[for-next][PATCH 00/13] tracing: Updates for 6.5

[for-next][PATCH 00/13] tracing: Updates for 6.5

[Steven Rostedt]

  git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace.git
trace/for-next

Head SHA1: 513f25cdf82cec8eb98b111dc0570116562391e0


Azeem Shaikh (1):
      tracing/boot: Replace strlcpy with strscpy

Daniel Bristot de Oliveira (3):
      tracing/osnoise: Switch from PF_NO_SETAFFINITY to migrate_disable
      tracing/osnoise: Skip running osnoise if all instances are off
      tracing/timerlat: Add user-space interface

Donglin Peng (7):
      function_graph: Support recording and printing the return value of function
      tracing: Add documentation for funcgraph-retval and funcgraph-retval-hex
      arm64: ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL
      x86/ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL
      LoongArch: ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL
      selftests/ftrace: Add funcgraph-retval test case
      riscv: ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL

Jiri Olsa (1):
      ftrace: Show all functions with addresses in available_filter_functions_addrs

Steven Rostedt (Google) (1):
      fgraph: Add declaration of "struct fgraph_ret_regs"

----
 Documentation/trace/ftrace.rst                     | 132 ++++++
 Documentation/trace/timerlat-tracer.rst            |  78 ++++
 arch/arm64/Kconfig                                 |   1 +
 arch/arm64/include/asm/ftrace.h                    |  22 +
 arch/arm64/kernel/asm-offsets.c                    |  13 +
 arch/arm64/kernel/entry-ftrace.S                   |  27 +-
 arch/loongarch/Kconfig                             |   1 +
 arch/loongarch/include/asm/ftrace.h                |  22 +
 arch/loongarch/kernel/asm-offsets.c                |  15 +-
 arch/loongarch/kernel/mcount.S                     |  14 +-
 arch/loongarch/kernel/mcount_dyn.S                 |  15 +-
 arch/riscv/Kconfig                                 |   1 +
 arch/riscv/include/asm/ftrace.h                    |  21 +
 arch/riscv/kernel/mcount.S                         |   7 +-
 arch/x86/Kconfig                                   |   1 +
 arch/x86/include/asm/ftrace.h                      |  20 +
 arch/x86/kernel/ftrace_32.S                        |   8 +-
 arch/x86/kernel/ftrace_64.S                        |   7 +-
 include/linux/ftrace.h                             |   4 +
 kernel/trace/Kconfig                               |  15 +
 kernel/trace/fgraph.c                              |  26 +-
 kernel/trace/ftrace.c                              |  37 ++
 kernel/trace/trace.h                               |   2 +
 kernel/trace/trace_boot.c                          |   8 +-
 kernel/trace/trace_entries.h                       |  26 ++
 kernel/trace/trace_functions_graph.c               |  93 +++-
 kernel/trace/trace_osnoise.c                       | 477 ++++++++++++++++++++-
 kernel/trace/trace_output.c                        |   4 +-
 .../ftrace/test.d/ftrace/fgraph-retval.tc          |  44 ++
 29 files changed, 1079 insertions(+), 62 deletions(-)
 create mode 100644 tools/testing/selftests/ftrace/test.d/ftrace/fgraph-retval.tc

[for-next][PATCH 02/13] function_graph: Support recording and printing the return value of function

[Steven Rostedt]

From: Donglin Peng <pengdonglin@sangfor.com.cn>

Analyzing system call failures with the function_graph tracer can be a
time-consuming process, particularly when locating the kernel function
that first returns an error in the trace logs. This change aims to
simplify the process by recording the function return value to the
'retval' member of 'ftrace_graph_ret' and printing it when outputting
the trace log.

We have introduced new trace options: funcgraph-retval and
funcgraph-retval-hex. The former controls whether to display the return
value, while the latter controls the display format.

Please note that even if a function's return type is void, a return
value will still be printed. You can simply ignore it.

This patch only establishes the fundamental infrastructure. Subsequent
patches will make this feature available on some commonly used processor
architectures.

Here is an example:

I attempted to attach the demo process to a cpu cgroup, but it failed:

echo `pidof demo` > /sys/fs/cgroup/cpu/test/tasks
-bash: echo: write error: Invalid argument

The strace logs indicate that the write system call returned -EINVAL(-22):
...
write(1, "273\n", 4)                    = -1 EINVAL (Invalid argument)
...

To capture trace logs during a write system call, use the following
commands:

cd /sys/kernel/debug/tracing/
echo 0 > tracing_on
echo > trace
echo *sys_write > set_graph_function
echo *spin* > set_graph_notrace
echo *rcu* >> set_graph_notrace
echo *alloc* >> set_graph_notrace
echo preempt* >> set_graph_notrace
echo kfree* >> set_graph_notrace
echo $$ > set_ftrace_pid
echo function_graph > current_tracer
echo 1 > options/funcgraph-retval
echo 0 > options/funcgraph-retval-hex
echo 1 > tracing_on
echo `pidof demo` > /sys/fs/cgroup/cpu/test/tasks
echo 0 > tracing_on
cat trace > ~/trace.log

To locate the root cause, search for error code -22 directly in the file
trace.log and identify the first function that returned -22. Once you
have identified this function, examine its code to determine the root
cause.

For example, in the trace log below, cpu_cgroup_can_attach
returned -22 first, so we can focus our analysis on this function to
identify the root cause.

...

 1)          | cgroup_migrate() {
 1) 0.651 us |   cgroup_migrate_add_task(); /* = 0xffff93fcfd346c00 */
 1)          |   cgroup_migrate_execute() {
 1)          |     cpu_cgroup_can_attach() {
 1)          |       cgroup_taskset_first() {
 1) 0.732 us |         cgroup_taskset_next(); /* = 0xffff93fc8fb20000 */
 1) 1.232 us |       } /* cgroup_taskset_first = 0xffff93fc8fb20000 */
 1) 0.380 us |       sched_rt_can_attach(); /* = 0x0 */
 1) 2.335 us |     } /* cpu_cgroup_can_attach = -22 */
 1) 4.369 us |   } /* cgroup_migrate_execute = -22 */
 1) 7.143 us | } /* cgroup_migrate = -22 */

...

Link: https://lkml.kernel.org/r/1fc502712c981e0e6742185ba242992170ac9da8.1680954589.git.pengdonglin@sangfor.com.cn

Tested-by: Florian Kauer <florian.kauer@linutronix.de>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Donglin Peng <pengdonglin@sangfor.com.cn>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 include/linux/ftrace.h               |  3 +
 kernel/trace/Kconfig                 | 15 +++++
 kernel/trace/fgraph.c                | 23 ++++++-
 kernel/trace/trace.h                 |  2 +
 kernel/trace/trace_entries.h         | 26 ++++++++
 kernel/trace/trace_functions_graph.c | 93 +++++++++++++++++++++++++---
 6 files changed, 151 insertions(+), 11 deletions(-)

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index b23bdd414394..49f279f4c3a1 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -1018,6 +1018,9 @@ struct ftrace_graph_ent {
  */
 struct ftrace_graph_ret {
 	unsigned long func; /* Current function */
+#ifdef CONFIG_FUNCTION_GRAPH_RETVAL
+	unsigned long retval;
+#endif
 	int depth;
 	/* Number of functions that overran the depth limit for current task */
 	unsigned int overrun;
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 8cf97fa4a4b3..abe5c583bd59 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -31,6 +31,9 @@ config HAVE_FUNCTION_GRAPH_TRACER
 	help
 	  See Documentation/trace/ftrace-design.rst
 
+config HAVE_FUNCTION_GRAPH_RETVAL
+	bool
+
 config HAVE_DYNAMIC_FTRACE
 	bool
 	help
@@ -227,6 +230,18 @@ config FUNCTION_GRAPH_TRACER
 	  the return value. This is done by setting the current return
 	  address on the current task structure into a stack of calls.
 
+config FUNCTION_GRAPH_RETVAL
+	bool "Kernel Function Graph Return Value"
+	depends on HAVE_FUNCTION_GRAPH_RETVAL
+	depends on FUNCTION_GRAPH_TRACER
+	default n
+	help
+	  Support recording and printing the function return value when
+	  using function graph tracer. It can be helpful to locate functions
+	  that return errors. This feature is off by default, and you can
+	  enable it via the trace option funcgraph-retval.
+	  See Documentation/trace/ftrace.rst
+
 config DYNAMIC_FTRACE
 	bool "enable/disable function tracing dynamically"
 	depends on FUNCTION_TRACER
diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c
index ea3d7bb235d3..cd2c35b1dd8f 100644
--- a/kernel/trace/fgraph.c
+++ b/kernel/trace/fgraph.c
@@ -243,12 +243,16 @@ struct fgraph_ret_regs;
  * Send the trace to the ring-buffer.
  * @return the original return address.
  */
-unsigned long ftrace_return_to_handler(unsigned long frame_pointer)
+static unsigned long __ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs,
+						unsigned long frame_pointer)
 {
 	struct ftrace_graph_ret trace;
 	unsigned long ret;
 
 	ftrace_pop_return_trace(&trace, &ret, frame_pointer);
+#ifdef CONFIG_FUNCTION_GRAPH_RETVAL
+	trace.retval = fgraph_ret_regs_return_value(ret_regs);
+#endif
 	trace.rettime = trace_clock_local();
 	ftrace_graph_return(&trace);
 	/*
@@ -269,6 +273,23 @@ unsigned long ftrace_return_to_handler(unsigned long frame_pointer)
 	return ret;
 }
 
+/*
+ * After all architecures have selected HAVE_FUNCTION_GRAPH_RETVAL, we can
+ * leave only ftrace_return_to_handler(ret_regs).
+ */
+#ifdef CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
+unsigned long ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs)
+{
+	return __ftrace_return_to_handler(ret_regs,
+				fgraph_ret_regs_frame_pointer(ret_regs));
+}
+#else
+unsigned long ftrace_return_to_handler(unsigned long frame_pointer)
+{
+	return __ftrace_return_to_handler(NULL, frame_pointer);
+}
+#endif
+
 /**
  * ftrace_graph_get_ret_stack - return the entry of the shadow stack
  * @task: The task to read the shadow stack from
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 79bdefe9261b..e6407a27d644 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -832,6 +832,8 @@ static __always_inline bool ftrace_hash_empty(struct ftrace_hash *hash)
 #define TRACE_GRAPH_PRINT_TAIL          0x100
 #define TRACE_GRAPH_SLEEP_TIME          0x200
 #define TRACE_GRAPH_GRAPH_TIME          0x400
+#define TRACE_GRAPH_PRINT_RETVAL        0x800
+#define TRACE_GRAPH_PRINT_RETVAL_HEX    0x1000
 #define TRACE_GRAPH_PRINT_FILL_SHIFT	28
 #define TRACE_GRAPH_PRINT_FILL_MASK	(0x3 << TRACE_GRAPH_PRINT_FILL_SHIFT)
 
diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h
index cd41e863b51c..340b2fa98218 100644
--- a/kernel/trace/trace_entries.h
+++ b/kernel/trace/trace_entries.h
@@ -86,6 +86,30 @@ FTRACE_ENTRY_PACKED(funcgraph_entry, ftrace_graph_ent_entry,
 );
 
 /* Function return entry */
+#ifdef CONFIG_FUNCTION_GRAPH_RETVAL
+
+FTRACE_ENTRY_PACKED(funcgraph_exit, ftrace_graph_ret_entry,
+
+	TRACE_GRAPH_RET,
+
+	F_STRUCT(
+		__field_struct(	struct ftrace_graph_ret,	ret	)
+		__field_packed(	unsigned long,	ret,		func	)
+		__field_packed(	unsigned long,	ret,		retval	)
+		__field_packed(	int,		ret,		depth	)
+		__field_packed(	unsigned int,	ret,		overrun	)
+		__field_packed(	unsigned long long, ret,	calltime)
+		__field_packed(	unsigned long long, ret,	rettime	)
+	),
+
+	F_printk("<-- %ps (%d) (start: %llx  end: %llx) over: %d retval: %lx",
+		 (void *)__entry->func, __entry->depth,
+		 __entry->calltime, __entry->rettime,
+		 __entry->depth, __entry->retval)
+);
+
+#else
+
 FTRACE_ENTRY_PACKED(funcgraph_exit, ftrace_graph_ret_entry,
 
