Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 888 insertions, 0 deletions

diff --git a/tools/perf/tests/code-reading.c b/tools/perf/tests/code-reading.c
new file mode 100644
index 000000000..f0e8ea875
--- /dev/null
+++ b/tools/perf/tests/code-reading.c
@@ -0,0 +1,888 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <errno.h>
+#include <linux/kconfig.h>
+#include <linux/kernel.h>
+#include <linux/rbtree.h>
+#include <linux/types.h>
+#include <linux/zalloc.h>
+#include <inttypes.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/param.h>
+#include <sys/utsname.h>
+#include <perf/cpumap.h>
+#include <perf/evlist.h>
+#include <perf/mmap.h>
+
+#include "debug.h"
+#include "dso.h"
+#include "env.h"
+#include "parse-events.h"
+#include "evlist.h"
+#include "evsel.h"
+#include "thread_map.h"
+#include "machine.h"
+#include "map.h"
+#include "symbol.h"
+#include "event.h"
+#include "record.h"
+#include "util/mmap.h"
+#include "util/string2.h"
+#include "util/synthetic-events.h"
+#include "util/util.h"
+#include "thread.h"
+
+#include "tests.h"
+
+#include <linux/ctype.h>
+
+#define BUFSZ	1024
+#define READLEN	128
+
+struct tested_section {
+	struct rb_node rb_node;
+	u64 addr;
+	char *path;
+};
+
+static bool tested_code_insert_or_exists(const char *path, u64 addr,
+					 struct rb_root *tested_sections)
+{
+	struct rb_node **node = &tested_sections->rb_node;
+	struct rb_node *parent = NULL;
+	struct tested_section *data;
+
+	while (*node) {
+		int cmp;
+
+		parent = *node;
+		data = rb_entry(*node, struct tested_section, rb_node);
+		cmp = strcmp(path, data->path);
+		if (!cmp) {
+			if (addr < data->addr)
+				cmp = -1;
+			else if (addr > data->addr)
+				cmp = 1;
+			else
+				return true; /* already tested */
+		}
+
+		if (cmp < 0)
+			node = &(*node)->rb_left;
+		else
+			node = &(*node)->rb_right;
+	}
+
+	data = zalloc(sizeof(*data));
+	if (!data)
+		return true;
+
+	data->addr = addr;
+	data->path = strdup(path);
+	if (!data->path) {
+		free(data);
+		return true;
+	}
+	rb_link_node(&data->rb_node, parent, node);
+	rb_insert_color(&data->rb_node, tested_sections);
+	return false;
+}
+
+static void tested_sections__free(struct rb_root *root)
+{
+	while (!RB_EMPTY_ROOT(root)) {
+		struct rb_node *node = rb_first(root);
+		struct tested_section *ts = rb_entry(node,
+						     struct tested_section,
+						     rb_node);
+
+		rb_erase(node, root);
+		free(ts->path);
+		free(ts);
+	}
+}
+
+static size_t read_objdump_chunk(const char **line, unsigned char **buf,
+				 size_t *buf_len)
+{
+	size_t bytes_read = 0;
+	unsigned char *chunk_start = *buf;
+
+	/* Read bytes */
+	while (*buf_len > 0) {
+		char c1, c2;
+
+		/* Get 2 hex digits */
+		c1 = *(*line)++;
+		if (!isxdigit(c1))
+			break;
+		c2 = *(*line)++;
+		if (!isxdigit(c2))
+			break;
+
+		/* Store byte and advance buf */
+		**buf = (hex(c1) << 4) | hex(c2);
+		(*buf)++;
+		(*buf_len)--;
+		bytes_read++;
+
+		/* End of chunk? */
+		if (isspace(**line))
+			break;
+	}
+
+	/*
+	 * objdump will display raw insn as LE if code endian
+	 * is LE and bytes_per_chunk > 1. In that case reverse
+	 * the chunk we just read.
