kernel/linux.git/tools/lib/bpf/libbpf.c, branch v5.3.1

libbpf: set BTF FD for prog only when there is supported .BTF.ext data

2019-08-01T20:10:45+00:00

5d01ab7bac46 ("libbpf: fix erroneous multi-closing of BTF FD") introduced backwards-compatibility issue, manifesting itself as -E2BIG error returned on program load due to unknown non-zero btf_fd attribute value for BPF_PROG_LOAD sys_bpf() sub-command. This patch fixes bug by ensuring that we only ever associate BTF FD with program if there is a BTF.ext data that was successfully loaded into kernel, which automatically means kernel supports func_info/line_info and associated BTF FD for progs (checked and ensured also by BTF sanitization code). Fixes: 5d01ab7bac46 ("libbpf: fix erroneous multi-closing of BTF FD") Reported-by: Andrey Ignatov Signed-off-by: Andrii Nakryiko Signed-off-by: Alexei Starovoitov

libbpf : make libbpf_num_possible_cpus function thread safe

2019-08-01T03:35:19+00:00

Having static variable `cpus` in libbpf_num_possible_cpus function without guarding it with mutex makes this function thread-unsafe. If multiple threads accessing this function, in the current form; it leads to incrementing the static variable value `cpus` in the multiple of total available CPUs. Used local stack variable to calculate the number of possible CPUs and then updated the static variable using WRITE_ONCE(). Changes since v1: * added stack variable to calculate cpus * serialized static variable update using WRITE_ONCE() * fixed Fixes tag Fixes: 6446b3155521 ("bpf: add a new API libbpf_num_possible_cpus()") Signed-off-by: Takshak Chahande Acked-by: Andrey Ignatov Reviewed-by: Jakub Kicinski Signed-off-by: Alexei Starovoitov

libbpf: fix erroneous multi-closing of BTF FD

2019-07-27T00:23:16+00:00

Libbpf stores associated BTF FD per each instance of bpf_program. When program is unloaded, that FD is closed. This is wrong, because leads to a race and possibly closing of unrelated files, if application simultaneously opens new files while bpf_programs are unloaded. It's also unnecessary, because struct btf "owns" that FD, and btf__free(), called from bpf_object__close() will close it. Thus the fix is to never have per-program BTF FD and fetch it from obj->btf, when necessary. Fixes: 2993e0515bb4 ("tools/bpf: add support to read .BTF.ext sections") Reported-by: Andrey Ignatov Signed-off-by: Andrii Nakryiko Signed-off-by: Alexei Starovoitov

libbpf: Avoid designated initializers for unnamed union members

2019-07-22T14:14:43+00:00

As it fails to build in some systems with: libbpf.c: In function 'perf_buffer__new': libbpf.c:4515: error: unknown field 'sample_period' specified in initializer libbpf.c:4516: error: unknown field 'wakeup_events' specified in initializer Doing as: attr.sample_period = 1; I.e. not as a designated initializer makes it build everywhere. Cc: Andrii Nakryiko Cc: Adrian Hunter Cc: Daniel Borkmann Cc: Jiri Olsa Cc: Namhyung Kim Fixes: fb84b8224655 ("libbpf: add perf buffer API") Link: https://lkml.kernel.org/n/tip-hnlmch8qit1ieksfppmr32si@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo Acked-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann

libbpf: Fix endianness macro usage for some compilers

2019-07-22T14:14:43+00:00

Using endian.h and its endianness macros makes this code build in a wider range of compilers, as some don't have those macros (__BYTE_ORDER__, __ORDER_LITTLE_ENDIAN__, __ORDER_BIG_ENDIAN__), so use instead endian.h's macros (__BYTE_ORDER, __LITTLE_ENDIAN, __BIG_ENDIAN) which makes this code even shorter :-) Acked-by: Andrii Nakryiko Cc: Adrian Hunter Cc: Alexei Starovoitov Cc: Daniel Borkmann Cc: Jiri Olsa Cc: Namhyung Kim Fixes: 12ef5634a855 ("libbpf: simplify endianness check") Fixes: e6c64855fd7a ("libbpf: add btf__parse_elf API to load .BTF and .BTF.ext") Link: https://lkml.kernel.org/n/tip-eep5n8vgwcdphw3uc058k03u@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: Daniel Borkmann

