diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 5e618c3b47208ed2f301c685a5596135b30cc78f..e142091524b0897f26f99673287692507f111ab7 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -56,6 +56,7 @@ obj-$(CONFIG_X86_MPPARSE) += mpparse.o
obj-$(CONFIG_X86_LOCAL_APIC) += apic_$(BITS).o nmi_$(BITS).o
obj-$(CONFIG_X86_IO_APIC) += io_apic_$(BITS).o
obj-$(CONFIG_X86_REBOOTFIXUPS) += reboot_fixups_32.o
+obj-$(CONFIG_DYNAMIC_FTRACE) += ftrace.o
obj-$(CONFIG_KEXEC) += machine_kexec_$(BITS).o
obj-$(CONFIG_KEXEC) += relocate_kernel_$(BITS).o crash.o
obj-$(CONFIG_CRASH_DUMP) += crash_dump_$(BITS).o
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
new file mode 100644
index 0000000000000000000000000000000000000000..5dd58136ef028c15b1ffbba2b8e787e71bbd43bd
--- /dev/null
+++ b/arch/x86/kernel/ftrace.c
@@ -0,0 +1,237 @@
+/*
+ * Code for replacing ftrace calls with jumps.
+ *
+ * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
+ *
+ * Thanks goes to Ingo Molnar, for suggesting the idea.
+ * Mathieu Desnoyers, for suggesting postponing the modifications.
+ * Arjan van de Ven, for keeping me straight, and explaining to me
+ * the dangers of modifying code on the run.
+ */
+
+#include <linux/spinlock.h>
+#include <linux/hardirq.h>
+#include <linux/ftrace.h>
+#include <linux/percpu.h>
+#include <linux/init.h>
+#include <linux/list.h>
+
+#define CALL_BACK 5
+
+#define JMPFWD 0x03eb
+
+static unsigned short ftrace_jmp = JMPFWD;
+
+struct ftrace_record {
+ struct dyn_ftrace rec;
+ int failed;
+} __attribute__((packed));
+
+struct ftrace_page {
+ struct ftrace_page *next;
+ int index;
+ struct ftrace_record records[];
+} __attribute__((packed));
+
+#define ENTRIES_PER_PAGE \
+ ((PAGE_SIZE - sizeof(struct ftrace_page)) / sizeof(struct ftrace_record))
+
+/* estimate from running different kernels */
+#define NR_TO_INIT 10000
+
+#define MCOUNT_ADDR ((long)(&mcount))
+
+union ftrace_code_union {
+ char code[5];
+ struct {
+ char e8;
+ int offset;
+ } __attribute__((packed));
+};
+
+static struct ftrace_page *ftrace_pages_start;
+static struct ftrace_page *ftrace_pages;
+
+notrace struct dyn_ftrace *ftrace_alloc_shutdown_node(unsigned long ip)
+{
+ struct ftrace_record *rec;
+ unsigned short save;
+
+ ip -= CALL_BACK;
+ save = *(short *)ip;
+
+ /* If this was already converted, skip it */
+ if (save == JMPFWD)
+ return NULL;
+
+ if (ftrace_pages->index == ENTRIES_PER_PAGE) {
+ if (!ftrace_pages->next)
+ return NULL;
+ ftrace_pages = ftrace_pages->next;
+ }
+
+ rec = &ftrace_pages->records[ftrace_pages->index++];
+
+ return &rec->rec;
+}
+
+static int notrace
+ftrace_modify_code(unsigned long ip, unsigned char *old_code,
+ unsigned char *new_code)
+{
+ unsigned short old = *(unsigned short *)old_code;
+ unsigned short new = *(unsigned short *)new_code;
+ unsigned short replaced;
+ int faulted = 0;
+
+ /*
+ * Note: Due to modules and __init, code can
+ * disappear and change, we need to protect against faulting
+ * as well as code changing.
+ *
+ * No real locking needed, this code is run through
+ * kstop_machine.