+	 *
+	 * see disassemble_bytes() at binutils/objdump.c for details
+	 * how objdump chooses display endian)
+	 */
+	if (bytes_read > 1 && !host_is_bigendian()) {
+		unsigned char *chunk_end = chunk_start + bytes_read - 1;
+		unsigned char tmp;
+
+		while (chunk_start < chunk_end) {
+			tmp = *chunk_start;
+			*chunk_start = *chunk_end;
+			*chunk_end = tmp;
+			chunk_start++;
+			chunk_end--;
+		}
+	}
+
+	return bytes_read;
+}
+
+static size_t read_objdump_line(const char *line, unsigned char *buf,
+				size_t buf_len)
+{
+	const char *p;
+	size_t ret, bytes_read = 0;
+
+	/* Skip to a colon */
+	p = strchr(line, ':');
+	if (!p)
+		return 0;
+	p++;
+
+	/* Skip initial spaces */
+	while (*p) {
+		if (!isspace(*p))
+			break;
+		p++;
+	}
+
+	do {
+		ret = read_objdump_chunk(&p, &buf, &buf_len);
+		bytes_read += ret;
+		p++;
+	} while (ret > 0);
+
+	/* return number of successfully read bytes */
+	return bytes_read;
+}
+
+static int read_objdump_output(FILE *f, void *buf, size_t *len, u64 start_addr)
+{
+	char *line = NULL;
+	size_t line_len, off_last = 0;
+	ssize_t ret;
+	int err = 0;
+	u64 addr, last_addr = start_addr;
+
+	while (off_last < *len) {
+		size_t off, read_bytes, written_bytes;
+		unsigned char tmp[BUFSZ];
+
+		ret = getline(&line, &line_len, f);
+		if (feof(f))
+			break;
+		if (ret < 0) {
+			pr_debug("getline failed\n");
+			err = -1;
+			break;
+		}
+
+		/* read objdump data into temporary buffer */
+		read_bytes = read_objdump_line(line, tmp, sizeof(tmp));
+		if (!read_bytes)
+			continue;
+
+		if (sscanf(line, "%"PRIx64, &addr) != 1)
+			continue;
+		if (addr < last_addr) {
+			pr_debug("addr going backwards, read beyond section?\n");
+			break;
+		}
+		last_addr = addr;
+
+		/* copy it from temporary buffer to 'buf' according
+		 * to address on current objdump line */
+		off = addr - start_addr;
+		if (off >= *len)
+			break;
+		written_bytes = MIN(read_bytes, *len - off);
+		memcpy(buf + off, tmp, written_bytes);
+		off_last = off + written_bytes;
+	}
+
+	/* len returns number of bytes that could not be read */
+	*len -= off_last;
+
+	free(line);
+
+	return err;
+}
+
+/*
+ * Only gets GNU objdump version. Returns 0 for llvm-objdump.
+ */
+static int objdump_version(void)
+{
+	size_t line_len;
+	char cmd[PATH_MAX * 2];
+	char *line = NULL;
+	const char *fmt;
+	FILE *f;
+	int ret;
+
+	int version_tmp, version_num = 0;
+	char *version = 0, *token;
+
+	fmt = "%s --version";
+	ret = snprintf(cmd, sizeof(cmd), fmt, test_objdump_path);
+	if (ret <= 0 || (size_t)ret >= sizeof(cmd))
+		return -1;
+	/* Ignore objdump errors */
+	strcat(cmd, " 2>/dev/null");
+	f = popen(cmd, "r");
+	if (!f) {
+		pr_debug("popen failed\n");
+		return -1;
+	}
+	/* Get first line of objdump --version output */
+	ret = getline(&line, &line_len, f);
+	pclose(f);
+	if (ret < 0) {
+		pr_debug("getline failed\n");
+		return -1;
+	}
+
+	token = strsep(&line, " ");
+	if (token != NULL && !strcmp(token, "GNU")) {
+		// version is last part of first line of objdump --version output.
+		while ((token = strsep(&line, " ")))
+			version = token;
+
+		// Convert version into a format we can compare with
+		token = strsep(&version, ".");
+		version_num = atoi(token);
+		if (version_num)
+			version_num *= 10000;
+
+		token = strsep(&version, ".");
+		version_tmp = atoi(token);
+		if (token)
+			version_num += version_tmp * 100;
+
+		token = strsep(&version, ".");
+		version_tmp = atoi(token);
+		if (token)
+			version_num += version_tmp;
+	}
+
+	return version_num;
+}
+
+static int read_via_objdump(const char *filename, u64 addr, void *buf,
+			    size_t len)
+{
+	u64 stop_address = addr + len;
+	struct utsname uname_buf;
+	char cmd[PATH_MAX * 2];
+	const char *fmt;
+	FILE *f;
+	int ret;
+
+	ret = uname(&uname_buf);
+	if (ret) {
+		pr_debug("uname failed\n");
+		return -1;
+	}
+
+	if (!strncmp(uname_buf.machine, "riscv", 5)) {
+		int version = objdump_version();
+
+		/* Default to this workaround if version parsing fails */
+		if (version < 0 || version > 24100) {
+			/*
+			 * Starting at riscv objdump version 2.41, dumping in
+			 * the middle of an instruction is not supported. riscv
+			 * instructions are aligned along 2-byte intervals and
+			 * can be either 2-bytes or 4-bytes. This makes it
+			 * possible that the stop-address lands in the middle of
+			 * a 4-byte instruction. Increase the stop_address by
+			 * two to ensure an instruction is not cut in half, but
+			 * leave the len as-is so only the expected number of
+			 * bytes are collected.
