[PATCH v11 00/12] fprobe: Introduce fprobe function entry/exit probe

[PATCH v11 00/12] fprobe: Introduce fprobe function entry/exit probe

[Masami Hiramatsu]

Hi,

Here is the 11th version of fprobe. This version fixes some issues reported by
build bots (Thanks!) and rebased on bpf-next tree.

The previous version (v10) is here[1];

[1] https://lore.kernel.org/all/164673771096.1984170.8155877393151850116.stgit@devnote2/T/#u

This series introduces the fprobe, the function entry/exit probe
with multiple probe point support for x86, arm64 and powerpc64le.
This also introduces the rethook for hooking function return as same as
the kretprobe does. This abstraction will help us to generalize the fgraph
tracer, because we can just switch to it from the rethook in fprobe,
depending on the kernel configuration.

The patch [1/12] is from Jiri's series[2].

[2] https://lore.kernel.org/all/20220104080943.113249-1-jolsa@kernel.org/T/#u

And the patch [9/10] adds the FPROBE_FL_KPROBE_SHARED flag for the case
if user wants to share the same code (or share a same resource) on the
fprobe and the kprobes.

I forcibly updated my kprobes/fprobe branch, you can pull this series
from:

 https://git.kernel.org/pub/scm/linux/kernel/git/mhiramat/linux.git kprobes/fprobe

Thank you,

---

Jiri Olsa (1):
      ftrace: Add ftrace_set_filter_ips function

Masami Hiramatsu (11):
      fprobe: Add ftrace based probe APIs
      rethook: Add a generic return hook
      rethook: x86: Add rethook x86 implementation
      arm64: rethook: Add arm64 rethook implementation
      powerpc: Add rethook support
      ARM: rethook: Add rethook arm implementation
      fprobe: Add exit_handler support
      fprobe: Add sample program for fprobe
      fprobe: Introduce FPROBE_FL_KPROBE_SHARED flag for fprobe
      docs: fprobe: Add fprobe description to ftrace-use.rst
      fprobe: Add a selftest for fprobe


 Documentation/trace/fprobe.rst                |  171 +++++++++++++
 Documentation/trace/index.rst                 |    1 
 arch/arm/Kconfig                              |    1 
 arch/arm/include/asm/stacktrace.h             |    4 
 arch/arm/kernel/stacktrace.c                  |    6 
 arch/arm/probes/Makefile                      |    1 
 arch/arm/probes/rethook.c                     |  101 ++++++++
 arch/arm64/Kconfig                            |    1 
 arch/arm64/include/asm/stacktrace.h           |    2 
 arch/arm64/kernel/probes/Makefile             |    1 
 arch/arm64/kernel/probes/rethook.c            |   25 ++
 arch/arm64/kernel/probes/rethook_trampoline.S |   87 +++++++
 arch/arm64/kernel/stacktrace.c                |    7 -
 arch/powerpc/Kconfig                          |    1 
 arch/powerpc/kernel/Makefile                  |    1 
 arch/powerpc/kernel/rethook.c                 |   72 +++++
 arch/x86/Kconfig                              |    1 
 arch/x86/include/asm/unwind.h                 |    8 +
 arch/x86/kernel/Makefile                      |    1 
 arch/x86/kernel/kprobes/common.h              |    1 
 arch/x86/kernel/rethook.c                     |  119 +++++++++
 include/linux/fprobe.h                        |  105 ++++++++
 include/linux/ftrace.h                        |    3 
 include/linux/kprobes.h                       |    3 
 include/linux/rethook.h                       |  100 ++++++++
 include/linux/sched.h                         |    3 
 kernel/exit.c                                 |    2 
 kernel/fork.c                                 |    3 
 kernel/trace/Kconfig                          |   26 ++
 kernel/trace/Makefile                         |    2 
 kernel/trace/fprobe.c                         |  332 +++++++++++++++++++++++++
 kernel/trace/ftrace.c                         |   58 ++++
 kernel/trace/rethook.c                        |  317 ++++++++++++++++++++++++
 lib/Kconfig.debug                             |   12 +
 lib/Makefile                                  |    2 
 lib/test_fprobe.c                             |  174 +++++++++++++
 samples/Kconfig                               |    7 +
 samples/Makefile                              |    1 
 samples/fprobe/Makefile                       |    3 
 samples/fprobe/fprobe_example.c               |  120 +++++++++
 40 files changed, 1871 insertions(+), 14 deletions(-)
 create mode 100644 Documentation/trace/fprobe.rst
 create mode 100644 arch/arm/probes/rethook.c
 create mode 100644 arch/arm64/kernel/probes/rethook.c
 create mode 100644 arch/arm64/kernel/probes/rethook_trampoline.S
 create mode 100644 arch/powerpc/kernel/rethook.c
 create mode 100644 arch/x86/kernel/rethook.c
 create mode 100644 include/linux/fprobe.h
 create mode 100644 include/linux/rethook.h
 create mode 100644 kernel/trace/fprobe.c
 create mode 100644 kernel/trace/rethook.c
 create mode 100644 lib/test_fprobe.c
 create mode 100644 samples/fprobe/Makefile
 create mode 100644 samples/fprobe/fprobe_example.c

--
Masami Hiramatsu (Linaro) <mhiramat@kernel.org>

[PATCH v11 01/12] ftrace: Add ftrace_set_filter_ips function

[Masami Hiramatsu]

From: Jiri Olsa <jolsa@redhat.com>

Adding ftrace_set_filter_ips function to be able to set filter on
multiple ip addresses at once.

With the kprobe multi attach interface we have cases where we need to
initialize ftrace_ops object with thousands of functions, so having
single function diving into ftrace_hash_move_and_update_ops with
ftrace_lock is faster.

The functions ips are passed as unsigned long array with count.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 Changes in v6: [Masami]
  - Fix a typo and add a comment.
---
 include/linux/ftrace.h |    3 ++
 kernel/trace/ftrace.c  |   58 +++++++++++++++++++++++++++++++++++++++++-------
 2 files changed, 52 insertions(+), 9 deletions(-)

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 9999e29187de..60847cbce0da 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -512,6 +512,8 @@ struct dyn_ftrace {
 
 int ftrace_set_filter_ip(struct ftrace_ops *ops, unsigned long ip,
 			 int remove, int reset);
+int ftrace_set_filter_ips(struct ftrace_ops *ops, unsigned long *ips,
+			  unsigned int cnt, int remove, int reset);
 int ftrace_set_filter(struct ftrace_ops *ops, unsigned char *buf,
 		       int len, int reset);
 int ftrace_set_notrace(struct ftrace_ops *ops, unsigned char *buf,
@@ -802,6 +804,7 @@ static inline unsigned long ftrace_location(unsigned long ip)
 #define ftrace_regex_open(ops, flag, inod, file) ({ -ENODEV; })
 #define ftrace_set_early_filter(ops, buf, enable) do { } while (0)
 #define ftrace_set_filter_ip(ops, ip, remove, reset) ({ -ENODEV; })
+#define ftrace_set_filter_ips(ops, ips, cnt, remove, reset) ({ -ENODEV; })
 #define ftrace_set_filter(ops, buf, len, reset) ({ -ENODEV; })
 #define ftrace_set_notrace(ops, buf, len, reset) ({ -ENODEV; })
 #define ftrace_free_filter(ops) do { } while (0)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index a4b462b6f944..93e992962ada 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -4958,7 +4958,7 @@ ftrace_notrace_write(struct file *file, const char __user *ubuf,
 }
 
 static int
-ftrace_match_addr(struct ftrace_hash *hash, unsigned long ip, int remove)
+__ftrace_match_addr(struct ftrace_hash *hash, unsigned long ip, int remove)
 {
 	struct ftrace_func_entry *entry;
 
@@ -4976,9 +4976,30 @@ ftrace_match_addr(struct ftrace_hash *hash, unsigned long ip, int remove)
 	return add_hash_entry(hash, ip);
 }
 
+static int
+ftrace_match_addr(struct ftrace_hash *hash, unsigned long *ips,
+		  unsigned int cnt, int remove)
+{
+	unsigned int i;
+	int err;
+
+	for (i = 0; i < cnt; i++) {
+		err = __ftrace_match_addr(hash, ips[i], remove);
+		if (err) {
+			/*
+			 * This expects the @hash is a temporary hash and if this
+			 * fails the caller must free the @hash.
+			 */
+			return err;
+		}
+	}
+	return 0;
+}
+
 static int
 ftrace_set_hash(struct ftrace_ops *ops, unsigned char *buf, int len,
-		unsigned long ip, int remove, int reset, int enable)
+		unsigned long *ips, unsigned int cnt,
+		int remove, int reset, int enable)
 {
 	struct ftrace_hash **orig_hash;
 	struct ftrace_hash *hash;
@@ -5008,8 +5029,8 @@ ftrace_set_hash(struct ftrace_ops *ops, unsigned char *buf, int len,
 		ret = -EINVAL;
 		goto out_regex_unlock;
 	}
-	if (ip) {
-		ret = ftrace_match_addr(hash, ip, remove);
+	if (ips) {
+		ret = ftrace_match_addr(hash, ips, cnt, remove);
 		if (ret < 0)
 			goto out_regex_unlock;
 	}
@@ -5026,10 +5047,10 @@ ftrace_set_hash(struct ftrace_ops *ops, unsigned char *buf, int len,
 }
 
 static int
-ftrace_set_addr(struct ftrace_ops *ops, unsigned long ip, int remove,
-		int reset, int enable)
+ftrace_set_addr(struct ftrace_ops *ops, unsigned long *ips, unsigned int cnt,
+		int remove, int reset, int enable)
 {
-	return ftrace_set_hash(ops, NULL, 0, ip, remove, reset, enable);
+	return ftrace_set_hash(ops, NULL, 0, ips, cnt, remove, reset, enable);
 }
 
 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
@@ -5634,10 +5655,29 @@ int ftrace_set_filter_ip(struct ftrace_ops *ops, unsigned long ip,
 			 int remove, int reset)
 {
 	ftrace_ops_init(ops);
-	return ftrace_set_addr(ops, ip, remove, reset, 1);
+	return ftrace_set_addr(ops, &ip, 1, remove, reset, 1);
 }
 EXPORT_SYMBOL_GPL(ftrace_set_filter_ip);
 
+/**
+ * ftrace_set_filter_ips - set functions to filter on in ftrace by addresses
+ * @ops - the ops to set the filter with
+ * @ips - the array of addresses to add to or remove from the filter.
+ * @cnt - the number of addresses in @ips
+ * @remove - non zero to remove ips from the filter
+ * @reset - non zero to reset all filters before applying this filter.
+ *
+ * Filters denote which functions should be enabled when tracing is enabled
+ * If @ips array or any ip specified within is NULL , it fails to update filter.
+ */
+int ftrace_set_filter_ips(struct ftrace_ops *ops, unsigned long *ips,
+			  unsigned int cnt, int remove, int reset)
+{
+	ftrace_ops_init(ops);
+	return ftrace_set_addr(ops, ips, cnt, remove, reset, 1);
+}
+EXPORT_SYMBOL_GPL(ftrace_set_filter_ips);
+
 /**
  * ftrace_ops_set_global_filter - setup ops to use global filters
  * @ops - the ops which will use the global filters
@@ -5659,7 +5699,7 @@ static int
 ftrace_set_regex(struct ftrace_ops *ops, unsigned char *buf, int len,
 		 int reset, int enable)
 {
-	return ftrace_set_hash(ops, buf, len, 0, 0, reset, enable);
+	return ftrace_set_hash(ops, buf, len, NULL, 0, 0, reset, enable);
 }
 
 /**

[PATCH v11 02/12] fprobe: Add ftrace based probe APIs

[Masami Hiramatsu]

The fprobe is a wrapper API for ftrace function tracer.
Unlike kprobes, this probes only supports the function entry, but this
can probe multiple functions by one fprobe. The usage is similar, user
will set their callback to fprobe::entry_handler and call
register_fprobe*() with probed functions.
There are 3 registration interfaces,

 - register_fprobe() takes filtering patterns of the functin names.
 - register_fprobe_ips() takes an array of ftrace-location addresses.
 - register_fprobe_syms() takes an array of function names.

The registered fprobes can be unregistered with unregister_fprobe().
e.g.

struct fprobe fp = { .entry_handler = user_handler };
const char *targets[] = { "func1", "func2", "func3"};
...

ret = register_fprobe_syms(&fp, targets, ARRAY_SIZE(targets));

...

unregister_fprobe(&fp);

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 Changes in v10:
  - Simplify the loops in get_ftrace_locations() (Thanks Jiri!)
 Changes in v9:
  - Return an error if fprobe can not get the address or size of given
    symbol from kallsyms.
  - Use register_fprobe_ips() from register_fprobe_syms().
 Changes in v8:
  - Remove ftrace_ops if CONFIG_FUNCTION_TRACER=n.
 Changes in v7:
  - Fix kerneldoc for the APIs.
 Changes in v6:
  - Remove syms, addrs, and nentry fields from struct fprobe.
  - Introduce 3 variants of registration functions.
  - Call ftrace_free_filter() at unregistration.

