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Will be used together with BPF_MAP_TYPE_PROG_ARRAY in
tools/perf/examples/bpf/augmented_raw_syscalls.c.
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Luis Cláudio Gonçalves <lclaudio@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-pd1bpy8i31nta6jqwdex871g@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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The libbpf loader expects that some __btf_map_<MAP_NAME> structs be in
place with the keys and values types of maps so that one can store the
struct definitions and have them sent to the kernel via sys_bpf(fd, cmd
= BTF_LOAD) and then later be retrievable via sys_bpf(fd, cmd =
BPF_OBJ_GET_INFO_BY_FD) for use by tools such as 'bpftool map dump id
MAP_ID'.
Since we already have this for defining maps in 'perf trace' BPF events:
bpf_map(name, _type, type_key, type_val, _max_entries)
As used in the tools/perf/examples/bpf/augmented_raw_syscalls.c:
--- 8< ---
struct syscall {
bool enabled;
};
bpf_map(syscalls, ARRAY, int, struct syscall, 512);
--- 8< ---
All we need is to get all that already available info, piggyback on the
'bpf_map' define in tools/perf/include/bpf/bpf.h, that is included by
'perf trace' BPF programs and do that without requiring changes to the
BPF programs already defining maps using 'bpf_map()'.
So this is what we have before this patch:
1) With this in ~/.perfconfig to dump .c events as .o, aka save a copy
so that we can use the .o later as a pre-compiled BPF bytecode:
# grep '\[llvm\]' -A2 ~/.perfconfig
[llvm]
dump-obj = true
clang-opt = -g
#
# clang --version
clang version 9.0.0 (https://git.llvm.org/git/clang.git/ 7906282d3afec5dfdc2b27943fd6c0309086c507) (https://git.llvm.org/git/llvm.git/ a1b5de1ff8ae8bc79dc8e86e1f82565229bd0500)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /opt/llvm/bin
2) Note the -g there so that we get clang to generate debuginfo, and
since the target is 'bpf' it will generate the BTF info in this
clang version (9.0).
3) Run a simple 'perf record' specifiying as an event the augmented_raw_syscalls.c
source code:
# perf record -e /home/acme/git/perf/tools/perf/examples/bpf/augmented_raw_syscalls.c sleep 1
LLVM: dumping /home/acme/git/perf/tools/perf/examples/bpf/augmented_raw_syscalls.o
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.025 MB perf.data ]
# file /home/acme/git/perf/tools/perf/examples/bpf/augmented_raw_syscalls.o
/home/acme/git/perf/tools/perf/examples/bpf/augmented_raw_syscalls.o: ELF 64-bit LSB relocatable, eBPF, version 1 (SYSV), with debug_info, not stripped
4) Look at the BTF structs encoded in it:
# pahole -F btf --sizes /home/acme/git/perf/tools/perf/examples/bpf/augmented_raw_syscalls.o
syscall_enter_args 64 0
augmented_filename 264 0
syscall 1 0
syscall_exit_args 24 0
bpf_map 28 0
#
# pahole -F btf -C syscalls /home/acme/git/perf/tools/perf/examples/bpf/augmented_raw_syscalls.o
# pahole -F btf -C syscall /home/acme/git/perf/tools/perf/examples/bpf/augmented_raw_syscalls.o
struct syscall {
bool enabled; /* 0 1 */
/* size: 1, cachelines: 1, members: 1 */
/* last cacheline: 1 bytes */
};
#
5) Ok, with just this we don't have the markers expected by the libbpf
loader and when we run with this BPF bytecode, because we have:
# grep '\[trace\]' -A1 ~/.perfconfig
[trace]
add_events = /home/acme/git/perf/tools/perf/examples/bpf/augmented_raw_syscalls.o