+ */
+ asm volatile (
+ "1: lock\n"
+ " cmpxchg %w3, (%2)\n"
+ "2:\n"
+ ".section .fixup, \"ax\"\n"
+ " movl $1, %0\n"
+ "3: jmp 2b\n"
+ ".previous\n"
+ _ASM_EXTABLE(1b, 3b)
+ : "=r"(faulted), "=a"(replaced)
+ : "r"(ip), "r"(new), "0"(faulted), "a"(old)
+ : "memory");
+ sync_core();
+
+ if (replaced != old)
+ faulted = 2;
+
+ return faulted;
+}
+
+static int notrace ftrace_calc_offset(long ip)
+{
+ return (int)(MCOUNT_ADDR - ip);
+}
+
+notrace void ftrace_code_disable(struct dyn_ftrace *rec)
+{
+ unsigned long ip;
+ union ftrace_code_union save;
+ struct ftrace_record *r =
+ container_of(rec, struct ftrace_record, rec);
+
+ ip = rec->ip;
+
+ save.e8 = 0xe8;
+ save.offset = ftrace_calc_offset(ip);
+
+ /* move the IP back to the start of the call */
+ ip -= CALL_BACK;
+
+ r->failed = ftrace_modify_code(ip, save.code, (char *)&ftrace_jmp);
+}
+
+static void notrace ftrace_replace_code(int saved)
+{
+ unsigned char *new = NULL, *old = NULL;
+ struct ftrace_record *rec;
+ struct ftrace_page *pg;
+ unsigned long ip;
+ int i;
+
+ if (saved)
+ old = (char *)&ftrace_jmp;
+ else
+ new = (char *)&ftrace_jmp;
+
+ for (pg = ftrace_pages_start; pg; pg = pg->next) {
+ for (i = 0; i < pg->index; i++) {
+ union ftrace_code_union calc;
+ rec = &pg->records[i];
+
+ /* don't modify code that has already faulted */
+ if (rec->failed)
+ continue;
+
+ ip = rec->rec.ip;
+
+ calc.e8 = 0xe8;
+ calc.offset = ftrace_calc_offset(ip);
+
+ if (saved)
+ new = calc.code;
+ else
+ old = calc.code;
+
+ ip -= CALL_BACK;
+
+ rec->failed = ftrace_modify_code(ip, old, new);
+ }
+ }
+
+}
+
+notrace void ftrace_startup_code(void)
+{
+ ftrace_replace_code(1);
+}
+
+notrace void ftrace_shutdown_code(void)
+{
+ ftrace_replace_code(0);
+}
+
+notrace void ftrace_shutdown_replenish(void)
+{
+ if (ftrace_pages->next)
+ return;
+
+ /* allocate another page */
+ ftrace_pages->next = (void *)get_zeroed_page(GFP_KERNEL);
+}
+
+notrace int ftrace_shutdown_arch_init(void)
+{
+ struct ftrace_page *pg;
+ int cnt;
+ int i;
+
+ /* 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;
+}
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 740c97dcf9cb831fc2092458b913c3a1de571a72..90dbc0ee2046506c1cf4f3e6def0fef3e242b5e2 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -32,6 +32,24 @@ extern void mcount(void);
# define clear_ftrace_function(ops) do { } while (0)
#endif /* CONFIG_FTRACE */
+#ifdef CONFIG_DYNAMIC_FTRACE
+# define FTRACE_HASHBITS 10
+# define FTRACE_HASHSIZE (1<<FTRACE_HASHBITS)
+
+struct dyn_ftrace {
+ struct hlist_node node;
+ unsigned long ip;
+};
+
+/* defined in arch */
+extern struct dyn_ftrace *
+ftrace_alloc_shutdown_node(unsigned long ip);
+extern int ftrace_shutdown_arch_init(void);
+extern void ftrace_code_disable(struct dyn_ftrace *rec);
+extern void ftrace_startup_code(void);
+extern void ftrace_shutdown_code(void);
+extern void ftrace_shutdown_replenish(void);
+#endif
#ifdef CONFIG_FRAME_POINTER
/* TODO: need to fix this for ARM */
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 6430016b98e8fcb16dea44d53c77c53ef4753e88..cad9db1dee02386c0a7c989a03b84b3d341648e5 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -88,3 +88,20 @@ config CONTEXT_SWITCH_TRACER
This tracer gets called from the context switch and records
all switching of tasks.
