- 13 Mar, 2020 31 commits
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Andrii Nakryiko authored
Add vmlinux.h generation to selftest/bpf's Makefile. Use it from newly added test_vmlinux to trace nanosleep syscall using 5 different types of programs: - tracepoint; - raw tracepoint; - raw tracepoint w/ direct memory reads (tp_btf); - kprobe; - fentry. These programs are realistic variants of real-life tracing programs, excercising vmlinux.h's usage with tracing applications. Signed-off-by:
Andrii Nakryiko <andriin@fb.com> Signed-off-by:
Daniel Borkmann <daniel@iogearbox.net> Acked-by:
Martin KaFai Lau <kafai@fb.com> Link: https://lore.kernel.org/bpf/20200313172336.1879637-5-andriin@fb.com
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Andrii Nakryiko authored
Syscall raw tracepoints have struct pt_regs pointer as tracepoint's first argument. After that, reading any of pt_regs fields requires bpf_probe_read(), even for tp_btf programs. Due to that, PT_REGS_PARMx macros are not usable as is. This patch adds CO-RE variants of those macros that use BPF_CORE_READ() to read necessary fields. This provides relocatable architecture-agnostic pt_regs field accesses. Signed-off-by:
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Andrii Nakryiko authored
When finding target type candidates, ignore forward declarations, functions, and other named types of incompatible kind. Not doing this can cause false errors. See [0] for one such case (due to struct pt_regs forward declaration). [0] https://github.com/iovisor/bcc/pull/2806#issuecomment-598543645 Fixes: ddc7c304 ("libbpf: implement BPF CO-RE offset relocation algorithm") Reported-by:
Wenbo Zhang <ethercflow@gmail.com> Signed-off-by:
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Andrii Nakryiko authored
printf() doesn't seem to honor using overwritten stdout/stderr (as part of stdio hijacking), so ensure all "standard" invocations of printf() do fprintf(stdout, ...) instead. Signed-off-by:
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Jakub Sitnicki authored
Andrii Nakryiko reports that sockmap_listen test suite is frequently failing due to accept() calls erroring out with EAGAIN: ./test_progs:connect_accept_thread:733: accept: Resource temporarily unavailable connect_accept_thread:FAIL:733 This is because we are using a non-blocking listening TCP socket to accept() connections without polling on the socket. While at first switching to blocking mode seems like the right thing to do, this could lead to test process blocking indefinitely in face of a network issue, like loopback interface being down, as Andrii pointed out. Hence, stick to non-blocking mode for TCP listening sockets but with polling for incoming connection for a limited time before giving up. Apply this approach to all socket I/O calls in the test suite that we expect to block indefinitely, that is accept() for TCP and recv() for UDP. Fixes: 44d28be2 ("selftests/bpf: Tests for sockmap/sockhash holding listening sockets") Reported-by:
Andrii Nakryiko <andrii.nakryiko@gmail.com> Signed-off-by:
Jakub Sitnicki <jakub@cloudflare.com> Signed-off-by:
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Tobias Klauser authored
Commit fe4eb069 ("bpftool: Use linux/types.h from source tree for profiler build") added a build dependency on tools/testing/selftests/bpf to tools/bpf/bpftool. This is suboptimal with respect to a possible stand-alone build of bpftool. Fix this by moving tools/testing/selftests/bpf/include/uapi/linux/types.h to tools/include/uapi/linux/types.h. This requires an adjustment in the include search path order for the tests in tools/testing/selftests/bpf so that tools/include/linux/types.h is selected when building host binaries and tools/include/uapi/linux/types.h is selected when building bpf binaries. Verified by compiling bpftool and the bpf selftests on x86_64 with this change. Fixes: fe4eb069 ("bpftool: Use linux/types.h from source tree for profiler build") Suggested-by:
Tobias Klauser <tklauser@distanz.ch> Signed-off-by:
Quentin Monnet <quentin@isovalent.com> Link: https://lore.kernel.org/bpf/20200313113105.6918-1-tklauser@distanz.ch
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Jules Irenge authored
