LXR linux/tools/perf/examples/bpf/etcsnoop.c

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * Augment the filename syscalls with the contents of the filename pointer argument
   4 * filtering only those that do not start with /etc/.
   5 *
   6 * Test it with:
   7 *
   8 * perf trace -e tools/perf/examples/bpf/augmented_syscalls.c cat /etc/passwd > /dev/null
   9 *
  10 * It'll catch some openat syscalls related to the dynamic linked and
  11 * the last one should be the one for '/etc/passwd'.
  12 *
  13 * This matches what is marshalled into the raw_syscall:sys_enter payload
  14 * expected by the 'perf trace' beautifiers, and can be used by them unmodified,
  15 * which will be done as that feature is implemented in the next csets, for now
  16 * it will appear in a dump done by the default tracepoint handler in 'perf trace',
  17 * that uses bpf_output__fprintf() to just dump those contents, as done with
  18 * the bpf-output event associated with the __bpf_output__ map declared in
  19 * tools/perf/include/bpf/stdio.h.
  20 */
  21
  22#include <stdio.h>
  23
  24/* bpf-output associated map */
  25bpf_map(__augmented_syscalls__, PERF_EVENT_ARRAY, int, u32, __NR_CPUS__);
  26
  27struct augmented_filename {
  28        int     size;
  29        int     reserved;
  30        char    value[64];
  31};
  32
  33#define augmented_filename_syscall_enter(syscall)                                               \
  34struct augmented_enter_##syscall##_args {                                                       \
  35        struct syscall_enter_##syscall##_args   args;                                           \
  36        struct augmented_filename               filename;                                       \
  37};                                                                                              \
  38int syscall_enter(syscall)(struct syscall_enter_##syscall##_args *args)                         \
  39{                                                                                               \
  40        char etc[6] = "/etc/";                                                                  \
  41        struct augmented_enter_##syscall##_args augmented_args = { .filename.reserved = 0, };   \
  42        probe_read(&augmented_args.args, sizeof(augmented_args.args), args);                    \
  43        augmented_args.filename.size = probe_read_str(&augmented_args.filename.value,           \
  44                                                      sizeof(augmented_args.filename.value),    \
  45                                                      args->filename_ptr);                      \
  46        if (__builtin_memcmp(augmented_args.filename.value, etc, 4) != 0)                       \
  47                return 0;                                                                       \
  48        /* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */  \
  49        return perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU,              \
  50                                 &augmented_args,                                               \
  51                                 (sizeof(augmented_args) - sizeof(augmented_args.filename.value) + \
  52                                 augmented_args.filename.size));                                \
  53}
  54
  55struct syscall_enter_openat_args {
  56        unsigned long long common_tp_fields;
  57        long               syscall_nr;
  58        long               dfd;
  59        char               *filename_ptr;
  60        long               flags;
  61        long               mode;
  62};
  63
  64augmented_filename_syscall_enter(openat);
  65
  66struct syscall_enter_open_args {
  67        unsigned long long common_tp_fields;
  68        long               syscall_nr;
  69        char               *filename_ptr;
  70        long               flags;
  71        long               mode;
  72};
  73
  74augmented_filename_syscall_enter(open);
  75
  76license(GPL);
  77