+config DYNAMIC_FTRACE
+ bool "enable/disable ftrace tracepoints dynamically"
+ depends on FTRACE
+ default y
+ help
+ This option will modify all the calls to ftrace dynamically
+ (will patch them out of the binary image and replaces them
+ with a No-Op instruction) as they are called. A table is
+ created to dynamically enable them again.
+
+ This way a CONFIG_FTRACE kernel is slightly larger, but otherwise
+ has native performance as long as no tracing is active.
+
+ The changes to the code are done by a kernel thread that
+ wakes up once a second and checks to see if any ftrace calls
+ were made. If so, it runs stop_machine (stops all CPUS)
+ and modifies the code to jump over the call to ftrace.
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index b6a80b98a3fb7854e6747e4276af3930370a96ca..d1ae2ba25274c10f20d578ef9c1b2a566c2134e1 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -13,10 +13,19 @@
* Copyright (C) 2004 William Lee Irwin III
*/
-#include <linux/module.h>
+#include <linux/stop_machine.h>
+#include <linux/clocksource.h>
+#include <linux/kallsyms.h>
+#include <linux/kthread.h>
+#include <linux/hardirq.h>
#include <linux/ftrace.h>
+#include <linux/module.h>
+#include <linux/hash.h>
+#include <linux/list.h>
+
+#include "trace.h"
-static DEFINE_SPINLOCK(ftrace_func_lock);
+static DEFINE_SPINLOCK(ftrace_lock);
static struct ftrace_ops ftrace_list_end __read_mostly =
{
.func = ftrace_stub,
@@ -44,21 +53,21 @@ notrace void ftrace_list_func(unsigned long ip, unsigned long parent_ip)
}
/**
- * register_ftrace_function - register a function for profiling
- * @ops - ops structure that holds the function for profiling.
- *
- * Register a function to be called by all functions in the
- * kernel.
+ * clear_ftrace_function - reset the ftrace function
*
- * Note: @ops->func and all the functions it calls must be labeled
- * with "notrace", otherwise it will go into a
- * recursive loop.
+ * This NULLs the ftrace function and in essence stops
+ * tracing. There may be lag
*/
-int register_ftrace_function(struct ftrace_ops *ops)
+void clear_ftrace_function(void)
{
- unsigned long flags;
+ ftrace_trace_function = ftrace_stub;
+}
+
+static int notrace __register_ftrace_function(struct ftrace_ops *ops)
+{
+ /* Should never be called by interrupts */
+ spin_lock(&ftrace_lock);
- spin_lock_irqsave(&ftrace_func_lock, flags);
ops->next = ftrace_list;
/*
* We are entering ops into the ftrace_list but another
@@ -68,6 +77,7 @@ int register_ftrace_function(struct ftrace_ops *ops)
*/
smp_wmb();
ftrace_list = ops;
+
/*
* For one func, simply call it directly.
* For more than one func, call the chain.
@@ -76,28 +86,22 @@ int register_ftrace_function(struct ftrace_ops *ops)
ftrace_trace_function = ops->func;
else
ftrace_trace_function = ftrace_list_func;
- spin_unlock_irqrestore(&ftrace_func_lock, flags);
+
+ spin_unlock(&ftrace_lock);
return 0;
}
-/**
- * unregister_ftrace_function - unresgister a function for profiling.
- * @ops - ops structure that holds the function to unregister
- *
- * Unregister a function that was added to be called by ftrace profiling.