 Changes in v4:
  - Fix a memory leak when symbol lookup failed.
  - Use ftrace location address instead of symbol address.
  - Convert the given symbol address to ftrace location automatically.
  - Rename fprobe::ftrace to fprobe::ops.
  - Update the Kconfig description.
---
 include/linux/fprobe.h |   87 ++++++++++++++++++++
 kernel/trace/Kconfig   |   12 +++
 kernel/trace/Makefile  |    1 
 kernel/trace/fprobe.c  |  211 ++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 311 insertions(+)
 create mode 100644 include/linux/fprobe.h
 create mode 100644 kernel/trace/fprobe.c

diff --git a/include/linux/fprobe.h b/include/linux/fprobe.h
new file mode 100644
index 000000000000..2ba099aff041
--- /dev/null
+++ b/include/linux/fprobe.h
@@ -0,0 +1,87 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Simple ftrace probe wrapper */
+#ifndef _LINUX_FPROBE_H
+#define _LINUX_FPROBE_H
+
+#include <linux/compiler.h>
+#include <linux/ftrace.h>
+
+/**
+ * struct fprobe - ftrace based probe.
+ * @ops: The ftrace_ops.
+ * @nmissed: The counter for missing events.
+ * @flags: The status flag.
+ * @entry_handler: The callback function for function entry.
+ */
+struct fprobe {
+#ifdef CONFIG_FUNCTION_TRACER
+	/*
+	 * If CONFIG_FUNCTION_TRACER is not set, CONFIG_FPROBE is disabled too.
+	 * But user of fprobe may keep embedding the struct fprobe on their own
+	 * code. To avoid build error, this will keep the fprobe data structure
+	 * defined here, but remove ftrace_ops data structure.
+	 */
+	struct ftrace_ops	ops;
+#endif
+	unsigned long		nmissed;
+	unsigned int		flags;
+	void (*entry_handler)(struct fprobe *fp, unsigned long entry_ip, struct pt_regs *regs);
+};
+
+#define FPROBE_FL_DISABLED	1
+
+static inline bool fprobe_disabled(struct fprobe *fp)
+{
+	return (fp) ? fp->flags & FPROBE_FL_DISABLED : false;
+}
+
+#ifdef CONFIG_FPROBE
+int register_fprobe(struct fprobe *fp, const char *filter, const char *notfilter);
+int register_fprobe_ips(struct fprobe *fp, unsigned long *addrs, int num);
+int register_fprobe_syms(struct fprobe *fp, const char **syms, int num);
+int unregister_fprobe(struct fprobe *fp);
+#else
+static inline int register_fprobe(struct fprobe *fp, const char *filter, const char *notfilter)
+{
+	return -EOPNOTSUPP;
+}
+static inline int register_fprobe_ips(struct fprobe *fp, unsigned long *addrs, int num)
+{
+	return -EOPNOTSUPP;
+}
+static inline int register_fprobe_syms(struct fprobe *fp, const char **syms, int num)
+{
+	return -EOPNOTSUPP;
+}
+static inline int unregister_fprobe(struct fprobe *fp)
+{
+	return -EOPNOTSUPP;
+}
+#endif
+
+/**
+ * disable_fprobe() - Disable fprobe
+ * @fp: The fprobe to be disabled.
+ *
+ * This will soft-disable @fp. Note that this doesn't remove the ftrace
+ * hooks from the function entry.
+ */
+static inline void disable_fprobe(struct fprobe *fp)
+{
+	if (fp)
+		fp->flags |= FPROBE_FL_DISABLED;
+}
+
+/**
+ * enable_fprobe() - Enable fprobe
+ * @fp: The fprobe to be enabled.
+ *
+ * This will soft-enable @fp.
+ */
+static inline void enable_fprobe(struct fprobe *fp)
+{
+	if (fp)
+		fp->flags &= ~FPROBE_FL_DISABLED;
+}
+
+#endif
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index a5eb5e7fd624..7ce31abc542b 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -236,6 +236,18 @@ config DYNAMIC_FTRACE_WITH_ARGS
 	depends on DYNAMIC_FTRACE
 	depends on HAVE_DYNAMIC_FTRACE_WITH_ARGS
 
+config FPROBE
+	bool "Kernel Function Probe (fprobe)"
+	depends on FUNCTION_TRACER
+	depends on DYNAMIC_FTRACE_WITH_REGS
+	default n
+	help
+	  This option enables kernel function probe (fprobe) based on ftrace,
+	  which is similar to kprobes, but probes only for kernel function
+	  entries and it can probe multiple functions by one fprobe.
+
+	  If unsure, say N.
+
 config FUNCTION_PROFILER
 	bool "Kernel function profiler"
 	depends on FUNCTION_TRACER
diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index bedc5caceec7..79255f9de9a4 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -97,6 +97,7 @@ obj-$(CONFIG_PROBE_EVENTS) += trace_probe.o
 obj-$(CONFIG_UPROBE_EVENTS) += trace_uprobe.o
 obj-$(CONFIG_BOOTTIME_TRACING) += trace_boot.o
 obj-$(CONFIG_FTRACE_RECORD_RECURSION) += trace_recursion_record.o
+obj-$(CONFIG_FPROBE) += fprobe.o
 
 obj-$(CONFIG_TRACEPOINT_BENCHMARK) += trace_benchmark.o
 
diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
new file mode 100644
index 000000000000..7e8ceee339a0
--- /dev/null
+++ b/kernel/trace/fprobe.c
@@ -0,0 +1,211 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * fprobe - Simple ftrace probe wrapper for function entry.
+ */
+#define pr_fmt(fmt) "fprobe: " fmt
+
+#include <linux/err.h>
+#include <linux/fprobe.h>
+#include <linux/kallsyms.h>
+#include <linux/kprobes.h>
+#include <linux/slab.h>
+#include <linux/sort.h>
+
+static void fprobe_handler(unsigned long ip, unsigned long parent_ip,
+			   struct ftrace_ops *ops, struct ftrace_regs *fregs)
+{
+	struct fprobe *fp;
+	int bit;
+
+	fp = container_of(ops, struct fprobe, ops);
+	if (fprobe_disabled(fp))
+		return;
+
+	bit = ftrace_test_recursion_trylock(ip, parent_ip);
+	if (bit < 0) {
+		fp->nmissed++;
+		return;
+	}
+
+	if (fp->entry_handler)
+		fp->entry_handler(fp, ip, ftrace_get_regs(fregs));
+
+	ftrace_test_recursion_unlock(bit);
+}
+NOKPROBE_SYMBOL(fprobe_handler);
+
+/* Convert ftrace location address from symbols */
+static unsigned long *get_ftrace_locations(const char **syms, int num)
+{
+	unsigned long addr, size;
+	unsigned long *addrs;
+	int i;
+
+	/* Convert symbols to symbol address */
+	addrs = kcalloc(num, sizeof(*addrs), GFP_KERNEL);
+	if (!addrs)
+		return ERR_PTR(-ENOMEM);
+
+	for (i = 0; i < num; i++) {
+		addr = kallsyms_lookup_name(syms[i]);
+		if (!addr)	/* Maybe wrong symbol */
+			goto error;
+
+		/* Convert symbol address to ftrace location. */
+		if (!kallsyms_lookup_size_offset(addr, &size, NULL) || !size)
+			goto error;
+
+		addr = ftrace_location_range(addr, addr + size - 1);
+		if (!addr) /* No dynamic ftrace there. */
+			goto error;
+
+		addrs[i] = addr;
+	}
+
+	return addrs;
+
+error:
+	kfree(addrs);
+
+	return ERR_PTR(-ENOENT);
+}
+
+static void fprobe_init(struct fprobe *fp)
+{
+	fp->nmissed = 0;
+	fp->ops.func = fprobe_handler;
+	fp->ops.flags |= FTRACE_OPS_FL_SAVE_REGS;
+}
+
+/**
+ * register_fprobe() - Register fprobe to ftrace by pattern.
+ * @fp: A fprobe data structure to be registered.
+ * @filter: A wildcard pattern of probed symbols.
+ * @notfilter: A wildcard pattern of NOT probed symbols.
+ *
+ * Register @fp to ftrace for enabling the probe on the symbols matched to @filter.
+ * If @notfilter is not NULL, the symbols matched the @notfilter are not probed.
+ *
+ * Return 0 if @fp is registered successfully, -errno if not.
+ */
+int register_fprobe(struct fprobe *fp, const char *filter, const char *notfilter)
+{
+	unsigned char *str;
+	int ret, len;
+
+	if (!fp || !filter)
+		return -EINVAL;
+
+	fprobe_init(fp);
+
+	len = strlen(filter);
+	str = kstrdup(filter, GFP_KERNEL);
+	ret = ftrace_set_filter(&fp->ops, str, len, 0);
+	kfree(str);
+	if (ret)
+		return ret;
+
+	if (notfilter) {
+		len = strlen(notfilter);
+		str = kstrdup(notfilter, GFP_KERNEL);
+		ret = ftrace_set_notrace(&fp->ops, str, len, 0);
+		kfree(str);
+		if (ret)
+			goto out;
+	}
+
+	ret = register_ftrace_function(&fp->ops);
+out:
+	if (ret)
+		ftrace_free_filter(&fp->ops);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(register_fprobe);
+
+/**
+ * register_fprobe_ips() - Register fprobe to ftrace by address.
+ * @fp: A fprobe data structure to be registered.
+ * @addrs: An array of target ftrace location addresses.
+ * @num: The number of entries of @addrs.
+ *
+ * Register @fp to ftrace for enabling the probe on the address given by @addrs.
+ * The @addrs must be the addresses of ftrace location address, which may be
+ * the symbol address + arch-dependent offset.
+ * If you unsure what this mean, please use other registration functions.
+ *
+ * Return 0 if @fp is registered successfully, -errno if not.
+ */
+int register_fprobe_ips(struct fprobe *fp, unsigned long *addrs, int num)
+{
+	int ret;
+
+	if (!fp || !addrs || num <= 0)
+		return -EINVAL;
+
+	fprobe_init(fp);
+
+	ret = ftrace_set_filter_ips(&fp->ops, addrs, num, 0, 0);
+	if (!ret)
+		ret = register_ftrace_function(&fp->ops);
+
+	if (ret)
+		ftrace_free_filter(&fp->ops);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(register_fprobe_ips);
+
+/**
+ * register_fprobe_syms() - Register fprobe to ftrace by symbols.
+ * @fp: A fprobe data structure to be registered.
+ * @syms: An array of target symbols.
+ * @num: The number of entries of @syms.
+ *
+ * Register @fp to the symbols given by @syms array. This will be useful if
+ * you are sure the symbols exist in the kernel.
+ *
+ * Return 0 if @fp is registered successfully, -errno if not.
+ */
+int register_fprobe_syms(struct fprobe *fp, const char **syms, int num)
+{
+	unsigned long *addrs;
+	int ret;
+
+	if (!fp || !syms || num <= 0)
+		return -EINVAL;
+
+	addrs = get_ftrace_locations(syms, num);
+	if (IS_ERR(addrs))
+		return PTR_ERR(addrs);
+
+	ret = register_fprobe_ips(fp, addrs, num);
+
+	kfree(addrs);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(register_fprobe_syms);
+
+/**
+ * unregister_fprobe() - Unregister fprobe from ftrace
+ * @fp: A fprobe data structure to be unregistered.
+ *
+ * Unregister fprobe (and remove ftrace hooks from the function entries).
+ *
+ * Return 0 if @fp is unregistered successfully, -errno if not.
+ */
+int unregister_fprobe(struct fprobe *fp)
+{
+	int ret;
+
+	if (!fp || fp->ops.func != fprobe_handler)
+		return -EINVAL;
+
+	ret = unregister_ftrace_function(&fp->ops);
+
+	if (!ret)
+		ftrace_free_filter(&fp->ops);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(unregister_fprobe);

[PATCH v11 03/12] rethook: Add a generic return hook

[Masami Hiramatsu]

Add a return hook framework which hooks the function return. Most of the
logic came from the kretprobe, but this is independent from kretprobe.

Note that this is expected to be used with other function entry hooking
feature, like ftrace, fprobe, adn kprobes. Eventually this will replace
the kretprobe (e.g. kprobe + rethook = kretprobe), but at this moment,
this is just an additional hook.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 Changes in v10:
  - Add @mcount parameter to rethook_hook() to identify the context.
 Changes in v6:
  - Fix typos.
  - Use dereference_symbol_descriptor() to check the trampoline address.
  - Shrink down the preempt-disabled section for recycling nodes.
  - Reject stack searching if the task is not current and is running in
    rethook_find_ret_addr().
 Changes in v4:
  - Fix rethook_trampoline_handler() loops as same as
    what currently kretprobe does.  This will fix some
    stacktrace issue in the rethook handler.
---
 include/linux/rethook.h |  100 +++++++++++++++
 include/linux/sched.h   |    3 
 kernel/exit.c           |    2 
 kernel/fork.c           |    3 
 kernel/trace/Kconfig    |   11 ++
 kernel/trace/Makefile   |    1 
 kernel/trace/rethook.c  |  317 +++++++++++++++++++++++++++++++++++++++++++++++
 7 files changed, 437 insertions(+)
 create mode 100644 include/linux/rethook.h
 create mode 100644 kernel/trace/rethook.c

diff --git a/include/linux/rethook.h b/include/linux/rethook.h
new file mode 100644
index 000000000000..c8ac1e5afcd1
--- /dev/null
+++ b/include/linux/rethook.h
@@ -0,0 +1,100 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Return hooking with list-based shadow stack.
+ */
+#ifndef _LINUX_RETHOOK_H
+#define _LINUX_RETHOOK_H
+
+#include <linux/compiler.h>
+#include <linux/freelist.h>
+#include <linux/kallsyms.h>
+#include <linux/llist.h>
+#include <linux/rcupdate.h>
+#include <linux/refcount.h>
+
+struct rethook_node;
+
+typedef void (*rethook_handler_t) (struct rethook_node *, void *, struct pt_regs *);
+
+/**
+ * struct rethook - The rethook management data structure.
+ * @data: The user-defined data storage.
+ * @handler: The user-defined return hook handler.
+ * @pool: The pool of struct rethook_node.
+ * @ref: The reference counter.
+ * @rcu: The rcu_head for deferred freeing.
+ *
+ * Don't embed to another data structure, because this is a self-destructive
+ * data structure when all rethook_node are freed.
+ */
+struct rethook {
+	void			*data;
+	rethook_handler_t	handler;
+	struct freelist_head	pool;
+	refcount_t		ref;
+	struct rcu_head		rcu;
+};
+
+/**
+ * struct rethook_node - The rethook shadow-stack entry node.
+ * @freelist: The freelist, linked to struct rethook::pool.
+ * @rcu: The rcu_head for deferred freeing.
+ * @llist: The llist, linked to a struct task_struct::rethooks.
+ * @rethook: The pointer to the struct rethook.
+ * @ret_addr: The storage for the real return address.
+ * @frame: The storage for the frame pointer.
+ *
+ * You can embed this to your extended data structure to store any data
+ * on each entry of the shadow stack.
+ */
+struct rethook_node {
+	union {
+		struct freelist_node freelist;
+		struct rcu_head      rcu;
+	};
+	struct llist_node	llist;
+	struct rethook		*rethook;
+	unsigned long		ret_addr;
+	unsigned long		frame;
+};
+
+struct rethook *rethook_alloc(void *data, rethook_handler_t handler);
+void rethook_free(struct rethook *rh);
+void rethook_add_node(struct rethook *rh, struct rethook_node *node);
+struct rethook_node *rethook_try_get(struct rethook *rh);
+void rethook_recycle(struct rethook_node *node);
+void rethook_hook(struct rethook_node *node, struct pt_regs *regs, bool mcount);
+unsigned long rethook_find_ret_addr(struct task_struct *tsk, unsigned long frame,
+				    struct llist_node **cur);
+
+/* Arch dependent code must implement arch_* and trampoline code */
+void arch_rethook_prepare(struct rethook_node *node, struct pt_regs *regs, bool mcount);
+void arch_rethook_trampoline(void);
+
+/**
+ * is_rethook_trampoline() - Check whether the address is rethook trampoline
+ * @addr: The address to be checked
+ *
+ * Return true if the @addr is the rethook trampoline address.
+ */
+static inline bool is_rethook_trampoline(unsigned long addr)
+{
+	return addr == (unsigned long)dereference_symbol_descriptor(arch_rethook_trampoline);
+}
+
+/* If the architecture needs to fixup the return address, implement it. */
+void arch_rethook_fixup_return(struct pt_regs *regs,
+			       unsigned long correct_ret_addr);
+
+/* Generic trampoline handler, arch code must prepare asm stub */
+unsigned long rethook_trampoline_handler(struct pt_regs *regs,
+					 unsigned long frame);
+
+#ifdef CONFIG_RETHOOK
+void rethook_flush_task(struct task_struct *tk);
+#else
+#define rethook_flush_task(tsk)	do { } while (0)
+#endif
+
+#endif
+
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 75ba8aa60248..7034f53404e3 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1481,6 +1481,9 @@ struct task_struct {
 #ifdef CONFIG_KRETPROBES
 	struct llist_head               kretprobe_instances;
 #endif
+#ifdef CONFIG_RETHOOK
+	struct llist_head               rethooks;
+#endif
 