+			 */
+			stop_address += 2;
+		}
+	}
+
+	fmt = "%s -z -d --start-address=0x%"PRIx64" --stop-address=0x%"PRIx64" %s";
+	ret = snprintf(cmd, sizeof(cmd), fmt, test_objdump_path, addr, stop_address,
+		       filename);
+	if (ret <= 0 || (size_t)ret >= sizeof(cmd))
+		return -1;
+
+	pr_debug("Objdump command is: %s\n", cmd);
+
+	/* Ignore objdump errors */
+	strcat(cmd, " 2>/dev/null");
+
+	f = popen(cmd, "r");
+	if (!f) {
+		pr_debug("popen failed\n");
+		return -1;
+	}
+
+	ret = read_objdump_output(f, buf, &len, addr);
+	if (len) {
+		pr_debug("objdump read too few bytes: %zd\n", len);
+		if (!ret)
+			ret = len;
+	}
+
+	pclose(f);
+
+	return ret;
+}
+
+static void dump_buf(unsigned char *buf, size_t len)
+{
+	size_t i;
+
+	for (i = 0; i < len; i++) {
+		pr_debug("0x%02x ", buf[i]);
+		if (i % 16 == 15)
+			pr_debug("\n");
+	}
+	pr_debug("\n");
+}
+
+static int read_object_code(u64 addr, size_t len, u8 cpumode,
+			    struct thread *thread,
+			    struct rb_root *tested_sections)
+{
+	struct addr_location al;
+	unsigned char buf1[BUFSZ] = {0};
+	unsigned char buf2[BUFSZ] = {0};
+	size_t ret_len;
+	u64 objdump_addr;
+	u64 skip_addr;
+	const char *objdump_name;
+	char decomp_name[KMOD_DECOMP_LEN];
+	bool decomp = false;
+	int ret, err = 0;
+	struct dso *dso;
+
+	pr_debug("Reading object code for memory address: %#"PRIx64"\n", addr);
+
+	addr_location__init(&al);
+	if (!thread__find_map(thread, cpumode, addr, &al) || !map__dso(al.map)) {
+		if (cpumode == PERF_RECORD_MISC_HYPERVISOR) {
+			pr_debug("Hypervisor address can not be resolved - skipping\n");
+			goto out;
+		}
+
+		pr_debug("thread__find_map failed\n");
+		err = -1;
+		goto out;
+	}
+	dso = map__dso(al.map);
+	pr_debug("File is: %s\n", dso__long_name(dso));
+
+	if (dso__symtab_type(dso) == DSO_BINARY_TYPE__KALLSYMS && !dso__is_kcore(dso)) {
+		pr_debug("Unexpected kernel address - skipping\n");
+		goto out;
+	}
+
+	/*
+	 * Don't retest the same addresses. objdump struggles with kcore - try
+	 * each map only once even if the address is different.
+	 */
+	skip_addr = dso__is_kcore(dso) ? map__start(al.map) : al.addr;
+	if (tested_code_insert_or_exists(dso__long_name(dso), skip_addr,
+					 tested_sections)) {
+		pr_debug("Already tested %s @ %#"PRIx64" - skipping\n",
+			 dso__long_name(dso), skip_addr);
+		goto out;
+	}
+
+	pr_debug("On file address is: %#"PRIx64"\n", al.addr);
+
+	if (len > BUFSZ)
+		len = BUFSZ;
+
+	/* Do not go off the map */
+	if (addr + len > map__end(al.map))
+		len = map__end(al.map) - addr;
+
+	/*
+	 * Some architectures (ex: powerpc) have stubs (trampolines) in kernel
+	 * modules to manage long jumps. Check if the ip offset falls in stubs
+	 * sections for kernel modules. And skip module address after text end
+	 */
+	if (dso__is_kmod(dso) && al.addr > dso__text_end(dso)) {
+		pr_debug("skipping the module address %#"PRIx64" after text end\n", al.addr);
+		goto out;
+	}
+
+	/* Read the object code using perf */
+	ret_len = dso__data_read_offset(dso, maps__machine(thread__maps(thread)),
+					al.addr, buf1, len);
+	if (ret_len != len) {
+		pr_debug("dso__data_read_offset failed\n");
+		err = -1;
+		goto out;
+	}
+
+	/*
+	 * Converting addresses for use by objdump requires more information.