Sparse reports a warning at __bpf_prog_enter() and __bpf_prog_exit() warning: context imbalance in __bpf_prog_enter() - wrong count at exit warning: context imbalance in __bpf_prog_exit() - unexpected unlock The root cause is the missing annotation at __bpf_prog_enter() and __bpf_prog_exit() Add the missing __acquires(RCU) annotation Add the missing __releases(RCU) annotation Signed-off-by:
Jules Irenge <jbi.octave@gmail.com> Signed-off-by:
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Carlos Neira authored
When compiling bpftool the following warning is found: "declaration of 'struct bpf_pidns_info' will not be visible outside of this function." This patch adds struct bpf_pidns_info to type_fwds array to fix this. Fixes: b4490c5c ("bpf: Added new helper bpf_get_ns_current_pid_tgid") Signed-off-by:
Carlos Neira <cneirabustos@gmail.com> Signed-off-by:
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Andrii Nakryiko authored
nanosleep syscall expects pointer to struct timespec, not nanoseconds directly. Current implementation fulfills its purpose of invoking nanosleep syscall, but doesn't really provide sleeping capabilities, which can cause flakiness for tests relying on usleep() to wait for something. Fixes: ec12a57b822c ("selftests/bpf: Guarantee that useep() calls nanosleep() syscall") Signed-off-by:Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20200313061837.3685572-1-andriin@fb.comSigned-off-by:
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Alexei Starovoitov authored
Jiri Olsa says: ==================== this patchset adds trampoline and dispatcher objects to be visible in /proc/kallsyms. $ sudo cat /proc/kallsyms | tail -20 ... ffffffffa050f000 t bpf_prog_5a2b06eab81b8f51 [bpf] ffffffffa0511000 t bpf_prog_6deef7357e7b4530 [bpf] ffffffffa0542000 t bpf_trampoline_13832 [bpf] ffffffffa0548000 t bpf_prog_96f1b5bf4e4cc6dc_mutex_lock [bpf] ffffffffa0572000 t bpf_prog_d1c63e29ad82c4ab_bpf_prog1 [bpf] ffffffffa0585000 t bpf_prog_e314084d332a5338__dissect [bpf] ffffffffa0587000 t bpf_prog_59785a79eac7e5d2_mutex_unlock [bpf] ffffffffa0589000 t bpf_prog_d0db6e0cac050163_mutex_lock [bpf] ffffffffa058d000 t bpf_prog_d8f047721e4d8321_bpf_prog2 [bpf] ffffffffa05df000 t bpf_trampoline_25637 [bpf] ffffffffa05e3000 t bpf_prog_d8f047721e4d8321_bpf_prog2 [bpf] ffffffffa05e5000 t bpf_prog_3b185187f1855c4c [bpf] ffffffffa05e7000 t bpf_prog_d8f047721e4d8321_bpf_prog2 [bpf] ffffffffa05eb000 t bpf_prog_93cebb259dd5c4b2_do_sys_open [bpf] ffffffffa0677000 t bpf_dispatcher_xdp [bpf] v5 changes: - keeping just 1 bpf_tree for all the objects and adding flag to recognize bpf_objects when searching for exception tables [Alexei] - no need for is_bpf_image_address call in kernel_text_address [Alexei] - removed the bpf_image tree, because it's no longer needed v4 changes: - add trampoline and dispatcher to kallsyms once the it's allocated [Alexei] - omit the symbols sorting for kallsyms [Alexei] - small title change in one patch [Song] - some function renames: bpf_get_prog_name to bpf_prog_ksym_set_name bpf_get_prog_addr_region to bpf_prog_ksym_set_addr - added acks to changelogs - I checked and there'll be conflict on perftool side with upcoming changes from Adrian Hunter (text poke events), so I think it's better if Arnaldo takes the perf changes via perf tree and we will solve all conflicts there v3 changes: - use container_of directly in bpf_get_ksym_start [Daniel] - add more changelog explanations for ksym addresses [Daniel] v2 changes: - omit extra condition in __bpf_ksym_add for sorting code (Andrii) - rename bpf_kallsyms_tree_ops to bpf_ksym_tree (Andrii) - expose only executable code in kallsyms (Andrii) - use full trampoline key as its kallsyms id (Andrii) - explained the BPF_TRAMP_REPLACE case (Andrii) - small format changes in bpf_trampoline_link_prog/bpf_trampoline_unlink_prog (Andrii) - propagate error value in bpf_dispatcher_update and update kallsym if it's successful (Andrii) - get rid of __always_inline for bpf_ksym_tree callbacks (Andrii) - added KSYMBOL notification for bpf_image add/removal - added perf tools changes to properly display trampoline/dispatcher ==================== Signed-off-by: -
Jiri Olsa authored