 #ifdef CONFIG_ARCH_HAS_PARANOID_L1D_FLUSH
 	/*
diff --git a/kernel/exit.c b/kernel/exit.c
index b00a25bb4ab9..2d1803fa8fe6 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -64,6 +64,7 @@
 #include <linux/compat.h>
 #include <linux/io_uring.h>
 #include <linux/kprobes.h>
+#include <linux/rethook.h>
 
 #include <linux/uaccess.h>
 #include <asm/unistd.h>
@@ -169,6 +170,7 @@ static void delayed_put_task_struct(struct rcu_head *rhp)
 	struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
 
 	kprobe_flush_task(tsk);
+	rethook_flush_task(tsk);
 	perf_event_delayed_put(tsk);
 	trace_sched_process_free(tsk);
 	put_task_struct(tsk);
diff --git a/kernel/fork.c b/kernel/fork.c
index a024bf6254df..3db1a4110a25 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2255,6 +2255,9 @@ static __latent_entropy struct task_struct *copy_process(
 #ifdef CONFIG_KRETPROBES
 	p->kretprobe_instances.first = NULL;
 #endif
+#ifdef CONFIG_RETHOOK
+	p->rethooks.first = NULL;
+#endif
 
 	/*
 	 * Ensure that the cgroup subsystem policies allow the new process to be
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 7ce31abc542b..e75504e42ab8 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -10,6 +10,17 @@ config USER_STACKTRACE_SUPPORT
 config NOP_TRACER
 	bool
 
+config HAVE_RETHOOK
+	bool
+
+config RETHOOK
+	bool
+	depends on HAVE_RETHOOK
+	help
+	  Enable generic return hooking feature. This is an internal
+	  API, which will be used by other function-entry hooking
+	  features like fprobe and kprobes.
+
 config HAVE_FUNCTION_TRACER
 	bool
 	help
diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index 79255f9de9a4..c6f11a139eac 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -98,6 +98,7 @@ obj-$(CONFIG_UPROBE_EVENTS) += trace_uprobe.o
 obj-$(CONFIG_BOOTTIME_TRACING) += trace_boot.o
 obj-$(CONFIG_FTRACE_RECORD_RECURSION) += trace_recursion_record.o
 obj-$(CONFIG_FPROBE) += fprobe.o
+obj-$(CONFIG_RETHOOK) += rethook.o
 
 obj-$(CONFIG_TRACEPOINT_BENCHMARK) += trace_benchmark.o
 
diff --git a/kernel/trace/rethook.c b/kernel/trace/rethook.c
new file mode 100644
index 000000000000..ab463a4d2b23
--- /dev/null
+++ b/kernel/trace/rethook.c
@@ -0,0 +1,317 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#define pr_fmt(fmt) "rethook: " fmt
+
+#include <linux/bug.h>
+#include <linux/kallsyms.h>
+#include <linux/kprobes.h>
+#include <linux/preempt.h>
+#include <linux/rethook.h>
+#include <linux/slab.h>
+#include <linux/sort.h>
+
+/* Return hook list (shadow stack by list) */
+
+/*
+ * This function is called from delayed_put_task_struct() when a task is
+ * dead and cleaned up to recycle any kretprobe instances associated with
+ * this task. These left over instances represent probed functions that
+ * have been called but will never return.
+ */
+void rethook_flush_task(struct task_struct *tk)
+{
+	struct rethook_node *rhn;
+	struct llist_node *node;
+
+	node = __llist_del_all(&tk->rethooks);
+	while (node) {
+		rhn = container_of(node, struct rethook_node, llist);
+		node = node->next;
+		preempt_disable();
+		rethook_recycle(rhn);
+		preempt_enable();
+	}
+}
+
+static void rethook_free_rcu(struct rcu_head *head)
+{
+	struct rethook *rh = container_of(head, struct rethook, rcu);
+	struct rethook_node *rhn;
+	struct freelist_node *node;
+	int count = 1;
+
+	node = rh->pool.head;
+	while (node) {
+		rhn = container_of(node, struct rethook_node, freelist);
+		node = node->next;
+		kfree(rhn);
+		count++;
+	}
+
+	/* The rh->ref is the number of pooled node + 1 */
+	if (refcount_sub_and_test(count, &rh->ref))
+		kfree(rh);
+}
+
+/**
+ * rethook_free() - Free struct rethook.
+ * @rh: the struct rethook to be freed.
+ *
+ * Free the rethook. Before calling this function, user must ensure the
+ * @rh::data is cleaned if needed (or, the handler can access it after
+ * calling this function.) This function will set the @rh to be freed
+ * after all rethook_node are freed (not soon). And the caller must
+ * not touch @rh after calling this.
+ */
+void rethook_free(struct rethook *rh)
+{
+	rcu_assign_pointer(rh->handler, NULL);
+
+	call_rcu(&rh->rcu, rethook_free_rcu);
+}
+
+/**
+ * rethook_alloc() - Allocate struct rethook.
+ * @data: a data to pass the @handler when hooking the return.
+ * @handler: the return hook callback function.
+ *
+ * Allocate and initialize a new rethook with @data and @handler.
+ * Return NULL if memory allocation fails or @handler is NULL.
+ * Note that @handler == NULL means this rethook is going to be freed.
+ */
+struct rethook *rethook_alloc(void *data, rethook_handler_t handler)
+{
+	struct rethook *rh = kzalloc(sizeof(struct rethook), GFP_KERNEL);
+
+	if (!rh || !handler)
+		return NULL;
+
+	rh->data = data;
+	rh->handler = handler;
+	rh->pool.head = NULL;
+	refcount_set(&rh->ref, 1);
+
+	return rh;
+}
+
+/**
+ * rethook_add_node() - Add a new node to the rethook.
+ * @rh: the struct rethook.
+ * @node: the struct rethook_node to be added.
+ *
+ * Add @node to @rh. User must allocate @node (as a part of user's
+ * data structure.) The @node fields are initialized in this function.
+ */
+void rethook_add_node(struct rethook *rh, struct rethook_node *node)
+{
+	node->rethook = rh;
+	freelist_add(&node->freelist, &rh->pool);
+	refcount_inc(&rh->ref);
+}
+
+static void free_rethook_node_rcu(struct rcu_head *head)
+{
+	struct rethook_node *node = container_of(head, struct rethook_node, rcu);
+
+	if (refcount_dec_and_test(&node->rethook->ref))
+		kfree(node->rethook);
+	kfree(node);
+}
+
+/**
+ * rethook_recycle() - return the node to rethook.
+ * @node: The struct rethook_node to be returned.
+ *
+ * Return back the @node to @node::rethook. If the @node::rethook is already
+ * marked as freed, this will free the @node.
+ */
+void rethook_recycle(struct rethook_node *node)
+{
+	lockdep_assert_preemption_disabled();
+
+	if (likely(READ_ONCE(node->rethook->handler)))
+		freelist_add(&node->freelist, &node->rethook->pool);
+	else
+		call_rcu(&node->rcu, free_rethook_node_rcu);
+}
+NOKPROBE_SYMBOL(rethook_recycle);
+
+/**
+ * rethook_try_get() - get an unused rethook node.
+ * @rh: The struct rethook which pools the nodes.
+ *
+ * Get an unused rethook node from @rh. If the node pool is empty, this
+ * will return NULL. Caller must disable preemption.
+ */
+struct rethook_node *rethook_try_get(struct rethook *rh)
+{
+	rethook_handler_t handler = READ_ONCE(rh->handler);
+	struct freelist_node *fn;
+
+	lockdep_assert_preemption_disabled();
+
+	/* Check whether @rh is going to be freed. */
+	if (unlikely(!handler))
+		return NULL;
+
+	fn = freelist_try_get(&rh->pool);
+	if (!fn)
+		return NULL;
+
+	return container_of(fn, struct rethook_node, freelist);
+}
+NOKPROBE_SYMBOL(rethook_try_get);
+
+/**
+ * rethook_hook() - Hook the current function return.
+ * @node: The struct rethook node to hook the function return.
+ * @regs: The struct pt_regs for the function entry.
+ * @mcount: True if this is called from mcount(ftrace) context.
+ *
+ * Hook the current running function return. This must be called when the
+ * function entry (or at least @regs must be the registers of the function
+ * entry.) @mcount is used for identifying the context. If this is called
+ * from ftrace (mcount) callback, @mcount must be set true. If this is called
+ * from the real function entry (e.g. kprobes) @mcount must be set false.
+ * This is because the way to hook the function return depends on the context.
+ */
+void rethook_hook(struct rethook_node *node, struct pt_regs *regs, bool mcount)
+{
+	arch_rethook_prepare(node, regs, mcount);
+	__llist_add(&node->llist, &current->rethooks);
+}
+NOKPROBE_SYMBOL(rethook_hook);
+
+/* This assumes the 'tsk' is the current task or is not running. */
+static unsigned long __rethook_find_ret_addr(struct task_struct *tsk,
+					     struct llist_node **cur)
+{
+	struct rethook_node *rh = NULL;
+	struct llist_node *node = *cur;
+
+	if (!node)
+		node = tsk->rethooks.first;
+	else
+		node = node->next;
+
+	while (node) {
+		rh = container_of(node, struct rethook_node, llist);
+		if (rh->ret_addr != (unsigned long)arch_rethook_trampoline) {
+			*cur = node;
+			return rh->ret_addr;
+		}
+		node = node->next;
+	}
+	return 0;
+}
+NOKPROBE_SYMBOL(__rethook_find_ret_addr);
+
+/**
+ * rethook_find_ret_addr -- Find correct return address modified by rethook
+ * @tsk: Target task
+ * @frame: A frame pointer
+ * @cur: a storage of the loop cursor llist_node pointer for next call
+ *
+ * Find the correct return address modified by a rethook on @tsk in unsigned
+ * long type.
+ * The @tsk must be 'current' or a task which is not running. @frame is a hint
+ * to get the currect return address - which is compared with the
+ * rethook::frame field. The @cur is a loop cursor for searching the
+ * kretprobe return addresses on the @tsk. The '*@cur' should be NULL at the
+ * first call, but '@cur' itself must NOT NULL.
+ *
+ * Returns found address value or zero if not found.
+ */
+unsigned long rethook_find_ret_addr(struct task_struct *tsk, unsigned long frame,
+				    struct llist_node **cur)
+{
+	struct rethook_node *rhn = NULL;
+	unsigned long ret;
+
+	if (WARN_ON_ONCE(!cur))
+		return 0;
+
+	if (WARN_ON_ONCE(tsk != current && task_is_running(tsk)))
+		return 0;
+
+	do {
+		ret = __rethook_find_ret_addr(tsk, cur);
+		if (!ret)
+			break;
+		rhn = container_of(*cur, struct rethook_node, llist);
+	} while (rhn->frame != frame);
+
+	return ret;
+}
+NOKPROBE_SYMBOL(rethook_find_ret_addr);
+
+void __weak arch_rethook_fixup_return(struct pt_regs *regs,
+				      unsigned long correct_ret_addr)
+{
+	/*
+	 * Do nothing by default. If the architecture which uses a
+	 * frame pointer to record real return address on the stack,
+	 * it should fill this function to fixup the return address
+	 * so that stacktrace works from the rethook handler.
+	 */
+}
+
+/* This function will be called from each arch-defined trampoline. */
+unsigned long rethook_trampoline_handler(struct pt_regs *regs,
+					 unsigned long frame)
+{
+	struct llist_node *first, *node = NULL;
+	unsigned long correct_ret_addr;
+	rethook_handler_t handler;
+	struct rethook_node *rhn;
+
+	correct_ret_addr = __rethook_find_ret_addr(current, &node);
+	if (!correct_ret_addr) {
+		pr_err("rethook: Return address not found! Maybe there is a bug in the kernel\n");
+		BUG_ON(1);
+	}
+
+	instruction_pointer_set(regs, correct_ret_addr);
+
+	/*
+	 * These loops must be protected from rethook_free_rcu() because those
+	 * are accessing 'rhn->rethook'.
+	 */
+	preempt_disable();
+
+	/*
+	 * Run the handler on the shadow stack. Do not unlink the list here because
+	 * stackdump inside the handlers needs to decode it.
+	 */
+	first = current->rethooks.first;
+	while (first) {
+		rhn = container_of(first, struct rethook_node, llist);
+		if (WARN_ON_ONCE(rhn->frame != frame))
+			break;
+		handler = READ_ONCE(rhn->rethook->handler);
+		if (handler)
+			handler(rhn, rhn->rethook->data, regs);
+
+		if (first == node)
+			break;
+		first = first->next;
+	}
+
+	/* Fixup registers for returning to correct address. */
+	arch_rethook_fixup_return(regs, correct_ret_addr);
+
+	/* Unlink used shadow stack */
+	first = current->rethooks.first;
+	current->rethooks.first = node->next;
+	node->next = NULL;
+
+	while (first) {
+		rhn = container_of(first, struct rethook_node, llist);
+		first = first->next;
+		rethook_recycle(rhn);
+	}
+	preempt_enable();
+
+	return correct_ret_addr;
+}
+NOKPROBE_SYMBOL(rethook_trampoline_handler);