 	TRACE_GRAPH_RET,
@@ -105,6 +129,8 @@ FTRACE_ENTRY_PACKED(funcgraph_exit, ftrace_graph_ret_entry,
 		 __entry->depth)
 );
 
+#endif
+
 /*
  * Context switch trace entry - which task (and prio) we switched from/to:
  *
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 203204cadf92..c35fbaab2a47 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -58,6 +58,12 @@ static struct tracer_opt trace_opts[] = {
 	{ TRACER_OPT(funcgraph-irqs, TRACE_GRAPH_PRINT_IRQS) },
 	/* Display function name after trailing } */
 	{ TRACER_OPT(funcgraph-tail, TRACE_GRAPH_PRINT_TAIL) },
+#ifdef CONFIG_FUNCTION_GRAPH_RETVAL
+	/* Display function return value ? */
+	{ TRACER_OPT(funcgraph-retval, TRACE_GRAPH_PRINT_RETVAL) },
+	/* Display function return value in hexadecimal format ? */
+	{ TRACER_OPT(funcgraph-retval-hex, TRACE_GRAPH_PRINT_RETVAL_HEX) },
+#endif
 	/* Include sleep time (scheduled out) between entry and return */
 	{ TRACER_OPT(sleep-time, TRACE_GRAPH_SLEEP_TIME) },
 
@@ -619,6 +625,56 @@ print_graph_duration(struct trace_array *tr, unsigned long long duration,
 	trace_seq_puts(s, "|  ");
 }
 
+#ifdef CONFIG_FUNCTION_GRAPH_RETVAL
+
+#define __TRACE_GRAPH_PRINT_RETVAL TRACE_GRAPH_PRINT_RETVAL
+
+static void print_graph_retval(struct trace_seq *s, unsigned long retval,
+				bool leaf, void *func, bool hex_format)
+{
+	unsigned long err_code = 0;
+
+	if (retval == 0 || hex_format)
+		goto done;
+
+	/* Check if the return value matches the negative format */
+	if (IS_ENABLED(CONFIG_64BIT) && (retval & BIT(31)) &&
+		(((u64)retval) >> 32) == 0) {
+		/* sign extension */
+		err_code = (unsigned long)(s32)retval;
+	} else {
+		err_code = retval;
+	}
+
+	if (!IS_ERR_VALUE(err_code))
+		err_code = 0;
+
+done:
+	if (leaf) {
+		if (hex_format || (err_code == 0))
+			trace_seq_printf(s, "%ps(); /* = 0x%lx */\n",
+					func, retval);
+		else
+			trace_seq_printf(s, "%ps(); /* = %ld */\n",
+					func, err_code);
+	} else {
+		if (hex_format || (err_code == 0))
+			trace_seq_printf(s, "} /* %ps = 0x%lx */\n",
+					func, retval);
+		else
+			trace_seq_printf(s, "} /* %ps = %ld */\n",
+					func, err_code);
+	}
+}
+
+#else
+
+#define __TRACE_GRAPH_PRINT_RETVAL 0
+
+#define print_graph_retval(_seq, _retval, _leaf, _func, _format) do {} while (0)
+
+#endif
+
 /* Case of a leaf function on its call entry */
 static enum print_line_t
 print_graph_entry_leaf(struct trace_iterator *iter,
@@ -663,7 +719,15 @@ print_graph_entry_leaf(struct trace_iterator *iter,
 	for (i = 0; i < call->depth * TRACE_GRAPH_INDENT; i++)
 		trace_seq_putc(s, ' ');
 
-	trace_seq_printf(s, "%ps();\n", (void *)call->func);
+	/*
+	 * Write out the function return value if the option function-retval is
+	 * enabled.
+	 */
+	if (flags & __TRACE_GRAPH_PRINT_RETVAL)
+		print_graph_retval(s, graph_ret->retval, true, (void *)call->func,
+				!!(flags & TRACE_GRAPH_PRINT_RETVAL_HEX));
+	else
+		trace_seq_printf(s, "%ps();\n", (void *)call->func);
 
 	print_graph_irq(iter, graph_ret->func, TRACE_GRAPH_RET,
 			cpu, iter->ent->pid, flags);
@@ -942,16 +1006,25 @@ print_graph_return(struct ftrace_graph_ret *trace, struct trace_seq *s,
 		trace_seq_putc(s, ' ');
 
 	/*
-	 * If the return function does not have a matching entry,
-	 * then the entry was lost. Instead of just printing
-	 * the '}' and letting the user guess what function this
-	 * belongs to, write out the function name. Always do
-	 * that if the funcgraph-tail option is enabled.
+	 * Always write out the function name and its return value if the
+	 * function-retval option is enabled.
 	 */
-	if (func_match && !(flags & TRACE_GRAPH_PRINT_TAIL))
-		trace_seq_puts(s, "}\n");
-	else
-		trace_seq_printf(s, "} /* %ps */\n", (void *)trace->func);
+	if (flags & __TRACE_GRAPH_PRINT_RETVAL) {
+		print_graph_retval(s, trace->retval, false, (void *)trace->func,
+			!!(flags & TRACE_GRAPH_PRINT_RETVAL_HEX));
+	} else {
+		/*
+		 * If the return function does not have a matching entry,
+		 * then the entry was lost. Instead of just printing
+		 * the '}' and letting the user guess what function this
+		 * belongs to, write out the function name. Always do
+		 * that if the funcgraph-tail option is enabled.
+		 */
+		if (func_match && !(flags & TRACE_GRAPH_PRINT_TAIL))
+			trace_seq_puts(s, "}\n");
+		else
+			trace_seq_printf(s, "} /* %ps */\n", (void *)trace->func);
+	}
 
 	/* Overrun */
 	if (flags & TRACE_GRAPH_PRINT_OVERRUN)
-- 
2.39.2

[for-next][PATCH 03/13] tracing: Add documentation for funcgraph-retval and funcgraph-retval-hex

[Steven Rostedt]

From: Donglin Peng <pengdonglin@sangfor.com.cn>

Add documentation for the two newly introduced options for the
function_graph tracer. The funcgraph-retval option is used to
control whether or not to display the return value, while the
funcgraph-retval-hex option is used to control the display
format of the return value.

Link: https://lkml.kernel.org/r/2b5635f05146161b54c9ea6307e25efe5ccebdad.1680954589.git.pengdonglin@sangfor.com.cn

Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Donglin Peng <pengdonglin@sangfor.com.cn>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 Documentation/trace/ftrace.rst | 126 +++++++++++++++++++++++++++++++++
 1 file changed, 126 insertions(+)

diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst
index 027437b745a0..df2d3e57a83f 100644
--- a/Documentation/trace/ftrace.rst
+++ b/Documentation/trace/ftrace.rst
@@ -1359,6 +1359,19 @@ Options for function_graph tracer:
 	only a closing curly bracket "}" is displayed for
 	the return of a function.
 
+  funcgraph-retval
+	When set, the return value of each traced function
+	will be printed after an equal sign "=". By default
+	this is off.
+
+  funcgraph-retval-hex
+	When set, the return value will always be printed
+	in hexadecimal format. If the option is not set and
+	the return value is an error code, it will be printed
+	in signed decimal format; otherwise it will also be
+	printed in hexadecimal format. By default, this option
+	is off.
+
   sleep-time
 	When running function graph tracer, to include
 	the time a task schedules out in its function.
@@ -2704,6 +2717,119 @@ It is default disabled.
     0)   1.757 us    |        } /* kmem_cache_free() */
     0)   2.861 us    |      } /* putname() */
 
+The return value of each traced function can be displayed after
+an equal sign "=". When encountering system call failures, it
+can be verfy helpful to quickly locate the function that first
+returns an error code.
+
+	- hide: echo nofuncgraph-retval > trace_options
+	- show: echo funcgraph-retval > trace_options
+
+  Example with funcgraph-retval::
+
+    1)               |    cgroup_migrate() {
+    1)   0.651 us    |      cgroup_migrate_add_task(); /* = 0xffff93fcfd346c00 */
+    1)               |      cgroup_migrate_execute() {
+    1)               |        cpu_cgroup_can_attach() {
+    1)               |          cgroup_taskset_first() {
+    1)   0.732 us    |            cgroup_taskset_next(); /* = 0xffff93fc8fb20000 */
+    1)   1.232 us    |          } /* cgroup_taskset_first = 0xffff93fc8fb20000 */
+    1)   0.380 us    |          sched_rt_can_attach(); /* = 0x0 */
+    1)   2.335 us    |        } /* cpu_cgroup_can_attach = -22 */
+    1)   4.369 us    |      } /* cgroup_migrate_execute = -22 */
+    1)   7.143 us    |    } /* cgroup_migrate = -22 */
+
+The above example shows that the function cpu_cgroup_can_attach
+returned the error code -22 firstly, then we can read the code
+of this function to get the root cause.
+
+When the option funcgraph-retval-hex is not set, the return value can
+be displayed in a smart way. Specifically, if it is an error code,
+it will be printed in signed decimal format, otherwise it will
+printed in hexadecimal format.
+
+	- smart: echo nofuncgraph-retval-hex > trace_options
+	- hexadecimal: echo funcgraph-retval-hex > trace_options
+
+  Example with funcgraph-retval-hex::
+
+    1)               |      cgroup_migrate() {
+    1)   0.651 us    |        cgroup_migrate_add_task(); /* = 0xffff93fcfd346c00 */
+    1)               |        cgroup_migrate_execute() {
+    1)               |          cpu_cgroup_can_attach() {
+    1)               |            cgroup_taskset_first() {
+    1)   0.732 us    |              cgroup_taskset_next(); /* = 0xffff93fc8fb20000 */
+    1)   1.232 us    |            } /* cgroup_taskset_first = 0xffff93fc8fb20000 */
+    1)   0.380 us    |            sched_rt_can_attach(); /* = 0x0 */
+    1)   2.335 us    |          } /* cpu_cgroup_can_attach = 0xffffffea */
+    1)   4.369 us    |        } /* cgroup_migrate_execute = 0xffffffea */
+    1)   7.143 us    |      } /* cgroup_migrate = 0xffffffea */
+
+At present, there are some limitations when using the funcgraph-retval
+option, and these limitations will be eliminated in the future:
+
+- Even if the function return type is void, a return value will still
+  be printed, and you can just ignore it.
+
+- Even if return values are stored in multiple registers, only the
+  value contained in the first register will be recorded and printed.
+  To illustrate, in the x86 architecture, eax and edx are used to store
+  a 64-bit return value, with the lower 32 bits saved in eax and the
+  upper 32 bits saved in edx. However, only the value stored in eax
+  will be recorded and printed.
+
+- In certain procedure call standards, such as arm64's AAPCS64, when a
+  type is smaller than a GPR, it is the responsibility of the consumer
+  to perform the narrowing, and the upper bits may contain UNKNOWN values.
+  Therefore, it is advisable to check the code for such cases. For instance,
+  when using a u8 in a 64-bit GPR, bits [63:8] may contain arbitrary values,
+  especially when larger types are truncated, whether explicitly or implicitly.
+  Here are some specific cases to illustrate this point:
+
+  **Case One**::
+
+  The function narrow_to_u8 is defined as follows::
+
+	u8 narrow_to_u8(u64 val)
+	{
+		// implicitly truncated
+		return val;
+	}
+
+  It may be compiled to::
+
+	narrow_to_u8:
+		< ... ftrace instrumentation ... >
+		RET
+
+  If you pass 0x123456789abcdef to this function and want to narrow it,
+  it may be recorded as 0x123456789abcdef instead of 0xef.
+
+  **Case Two**::
+
+  The function error_if_not_4g_aligned is defined as follows::
+
+	int error_if_not_4g_aligned(u64 val)
+	{
+		if (val & GENMASK(31, 0))
+			return -EINVAL;
+
+		return 0;
+	}
+
+  It could be compiled to::
+
+	error_if_not_4g_aligned:
+		CBNZ    w0, .Lnot_aligned
+		RET			// bits [31:0] are zero, bits
+					// [63:32] are UNKNOWN
+	.Lnot_aligned:
+		MOV    x0, #-EINVAL
+		RET
+
+  When passing 0x2_0000_0000 to it, the return value may be recorded as
+  0x2_0000_0000 instead of 0.
+
 You can put some comments on specific functions by using
 trace_printk() For example, if you want to put a comment inside
 the __might_sleep() function, you just have to include
-- 
2.39.2

[for-next][PATCH 04/13] arm64: ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL

[Steven Rostedt]

From: Donglin Peng <pengdonglin@sangfor.com.cn>

The previous patch ("function_graph: Support recording and printing
the return value of function") has laid the groundwork for the for
the funcgraph-retval, and this modification makes it available on
the ARM64 platform.

