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author | Arnaldo Carvalho de Melo <acme@redhat.com> | 2019-03-22 14:48:26 -0300 |
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committer | Arnaldo Carvalho de Melo <acme@redhat.com> | 2019-04-01 14:49:24 -0300 |
commit | 59f3bd7802d3ff7e6ddcce600f361bed288a97dd (patch) | |
tree | 465e6b1536442cf2c0eed50c431639f87e5550cf /tools | |
parent | c52a82f7796306d2d2aafadba47617da619b0918 (diff) | |
download | linux-59f3bd7802d3ff7e6ddcce600f361bed288a97dd.tar.bz2 |
perf augmented_raw_syscalls: Use a PERCPU_ARRAY map to copy more string bytes
The previous method, copying to the BPF stack limited us in how many
bytes we could copy from strings, use a PERCPU_ARRAY map like devised by
the sysdig guys[1] to copy more bytes:
Before:
# trace --no-inherit -e openat touch `python -c "print "$s" 'a' * 2000"`
touch: cannot touch 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa': File name too long
openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
openat(AT_FDCWD, "/lib64/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
openat(AT_FDCWD, "/usr/lib/locale/locale-archive", O_RDONLY|O_CLOEXEC) = 3
openat(AT_FDCWD, "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa", O_CREAT|O_NOCTTY|O_NONBLOCK|O_WRONLY, S_IRUGO|S_IWUGO) = -1 ENAMETOOLONG (File name too long)
openat(AT_FDCWD, "/usr/share/locale/locale.alias", O_RDONLY|O_CLOEXEC) = 3
openat(AT_FDCWD, "/usr/share/locale/en_US.UTF-8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/share/locale/en_US.utf8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
<SNIP some openat calls>
#
After:
[root@quaco acme]# trace --no-inherit -e openat touch `python -c "print "$s" 'a' * 2000"`
<STRIP what is the same as in the 'before' part>
openat(AT_FDCWD, "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa", O_CREAT|O_NOCTTY|O_NONBLOC) = -1 ENAMETOOLONG (File name too long)
<STRIP what is the same as in the 'before' part>
If we leave something like 'perf trace -e string' to trace all syscalls
with a string, and then do some 'perf top', to get some annotation for
the augmented_raw_syscalls.o BPF program we get:
│ → callq *ffffffffc45576d1 ▒
│ augmented_args->filename.size = probe_read_str(&augmented_args->filename.value, ▒
0.05 │ mov %eax,0x40(%r13)
Looking with pahole, expanding types, asking for hex offsets and sizes,
and use of BTF type information to see what is at that 0x40 offset from
%r13:
# pahole -F btf -C augmented_args_filename --expand_types --hex /home/acme/git/perf/tools/perf/examples/bpf/augmented_raw_syscalls.o
struct augmented_args_filename {
struct syscall_enter_args {
long long unsigned int common_tp_fields; /* 0 0x8 */
long int syscall_nr; /* 0x8 0x8 */
long unsigned int args[6]; /* 0x10 0x30 */
} args; /* 0 0x40 */
/* --- cacheline 1 boundary (64 bytes) --- */
struct augmented_filename {
unsigned int size; /* 0x40 0x4 */
int reserved; /* 0x44 0x4 */
char value[4096]; /* 0x48 0x1000 */
} filename; /* 0x40 0x1008 */
/* size: 4168, cachelines: 66, members: 2 */
/* last cacheline: 8 bytes */
};
#
Then looking if PATH_MAX leaves some signature in the tests:
│ if (augmented_args->filename.size < sizeof(augmented_args->filename.value)) { ▒
│ cmp $0xfff,%rdi
0xfff == 4095
sizeof(augmented_args->filename.value) == PATH_MAX == 4096
[1] https://sysdig.com/blog/the-art-of-writing-ebpf-programs-a-primer/
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andrii Nakryiko <andriin@fb.com>
Cc: Daniel Borkmann <borkmann@iogearbox.net>
Cc: Gianluca Borello <g.borello@gmail.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Luis Cláudio Gonçalves <lclaudio@redhat.com>