+	 * map__load() does that.  See map__rip_2objdump() for details.
+	 */
+	if (map__load(al.map)) {
+		err = -1;
+		goto out;
+	}
+
+	objdump_name = dso__long_name(dso);
+	if (dso__needs_decompress(dso)) {
+		if (dso__decompress_kmodule_path(dso, objdump_name,
+						 decomp_name,
+						 sizeof(decomp_name)) < 0) {
+			pr_debug("decompression failed\n");
+			err = -1;
+			goto out;
+		}
+
+		/* empty pathname means file wasn't actually compressed */
+		if (decomp_name[0] != '\0') {
+			decomp = true;
+			objdump_name = decomp_name;
+		}
+	}
+
+	/* Read the object code using objdump */
+	objdump_addr = map__rip_2objdump(al.map, al.addr);
+	ret = read_via_objdump(objdump_name, objdump_addr, buf2, len);
+
+	if (decomp)
+		unlink(objdump_name);
+
+	if (ret > 0) {
+		/*
+		 * The kernel maps are inaccurate - assume objdump is right in
+		 * that case.
+		 */
+		if (cpumode == PERF_RECORD_MISC_KERNEL ||
+		    cpumode == PERF_RECORD_MISC_GUEST_KERNEL) {
+			len -= ret;
+			if (len) {
+				pr_debug("Reducing len to %zu\n", len);
+			} else if (dso__is_kcore(dso)) {
+				/*
+				 * objdump cannot handle very large segments
+				 * that may be found in kcore.
+				 */
+				pr_debug("objdump failed for kcore");
+				pr_debug(" - skipping\n");
+			} else {
+				err = -1;
+			}
+			goto out;
+		}
+	}
+	if (ret < 0) {
+		pr_debug("read_via_objdump failed\n");
+		err = -1;
+		goto out;
+	}
+
+	/* The results should be identical */
+	if (memcmp(buf1, buf2, len)) {
+		pr_debug("Bytes read differ from those read by objdump\n");
+		pr_debug("buf1 (dso):\n");
+		dump_buf(buf1, len);
+		pr_debug("buf2 (objdump):\n");
+		dump_buf(buf2, len);
+		err = -1;
+		goto out;
+	}
+	pr_debug("Bytes read match those read by objdump\n");
+out:
+	addr_location__exit(&al);
+	return err;
+}
+
+static int process_sample_event(struct machine *machine, struct evlist *evlist,
+				union perf_event *event,
+				struct rb_root *tested_sections)
+{
+	struct perf_sample sample;
+	struct thread *thread;
+	int ret;
+
+	perf_sample__init(&sample, /*all=*/false);
+	ret = evlist__parse_sample(evlist, event, &sample);
+	if (ret) {
+		pr_debug("evlist__parse_sample failed\n");
+		ret = -1;
+		goto out;
+	}
+
+	thread = machine__findnew_thread(machine, sample.pid, sample.tid);
+	if (!thread) {
+		pr_debug("machine__findnew_thread failed\n");
+		ret = -1;
+		goto out;
+	}
+
+	ret = read_object_code(sample.ip, READLEN, sample.cpumode, thread,
+			       tested_sections);
+	thread__put(thread);
+out:
+	perf_sample__exit(&sample);
+	return ret;
+}
+
+static int process_event(struct machine *machine, struct evlist *evlist,
+			 union perf_event *event, struct rb_root *tested_sections)
+{
+	if (event->header.type == PERF_RECORD_SAMPLE)
+		return process_sample_event(machine, evlist, event,
+					    tested_sections);
+
+	if (event->header.type == PERF_RECORD_THROTTLE ||
+	    event->header.type == PERF_RECORD_UNTHROTTLE)
+		return 0;
+
+	if (event->header.type < PERF_RECORD_MAX) {
+		int ret;
+
+		ret = machine__process_event(machine, event, NULL);
+		if (ret < 0)
+			pr_debug("machine__process_event failed, event type %u\n",
+				 event->header.type);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int process_events(struct machine *machine, struct evlist *evlist,