We introduce a new structure called fgraph_ret_regs for the ARM64
platform to hold return registers and the frame pointer. We then
fill its content in the return_to_handler and pass its address to
the function ftrace_return_to_handler to record the return value.

Link: https://lkml.kernel.org/r/c78366416ce93f704ae7000c4ee60eb4258c38f7.1680954589.git.pengdonglin@sangfor.com.cn

Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Donglin Peng <pengdonglin@sangfor.com.cn>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 arch/arm64/Kconfig               |  1 +
 arch/arm64/include/asm/ftrace.h  | 22 ++++++++++++++++++++++
 arch/arm64/kernel/asm-offsets.c  | 13 +++++++++++++
 arch/arm64/kernel/entry-ftrace.S | 27 ++++++++++++++-------------
 4 files changed, 50 insertions(+), 13 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index b1201d25a8a4..f90b1780ea6c 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -201,6 +201,7 @@ config ARM64
 	select HAVE_FTRACE_MCOUNT_RECORD
 	select HAVE_FUNCTION_TRACER
 	select HAVE_FUNCTION_ERROR_INJECTION
+	select HAVE_FUNCTION_GRAPH_RETVAL if HAVE_FUNCTION_GRAPH_TRACER
 	select HAVE_FUNCTION_GRAPH_TRACER
 	select HAVE_GCC_PLUGINS
 	select HAVE_HW_BREAKPOINT if PERF_EVENTS
diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h
index b87d70b693c6..21ac1c5c71d3 100644
--- a/arch/arm64/include/asm/ftrace.h
+++ b/arch/arm64/include/asm/ftrace.h
@@ -192,4 +192,26 @@ static inline bool arch_syscall_match_sym_name(const char *sym,
 }
 #endif /* ifndef __ASSEMBLY__ */
 
+#ifndef __ASSEMBLY__
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+struct fgraph_ret_regs {
+	/* x0 - x7 */
+	unsigned long regs[8];
+
+	unsigned long fp;
+	unsigned long __unused;
+};
+
+static inline unsigned long fgraph_ret_regs_return_value(struct fgraph_ret_regs *ret_regs)
+{
+	return ret_regs->regs[0];
+}
+
+static inline unsigned long fgraph_ret_regs_frame_pointer(struct fgraph_ret_regs *ret_regs)
+{
+	return ret_regs->fp;
+}
+#endif /* ifdef CONFIG_FUNCTION_GRAPH_TRACER  */
+#endif
+
 #endif /* __ASM_FTRACE_H */
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index 0996094b0d22..757d01a68ffd 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -200,6 +200,19 @@ int main(void)
 #endif
 #ifdef CONFIG_FUNCTION_TRACER
   DEFINE(FTRACE_OPS_FUNC,		offsetof(struct ftrace_ops, func));
+#endif
+  BLANK();
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+  DEFINE(FGRET_REGS_X0,			offsetof(struct fgraph_ret_regs, regs[0]));
+  DEFINE(FGRET_REGS_X1,			offsetof(struct fgraph_ret_regs, regs[1]));
+  DEFINE(FGRET_REGS_X2,			offsetof(struct fgraph_ret_regs, regs[2]));
+  DEFINE(FGRET_REGS_X3,			offsetof(struct fgraph_ret_regs, regs[3]));
+  DEFINE(FGRET_REGS_X4,			offsetof(struct fgraph_ret_regs, regs[4]));
+  DEFINE(FGRET_REGS_X5,			offsetof(struct fgraph_ret_regs, regs[5]));
+  DEFINE(FGRET_REGS_X6,			offsetof(struct fgraph_ret_regs, regs[6]));
+  DEFINE(FGRET_REGS_X7,			offsetof(struct fgraph_ret_regs, regs[7]));
+  DEFINE(FGRET_REGS_FP,			offsetof(struct fgraph_ret_regs, fp));
+  DEFINE(FGRET_REGS_SIZE,		sizeof(struct fgraph_ret_regs));
 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
   DEFINE(FTRACE_OPS_DIRECT_CALL,	offsetof(struct ftrace_ops, direct_call));
 #endif
diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S
index 1c38a60575aa..f0c16640ef21 100644
--- a/arch/arm64/kernel/entry-ftrace.S
+++ b/arch/arm64/kernel/entry-ftrace.S
@@ -330,22 +330,23 @@ SYM_FUNC_END(ftrace_stub_graph)
  */
 SYM_CODE_START(return_to_handler)
 	/* save return value regs */
-	sub sp, sp, #64
-	stp x0, x1, [sp]
-	stp x2, x3, [sp, #16]
-	stp x4, x5, [sp, #32]
-	stp x6, x7, [sp, #48]
+	sub sp, sp, #FGRET_REGS_SIZE
+	stp x0, x1, [sp, #FGRET_REGS_X0]
+	stp x2, x3, [sp, #FGRET_REGS_X2]
+	stp x4, x5, [sp, #FGRET_REGS_X4]
+	stp x6, x7, [sp, #FGRET_REGS_X6]
+	str x29,    [sp, #FGRET_REGS_FP]	// parent's fp
 
-	mov	x0, x29			//     parent's fp
-	bl	ftrace_return_to_handler// addr = ftrace_return_to_hander(fp);
-	mov	x30, x0			// restore the original return address
+	mov	x0, sp
+	bl	ftrace_return_to_handler	// addr = ftrace_return_to_hander(regs);
+	mov	x30, x0				// restore the original return address
 
 	/* restore return value regs */
-	ldp x0, x1, [sp]
-	ldp x2, x3, [sp, #16]
-	ldp x4, x5, [sp, #32]
-	ldp x6, x7, [sp, #48]
-	add sp, sp, #64
+	ldp x0, x1, [sp, #FGRET_REGS_X0]
+	ldp x2, x3, [sp, #FGRET_REGS_X2]
+	ldp x4, x5, [sp, #FGRET_REGS_X4]
+	ldp x6, x7, [sp, #FGRET_REGS_X6]
+	add sp, sp, #FGRET_REGS_SIZE
 
 	ret
 SYM_CODE_END(return_to_handler)
-- 
2.39.2

[for-next][PATCH 05/13] x86/ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL

[Steven Rostedt]

From: Donglin Peng <pengdonglin@sangfor.com.cn>

The previous patch ("function_graph: Support recording and printing
the return value of function") has laid the groundwork for the for
the funcgraph-retval, and this modification makes it available on
the x86 platform.

We introduce a new structure called fgraph_ret_regs for the x86
platform to hold return registers and the frame pointer. We then
fill its content in the return_to_handler and pass its address
to the function ftrace_return_to_handler to record the return
value.

Link: https://lkml.kernel.org/r/53a506f0f18ff4b7aeb0feb762f1c9a5e9b83ee9.1680954589.git.pengdonglin@sangfor.com.cn

Signed-off-by: Donglin Peng <pengdonglin@sangfor.com.cn>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 arch/x86/Kconfig              |  1 +
 arch/x86/include/asm/ftrace.h | 20 ++++++++++++++++++++
 arch/x86/kernel/ftrace_32.S   |  8 +++++---
 arch/x86/kernel/ftrace_64.S   |  7 ++++---
 4 files changed, 30 insertions(+), 6 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 53bab123a8ee..da5c081d64a5 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -216,6 +216,7 @@ config X86
 	select HAVE_FAST_GUP
 	select HAVE_FENTRY			if X86_64 || DYNAMIC_FTRACE
 	select HAVE_FTRACE_MCOUNT_RECORD
+	select HAVE_FUNCTION_GRAPH_RETVAL	if HAVE_FUNCTION_GRAPH_TRACER
 	select HAVE_FUNCTION_GRAPH_TRACER	if X86_32 || (X86_64 && DYNAMIC_FTRACE)
 	select HAVE_FUNCTION_TRACER
 	select HAVE_GCC_PLUGINS
diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h
index 5061ac98ffa1..38d1df9aed37 100644
--- a/arch/x86/include/asm/ftrace.h
+++ b/arch/x86/include/asm/ftrace.h
@@ -147,4 +147,24 @@ static inline bool arch_trace_is_compat_syscall(struct pt_regs *regs)
 #endif /* !COMPILE_OFFSETS */
 #endif /* !__ASSEMBLY__ */
 
+#ifndef __ASSEMBLY__
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+struct fgraph_ret_regs {
+	unsigned long ax;
+	unsigned long dx;
+	unsigned long bp;
+};
+
+static inline unsigned long fgraph_ret_regs_return_value(struct fgraph_ret_regs *ret_regs)
+{
+	return ret_regs->ax;
+}
+
+static inline unsigned long fgraph_ret_regs_frame_pointer(struct fgraph_ret_regs *ret_regs)
+{
+	return ret_regs->bp;
+}
+#endif /* ifdef CONFIG_FUNCTION_GRAPH_TRACER */
+#endif
+
 #endif /* _ASM_X86_FTRACE_H */
diff --git a/arch/x86/kernel/ftrace_32.S b/arch/x86/kernel/ftrace_32.S
index 0d9a14528176..24c1175a47e2 100644
--- a/arch/x86/kernel/ftrace_32.S
+++ b/arch/x86/kernel/ftrace_32.S
@@ -187,12 +187,14 @@ SYM_CODE_END(ftrace_graph_caller)
 
 .globl return_to_handler
 return_to_handler:
-	pushl	%eax
+	pushl	$0
 	pushl	%edx
-	movl	$0, %eax
+	pushl	%eax
+	movl	%esp, %eax
 	call	ftrace_return_to_handler
 	movl	%eax, %ecx
-	popl	%edx
 	popl	%eax
+	popl	%edx
+	addl	$4, %esp		# skip ebp
 	JMP_NOSPEC ecx
 #endif
diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S
index b8c720b5dab2..945cfa5f7239 100644
--- a/arch/x86/kernel/ftrace_64.S
+++ b/arch/x86/kernel/ftrace_64.S
@@ -348,12 +348,13 @@ STACK_FRAME_NON_STANDARD_FP(__fentry__)
 SYM_CODE_START(return_to_handler)
 	UNWIND_HINT_UNDEFINED
 	ANNOTATE_NOENDBR
-	subq  $16, %rsp
+	subq  $24, %rsp
 
 	/* Save the return values */
 	movq %rax, (%rsp)
 	movq %rdx, 8(%rsp)
-	movq %rbp, %rdi
+	movq %rbp, 16(%rsp)
+	movq %rsp, %rdi
 
 	call ftrace_return_to_handler
 
@@ -361,7 +362,7 @@ SYM_CODE_START(return_to_handler)
 	movq 8(%rsp), %rdx
 	movq (%rsp), %rax
 
-	addq $16, %rsp
+	addq $24, %rsp
 	/*
 	 * Jump back to the old return address. This cannot be JMP_NOSPEC rdi
 	 * since IBT would demand that contain ENDBR, which simply isn't so for
-- 
2.39.2

[for-next][PATCH 06/13] LoongArch: ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL

[Steven Rostedt]

From: Donglin Peng <pengdonglin@sangfor.com.cn>

The previous patch ("function_graph: Support recording and printing
the return value of function") has laid the groundwork for the for
the funcgraph-retval, and this modification makes it available on
the LoongArch platform.

We introduce a new structure called fgraph_ret_regs for the LoongArch
platform to hold return registers and the frame pointer. We then fill
its content in the return_to_handler and pass its address to the
function ftrace_return_to_handler to record the return value.

