[RFC PATCH 07/30] lib: add support for allocation tagging

Suren Baghdasaryan
2022-08-30T21:50:56Z

Introduce CONFIG_ALLOC_TAGGING which provides definitions to easily
instrument allocators. It also registers an "alloc_tags" codetag type
with defbugfs interface to output allocation tags information.

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Co-developed-by: Kent Overstreet <kent.overstreet@linux.dev>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
---
include/asm-generic/codetag.lds.h | 14 +++
include/asm-generic/vmlinux.lds.h | 3 +
include/linux/alloc_tag.h | 66 +++++++++++++
lib/Kconfig.debug | 5 +
lib/Makefile | 2 +
lib/alloc_tag.c | 158 ++++++++++++++++++++++++++++++
scripts/module.lds.S | 7 ++
7 files changed, 255 insertions(+)
create mode 100644 include/asm-generic/codetag.lds.h
create mode 100644 include/linux/alloc_tag.h
create mode 100644 lib/alloc_tag.c

diff --git a/include/asm-generic/codetag.lds.h b/include/asm-generic/codetag.lds.h
new file mode 100644
index 000000000000..64f536b80380
--- /dev/null
+++ b/include/asm-generic/codetag.lds.h
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef __ASM_GENERIC_CODETAG_LDS_H
+#define __ASM_GENERIC_CODETAG_LDS_H
+
+#define SECTION_WITH_BOUNDARIES(_name) \
+ . = ALIGN(8); \
+ __start_##_name = .; \
+ KEEP(*(_name)) \
+ __stop_##_name = .;
+
+#define CODETAG_SECTIONS() \
+ SECTION_WITH_BOUNDARIES(alloc_tags)
+
+#endif /* __ASM_GENERIC_CODETAG_LDS_H */
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 7515a465ec03..c2dc2a59ab2e 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -50,6 +50,8 @@
* [__nosave_begin, __nosave_end] for the nosave data
*/

+#include <asm-generic/codetag.lds.h>
+
#ifndef LOAD_OFFSET
#define LOAD_OFFSET 0
#endif
@@ -348,6 +350,7 @@
__start___dyndbg = .; \
KEEP(*(__dyndbg)) \
__stop___dyndbg = .; \
+ CODETAG_SECTIONS() \
LIKELY_PROFILE() \
BRANCH_PROFILE() \
TRACE_PRINTKS() \
diff --git a/include/linux/alloc_tag.h b/include/linux/alloc_tag.h
new file mode 100644
index 000000000000..b3f589afb1c9
--- /dev/null
+++ b/include/linux/alloc_tag.h
@@ -0,0 +1,66 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * allocation tagging
+ */
+#ifndef _LINUX_ALLOC_TAG_H
+#define _LINUX_ALLOC_TAG_H
+
+#include <linux/bug.h>
+#include <linux/codetag.h>
+#include <linux/container_of.h>
+#include <linux/lazy-percpu-counter.h>
+
+/*
+ * An instance of this structure is created in a special ELF section at every
+ * allocation callsite. At runtime, the special section is treated as
+ * an array of these. Embedded codetag utilizes codetag framework.
+ */
+struct alloc_tag {
+ struct codetag ct;
+ unsigned long last_wrap;
+ struct raw_lazy_percpu_counter call_count;
+ struct raw_lazy_percpu_counter bytes_allocated;
+} __aligned(8);
+
+static inline struct alloc_tag *ct_to_alloc_tag(struct codetag *ct)
+{
+ return container_of(ct, struct alloc_tag, ct);
+}
+
+#define DEFINE_ALLOC_TAG(_alloc_tag) \
+ static struct alloc_tag _alloc_tag __used __aligned(8) \
+ __section("alloc_tags") = { .ct = CODE_TAG_INIT }
+
+#define alloc_tag_counter_read(counter) \
+ __lazy_percpu_counter_read(counter)
+
+static inline void __alloc_tag_sub(union codetag_ref *ref, size_t bytes)
+{
+ struct alloc_tag *tag = ct_to_alloc_tag(ref->ct);
+
+ __lazy_percpu_counter_add(&tag->call_count, &tag->last_wrap, -1);
+ __lazy_percpu_counter_add(&tag->bytes_allocated, &tag->last_wrap, -bytes);
+ ref->ct = NULL;
+}
+
+#define alloc_tag_sub(_ref, _bytes) \
+do { \
+ if ((_ref) && (_ref)->ct) \
+ __alloc_tag_sub(_ref, _bytes); \
+} while (0)
+
+static inline void __alloc_tag_add(struct alloc_tag *tag, union codetag_ref *ref, size_t bytes)
+{
+ ref->ct = &tag->ct;
+ __lazy_percpu_counter_add(&tag->call_count, &tag->last_wrap, 1);
+ __lazy_percpu_counter_add(&tag->bytes_allocated, &tag->last_wrap, bytes);
+}
+
+#define alloc_tag_add(_ref, _bytes) \
+do { \
+ DEFINE_ALLOC_TAG(_alloc_tag); \
+ if (_ref && !WARN_ONCE(_ref->ct, "alloc_tag was not cleared")) \
+ __alloc_tag_add(&_alloc_tag, _ref, _bytes); \
+} while (0)
+
+#endif /* _LINUX_ALLOC_TAG_H */
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 22bc1eff7f8f..795bf6993f8a 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -973,6 +973,11 @@ config CODE_TAGGING
bool
select KALLSYMS