[PATCH v11 04/12] rethook: x86: Add rethook x86 implementation

[Masami Hiramatsu]

Add rethook for x86 implementation. Most of the code has been copied from
kretprobes on x86.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 Changes in v11:
  - Mark arch_rethook_fixup_return() as NOKPROBE_SYMBOL.
  - Add a function prototype of arch_rethook_trampoline_callback
    to suppress warning.
 Changes in v10:
  - Add a dummy @mcount to arch_rethook_prepare().
 Changes in v5:
  - Fix a build error if !CONFIG_KRETPROBES and !CONFIG_RETHOOK.
 Changes in v4:
  - fix stack backtrace as same as kretprobe does.
---
 arch/x86/Kconfig                 |    1 
 arch/x86/include/asm/unwind.h    |    8 ++-
 arch/x86/kernel/Makefile         |    1 
 arch/x86/kernel/kprobes/common.h |    1 
 arch/x86/kernel/rethook.c        |  119 ++++++++++++++++++++++++++++++++++++++
 5 files changed, 129 insertions(+), 1 deletion(-)
 create mode 100644 arch/x86/kernel/rethook.c

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 9b356da6f46b..1270b65a5546 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -221,6 +221,7 @@ config X86
 	select HAVE_KPROBES_ON_FTRACE
 	select HAVE_FUNCTION_ERROR_INJECTION
 	select HAVE_KRETPROBES
+	select HAVE_RETHOOK
 	select HAVE_KVM
 	select HAVE_LIVEPATCH			if X86_64
 	select HAVE_MIXED_BREAKPOINTS_REGS
diff --git a/arch/x86/include/asm/unwind.h b/arch/x86/include/asm/unwind.h
index 2a1f8734416d..192df5b2094d 100644
--- a/arch/x86/include/asm/unwind.h
+++ b/arch/x86/include/asm/unwind.h
@@ -5,6 +5,7 @@
 #include <linux/sched.h>
 #include <linux/ftrace.h>
 #include <linux/kprobes.h>
+#include <linux/rethook.h>
 #include <asm/ptrace.h>
 #include <asm/stacktrace.h>
 
@@ -16,7 +17,7 @@ struct unwind_state {
 	unsigned long stack_mask;
 	struct task_struct *task;
 	int graph_idx;
-#ifdef CONFIG_KRETPROBES
+#if defined(CONFIG_KRETPROBES) || defined(CONFIG_RETHOOK)
 	struct llist_node *kr_cur;
 #endif
 	bool error;
@@ -107,6 +108,11 @@ static inline
 unsigned long unwind_recover_kretprobe(struct unwind_state *state,
 				       unsigned long addr, unsigned long *addr_p)
 {
+#ifdef CONFIG_RETHOOK
+	if (is_rethook_trampoline(addr))
+		return rethook_find_ret_addr(state->task, (unsigned long)addr_p,
+					     &state->kr_cur);
+#endif
 #ifdef CONFIG_KRETPROBES
 	return is_kretprobe_trampoline(addr) ?
 		kretprobe_find_ret_addr(state->task, addr_p, &state->kr_cur) :
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 6aef9ee28a39..792a893a5cc5 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -106,6 +106,7 @@ obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += ftrace.o
 obj-$(CONFIG_FTRACE_SYSCALLS)	+= ftrace.o
 obj-$(CONFIG_X86_TSC)		+= trace_clock.o
 obj-$(CONFIG_TRACING)		+= trace.o
+obj-$(CONFIG_RETHOOK)		+= rethook.o
 obj-$(CONFIG_CRASH_CORE)	+= crash_core_$(BITS).o
 obj-$(CONFIG_KEXEC_CORE)	+= machine_kexec_$(BITS).o
 obj-$(CONFIG_KEXEC_CORE)	+= relocate_kernel_$(BITS).o crash.o
diff --git a/arch/x86/kernel/kprobes/common.h b/arch/x86/kernel/kprobes/common.h
index 7d3a2e2daf01..c993521d4933 100644
--- a/arch/x86/kernel/kprobes/common.h
+++ b/arch/x86/kernel/kprobes/common.h
@@ -6,6 +6,7 @@
 
 #include <asm/asm.h>
 #include <asm/frame.h>
+#include <asm/insn.h>
 
 #ifdef CONFIG_X86_64
 
diff --git a/arch/x86/kernel/rethook.c b/arch/x86/kernel/rethook.c
new file mode 100644
index 000000000000..f0f2f0608282
--- /dev/null
+++ b/arch/x86/kernel/rethook.c
@@ -0,0 +1,119 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * x86 implementation of rethook. Mostly copied from arch/x86/kernel/kprobes/core.c.
+ */
+#include <linux/bug.h>
+#include <linux/rethook.h>
+#include <linux/kprobes.h>
+
+#include "kprobes/common.h"
+
+__visible void arch_rethook_trampoline_callback(struct pt_regs *regs);
+
+/*
+ * When a target function returns, this code saves registers and calls
+ * arch_rethook_trampoline_callback(), which calls the rethook handler.
+ */
+asm(
+	".text\n"
+	".global arch_rethook_trampoline\n"
+	".type arch_rethook_trampoline, @function\n"
+	"arch_rethook_trampoline:\n"
+#ifdef CONFIG_X86_64
+	/* Push a fake return address to tell the unwinder it's a kretprobe. */
+	"	pushq $arch_rethook_trampoline\n"
+	UNWIND_HINT_FUNC
+	/* Save the 'sp - 8', this will be fixed later. */
+	"	pushq %rsp\n"
+	"	pushfq\n"
+	SAVE_REGS_STRING
+	"	movq %rsp, %rdi\n"
+	"	call arch_rethook_trampoline_callback\n"
+	RESTORE_REGS_STRING
+	/* In the callback function, 'regs->flags' is copied to 'regs->sp'. */
+	"	addq $8, %rsp\n"
+	"	popfq\n"
+#else
+	/* Push a fake return address to tell the unwinder it's a kretprobe. */
+	"	pushl $arch_rethook_trampoline\n"
+	UNWIND_HINT_FUNC
+	/* Save the 'sp - 4', this will be fixed later. */
+	"	pushl %esp\n"
+	"	pushfl\n"
+	SAVE_REGS_STRING
+	"	movl %esp, %eax\n"
+	"	call arch_rethook_trampoline_callback\n"
+	RESTORE_REGS_STRING
+	/* In the callback function, 'regs->flags' is copied to 'regs->sp'. */
+	"	addl $4, %esp\n"
+	"	popfl\n"
+#endif
+	"	ret\n"
+	".size arch_rethook_trampoline, .-arch_rethook_trampoline\n"
+);
+NOKPROBE_SYMBOL(arch_rethook_trampoline);
+
+/*
+ * Called from arch_rethook_trampoline
+ */
+__used __visible void arch_rethook_trampoline_callback(struct pt_regs *regs)
+{
+	unsigned long *frame_pointer;
+
+	/* fixup registers */
+	regs->cs = __KERNEL_CS;
+#ifdef CONFIG_X86_32
+	regs->gs = 0;
+#endif
+	regs->ip = (unsigned long)&arch_rethook_trampoline;
+	regs->orig_ax = ~0UL;
+	regs->sp += sizeof(long);
+	frame_pointer = &regs->sp + 1;
+
+	/*
+	 * The return address at 'frame_pointer' is recovered by the
+	 * arch_rethook_fixup_return() which called from this
+	 * rethook_trampoline_handler().
+	 */
+	rethook_trampoline_handler(regs, (unsigned long)frame_pointer);
+
+	/*
+	 * Copy FLAGS to 'pt_regs::sp' so that arch_rethook_trapmoline()
+	 * can do RET right after POPF.
+	 */
+	regs->sp = regs->flags;
+}
+NOKPROBE_SYMBOL(arch_rethook_trampoline_callback);
+
+/*
+ * arch_rethook_trampoline() skips updating frame pointer. The frame pointer
+ * saved in arch_rethook_trampoline_callback() points to the real caller
+ * function's frame pointer. Thus the arch_rethook_trampoline() doesn't have
+ * a standard stack frame with CONFIG_FRAME_POINTER=y.
+ * Let's mark it non-standard function. Anyway, FP unwinder can correctly
+ * unwind without the hint.
+ */
+STACK_FRAME_NON_STANDARD_FP(arch_rethook_trampoline);
+
+/* This is called from rethook_trampoline_handler(). */
+void arch_rethook_fixup_return(struct pt_regs *regs,
+			       unsigned long correct_ret_addr)
+{
+	unsigned long *frame_pointer = &regs->sp + 1;
+
+	/* Replace fake return address with real one. */
+	*frame_pointer = correct_ret_addr;
+}
+NOKPROBE_SYMBOL(arch_rethook_fixup_return);
+
+void arch_rethook_prepare(struct rethook_node *rh, struct pt_regs *regs, bool mcount)
+{
+	unsigned long *stack = (unsigned long *)regs->sp;
+
+	rh->ret_addr = stack[0];
+	rh->frame = regs->sp;
+
+	/* Replace the return addr with trampoline addr */
+	stack[0] = (unsigned long) arch_rethook_trampoline;
+}
+NOKPROBE_SYMBOL(arch_rethook_prepare);

[PATCH v11 05/12] arm64: rethook: Add arm64 rethook implementation

[Masami Hiramatsu]

Add rethook arm64 implementation. Most of the code has been copied from
kretprobes on arm64.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 Changes in v10:
  - Add a dummy @mcount to arch_rethook_prepare().
 Changes in v5:
  - Add description.
  - Fix build error if !CONFIG_KRETPROBES
---
 arch/arm64/Kconfig                            |    1 
 arch/arm64/include/asm/stacktrace.h           |    2 -
 arch/arm64/kernel/probes/Makefile             |    1 
 arch/arm64/kernel/probes/rethook.c            |   25 +++++++
 arch/arm64/kernel/probes/rethook_trampoline.S |   87 +++++++++++++++++++++++++
 arch/arm64/kernel/stacktrace.c                |    7 ++
 6 files changed, 121 insertions(+), 2 deletions(-)
 create mode 100644 arch/arm64/kernel/probes/rethook.c
 create mode 100644 arch/arm64/kernel/probes/rethook_trampoline.S

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 09b885cc4db5..62cff9d0a5bb 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -201,6 +201,7 @@ config ARM64
 	select HAVE_SYSCALL_TRACEPOINTS
 	select HAVE_KPROBES
 	select HAVE_KRETPROBES
+	select HAVE_RETHOOK
 	select HAVE_GENERIC_VDSO
 	select IOMMU_DMA if IOMMU_SUPPORT
 	select IRQ_DOMAIN
diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h
index e77cdef9ca29..bf04107da97c 100644
--- a/arch/arm64/include/asm/stacktrace.h
+++ b/arch/arm64/include/asm/stacktrace.h
@@ -58,7 +58,7 @@ struct stackframe {
 	DECLARE_BITMAP(stacks_done, __NR_STACK_TYPES);
 	unsigned long prev_fp;
 	enum stack_type prev_type;
-#ifdef CONFIG_KRETPROBES
+#if defined(CONFIG_KRETPROBES) || defined(CONFIG_RETHOOK)
 	struct llist_node *kr_cur;
 #endif
 };
diff --git a/arch/arm64/kernel/probes/Makefile b/arch/arm64/kernel/probes/Makefile
index 8e4be92e25b1..24e689f44c32 100644
--- a/arch/arm64/kernel/probes/Makefile
+++ b/arch/arm64/kernel/probes/Makefile
@@ -4,3 +4,4 @@ obj-$(CONFIG_KPROBES)		+= kprobes.o decode-insn.o	\
 				   simulate-insn.o
 obj-$(CONFIG_UPROBES)		+= uprobes.o decode-insn.o	\
 				   simulate-insn.o
+obj-$(CONFIG_RETHOOK)		+= rethook.o rethook_trampoline.o
diff --git a/arch/arm64/kernel/probes/rethook.c b/arch/arm64/kernel/probes/rethook.c
new file mode 100644
index 000000000000..edc6b804ad6a
--- /dev/null
+++ b/arch/arm64/kernel/probes/rethook.c
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Generic return hook for arm64.
+ * Most of the code is copied from arch/arm64/kernel/probes/kprobes.c
+ */
+
+#include <linux/kprobes.h>
+#include <linux/rethook.h>
+
+/* This is called from arch_rethook_trampoline() */
+unsigned long __used arch_rethook_trampoline_callback(struct pt_regs *regs)
+{
+	return rethook_trampoline_handler(regs, regs->regs[29]);
+}
+NOKPROBE_SYMBOL(arch_rethook_trampoline_callback);
+
+void arch_rethook_prepare(struct rethook_node *rhn, struct pt_regs *regs, bool mcount)
+{
+	rhn->ret_addr = regs->regs[30];
+	rhn->frame = regs->regs[29];
+
+	/* replace return addr (x30) with trampoline */
+	regs->regs[30] = (u64)arch_rethook_trampoline;
+}
+NOKPROBE_SYMBOL(arch_rethook_prepare);
diff --git a/arch/arm64/kernel/probes/rethook_trampoline.S b/arch/arm64/kernel/probes/rethook_trampoline.S
new file mode 100644
index 000000000000..610f520ee72b
--- /dev/null
+++ b/arch/arm64/kernel/probes/rethook_trampoline.S
@@ -0,0 +1,87 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * trampoline entry and return code for rethook.
+ * Copied from arch/arm64/kernel/probes/kprobes_trampoline.S
+ */
+
+#include <linux/linkage.h>
+#include <asm/asm-offsets.h>
+#include <asm/assembler.h>
+
+	.text
+
+	.macro	save_all_base_regs
+	stp x0, x1, [sp, #S_X0]
+	stp x2, x3, [sp, #S_X2]
+	stp x4, x5, [sp, #S_X4]
+	stp x6, x7, [sp, #S_X6]
+	stp x8, x9, [sp, #S_X8]
+	stp x10, x11, [sp, #S_X10]
+	stp x12, x13, [sp, #S_X12]
+	stp x14, x15, [sp, #S_X14]
+	stp x16, x17, [sp, #S_X16]
+	stp x18, x19, [sp, #S_X18]
+	stp x20, x21, [sp, #S_X20]
+	stp x22, x23, [sp, #S_X22]
+	stp x24, x25, [sp, #S_X24]
+	stp x26, x27, [sp, #S_X26]
+	stp x28, x29, [sp, #S_X28]
+	add x0, sp, #PT_REGS_SIZE
+	stp lr, x0, [sp, #S_LR]
+	/*
+	 * Construct a useful saved PSTATE
+	 */
+	mrs x0, nzcv
+	mrs x1, daif
+	orr x0, x0, x1
+	mrs x1, CurrentEL
+	orr x0, x0, x1
+	mrs x1, SPSel
+	orr x0, x0, x1
+	stp xzr, x0, [sp, #S_PC]
+	.endm
+
+	.macro	restore_all_base_regs
+	ldr x0, [sp, #S_PSTATE]
+	and x0, x0, #(PSR_N_BIT | PSR_Z_BIT | PSR_C_BIT | PSR_V_BIT)
+	msr nzcv, x0
+	ldp x0, x1, [sp, #S_X0]
+	ldp x2, x3, [sp, #S_X2]
+	ldp x4, x5, [sp, #S_X4]
+	ldp x6, x7, [sp, #S_X6]
+	ldp x8, x9, [sp, #S_X8]
+	ldp x10, x11, [sp, #S_X10]
+	ldp x12, x13, [sp, #S_X12]
+	ldp x14, x15, [sp, #S_X14]
+	ldp x16, x17, [sp, #S_X16]
+	ldp x18, x19, [sp, #S_X18]
+	ldp x20, x21, [sp, #S_X20]
+	ldp x22, x23, [sp, #S_X22]
+	ldp x24, x25, [sp, #S_X24]
+	ldp x26, x27, [sp, #S_X26]
+	ldp x28, x29, [sp, #S_X28]
+	.endm
+
+SYM_CODE_START(arch_rethook_trampoline)
+	sub sp, sp, #PT_REGS_SIZE
+
+	save_all_base_regs
+
+	/* Setup a frame pointer. */
+	add x29, sp, #S_FP
+
+	mov x0, sp
+	bl arch_rethook_trampoline_callback
+	/*
+	 * Replace trampoline address in lr with actual orig_ret_addr return
+	 * address.
+	 */
+	mov lr, x0
+
+	/* The frame pointer (x29) is restored with other registers. */
+	restore_all_base_regs
+
+	add sp, sp, #PT_REGS_SIZE
+	ret
+
+SYM_CODE_END(arch_rethook_trampoline)
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index e4103e085681..efb5b85b57c2 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -8,6 +8,7 @@
 #include <linux/export.h>
 #include <linux/ftrace.h>
 #include <linux/kprobes.h>
+#include <linux/rethook.h>
 #include <linux/sched.h>
 #include <linux/sched/debug.h>
 #include <linux/sched/task_stack.h>
@@ -38,7 +39,7 @@ static notrace void start_backtrace(struct stackframe *frame, unsigned long fp,
 {
 	frame->fp = fp;
 	frame->pc = pc;
-#ifdef CONFIG_KRETPROBES
+#if defined(CONFIG_KRETPROBES) || defined(CONFIG_RETHOOK)
 	frame->kr_cur = NULL;
 #endif
 
