tracing: Remove ksym tracer

The ksym (breakpoint) ftrace plugin has been superseded by perf
tools that are much more poweful to use the cpu breakpoints.
This tracer doesn't bring more feature. It has been deprecated
for a while now, lets remove it.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Prasad <prasad@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>

kernel/trace/Kconfig

@@ -308,28 +308,6 @@ config BRANCH_TRACER
 
 	  Say N if unsure.
 
-config KSYM_TRACER
-	bool "Trace read and write access on kernel memory locations"
-	depends on HAVE_HW_BREAKPOINT
-	select TRACING
-	help
-	  This tracer helps find read and write operations on any given kernel
-	  symbol i.e. /proc/kallsyms.
-
-config PROFILE_KSYM_TRACER
-	bool "Profile all kernel memory accesses on 'watched' variables"
-	depends on KSYM_TRACER
-	help
-	  This tracer profiles kernel accesses on variables watched through the
-	  ksym tracer ftrace plugin. Depending upon the hardware, all read
-	  and write operations on kernel variables can be monitored for
-	  accesses.
-
-	  The results will be displayed in:
-	  /debugfs/tracing/profile_ksym
-
-	  Say N if unsure.
-
 config STACK_TRACER
 	bool "Trace max stack"
 	depends on HAVE_FUNCTION_TRACER

kernel/trace/Makefile

@@ -53,7 +53,6 @@ obj-$(CONFIG_EVENT_TRACING) += trace_event_perf.o
 endif
 obj-$(CONFIG_EVENT_TRACING) += trace_events_filter.o
 obj-$(CONFIG_KPROBE_EVENT) += trace_kprobe.o
-obj-$(CONFIG_KSYM_TRACER) += trace_ksym.o
 obj-$(CONFIG_EVENT_TRACING) += power-traces.o
 
 libftrace-y := ftrace.o

kernel/trace/trace.h

@@ -30,7 +30,6 @@ enum trace_type {
 	TRACE_GRAPH_ENT,
 	TRACE_USER_STACK,
 	TRACE_BLK,
-	TRACE_KSYM,
 
 	__TRACE_LAST_TYPE,
 };
@@ -200,7 +199,6 @@ extern void __ftrace_bad_type(void);
 			  TRACE_GRAPH_ENT);		\
 		IF_ASSIGN(var, ent, struct ftrace_graph_ret_entry,	\
 			  TRACE_GRAPH_RET);		\
-		IF_ASSIGN(var, ent, struct ksym_trace_entry, TRACE_KSYM);\
 		__ftrace_bad_type();					\
 	} while (0)
 
@@ -361,8 +359,6 @@ int register_tracer(struct tracer *type);
 void unregister_tracer(struct tracer *type);
 int is_tracing_stopped(void);
 
-extern int process_new_ksym_entry(char *ksymname, int op, unsigned long addr);
-
 extern unsigned long nsecs_to_usecs(unsigned long nsecs);
 
 extern unsigned long tracing_thresh;
@@ -436,8 +432,6 @@ extern int trace_selftest_startup_sysprof(struct tracer *trace,
 					       struct trace_array *tr);
 extern int trace_selftest_startup_branch(struct tracer *trace,
 					 struct trace_array *tr);
-extern int trace_selftest_startup_ksym(struct tracer *trace,
-					 struct trace_array *tr);
 #endif /* CONFIG_FTRACE_STARTUP_TEST */
 
 extern void *head_page(struct trace_array_cpu *data);

kernel/trace/trace_entries.h

@@ -291,18 +291,3 @@ FTRACE_ENTRY(branch, trace_branch,
 		 __entry->func, __entry->file, __entry->correct)
 );
 