#
6) Lets do a 'perf trace' system wide session using this BPF program:
# perf trace -e *mmsg,open*
Cache2 I/O/6885 openat(AT_FDCWD, "/home/acme/.cache/mozilla/firefox/ina67tev.default/cache2/entries/BA220AB2914006A7AE96D27BE6EA13DD77519FCA", O_RDWR|O_CREAT|O_TRUNC, S_IRUSR|S_IWUSR) = 106
Cache2 I/O/6885 openat(AT_FDCWD, "/proc/self/mountinfo", O_RDONLY) = 121
Cache2 I/O/6885 openat(AT_FDCWD, "/proc/self/mountinfo", O_RDONLY) = 121
Cache2 I/O/6885 openat(AT_FDCWD, "/proc/self/mountinfo", O_RDONLY) = 121
Cache2 I/O/6885 openat(AT_FDCWD, "/proc/self/mountinfo", O_RDONLY) = 121
DNS Res~ver #3/23340 openat(AT_FDCWD, "/etc/hosts", O_RDONLY|O_CLOEXEC) = 106
DNS Res~ver #3/23340 sendmmsg(106<socket:[3482690]>, 0x7f252f1fcaf0, 2, MSG_NOSIGNAL) = 2
Cache2 I/O/6885 openat(AT_FDCWD, "/home/acme/.cache/mozilla/firefox/ina67tev.default/cache2/entries/BA220AB2914006A7AE96D27BE6EA13DD77519FCA", O_RDWR) = 106
lighttpd/18915 openat(AT_FDCWD, "/proc/loadavg", O_RDONLY) = 12
7) While it runs lets see the maps that 'perf trace' + libbpf's BPF
loader loaded into the kernel via sys_bpf(fd, BPF_BTF_LOAD, ...):
# bpftool map list | tail -6
149: perf_event_array name __augmented_sys flags 0x0
key 4B value 4B max_entries 8 memlock 4096B
150: array name syscalls flags 0x0
key 4B value 1B max_entries 512 memlock 8192B
151: hash name pids_filtered flags 0x0
key 4B value 1B max_entries 64 memlock 8192B
#
8) Dump the "pids_filtered", map, that will have one entry per PID that
'perf trace' wants filtered, which includes its own, to avoid a
tracing feedback loop (perf trace shows the syscalls it does which
generates more syscalls that it has to show that...), it also
auto-filters the 'gnome-terminal' and 'sshd' parent PIDs, for the
same reason:
# bpftool map dump id 151
key: a5 0c 00 00 value: 01
key: 14 63 00 00 value: 01
Found 2 elements
#
9) Since there is no BTF info available, it does a generic hex dump :-\
10) Now, with this patch applied, we'll do steps 3 to 6 again and look
with pahole if there are extra structs encoded in BTF:
# pahole -F btf --sizes /home/acme/git/perf/tools/perf/examples/bpf/augmented_raw_syscalls.o
syscall_enter_args 64 0
augmented_filename 264 0
syscall 1 0
syscall_exit_args 24 0
bpf_map 28 0
____btf_map___augmented_syscalls__ 8 0
____btf_map_syscalls 8 0
____btf_map_pids_filtered 8 0
#
11) Yes, those __btf_map_ + the map names, lets see how they look like:
# pahole -F btf -C ____btf_map_syscalls /home/acme/git/perf/tools/perf/examples/bpf/augmented_raw_syscalls.o
struct ____btf_map_syscalls {
int key; /* 0 4 */
struct syscall value; /* 4 1 */
/* size: 8, cachelines: 1, members: 2 */
/* padding: 3 */
/* last cacheline: 8 bytes */
};
#
12) Lets repeat step 7 to get the new map ids:
# bpftool map list | tail -6
155: perf_event_array name __augmented_sys flags 0x0
key 4B value 4B max_entries 8 memlock 4096B
156: array name syscalls flags 0x0
key 4B value 1B max_entries 512 memlock 8192B
157: hash name pids_filtered flags 0x0
key 4B value 1B max_entries 64 memlock 8192B
#
13) And finally lets dump the 'pids_filtered':
# bpftool map dump id 157
[{
"key": 3237,
"value": true
},{
"key": 26435,
"value": true
}
]
#
Looks much better! BTF info was used to interpret the key as an integer
and the value as a struct with just one boolean member, so to make it
more compact, show just the 'true' value where we saw '01'.