@@ -138,6 +139,10 @@ static int notrace unwind_frame(struct task_struct *tsk,
 	if (is_kretprobe_trampoline(frame->pc))
 		frame->pc = kretprobe_find_ret_addr(tsk, (void *)frame->fp, &frame->kr_cur);
 #endif
+#ifdef CONFIG_RETHOOK
+	if (is_rethook_trampoline(frame->pc))
+		frame->pc = rethook_find_ret_addr(tsk, frame->fp, &frame->kr_cur);
+#endif
 
 	return 0;
 }

[PATCH v11 06/12] powerpc: Add rethook support

[Masami Hiramatsu]

Add rethook powerpc64 implementation. Most of the code has been copied from
kretprobes on powerpc64.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 Changes in v10:
  - Add a dummy @mcount to arch_rethook_prepare().
---
 arch/powerpc/Kconfig          |    1 +
 arch/powerpc/kernel/Makefile  |    1 +
 arch/powerpc/kernel/rethook.c |   72 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 74 insertions(+)
 create mode 100644 arch/powerpc/kernel/rethook.c

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index b779603978e1..5feaa241fb56 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -229,6 +229,7 @@ config PPC
 	select HAVE_PERF_EVENTS_NMI		if PPC64
 	select HAVE_PERF_REGS
 	select HAVE_PERF_USER_STACK_DUMP
+	select HAVE_RETHOOK			if KPROBES
 	select HAVE_REGS_AND_STACK_ACCESS_API
 	select HAVE_RELIABLE_STACKTRACE
 	select HAVE_RSEQ
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index 4d7829399570..feb24ea83ca6 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -115,6 +115,7 @@ obj-$(CONFIG_SMP)		+= smp.o
 obj-$(CONFIG_KPROBES)		+= kprobes.o
 obj-$(CONFIG_OPTPROBES)		+= optprobes.o optprobes_head.o
 obj-$(CONFIG_KPROBES_ON_FTRACE)	+= kprobes-ftrace.o
+obj-$(CONFIG_RETHOOK)		+= rethook.o
 obj-$(CONFIG_UPROBES)		+= uprobes.o
 obj-$(CONFIG_PPC_UDBG_16550)	+= legacy_serial.o udbg_16550.o
 obj-$(CONFIG_SWIOTLB)		+= dma-swiotlb.o
diff --git a/arch/powerpc/kernel/rethook.c b/arch/powerpc/kernel/rethook.c
new file mode 100644
index 000000000000..a8a128748efa
--- /dev/null
+++ b/arch/powerpc/kernel/rethook.c
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * PowerPC implementation of rethook. This depends on kprobes.
+ */
+
+#include <linux/kprobes.h>
+#include <linux/rethook.h>
+
+/*
+ * Function return trampoline:
+ * 	- init_kprobes() establishes a probepoint here
+ * 	- When the probed function returns, this probe
+ * 		causes the handlers to fire
+ */
+asm(".global arch_rethook_trampoline\n"
+	".type arch_rethook_trampoline, @function\n"
+	"arch_rethook_trampoline:\n"
+	"nop\n"
+	"blr\n"
+	".size arch_rethook_trampoline, .-arch_rethook_trampoline\n");
+
+/*
+ * Called when the probe at kretprobe trampoline is hit
+ */
+static int trampoline_rethook_handler(struct kprobe *p, struct pt_regs *regs)
+{
+	unsigned long orig_ret_address;
+
+	orig_ret_address = rethook_trampoline_handler(regs, 0);
+	/*
+	 * We get here through one of two paths:
+	 * 1. by taking a trap -> kprobe_handler() -> here
+	 * 2. by optprobe branch -> optimized_callback() -> opt_pre_handler() -> here
+	 *
+	 * When going back through (1), we need regs->nip to be setup properly
+	 * as it is used to determine the return address from the trap.
+	 * For (2), since nip is not honoured with optprobes, we instead setup
+	 * the link register properly so that the subsequent 'blr' in
+	 * __kretprobe_trampoline jumps back to the right instruction.
+	 *
+	 * For nip, we should set the address to the previous instruction since
+	 * we end up emulating it in kprobe_handler(), which increments the nip
+	 * again.
+	 */
+	regs_set_return_ip(regs, orig_ret_address - 4);
+	regs->link = orig_ret_address;
+
+	return 0;
+}
+NOKPROBE_SYMBOL(trampoline_rethook_handler);
+
+void arch_rethook_prepare(struct rethook_node *rh, struct pt_regs *regs, bool mcount)
+{
+	rh->ret_addr = regs->link;
+	rh->frame = 0;
+
+	/* Replace the return addr with trampoline addr */
+	regs->link = (unsigned long)arch_rethook_trampoline;
+}
+NOKPROBE_SYMBOL(arch_prepare_kretprobe);
+
+static struct kprobe trampoline_p = {
+	.addr = (kprobe_opcode_t *) &arch_rethook_trampoline,
+	.pre_handler = trampoline_rethook_handler
+};
+
+static int init_arch_rethook(void)
+{
+	return register_kprobe(&trampoline_p);
+}
+
+core_initcall(init_arch_rethook);

[PATCH v11 07/12] ARM: rethook: Add rethook arm implementation

[Masami Hiramatsu]

Add rethook arm implementation. Most of the code has been copied from
kretprobes on arm.
Since the arm's ftrace implementation is a bit special, this needs a
special care using from fprobe.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 Changes in v10:
  - Fix for the mcount entry.
 Changes in v5:
  - Fix build error when !CONFIG_KRETPROBES
---
 arch/arm/Kconfig                  |    1 
 arch/arm/include/asm/stacktrace.h |    4 +
 arch/arm/kernel/stacktrace.c      |    6 ++
 arch/arm/probes/Makefile          |    1 
 arch/arm/probes/rethook.c         |  101 +++++++++++++++++++++++++++++++++++++
 5 files changed, 111 insertions(+), 2 deletions(-)
 create mode 100644 arch/arm/probes/rethook.c

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 4c97cb40eebb..440f69ee8af5 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -107,6 +107,7 @@ config ARM
 	select HAVE_MOD_ARCH_SPECIFIC
 	select HAVE_NMI
 	select HAVE_OPTPROBES if !THUMB2_KERNEL
+	select HAVE_RETHOOK
 	select HAVE_PERF_EVENTS
 	select HAVE_PERF_REGS
 	select HAVE_PERF_USER_STACK_DUMP
diff --git a/arch/arm/include/asm/stacktrace.h b/arch/arm/include/asm/stacktrace.h
index 8f54f9ad8a9b..babed1707ca8 100644
--- a/arch/arm/include/asm/stacktrace.h
+++ b/arch/arm/include/asm/stacktrace.h
@@ -14,7 +14,7 @@ struct stackframe {
 	unsigned long sp;
 	unsigned long lr;
 	unsigned long pc;
-#ifdef CONFIG_KRETPROBES
+#if defined(CONFIG_KRETPROBES) || defined(CONFIG_RETHOOK)
 	struct llist_node *kr_cur;
 	struct task_struct *tsk;
 #endif
@@ -27,7 +27,7 @@ void arm_get_current_stackframe(struct pt_regs *regs, struct stackframe *frame)
 		frame->sp = regs->ARM_sp;
 		frame->lr = regs->ARM_lr;
 		frame->pc = regs->ARM_pc;
-#ifdef CONFIG_KRETPROBES
+#if defined(CONFIG_KRETPROBES) || defined(CONFIG_RETHOOK)
 		frame->kr_cur = NULL;
 		frame->tsk = current;
 #endif
diff --git a/arch/arm/kernel/stacktrace.c b/arch/arm/kernel/stacktrace.c
index 75e905508f27..f509c6be4f57 100644
--- a/arch/arm/kernel/stacktrace.c
+++ b/arch/arm/kernel/stacktrace.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-only
 #include <linux/export.h>
 #include <linux/kprobes.h>
+#include <linux/rethook.h>
 #include <linux/sched.h>
 #include <linux/sched/debug.h>
 #include <linux/stacktrace.h>
@@ -66,6 +67,11 @@ int notrace unwind_frame(struct stackframe *frame)
 	frame->sp = *(unsigned long *)(fp - 8);
 	frame->pc = *(unsigned long *)(fp - 4);
 #endif
+#ifdef CONFIG_RETHOOK
+	if (is_rethook_trampoline(frame->pc))
+		frame->pc = rethook_find_ret_addr(frame->tsk, frame->fp,
+						  &frame->kr_cur);
+#endif
 #ifdef CONFIG_KRETPROBES
 	if (is_kretprobe_trampoline(frame->pc))
 		frame->pc = kretprobe_find_ret_addr(frame->tsk,
diff --git a/arch/arm/probes/Makefile b/arch/arm/probes/Makefile
index 8b0ea5ace100..10c083a22223 100644
--- a/arch/arm/probes/Makefile
+++ b/arch/arm/probes/Makefile
@@ -6,3 +6,4 @@ obj-$(CONFIG_KPROBES)		+= decode-thumb.o
 else
 obj-$(CONFIG_KPROBES)		+= decode-arm.o
 endif
+obj-$(CONFIG_RETHOOK)		+= rethook.o
diff --git a/arch/arm/probes/rethook.c b/arch/arm/probes/rethook.c
new file mode 100644
index 000000000000..338ebe964eb1
--- /dev/null
+++ b/arch/arm/probes/rethook.c
@@ -0,0 +1,101 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * arm implementation of rethook. Mostly copied from arch/arm/probes/kprobes/core.c
+ */
+
+#include <linux/kprobes.h>
+#include <linux/rethook.h>
+
+/* Called from arch_rethook_trampoline */
+static __used unsigned long arch_rethook_trampoline_callback(struct pt_regs *regs)
+{
+	return rethook_trampoline_handler(regs, regs->ARM_fp);
+}
+NOKPROBE_SYMBOL(arch_rethook_trampoline_callback);
+
+/*
+ * When a rethook'ed function returns, it returns to arch_rethook_trampoline
+ * which calls rethook callback. We construct a struct pt_regs to
+ * give a view of registers r0-r11, sp, lr, and pc to the user
+ * return-handler. This is not a complete pt_regs structure, but that
+ * should be enough for stacktrace from the return handler with or
+ * without pt_regs.
+ */
+void __naked arch_rethook_trampoline(void)
+{
+	__asm__ __volatile__ (
+#ifdef CONFIG_FRAME_POINTER
+		"ldr	lr, =arch_rethook_trampoline	\n\t"
+	/* this makes a framepointer on pt_regs. */
+#ifdef CONFIG_CC_IS_CLANG
+		"stmdb	sp, {sp, lr, pc}	\n\t"
+		"sub	sp, sp, #12		\n\t"
+		/* In clang case, pt_regs->ip = lr. */
+		"stmdb	sp!, {r0 - r11, lr}	\n\t"
+		/* fp points regs->r11 (fp) */
+		"add	fp, sp,	#44		\n\t"
+#else /* !CONFIG_CC_IS_CLANG */
+		/* In gcc case, pt_regs->ip = fp. */
+		"stmdb	sp, {fp, sp, lr, pc}	\n\t"
+		"sub	sp, sp, #16		\n\t"
+		"stmdb	sp!, {r0 - r11}		\n\t"
+		/* fp points regs->r15 (pc) */
+		"add	fp, sp, #60		\n\t"
+#endif /* CONFIG_CC_IS_CLANG */
+#else /* !CONFIG_FRAME_POINTER */
+		"sub	sp, sp, #16		\n\t"
+		"stmdb	sp!, {r0 - r11}		\n\t"
+#endif /* CONFIG_FRAME_POINTER */
+		"mov	r0, sp			\n\t"
+		"bl	arch_rethook_trampoline_callback	\n\t"
+		"mov	lr, r0			\n\t"
+		"ldmia	sp!, {r0 - r11}		\n\t"
+		"add	sp, sp, #16		\n\t"
+#ifdef CONFIG_THUMB2_KERNEL
+		"bx	lr			\n\t"
+#else
+		"mov	pc, lr			\n\t"
+#endif
+		: : : "memory");
+}
+NOKPROBE_SYMBOL(arch_rethook_trampoline);
+
+/*
+ * At the entry of function with mcount. The stack and registers are prepared
+ * for the mcount function as below.
+ *
+ * mov     ip, sp
+ * push    {fp, ip, lr, pc}
+ * sub     fp, ip, #4	; FP[0] = PC, FP[-4] = LR, and FP[-12] = call-site FP.
+ * push    {lr}
+ * bl      <__gnu_mcount_nc> ; call ftrace
+ *
+ * And when returning from the function, call-site FP, SP and PC are restored
+ * from stack as below;
+ *
+ * ldm     sp, {fp, sp, pc}
+ *
+ * Thus, if the arch_rethook_prepare() is called from real function entry,
+ * it must change the LR and save FP in pt_regs. But if it is called via
+ * mcount context (ftrace), it must change the LR on stack, which is next
+ * to the PC (= FP[-4]), and save the FP value at FP[-12].
+ */
+void arch_rethook_prepare(struct rethook_node *rh, struct pt_regs *regs, bool mcount)
+{
+	unsigned long *ret_addr, *frame;
+
+	if (mcount) {
+		ret_addr = (unsigned long *)(regs->ARM_fp - 4);
+		frame = (unsigned long *)(regs->ARM_fp - 12);
+	} else {
+		ret_addr = &regs->ARM_lr;
+		frame = &regs->ARM_fp;
+	}
+
+	rh->ret_addr = *ret_addr;
+	rh->frame = *frame;
+
+	/* Replace the return addr with trampoline addr. */
+	*ret_addr = (unsigned long)arch_rethook_trampoline;
+}
+NOKPROBE_SYMBOL(arch_rethook_prepare);