Link: https://lkml.kernel.org/r/c5462255e435fab363895c2d7433bc0f5a140411.1680954589.git.pengdonglin@sangfor.com.cn

Reviewed-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Donglin Peng <pengdonglin@sangfor.com.cn>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 arch/loongarch/Kconfig              |  1 +
 arch/loongarch/include/asm/ftrace.h | 22 ++++++++++++++++++++++
 arch/loongarch/kernel/asm-offsets.c | 15 ++++++++++++++-
 arch/loongarch/kernel/mcount.S      | 14 ++++++++------
 arch/loongarch/kernel/mcount_dyn.S  | 15 ++++++++-------
 5 files changed, 53 insertions(+), 14 deletions(-)

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index d38b066fc931..6c465619b43d 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -103,6 +103,7 @@ config LOONGARCH
 	select HAVE_FTRACE_MCOUNT_RECORD
 	select HAVE_FUNCTION_ARG_ACCESS_API
 	select HAVE_FUNCTION_ERROR_INJECTION
+	select HAVE_FUNCTION_GRAPH_RETVAL if HAVE_FUNCTION_GRAPH_TRACER
 	select HAVE_FUNCTION_GRAPH_TRACER
 	select HAVE_FUNCTION_TRACER
 	select HAVE_GENERIC_VDSO
diff --git a/arch/loongarch/include/asm/ftrace.h b/arch/loongarch/include/asm/ftrace.h
index 23e2ba78dcb0..a11996eb5892 100644
--- a/arch/loongarch/include/asm/ftrace.h
+++ b/arch/loongarch/include/asm/ftrace.h
@@ -100,4 +100,26 @@ __arch_ftrace_set_direct_caller(struct pt_regs *regs, unsigned long addr)
 
 #endif /* CONFIG_FUNCTION_TRACER */
 
+#ifndef __ASSEMBLY__
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+struct fgraph_ret_regs {
+	/* a0 - a1 */
+	unsigned long regs[2];
+
+	unsigned long fp;
+	unsigned long __unused;
+};
+
+static inline unsigned long fgraph_ret_regs_return_value(struct fgraph_ret_regs *ret_regs)
+{
+	return ret_regs->regs[0];
+}
+
+static inline unsigned long fgraph_ret_regs_frame_pointer(struct fgraph_ret_regs *ret_regs)
+{
+	return ret_regs->fp;
+}
+#endif /* ifdef CONFIG_FUNCTION_GRAPH_TRACER */
+#endif
+
 #endif /* _ASM_LOONGARCH_FTRACE_H */
diff --git a/arch/loongarch/kernel/asm-offsets.c b/arch/loongarch/kernel/asm-offsets.c
index 4bdb203fc66e..505e4bf59603 100644
--- a/arch/loongarch/kernel/asm-offsets.c
+++ b/arch/loongarch/kernel/asm-offsets.c
@@ -12,6 +12,7 @@
 #include <asm/cpu-info.h>
 #include <asm/ptrace.h>
 #include <asm/processor.h>
+#include <asm/ftrace.h>
 
 void output_ptreg_defines(void)
 {
@@ -264,7 +265,7 @@ void output_smpboot_defines(void)
 #ifdef CONFIG_HIBERNATION
 void output_pbe_defines(void)
 {
-	COMMENT(" Linux struct pbe offsets. ");
+	COMMENT("Linux struct pbe offsets.");
 	OFFSET(PBE_ADDRESS, pbe, address);
 	OFFSET(PBE_ORIG_ADDRESS, pbe, orig_address);
 	OFFSET(PBE_NEXT, pbe, next);
@@ -272,3 +273,15 @@ void output_pbe_defines(void)
 	BLANK();
 }
 #endif
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+void output_fgraph_ret_regs_defines(void)
+{
+	COMMENT("LoongArch fgraph_ret_regs offsets.");
+	OFFSET(FGRET_REGS_A0, fgraph_ret_regs, regs[0]);
+	OFFSET(FGRET_REGS_A1, fgraph_ret_regs, regs[1]);
+	OFFSET(FGRET_REGS_FP, fgraph_ret_regs, fp);
+	DEFINE(FGRET_REGS_SIZE, sizeof(struct fgraph_ret_regs));
+	BLANK();
+}
+#endif
diff --git a/arch/loongarch/kernel/mcount.S b/arch/loongarch/kernel/mcount.S
index 8cdc1563cd33..cb8e5803de4b 100644
--- a/arch/loongarch/kernel/mcount.S
+++ b/arch/loongarch/kernel/mcount.S
@@ -79,18 +79,20 @@ SYM_FUNC_START(ftrace_graph_caller)
 SYM_FUNC_END(ftrace_graph_caller)
 
 SYM_FUNC_START(return_to_handler)
-	PTR_ADDI	sp, sp, -2 * SZREG
-	PTR_S		a0, sp, 0
-	PTR_S		a1, sp, SZREG
+	PTR_ADDI	sp, sp, -FGRET_REGS_SIZE
+	PTR_S		a0, sp, FGRET_REGS_A0
+	PTR_S		a1, sp, FGRET_REGS_A1
+	PTR_S		zero, sp, FGRET_REGS_FP
 
+	move		a0, sp
 	bl		ftrace_return_to_handler
 
 	/* Restore the real parent address: a0 -> ra */
 	move		ra, a0
 
-	PTR_L		a0, sp, 0
-	PTR_L		a1, sp, SZREG
-	PTR_ADDI	sp, sp, 2 * SZREG
+	PTR_L		a0, sp, FGRET_REGS_A0
+	PTR_L		a1, sp, FGRET_REGS_A1
+	PTR_ADDI	sp, sp, FGRET_REGS_SIZE
 	jr		ra
 SYM_FUNC_END(return_to_handler)
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
diff --git a/arch/loongarch/kernel/mcount_dyn.S b/arch/loongarch/kernel/mcount_dyn.S
index c7d961fc72c2..e16ab0b98e5a 100644
--- a/arch/loongarch/kernel/mcount_dyn.S
+++ b/arch/loongarch/kernel/mcount_dyn.S
@@ -136,18 +136,19 @@ SYM_CODE_END(ftrace_graph_caller)
 
 SYM_CODE_START(return_to_handler)
 	/* Save return value regs */
-	PTR_ADDI 	sp, sp, -2 * SZREG
-	PTR_S		a0, sp, 0
-	PTR_S		a1, sp, SZREG
+	PTR_ADDI	sp, sp, -FGRET_REGS_SIZE
+	PTR_S		a0, sp, FGRET_REGS_A0
+	PTR_S		a1, sp, FGRET_REGS_A1
+	PTR_S		zero, sp, FGRET_REGS_FP
 
-	move		a0, zero
+	move		a0, sp
 	bl		ftrace_return_to_handler
 	move		ra, a0
 
 	/* Restore return value regs */
-	PTR_L		a0, sp, 0
-	PTR_L		a1, sp, SZREG
-	PTR_ADDI 	sp, sp, 2 * SZREG
+	PTR_L		a0, sp, FGRET_REGS_A0
+	PTR_L		a1, sp, FGRET_REGS_A1
+	PTR_ADDI	sp, sp, FGRET_REGS_SIZE
 
 	jr		ra
 SYM_CODE_END(return_to_handler)
-- 
2.39.2

[for-next][PATCH 07/13] selftests/ftrace: Add funcgraph-retval test case

[Steven Rostedt]

From: Donglin Peng <pengdonglin@sangfor.com.cn>

Add a test case for the funcgraph-retval and funcgraph-retval-hex
trace options.

Link: https://lkml.kernel.org/r/9fedbd25e63f012cade5dad13be21225fec2fb5d.1680954589.git.pengdonglin@sangfor.com.cn

Signed-off-by: Donglin Peng <pengdonglin@sangfor.com.cn>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 .../ftrace/test.d/ftrace/fgraph-retval.tc     | 44 +++++++++++++++++++
 1 file changed, 44 insertions(+)
 create mode 100644 tools/testing/selftests/ftrace/test.d/ftrace/fgraph-retval.tc

diff --git a/tools/testing/selftests/ftrace/test.d/ftrace/fgraph-retval.tc b/tools/testing/selftests/ftrace/test.d/ftrace/fgraph-retval.tc
new file mode 100644
index 000000000000..e34c0bdef3ed
--- /dev/null
+++ b/tools/testing/selftests/ftrace/test.d/ftrace/fgraph-retval.tc
@@ -0,0 +1,44 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# description: ftrace - function graph print function return value
+# requires: options/funcgraph-retval options/funcgraph-retval-hex function_graph:tracer
+
+# Make sure that funcgraph-retval works
+
+fail() { # msg
+    echo $1
+    exit_fail
+}
+
+disable_tracing
+clear_trace
+
+# get self PID, can not use $$, because it is PPID
+read PID _ < /proc/self/stat
+
+[ -f set_ftrace_filter ] && echo proc_reg_write > set_ftrace_filter
+[ -f set_ftrace_pid ] && echo ${PID} > set_ftrace_pid
+echo function_graph > current_tracer
+echo 1 > options/funcgraph-retval
+
+set +e
+enable_tracing
+echo > /proc/interrupts
+disable_tracing
+set -e
+
+: "Test printing the error code in signed decimal format"
+echo 0 > options/funcgraph-retval-hex
+count=`cat trace | grep 'proc_reg_write' | grep '= -5' | wc -l`
+if [ $count -eq 0 ]; then
+    fail "Return value can not be printed in signed decimal format"
+fi
+
+: "Test printing the error code in hexadecimal format"
+echo 1 > options/funcgraph-retval-hex
+count=`cat trace | grep 'proc_reg_write' | grep 'fffffffb' | wc -l`
+if [ $count -eq 0 ]; then
+    fail "Return value can not be printed in hexadecimal format"
+fi
+
+exit 0
-- 
2.39.2

[for-next][PATCH 08/13] ftrace: Show all functions with addresses in available_filter_functions_addrs

[Steven Rostedt]

From: Jiri Olsa <jolsa@kernel.org>

Adding new available_filter_functions_addrs file that shows all available
functions (same as available_filter_functions) together with addresses,
like:

  # cat available_filter_functions_addrs | head
  ffffffff81000770 __traceiter_initcall_level
  ffffffff810007c0 __traceiter_initcall_start
  ffffffff81000810 __traceiter_initcall_finish
  ffffffff81000860 trace_initcall_finish_cb
  ...

Note displayed address is the patch-site address and can differ from
/proc/kallsyms address.

It's useful to have address avilable for traceable symbols, so we don't
need to allways cross check kallsyms with available_filter_functions
(or the other way around) and have all the data in single file.

For backwards compatibility reasons we can't change the existing
available_filter_functions file output, but we need to add new file.

The problem is that we need to do 2 passes:

 - through available_filter_functions and find out if the function is traceable
 - through /proc/kallsyms to get the address for traceable function

Having available_filter_functions symbols together with addresses allow
us to skip the kallsyms step and we are ok with the address in
available_filter_functions_addr not being the function entry, because
kprobe_multi uses fprobe and that handles both entry and patch-site
address properly.

We have 2 interfaces how to create kprobe_multi link:

  a) passing symbols to kernel

     1) user gathers symbols and need to ensure that they are
        trace-able -> pass through available_filter_functions file

     2) kernel takes those symbols and translates them to addresses
        through kallsyms api

     3) addresses are passed to fprobe/ftrace through:

         register_fprobe_ips
         -> ftrace_set_filter_ips

  b) passing addresses to kernel

     1) user gathers symbols and needs to ensure that they are
        trace-able -> pass through available_filter_functions file

     2) user takes those symbols and translates them to addresses
       through /proc/kallsyms

     3) addresses are passed to the kernel and kernel calls:

         register_fprobe_ips
         -> ftrace_set_filter_ips

The new available_filter_functions_addrs file helps us with option b),
because we can make 'b 1' and 'b 2' in one step - while filtering traceable
functions, we get the address directly.

Link: https://lore.kernel.org/linux-trace-kernel/20230611130029.1202298-1-jolsa@kernel.org

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Jackie Liu <liu.yun@linux.dev>
Suggested-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 Documentation/trace/ftrace.rst |  6 ++++++
 include/linux/ftrace.h         |  1 +
 kernel/trace/ftrace.c          | 37 ++++++++++++++++++++++++++++++++++
 3 files changed, 44 insertions(+)

diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst
index df2d3e57a83f..b7308ab10c0e 100644
--- a/Documentation/trace/ftrace.rst
+++ b/Documentation/trace/ftrace.rst
@@ -324,6 +324,12 @@ of ftrace. Here is a list of some of the key files:
 	"set_graph_function", or "set_graph_notrace".
 	(See the section "dynamic ftrace" below for more details.)
 