Now to make 'perf trace --dump-map' to use BTF!
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexei Starovoitov <ast@fb.com>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Luis Cláudio Gonçalves <lclaudio@redhat.com>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Wang Nan <wangnan0@huawei.com>
Cc: Yonghong Song <yhs@fb.com>
Link: https://lkml.kernel.org/n/tip-ybuf9wpkm30xk28iq7jbwb40@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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First user, pid_t as the type, lets see how this goes with the BTF
routines.
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Luis Cláudio Gonçalves <lclaudio@redhat.com>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Cc: Yonghong Song <yhs@fb.com>
Link: https://lkml.kernel.org/n/tip-56eplvf86r69wt3p35nh805z@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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To make the declaration of maps more compact, the following patches will
make use of it.
Standardizing on it will allow to add the BTF details, i.e.
BPF_ANNOTATE_KV_PAIR() (tools/testing/selftests/bpf/bpf_helpers.h)
transparently.
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Luis Cláudio Gonçalves <lclaudio@redhat.com>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Cc: Yonghong Song <yhs@fb.com>
Link: https://lkml.kernel.org/n/tip-h3q9rxxkbzetgnbro5rclqft@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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So that we don't always carry that __bpf_output__ map, leaving that to
the scripts wanting to use that facility.
'perf trace' will be changed to look if that map is present and only
setup the bpf-output events if so.
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-azwys8irxqx9053vpajr0k5h@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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While working on augmented syscalls I got into this error:
# trace -vv --filter-pids 2469,1663 -e tools/perf/examples/bpf/augmented_raw_syscalls.c sleep 1
<SNIP>
libbpf: map 0 is "__augmented_syscalls__"
libbpf: map 1 is "__bpf_stdout__"
libbpf: map 2 is "pids_filtered"
libbpf: map 3 is "syscalls"
libbpf: collecting relocating info for: '.text'
libbpf: relo for 13 value 84 name 133
libbpf: relocation: insn_idx=3
libbpf: relocation: find map 3 (pids_filtered) for insn 3
libbpf: collecting relocating info for: 'raw_syscalls:sys_enter'
libbpf: relo for 8 value 0 name 0
libbpf: relocation: insn_idx=1
libbpf: relo for 8 value 0 name 0
libbpf: relocation: insn_idx=3
libbpf: relo for 9 value 28 name 178
libbpf: relocation: insn_idx=36
libbpf: relocation: find map 1 (__augmented_syscalls__) for insn 36
libbpf: collecting relocating info for: 'raw_syscalls:sys_exit'
libbpf: relo for 8 value 0 name 0
libbpf: relocation: insn_idx=0
libbpf: relo for 8 value 0 name 0
libbpf: relocation: insn_idx=2
bpf: config program 'raw_syscalls:sys_enter'
bpf: config program 'raw_syscalls:sys_exit'
libbpf: create map __bpf_stdout__: fd=3
libbpf: create map __augmented_syscalls__: fd=4
libbpf: create map syscalls: fd=5
libbpf: create map pids_filtered: fd=6
libbpf: added 13 insn from .text to prog raw_syscalls:sys_enter