+config ALLOC_TAGGING
+ bool
+ select CODE_TAGGING
+ select LAZY_PERCPU_COUNTER
+
source "lib/Kconfig.kasan"
source "lib/Kconfig.kfence"

diff --git a/lib/Makefile b/lib/Makefile
index 574d7716e640..dc00533fc5c8 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -228,6 +228,8 @@ obj-$(CONFIG_OF_RECONFIG_NOTIFIER_ERROR_INJECT) += \
obj-$(CONFIG_FUNCTION_ERROR_INJECTION) += error-inject.o

obj-$(CONFIG_CODE_TAGGING) += codetag.o
+obj-$(CONFIG_ALLOC_TAGGING) += alloc_tag.o
+
lib-$(CONFIG_GENERIC_BUG) += bug.o

obj-$(CONFIG_HAVE_ARCH_TRACEHOOK) += syscall.o
diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
new file mode 100644
index 000000000000..082fbde184ef
--- /dev/null
+++ b/lib/alloc_tag.c
@@ -0,0 +1,158 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/alloc_tag.h>
+#include <linux/debugfs.h>
+#include <linux/fs.h>
+#include <linux/gfp.h>
+#include <linux/module.h>
+#include <linux/seq_buf.h>
+#include <linux/uaccess.h>
+
+#ifdef CONFIG_DEBUG_FS
+
+struct alloc_tag_file_iterator {
+ struct codetag_iterator ct_iter;
+ struct seq_buf buf;
+ char rawbuf[4096];
+};
+
+struct user_buf {
+ char __user *buf; /* destination user buffer */
+ size_t size; /* size of requested read */
+ ssize_t ret; /* bytes read so far */
+};
+
+static int flush_ubuf(struct user_buf *dst, struct seq_buf *src)
+{
+ if (src->len) {
+ size_t bytes = min_t(size_t, src->len, dst->size);
+ int err = copy_to_user(dst->buf, src->buffer, bytes);
+
+ if (err)
+ return err;
+
+ dst->ret += bytes;
+ dst->buf += bytes;
+ dst->size -= bytes;
+ src->len -= bytes;
+ memmove(src->buffer, src->buffer + bytes, src->len);
+ }
+
+ return 0;
+}
+
+static int alloc_tag_file_open(struct inode *inode, struct file *file)
+{
+ struct codetag_type *cttype = inode->i_private;
+ struct alloc_tag_file_iterator *iter;
+
+ iter = kzalloc(sizeof(*iter), GFP_KERNEL);
+ if (!iter)
+ return -ENOMEM;
+
+ codetag_lock_module_list(cttype, true);
+ iter->ct_iter = codetag_get_ct_iter(cttype);
+ codetag_lock_module_list(cttype, false);
+ seq_buf_init(&iter->buf, iter->rawbuf, sizeof(iter->rawbuf));
+ file->private_data = iter;
+
+ return 0;
+}
+
+static int alloc_tag_file_release(struct inode *inode, struct file *file)
+{
+ struct alloc_tag_file_iterator *iter = file->private_data;
+
+ kfree(iter);
+ return 0;
+}
+
+static void alloc_tag_to_text(struct seq_buf *out, struct codetag *ct)
+{
+ struct alloc_tag *tag = ct_to_alloc_tag(ct);
+ char buf[10];
+
+ string_get_size(alloc_tag_counter_read(&tag->bytes_allocated), 1,
+ STRING_UNITS_2, buf, sizeof(buf));
+
+ seq_buf_printf(out, "%8s %8lld ", buf, alloc_tag_counter_read(&tag->call_count));
