add new system file

hc

2024-02-20 102a0743326a03cd1a1202ceda21e175b7d3575c

 kernel/tools/testing/selftests/bpf/trace_helpers.c
..
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@@ -4,11 +4,14 @@
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 #include <string.h>
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 #include <assert.h>
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 #include <errno.h>
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+#include <fcntl.h>
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 #include <poll.h>
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 #include <unistd.h>
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 #include <linux/perf_event.h>
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 #include <sys/mman.h>
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 #include "trace_helpers.h"
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+
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+#define DEBUGFS "/sys/kernel/debug/tracing/"
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 #define MAX_SYMS 300000
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 static struct ksym syms[MAX_SYMS];
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@@ -30,9 +33,7 @@
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 	if (!f)
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 		return -ENOENT;
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-	while (!feof(f)) {
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-		if (!fgets(buf, sizeof(buf), f))
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-			break;
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+	while (fgets(buf, sizeof(buf), f)) {
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 		if (sscanf(buf, "%p %c %s", &addr, &symbol, func) != 3)
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 			break;
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 		if (!addr)
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@@ -89,126 +90,49 @@
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 	return 0;
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 }
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92
 
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-static int page_size;
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-static int page_cnt = 8;
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-static struct perf_event_mmap_page *header;
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-
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-int perf_event_mmap_header(int fd, struct perf_event_mmap_page **header)
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+/* open kallsyms and read symbol addresses on the fly. Without caching all symbols,
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+ * this is faster than load + find.
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+ */
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+int kallsyms_find(const char *sym, unsigned long long *addr)
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 {
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-	void *base;
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-	int mmap_size;
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+	char type, name[500];
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+	unsigned long long value;
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+	int err = 0;
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+	FILE *f;
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-	page_size = getpagesize();
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-	mmap_size = page_size * (page_cnt + 1);
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+	f = fopen("/proc/kallsyms", "r");
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+	if (!f)
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+		return -EINVAL;
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-	base = mmap(NULL, mmap_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
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-	if (base == MAP_FAILED) {
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-		printf("mmap err\n");
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-		return -1;
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-	}
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-
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-	*header = base;
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-	return 0;
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-}
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-
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-int perf_event_mmap(int fd)
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-{
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-	return perf_event_mmap_header(fd, &header);
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-}
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-
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-static int perf_event_poll(int fd)
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-{
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-	struct pollfd pfd = { .fd = fd, .events = POLLIN };
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-
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-	return poll(&pfd, 1, 1000);
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-}
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-
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-struct perf_event_sample {
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-	struct perf_event_header header;
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-	__u32 size;
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-	char data[];
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-};
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-
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-static enum bpf_perf_event_ret bpf_perf_event_print(void *event, void *priv)
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-{
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-	struct perf_event_sample *e = event;
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-	perf_event_print_fn fn = priv;
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-	int ret;
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-
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-	if (e->header.type == PERF_RECORD_SAMPLE) {
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-		ret = fn(e->data, e->size);
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-		if (ret != LIBBPF_PERF_EVENT_CONT)
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-			return ret;
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-	} else if (e->header.type == PERF_RECORD_LOST) {
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-		struct {
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-			struct perf_event_header header;
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-			__u64 id;
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-			__u64 lost;
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-		} *lost = (void *) e;
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-		printf("lost %lld events\n", lost->lost);
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-	} else {
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-		printf("unknown event type=%d size=%d\n",
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-		       e->header.type, e->header.size);
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-	}
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-
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-	return LIBBPF_PERF_EVENT_CONT;
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-}
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-
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-int perf_event_poller(int fd, perf_event_print_fn output_fn)
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-{
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-	enum bpf_perf_event_ret ret;
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-	void *buf = NULL;
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-	size_t len = 0;
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-
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-	for (;;) {
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-		perf_event_poll(fd);
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-		ret = bpf_perf_event_read_simple(header, page_cnt * page_size,
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-						 page_size, &buf, &len,
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-						 bpf_perf_event_print,
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-						 output_fn);
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-		if (ret != LIBBPF_PERF_EVENT_CONT)
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-			break;
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-	}
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-	free(buf);
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-
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-	return ret;
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-}
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-
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-int perf_event_poller_multi(int *fds, struct perf_event_mmap_page **headers,
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-			    int num_fds, perf_event_print_fn output_fn)
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-{
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-	enum bpf_perf_event_ret ret;
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-	struct pollfd *pfds;
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-	void *buf = NULL;
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-	size_t len = 0;
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-	int i;
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-
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-	pfds = calloc(num_fds, sizeof(*pfds));
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-	if (!pfds)
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-		return LIBBPF_PERF_EVENT_ERROR;
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-
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-	for (i = 0; i < num_fds; i++) {
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-		pfds[i].fd = fds[i];
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-		pfds[i].events = POLLIN;
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-	}
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-
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-	for (;;) {
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-		poll(pfds, num_fds, 1000);
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-		for (i = 0; i < num_fds; i++) {
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-			if (!pfds[i].revents)
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-				continue;
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-
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-			ret = bpf_perf_event_read_simple(headers[i],
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-							 page_cnt * page_size,
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-							 page_size, &buf, &len,
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-							 bpf_perf_event_print,
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-							 output_fn);
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-			if (ret != LIBBPF_PERF_EVENT_CONT)
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-				break;
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+	while (fscanf(f, "%llx %c %499s%*[^\n]\n", &value, &type, name) > 0) {
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+		if (strcmp(name, sym) == 0) {
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+			*addr = value;
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+			goto out;
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 		}
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 	}
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-	free(buf);
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-	free(pfds);
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+	err = -ENOENT;
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-	return ret;
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+out:
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+	fclose(f);
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+	return err;
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+}
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+
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+void read_trace_pipe(void)
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+{
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+	int trace_fd;
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+
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+	trace_fd = open(DEBUGFS "trace_pipe", O_RDONLY, 0);
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+	if (trace_fd < 0)
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+		return;
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+
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+	while (1) {
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+		static char buf[4096];
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+		ssize_t sz;
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+
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+		sz = read(trace_fd, buf, sizeof(buf) - 1);
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+		if (sz > 0) {
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+			buf[sz] = 0;
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+			puts(buf);
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+		}
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+	}
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 }