libbpf: added 13 insn from .text to prog raw_syscalls:sys_exit
libbpf: load bpf program failed: Operation not permitted
libbpf: failed to load program 'raw_syscalls:sys_exit'
libbpf: failed to load object 'tools/perf/examples/bpf/augmented_raw_syscalls.c'
bpf: load objects failed: err=-4009: (Incorrect kernel version)
event syntax error: 'tools/perf/examples/bpf/augmented_raw_syscalls.c'
\___ Failed to load program for unknown reason
(add -v to see detail)
Run 'perf list' for a list of valid events
Usage: perf trace [<options>] [<command>]
or: perf trace [<options>] -- <command> [<options>]
or: perf trace record [<options>] [<command>]
or: perf trace record [<options>] -- <command> [<options>]
-e, --event <event> event/syscall selector. use 'perf list' to list available events
If I then try to use strace (perf trace'ing 'perf trace' needs some more work
before its possible) to get a bit more info I get:
# strace -e bpf trace --filter-pids 2469,1663 -e tools/perf/examples/bpf/augmented_raw_syscalls.c sleep 1
bpf(BPF_MAP_CREATE, {map_type=BPF_MAP_TYPE_PERF_EVENT_ARRAY, key_size=4, value_size=4, max_entries=4, map_flags=0, inner_map_fd=0, map_name="__bpf_stdout__", map_ifindex=0}, 72) = 3
bpf(BPF_MAP_CREATE, {map_type=BPF_MAP_TYPE_PERF_EVENT_ARRAY, key_size=4, value_size=4, max_entries=4, map_flags=0, inner_map_fd=0, map_name="__augmented_sys", map_ifindex=0}, 72) = 4
bpf(BPF_MAP_CREATE, {map_type=BPF_MAP_TYPE_ARRAY, key_size=4, value_size=1, max_entries=500, map_flags=0, inner_map_fd=0, map_name="syscalls", map_ifindex=0}, 72) = 5
bpf(BPF_MAP_CREATE, {map_type=BPF_MAP_TYPE_HASH, key_size=4, value_size=1, max_entries=512, map_flags=0, inner_map_fd=0, map_name="pids_filtered", map_ifindex=0}, 72) = 6
bpf(BPF_PROG_LOAD, {prog_type=BPF_PROG_TYPE_TRACEPOINT, insn_cnt=57, insns=0x1223f50, license="GPL", log_level=0, log_size=0, log_buf=NULL, kern_version=KERNEL_VERSION(4, 18, 10), prog_flags=0, prog_name="sys_enter", prog_ifindex=0, expected_attach_type=BPF_CGROUP_INET_INGRESS}, 72) = 7
bpf(BPF_PROG_LOAD, {prog_type=BPF_PROG_TYPE_TRACEPOINT, insn_cnt=18, insns=0x1224120, license="GPL", log_level=0, log_size=0, log_buf=NULL, kern_version=KERNEL_VERSION(4, 18, 10), prog_flags=0, prog_name="sys_exit", prog_ifindex=0, expected_attach_type=BPF_CGROUP_INET_INGRESS}, 72) = -1 EPERM (Operation not permitted)
bpf(BPF_PROG_LOAD, {prog_type=BPF_PROG_TYPE_TRACEPOINT, insn_cnt=18, insns=0x1224120, license="GPL", log_level=1, log_size=262144, log_buf="", kern_version=KERNEL_VERSION(4, 18, 10), prog_flags=0, prog_name="sys_exit", prog_ifindex=0, expected_attach_type=BPF_CGROUP_INET_INGRESS}, 72) = -1 EPERM (Operation not permitted)
bpf(BPF_PROG_LOAD, {prog_type=BPF_PROG_TYPE_KPROBE, insn_cnt=18, insns=0x1224120, license="GPL", log_level=0, log_size=0, log_buf=NULL, kern_version=KERNEL_VERSION(4, 18, 10), prog_flags=0, prog_name="sys_exit", prog_ifindex=0, expected_attach_type=BPF_CGROUP_INET_INGRESS}, 72) = -1 EPERM (Operation not permitted)
event syntax error: 'tools/perf/examples/bpf/augmented_raw_syscalls.c'
\___ Failed to load program for unknown reason
<SNIP similar output as without 'strace'>
#
I managed to create the maps, etc, but then installing the "sys_exit" hook into
the "raw_syscalls:sys_exit" tracepoint somehow gets -EPERMed...
