Fixes and minor clean ups for tracing:

- Fix memory leak by reverting what was thought to be a double free.
    A static tool had gave a false positive that a double free was
    possible in the error path, but it was actually a different location
    that confused the static analyzer (and those of us that reviewed it).
 
  - Move use of static buffers by ftrace_dump() to a location that can
    be used by kgdb's ftdump(), as it needs it for the same reasons.
 
  - Clarify in the Kconfig description that function tracing has negligible
    impact on x86, but may have a bit bigger impact on other architectures.
 
  - Remove unnecessary extra semicolon in trace event.
 
  - Make a local variable static that is used in the fprobes sample
 
  - Use KSYM_NAME_LEN for length of function in kprobe sample and get
    rid of unneeded macro for the same purpose.
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Merge tag 'trace-v5.19-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull tracing fixes from Steven Rostedt:
 "Fixes and minor clean ups for tracing:

   - Fix memory leak by reverting what was thought to be a double free.

     A static tool had gave a false positive that a double free was
     possible in the error path, but it was actually a different
     location that confused the static analyzer (and those of us that
     reviewed it).

   - Move use of static buffers by ftrace_dump() to a location that can
     be used by kgdb's ftdump(), as it needs it for the same reasons.

   - Clarify in the Kconfig description that function tracing has
     negligible impact on x86, but may have a bit bigger impact on other
     architectures.

   - Remove unnecessary extra semicolon in trace event.

   - Make a local variable static that is used in the fprobes sample

   - Use KSYM_NAME_LEN for length of function in kprobe sample and get
     rid of unneeded macro for the same purpose"

* tag 'trace-v5.19-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  samples: Use KSYM_NAME_LEN for kprobes
  fprobe/samples: Make sample_probe static
  blk-iocost: tracing: atomic64_read(&ioc->vtime_rate) is assigned an extra semicolon
  ftrace: Be more specific about arch impact when function tracer is enabled
  tracing: Fix sleeping while atomic in kdb ftdump
  tracing/histograms: Fix memory leak problem

include/trace/events/iocost.h

@@ -160,7 +160,7 @@ TRACE_EVENT(iocost_ioc_vrate_adj,
 
 	TP_fast_assign(
 		__assign_str(devname, ioc_name(ioc));
-		__entry->old_vrate = atomic64_read(&ioc->vtime_rate);;
+		__entry->old_vrate = atomic64_read(&ioc->vtime_rate);
 		__entry->new_vrate = new_vrate;
 		__entry->busy_level = ioc->busy_level;
 		__entry->read_missed_ppm = missed_ppm[READ];

kernel/trace/Kconfig

@@ -194,7 +194,8 @@ config FUNCTION_TRACER
 	  sequence is then dynamically patched into a tracer call when
 	  tracing is enabled by the administrator. If it's runtime disabled
 	  (the bootup default), then the overhead of the instructions is very
-	  small and not measurable even in micro-benchmarks.
+	  small and not measurable even in micro-benchmarks (at least on
+	  x86, but may have impact on other architectures).
 
 config FUNCTION_GRAPH_TRACER
 	bool "Kernel Function Graph Tracer"

kernel/trace/trace.c

@@ -9864,6 +9864,12 @@ void trace_init_global_iter(struct trace_iterator *iter)
 	/* Output in nanoseconds only if we are using a clock in nanoseconds. */
 	if (trace_clocks[iter->tr->clock_id].in_ns)
 		iter->iter_flags |= TRACE_FILE_TIME_IN_NS;
+
+	/* Can not use kmalloc for iter.temp and iter.fmt */
+	iter->temp = static_temp_buf;
+	iter->temp_size = STATIC_TEMP_BUF_SIZE;
+	iter->fmt = static_fmt_buf;
+	iter->fmt_size = STATIC_FMT_BUF_SIZE;
 }
 
 void ftrace_dump(enum ftrace_dump_mode oops_dump_mode)
@@ -9896,11 +9902,6 @@ void ftrace_dump(enum ftrace_dump_mode oops_dump_mode)
 
 	/* Simulate the iterator */
 	trace_init_global_iter(&iter);
-	/* Can not use kmalloc for iter.temp and iter.fmt */
-	iter.temp = static_temp_buf;
-	iter.temp_size = STATIC_TEMP_BUF_SIZE;
-	iter.fmt = static_fmt_buf;
-	iter.fmt_size = STATIC_FMT_BUF_SIZE;
 
 	for_each_tracing_cpu(cpu) {
 		atomic_inc(&per_cpu_ptr(iter.array_buffer->data, cpu)->disabled);

kernel/trace/trace_events_hist.c

@@ -4430,6 +4430,8 @@ static int parse_var_defs(struct hist_trigger_data *hist_data)
 
 			s = kstrdup(field_str, GFP_KERNEL);
 			if (!s) {
+				kfree(hist_data->attrs->var_defs.name[n_vars]);
+				hist_data->attrs->var_defs.name[n_vars] = NULL;
 				ret = -ENOMEM;
 				goto free;
 			}

samples/fprobe/fprobe_example.c

@@ -20,7 +20,7 @@
 
 #define BACKTRACE_DEPTH 16
 #define MAX_SYMBOL_LEN 4096
-struct fprobe sample_probe;
+static struct fprobe sample_probe;
 static unsigned long nhit;
 
 static char symbol[MAX_SYMBOL_LEN] = "kernel_clone";

samples/kprobes/kprobe_example.c

@@ -16,9 +16,8 @@
 #include <linux/module.h>
 #include <linux/kprobes.h>
 
-#define MAX_SYMBOL_LEN	64
+static char symbol[KSYM_NAME_LEN] = "kernel_clone";
-static char symbol[MAX_SYMBOL_LEN] = "kernel_clone";
+module_param_string(symbol, symbol, KSYM_NAME_LEN, 0644);
-module_param_string(symbol, symbol, sizeof(symbol), 0644);
 
 /* For each probe you need to allocate a kprobe structure */
 static struct kprobe kp = {

samples/kprobes/kretprobe_example.c

@@ -23,11 +23,10 @@
 #include <linux/module.h>
 #include <linux/kprobes.h>
 #include <linux/ktime.h>
-#include <linux/limits.h>
 #include <linux/sched.h>
 
-static char func_name[NAME_MAX] = "kernel_clone";
+static char func_name[KSYM_NAME_LEN] = "kernel_clone";
-module_param_string(func, func_name, NAME_MAX, S_IRUGO);
+module_param_string(func, func_name, KSYM_NAME_LEN, 0644);
 MODULE_PARM_DESC(func, "Function to kretprobe; this module will report the"
 			" function's execution time");