+  available_filter_functions_addrs:
+
+	Similar to available_filter_functions, but with address displayed
+	for each function. The displayed address is the patch-site address
+	and can differ from /proc/kallsyms address.
+
   dyn_ftrace_total_info:
 
 	This file is for debugging purposes. The number of functions that
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 49f279f4c3a1..8e59bd954153 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -633,6 +633,7 @@ enum {
 	FTRACE_ITER_MOD		= (1 << 5),
 	FTRACE_ITER_ENABLED	= (1 << 6),
 	FTRACE_ITER_TOUCHED	= (1 << 7),
+	FTRACE_ITER_ADDRS	= (1 << 8),
 };
 
 void arch_ftrace_update_code(int command);
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 764668467155..b24c573934af 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -3861,6 +3861,9 @@ static int t_show(struct seq_file *m, void *v)
 	if (!rec)
 		return 0;
 
+	if (iter->flags & FTRACE_ITER_ADDRS)
+		seq_printf(m, "%lx ", rec->ip);
+
 	if (print_rec(m, rec->ip)) {
 		/* This should only happen when a rec is disabled */
 		WARN_ON_ONCE(!(rec->flags & FTRACE_FL_DISABLED));
@@ -3996,6 +3999,30 @@ ftrace_touched_open(struct inode *inode, struct file *file)
 	return 0;
 }
 
+static int
+ftrace_avail_addrs_open(struct inode *inode, struct file *file)
+{
+	struct ftrace_iterator *iter;
+	int ret;
+
+	ret = security_locked_down(LOCKDOWN_TRACEFS);
+	if (ret)
+		return ret;
+
+	if (unlikely(ftrace_disabled))
+		return -ENODEV;
+
+	iter = __seq_open_private(file, &show_ftrace_seq_ops, sizeof(*iter));
+	if (!iter)
+		return -ENOMEM;
+
+	iter->pg = ftrace_pages_start;
+	iter->flags = FTRACE_ITER_ADDRS;
+	iter->ops = &global_ops;
+
+	return 0;
+}
+
 /**
  * ftrace_regex_open - initialize function tracer filter files
  * @ops: The ftrace_ops that hold the hash filters
@@ -5916,6 +5943,13 @@ static const struct file_operations ftrace_touched_fops = {
 	.release = seq_release_private,
 };
 
+static const struct file_operations ftrace_avail_addrs_fops = {
+	.open = ftrace_avail_addrs_open,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.release = seq_release_private,
+};
+
 static const struct file_operations ftrace_filter_fops = {
 	.open = ftrace_filter_open,
 	.read = seq_read,
@@ -6377,6 +6411,9 @@ static __init int ftrace_init_dyn_tracefs(struct dentry *d_tracer)
 	trace_create_file("available_filter_functions", TRACE_MODE_READ,
 			d_tracer, NULL, &ftrace_avail_fops);
 
+	trace_create_file("available_filter_functions_addrs", TRACE_MODE_READ,
+			d_tracer, NULL, &ftrace_avail_addrs_fops);
+
 	trace_create_file("enabled_functions", TRACE_MODE_READ,
 			d_tracer, NULL, &ftrace_enabled_fops);
 
-- 
2.39.2

Re: [for-next][PATCH 08/13] ftrace: Show all functions with addresses in available_filter_functions_addrs

[Jackie Liu]

在 2023/6/22 00:29, Steven Rostedt 写道:
> From: Jiri Olsa <jolsa@kernel.org>
> 
> Adding new available_filter_functions_addrs file that shows all available
> functions (same as available_filter_functions) together with addresses,
> like:
> 
>    # cat available_filter_functions_addrs | head
>    ffffffff81000770 __traceiter_initcall_level
>    ffffffff810007c0 __traceiter_initcall_start
>    ffffffff81000810 __traceiter_initcall_finish
>    ffffffff81000860 trace_initcall_finish_cb
>    ...
> 
> Note displayed address is the patch-site address and can differ from
> /proc/kallsyms address.
> 
> It's useful to have address avilable for traceable symbols, so we don't
> need to allways cross check kallsyms with available_filter_functions
> (or the other way around) and have all the data in single file.
> 
> For backwards compatibility reasons we can't change the existing
> available_filter_functions file output, but we need to add new file.
> 
> The problem is that we need to do 2 passes:
> 
>   - through available_filter_functions and find out if the function is traceable
>   - through /proc/kallsyms to get the address for traceable function
> 
> Having available_filter_functions symbols together with addresses allow
> us to skip the kallsyms step and we are ok with the address in
> available_filter_functions_addr not being the function entry, because
> kprobe_multi uses fprobe and that handles both entry and patch-site
> address properly.
> 
> We have 2 interfaces how to create kprobe_multi link:
> 
>    a) passing symbols to kernel
> 
>       1) user gathers symbols and need to ensure that they are
>          trace-able -> pass through available_filter_functions file
> 
>       2) kernel takes those symbols and translates them to addresses
>          through kallsyms api
> 
>       3) addresses are passed to fprobe/ftrace through:
> 
>           register_fprobe_ips
>           -> ftrace_set_filter_ips
> 
>    b) passing addresses to kernel
> 
>       1) user gathers symbols and needs to ensure that they are
>          trace-able -> pass through available_filter_functions file
> 
>       2) user takes those symbols and translates them to addresses
>         through /proc/kallsyms
> 
>       3) addresses are passed to the kernel and kernel calls:
> 
>           register_fprobe_ips
>           -> ftrace_set_filter_ips
> 
> The new available_filter_functions_addrs file helps us with option b),
> because we can make 'b 1' and 'b 2' in one step - while filtering traceable
> functions, we get the address directly.
> 
> Link: https://lore.kernel.org/linux-trace-kernel/20230611130029.1202298-1-jolsa@kernel.org
> 
> Cc: Masami Hiramatsu <mhiramat@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
> Cc: Jackie Liu <liu.yun@linux.dev>
> Suggested-by: Steven Rostedt (Google) <rostedt@goodmis.org>
> Suggested-by: Andrii Nakryiko <andrii@kernel.org>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
> ---
>   Documentation/trace/ftrace.rst |  6 ++++++
>   include/linux/ftrace.h         |  1 +
>   kernel/trace/ftrace.c          | 37 ++++++++++++++++++++++++++++++++++
>   3 files changed, 44 insertions(+)
> 
> diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst
> index df2d3e57a83f..b7308ab10c0e 100644
> --- a/Documentation/trace/ftrace.rst
> +++ b/Documentation/trace/ftrace.rst
> @@ -324,6 +324,12 @@ of ftrace. Here is a list of some of the key files:
>   	"set_graph_function", or "set_graph_notrace".
>   	(See the section "dynamic ftrace" below for more details.)
>   
> +  available_filter_functions_addrs:
> +
> +	Similar to available_filter_functions, but with address displayed
> +	for each function. The displayed address is the patch-site address
> +	and can differ from /proc/kallsyms address.
> +
>     dyn_ftrace_total_info:
>   
>   	This file is for debugging purposes. The number of functions that
> diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> index 49f279f4c3a1..8e59bd954153 100644
> --- a/include/linux/ftrace.h
> +++ b/include/linux/ftrace.h
> @@ -633,6 +633,7 @@ enum {
>   	FTRACE_ITER_MOD		= (1 << 5),
>   	FTRACE_ITER_ENABLED	= (1 << 6),
>   	FTRACE_ITER_TOUCHED	= (1 << 7),
> +	FTRACE_ITER_ADDRS	= (1 << 8),
>   };
>   
>   void arch_ftrace_update_code(int command);
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 764668467155..b24c573934af 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -3861,6 +3861,9 @@ static int t_show(struct seq_file *m, void *v)
>   	if (!rec)
>   		return 0;
>   
> +	if (iter->flags & FTRACE_ITER_ADDRS)
> +		seq_printf(m, "%lx ", rec->ip);
> +
>   	if (print_rec(m, rec->ip)) {
>   		/* This should only happen when a rec is disabled */
>   		WARN_ON_ONCE(!(rec->flags & FTRACE_FL_DISABLED));
> @@ -3996,6 +3999,30 @@ ftrace_touched_open(struct inode *inode, struct file *file)
>   	return 0;
>   }
>   
> +static int
> +ftrace_avail_addrs_open(struct inode *inode, struct file *file)
> +{
> +	struct ftrace_iterator *iter;
> +	int ret;
> +
> +	ret = security_locked_down(LOCKDOWN_TRACEFS);
> +	if (ret)
> +		return ret;
> +
> +	if (unlikely(ftrace_disabled))
> +		return -ENODEV;
> +
> +	iter = __seq_open_private(file, &show_ftrace_seq_ops, sizeof(*iter));
> +	if (!iter)
> +		return -ENOMEM;
> +
> +	iter->pg = ftrace_pages_start;
> +	iter->flags = FTRACE_ITER_ADDRS;
> +	iter->ops = &global_ops;
> +
> +	return 0;
> +}
> +
>   /**
>    * ftrace_regex_open - initialize function tracer filter files
>    * @ops: The ftrace_ops that hold the hash filters
> @@ -5916,6 +5943,13 @@ static const struct file_operations ftrace_touched_fops = {
>   	.release = seq_release_private,
>   };
>   
> +static const struct file_operations ftrace_avail_addrs_fops = {
> +	.open = ftrace_avail_addrs_open,
> +	.read = seq_read,
> +	.llseek = seq_lseek,
> +	.release = seq_release_private,
> +};
> +
>   static const struct file_operations ftrace_filter_fops = {
>   	.open = ftrace_filter_open,
>   	.read = seq_read,
> @@ -6377,6 +6411,9 @@ static __init int ftrace_init_dyn_tracefs(struct dentry *d_tracer)
>   	trace_create_file("available_filter_functions", TRACE_MODE_READ,
>   			d_tracer, NULL, &ftrace_avail_fops);
>   
> +	trace_create_file("available_filter_functions_addrs", TRACE_MODE_READ,
> +			d_tracer, NULL, &ftrace_avail_addrs_fops);
> +

Tested-by: Jackie Liu <liuyun01@kylinos.cn> # x86

>   	trace_create_file("enabled_functions", TRACE_MODE_READ,
>   			d_tracer, NULL, &ftrace_enabled_fops);
>   

[for-next][PATCH 09/13] tracing/osnoise: Switch from PF_NO_SETAFFINITY to migrate_disable

[Steven Rostedt]

From: Daniel Bristot de Oliveira <bristot@kernel.org>

Currently, osnoise/timerlat threads run with PF_NO_SETAFFINITY set.
It works well, however, cgroups do not allow PF_NO_SETAFFINITY threads
to be accepted, and this creates a limitation to osnoise/timerlat.

To avoid this limitation, disable migration of the threads as soon
as they start to run, and then clean the PF_NO_SETAFFINITY flag (still)
used during thread creation.

If for some reason a thread migration is requested, e.g., via
sched_settafinity, the tracer thread will notice and exit.

