ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 293 insertions, 0 deletions

diff --git a/tools/perf/util/bpf-utils.c b/tools/perf/util/bpf-utils.c
new file mode 100644
index 000000000..69148197b
--- /dev/null
+++ b/tools/perf/util/bpf-utils.c
@@ -0,0 +1,293 @@
+// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
+
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+
+#include <errno.h>
+#include <stdlib.h>
+#include <linux/err.h>
+#include <linux/kernel.h>
+#include <bpf/bpf.h>
+#include "bpf-utils.h"
+#include "debug.h"
+
+struct bpil_array_desc {
+	int	array_offset;	/* e.g. offset of jited_prog_insns */
+	int	count_offset;	/* e.g. offset of jited_prog_len */
+	int	size_offset;	/* > 0: offset of rec size,
+				 * < 0: fix size of -size_offset
+				 */
+};
+
+static const struct bpil_array_desc bpil_array_desc[] = {
+	[PERF_BPIL_JITED_INSNS] = {
+		offsetof(struct bpf_prog_info, jited_prog_insns),
+		offsetof(struct bpf_prog_info, jited_prog_len),
+		-1,
+	},
+	[PERF_BPIL_XLATED_INSNS] = {
+		offsetof(struct bpf_prog_info, xlated_prog_insns),
+		offsetof(struct bpf_prog_info, xlated_prog_len),
+		-1,
+	},
+	[PERF_BPIL_MAP_IDS] = {
+		offsetof(struct bpf_prog_info, map_ids),
+		offsetof(struct bpf_prog_info, nr_map_ids),
+		-(int)sizeof(__u32),
+	},
+	[PERF_BPIL_JITED_KSYMS] = {
+		offsetof(struct bpf_prog_info, jited_ksyms),
+		offsetof(struct bpf_prog_info, nr_jited_ksyms),
+		-(int)sizeof(__u64),
+	},
+	[PERF_BPIL_JITED_FUNC_LENS] = {
+		offsetof(struct bpf_prog_info, jited_func_lens),
+		offsetof(struct bpf_prog_info, nr_jited_func_lens),
+		-(int)sizeof(__u32),
+	},
+	[PERF_BPIL_FUNC_INFO] = {
+		offsetof(struct bpf_prog_info, func_info),
+		offsetof(struct bpf_prog_info, nr_func_info),
+		offsetof(struct bpf_prog_info, func_info_rec_size),
+	},
+	[PERF_BPIL_LINE_INFO] = {
+		offsetof(struct bpf_prog_info, line_info),
+		offsetof(struct bpf_prog_info, nr_line_info),
+		offsetof(struct bpf_prog_info, line_info_rec_size),
+	},
+	[PERF_BPIL_JITED_LINE_INFO] = {
+		offsetof(struct bpf_prog_info, jited_line_info),
+		offsetof(struct bpf_prog_info, nr_jited_line_info),
+		offsetof(struct bpf_prog_info, jited_line_info_rec_size),
+	},
+	[PERF_BPIL_PROG_TAGS] = {
+		offsetof(struct bpf_prog_info, prog_tags),
+		offsetof(struct bpf_prog_info, nr_prog_tags),
+		-(int)sizeof(__u8) * BPF_TAG_SIZE,
+	},
+
+};
+
+static __u32 bpf_prog_info_read_offset_u32(struct bpf_prog_info *info,
+					   int offset)
+{
+	__u32 *array = (__u32 *)info;
+
+	if (offset >= 0)
+		return array[offset / sizeof(__u32)];
+	return -(int)offset;
+}
+
+static __u64 bpf_prog_info_read_offset_u64(struct bpf_prog_info *info,
+					   int offset)
+{
+	__u64 *array = (__u64 *)info;
+
+	if (offset >= 0)
+		return array[offset / sizeof(__u64)];
+	return -(int)offset;
+}
+
+static void bpf_prog_info_set_offset_u32(struct bpf_prog_info *info, int offset,
+					 __u32 val)
+{
+	__u32 *array = (__u32 *)info;
+
+	if (offset >= 0)
+		array[offset / sizeof(__u32)] = val;
+}
+
+static void bpf_prog_info_set_offset_u64(struct bpf_prog_info *info, int offset,