-FTRACE_ENTRY(ksym_trace, ksym_trace_entry,
-
-	TRACE_KSYM,
-
-	F_STRUCT(
-		__field(	unsigned long,	ip			  )
-		__field(	unsigned char,	type			  )
-		__array(	char	     ,	cmd,	   TASK_COMM_LEN  )
-		__field(	unsigned long,  addr			  )
-	),
-
-	F_printk("ip: %pF type: %d ksym_name: %pS cmd: %s",
-		(void *)__entry->ip, (unsigned int)__entry->type,
-		(void *)__entry->addr,  __entry->cmd)
-);

kernel/trace/trace_ksym.c

-/*
- * trace_ksym.c - Kernel Symbol Tracer
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
- *
- * Copyright (C) IBM Corporation, 2009
- */
-
-#include <linux/kallsyms.h>
-#include <linux/uaccess.h>
-#include <linux/debugfs.h>
-#include <linux/ftrace.h>
-#include <linux/module.h>
-#include <linux/slab.h>
-#include <linux/fs.h>
-
-#include "trace_output.h"
-#include "trace.h"
-
-#include <linux/hw_breakpoint.h>
-#include <asm/hw_breakpoint.h>
-
-#include <asm/atomic.h>
-
-#define KSYM_TRACER_OP_LEN 3 /* rw- */
-
-struct trace_ksym {
-	struct perf_event	**ksym_hbp;
-	struct perf_event_attr	attr;
-#ifdef CONFIG_PROFILE_KSYM_TRACER
-	atomic64_t		counter;
-#endif
-	struct hlist_node	ksym_hlist;
-};
-
-static struct trace_array *ksym_trace_array;
-
-static unsigned int ksym_tracing_enabled;
-
-static HLIST_HEAD(ksym_filter_head);
-
-static DEFINE_MUTEX(ksym_tracer_mutex);
-
-#ifdef CONFIG_PROFILE_KSYM_TRACER
-
-#define MAX_UL_INT 0xffffffff
-
-void ksym_collect_stats(unsigned long hbp_hit_addr)
-{
-	struct hlist_node *node;
-	struct trace_ksym *entry;
-
-	rcu_read_lock();
-	hlist_for_each_entry_rcu(entry, node, &ksym_filter_head, ksym_hlist) {
-		if (entry->attr.bp_addr == hbp_hit_addr) {
-			atomic64_inc(&entry->counter);
-			break;
-		}
-	}
-	rcu_read_unlock();
-}
-#endif /* CONFIG_PROFILE_KSYM_TRACER */
-
-void ksym_hbp_handler(struct perf_event *hbp, int nmi,
-		      struct perf_sample_data *data,
-		      struct pt_regs *regs)
-{
-	struct ring_buffer_event *event;
-	struct ksym_trace_entry *entry;
-	struct ring_buffer *buffer;
-	int pc;
-
-	if (!ksym_tracing_enabled)
-		return;
-
-	buffer = ksym_trace_array->buffer;
-
-	pc = preempt_count();
-
-	event = trace_buffer_lock_reserve(buffer, TRACE_KSYM,
-							sizeof(*entry), 0, pc);
-	if (!event)
-		return;
-
-	entry		= ring_buffer_event_data(event);
-	entry->ip	= instruction_pointer(regs);
-	entry->type	= hw_breakpoint_type(hbp);
-	entry->addr	= hw_breakpoint_addr(hbp);
-	strlcpy(entry->cmd, current->comm, TASK_COMM_LEN);
-
-#ifdef CONFIG_PROFILE_KSYM_TRACER
-	ksym_collect_stats(hw_breakpoint_addr(hbp));
-#endif /* CONFIG_PROFILE_KSYM_TRACER */
-
-	trace_buffer_unlock_commit(buffer, event, 0, pc);
-}
-
-/* Valid access types are represented as
- *
- * rw- : Set Read/Write Access Breakpoint
- * -w- : Set Write Access Breakpoint
- * --- : Clear Breakpoints
- * --x : Set Execution Break points (Not available yet)
- *
- */
-static int ksym_trace_get_access_type(char *str)
-{
-	int access = 0;
-
-	if (str[0] == 'r')
-		access |= HW_BREAKPOINT_R;
-
-	if (str[1] == 'w')
-		access |= HW_BREAKPOINT_W;
-
-	if (str[2] == 'x')
-		access |= HW_BREAKPOINT_X;
-
-	switch (access) {
-	case HW_BREAKPOINT_R:
-	case HW_BREAKPOINT_W:
-	case HW_BREAKPOINT_W | HW_BREAKPOINT_R:
-		return access;
-	default:
-		return -EINVAL;
-	}
-}
-
-/*
- * There can be several possible malformed requests and we attempt to capture
- * all of them. We enumerate some of the rules
- * 1. We will not allow kernel symbols with ':' since it is used as a delimiter.
- *    i.e. multiple ':' symbols disallowed. Possible uses are of the form
- *    <module>:<ksym_name>:<op>.
- * 2. No delimiter symbol ':' in the input string
- * 3. Spurious operator symbols or symbols not in their respective positions
- * 4. <ksym_name>:--- i.e. clear breakpoint request when ksym_name not in file
- * 5. Kernel symbol not a part of /proc/kallsyms
- * 6. Duplicate requests
- */
-static int parse_ksym_trace_str(char *input_string, char **ksymname,
-							unsigned long *addr)
-{
-	int ret;
-
-	*ksymname = strsep(&input_string, ":");
-	*addr = kallsyms_lookup_name(*ksymname);
-
-	/* Check for malformed request: (2), (1) and (5) */
-	if ((!input_string) ||
-	    (strlen(input_string) != KSYM_TRACER_OP_LEN) ||
-	    (*addr == 0))
-		return -EINVAL;;
-
-	ret = ksym_trace_get_access_type(input_string);
-
-	return ret;
-}
-
-int process_new_ksym_entry(char *ksymname, int op, unsigned long addr)
-{
-	struct trace_ksym *entry;
-	int ret = -ENOMEM;
-
-	entry = kzalloc(sizeof(struct trace_ksym), GFP_KERNEL);
-	if (!entry)
-		return -ENOMEM;
-
-	hw_breakpoint_init(&entry->attr);
-
-	entry->attr.bp_type = op;
-	entry->attr.bp_addr = addr;
-	entry->attr.bp_len = HW_BREAKPOINT_LEN_4;
-
-	entry->ksym_hbp = register_wide_hw_breakpoint(&entry->attr,
-					ksym_hbp_handler);
-
-	if (IS_ERR(entry->ksym_hbp)) {
-		ret = PTR_ERR(entry->ksym_hbp);
-		if (ret == -ENOSPC) {
-			printk(KERN_ERR "ksym_tracer: Maximum limit reached."
-			" No new requests for tracing can be accepted now.\n");
-		} else {
-			printk(KERN_INFO "ksym_tracer request failed. Try again"
-					 " later!!\n");
-		}
-		goto err;
-	}
-
-	hlist_add_head_rcu(&(entry->ksym_hlist), &ksym_filter_head);
-
-	return 0;
-
-err:
-	kfree(entry);
-
-	return ret;
-}
-
-static ssize_t ksym_trace_filter_read(struct file *filp, char __user *ubuf,
-						size_t count, loff_t *ppos)
-{
-	struct trace_ksym *entry;
-	struct hlist_node *node;
-	struct trace_seq *s;
-	ssize_t cnt = 0;
-	int ret;
-
-	s = kmalloc(sizeof(*s), GFP_KERNEL);
-	if (!s)
-		return -ENOMEM;
-	trace_seq_init(s);
-
-	mutex_lock(&ksym_tracer_mutex);
-
-	hlist_for_each_entry(entry, node, &ksym_filter_head, ksym_hlist) {
-		ret = trace_seq_printf(s, "%pS:",
-				(void *)(unsigned long)entry->attr.bp_addr);
-		if (entry->attr.bp_type == HW_BREAKPOINT_R)
-			ret = trace_seq_puts(s, "r--\n");
-		else if (entry->attr.bp_type == HW_BREAKPOINT_W)
-			ret = trace_seq_puts(s, "-w-\n");
-		else if (entry->attr.bp_type == (HW_BREAKPOINT_W | HW_BREAKPOINT_R))
-			ret = trace_seq_puts(s, "rw-\n");
-		WARN_ON_ONCE(!ret);
-	}
-
-	cnt = simple_read_from_buffer(ubuf, count, ppos, s->buffer, s->len);
-
-	mutex_unlock(&ksym_tracer_mutex);
-
-	kfree(s);
-
-	return cnt;
-}
-
-static void __ksym_trace_reset(void)
-{
-	struct trace_ksym *entry;
