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Linux/tools/testing/selftests/bpf/trace_helpers.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 #include <stdio.h>
  3 #include <stdlib.h>
  4 #include <string.h>
  5 #include <assert.h>
  6 #include <errno.h>
  7 #include <poll.h>
  8 #include <unistd.h>
  9 #include <linux/perf_event.h>
 10 #include <sys/mman.h>
 11 #include "trace_helpers.h"
 12 
 13 #define MAX_SYMS 300000
 14 static struct ksym syms[MAX_SYMS];
 15 static int sym_cnt;
 16 
 17 static int ksym_cmp(const void *p1, const void *p2)
 18 {
 19         return ((struct ksym *)p1)->addr - ((struct ksym *)p2)->addr;
 20 }
 21 
 22 int load_kallsyms(void)
 23 {
 24         FILE *f = fopen("/proc/kallsyms", "r");
 25         char func[256], buf[256];
 26         char symbol;
 27         void *addr;
 28         int i = 0;
 29 
 30         if (!f)
 31                 return -ENOENT;
 32 
 33         while (!feof(f)) {
 34                 if (!fgets(buf, sizeof(buf), f))
 35                         break;
 36                 if (sscanf(buf, "%p %c %s", &addr, &symbol, func) != 3)
 37                         break;
 38                 if (!addr)
 39                         continue;
 40                 syms[i].addr = (long) addr;
 41                 syms[i].name = strdup(func);
 42                 i++;
 43         }
 44         sym_cnt = i;
 45         qsort(syms, sym_cnt, sizeof(struct ksym), ksym_cmp);
 46         return 0;
 47 }
 48 
 49 struct ksym *ksym_search(long key)
 50 {
 51         int start = 0, end = sym_cnt;
 52         int result;
 53 
 54         while (start < end) {
 55                 size_t mid = start + (end - start) / 2;
 56 
 57                 result = key - syms[mid].addr;
 58                 if (result < 0)
 59                         end = mid;
 60                 else if (result > 0)
 61                         start = mid + 1;
 62                 else
 63                         return &syms[mid];
 64         }
 65 
 66         if (start >= 1 && syms[start - 1].addr < key &&
 67             key < syms[start].addr)
 68                 /* valid ksym */
 69                 return &syms[start - 1];
 70 
 71         /* out of range. return _stext */
 72         return &syms[0];
 73 }
 74 
 75 long ksym_get_addr(const char *name)
 76 {
 77         int i;
 78 
 79         for (i = 0; i < sym_cnt; i++) {
 80                 if (strcmp(syms[i].name, name) == 0)
 81                         return syms[i].addr;
 82         }
 83 
 84         return 0;
 85 }
 86 
 87 static int page_size;
 88 static int page_cnt = 8;
 89 static struct perf_event_mmap_page *header;
 90 
 91 int perf_event_mmap(int fd)
 92 {
 93         void *base;
 94         int mmap_size;
 95 
 96         page_size = getpagesize();
 97         mmap_size = page_size * (page_cnt + 1);
 98 
 99         base = mmap(NULL, mmap_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
100         if (base == MAP_FAILED) {
101                 printf("mmap err\n");
102                 return -1;
103         }
104 
105         header = base;
106         return 0;
107 }
108 
109 static int perf_event_poll(int fd)
110 {
111         struct pollfd pfd = { .fd = fd, .events = POLLIN };
112 
113         return poll(&pfd, 1, 1000);
114 }
115 
116 struct perf_event_sample {
117         struct perf_event_header header;
118         __u32 size;
119         char data[];
120 };
121 
122 static enum bpf_perf_event_ret bpf_perf_event_print(void *event, void *priv)
123 {
124         struct perf_event_sample *e = event;
125         perf_event_print_fn fn = priv;
126         int ret;
127 
128         if (e->header.type == PERF_RECORD_SAMPLE) {
129                 ret = fn(e->data, e->size);
130                 if (ret != LIBBPF_PERF_EVENT_CONT)
131                         return ret;
132         } else if (e->header.type == PERF_RECORD_LOST) {
133                 struct {
134                         struct perf_event_header header;
135                         __u64 id;
136                         __u64 lost;
137                 } *lost = (void *) e;
138                 printf("lost %lld events\n", lost->lost);
139         } else {
140                 printf("unknown event type=%d size=%d\n",
141                        e->header.type, e->header.size);
142         }
143 
144         return LIBBPF_PERF_EVENT_CONT;
145 }
146 
147 int perf_event_poller(int fd, perf_event_print_fn output_fn)
148 {
149         enum bpf_perf_event_ret ret;
150         void *buf = NULL;
151         size_t len = 0;
152 
153         for (;;) {
154                 perf_event_poll(fd);
155                 ret = bpf_perf_event_read_simple(header, page_cnt * page_size,
156                                                  page_size, &buf, &len,
157                                                  bpf_perf_event_print,
158                                                  output_fn);
159                 if (ret != LIBBPF_PERF_EVENT_CONT)
160                         break;
161         }
162         free(buf);
163 
164         return ret;
165 }
166 

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