Link: https://lkml.kernel.org/r/8ba8bc9c15b3ea40cf73cf67a9bc061a264609f0.1686063934.git.bristot@kernel.org

Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: William White <chwhite@redhat.com>
Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 kernel/trace/trace_osnoise.c | 68 ++++++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)

diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
index e97e3fa5cbed..c265ec5f1726 100644
--- a/kernel/trace/trace_osnoise.c
+++ b/kernel/trace/trace_osnoise.c
@@ -1545,6 +1545,39 @@ static void osnoise_sleep(void)
 	}
 }
 
+/*
+ * osnoise_migration_pending - checks if the task needs to migrate
+ *
+ * osnoise/timerlat threads are per-cpu. If there is a pending request to
+ * migrate the thread away from the current CPU, something bad has happened.
+ * Play the good citizen and leave.
+ *
+ * Returns 0 if it is safe to continue, 1 otherwise.
+ */
+static inline int osnoise_migration_pending(void)
+{
+	if (!current->migration_pending)
+		return 0;
+
+	/*
+	 * If migration is pending, there is a task waiting for the
+	 * tracer to enable migration. The tracer does not allow migration,
+	 * thus: taint and leave to unblock the blocked thread.
+	 */
+	osnoise_taint("migration requested to osnoise threads, leaving.");
+
+	/*
+	 * Unset this thread from the threads managed by the interface.
+	 * The tracers are responsible for cleaning their env before
+	 * exiting.
+	 */
+	mutex_lock(&interface_lock);
+	this_cpu_osn_var()->kthread = NULL;
+	mutex_unlock(&interface_lock);
+
+	return 1;
+}
+
 /*
  * osnoise_main - The osnoise detection kernel thread
  *
@@ -1553,12 +1586,29 @@ static void osnoise_sleep(void)
  */
 static int osnoise_main(void *data)
 {
+	unsigned long flags;
+
+	/*
+	 * This thread was created pinned to the CPU using PF_NO_SETAFFINITY.
+	 * The problem is that cgroup does not allow PF_NO_SETAFFINITY thread.
+	 *
+	 * To work around this limitation, disable migration and remove the
+	 * flag.
+	 */
+	migrate_disable();
+	raw_spin_lock_irqsave(&current->pi_lock, flags);
+	current->flags &= ~(PF_NO_SETAFFINITY);
+	raw_spin_unlock_irqrestore(&current->pi_lock, flags);
 
 	while (!kthread_should_stop()) {
+		if (osnoise_migration_pending())
+			break;
+
 		run_osnoise();
 		osnoise_sleep();
 	}
 
+	migrate_enable();
 	return 0;
 }
 
@@ -1706,6 +1756,7 @@ static int timerlat_main(void *data)
 	struct timerlat_variables *tlat = this_cpu_tmr_var();
 	struct timerlat_sample s;
 	struct sched_param sp;
+	unsigned long flags;
 	u64 now, diff;
 
 	/*
@@ -1714,6 +1765,18 @@ static int timerlat_main(void *data)
 	sp.sched_priority = DEFAULT_TIMERLAT_PRIO;
 	sched_setscheduler_nocheck(current, SCHED_FIFO, &sp);
 
+	/*
+	 * This thread was created pinned to the CPU using PF_NO_SETAFFINITY.
+	 * The problem is that cgroup does not allow PF_NO_SETAFFINITY thread.
+	 *
+	 * To work around this limitation, disable migration and remove the
+	 * flag.
+	 */
+	migrate_disable();
+	raw_spin_lock_irqsave(&current->pi_lock, flags);
+	current->flags &= ~(PF_NO_SETAFFINITY);
+	raw_spin_unlock_irqrestore(&current->pi_lock, flags);
+
 	tlat->count = 0;
 	tlat->tracing_thread = false;
 
@@ -1731,6 +1794,7 @@ static int timerlat_main(void *data)
 	osn_var->sampling = 1;
 
 	while (!kthread_should_stop()) {
+
 		now = ktime_to_ns(hrtimer_cb_get_time(&tlat->timer));
 		diff = now - tlat->abs_period;
 
@@ -1749,10 +1813,14 @@ static int timerlat_main(void *data)
 			if (time_to_us(diff) >= osnoise_data.stop_tracing_total)
 				osnoise_stop_tracing();
 
+		if (osnoise_migration_pending())
+			break;
+
 		wait_next_period(tlat);
 	}
 
 	hrtimer_cancel(&tlat->timer);
+	migrate_enable();
 	return 0;
 }
 #else /* CONFIG_TIMERLAT_TRACER */
-- 
2.39.2

[for-next][PATCH 10/13] tracing/osnoise: Skip running osnoise if all instances are off

[Steven Rostedt]

From: Daniel Bristot de Oliveira <bristot@kernel.org>

In the case of all tracing instances being off, sleep for the entire
period.

 Q: Why not kill all threads so?
 A: It is valid and useful to start the threads with tracing off.
For example, rtla disables tracing, starts the tracer, applies the
scheduling setup to the threads, e.g., sched priority and cgroup,
and then begin tracing with all set.

Skipping the period helps to speed up rtla setup and save the
trace after a stop tracing.

Link: https://lkml.kernel.org/r/aa4dd9b7e76fcb63901fe5407e15ec002b318599.1686063934.git.bristot@kernel.org

Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: William White <chwhite@redhat.com>
Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 kernel/trace/trace_osnoise.c | 31 ++++++++++++++++++++++++++++---
 1 file changed, 28 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
index c265ec5f1726..220172cb874d 100644
--- a/kernel/trace/trace_osnoise.c
+++ b/kernel/trace/trace_osnoise.c
@@ -1285,6 +1285,22 @@ static __always_inline void osnoise_stop_tracing(void)
 	rcu_read_unlock();
 }
 
+/*
+ * osnoise_has_tracing_on - Check if there is at least one instance on
+ */
+static __always_inline int osnoise_has_tracing_on(void)
+{
+	struct osnoise_instance *inst;
+	int trace_is_on = 0;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(inst, &osnoise_instances, list)
+		trace_is_on += tracer_tracing_is_on(inst->tr);
+	rcu_read_unlock();
+
+	return trace_is_on;
+}
+
 /*
  * notify_new_max_latency - Notify a new max latency via fsnotify interface.
  */
@@ -1517,13 +1533,16 @@ static struct cpumask save_cpumask;
 /*
  * osnoise_sleep - sleep until the next period
  */
-static void osnoise_sleep(void)
+static void osnoise_sleep(bool skip_period)
 {
 	u64 interval;
 	ktime_t wake_time;
 
 	mutex_lock(&interface_lock);
-	interval = osnoise_data.sample_period - osnoise_data.sample_runtime;
+	if (skip_period)
+		interval = osnoise_data.sample_period;
+	else
+		interval = osnoise_data.sample_period - osnoise_data.sample_runtime;
 	mutex_unlock(&interface_lock);
 
 	/*
@@ -1604,8 +1623,14 @@ static int osnoise_main(void *data)
 		if (osnoise_migration_pending())
 			break;
 
+		/* skip a period if tracing is off on all instances */
+		if (!osnoise_has_tracing_on()) {
+			osnoise_sleep(true);
+			continue;
+		}
+
 		run_osnoise();
-		osnoise_sleep();
+		osnoise_sleep(false);
 	}
 
 	migrate_enable();
-- 
2.39.2

[for-next][PATCH 11/13] tracing/timerlat: Add user-space interface

[Steven Rostedt]

From: Daniel Bristot de Oliveira <bristot@kernel.org>

Going a step further, we propose a way to use any user-space
workload as the task waiting for the timerlat timer. This is done
via a per-CPU file named osnoise/cpu$id/timerlat_fd file.

The tracef_fd allows a task to open at a time. When a task reads
the file, the timerlat timer is armed for future osnoise/timerlat_period_us
time. When the timer fires, it prints the IRQ latency and
wakes up the user-space thread waiting in the timerlat_fd.

The thread then starts to run, executes the timerlat measurement, prints
the thread scheduling latency and returns to user-space.

When the thread rereads the timerlat_fd, the tracer will print the
user-ret(urn) latency, which is an additional metric.

This additional metric is also traced by the tracer and can be used, for
example of measuring the context switch overhead from kernel-to-user and
user-to-kernel, or the response time for an arbitrary execution in
user-space.

The tracer supports one thread per CPU, the thread must be pinned to
the CPU, and it cannot migrate while holding the timerlat_fd. The reason
is that the tracer is per CPU (nothing prohibits the tracer from
allowing migrations in the future). The tracer monitors the migration
of the thread and disables the tracer if detected.

The timerlat_fd is only available for opening/reading when timerlat
tracer is enabled, and NO_OSNOISE_WORKLOAD is set.

The simplest way to activate this feature from user-space is:

 -------------------------------- %< -----------------------------------
 int main(void)
 {
	char buffer[1024];
	int timerlat_fd;
	int retval;
	long cpu = 0;	/* place in CPU 0 */
	cpu_set_t set;

	CPU_ZERO(&set);
	CPU_SET(cpu, &set);

	if (sched_setaffinity(gettid(), sizeof(set), &set) == -1)
		return 1;

	snprintf(buffer, sizeof(buffer),
		"/sys/kernel/tracing/osnoise/per_cpu/cpu%ld/timerlat_fd",
		cpu);

	timerlat_fd = open(buffer, O_RDONLY);
	if (timerlat_fd < 0) {
		printf("error opening %s: %s\n", buffer, strerror(errno));
		exit(1);
	}

	for (;;) {
		retval = read(timerlat_fd, buffer, 1024);
		if (retval < 0)
			break;
	}

	close(timerlat_fd);
	exit(0);
}
 -------------------------------- >% -----------------------------------

When disabling timerlat, if there is a workload holding the timerlat_fd,
the SIGKILL will be sent to the thread.

Link: https://lkml.kernel.org/r/69fe66a863d2792ff4c3a149bf9e32e26468bb3a.1686063934.git.bristot@kernel.org

Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: William White <chwhite@redhat.com>
Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 Documentation/trace/timerlat-tracer.rst |  78 +++++
 kernel/trace/trace_osnoise.c            | 378 +++++++++++++++++++++++-
 kernel/trace/trace_output.c             |   4 +-
 3 files changed, 455 insertions(+), 5 deletions(-)

diff --git a/Documentation/trace/timerlat-tracer.rst b/Documentation/trace/timerlat-tracer.rst
index db17df312bc8..53a56823e903 100644
--- a/Documentation/trace/timerlat-tracer.rst
+++ b/Documentation/trace/timerlat-tracer.rst
@@ -180,3 +180,81 @@ dummy_load_1ms_pd_init, which had the following code (on purpose)::
 		return 0;
 
 	}
+
+User-space interface
+---------------------------
+
+Timerlat allows user-space threads to use timerlat infra-structure to
+measure scheduling latency. This interface is accessible via a per-CPU
+file descriptor inside $tracing_dir/osnoise/per_cpu/cpu$ID/timerlat_fd.
+
+This interface is accessible under the following conditions:
+
+ - timerlat tracer is enable
+ - osnoise workload option is set to NO_OSNOISE_WORKLOAD
+ - The user-space thread is affined to a single processor
+ - The thread opens the file associated with its single processor
+ - Only one thread can access the file at a time
+
+The open() syscall will fail if any of these conditions are not met.
+After opening the file descriptor, the user space can read from it.
+
+The read() system call will run a timerlat code that will arm the
+timer in the future and wait for it as the regular kernel thread does.
+
+When the timer IRQ fires, the timerlat IRQ will execute, report the
+IRQ latency and wake up the thread waiting in the read. The thread will be
+scheduled and report the thread latency via tracer - as for the kernel
+thread.
+
+The difference from the in-kernel timerlat is that, instead of re-arming
+the timer, timerlat will return to the read() system call. At this point,
+the user can run any code.
+
+If the application rereads the file timerlat file descriptor, the tracer
+will report the return from user-space latency, which is the total
+latency. If this is the end of the work, it can be interpreted as the
+response time for the request.
+
+After reporting the total latency, timerlat will restart the cycle, arm
+a timer, and go to sleep for the following activation.
+
+If at any time one of the conditions is broken, e.g., the thread migrates
+while in user space, or the timerlat tracer is disabled, the SIG_KILL
+signal will be sent to the user-space thread.
+
+Here is an basic example of user-space code for timerlat::
+
+ int main(void)
+ {
+	char buffer[1024];
+	int timerlat_fd;
+	int retval;
+	long cpu = 0;   /* place in CPU 0 */
+	cpu_set_t set;
+
+	CPU_ZERO(&set);
+	CPU_SET(cpu, &set);
+
+	if (sched_setaffinity(gettid(), sizeof(set), &set) == -1)
+		return 1;
+
+	snprintf(buffer, sizeof(buffer),
+		"/sys/kernel/tracing/osnoise/per_cpu/cpu%ld/timerlat_fd",
+		cpu);
+
+	timerlat_fd = open(buffer, O_RDONLY);
+	if (timerlat_fd < 0) {
+		printf("error opening %s: %s\n", buffer, strerror(errno));
+		exit(1);
+	}
+
+	for (;;) {
+		retval = read(timerlat_fd, buffer, 1024);
+		if (retval < 0)
+			break;
+	}
+
+	close(timerlat_fd);
+	exit(0);
+ }
diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
index 220172cb874d..bd0d01d00fb9 100644
--- a/kernel/trace/trace_osnoise.c
+++ b/kernel/trace/trace_osnoise.c
@@ -181,6 +181,7 @@ struct osn_irq {
 