+					 __u64 val)
+{
+	__u64 *array = (__u64 *)info;
+
+	if (offset >= 0)
+		array[offset / sizeof(__u64)] = val;
+}
+
+struct perf_bpil *
+get_bpf_prog_info_linear(int fd, __u64 arrays)
+{
+	struct bpf_prog_info info = {};
+	struct perf_bpil *info_linear;
+	__u32 info_len = sizeof(info);
+	__u32 data_len = 0;
+	int i, err;
+	__u8 *ptr;
+
+	if (arrays >> PERF_BPIL_LAST_ARRAY)
+		return ERR_PTR(-EINVAL);
+
+	/* step 1: get array dimensions */
+	err = bpf_obj_get_info_by_fd(fd, &info, &info_len);
+	if (err) {
+		pr_debug("can't get prog info: %m\n");
+		return ERR_PTR(-EFAULT);
+	}
+	if (info.type >= __MAX_BPF_PROG_TYPE)
+		pr_debug("%s:%d: unexpected program type %u\n", __func__, __LINE__, info.type);
+
+	/* step 2: calculate total size of all arrays */
+	for (i = PERF_BPIL_FIRST_ARRAY; i < PERF_BPIL_LAST_ARRAY; ++i) {
+		const struct bpil_array_desc *desc = &bpil_array_desc[i];
+		bool include_array = (arrays & (1UL << i)) > 0;
+		__u32 count, size;
+
+		/* kernel is too old to support this field */
+		if (info_len < desc->array_offset + sizeof(__u32) ||
+		    info_len < desc->count_offset + sizeof(__u32) ||
+		    (desc->size_offset > 0 && info_len < (__u32)desc->size_offset))
+			include_array = false;
+
+		if (!include_array) {
+			arrays &= ~(1UL << i);	/* clear the bit */
+			continue;
+		}
+
+		count = bpf_prog_info_read_offset_u32(&info, desc->count_offset);
+		size  = bpf_prog_info_read_offset_u32(&info, desc->size_offset);
+
+		data_len += roundup(count * size, sizeof(__u64));
+	}
+
+	/* step 3: allocate continuous memory */
+	info_linear = malloc(sizeof(struct perf_bpil) + data_len);
+	if (!info_linear)
+		return ERR_PTR(-ENOMEM);
+
+	/* step 4: fill data to info_linear->info */
+	info_linear->arrays = arrays;
+	memset(&info_linear->info, 0, sizeof(info));
+	ptr = info_linear->data;
+
+	for (i = PERF_BPIL_FIRST_ARRAY; i < PERF_BPIL_LAST_ARRAY; ++i) {
+		const struct bpil_array_desc *desc = &bpil_array_desc[i];
+		__u32 count, size;
+
+		if ((arrays & (1UL << i)) == 0)
+			continue;
+
+		count = bpf_prog_info_read_offset_u32(&info, desc->count_offset);
+		size  = bpf_prog_info_read_offset_u32(&info, desc->size_offset);
+		bpf_prog_info_set_offset_u32(&info_linear->info,
+					     desc->count_offset, count);
+		bpf_prog_info_set_offset_u32(&info_linear->info,
+					     desc->size_offset, size);
+		assert(ptr >= info_linear->data);
+		assert(ptr < &info_linear->data[data_len]);
+		bpf_prog_info_set_offset_u64(&info_linear->info,
+					     desc->array_offset,
+					     ptr_to_u64(ptr));
+		ptr += roundup(count * size, sizeof(__u64));
+	}
+
+	/* step 5: call syscall again to get required arrays */
+	err = bpf_obj_get_info_by_fd(fd, &info_linear->info, &info_len);
+	if (err) {
+		pr_debug("can't get prog info: %m\n");
+		free(info_linear);
+		return ERR_PTR(-EFAULT);
+	}
+	if (info_linear->info.type >= __MAX_BPF_PROG_TYPE) {
+		pr_debug("%s:%d: unexpected program type %u\n",
+			 __func__, __LINE__, info_linear->info.type);
+	}
+
+	/* step 6: verify the data */
+	ptr = info_linear->data;