[PATCH v11 08/12] fprobe: Add exit_handler support

[Masami Hiramatsu]

Add exit_handler to fprobe. fprobe + rethook allows us to hook the kernel
function return. The rethook will be enabled only if the
fprobe::exit_handler is set.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 Changes in v10:
  - Call rethook_hook() with mcount context flag.
 Changes in v7:
  - Fix unregister_fprobe() to ensure the rethook handlers are
    finished when it returns.
  - Update Kconfig help.
 Changes in v6:
  - Update according to the fprobe update.
 Changes in v5:
  - Add dependency for HAVE_RETHOOK.
 Changes in v4:
  - Check fprobe is disabled in the exit handler.
 Changes in v3:
  - Make sure to clear rethook->data before free.
  - Handler checks the data is not NULL.
  - Free rethook only if the rethook is using.
---
 include/linux/fprobe.h |    6 ++
 kernel/trace/Kconfig   |    9 ++--
 kernel/trace/fprobe.c  |  116 ++++++++++++++++++++++++++++++++++++++++++++++--
 3 files changed, 122 insertions(+), 9 deletions(-)

diff --git a/include/linux/fprobe.h b/include/linux/fprobe.h
index 2ba099aff041..8eefec2b485e 100644
--- a/include/linux/fprobe.h
+++ b/include/linux/fprobe.h
@@ -5,13 +5,16 @@
 
 #include <linux/compiler.h>
 #include <linux/ftrace.h>
+#include <linux/rethook.h>
 
 /**
  * struct fprobe - ftrace based probe.
  * @ops: The ftrace_ops.
  * @nmissed: The counter for missing events.
  * @flags: The status flag.
+ * @rethook: The rethook data structure. (internal data)
  * @entry_handler: The callback function for function entry.
+ * @exit_handler: The callback function for function exit.
  */
 struct fprobe {
 #ifdef CONFIG_FUNCTION_TRACER
@@ -25,7 +28,10 @@ struct fprobe {
 #endif
 	unsigned long		nmissed;
 	unsigned int		flags;
+	struct rethook		*rethook;
+
 	void (*entry_handler)(struct fprobe *fp, unsigned long entry_ip, struct pt_regs *regs);
+	void (*exit_handler)(struct fprobe *fp, unsigned long entry_ip, struct pt_regs *regs);
 };
 
 #define FPROBE_FL_DISABLED	1
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index e75504e42ab8..99dd4ca63d68 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -251,11 +251,14 @@ config FPROBE
 	bool "Kernel Function Probe (fprobe)"
 	depends on FUNCTION_TRACER
 	depends on DYNAMIC_FTRACE_WITH_REGS
+	depends on HAVE_RETHOOK
+	select RETHOOK
 	default n
 	help
-	  This option enables kernel function probe (fprobe) based on ftrace,
-	  which is similar to kprobes, but probes only for kernel function
-	  entries and it can probe multiple functions by one fprobe.
+	  This option enables kernel function probe (fprobe) based on ftrace.
+	  The fprobe is similar to kprobes, but probes only for kernel function
+	  entries and exits. This also can probe multiple functions by one
+	  fprobe.
 
 	  If unsure, say N.
 
diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
index 7e8ceee339a0..38073632bfe4 100644
--- a/kernel/trace/fprobe.c
+++ b/kernel/trace/fprobe.c
@@ -8,12 +8,22 @@
 #include <linux/fprobe.h>
 #include <linux/kallsyms.h>
 #include <linux/kprobes.h>
+#include <linux/rethook.h>
 #include <linux/slab.h>
 #include <linux/sort.h>
 
+#include "trace.h"
+
+struct fprobe_rethook_node {
+	struct rethook_node node;
+	unsigned long entry_ip;
+};
+
 static void fprobe_handler(unsigned long ip, unsigned long parent_ip,
 			   struct ftrace_ops *ops, struct ftrace_regs *fregs)
 {
+	struct fprobe_rethook_node *fpr;
+	struct rethook_node *rh;
 	struct fprobe *fp;
 	int bit;
 
@@ -30,10 +40,37 @@ static void fprobe_handler(unsigned long ip, unsigned long parent_ip,
 	if (fp->entry_handler)
 		fp->entry_handler(fp, ip, ftrace_get_regs(fregs));
 
+	if (fp->exit_handler) {
+		rh = rethook_try_get(fp->rethook);
+		if (!rh) {
+			fp->nmissed++;
+			goto out;
+		}
+		fpr = container_of(rh, struct fprobe_rethook_node, node);
+		fpr->entry_ip = ip;
+		rethook_hook(rh, ftrace_get_regs(fregs), true);
+	}
+
+out:
 	ftrace_test_recursion_unlock(bit);
 }
 NOKPROBE_SYMBOL(fprobe_handler);
 
+static void fprobe_exit_handler(struct rethook_node *rh, void *data,
+				struct pt_regs *regs)
+{
+	struct fprobe *fp = (struct fprobe *)data;
+	struct fprobe_rethook_node *fpr;
+
+	if (!fp || fprobe_disabled(fp))
+		return;
+
+	fpr = container_of(rh, struct fprobe_rethook_node, node);
+
+	fp->exit_handler(fp, fpr->entry_ip, regs);
+}
+NOKPROBE_SYMBOL(fprobe_exit_handler);
+
 /* Convert ftrace location address from symbols */
 static unsigned long *get_ftrace_locations(const char **syms, int num)
 {
@@ -77,6 +114,48 @@ static void fprobe_init(struct fprobe *fp)
 	fp->ops.flags |= FTRACE_OPS_FL_SAVE_REGS;
 }
 
+static int fprobe_init_rethook(struct fprobe *fp, int num)
+{
+	int i, size;
+
+	if (num < 0)
+		return -EINVAL;
+
+	if (!fp->exit_handler) {
+		fp->rethook = NULL;
+		return 0;
+	}
+
+	/* Initialize rethook if needed */
+	size = num * num_possible_cpus() * 2;
+	if (size < 0)
+		return -E2BIG;
+
+	fp->rethook = rethook_alloc((void *)fp, fprobe_exit_handler);
+	for (i = 0; i < size; i++) {
+		struct rethook_node *node;
+
+		node = kzalloc(sizeof(struct fprobe_rethook_node), GFP_KERNEL);
+		if (!node) {
+			rethook_free(fp->rethook);
+			fp->rethook = NULL;
+			return -ENOMEM;
+		}
+		rethook_add_node(fp->rethook, node);
+	}
+	return 0;
+}
+
+static void fprobe_fail_cleanup(struct fprobe *fp)
+{
+	if (fp->rethook) {
+		/* Don't need to cleanup rethook->handler because this is not used. */
+		rethook_free(fp->rethook);
+		fp->rethook = NULL;
+	}
+	ftrace_free_filter(&fp->ops);
+}
+
 /**
  * register_fprobe() - Register fprobe to ftrace by pattern.
  * @fp: A fprobe data structure to be registered.
@@ -90,6 +169,7 @@ static void fprobe_init(struct fprobe *fp)
  */
 int register_fprobe(struct fprobe *fp, const char *filter, const char *notfilter)
 {
+	struct ftrace_hash *hash;
 	unsigned char *str;
 	int ret, len;
 
@@ -114,10 +194,21 @@ int register_fprobe(struct fprobe *fp, const char *filter, const char *notfilter
 			goto out;
 	}
 
-	ret = register_ftrace_function(&fp->ops);
+	/* TODO:
+	 * correctly calculate the total number of filtered symbols
+	 * from both filter and notfilter.
+	 */
+	hash = fp->ops.local_hash.filter_hash;
+	if (WARN_ON_ONCE(!hash))
+		goto out;
+
+	ret = fprobe_init_rethook(fp, (int)hash->count);
+	if (!ret)
+		ret = register_ftrace_function(&fp->ops);
+
 out:
 	if (ret)
-		ftrace_free_filter(&fp->ops);
+		fprobe_fail_cleanup(fp);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(register_fprobe);
@@ -145,12 +236,15 @@ int register_fprobe_ips(struct fprobe *fp, unsigned long *addrs, int num)
 	fprobe_init(fp);
 
 	ret = ftrace_set_filter_ips(&fp->ops, addrs, num, 0, 0);
+	if (ret)
+		return ret;
+
+	ret = fprobe_init_rethook(fp, num);
 	if (!ret)
 		ret = register_ftrace_function(&fp->ops);
 
 	if (ret)
-		ftrace_free_filter(&fp->ops);
-
+		fprobe_fail_cleanup(fp);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(register_fprobe_ips);
@@ -201,10 +295,20 @@ int unregister_fprobe(struct fprobe *fp)
 	if (!fp || fp->ops.func != fprobe_handler)
 		return -EINVAL;
 
+	/*
+	 * rethook_free() starts disabling the rethook, but the rethook handlers
+	 * may be running on other processors at this point. To make sure that all
+	 * current running handlers are finished, call unregister_ftrace_function()
+	 * after this.
+	 */
+	if (fp->rethook)
+		rethook_free(fp->rethook);
+
 	ret = unregister_ftrace_function(&fp->ops);
+	if (ret < 0)
+		return ret;
 
-	if (!ret)
-		ftrace_free_filter(&fp->ops);
+	ftrace_free_filter(&fp->ops);
 
 	return ret;
 }

[PATCH v11 09/12] fprobe: Add sample program for fprobe

[Masami Hiramatsu]

Add a sample program for the fprobe. The sample_fprobe puts a fprobe on
kernel_clone() by default. This dump stack and some called address info
at the function entry and exit.

The sample_fprobe.ko gets 2 parameters.
- symbol: you can specify the comma separated symbols or wildcard symbol
  pattern (in this case you can not use comma)
- stackdump: a bool value to enable or disable stack dump in the fprobe
  handler.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 Changes in v6:
  - Dump stack on the handler as explained in the comment.
  - Add "stackdump" option to enable/disable stackdump.
  - Support wildcard filter.
 Changes in v2:
  - Fix infinit loop for multiple symbols.
  - Fix memory leaks for copied string and entry array.
  - Update for new fprobe APIs.
  - Fix style issues.
---
 samples/Kconfig                 |    7 ++
 samples/Makefile                |    1 
 samples/fprobe/Makefile         |    3 +
 samples/fprobe/fprobe_example.c |  120 +++++++++++++++++++++++++++++++++++++++
 4 files changed, 131 insertions(+)
 create mode 100644 samples/fprobe/Makefile
 create mode 100644 samples/fprobe/fprobe_example.c

diff --git a/samples/Kconfig b/samples/Kconfig
index 22cc921ae291..8415d60ea5f4 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -73,6 +73,13 @@ config SAMPLE_HW_BREAKPOINT
 	help
 	  This builds kernel hardware breakpoint example modules.
 