I then go and try reducing the size of this new table:
+++ b/tools/perf/examples/bpf/augmented_raw_syscalls.c
@@ -47,6 +47,17 @@ struct augmented_filename {
#define SYS_OPEN 2
#define SYS_OPENAT 257
+struct syscall {
+ bool filtered;
+};
+
+struct bpf_map SEC("maps") syscalls = {
+ .type = BPF_MAP_TYPE_ARRAY,
+ .key_size = sizeof(int),
+ .value_size = sizeof(struct syscall),
+ .max_entries = 500,
+};
And after reducing that .max_entries a tad, it works. So yeah, the "unknown
reason" should be related to the number of bytes all this is taking, reduce the
default for pid_map()s so that we can have a "syscalls" map with enough slots
for all syscalls in most arches. And take notes about this error message,
improve it :-)
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: David Ahern <dsahern@gmail.com>
Cc: Edward Cree <ecree@solarflare.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Cc: Yonghong Song <yhs@fb.com>
Link: https://lkml.kernel.org/n/tip-yjzhak8asumz9e9hts2dgplp@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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Will be used in the augmented_raw_syscalls.c to implement 'perf trace
--filter-pids'.
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-9sybmz4vchlbpqwx2am13h9e@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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Starting with a helper for a basic pid_map(), a hash using a pid as a
key.
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-gdwvq53wltvq6b3g5tdmh0cw@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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Start with a getpid() function wrapping BPF_FUNC_get_current_pid_tgid,
idea is to mimic the system headers.
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-zo8hv22onidep7tm785dzxfk@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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So that we can hook to the syscalls:sys_exit_SYSCALL tracepoints in
addition to the syscalls:sys_enter_SYSCALL we hook using the
syscall_enter() helper.
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-6qh8aph1jklyvdu7w89c0izc@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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So that we don't have to define sockaddr_storage in the
augmented_syscalls.c bpf example when hooking into syscalls needing it,
idea is to mimic the system headers. Eventually we probably need to have
sys/socket.h, etc. Start by having at least linux/socket.h.
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-yhzarcvsjue8pgpvkjhqgioc@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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Will be used shortly in the augmented syscalls work together with a
PERF_COUNT_SW_BPF_OUTPUT software event to insert syscalls + pointer
contents in the perf ring buffer, to be consumed by 'perf trace'
beautifiers.
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-ajlkpz4cd688ulx1u30htkj3@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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That, together with the map __bpf_output__ that is already handled by
'perf trace' to print that event's contents as strings provides a
debugging facility, to show it in use, print a simple string everytime
the syscalls:sys_enter_openat() syscall tracepoint is hit:
# cat tools/perf/examples/bpf/hello.c
#include <stdio.h>
int syscall_enter(openat)(void *args)
{
puts("Hello, world\n");
return 0;
}
license(GPL);
#
# perf trace -e openat,tools/perf/examples/bpf/hello.c cat /etc/passwd > /dev/null
0.016 ( ): __bpf_stdout__:Hello, world
0.018 ( 0.010 ms): cat/9079 openat(dfd: CWD, filename: /etc/ld.so.cache, flags: CLOEXEC) = 3
0.057 ( ): __bpf_stdout__:Hello, world
0.059 ( 0.011 ms): cat/9079 openat(dfd: CWD, filename: /lib64/libc.so.6, flags: CLOEXEC) = 3
0.417 ( ): __bpf_stdout__:Hello, world
0.419 ( 0.009 ms): cat/9079 openat(dfd: CWD, filename: /etc/passwd) = 3
#
This is part of an ongoing experimentation on making eBPF scripts as
consumed by perf to be as concise as possible and using familiar
concepts such as stdio.h functions, that end up just wrapping the
existing BPF functions, trying to hide as much boilerplate as possible
while using just conventions and C preprocessor tricks.