+ codetag_to_text(out, ct);
+ seq_buf_putc(out, '\n');
+}
+
+static ssize_t alloc_tag_file_read(struct file *file, char __user *ubuf,
+ size_t size, loff_t *ppos)
+{
+ struct alloc_tag_file_iterator *iter = file->private_data;
+ struct user_buf buf = { .buf = ubuf, .size = size };
+ struct codetag *ct;
+ int err = 0;
+
+ codetag_lock_module_list(iter->ct_iter.cttype, true);
+ while (1) {
+ err = flush_ubuf(&buf, &iter->buf);
+ if (err || !buf.size)
+ break;
+
+ ct = codetag_next_ct(&iter->ct_iter);
+ if (!ct)
+ break;
+
+ alloc_tag_to_text(&iter->buf, ct);
+ }
+ codetag_lock_module_list(iter->ct_iter.cttype, false);
+
+ return err ? : buf.ret;
+}
+
+static const struct file_operations alloc_tag_file_ops = {
+ .owner = THIS_MODULE,
+ .open = alloc_tag_file_open,
+ .release = alloc_tag_file_release,
+ .read = alloc_tag_file_read,
+};
+
+static int dbgfs_init(struct codetag_type *cttype)
+{
+ struct dentry *file;
+
+ file = debugfs_create_file("alloc_tags", 0444, NULL, cttype,
+ &alloc_tag_file_ops);
+
+ return IS_ERR(file) ? PTR_ERR(file) : 0;
+}
+
+#else /* CONFIG_DEBUG_FS */
+
+static int dbgfs_init(struct codetag_type *) { return 0; }
+
+#endif /* CONFIG_DEBUG_FS */
+
+static void alloc_tag_module_unload(struct codetag_type *cttype, struct codetag_module *cmod)
+{
+ struct codetag_iterator iter = codetag_get_ct_iter(cttype);
+ struct codetag *ct;
+
+ for (ct = codetag_next_ct(&iter); ct; ct = codetag_next_ct(&iter)) {
+ struct alloc_tag *tag = ct_to_alloc_tag(ct);
+
+ __lazy_percpu_counter_exit(&tag->call_count);
+ __lazy_percpu_counter_exit(&tag->bytes_allocated);
+ }
+}
+
+static int __init alloc_tag_init(void)
+{
+ struct codetag_type *cttype;
+ const struct codetag_type_desc desc = {
+ .section = "alloc_tags",
+ .tag_size = sizeof(struct alloc_tag),
+ .module_unload = alloc_tag_module_unload,
+ };
+
+ cttype = codetag_register_type(&desc);
+ if (IS_ERR_OR_NULL(cttype))
+ return PTR_ERR(cttype);
+
+ return dbgfs_init(cttype);
+}
+module_init(alloc_tag_init);
diff --git a/scripts/module.lds.S b/scripts/module.lds.S
index 3a3aa2354ed8..e73a8781f239 100644
--- a/scripts/module.lds.S
+++ b/scripts/module.lds.S
@@ -12,6 +12,8 @@
# define SANITIZER_DISCARDS
#endif

+#include <asm-generic/codetag.lds.h>
+
SECTIONS {
/DISCARD/ : {
*(.discard)
@@ -47,6 +49,7 @@ SECTIONS {
.data : {
*(.data .data.[0-9a-zA-Z_]*)
*(.data..L*)
+ CODETAG_SECTIONS()
}

.rodata : {
@@ -62,6 +65,10 @@ SECTIONS {
*(.text.__cfi_check)
*(.text .text.[0-9a-zA-Z_]* .text..L.cfi*)
}
+#else
+ .data : {
+ CODETAG_SECTIONS()
+ }
#endif
}

--
2.37.2.672.g94769d06f0-goog