tools/testing/selftests/bpf/progs/test_get_stack_rawtp.c

   1 // SPDX-License-Identifier: GPL-2.0
   2
   3 #include <linux/bpf.h>
   4 #include "bpf_helpers.h"
   5
   6 /* Permit pretty deep stack traces */
   7 #define MAX_STACK_RAWTP 100
   8 struct stack_trace_t {
   9         int pid;
  10         int kern_stack_size;
  11         int user_stack_size;
  12         int user_stack_buildid_size;
  13         __u64 kern_stack[MAX_STACK_RAWTP];
  14         __u64 user_stack[MAX_STACK_RAWTP];
  15         struct bpf_stack_build_id user_stack_buildid[MAX_STACK_RAWTP];
  16 };
  17
  18 struct {
  19         __uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
  20         __uint(max_entries, 2);
  21         __uint(key_size, sizeof(int));
  22         __uint(value_size, sizeof(__u32));
  23 } perfmap SEC(".maps");
  24
  25 struct {
  26         __uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
  27         __uint(max_entries, 1);
  28         __type(key, __u32);
  29         __type(value, struct stack_trace_t);
  30 } stackdata_map SEC(".maps");
  31
  32 /* Allocate per-cpu space twice the needed. For the code below
  33  *   usize = bpf_get_stack(ctx, raw_data, max_len, BPF_F_USER_STACK);
  34  *   if (usize < 0)
  35  *     return 0;
  36  *   ksize = bpf_get_stack(ctx, raw_data + usize, max_len - usize, 0);
  37  *
  38  * If we have value_size = MAX_STACK_RAWTP * sizeof(__u64),
  39  * verifier will complain that access "raw_data + usize"
  40  * with size "max_len - usize" may be out of bound.
  41  * The maximum "raw_data + usize" is "raw_data + max_len"
  42  * and the maximum "max_len - usize" is "max_len", verifier
  43  * concludes that the maximum buffer access range is
  44  * "raw_data[0...max_len * 2 - 1]" and hence reject the program.
  45  *
  46  * Doubling the to-be-used max buffer size can fix this verifier
  47  * issue and avoid complicated C programming massaging.
  48  * This is an acceptable workaround since there is one entry here.
  49  */
  50 typedef __u64 raw_stack_trace_t[2 * MAX_STACK_RAWTP];
  51 struct {
  52         __uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
  53         __uint(max_entries, 1);
  54         __type(key, __u32);
  55         __type(value, raw_stack_trace_t);
  56 } rawdata_map SEC(".maps");
  57
  58 SEC("tracepoint/raw_syscalls/sys_enter")
  59 int bpf_prog1(void *ctx)
  60 {
  61         int max_len, max_buildid_len, usize, ksize, total_size;
  62         struct stack_trace_t *data;
  63         void *raw_data;
  64         __u32 key = 0;
  65
  66         data = bpf_map_lookup_elem(&stackdata_map, &key);
  67         if (!data)
  68                 return 0;
  69
  70         max_len = MAX_STACK_RAWTP * sizeof(__u64);
  71         max_buildid_len = MAX_STACK_RAWTP * sizeof(struct bpf_stack_build_id);
  72         data->pid = bpf_get_current_pid_tgid();
  73         data->kern_stack_size = bpf_get_stack(ctx, data->kern_stack,
  74                                               max_len, 0);
  75         data->user_stack_size = bpf_get_stack(ctx, data->user_stack, max_len,
  76                                             BPF_F_USER_STACK);
  77         data->user_stack_buildid_size = bpf_get_stack(
  78                 ctx, data->user_stack_buildid, max_buildid_len,
  79                 BPF_F_USER_STACK | BPF_F_USER_BUILD_ID);
  80         bpf_perf_event_output(ctx, &perfmap, 0, data, sizeof(*data));
  81
  82         /* write both kernel and user stacks to the same buffer */
  83         raw_data = bpf_map_lookup_elem(&rawdata_map, &key);
  84         if (!raw_data)
  85                 return 0;
  86
  87         usize = bpf_get_stack(ctx, raw_data, max_len, BPF_F_USER_STACK);
  88         if (usize < 0)
  89                 return 0;
  90
  91         ksize = bpf_get_stack(ctx, raw_data + usize, max_len - usize, 0);
  92         if (ksize < 0)
  93                 return 0;
  94
  95         total_size = usize + ksize;
  96         if (total_size > 0 && total_size <= max_len)
  97                 bpf_perf_event_output(ctx, &perfmap, 0, raw_data, total_size);
  98
  99         return 0;
 100 }
 101
 102 char _license[] SEC("license") = "GPL";
 103 __u32 _version SEC("version") = 1; /* ignored by tracepoints, required by libbpf.a */