-	struct hlist_node *node, *node1;
-
-	mutex_lock(&ksym_tracer_mutex);
-	hlist_for_each_entry_safe(entry, node, node1, &ksym_filter_head,
-								ksym_hlist) {
-		unregister_wide_hw_breakpoint(entry->ksym_hbp);
-		hlist_del_rcu(&(entry->ksym_hlist));
-		synchronize_rcu();
-		kfree(entry);
-	}
-	mutex_unlock(&ksym_tracer_mutex);
-}
-
-static ssize_t ksym_trace_filter_write(struct file *file,
-					const char __user *buffer,
-						size_t count, loff_t *ppos)
-{
-	struct trace_ksym *entry;
-	struct hlist_node *node;
-	char *buf, *input_string, *ksymname = NULL;
-	unsigned long ksym_addr = 0;
-	int ret, op, changed = 0;
-
-	buf = kzalloc(count + 1, GFP_KERNEL);
-	if (!buf)
-		return -ENOMEM;
-
-	ret = -EFAULT;
-	if (copy_from_user(buf, buffer, count))
-		goto out;
-
-	buf[count] = '\0';
-	input_string = strstrip(buf);
-
-	/*
-	 * Clear all breakpoints if:
-	 * 1: echo > ksym_trace_filter
-	 * 2: echo 0 > ksym_trace_filter
-	 * 3: echo "*:---" > ksym_trace_filter
-	 */
-	if (!input_string[0] || !strcmp(input_string, "0") ||
-	    !strcmp(input_string, "*:---")) {
-		__ksym_trace_reset();
-		ret = 0;
-		goto out;
-	}
-
-	ret = op = parse_ksym_trace_str(input_string, &ksymname, &ksym_addr);
-	if (ret < 0)
-		goto out;
-
-	mutex_lock(&ksym_tracer_mutex);
-
-	ret = -EINVAL;
-	hlist_for_each_entry(entry, node, &ksym_filter_head, ksym_hlist) {
-		if (entry->attr.bp_addr == ksym_addr) {
-			/* Check for malformed request: (6) */
-			if (entry->attr.bp_type != op)
-				changed = 1;
-			else
-				goto out_unlock;
-			break;
-		}
-	}
-	if (changed) {
-		unregister_wide_hw_breakpoint(entry->ksym_hbp);
-		entry->attr.bp_type = op;
-		ret = 0;
-		if (op > 0) {
-			entry->ksym_hbp =
-				register_wide_hw_breakpoint(&entry->attr,
-					ksym_hbp_handler);
-			if (IS_ERR(entry->ksym_hbp))
-				ret = PTR_ERR(entry->ksym_hbp);
-			else
-				goto out_unlock;
-		}
-		/* Error or "symbol:---" case: drop it */
-		hlist_del_rcu(&(entry->ksym_hlist));
-		synchronize_rcu();
-		kfree(entry);
-		goto out_unlock;
-	} else {
-		/* Check for malformed request: (4) */
-		if (op)
-			ret = process_new_ksym_entry(ksymname, op, ksym_addr);
-	}
-out_unlock:
-	mutex_unlock(&ksym_tracer_mutex);
-out:
-	kfree(buf);
-	return !ret ? count : ret;
-}
-
-static const struct file_operations ksym_tracing_fops = {
-	.open		= tracing_open_generic,
-	.read		= ksym_trace_filter_read,
-	.write		= ksym_trace_filter_write,
-};
-
-static void ksym_trace_reset(struct trace_array *tr)
-{
-	ksym_tracing_enabled = 0;
-	__ksym_trace_reset();
-}
-
-static int ksym_trace_init(struct trace_array *tr)
-{
-	int cpu, ret = 0;
-
-	for_each_online_cpu(cpu)
-		tracing_reset(tr, cpu);
-	ksym_tracing_enabled = 1;
-	ksym_trace_array = tr;
-
-	return ret;
-}
-
-static void ksym_trace_print_header(struct seq_file *m)
-{
-	seq_puts(m,
-		 "#       TASK-PID   CPU#      Symbol                    "
-		 "Type    Function\n");
-	seq_puts(m,
-		 "#          |        |          |                       "
-		 " |         |\n");
-}
-
-static enum print_line_t ksym_trace_output(struct trace_iterator *iter)
-{
-	struct trace_entry *entry = iter->ent;