+config SAMPLE_FPROBE
+	tristate "Build fprobe examples -- loadable modules only"
+	depends on FPROBE && m
+	help
+	  This builds a fprobe example module. This module has an option 'symbol'.
+	  You can specify a probed symbol or symbols separated with ','.
+
 config SAMPLE_KFIFO
 	tristate "Build kfifo examples -- loadable modules only"
 	depends on m
diff --git a/samples/Makefile b/samples/Makefile
index 1ae4de99c983..6d662965be5b 100644
--- a/samples/Makefile
+++ b/samples/Makefile
@@ -33,3 +33,4 @@ subdir-$(CONFIG_SAMPLE_WATCHDOG)	+= watchdog
 subdir-$(CONFIG_SAMPLE_WATCH_QUEUE)	+= watch_queue
 obj-$(CONFIG_DEBUG_KMEMLEAK_TEST)	+= kmemleak/
 obj-$(CONFIG_SAMPLE_CORESIGHT_SYSCFG)	+= coresight/
+obj-$(CONFIG_SAMPLE_FPROBE)		+= fprobe/
diff --git a/samples/fprobe/Makefile b/samples/fprobe/Makefile
new file mode 100644
index 000000000000..ecccbfa6e99b
--- /dev/null
+++ b/samples/fprobe/Makefile
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+obj-$(CONFIG_SAMPLE_FPROBE) += fprobe_example.o
diff --git a/samples/fprobe/fprobe_example.c b/samples/fprobe/fprobe_example.c
new file mode 100644
index 000000000000..24d3cf109140
--- /dev/null
+++ b/samples/fprobe/fprobe_example.c
@@ -0,0 +1,120 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Here's a sample kernel module showing the use of fprobe to dump a
+ * stack trace and selected registers when kernel_clone() is called.
+ *
+ * For more information on theory of operation of kprobes, see
+ * Documentation/trace/kprobes.rst
+ *
+ * You will see the trace data in /var/log/messages and on the console
+ * whenever kernel_clone() is invoked to create a new process.
+ */
+
+#define pr_fmt(fmt) "%s: " fmt, __func__
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/fprobe.h>
+#include <linux/sched/debug.h>
+#include <linux/slab.h>
+
+#define BACKTRACE_DEPTH 16
+#define MAX_SYMBOL_LEN 4096
+struct fprobe sample_probe;
+
+static char symbol[MAX_SYMBOL_LEN] = "kernel_clone";
+module_param_string(symbol, symbol, sizeof(symbol), 0644);
+static char nosymbol[MAX_SYMBOL_LEN] = "";
+module_param_string(nosymbol, nosymbol, sizeof(nosymbol), 0644);
+static bool stackdump = true;
+module_param(stackdump, bool, 0644);
+
+static void show_backtrace(void)
+{
+	unsigned long stacks[BACKTRACE_DEPTH];
+	unsigned int len;
+
+	len = stack_trace_save(stacks, BACKTRACE_DEPTH, 2);
+	stack_trace_print(stacks, len, 24);
+}
+
+static void sample_entry_handler(struct fprobe *fp, unsigned long ip, struct pt_regs *regs)
+{
+	pr_info("Enter <%pS> ip = 0x%p\n", (void *)ip, (void *)ip);
+	if (stackdump)
+		show_backtrace();
+}
+
+static void sample_exit_handler(struct fprobe *fp, unsigned long ip, struct pt_regs *regs)
+{
+	unsigned long rip = instruction_pointer(regs);
+
+	pr_info("Return from <%pS> ip = 0x%p to rip = 0x%p (%pS)\n",
+		(void *)ip, (void *)ip, (void *)rip, (void *)rip);
+	if (stackdump)
+		show_backtrace();
+}
+
+static int __init fprobe_init(void)
+{
+	char *p, *symbuf = NULL;
+	const char **syms;
+	int ret, count, i;
+
+	sample_probe.entry_handler = sample_entry_handler;
+	sample_probe.exit_handler = sample_exit_handler;
+
+	if (strchr(symbol, '*')) {
+		/* filter based fprobe */
+		ret = register_fprobe(&sample_probe, symbol,
+				      nosymbol[0] == '\0' ? NULL : nosymbol);
+		goto out;
+	} else if (!strchr(symbol, ',')) {
+		symbuf = symbol;
+		ret = register_fprobe_syms(&sample_probe, (const char **)&symbuf, 1);
+		goto out;
+	}
+
+	/* Comma separated symbols */
+	symbuf = kstrdup(symbol, GFP_KERNEL);
+	if (!symbuf)
+		return -ENOMEM;
+	p = symbuf;
+	count = 1;
+	while ((p = strchr(++p, ',')) != NULL)
+		count++;
+
+	pr_info("%d symbols found\n", count);
+
+	syms = kcalloc(count, sizeof(char *), GFP_KERNEL);
+	if (!syms) {
+		kfree(symbuf);
+		return -ENOMEM;
+	}
+
+	p = symbuf;
+	for (i = 0; i < count; i++)
+		syms[i] = strsep(&p, ",");
+
+	ret = register_fprobe_syms(&sample_probe, syms, count);
+	kfree(syms);
+	kfree(symbuf);
+out:
+	if (ret < 0)
+		pr_err("register_fprobe failed, returned %d\n", ret);
+	else
+		pr_info("Planted fprobe at %s\n", symbol);
+
+	return ret;
+}
+
+static void __exit fprobe_exit(void)
+{
+	unregister_fprobe(&sample_probe);
+
+	pr_info("fprobe at %s unregistered\n", symbol);
+}
+
+module_init(fprobe_init)
+module_exit(fprobe_exit)
+MODULE_LICENSE("GPL");

[PATCH v11 10/12] fprobe: Introduce FPROBE_FL_KPROBE_SHARED flag for fprobe

[Masami Hiramatsu]

Introduce FPROBE_FL_KPROBE_SHARED flag for sharing fprobe callback with
kprobes safely from the viewpoint of recursion.

Since the recursion safety of the fprobe (and ftrace) is a bit different
from the kprobes, this may cause an issue if user wants to run the same
code from the fprobe and the kprobes.

The kprobes has per-cpu 'current_kprobe' variable which protects the
kprobe handler from recursion in any case. On the other hand, the fprobe
uses only ftrace_test_recursion_trylock(), which will allow interrupt
context calls another (or same) fprobe during the fprobe user handler is
running.

This is not a matter in cases if the common callback shared among the
kprobes and the fprobe has its own recursion detection, or it can handle
the recursion in the different contexts (normal/interrupt/NMI.)
But if it relies on the 'current_kprobe' recursion lock, it has to check
kprobe_running() and use kprobe_busy_*() APIs.

Fprobe has FPROBE_FL_KPROBE_SHARED flag to do this. If your common callback
code will be shared with kprobes, please set FPROBE_FL_KPROBE_SHARED
*before* registering the fprobe, like;

 fprobe.flags = FPROBE_FL_KPROBE_SHARED;

 register_fprobe(&fprobe, "func*", NULL);

This will protect your common callback from the nested call.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 include/linux/fprobe.h  |   12 ++++++++++++
 include/linux/kprobes.h |    3 +++
 kernel/trace/fprobe.c   |   19 ++++++++++++++++++-
 3 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/include/linux/fprobe.h b/include/linux/fprobe.h
index 8eefec2b485e..1c2bde0ead73 100644
--- a/include/linux/fprobe.h
+++ b/include/linux/fprobe.h
@@ -34,13 +34,25 @@ struct fprobe {
 	void (*exit_handler)(struct fprobe *fp, unsigned long entry_ip, struct pt_regs *regs);
 };
 
+/* This fprobe is soft-disabled. */
 #define FPROBE_FL_DISABLED	1
 
+/*
+ * This fprobe handler will be shared with kprobes.
+ * This flag must be set before registering.
+ */
+#define FPROBE_FL_KPROBE_SHARED	2
+
 static inline bool fprobe_disabled(struct fprobe *fp)
 {
 	return (fp) ? fp->flags & FPROBE_FL_DISABLED : false;
 }
 
+static inline bool fprobe_shared_with_kprobes(struct fprobe *fp)
+{
+	return (fp) ? fp->flags & FPROBE_FL_KPROBE_SHARED : false;
+}
+
 #ifdef CONFIG_FPROBE
 int register_fprobe(struct fprobe *fp, const char *filter, const char *notfilter);
 int register_fprobe_ips(struct fprobe *fp, unsigned long *addrs, int num);
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index 19b884353b15..5f1859836deb 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -427,6 +427,9 @@ static inline struct kprobe *kprobe_running(void)
 {
 	return NULL;
 }
+#define kprobe_busy_begin()	do {} while (0)
+#define kprobe_busy_end()	do {} while (0)
+
 static inline int register_kprobe(struct kprobe *p)
 {
 	return -EOPNOTSUPP;
diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
index 38073632bfe4..8b2dd5b9dcd1 100644
--- a/kernel/trace/fprobe.c
+++ b/kernel/trace/fprobe.c
@@ -56,6 +56,20 @@ static void fprobe_handler(unsigned long ip, unsigned long parent_ip,
 }
 NOKPROBE_SYMBOL(fprobe_handler);
 
+static void fprobe_kprobe_handler(unsigned long ip, unsigned long parent_ip,
+				  struct ftrace_ops *ops, struct ftrace_regs *fregs)
+{
+	struct fprobe *fp = container_of(ops, struct fprobe, ops);
+
+	if (unlikely(kprobe_running())) {
+		fp->nmissed++;
+		return;
+	}
+	kprobe_busy_begin();
+	fprobe_handler(ip, parent_ip, ops, fregs);
+	kprobe_busy_end();
+}
+
 static void fprobe_exit_handler(struct rethook_node *rh, void *data,
 				struct pt_regs *regs)
 {
@@ -110,7 +124,10 @@ static unsigned long *get_ftrace_locations(const char **syms, int num)
 static void fprobe_init(struct fprobe *fp)
 {
 	fp->nmissed = 0;
-	fp->ops.func = fprobe_handler;
+	if (fprobe_shared_with_kprobes(fp))
+		fp->ops.func = fprobe_kprobe_handler;
+	else
+		fp->ops.func = fprobe_handler;
 	fp->ops.flags |= FTRACE_OPS_FL_SAVE_REGS;
 }
 

[PATCH v11 11/12] docs: fprobe: Add fprobe description to ftrace-use.rst

[Masami Hiramatsu]

Add a documentation of fprobe for the user who needs
this interface.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 Changes in v7:
  - Clarify unregister_fprobe() guarantee the callbacks will no
    longer being called after that.
  - Fix some wording.
 Changes in v6:
  - Update document according to the latest spec.
---
 Documentation/trace/fprobe.rst |  171 ++++++++++++++++++++++++++++++++++++++++
 Documentation/trace/index.rst  |    1 
 2 files changed, 172 insertions(+)
 create mode 100644 Documentation/trace/fprobe.rst

diff --git a/Documentation/trace/fprobe.rst b/Documentation/trace/fprobe.rst
new file mode 100644
index 000000000000..4275e95e16bc
--- /dev/null
+++ b/Documentation/trace/fprobe.rst
@@ -0,0 +1,171 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==================================
+Fprobe - Function entry/exit probe
+==================================
+
+.. Author: Masami Hiramatsu <mhiramat@kernel.org>
+
+Introduction
+============
+
+Instead of using ftrace full feature, if you only want to attach callbacks
+on function entry and exit, similar to the kprobes and kretprobes, you can
+use fprobe. Compared with kprobes and kretprobes, fprobe gives faster
+instrumentation for multiple functions with single handler. This document
+describes how to use fprobe.
+
+The usage of fprobe
+===================
+
+The fprobe is a wrapper of ftrace (+ kretprobe-like return callback) to
+attach callbacks to multiple function entry and exit. User needs to set up
+the `struct fprobe` and pass it to `register_fprobe()`.
+
+Typically, `fprobe` data structure is initialized with the `entry_handler`
+and/or `exit_handler` as below.
+
+.. code-block:: c
+
+ struct fprobe fp = {
+        .entry_handler  = my_entry_callback,
+        .exit_handler   = my_exit_callback,
+ };
+
+To enable the fprobe, call one of register_fprobe(), register_fprobe_ips(), and
+register_fprobe_syms(). These register the fprobe with different type of
+parameters.
+
+The register_fprobe() enables a fprobe by function-name filters.
+E.g. this enables @fp on "func*()" function except "func2()".::
+
+  register_fprobe(&fp, "func*", "func2");
+
+The register_fprobe_ips() enables a fprobe by ftrace-location addresses.
+E.g.
+
+.. code-block:: c
+
+  unsigned long ips[] = { 0x.... };
+
+  register_fprobe_ips(&fp, ips, ARRAY_SIZE(ips));
+
+And the register_fprobe_syms() enables a fprobe by symbol names.
+E.g.
+
+.. code-block:: c
+
+  char syms[] = {"func1", "func2", "func3"};
+
+  register_fprobe_syms(&fp, syms, ARRAY_SIZE(syms));
+
+To disable (remove from functions) this fprobe, call::
+
+  unregister_fprobe(&fp);
+
+You can temporally (soft) disable the fprobe by::
+
+  disable_fprobe(&fp);
+
+and resume by::
+
+  enable_fprobe(&fp);
+
+The above is defined by including the header::
+
+  #include <linux/fprobe.h>
+
+Same as ftrace, the registered callback will start being called some time
+after the register_fprobe() is called and before it returns. See
+:file:`Documentation/trace/ftrace.rst`.
+
+Also, the unregister_fprobe() will guarantee that the both enter and exit
+handlers are no longer being called by functions after unregister_fprobe()
+returns as same as unregister_ftrace_function().
+
+The fprobe entry/exit handler
+=============================
+
+The prototype of the entry/exit callback function is as follows:
+
+.. code-block:: c
+
+ void callback_func(struct fprobe *fp, unsigned long entry_ip, struct pt_regs *regs);
+
+Note that both entry and exit callback has same ptototype. The @entry_ip is
+saved at function entry and passed to exit handler.
+
+@fp
+        This is the address of `fprobe` data structure related to this handler.
+        You can embed the `fprobe` to your data structure and get it by
+        container_of() macro from @fp. The @fp must not be NULL.
+
+@entry_ip
+        This is the entry address of the traced function (both entry and exit).
+
+@regs
+        This is the `pt_regs` data structure at the entry and exit. Note that
+        the instruction pointer of @regs may be different from the @entry_ip
+        in the entry_handler. If you need traced instruction pointer, you need
+        to use @entry_ip. On the other hand, in the exit_handler, the instruction
+        pointer of @regs is set to the currect return address.
+
+Share the callbacks with kprobes
+================================
+
+Since the recursion safety of the fprobe (and ftrace) is a bit different
+from the kprobes, this may cause an issue if user wants to run the same
+code from the fprobe and the kprobes.
+
+The kprobes has per-cpu 'current_kprobe' variable which protects the
+kprobe handler from recursion in any case. On the other hand, the fprobe
+uses only ftrace_test_recursion_trylock(), which will allow interrupt
+context calls another (or same) fprobe during the fprobe user handler is
+running.
+
+This is not a matter in cases if the common callback shared among the
+kprobes and the fprobe has its own recursion detection, or it can handle
+the recursion in the different contexts (normal/interrupt/NMI.)
+But if it relies on the 'current_kprobe' recursion lock, it has to check
+kprobe_running() and use kprobe_busy_*() APIs.
+
+Fprobe has FPROBE_FL_KPROBE_SHARED flag to do this. If your common callback
+code will be shared with kprobes, please set FPROBE_FL_KPROBE_SHARED
+*before* registering the fprobe, like:
+
+.. code-block:: c
+
+ fprobe.flags = FPROBE_FL_KPROBE_SHARED;
+
+ register_fprobe(&fprobe, "func*", NULL);
+
+This will protect your common callback from the nested call.
+
+The missed counter
+==================
+
+The `fprobe` data structure has `fprobe::nmissed` counter field as same as
+kprobes.
+This counter counts up when;
+
+ - fprobe fails to take ftrace_recursion lock. This usually means that a function
+   which is traced by other ftrace users is called from the entry_handler.
+
+ - fprobe fails to setup the function exit because of the shortage of rethook
+   (the shadow stack for hooking the function return.)
+
+Since `fprobe::nmissed` field is counted up in both case, the former case
+will skip both of entry and exit callback, and the latter case will skip exit
+callback, but in both case the counter is just increased by 1.
+
+Note that if you set the FTRACE_OPS_FL_RECURSION and/or FTRACE_OPS_FL_RCU to
+`fprobe::ops::flags` (ftrace_ops::flags) when registering the fprobe, this
+counter may not work correctly, because those will skip fprobe's callback.
+
+
+Functions and structures
+========================
+
+.. kernel-doc:: include/linux/fprobe.h
+.. kernel-doc:: kernel/trace/fprobe.c
+
diff --git a/Documentation/trace/index.rst b/Documentation/trace/index.rst
index 3769b9b7aed8..b9f3757f8269 100644
--- a/Documentation/trace/index.rst
+++ b/Documentation/trace/index.rst
@@ -9,6 +9,7 @@ Linux Tracing Technologies
    tracepoint-analysis
    ftrace
    ftrace-uses
+   fprobe
    kprobes
    kprobetrace
    uprobetracer