+			  struct rb_root *tested_sections)
+{
+	union perf_event *event;
+	struct mmap *md;
+	int i, ret;
+
+	for (i = 0; i < evlist__core(evlist)->nr_mmaps; i++) {
+		md = &evlist__mmap(evlist)[i];
+		if (perf_mmap__read_init(&md->core) < 0)
+			continue;
+
+		while ((event = perf_mmap__read_event(&md->core)) != NULL) {
+			ret = process_event(machine, evlist, event, tested_sections);
+			perf_mmap__consume(&md->core);
+			if (ret < 0)
+				return ret;
+		}
+		perf_mmap__read_done(&md->core);
+	}
+	return 0;
+}
+
+static int comp(const void *a, const void *b)
+{
+	return *(int *)a - *(int *)b;
+}
+
+static void do_sort_something(void)
+{
+	int buf[40960], i;
+
+	for (i = 0; i < (int)ARRAY_SIZE(buf); i++)
+		buf[i] = ARRAY_SIZE(buf) - i - 1;
+
+	qsort(buf, ARRAY_SIZE(buf), sizeof(int), comp);
+
+	for (i = 0; i < (int)ARRAY_SIZE(buf); i++) {
+		if (buf[i] != i) {
+			pr_debug("qsort failed\n");
+			break;
+		}
+	}
+}
+
+static void sort_something(void)
+{
+	int i;
+
+	for (i = 0; i < 10; i++)
+		do_sort_something();
+}
+
+static void syscall_something(void)
+{
+	int pipefd[2];
+	int i;
+
+	for (i = 0; i < 1000; i++) {
+		if (pipe(pipefd) < 0) {
+			pr_debug("pipe failed\n");
+			break;
+		}
+		close(pipefd[1]);
+		close(pipefd[0]);
+	}
+}
+
+static void fs_something(void)
+{
+	const char *test_file_name = "temp-perf-code-reading-test-file--";
+	FILE *f;
+	int i;
+
+	for (i = 0; i < 1000; i++) {
+		f = fopen(test_file_name, "w+");
+		if (f) {
+			fclose(f);
+			unlink(test_file_name);
+		}
+	}
+}
+
+static void do_something(void)
+{
+	fs_something();
+
+	sort_something();
+
+	syscall_something();
+}
+
+enum {
+	TEST_CODE_READING_OK,
+	TEST_CODE_READING_NO_VMLINUX,
+	TEST_CODE_READING_NO_KCORE,
+	TEST_CODE_READING_NO_ACCESS,
+	TEST_CODE_READING_NO_KERNEL_OBJ,
+};
+
+static int do_test_code_reading(bool try_kcore)
+{
+	struct machine *machine;
+	struct thread *thread;
+	struct record_opts opts = {
+		.mmap_pages	     = UINT_MAX,
+		.user_freq	     = UINT_MAX,
+		.user_interval	     = ULLONG_MAX,
+		.freq		     = 500,
+		.target		     = {
+			.uses_mmap   = true,
+		},
+	};
+	struct rb_root tested_sections = RB_ROOT;
+	struct perf_thread_map *threads = NULL;
+	struct perf_cpu_map *cpus = NULL;
+	struct evlist *evlist = NULL;
+	struct evsel *evsel = NULL;
+	int err = -1, ret;
+	pid_t pid;
+	struct map *map;
+	bool have_vmlinux, have_kcore;
+	struct dso *dso;
+	const char *events[] = { "cpu-cycles", "cpu-cycles:u", "cpu-clock", "cpu-clock:u", NULL };
+	int evidx = 0;
+	struct perf_env host_env;
+
+	pid = getpid();
+
+	perf_env__init(&host_env);
+	machine = machine__new_host(&host_env);
+
+	ret = machine__create_kernel_maps(machine);
+	if (ret < 0) {
+		pr_debug("machine__create_kernel_maps failed\n");
+		goto out_err;
+	}
+
+	/* Force the use of kallsyms instead of vmlinux to try kcore */
+	if (try_kcore)
+		symbol_conf.kallsyms_name = "/proc/kallsyms";
+
+	/* Load kernel map */
+	map = machine__kernel_map(machine);
+	ret = map__load(map);
+	if (ret < 0) {
+		pr_debug("map__load failed\n");
+		goto out_err;
+	}
+	dso = map__dso(map);
+	have_vmlinux = dso__is_vmlinux(dso);
+	have_kcore = dso__is_kcore(dso);
+
+	/* 2nd time through we just try kcore */
+	if (try_kcore && !have_kcore)
+		return TEST_CODE_READING_NO_KCORE;
+