-	struct trace_seq *s = &iter->seq;
-	struct ksym_trace_entry *field;
-	char str[KSYM_SYMBOL_LEN];
-	int ret;
-
-	if (entry->type != TRACE_KSYM)
-		return TRACE_TYPE_UNHANDLED;
-
-	trace_assign_type(field, entry);
-
-	ret = trace_seq_printf(s, "%11s-%-5d [%03d] %pS", field->cmd,
-				entry->pid, iter->cpu, (char *)field->addr);
-	if (!ret)
-		return TRACE_TYPE_PARTIAL_LINE;
-
-	switch (field->type) {
-	case HW_BREAKPOINT_R:
-		ret = trace_seq_printf(s, " R  ");
-		break;
-	case HW_BREAKPOINT_W:
-		ret = trace_seq_printf(s, " W  ");
-		break;
-	case HW_BREAKPOINT_R | HW_BREAKPOINT_W:
-		ret = trace_seq_printf(s, " RW ");
-		break;
-	default:
-		return TRACE_TYPE_PARTIAL_LINE;
-	}
-
-	if (!ret)
-		return TRACE_TYPE_PARTIAL_LINE;
-
-	sprint_symbol(str, field->ip);
-	ret = trace_seq_printf(s, "%s\n", str);
-	if (!ret)
-		return TRACE_TYPE_PARTIAL_LINE;
-
-	return TRACE_TYPE_HANDLED;
-}
-
-struct tracer ksym_tracer __read_mostly =
-{
-	.name		= "ksym_tracer",
-	.init		= ksym_trace_init,
-	.reset		= ksym_trace_reset,
-#ifdef CONFIG_FTRACE_SELFTEST
-	.selftest	= trace_selftest_startup_ksym,
-#endif
-	.print_header   = ksym_trace_print_header,
-	.print_line	= ksym_trace_output
-};
-
-#ifdef CONFIG_PROFILE_KSYM_TRACER
-static int ksym_profile_show(struct seq_file *m, void *v)
-{
-	struct hlist_node *node;
-	struct trace_ksym *entry;
-	int access_type = 0;
-	char fn_name[KSYM_NAME_LEN];
-
-	seq_puts(m, "  Access Type ");
-	seq_puts(m, "  Symbol                                       Counter\n");
-	seq_puts(m, "  ----------- ");
-	seq_puts(m, "  ------                                       -------\n");
-
-	rcu_read_lock();
-	hlist_for_each_entry_rcu(entry, node, &ksym_filter_head, ksym_hlist) {
-
-		access_type = entry->attr.bp_type;
-
-		switch (access_type) {
-		case HW_BREAKPOINT_R:
-			seq_puts(m, "  R           ");
-			break;
-		case HW_BREAKPOINT_W:
-			seq_puts(m, "  W           ");
-			break;
-		case HW_BREAKPOINT_R | HW_BREAKPOINT_W:
-			seq_puts(m, "  RW          ");
-			break;
-		default:
-			seq_puts(m, "  NA          ");
-		}
-
-		if (lookup_symbol_name(entry->attr.bp_addr, fn_name) >= 0)
-			seq_printf(m, "  %-36s", fn_name);
-		else
-			seq_printf(m, "  %-36s", "<NA>");
-		seq_printf(m, " %15llu\n",
-			   (unsigned long long)atomic64_read(&entry->counter));
-	}
-	rcu_read_unlock();
-
-	return 0;
-}
-
-static int ksym_profile_open(struct inode *node, struct file *file)
-{
-	return single_open(file, ksym_profile_show, NULL);
-}
-
-static const struct file_operations ksym_profile_fops = {
-	.open		= ksym_profile_open,
-	.read		= seq_read,
-	.llseek		= seq_lseek,
-	.release	= single_release,
-};
-#endif /* CONFIG_PROFILE_KSYM_TRACER */
-
-__init static int init_ksym_trace(void)
-{
-	struct dentry *d_tracer;
-
-	d_tracer = tracing_init_dentry();
-
-	trace_create_file("ksym_trace_filter", 0644, d_tracer,
-			  NULL, &ksym_tracing_fops);
-
-#ifdef CONFIG_PROFILE_KSYM_TRACER
-	trace_create_file("ksym_profile", 0444, d_tracer,
-			  NULL, &ksym_profile_fops);
-#endif
-
-	return register_tracer(&ksym_tracer);
-}
-device_initcall(init_ksym_trace);

