strings are automatically deduplicated. This is achieved by maintaining an additional string lookup index for all unique strings. Such index is built when BTF is switched to modifiable mode. If at that time BTF strings section contained duplicate strings, they are not de-duplicated. This is done specifically to not modify the existing content of BTF (types, their string offsets, etc), which can cause confusion and is especially important property if there is struct btf_ext associated with struct btf. By following this "imperfect deduplication" process, btf_ext is kept consitent and correct. If deduplication of strings is necessary, it can be forced by doing BTF deduplication, at which point all the strings will be eagerly deduplicated and all string offsets both in struct btf and struct btf_ext will be updated. Signed-off-by:
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Andrii Nakryiko authored
Calculating a hash of zero-terminated string is a common need when using hashmap, so extract it for reuse. Signed-off-by:
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Andrii Nakryiko authored
Managing dynamically-sized array is a common, but not trivial functionality, which significant amount of logic and code to implement properly. So instead of re-implementing it all the time, extract it into a helper function ans reuse. Signed-off-by:
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Andrii Nakryiko authored
Refactor internals of struct btf to remove assumptions that BTF header, type data, and string data are layed out contiguously in a memory in a single memory allocation. Now we have three separate pointers pointing to the start of each respective are: header, types, strings. In the next patches, these pointers will be re-assigned to point to independently allocated memory areas, if BTF needs to be modified. Signed-off-by:
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Andrii Nakryiko authored
Refactor implementation of internal BTF type index to not use direct pointers. Instead it uses offset relative to the start of types data section. This allows for types data to be reallocatable, enabling implementation of modifiable BTF. As now getting type by ID has an extra indirection step, convert all internal type lookups to a new helper btf_type_id(), that returns non-const pointer to a type by its ID. Signed-off-by:
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Toke Høiland-Jørgensen authored
The test_overhead prog_test included an fmod_ret program that attached to __set_task_comm() in the kernel. However, this function was never listed as allowed for return modification, so this only worked because of the verifier skipping tests when a trampoline already existed for the attach point. Now that the verifier checks have been fixed, remove fmod_ret from the test so it works again. Fixes: 4eaf0b5c ("selftest/bpf: Fmod_ret prog and implement test_overhead as part of bench") Acked-by:
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Toke Høiland-Jørgensen authored
The check_attach_btf_id() function really does three things: 1. It performs a bunch of checks on the program to ensure that the attachment is valid. 2. It stores a bunch of state about the attachment being requested in the verifier environment and struct bpf_prog objects. 3. It allocates a trampoline for the attachment. This patch splits out (1.) and (3.) into separate functions which will perform the checks, but return the computed values instead of directly modifying the environment. This is done in preparation for reusing the checks when the actual attachment is happening, which will allow tracing programs to have multiple (compatible) attachments. This also fixes a bug where a bunch of checks were skipped if a trampoline already existed for the tracing target. Fixes: 6ba43b76 ("bpf: Attachment verification for BPF_MODIFY_RETURN") Fixes: 1e6c62a8 ("bpf: Introduce sleepable BPF programs") Acked-by:
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Toke Høiland-Jørgensen authored
In preparation for moving code around, change a bunch of references to env->log (and the verbose() logging helper) to use bpf_log() and a direct pointer to struct bpf_verifier_log. While we're touching the function signature, mark the 'prog' argument to bpf_check_type_match() as const. Also enhance the bpf_verifier_log_needed() check to handle NULL pointers for the log struct so we can re-use the code with logging disabled. Acked-by:
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