+	for (i = PERF_BPIL_FIRST_ARRAY; i < PERF_BPIL_LAST_ARRAY; ++i) {
+		const struct bpil_array_desc *desc = &bpil_array_desc[i];
+		__u32 count1, count2, size1, size2;
+		__u64 ptr2;
+
+		if ((arrays & (1UL << i)) == 0)
+			continue;
+
+		count1 = bpf_prog_info_read_offset_u32(&info, desc->count_offset);
+		count2 = bpf_prog_info_read_offset_u32(&info_linear->info,
+						   desc->count_offset);
+		if (count1 != count2) {
+			pr_warning("%s: mismatch in element count %u vs %u\n", __func__, count1, count2);
+			free(info_linear);
+			return ERR_PTR(-ERANGE);
+		}
+
+		size1 = bpf_prog_info_read_offset_u32(&info, desc->size_offset);
+		size2 = bpf_prog_info_read_offset_u32(&info_linear->info,
+						   desc->size_offset);
+		if (size1 != size2) {
+			pr_warning("%s: mismatch in rec size %u vs %u\n", __func__, size1, size2);
+			free(info_linear);
+			return ERR_PTR(-ERANGE);
+		}
+		ptr2 = bpf_prog_info_read_offset_u64(&info_linear->info, desc->array_offset);
+		if (ptr_to_u64(ptr) != ptr2) {
+			pr_warning("%s: mismatch in array %p vs %llx\n", __func__, ptr, ptr2);
+			free(info_linear);
+			return ERR_PTR(-ERANGE);
+		}
+		ptr += roundup(count1 * size1, sizeof(__u64));
+	}
+
+	/* step 7: update info_len and data_len */
+	info_linear->info_len = sizeof(struct bpf_prog_info);
+	info_linear->data_len = data_len;
+
+	return info_linear;
+}
+
+void bpil_addr_to_offs(struct perf_bpil *info_linear)
+{
+	int i;
+
+	for (i = PERF_BPIL_FIRST_ARRAY; i < PERF_BPIL_LAST_ARRAY; ++i) {
+		const struct bpil_array_desc *desc = &bpil_array_desc[i];
+		__u64 addr, offs;
+
+		if ((info_linear->arrays & (1UL << i)) == 0)
+			continue;
+
+		addr = bpf_prog_info_read_offset_u64(&info_linear->info,
+						     desc->array_offset);
+		offs = addr - ptr_to_u64(info_linear->data);
+		bpf_prog_info_set_offset_u64(&info_linear->info,
+					     desc->array_offset, offs);
+	}
+}
+
+void bpil_offs_to_addr(struct perf_bpil *info_linear)
+{
+	int i;
+
+	for (i = PERF_BPIL_FIRST_ARRAY; i < PERF_BPIL_LAST_ARRAY; ++i) {
+		const struct bpil_array_desc *desc = &bpil_array_desc[i];
+		__u64 addr, offs;
+		__u32 count, size;
+
+		if ((info_linear->arrays & (1UL << i)) == 0)
+			continue;
+
+		offs = bpf_prog_info_read_offset_u64(&info_linear->info,
+						     desc->array_offset);
+		count = bpf_prog_info_read_offset_u32(&info_linear->info,
+						      desc->count_offset);
+		size = bpf_prog_info_read_offset_u32(&info_linear->info,
+						     desc->size_offset);
+		/* offset and extent from perf.data are untrusted — keep within data[] */
+		if (offs >= info_linear->data_len ||
+		    (u64)count * size > info_linear->data_len - offs) {
+			bpf_prog_info_set_offset_u64(&info_linear->info,
+						     desc->array_offset, 0);
+			bpf_prog_info_set_offset_u32(&info_linear->info,
+						     desc->count_offset, 0);
+			/* clear the bit so bpil_addr_to_offs() won't reverse a zeroed address */
+			info_linear->arrays &= ~(1UL << i);
+			continue;
+		}
+		addr = offs + ptr_to_u64(info_linear->data);
+		bpf_prog_info_set_offset_u64(&info_linear->info,
+					     desc->array_offset, addr);
+	}
+}