+	/* No point getting kernel events if there is no kernel object */
+	if (!have_vmlinux && !have_kcore)
+		evidx++;
+
+	threads = thread_map__new_by_tid(pid);
+	if (!threads) {
+		pr_debug("thread_map__new_by_tid failed\n");
+		goto out_err;
+	}
+
+	ret = perf_event__synthesize_thread_map(NULL, threads,
+						perf_event__process, machine,
+						true, false);
+	if (ret < 0) {
+		pr_debug("perf_event__synthesize_thread_map failed\n");
+		goto out_err;
+	}
+
+	thread = machine__findnew_thread(machine, pid, pid);
+	if (!thread) {
+		pr_debug("machine__findnew_thread failed\n");
+		goto out_put;
+	}
+
+	cpus = perf_cpu_map__new_online_cpus();
+	if (!cpus) {
+		pr_debug("perf_cpu_map__new failed\n");
+		goto out_put;
+	}
+
+	while (events[evidx]) {
+		const char *str;
+
+		evlist = evlist__new();
+		if (!evlist) {
+			pr_debug("evlist__new failed\n");
+			goto out_put;
+		}
+
+		perf_evlist__set_maps(evlist__core(evlist), cpus, threads);
+
+		str = events[evidx];
+		pr_debug("Parsing event '%s'\n", str);
+		ret = parse_event(evlist, str);
+		if (ret < 0) {
+			pr_debug("parse_events failed\n");
+			goto out_put;
+		}
+
+		evlist__config(evlist, &opts, NULL);
+
+		evlist__for_each_entry(evlist, evsel) {
+			evsel->core.attr.comm = 1;
+			evsel->core.attr.disabled = 1;
+			evsel->core.attr.enable_on_exec = 0;
+		}
+
+		ret = evlist__open(evlist);
+		if (ret < 0) {
+			evidx++;
+
+			if (events[evidx] == NULL && verbose > 0) {
+				char errbuf[512];
+				evlist__strerror_open(evlist, errno, errbuf, sizeof(errbuf));
+				pr_debug("perf_evlist__open() failed!\n%s\n", errbuf);
+			}
+
+			perf_evlist__set_maps(evlist__core(evlist), NULL, NULL);
+			evlist__put(evlist);
+			evlist = NULL;
+			continue;
+		}
+		break;
+	}
+
+	if (events[evidx] == NULL)
+		goto out_put;
+
+	ret = evlist__do_mmap(evlist, UINT_MAX);
+	if (ret < 0) {
+		pr_debug("evlist__mmap failed\n");
+		goto out_put;
+	}
+
+	evlist__enable(evlist);
+
+	do_something();
+
+	evlist__disable(evlist);
+
+	ret = process_events(machine, evlist, &tested_sections);
+	if (ret < 0)
+		goto out_put;
+
+	if (!have_vmlinux && !have_kcore && !try_kcore)
+		err = TEST_CODE_READING_NO_KERNEL_OBJ;
+	else if (!have_vmlinux && !try_kcore)
+		err = TEST_CODE_READING_NO_VMLINUX;
+	else if (strstr(events[evidx], ":u"))
+		err = TEST_CODE_READING_NO_ACCESS;
+	else
+		err = TEST_CODE_READING_OK;
+out_put:
+	thread__put(thread);
+out_err:
+	evlist__put(evlist);
+	perf_cpu_map__put(cpus);
+	perf_thread_map__put(threads);
+	machine__delete(machine);
+	perf_env__exit(&host_env);
+	tested_sections__free(&tested_sections);
+
+	return err;
+}
+
+static int test__code_reading(struct test_suite *test __maybe_unused, int subtest __maybe_unused)
+{
+	int ret;
+
+	ret = do_test_code_reading(false);
+	if (!ret)
+		ret = do_test_code_reading(true);
+
+	switch (ret) {
+	case TEST_CODE_READING_OK:
+		return 0;
+	case TEST_CODE_READING_NO_VMLINUX:
+		pr_debug("no vmlinux\n");
+		return 0;
+	case TEST_CODE_READING_NO_KCORE:
+		pr_debug("no kcore\n");
+		return 0;
+	case TEST_CODE_READING_NO_ACCESS:
+		pr_debug("no access\n");
+		return 0;
+	case TEST_CODE_READING_NO_KERNEL_OBJ:
+		pr_debug("no kernel obj\n");
+		return 0;
+	default:
+		return -1;
+	};
+}
+
+DEFINE_SUITE("Object code reading", code_reading);