ftrace: move memory management out of arch code

This patch moves the memory management of the ftrace
records out of the arch code and into the generic code
making the arch code simpler.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

kernel/trace/ftrace.c

@@ -156,6 +156,21 @@ static DEFINE_PER_CPU(int, ftrace_shutdown_disable_cpu);
 static DEFINE_SPINLOCK(ftrace_shutdown_lock);
 static DEFINE_MUTEX(ftraced_lock);
 
+struct ftrace_page {
+	struct ftrace_page	*next;
+	int			index;
+	struct dyn_ftrace	records[];
+} __attribute__((packed));
+
+#define ENTRIES_PER_PAGE \
+  ((PAGE_SIZE - sizeof(struct ftrace_page)) / sizeof(struct dyn_ftrace))
+
+/* estimate from running different kernels */
+#define NR_TO_INIT		10000
+
+static struct ftrace_page	*ftrace_pages_start;
+static struct ftrace_page	*ftrace_pages;
+
 static int ftraced_trigger;
 static int ftraced_suspend;
 
@@ -184,6 +199,21 @@ ftrace_add_hash(struct dyn_ftrace *node, unsigned long key)
 	hlist_add_head(&node->node, &ftrace_hash[key]);
 }
 
+static notrace struct dyn_ftrace *ftrace_alloc_shutdown_node(unsigned long ip)
+{
+	/* If this was already converted, skip it */
+	if (ftrace_ip_converted(ip))
+		return NULL;
+
+	if (ftrace_pages->index == ENTRIES_PER_PAGE) {
+		if (!ftrace_pages->next)
+			return NULL;
+		ftrace_pages = ftrace_pages->next;
+	}
+
+	return &ftrace_pages->records[ftrace_pages->index++];
+}
+
 static void notrace
 ftrace_record_ip(unsigned long ip, unsigned long parent_ip)
 {
@@ -252,6 +282,62 @@ static struct ftrace_ops ftrace_shutdown_ops __read_mostly =
 	.func = ftrace_record_ip,
 };
 
+#define MCOUNT_ADDR ((long)(&mcount))
+
+static void notrace ftrace_replace_code(int saved)
+{
+	unsigned char *new = NULL, *old = NULL;
+	struct dyn_ftrace *rec;
+	struct ftrace_page *pg;
+	unsigned long ip;
+	int failed;
+	int i;
+
+	if (saved)
+		old = ftrace_nop_replace();
+	else
+		new = ftrace_nop_replace();
+
+	for (pg = ftrace_pages_start; pg; pg = pg->next) {
+		for (i = 0; i < pg->index; i++) {
+			rec = &pg->records[i];
+
+			/* don't modify code that has already faulted */
+			if (rec->flags & FTRACE_FL_FAILED)
+				continue;
+
+			ip = rec->ip;
+
+			if (saved)
+				new = ftrace_call_replace(ip, MCOUNT_ADDR);
+			else
+				old = ftrace_call_replace(ip, MCOUNT_ADDR);
+
+			failed = ftrace_modify_code(ip, old, new);
+			if (failed)
+				rec->flags |= FTRACE_FL_FAILED;
+		}
+	}
+}
+
+static notrace void ftrace_startup_code(void)
+{
+	ftrace_replace_code(1);
+}
+
+static notrace void ftrace_shutdown_code(void)
+{
+	ftrace_replace_code(0);
+}
+
+static notrace void ftrace_shutdown_replenish(void)
+{
+	if (ftrace_pages->next)
+		return;
+
+	/* allocate another page */
+	ftrace_pages->next = (void *)get_zeroed_page(GFP_KERNEL);
+}
 
 static int notrace __ftrace_modify_code(void *data)
 {
@@ -261,6 +347,23 @@ static int notrace __ftrace_modify_code(void *data)
 	return 0;
 }
 
+static notrace void
+ftrace_code_disable(struct dyn_ftrace *rec, unsigned long addr)
+{
+	unsigned long ip;
+	unsigned char *nop, *call;
+	int failed;
+
+	ip = rec->ip;
+
+	nop = ftrace_nop_replace();
+	call = ftrace_call_replace(ip, addr);
+
+	failed = ftrace_modify_code(ip, call, nop);
+	if (failed)
+		rec->flags |= FTRACE_FL_FAILED;
+}
+
 static void notrace ftrace_run_startup_code(void)
 {
 	stop_machine_run(__ftrace_modify_code, ftrace_startup_code, NR_CPUS);
@@ -346,7 +449,7 @@ static int notrace __ftrace_update_code(void *ignore)
 
 		/* all CPUS are stopped, we are safe to modify code */
 		hlist_for_each_entry(p, t, &head, node) {
-			ftrace_code_disable(p);
+			ftrace_code_disable(p, MCOUNT_ADDR);
 			ftrace_update_cnt++;
 		}
 
@@ -407,12 +510,59 @@ static int notrace ftraced(void *ignore)
 	return 0;
 }
 
+static int __init ftrace_dyn_table_alloc(void)
+{
+	struct ftrace_page *pg;
+	int cnt;
+	int i;
+	int ret;
+
+	ret = ftrace_dyn_arch_init();
+	if (ret)
+		return ret;
+
+	/* allocate a few pages */
+	ftrace_pages_start = (void *)get_zeroed_page(GFP_KERNEL);
+	if (!ftrace_pages_start)
+		return -1;
+
+	/*
+	 * Allocate a few more pages.
+	 *
+	 * TODO: have some parser search vmlinux before
+	 *   final linking to find all calls to ftrace.
+	 *   Then we can:
+	 *    a) know how many pages to allocate.
+	 *     and/or
+	 *    b) set up the table then.
+	 *
+	 *  The dynamic code is still necessary for
+	 *  modules.
+	 */
+
+	pg = ftrace_pages = ftrace_pages_start;
+
+	cnt = NR_TO_INIT / ENTRIES_PER_PAGE;
+
+	for (i = 0; i < cnt; i++) {
+		pg->next = (void *)get_zeroed_page(GFP_KERNEL);
+
+		/* If we fail, we'll try later anyway */
+		if (!pg->next)
+			break;
+
+		pg = pg->next;
+	}
+
+	return 0;
+}
+
 static int __init notrace ftrace_shutdown_init(void)
 {
 	struct task_struct *p;
 	int ret;
 
-	ret = ftrace_shutdown_arch_init();
+	ret = ftrace_dyn_table_alloc();
 	if (ret)
 		return ret;