 #define IRQ_CONTEXT	0
 #define THREAD_CONTEXT	1
+#define THREAD_URET	2
 /*
  * sofirq runtime info.
  */
@@ -238,6 +239,7 @@ struct timerlat_variables {
 	u64			abs_period;
 	bool			tracing_thread;
 	u64			count;
+	bool			uthread_migrate;
 };
 
 static DEFINE_PER_CPU(struct timerlat_variables, per_cpu_timerlat_var);
@@ -1181,6 +1183,78 @@ thread_exit(struct osnoise_variables *osn_var, struct task_struct *t)
 	osn_var->thread.arrival_time = 0;
 }
 
+#ifdef CONFIG_TIMERLAT_TRACER
+/*
+ * osnoise_stop_exception - Stop tracing and the tracer.
+ */
+static __always_inline void osnoise_stop_exception(char *msg, int cpu)
+{
+	struct osnoise_instance *inst;
+	struct trace_array *tr;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(inst, &osnoise_instances, list) {
+		tr = inst->tr;
+		trace_array_printk_buf(tr->array_buffer.buffer, _THIS_IP_,
+				       "stop tracing hit on cpu %d due to exception: %s\n",
+				       smp_processor_id(),
+				       msg);
+
+		if (test_bit(OSN_PANIC_ON_STOP, &osnoise_options))
+			panic("tracer hit on cpu %d due to exception: %s\n",
+			      smp_processor_id(),
+			      msg);
+
+		tracer_tracing_off(tr);
+	}
+	rcu_read_unlock();
+}
+
+/*
+ * trace_sched_migrate_callback - sched:sched_migrate_task trace event handler
+ *
+ * his function is hooked to the sched:sched_migrate_task trace event, and monitors
+ * timerlat user-space thread migration.
+ */
+static void trace_sched_migrate_callback(void *data, struct task_struct *p, int dest_cpu)
+{
+	struct osnoise_variables *osn_var;
+	long cpu = task_cpu(p);
+
+	osn_var = per_cpu_ptr(&per_cpu_osnoise_var, cpu);
+	if (osn_var->pid == p->pid && dest_cpu != cpu) {
+		per_cpu_ptr(&per_cpu_timerlat_var, cpu)->uthread_migrate = 1;
+		osnoise_taint("timerlat user-thread migrated\n");
+		osnoise_stop_exception("timerlat user-thread migrated", cpu);
+	}
+}
+
+static int register_migration_monitor(void)
+{
+	int ret = 0;
+
+	/*
+	 * Timerlat thread migration check is only required when running timerlat in user-space.
+	 * Thus, enable callback only if timerlat is set with no workload.
+	 */
+	if (timerlat_enabled() && !test_bit(OSN_WORKLOAD, &osnoise_options))
+		ret = register_trace_sched_migrate_task(trace_sched_migrate_callback, NULL);
+
+	return ret;
+}
+
+static void unregister_migration_monitor(void)
+{
+	if (timerlat_enabled() && !test_bit(OSN_WORKLOAD, &osnoise_options))
+		unregister_trace_sched_migrate_task(trace_sched_migrate_callback, NULL);
+}
+#else
+static int register_migration_monitor(void)
+{
+	return 0;
+}
+static void unregister_migration_monitor(void) {}
+#endif
 /*
  * trace_sched_switch - sched:sched_switch trace event handler
  *
@@ -1204,7 +1278,7 @@ trace_sched_switch_callback(void *data, bool preempt,
 }
 
 /*
- * hook_thread_events - Hook the insturmentation for thread noise
+ * hook_thread_events - Hook the instrumentation for thread noise
  *
  * Hook the osnoise tracer callbacks to handle the noise from other
  * threads on the necessary kernel events.
@@ -1217,11 +1291,19 @@ static int hook_thread_events(void)
 	if (ret)
 		return -EINVAL;
 
+	ret = register_migration_monitor();
+	if (ret)
+		goto out_unreg;
+
 	return 0;
+
+out_unreg:
+	unregister_trace_sched_switch(trace_sched_switch_callback, NULL);
+	return -EINVAL;
 }
 
 /*
- * unhook_thread_events - *nhook the insturmentation for thread noise
+ * unhook_thread_events - unhook the instrumentation for thread noise
  *
  * Unook the osnoise tracer callbacks to handle the noise from other
  * threads on the necessary kernel events.
@@ -1229,6 +1311,7 @@ static int hook_thread_events(void)
 static void unhook_thread_events(void)
 {
 	unregister_trace_sched_switch(trace_sched_switch_callback, NULL);
+	unregister_migration_monitor();
 }
 
 /*
@@ -1864,10 +1947,24 @@ static void stop_kthread(unsigned int cpu)
 
 	kthread = per_cpu(per_cpu_osnoise_var, cpu).kthread;
 	if (kthread) {
-		kthread_stop(kthread);
+		if (test_bit(OSN_WORKLOAD, &osnoise_options)) {
+			kthread_stop(kthread);
+		} else {
+			/*
+			 * This is a user thread waiting on the timerlat_fd. We need
+			 * to close all users, and the best way to guarantee this is
+			 * by killing the thread. NOTE: this is a purpose specific file.
+			 */
+			kill_pid(kthread->thread_pid, SIGKILL, 1);
+			put_task_struct(kthread);
+		}
 		per_cpu(per_cpu_osnoise_var, cpu).kthread = NULL;
 	} else {
+		/* if no workload, just return */
 		if (!test_bit(OSN_WORKLOAD, &osnoise_options)) {
+			/*
+			 * This is set in the osnoise tracer case.
+			 */
 			per_cpu(per_cpu_osnoise_var, cpu).sampling = false;
 			barrier();
 			return;
@@ -1912,7 +2009,6 @@ static int start_kthread(unsigned int cpu)
 			barrier();
 			return 0;
 		}
-
 		snprintf(comm, 24, "osnoise/%d", cpu);
 	}
 
@@ -1941,6 +2037,11 @@ static int start_per_cpu_kthreads(void)
 	int retval = 0;
 	int cpu;
 
+	if (!test_bit(OSN_WORKLOAD, &osnoise_options)) {
+		if (timerlat_enabled())
+			return 0;
+	}
+
 	cpus_read_lock();
 	/*
 	 * Run only on online CPUs in which osnoise is allowed to run.
@@ -2281,6 +2382,223 @@ osnoise_cpus_write(struct file *filp, const char __user *ubuf, size_t count,
 	return err;
 }
 
+#ifdef CONFIG_TIMERLAT_TRACER
+static int timerlat_fd_open(struct inode *inode, struct file *file)
+{
+	struct osnoise_variables *osn_var;
+	struct timerlat_variables *tlat;
+	long cpu = (long) inode->i_cdev;
+
+	mutex_lock(&interface_lock);
+
+	/*
+	 * This file is accessible only if timerlat is enabled, and
+	 * NO_OSNOISE_WORKLOAD is set.
+	 */
+	if (!timerlat_enabled() || test_bit(OSN_WORKLOAD, &osnoise_options)) {
+		mutex_unlock(&interface_lock);
+		return -EINVAL;
+	}
+
+	migrate_disable();
+
+	osn_var = this_cpu_osn_var();
+
+	/*
+	 * The osn_var->pid holds the single access to this file.
+	 */
+	if (osn_var->pid) {
+		mutex_unlock(&interface_lock);
+		migrate_enable();
+		return -EBUSY;
+	}
+
+	/*
+	 * timerlat tracer is a per-cpu tracer. Check if the user-space too
+	 * is pinned to a single CPU. The tracer laters monitor if the task
+	 * migrates and then disables tracer if it does. However, it is
+	 * worth doing this basic acceptance test to avoid obviusly wrong
+	 * setup.
+	 */
+	if (current->nr_cpus_allowed > 1 ||  cpu != smp_processor_id()) {
+		mutex_unlock(&interface_lock);
+		migrate_enable();
+		return -EPERM;
+	}
+
+	/*
+	 * From now on, it is good to go.
+	 */
+	file->private_data = inode->i_cdev;
+
+	get_task_struct(current);
+
+	osn_var->kthread = current;
+	osn_var->pid = current->pid;
+
+	/*
+	 * Setup is done.
+	 */
+	mutex_unlock(&interface_lock);
+
+	tlat = this_cpu_tmr_var();
+	tlat->count = 0;
+
+	migrate_enable();
+	return 0;
+};
+
+/*
+ * timerlat_fd_read - Read function for "timerlat_fd" file
+ * @file: The active open file structure
+ * @ubuf: The userspace provided buffer to read value into
+ * @cnt: The maximum number of bytes to read
+ * @ppos: The current "file" position
+ *
+ * Prints 1 on timerlat, the number of interferences on osnoise, -1 on error.
+ */
+static ssize_t
+timerlat_fd_read(struct file *file, char __user *ubuf, size_t count,
+		  loff_t *ppos)
+{
+	long cpu = (long) file->private_data;
+	struct osnoise_variables *osn_var;
+	struct timerlat_variables *tlat;
+	struct timerlat_sample s;
+	s64 diff;
+	u64 now;
+
+	migrate_disable();
+
+	tlat = this_cpu_tmr_var();
+
+	/*
+	 * While in user-space, the thread is migratable. There is nothing
+	 * we can do about it.
+	 * So, if the thread is running on another CPU, stop the machinery.
+	 */
+	if (cpu == smp_processor_id()) {
+		if (tlat->uthread_migrate) {
+			migrate_enable();
+			return -EINVAL;
+		}
+	} else {
+		per_cpu_ptr(&per_cpu_timerlat_var, cpu)->uthread_migrate = 1;
+		osnoise_taint("timerlat user thread migrate\n");
+		osnoise_stop_tracing();
+		migrate_enable();
+		return -EINVAL;
+	}
+
+	osn_var = this_cpu_osn_var();
+
+	/*
+	 * The timerlat in user-space runs in a different order:
+	 * the read() starts from the execution of the previous occurrence,
+	 * sleeping for the next occurrence.
+	 *
+	 * So, skip if we are entering on read() before the first wakeup
+	 * from timerlat IRQ:
+	 */
+	if (likely(osn_var->sampling)) {
+		now = ktime_to_ns(hrtimer_cb_get_time(&tlat->timer));
+		diff = now - tlat->abs_period;
+
+		/*
+		 * it was not a timer firing, but some other signal?
+		 */
+		if (diff < 0)
+			goto out;
+
+		s.seqnum = tlat->count;
+		s.timer_latency = diff;
+		s.context = THREAD_URET;
+
+		trace_timerlat_sample(&s);
+
+		notify_new_max_latency(diff);
+
+		tlat->tracing_thread = false;
+		if (osnoise_data.stop_tracing_total)
+			if (time_to_us(diff) >= osnoise_data.stop_tracing_total)
+				osnoise_stop_tracing();
+	} else {
+		tlat->tracing_thread = false;
+		tlat->kthread = current;
+
+		hrtimer_init(&tlat->timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED_HARD);
+		tlat->timer.function = timerlat_irq;
+
+		/* Annotate now to drift new period */
+		tlat->abs_period = hrtimer_cb_get_time(&tlat->timer);
+
+		osn_var->sampling = 1;
+	}
+
+	/* wait for the next period */
+	wait_next_period(tlat);
+
+	/* This is the wakeup from this cycle */
+	now = ktime_to_ns(hrtimer_cb_get_time(&tlat->timer));
+	diff = now - tlat->abs_period;
+
+	/*
+	 * it was not a timer firing, but some other signal?
+	 */
+	if (diff < 0)
+		goto out;
+
+	s.seqnum = tlat->count;
+	s.timer_latency = diff;
+	s.context = THREAD_CONTEXT;
+
+	trace_timerlat_sample(&s);
+
+	if (osnoise_data.stop_tracing_total) {
+		if (time_to_us(diff) >= osnoise_data.stop_tracing_total) {
+			timerlat_dump_stack(time_to_us(diff));
+			notify_new_max_latency(diff);
+			osnoise_stop_tracing();
+		}
+	}
+
+out:
+	migrate_enable();
+	return 0;
+}
+
+static int timerlat_fd_release(struct inode *inode, struct file *file)
+{
+	struct osnoise_variables *osn_var;
+	struct timerlat_variables *tlat_var;
+	long cpu = (long) file->private_data;
+
+	migrate_disable();
+	mutex_lock(&interface_lock);
+
+	osn_var = per_cpu_ptr(&per_cpu_osnoise_var, cpu);
+	tlat_var = per_cpu_ptr(&per_cpu_timerlat_var, cpu);
+
+	hrtimer_cancel(&tlat_var->timer);
+	memset(tlat_var, 0, sizeof(*tlat_var));
+
+	osn_var->sampling = 0;
+	osn_var->pid = 0;
+
+	/*
+	 * We are leaving, not being stopped... see stop_kthread();
+	 */
+	if (osn_var->kthread) {
+		put_task_struct(osn_var->kthread);
+		osn_var->kthread = NULL;
+	}
+
+	mutex_unlock(&interface_lock);
+	migrate_enable();
+	return 0;
+}
+#endif
+
 /*
  * osnoise/runtime_us: cannot be greater than the period.
  */
@@ -2344,6 +2662,13 @@ static struct trace_min_max_param timerlat_period = {
 	.max	= &timerlat_max_period,
 	.min	= &timerlat_min_period,
 };
+
+static const struct file_operations timerlat_fd_fops = {
+	.open		= timerlat_fd_open,
+	.read		= timerlat_fd_read,
+	.release	= timerlat_fd_release,
+	.llseek		= generic_file_llseek,
+};
 #endif
 
 static const struct file_operations cpus_fops = {
@@ -2381,18 +2706,63 @@ static int init_timerlat_stack_tracefs(struct dentry *top_dir)
 }
 #endif /* CONFIG_STACKTRACE */
 