Now that we have all the objects (bpf_prog, bpf_trampoline, bpf_dispatcher) linked in bpf_tree, there's no need to have separate bpf_image tree for images. Reverting the bpf_image tree together with struct bpf_image, because it's no longer needed. Also removing bpf_image_alloc function and adding the original bpf_jit_alloc_exec_page interface instead. The kernel_text_address function can now rely only on is_bpf_text_address, because it checks the bpf_tree that contains all the objects. Keeping bpf_image_ksym_add and bpf_image_ksym_del because they are useful wrappers with perf's ksymbol interface calls. Signed-off-by:
Jiri Olsa <jolsa@kernel.org> Signed-off-by:
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Jiri Olsa authored
Adding dispatchers to kallsyms. It's displayed as bpf_dispatcher_<NAME> where NAME is the name of dispatcher. Signed-off-by:
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Jiri Olsa authored
Adding trampolines to kallsyms. It's displayed as bpf_trampoline_<ID> [bpf] where ID is the BTF id of the trampoline function. Adding bpf_image_ksym_add/del functions that setup the start/end values and call KSYMBOL perf events handlers. Signed-off-by:
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Jiri Olsa authored
Separating /proc/kallsyms add/del code and adding bpf_ksym_add/del functions for that. Moving bpf_prog_ksym_node_add/del functions to __bpf_ksym_add/del and changing their argument to 'struct bpf_ksym' object. This way we can call them for other bpf objects types like trampoline and dispatcher. Signed-off-by:
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Jiri Olsa authored
Adding 'prog' bool flag to 'struct bpf_ksym' to mark that this object belongs to bpf_prog object. This change allows having bpf_prog objects together with other types (trampolines and dispatchers) in the single bpf_tree. It's used when searching for bpf_prog exception tables by the bpf_prog_ksym_find function, where we need to get the bpf_prog pointer. >From now we can safely add bpf_ksym support for trampoline or dispatcher objects, because we can differentiate them from bpf_prog objects. Signed-off-by:
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Andrii Nakryiko authored
Instead of requiring users to do three steps for cleaning up bpf_link, its anon_inode file, and unused fd, abstract that away into bpf_link_cleanup() helper. bpf_link_defunct() is removed, as it shouldn't be needed as an individual operation anymore. v1->v2: - keep bpf_link_cleanup() static for now (Daniel). Signed-off-by:
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Jiri Olsa authored
Adding bpf_ksym_find function that is used bpf bpf address lookup functions: __bpf_address_lookup is_bpf_text_address while keeping bpf_prog_kallsyms_find to be used only for lookup of bpf_prog objects (will happen in following changes). Signed-off-by:
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Andrii Nakryiko authored
Switch to non-blocking accept and wait for server thread to exit before proceeding. I noticed that sometimes tcp_rtt server thread failure would "spill over" into other tests (that would run after tcp_rtt), probably just because server thread exits much later and tcp_rtt doesn't wait for it. v1->v2: - add usleep() while waiting on initial non-blocking accept() (Stanislav); Fixes: 8a03222f ("selftests/bpf: test_progs: fix client/server race in tcp_rtt") Signed-off-by:
Stanislav Fomichev <sdf@google.com> Link: https://lore.kernel.org/bpf/20200311222749.458015-1-andriin@fb.comSigned-off-by:
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Jiri Olsa authored
Moving ksym_tnode list node to 'struct bpf_ksym' object, so the symbol itself can be chained and used in other objects like bpf_trampoline and bpf_dispatcher. We need bpf_ksym object to be linked both in bpf_kallsyms via lnode for /proc/kallsyms and in bpf_tree via tnode for bpf address lookup functions like __bpf_address_lookup or bpf_prog_kallsyms_find. Signed-off-by:
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Andrii Nakryiko authored
Some implementations of C runtime library won't call nanosleep() syscall from usleep(). But a bunch of kprobe/tracepoint selftests rely on nanosleep being called to trigger them. To make this more reliable, "override" usleep implementation and call nanosleep explicitly. Signed-off-by:
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Jiri Olsa authored
Adding lnode list node to 'struct bpf_ksym' object, so the struct bpf_ksym itself can be chained and used in other objects like bpf_trampoline and bpf_dispatcher. Changing iterator to bpf_ksym in bpf_get_kallsym function. The ksym->start is holding the prog->bpf_func value, so it's ok to use it as value in bpf_get_kallsym. Signed-off-by:
Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20200312195610.346362-6-jolsa@kernel.orgSigned-off-by:
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Quentin Monnet authored
In commit 4a3d6c6a ("libbpf: Reduce log level for custom section names"), log level for messages for libbpf_attach_type_by_name() and libbpf_prog_type_by_name() was downgraded from "info" to "debug". The latter function, in particular, is used by bpftool when attempting to load programs, and this change caused bpftool to exit with no hint or error message when it fails to detect the type of the program to load (unless "-d" option was provided). To help users understand why bpftool fails to load the program, let's do a second run of the function with log level in "debug" mode in case of failure. Before: # bpftool prog load sample_ret0.o /sys/fs/bpf/sample_ret0 # echo $? 255 Or really verbose with -d flag: # bpftool -d prog load sample_ret0.o /sys/fs/bpf/sample_ret0 libbpf: loading sample_ret0.o libbpf: section(1) .strtab, size 134, link 0, flags 0, type=3 libbpf: skip section(1) .strtab libbpf: section(2) .text, size 16, link 0, flags 6, type=1 libbpf: found program .text libbpf: section(3) .debug_abbrev, size 55, link 0, flags 0, type=1 libbpf: skip section(3) .debug_abbrev libbpf: section(4) .debug_info, size 75, link 0, flags 0, type=1 libbpf: skip section(4) .debug_info libbpf: section(5) .rel.debug_info, size 32, link 14, flags 0, type=9 libbpf: skip relo .rel.debug_info(5) for section(4) libbpf: section(6) .debug_str, size 150, link 0, flags 30, type=1 libbpf: skip section(6) .debug_str libbpf: section(7) .BTF, size 155, link 0, flags 0, type=1 libbpf: section(8) .BTF.ext, size 80, link 0, flags 0, type=1 libbpf: section(9) .rel.BTF.ext, size 32, link 14, flags 0, type=9 libbpf: skip relo .rel.BTF.ext(9) for section(8) libbpf: section(10) .debug_frame, size 40, link 0, flags 0, type=1 libbpf: skip section(10) .debug_frame libbpf: section(11) .rel.debug_frame, size 16, link 14, flags 0, type=9 libbpf: skip relo .rel.debug_frame(11) for section(10) libbpf: section(12) .debug_line, size 74, link 0, flags 0, type=1 libbpf: skip section(12) .debug_line libbpf: section(13) .rel.debug_line, size 16, link 14, flags 0, type=9 libbpf: skip relo .rel.debug_line(13) for section(12) libbpf: section(14) .symtab, size 96, link 1, flags 0, type=2 libbpf: looking for externs among 4 symbols... libbpf: collected 0 externs total libbpf: failed to guess program type from ELF section '.text' libbpf: supported section(type) names are: socket sk_reuseport kprobe/ [...] After: # bpftool prog load sample_ret0.o /sys/fs/bpf/sample_ret0 libbpf: failed to guess program type from ELF section '.text' libbpf: supported section(type) names are: socket sk_reuseport kprobe/ [...] Signed-off-by:
John Fastabend <john.fastabend@gmail.com> Link: https://lore.kernel.org/bpf/20200311021205.9755-1-quentin@isovalent.comSigned-off-by:
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Jiri Olsa authored
Adding name to 'struct bpf_ksym' object to carry the name of the symbol for bpf_prog, bpf_trampoline, bpf_dispatcher objects. The current benefit is that name is now generated only when the symbol is added to the list, so we don't need to generate it every time it's accessed. The future benefit is that we will have all the bpf objects symbols represented by struct bpf_ksym. Signed-off-by:
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Jiri Olsa authored
Adding 'struct bpf_ksym' object that will carry the kallsym information for bpf symbol. Adding the start and end address to begin with. It will be used by bpf_prog, bpf_trampoline, bpf_dispatcher objects. The symbol_start/symbol_end values were originally used to sort bpf_prog objects. For the address displayed in /proc/kallsyms we are using prog->bpf_func value. I'm using the bpf_func value for program symbol start instead of the symbol_start, because it makes no difference for sorting bpf_prog objects and we can use it directly as an address to display it in /proc/kallsyms. Signed-off-by:
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Björn Töpel authored
Adding bpf_trampoline_ name prefix for DECLARE_BPF_DISPATCHER, so all the dispatchers have the common name prefix. And also a small '_' cleanup for bpf_dispatcher_nopfunc function name. Signed-off-by:
Björn Töpel <bjorn.topel@intel.com> Signed-off-by:
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Jiri Olsa authored
The kbuild test robot reported compile issue on x86 in one of the following patches that adds <linux/kallsyms.h> include into <linux/bpf.h>, which is picked up by init_32.c object. The problem is that <linux/kallsyms.h> defines global function is_kernel_text which colides with the static function of the same name defined in init_32.c: $ make ARCH=i386 ... >> arch/x86/mm/init_32.c:241:19: error: redefinition of 'is_kernel_text' static inline int is_kernel_text(unsigned long addr) ^~~~~~~~~~~~~~ In file included from include/linux/bpf.h:21:0, from include/linux/bpf-cgroup.h:5, from include/linux/cgroup-defs.h:22, from include/linux/cgroup.h:28, from include/linux/hugetlb.h:9, from arch/x86/mm/init_32.c:18: include/linux/kallsyms.h:31:19: note: previous definition of 'is_kernel_text' was here static inline int is_kernel_text(unsigned long addr) Renaming the init_32.c is_kernel_text function to __is_kernel_text. Reported-by:kbuild test robot <lkp@intel.com> Signed-off-by:
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Eelco Chaudron authored
Introduce new helper that reuses existing xdp perf_event output implementation, but can be called from raw_tracepoint programs that receive 'struct xdp_buff *' as a tracepoint argument. Signed-off-by:
Eelco Chaudron <echaudro@redhat.com> Signed-off-by:
Toke Høiland-Jørgensen <toke@redhat.com> Link: https://lore.kernel.org/bpf/158348514556.2239.11050972434793741444.stgit@xdp-tutorial
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Alexei Starovoitov authored
Carlos Neira says: ==================== Currently bpf_get_current_pid_tgid(), is used to do pid filtering in bcc's scripts but this helper returns the pid as seen by the root namespace which is fine when a bcc script is not executed inside a container. When the process of interest is inside a container, pid filtering will not work if bpf_get_current_pid_tgid() is used. This helper addresses this limitation returning the pid as it's seen by the current namespace where the script is executing. In the future different pid_ns files may belong to different devices, according to the discussion between Eric Biederman and Yonghong in 2017 Linux plumbers conference. To address that situation the helper requires inum and dev_t from /proc/self/ns/pid. This helper has the same use cases as bpf_get_current_pid_tgid() as it can be used to do pid filtering even inside a container. ==================== Signed-off-by: -
Carlos Neira authored
Self tests added for new helper bpf_get_ns_current_pid_tgid Signed-off-by:
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Carlos Neira authored
New bpf helper bpf_get_ns_current_pid_tgid, This helper will return pid and tgid from current task which namespace matches dev_t and inode number provided, this will allows us to instrument a process inside a container. Signed-off-by:
Yonghong Song <yhs@fb.com> Link: https://lore.kernel.org/bpf/20200304204157.58695-3-cneirabustos@gmail.com
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Carlos Neira authored
ns_match returns true if the namespace inode and dev_t matches the ones provided by the caller. Signed-off-by:
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- 12 Mar, 2020 7 commits
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Quentin Monnet authored
Minor fixes for bash completion: addition of program name completion for two subcommands, and correction for program test-runs and map pinning. The completion for the following commands is fixed or improved: # bpftool prog run [TAB] # bpftool prog pin [TAB] # bpftool map pin [TAB] # bpftool net attach xdp name [TAB] Signed-off-by: -
Quentin Monnet authored
Documentation and interactive help for bpftool have always explained that the regular handles for programs (id|name|tag|pinned) and maps (id|name|pinned) can be passed to the utility when attempting to pin objects (bpftool prog pin PROG / bpftool map pin MAP). THIS IS A LIE!! The tool actually accepts only ids, as the parsing is done in do_pin_any() in common.c instead of reusing the parsing functions that have long been generic for program and map handles. Instead of fixing the doc, fix the code. It is trivial to reuse the generic parsing, and to simplify do_pin_any() in the process. Do not accept to pin multiple objects at the same time with prog_parse_fds() or map_parse_fds() (this would require a more complex syntax for passing multiple sysfs paths and validating that they correspond to the number of e.g. programs we find for a given name or tag). Signed-off-by:
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Andrii Nakryiko authored
Needs for application BTF being present differs between user-space libbpf needs and kernel needs. Currently, BTF is mandatory only in kernel only when BPF application is using STRUCT_OPS. While libbpf itself relies more heavily on presense of BTF: - for BTF-defined maps; - for Kconfig externs; - for STRUCT_OPS as well. Thus, checks for presence and validness of bpf_object's BPF needs to be performed separately, which is patch does. Fixes: 53276446 ("libbpf: Relax check whether BTF is mandatory") Reported-by:
Michal Rostecki <mrostecki@opensuse.org> Signed-off-by:
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Song Liu authored
These files are generated, so ignore them. Signed-off-by:
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Song Liu authored
Add the dependency to libbpf, to fix build errors like: In file included from skeleton/profiler.bpf.c:5: .../bpf_helpers.h:5:10: fatal error: 'bpf_helper_defs.h' file not found #include "bpf_helper_defs.h" ^~~~~~~~~~~~~~~~~~~ 1 error generated. make: *** [skeleton/profiler.bpf.o] Error 1 make: *** Waiting for unfinished jobs.... Fixes: 47c09d6a ("bpftool: Introduce "prog profile" command") Suggested-by: -
Song Liu authored
bpftool-prog-profile requires clang to generate BTF for global variables. When compared with older clang, skip this command. This is achieved by adding a new feature, clang-bpf-global-var, to tools/build/feature. Signed-off-by:
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Tobias Klauser authored
When compiling bpftool on a system where the /usr/include/asm symlink doesn't exist (e.g. on an Ubuntu system without gcc-multilib installed), the build fails with: CLANG skeleton/profiler.bpf.o In file included from skeleton/profiler.bpf.c:4: In file included from /usr/include/linux/bpf.h:11: /usr/include/linux/types.h:5:10: fatal error: 'asm/types.h' file not found #include <asm/types.h> ^~~~~~~~~~~~~ 1 error generated. make: *** [Makefile:123: skeleton/profiler.bpf.o] Error 1 This indicates that the build is using linux/types.h from system headers instead of source tree headers. To fix this, adjust the clang search path to include the necessary headers from tools/testing/selftests/bpf/include/uapi and tools/include/uapi. Also use __bitwise__ instead of __bitwise in skeleton/profiler.h to avoid clashing with the definition in tools/testing/selftests/bpf/include/uapi/linux/types.h. Signed-off-by:
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- 11 Mar, 2020 2 commits
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Andrii Nakryiko authored
Libbpf compiles and runs subset of selftests on each PR in its Github mirror repository. To allow still building up-to-date selftests against outdated kernel images, add back BPF_F_CURRENT_CPU definitions back. N.B. BCC's runqslower version ([0]) doesn't need BPF_F_CURRENT_CPU due to use of locally checked in vmlinux.h, generated against kernel with 1aae4bdd ("bpf: Switch BPF UAPI #define constants used from BPF program side to enums") applied. [0] https://github.com/iovisor/bcc/pull/2809 Fixes: 367d82f1 (" tools/runqslower: Drop copy/pasted BPF_F_CURRENT_CPU definiton") Signed-off-by:
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Alexei Starovoitov authored
fmod_ret progs are emitted as: start = __bpf_prog_enter(); call fmod_ret *(u64 *)(rbp - 8) = rax __bpf_prog_exit(, start); test eax, eax jne do_fexit That 'test eax, eax' is working by accident. The compiler is free to use rax inside __bpf_prog_exit() or inside functions that __bpf_prog_exit() is calling. Which caused "test_progs -t modify_return" to sporadically fail depending on compiler version and kconfig. Fix it by using 'cmp [rbp - 8], 0' instead of 'test eax, eax'. Fixes: ae240823 ("bpf: Introduce BPF_MODIFY_RETURN") Reported-by:
KP Singh <kpsingh@google.com> Link: https://lore.kernel.org/bpf/20200311003906.3643037-1-ast@kernel.org
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