libbpf: sanitize VAR to conservative 1-byte INT

2019-07-19T19:48:55+00:00

If VAR in non-sanitized BTF was size less than 4, converting such VAR into an INT with size=4 will cause BTF validation failure due to violationg of STRUCT (into which DATASEC was converted) member size. Fix by conservatively using size=1. Signed-off-by: Andrii Nakryiko Signed-off-by: Alexei Starovoitov

libbpf: fix SIGSEGV when BTF loading fails, but .BTF.ext exists

2019-07-19T19:37:18+00:00

In case when BTF loading fails despite sanitization, but BPF object has .BTF.ext loaded as well, we free and null obj->btf, but not obj->btf_ext. This leads to an attempt to relocate .BTF.ext later on during bpf_object__load(), which assumes obj->btf is present. This leads to SIGSEGV on null pointer access. Fix bug by freeing and nulling obj->btf_ext as well. Signed-off-by: Andrii Nakryiko Signed-off-by: Alexei Starovoitov

libbpf: fix ptr to u64 conversion warning on 32-bit platforms

2019-07-12T12:51:03+00:00

On 32-bit platforms compiler complains about conversion: libbpf.c: In function ‘perf_event_open_probe’: libbpf.c:4112:17: error: cast from pointer to integer of different size [-Werror=pointer-to-int-cast] attr.config1 = (uint64_t)(void *)name; /* kprobe_func or uprobe_path */ ^ Reported-by: Matt Hart Fixes: b26500274767 ("libbpf: add kprobe/uprobe attach API") Tested-by: Matt Hart Signed-off-by: Andrii Nakryiko Acked-by: Yonghong Song Signed-off-by: Daniel Borkmann

libbpf: auto-set PERF_EVENT_ARRAY size to number of CPUs

2019-07-08T13:35:43+00:00

For BPF_MAP_TYPE_PERF_EVENT_ARRAY typically correct size is number of possible CPUs. This is impossible to specify at compilation time. This change adds automatic setting of PERF_EVENT_ARRAY size to number of system CPUs, unless non-zero size is specified explicitly. This allows to adjust size for advanced specific cases, while providing convenient and logical defaults. Signed-off-by: Andrii Nakryiko Acked-by: Song Liu Acked-by: Yonghong Song Signed-off-by: Daniel Borkmann

libbpf: add perf buffer API

2019-07-08T13:35:43+00:00

BPF_MAP_TYPE_PERF_EVENT_ARRAY map is often used to send data from BPF program to user space for additional processing. libbpf already has very low-level API to read single CPU perf buffer, bpf_perf_event_read_simple(), but it's hard to use and requires a lot of code to set everything up. This patch adds perf_buffer abstraction on top of it, abstracting setting up and polling per-CPU logic into simple and convenient API, similar to what BCC provides. perf_buffer__new() sets up per-CPU ring buffers and updates corresponding BPF map entries. It accepts two user-provided callbacks: one for handling raw samples and one for get notifications of lost samples due to buffer overflow. perf_buffer__new_raw() is similar, but provides more control over how perf events are set up (by accepting user-provided perf_event_attr), how they are handled (perf_event_header pointer is passed directly to user-provided callback), and on which CPUs ring buffers are created (it's possible to provide a list of CPUs and corresponding map keys to update). This API allows advanced users fuller control. perf_buffer__poll() is used to fetch ring buffer data across all CPUs, utilizing epoll instance. perf_buffer__free() does corresponding clean up and unsets FDs from BPF map. All APIs are not thread-safe. User should ensure proper locking/coordination if used in multi-threaded set up. Signed-off-by: Andrii Nakryiko Acked-by: Yonghong Song Signed-off-by: Daniel Borkmann