cc: Martin 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-76gce2d2ghzq537ubwhjkone@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'tools')
-rw-r--r-- | tools/perf/examples/bpf/augmented_raw_syscalls.c | 46 |
1 files changed, 28 insertions, 18 deletions
diff --git a/tools/perf/examples/bpf/augmented_raw_syscalls.c b/tools/perf/examples/bpf/augmented_raw_syscalls.c index 9f8b31ad7a49..2422894a8194 100644 --- a/tools/perf/examples/bpf/augmented_raw_syscalls.c +++ b/tools/perf/examples/bpf/augmented_raw_syscalls.c @@ -15,6 +15,7 @@ */ #include <unistd.h> +#include <linux/limits.h> #include <pid_filter.h> /* bpf-output associated map */ @@ -41,7 +42,7 @@ struct syscall_exit_args { struct augmented_filename { unsigned int size; int reserved; - char value[256]; + char value[PATH_MAX]; }; /* syscalls where the first arg is a string */ @@ -119,23 +120,32 @@ struct augmented_filename { pid_filter(pids_filtered); +struct augmented_args_filename { + struct syscall_enter_args args; + struct augmented_filename filename; +}; + +bpf_map(augmented_filename_map, PERCPU_ARRAY, int, struct augmented_args_filename, 1); + SEC("raw_syscalls:sys_enter") int sys_enter(struct syscall_enter_args *args) { - struct { - struct syscall_enter_args args; - struct augmented_filename filename; - } augmented_args; - struct syscall *syscall; - unsigned int len = sizeof(augmented_args); + struct augmented_args_filename *augmented_args; + unsigned int len = sizeof(*augmented_args); const void *filename_arg = NULL; + struct syscall *syscall; + int key = 0; + + augmented_args = bpf_map_lookup_elem(&augmented_filename_map, &key); + if (augmented_args == NULL) + return 1; if (pid_filter__has(&pids_filtered, getpid())) return 0; - probe_read(&augmented_args.args, sizeof(augmented_args.args), args); + probe_read(&augmented_args->args, sizeof(augmented_args->args), args); - syscall = bpf_map_lookup_elem(&syscalls, &augmented_args.args.syscall_nr); + syscall = bpf_map_lookup_elem(&syscalls, &augmented_args->args.syscall_nr); if (syscall == NULL || !syscall->enabled) return 0; /* @@ -191,7 +201,7 @@ int sys_enter(struct syscall_enter_args *args) * processor architecture, making the kernel part the same no matter what * kernel version or processor architecture it runs on. */ - switch (augmented_args.args.syscall_nr) { + switch (augmented_args->args.syscall_nr) { case SYS_ACCT: case SYS_ADD_KEY: case SYS_CHDIR: @@ -263,20 +273,20 @@ int sys_enter(struct syscall_enter_args *args) } if (filename_arg != NULL) { - augmented_args.filename.reserved = 0; - augmented_args.filename.size = probe_read_str(&augmented_args.filename.value, - sizeof(augmented_args.filename.value), + augmented_args->filename.reserved = 0; + augmented_args->filename.size = probe_read_str(&augmented_args->filename.value, + sizeof(augmented_args->filename.value), filename_arg); - if (augmented_args.filename.size < sizeof(augmented_args.filename.value)) { - len -= sizeof(augmented_args.filename.value) - augmented_args.filename.size; - len &= sizeof(augmented_args.filename.value) - 1; + if (augmented_args->filename.size < sizeof(augmented_args->filename.value)) { + len -= sizeof(augmented_args->filename.value) - augmented_args->filename.size; + len &= sizeof(augmented_args->filename.value) - 1; } } else { - len = sizeof(augmented_args.args); + len = sizeof(augmented_args->args); } /* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */ - return perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, &augmented_args, len); + return perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, augmented_args, len); } SEC("raw_syscalls:sys_exit") |