[PATCH v11 12/12] fprobe: Add a selftest for fprobe

[Masami Hiramatsu]

Add a KUnit based selftest for fprobe interface.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 Changes in v11:
  - Build selftest only if KUNIT=y.
 Changes in v9:
  - Rename fprobe_target* to fprobe_selftest_target*.
  - Find the correct expected ip by ftrace_location_range().
  - Since the ftrace_location_range() is not exposed to module, make
    this test only for embedded.
  - Add entry only test.
  - Reset the fprobe structure before reuse it.
---
 lib/Kconfig.debug |   12 ++++
 lib/Makefile      |    2 +
 lib/test_fprobe.c |  174 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 188 insertions(+)
 create mode 100644 lib/test_fprobe.c

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 72ca4684beda..b0bf0d224b2c 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -2118,6 +2118,18 @@ config KPROBES_SANITY_TEST
 
 	  Say N if you are unsure.
 
+config FPROBE_SANITY_TEST
+	bool "Self test for fprobe"
+	depends on DEBUG_KERNEL
+	depends on FPROBE
+	depends on KUNIT=y
+	help
+	  This option will enable testing the fprobe when the system boot.
+	  A series of tests are made to verify that the fprobe is functioning
+	  properly.
+
+	  Say N if you are unsure.
+
 config BACKTRACE_SELF_TEST
 	tristate "Self test for the backtrace code"
 	depends on DEBUG_KERNEL
diff --git a/lib/Makefile b/lib/Makefile
index 300f569c626b..154008764b16 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -103,6 +103,8 @@ obj-$(CONFIG_TEST_HMM) += test_hmm.o
 obj-$(CONFIG_TEST_FREE_PAGES) += test_free_pages.o
 obj-$(CONFIG_KPROBES_SANITY_TEST) += test_kprobes.o
 obj-$(CONFIG_TEST_REF_TRACKER) += test_ref_tracker.o
+CFLAGS_test_fprobe.o += $(CC_FLAGS_FTRACE)
+obj-$(CONFIG_FPROBE_SANITY_TEST) += test_fprobe.o
 #
 # CFLAGS for compiling floating point code inside the kernel. x86/Makefile turns
 # off the generation of FPU/SSE* instructions for kernel proper but FPU_FLAGS
diff --git a/lib/test_fprobe.c b/lib/test_fprobe.c
new file mode 100644
index 000000000000..ed70637a2ffa
--- /dev/null
+++ b/lib/test_fprobe.c
@@ -0,0 +1,174 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * test_fprobe.c - simple sanity test for fprobe
+ */
+
+#include <linux/kernel.h>
+#include <linux/fprobe.h>
+#include <linux/random.h>
+#include <kunit/test.h>
+
+#define div_factor 3
+
+static struct kunit *current_test;
+
+static u32 rand1, entry_val, exit_val;
+
+/* Use indirect calls to avoid inlining the target functions */
+static u32 (*target)(u32 value);
+static u32 (*target2)(u32 value);
+static unsigned long target_ip;
+static unsigned long target2_ip;
+
+static noinline u32 fprobe_selftest_target(u32 value)
+{
+	return (value / div_factor);
+}
+
+static noinline u32 fprobe_selftest_target2(u32 value)
+{
+	return (value / div_factor) + 1;
+}
+
+static notrace void fp_entry_handler(struct fprobe *fp, unsigned long ip, struct pt_regs *regs)
+{
+	KUNIT_EXPECT_FALSE(current_test, preemptible());
+	/* This can be called on the fprobe_selftest_target and the fprobe_selftest_target2 */
+	if (ip != target_ip)
+		KUNIT_EXPECT_EQ(current_test, ip, target2_ip);
+	entry_val = (rand1 / div_factor);
+}
+
+static notrace void fp_exit_handler(struct fprobe *fp, unsigned long ip, struct pt_regs *regs)
+{
+	unsigned long ret = regs_return_value(regs);
+
+	KUNIT_EXPECT_FALSE(current_test, preemptible());
+	if (ip != target_ip) {
+		KUNIT_EXPECT_EQ(current_test, ip, target2_ip);
+		KUNIT_EXPECT_EQ(current_test, ret, (rand1 / div_factor) + 1);
+	} else
+		KUNIT_EXPECT_EQ(current_test, ret, (rand1 / div_factor));
+	KUNIT_EXPECT_EQ(current_test, entry_val, (rand1 / div_factor));
+	exit_val = entry_val + div_factor;
+}
+
+/* Test entry only (no rethook) */
+static void test_fprobe_entry(struct kunit *test)
+{
+	struct fprobe fp_entry = {
+		.entry_handler = fp_entry_handler,
+	};
+
+	current_test = test;
+
+	/* Before register, unregister should be failed. */
+	KUNIT_EXPECT_NE(test, 0, unregister_fprobe(&fp_entry));
+	KUNIT_EXPECT_EQ(test, 0, register_fprobe(&fp_entry, "fprobe_selftest_target*", NULL));
+
+	entry_val = 0;
+	exit_val = 0;
+	target(rand1);
+	KUNIT_EXPECT_NE(test, 0, entry_val);
+	KUNIT_EXPECT_EQ(test, 0, exit_val);
+
+	entry_val = 0;
+	exit_val = 0;
+	target2(rand1);
+	KUNIT_EXPECT_NE(test, 0, entry_val);
+	KUNIT_EXPECT_EQ(test, 0, exit_val);
+
+	KUNIT_EXPECT_EQ(test, 0, unregister_fprobe(&fp_entry));
+}
+
+static void test_fprobe(struct kunit *test)
+{
+	struct fprobe fp = {
+		.entry_handler = fp_entry_handler,
+		.exit_handler = fp_exit_handler,
+	};
+
+	current_test = test;
+	KUNIT_EXPECT_EQ(test, 0, register_fprobe(&fp, "fprobe_selftest_target*", NULL));
+
+	entry_val = 0;
+	exit_val = 0;
+	target(rand1);
+	KUNIT_EXPECT_NE(test, 0, entry_val);
+	KUNIT_EXPECT_EQ(test, entry_val + div_factor, exit_val);
+
+	entry_val = 0;
+	exit_val = 0;
+	target2(rand1);
+	KUNIT_EXPECT_NE(test, 0, entry_val);
+	KUNIT_EXPECT_EQ(test, entry_val + div_factor, exit_val);
+
+	KUNIT_EXPECT_EQ(test, 0, unregister_fprobe(&fp));
+}
+
+static void test_fprobe_syms(struct kunit *test)
+{
+	static const char *syms[] = {"fprobe_selftest_target", "fprobe_selftest_target2"};
+	struct fprobe fp = {
+		.entry_handler = fp_entry_handler,
+		.exit_handler = fp_exit_handler,
+	};
+
+	current_test = test;
+	KUNIT_EXPECT_EQ(test, 0, register_fprobe_syms(&fp, syms, 2));
+
+	entry_val = 0;
+	exit_val = 0;
+	target(rand1);
+	KUNIT_EXPECT_NE(test, 0, entry_val);
+	KUNIT_EXPECT_EQ(test, entry_val + div_factor, exit_val);
+
+	entry_val = 0;
+	exit_val = 0;
+	target2(rand1);
+	KUNIT_EXPECT_NE(test, 0, entry_val);
+	KUNIT_EXPECT_EQ(test, entry_val + div_factor, exit_val);
+
+	KUNIT_EXPECT_EQ(test, 0, unregister_fprobe(&fp));
+}
+
+static unsigned long get_ftrace_location(void *func)
+{
+	unsigned long size, addr = (unsigned long)func;
+
+	if (!kallsyms_lookup_size_offset(addr, &size, NULL) || !size)
+		return 0;
+
+	return ftrace_location_range(addr, addr + size - 1);
+}
+
+static int fprobe_test_init(struct kunit *test)
+{
+	do {
+		rand1 = prandom_u32();
+	} while (rand1 <= div_factor);
+
+	target = fprobe_selftest_target;
+	target2 = fprobe_selftest_target2;
+	target_ip = get_ftrace_location(target);
+	target2_ip = get_ftrace_location(target2);
+
+	return 0;
+}
+
+static struct kunit_case fprobe_testcases[] = {
+	KUNIT_CASE(test_fprobe_entry),
+	KUNIT_CASE(test_fprobe),
+	KUNIT_CASE(test_fprobe_syms),
+	{}
+};
+
+static struct kunit_suite fprobe_test_suite = {
+	.name = "fprobe_test",
+	.init = fprobe_test_init,
+	.test_cases = fprobe_testcases,
+};
+
+kunit_test_suites(&fprobe_test_suite);
+
+MODULE_LICENSE("GPL");

Re: [PATCH v11 07/12] ARM: rethook: Add rethook arm implementation

[Masami Hiramatsu]

On Sat, 12 Mar 2022 01:00:03 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:

> +void __naked arch_rethook_trampoline(void)
> +{
> +	__asm__ __volatile__ (
> +#ifdef CONFIG_FRAME_POINTER
> +		"ldr	lr, =arch_rethook_trampoline	\n\t"

Oops, this must have the same issue reported by 0day build bot recently[1].

[1] https://lore.kernel.org/all/202203150516.KTorSVVU-lkp@intel.com/T/#u

I'll update this series with same fix.

Thank you,

> +	/* this makes a framepointer on pt_regs. */
> +#ifdef CONFIG_CC_IS_CLANG
> +		"stmdb	sp, {sp, lr, pc}	\n\t"
> +		"sub	sp, sp, #12		\n\t"
> +		/* In clang case, pt_regs->ip = lr. */
> +		"stmdb	sp!, {r0 - r11, lr}	\n\t"
> +		/* fp points regs->r11 (fp) */
> +		"add	fp, sp,	#44		\n\t"
> +#else /* !CONFIG_CC_IS_CLANG */
> +		/* In gcc case, pt_regs->ip = fp. */
> +		"stmdb	sp, {fp, sp, lr, pc}	\n\t"
> +		"sub	sp, sp, #16		\n\t"
> +		"stmdb	sp!, {r0 - r11}		\n\t"
> +		/* fp points regs->r15 (pc) */
> +		"add	fp, sp, #60		\n\t"
> +#endif /* CONFIG_CC_IS_CLANG */
> +#else /* !CONFIG_FRAME_POINTER */
> +		"sub	sp, sp, #16		\n\t"
> +		"stmdb	sp!, {r0 - r11}		\n\t"
> +#endif /* CONFIG_FRAME_POINTER */
> +		"mov	r0, sp			\n\t"
> +		"bl	arch_rethook_trampoline_callback	\n\t"
> +		"mov	lr, r0			\n\t"
> +		"ldmia	sp!, {r0 - r11}		\n\t"
> +		"add	sp, sp, #16		\n\t"
> +#ifdef CONFIG_THUMB2_KERNEL
> +		"bx	lr			\n\t"
> +#else
> +		"mov	pc, lr			\n\t"
> +#endif
> +		: : : "memory");
> +}
> +NOKPROBE_SYMBOL(arch_rethook_trampoline);
> +
> +/*
> + * At the entry of function with mcount. The stack and registers are prepared
> + * for the mcount function as below.
> + *
> + * mov     ip, sp
> + * push    {fp, ip, lr, pc}
> + * sub     fp, ip, #4	; FP[0] = PC, FP[-4] = LR, and FP[-12] = call-site FP.
> + * push    {lr}
> + * bl      <__gnu_mcount_nc> ; call ftrace
> + *
> + * And when returning from the function, call-site FP, SP and PC are restored
> + * from stack as below;
> + *
> + * ldm     sp, {fp, sp, pc}
> + *
> + * Thus, if the arch_rethook_prepare() is called from real function entry,
> + * it must change the LR and save FP in pt_regs. But if it is called via
> + * mcount context (ftrace), it must change the LR on stack, which is next
> + * to the PC (= FP[-4]), and save the FP value at FP[-12].
> + */
> +void arch_rethook_prepare(struct rethook_node *rh, struct pt_regs *regs, bool mcount)
> +{
> +	unsigned long *ret_addr, *frame;
> +
> +	if (mcount) {
> +		ret_addr = (unsigned long *)(regs->ARM_fp - 4);
> +		frame = (unsigned long *)(regs->ARM_fp - 12);
> +	} else {
> +		ret_addr = &regs->ARM_lr;
> +		frame = &regs->ARM_fp;
> +	}
> +
> +	rh->ret_addr = *ret_addr;
> +	rh->frame = *frame;
> +
> +	/* Replace the return addr with trampoline addr. */
> +	*ret_addr = (unsigned long)arch_rethook_trampoline;
> +}
> +NOKPROBE_SYMBOL(arch_rethook_prepare);
> 


-- 
Masami Hiramatsu <mhiramat@kernel.org>