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-4tiaqlx5crf0fwpe7a6j84x7@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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A helper structure used by eBPF C program to describe map attributes to
elf_bpf loader, to be used initially by the special __bpf_stdout__ map
used to print strings into the perf ring buffer in BPF scripts, e.g.:
Using the upcoming stdio.h and puts() macros to use the __bpf_stdout__
map to add strings to the ring buffer:
# cat tools/perf/examples/bpf/hello.c
#include <stdio.h>
int syscall_enter(openat)(void *args)
{
puts("Hello, world\n");
return 0;
}
license(GPL);
#
# cat ~/.perfconfig
[llvm]
dump-obj = true
# perf trace -e openat,tools/perf/examples/bpf/hello.c/call-graph=dwarf/ cat /etc/passwd > /dev/null
LLVM: dumping tools/perf/examples/bpf/hello.o
0.016 ( ): __bpf_stdout__:Hello, world
0.018 ( 0.010 ms): cat/9079 openat(dfd: CWD, filename: /etc/ld.so.cache, flags: CLOEXEC ) = 3
0.057 ( ): __bpf_stdout__:Hello, world
0.059 ( 0.011 ms): cat/9079 openat(dfd: CWD, filename: /lib64/libc.so.6, flags: CLOEXEC ) = 3
0.417 ( ): __bpf_stdout__:Hello, world
0.419 ( 0.009 ms): cat/9079 openat(dfd: CWD, filename: /etc/passwd ) = 3
#
# file tools/perf/examples/bpf/hello.o
tools/perf/examples/bpf/hello.o: ELF 64-bit LSB relocatable, *unknown arch 0xf7* version 1 (SYSV), not stripped
# readelf -SW tools/perf/examples/bpf/hello.o
There are 10 section headers, starting at offset 0x208:
Section Headers:
[Nr] Name Type Address Off Size ES Flg Lk Inf Al
[ 0] NULL 0000000000000000 000000 000000 00 0 0 0
[ 1] .strtab STRTAB 0000000000000000 000188 00007f 00 0 0 1
[ 2] .text PROGBITS 0000000000000000 000040 000000 00 AX 0 0 4
[ 3] syscalls:sys_enter_openat PROGBITS 0000000000000000 000040 000088 00 AX 0 0 8
[ 4] .relsyscalls:sys_enter_openat REL 0000000000000000 000178 000010 10 9 3 8
[ 5] maps PROGBITS 0000000000000000 0000c8 00001c 00 WA 0 0 4
[ 6] .rodata.str1.1 PROGBITS 0000000000000000 0000e4 00000e 01 AMS 0 0 1
[ 7] license PROGBITS 0000000000000000 0000f2 000004 00 WA 0 0 1
[ 8] version PROGBITS 0000000000000000 0000f8 000004 00 WA 0 0 4
[ 9] .symtab SYMTAB 0000000000000000 000100 000078 18 1 1 8
Key to Flags:
W (write), A (alloc), X (execute), M (merge), S (strings), I (info),
L (link order), O (extra OS processing required), G (group), T (TLS),
C (compressed), x (unknown), o (OS specific), E (exclude),
p (processor specific)
# readelf -s tools/perf/examples/bpf/hello.o
Symbol table '.symtab' contains 5 entries:
Num: Value Size Type Bind Vis Ndx Name
0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
1: 0000000000000000 0 NOTYPE GLOBAL DEFAULT 5 __bpf_stdout__
2: 0000000000000000 0 NOTYPE GLOBAL DEFAULT 7 _license
3: 0000000000000000 0 NOTYPE GLOBAL DEFAULT 8 _version
4: 0000000000000000 0 NOTYPE GLOBAL DEFAULT 3 syscall_enter_openat
#
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-81fg60om2ifnatsybzwmiga3@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
|
|
Allowing one to hook into the syscalls:sys_enter_NAME tracepoints,
an example is provided that hooks into the 'openat' syscall.
Using it with the probe:vfs_getname probe into getname_flags to get the
filename args as it is copied from userspace:
# perf probe -l
probe:vfs_getname (on getname_flags:73@acme/git/linux/fs/namei.c with pathname)
# perf trace -e probe:*getname,tools/perf/examples/bpf/sys_enter_openat.c cat /etc/passwd > /dev/null
0.000 probe:vfs_getname:(ffffffffbd2a8983) pathname="/etc/ld.so.preload"
0.022 syscalls:sys_enter_openat:dfd: CWD, filename: 0xafbe8da8, flags: CLOEXEC
0.027 probe:vfs_getname:(ffffffffbd2a8983) pathname="/etc/ld.so.cache"
0.054 syscalls:sys_enter_openat:dfd: CWD, filename: 0xafdf0ce0, flags: CLOEXEC
0.057 probe:vfs_getname:(ffffffffbd2a8983) pathname="/lib64/libc.so.6"
0.316 probe:vfs_getname:(ffffffffbd2a8983) pathname="/usr/lib/locale/locale-archive"
0.375 syscalls:sys_enter_openat:dfd: CWD, filename: 0xe2b2b0b4
0.379 probe:vfs_getname:(ffffffffbd2a8983) pathname="/etc/passwd"
#
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-2po9jcqv1qgj0koxlg8kkg30@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
|
|
The next example scripts need the definition for the BPF functions, i.e.