kernel/trace/trace_selftest.c

@@ -17,7 +17,6 @@ static inline int trace_valid_entry(struct trace_entry *entry)
 	case TRACE_BRANCH:
 	case TRACE_GRAPH_ENT:
 	case TRACE_GRAPH_RET:
-	case TRACE_KSYM:
 		return 1;
 	}
 	return 0;
@@ -755,56 +754,3 @@ trace_selftest_startup_branch(struct tracer *trace, struct trace_array *tr)
 }
 #endif /* CONFIG_BRANCH_TRACER */
 
-#ifdef CONFIG_KSYM_TRACER
-static int ksym_selftest_dummy;
-
-int
-trace_selftest_startup_ksym(struct tracer *trace, struct trace_array *tr)
-{
-	unsigned long count;
-	int ret;
-
-	/* start the tracing */
-	ret = tracer_init(trace, tr);
-	if (ret) {
-		warn_failed_init_tracer(trace, ret);
-		return ret;
-	}
-
-	ksym_selftest_dummy = 0;
-	/* Register the read-write tracing request */
-
-	ret = process_new_ksym_entry("ksym_selftest_dummy",
-				     HW_BREAKPOINT_R | HW_BREAKPOINT_W,
-					(unsigned long)(&ksym_selftest_dummy));
-
-	if (ret < 0) {
-		printk(KERN_CONT "ksym_trace read-write startup test failed\n");
-		goto ret_path;
-	}
-	/* Perform a read and a write operation over the dummy variable to
-	 * trigger the tracer
-	 */
-	if (ksym_selftest_dummy == 0)
-		ksym_selftest_dummy++;
-
-	/* stop the tracing. */
-	tracing_stop();
-	/* check the trace buffer */
-	ret = trace_test_buffer(tr, &count);
-	trace->reset(tr);
-	tracing_start();
-
-	/* read & write operations - one each is performed on the dummy variable
-	 * triggering two entries in the trace buffer
-	 */
-	if (!ret && count != 2) {
-		printk(KERN_CONT "Ksym tracer startup test failed");
-		ret = -1;
-	}
-
-ret_path:
-	return ret;
-}
-#endif /* CONFIG_KSYM_TRACER */
-