+static int osnoise_create_cpu_timerlat_fd(struct dentry *top_dir)
+{
+	struct dentry *timerlat_fd;
+	struct dentry *per_cpu;
+	struct dentry *cpu_dir;
+	char cpu_str[30]; /* see trace.c: tracing_init_tracefs_percpu() */
+	long cpu;
+
+	/*
+	 * Why not using tracing instance per_cpu/ dir?
+	 *
+	 * Because osnoise/timerlat have a single workload, having
+	 * multiple files like these are wast of memory.
+	 */
+	per_cpu = tracefs_create_dir("per_cpu", top_dir);
+	if (!per_cpu)
+		return -ENOMEM;
+
+	for_each_possible_cpu(cpu) {
+		snprintf(cpu_str, 30, "cpu%ld", cpu);
+		cpu_dir = tracefs_create_dir(cpu_str, per_cpu);
+		if (!cpu_dir)
+			goto out_clean;
+
+		timerlat_fd = trace_create_file("timerlat_fd", TRACE_MODE_READ,
+						cpu_dir, NULL, &timerlat_fd_fops);
+		if (!timerlat_fd)
+			goto out_clean;
+
+		/* Record the CPU */
+		d_inode(timerlat_fd)->i_cdev = (void *)(cpu);
+	}
+
+	return 0;
+
+out_clean:
+	tracefs_remove(per_cpu);
+	return -ENOMEM;
+}
+
 /*
  * init_timerlat_tracefs - A function to initialize the timerlat interface files
  */
 static int init_timerlat_tracefs(struct dentry *top_dir)
 {
 	struct dentry *tmp;
+	int retval;
 
 	tmp = tracefs_create_file("timerlat_period_us", TRACE_MODE_WRITE, top_dir,
 				  &timerlat_period, &trace_min_max_fops);
 	if (!tmp)
 		return -ENOMEM;
 
+	retval = osnoise_create_cpu_timerlat_fd(top_dir);
+	if (retval)
+		return retval;
+
 	return init_timerlat_stack_tracefs(top_dir);
 }
 #else /* CONFIG_TIMERLAT_TRACER */
diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 15f05faaae44..9f10c0071c4f 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -1446,6 +1446,8 @@ static struct trace_event trace_osnoise_event = {
 };
 
 /* TRACE_TIMERLAT */
+
+static char *timerlat_lat_context[] = {"irq", "thread", "user-ret"};
 static enum print_line_t
 trace_timerlat_print(struct trace_iterator *iter, int flags,
 		     struct trace_event *event)
@@ -1458,7 +1460,7 @@ trace_timerlat_print(struct trace_iterator *iter, int flags,
 
 	trace_seq_printf(s, "#%-5u context %6s timer_latency %9llu ns\n",
 			 field->seqnum,
-			 field->context ? "thread" : "irq",
+			 timerlat_lat_context[field->context],
 			 field->timer_latency);
 
 	return trace_handle_return(s);
-- 
2.39.2

[for-next][PATCH 12/13] tracing/boot: Replace strlcpy with strscpy

[Steven Rostedt]

From: Azeem Shaikh <azeemshaikh38@gmail.com>

strlcpy() reads the entire source buffer first.
This read may exceed the destination size limit.
This is both inefficient and can lead to linear read
overflows if a source string is not NUL-terminated [1].
In an effort to remove strlcpy() completely [2], replace
strlcpy() here with strscpy().

Direct replacement is safe here since return value of -E2BIG
is used to check for truncation instead of sizeof(dest).

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
[2] https://github.com/KSPP/linux/issues/89

Link: https://lore.kernel.org/linux-trace-kernel/20230613004125.3539934-1-azeemshaikh38@gmail.com

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 kernel/trace/trace_boot.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c
index 778200dd8ede..5fe525f1b8cc 100644
--- a/kernel/trace/trace_boot.c
+++ b/kernel/trace/trace_boot.c
@@ -31,7 +31,7 @@ trace_boot_set_instance_options(struct trace_array *tr, struct xbc_node *node)
 
 	/* Common ftrace options */
 	xbc_node_for_each_array_value(node, "options", anode, p) {
-		if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf)) {
+		if (strscpy(buf, p, ARRAY_SIZE(buf)) == -E2BIG) {
 			pr_err("String is too long: %s\n", p);
 			continue;
 		}
@@ -87,7 +87,7 @@ trace_boot_enable_events(struct trace_array *tr, struct xbc_node *node)
 	const char *p;
 
 	xbc_node_for_each_array_value(node, "events", anode, p) {
-		if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf)) {
+		if (strscpy(buf, p, ARRAY_SIZE(buf)) == -E2BIG) {
 			pr_err("String is too long: %s\n", p);
 			continue;
 		}
@@ -486,7 +486,7 @@ trace_boot_init_one_event(struct trace_array *tr, struct xbc_node *gnode,
 
 	p = xbc_node_find_value(enode, "filter", NULL);
 	if (p && *p != '\0') {
-		if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf))
+		if (strscpy(buf, p, ARRAY_SIZE(buf)) == -E2BIG)
 			pr_err("filter string is too long: %s\n", p);
 		else if (apply_event_filter(file, buf) < 0)
 			pr_err("Failed to apply filter: %s\n", buf);
@@ -494,7 +494,7 @@ trace_boot_init_one_event(struct trace_array *tr, struct xbc_node *gnode,
 
 	if (IS_ENABLED(CONFIG_HIST_TRIGGERS)) {
 		xbc_node_for_each_array_value(enode, "actions", anode, p) {
-			if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf))
+			if (strscpy(buf, p, ARRAY_SIZE(buf)) == -E2BIG)
 				pr_err("action string is too long: %s\n", p);
 			else if (trigger_process_regex(file, buf) < 0)
 				pr_err("Failed to apply an action: %s\n", p);
-- 
2.39.2

[for-next][PATCH 13/13] riscv: ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL

[Steven Rostedt]

From: Donglin Peng <pengdonglin@sangfor.com.cn>

The previous patch ("function_graph: Support recording and printing
the return value of function") has laid the groundwork for the for
the funcgraph-retval, and this modification makes it available on
the RISC-V platform.

We introduce a new structure called fgraph_ret_regs for the RISC-V
platform to hold return registers and the frame pointer. We then
fill its content in the return_to_handler and pass its address to
the function ftrace_return_to_handler to record the return value.

Link: https://lore.kernel.org/linux-trace-kernel/a8d71b12259f90e7e63d0ea654fcac95b0232bbc.1680954589.git.pengdonglin@sangfor.com.cn

Signed-off-by: Donglin Peng <pengdonglin@sangfor.com.cn>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 arch/riscv/Kconfig              |  1 +
 arch/riscv/include/asm/ftrace.h | 21 +++++++++++++++++++++
 arch/riscv/kernel/mcount.S      |  7 +------
 3 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 2bb0c38419ff..62c1e375183c 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -146,6 +146,7 @@ config RISCV
 	select HAVE_DYNAMIC_FTRACE_WITH_REGS if HAVE_DYNAMIC_FTRACE
 	select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL
 	select HAVE_FUNCTION_GRAPH_TRACER
+	select HAVE_FUNCTION_GRAPH_RETVAL if HAVE_FUNCTION_GRAPH_TRACER
 	select HAVE_FUNCTION_TRACER if !XIP_KERNEL && !PREEMPTION
 
 config CLANG_SUPPORTS_DYNAMIC_FTRACE
diff --git a/arch/riscv/include/asm/ftrace.h b/arch/riscv/include/asm/ftrace.h
index d47d87c2d7e3..740a979171e5 100644
--- a/arch/riscv/include/asm/ftrace.h
+++ b/arch/riscv/include/asm/ftrace.h
@@ -111,4 +111,25 @@ int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec);
 
 #endif /* CONFIG_DYNAMIC_FTRACE */
 
+#ifndef __ASSEMBLY__
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+struct fgraph_ret_regs {
+	unsigned long a1;
+	unsigned long a0;
+	unsigned long s0;
+	unsigned long ra;
+};
+
+static inline unsigned long fgraph_ret_regs_return_value(struct fgraph_ret_regs *ret_regs)
+{
+	return ret_regs->a0;
+}
+
+static inline unsigned long fgraph_ret_regs_frame_pointer(struct fgraph_ret_regs *ret_regs)
+{
+	return ret_regs->s0;
+}
+#endif /* ifdef CONFIG_FUNCTION_GRAPH_TRACER */
+#endif
+
 #endif /* _ASM_RISCV_FTRACE_H */
diff --git a/arch/riscv/kernel/mcount.S b/arch/riscv/kernel/mcount.S
index 30102aadc4d7..8a6e5a9e842a 100644
--- a/arch/riscv/kernel/mcount.S
+++ b/arch/riscv/kernel/mcount.S
@@ -65,13 +65,8 @@ ENTRY(return_to_handler)
  * So alternatively we check the *old* frame pointer position, that is, the
  * value stored in -16(s0) on entry, and the s0 on return.
  */
-#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
-	mv	t6, s0
-#endif
 	SAVE_RET_ABI_STATE
-#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
-	mv	a0, t6
-#endif
+	mv	a0, sp
 	call	ftrace_return_to_handler
 	mv	a2, a0
 	RESTORE_RET_ABI_STATE
-- 
2.39.2

Re: [for-next][PATCH 01/13] fgraph: Add declaration of "struct fgraph_ret_regs"

[Steven Rostedt]

Sending manually, as quilt mail didn't acknowledge some character in this
email, and it was rejected by lkml as wrong mime type.

-- Steve

On Wed, 21 Jun 2023 12:29:24 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> From: "Steven Rostedt (Google)" <rostedt@goodmis.org>
> 
> In final testing of:
> 
>   https://patchwork.kernel.org/project/linux-trace-kernel/patch/1fc502712c981e0e6742185ba242992170ac9da8.1680954589.git.pengdonglin@sangfor.com.cn/
>   "function_graph: Support recording and printing the return value of function"
> 
> The test failed due to a new warning found in the build:
> 
> kernel/trace/fgraph.c:243:56: warning: ‘struct fgraph_ret_regs’ declared inside parameter list will not be visible outside of this definition or declaration
> 
> Instead of asking to send another patch series, just add it and then apply
> the updates.
> 
> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
> ---
>  kernel/trace/fgraph.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c
> index 218cd95bf8e4..ea3d7bb235d3 100644
> --- a/kernel/trace/fgraph.c
> +++ b/kernel/trace/fgraph.c
> @@ -236,6 +236,9 @@ static struct notifier_block ftrace_suspend_notifier = {
>  	.notifier_call = ftrace_suspend_notifier_call,
>  };
>  
> +/* fgraph_ret_regs is not defined without CONFIG_FUNCTION_GRAPH_RETVAL */
> +struct fgraph_ret_regs;
> +
>  /*
>   * Send the trace to the ring-buffer.
>   * @return the original return address.