things like BPF_FUNC_probe_read, and in time will require lots of other
definitions found in uapi/linux/bpf.h, so include it from the bpf.h file
included from the eBPF scripts build with clang via '-e bpf_script.c'
like in this example:
$ tail -8 tools/perf/examples/bpf/5sec.c
#include <bpf.h>
int probe(hrtimer_nanosleep, rqtp->tv_sec)(void *ctx, int err, long sec)
{
return sec == 5;
}
license(GPL);
$
That 'bpf.h' include in the 5sec.c eBPF example will come from a set of
header files crafted for building eBPF objects, that in a end-user
system will come from:
/usr/lib/perf/include/bpf/bpf.h
And will include <uapi/linux/bpf.h> either from the place where the
kernel was built, or from a kernel-devel rpm package like:
-working-directory /lib/modules/4.17.9-100.fc27.x86_64/build
That is set up by tools/perf/util/llvm-utils.c, and can be overriden
by setting the 'kbuild-dir' variable in the "llvm" ~/.perfconfig file,
like:
# cat ~/.perfconfig
[llvm]
kbuild-dir = /home/foo/git/build/linux
This usually doesn't need any change, just documenting here my findings
while working with this code.
In the future we may want to instead just use what is in
/usr/include/linux/bpf.h, that comes from the UAPI provided from the
kernel sources, for now, to avoid getting the kernel's non-UAPI
"linux/bpf.h" file, that will cause clang to fail and is not what we
want anyway (no BPF function definitions, etc), do it explicitely by
asking for "uapi/linux/bpf.h".
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-zd8zeyhr2sappevojdem9xxt@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
|
|
So that kprobe definitions become:
int probe(function, variables)(void *ctx, int err, var1, var2, ...)
The existing 5sec.c, got converted and goes from:
SEC("func=hrtimer_nanosleep rqtp->tv_sec")
int func(void *ctx, int err, long sec)
{
}
To:
int probe(hrtimer_nanosleep, rqtp->tv_sec)(void *ctx, int err, long sec)
{
}
If we decide to add tv_nsec as well, then it becomes:
$ cat tools/perf/examples/bpf/5sec.c
#include <bpf.h>
int probe(hrtimer_nanosleep, rqtp->tv_sec rqtp->tv_nsec)(void *ctx, int err, long sec, long nsec)
{
return sec == 5;
}
license(GPL);
$
And if we run it, system wide as before and run some 'sleep' with values
for the tv_nsec field, we get:
# perf trace --no-syscalls -e tools/perf/examples/bpf/5sec.c
0.000 perf_bpf_probe:hrtimer_nanosleep:(ffffffff9811b5f0) tv_sec=5 tv_nsec=100000000
9641.650 perf_bpf_probe:hrtimer_nanosleep:(ffffffff9811b5f0) tv_sec=5 tv_nsec=123450001
^C#
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-1v9r8f6ds5av0w9pcwpeknyl@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
|
|
To further reduce boilerplate.
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-vst6hj335s0ebxzqltes3nsc@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
|
|
So, the first helper is the one shortening a variable/function section
attribute, from, for instance:
char _license[] __attribute__((section("license"), used)) = "GPL";
to:
char _license[] SEC("license") = "GPL";
Convert empty.c to that and it becomes:
# cat ~acme/lib/examples/perf/bpf/empty.c
#include <bpf.h>
char _license[] SEC("license") = "GPL";
int _version SEC("version") = LINUX_VERSION_CODE;
#
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-zmeg52dlvy51rdlhyumfl5yf@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
|
Arnaldo Carvalho de Melo