- */
-int unregister_ftrace_function(struct ftrace_ops *ops)
+static int notrace __unregister_ftrace_function(struct ftrace_ops *ops)
{
- unsigned long flags;
struct ftrace_ops **p;
int ret = 0;
- spin_lock_irqsave(&ftrace_func_lock, flags);
+ spin_lock(&ftrace_lock);
/*
- * If we are the only function, then the ftrace pointer is
- * pointing directly to that function.
+ * If we are removing the last function, then simply point
+ * to the ftrace_stub.
*/
if (ftrace_list == ops && ops->next == &ftrace_list_end) {
ftrace_trace_function = ftrace_stub;
@@ -117,22 +121,310 @@ int unregister_ftrace_function(struct ftrace_ops *ops)
*p = (*p)->next;
/* If we only have one func left, then call that directly */
- if (ftrace_list->next == &ftrace_list_end)
+ if (ftrace_list == &ftrace_list_end ||
+ ftrace_list->next == &ftrace_list_end)
ftrace_trace_function = ftrace_list->func;
out:
- spin_unlock_irqrestore(&ftrace_func_lock, flags);
+ spin_unlock(&ftrace_lock);
+
+ return ret;
+}
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+
+static struct hlist_head ftrace_hash[FTRACE_HASHSIZE];
+
+static DEFINE_PER_CPU(int, ftrace_shutdown_disable_cpu);
+
+static DEFINE_SPINLOCK(ftrace_shutdown_lock);
+static DEFINE_MUTEX(ftraced_lock);
+
+static int ftraced_trigger;
+static int ftraced_suspend;
+
+static int ftrace_record_suspend;
+
+static inline int
+notrace ftrace_ip_in_hash(unsigned long ip, unsigned long key)
+{
+ struct dyn_ftrace *p;
+ struct hlist_node *t;
+ int found = 0;
+
+ hlist_for_each_entry(p, t, &ftrace_hash[key], node) {
+ if (p->ip == ip) {
+ found = 1;
+ break;
+ }
+ }
+
+ return found;
+}
+
+static inline void notrace
+ftrace_add_hash(struct dyn_ftrace *node, unsigned long key)
+{
+ hlist_add_head(&node->node, &ftrace_hash[key]);
+}
+
+static void notrace
+ftrace_record_ip(unsigned long ip, unsigned long parent_ip)
+{
+ struct dyn_ftrace *node;
+ unsigned long flags;
+ unsigned long key;
+ int resched;
+ int atomic;
+
+ resched = need_resched();
+ preempt_disable_notrace();
+
+ /* We simply need to protect against recursion */
+ __get_cpu_var(ftrace_shutdown_disable_cpu)++;
+ if (__get_cpu_var(ftrace_shutdown_disable_cpu) != 1)
+ goto out;
+
+ if (unlikely(ftrace_record_suspend))
+ goto out;
+
+ key = hash_long(ip, FTRACE_HASHBITS);
+
+ WARN_ON_ONCE(key >= FTRACE_HASHSIZE);
+
+ if (ftrace_ip_in_hash(ip, key))
+ goto out;
+
+ atomic = irqs_disabled();
+
+ spin_lock_irqsave(&ftrace_shutdown_lock, flags);
+
+ /* This ip may have hit the hash before the lock */
+ if (ftrace_ip_in_hash(ip, key))
+ goto out_unlock;
+
+ /*
+ * There's a slight race that the ftraced will update the
+ * hash and reset here. The arch alloc is responsible
+ * for seeing if the IP has already changed, and if
+ * it has, the alloc will fail.
+ */
+ node = ftrace_alloc_shutdown_node(ip);
+ if (!node)
+ goto out_unlock;
+
+ node->ip = ip;
+
+ ftrace_add_hash(node, key);
+
+ ftraced_trigger = 1;
+
+ out_unlock:
+ spin_unlock_irqrestore(&ftrace_shutdown_lock, flags);
+ out:
+ __get_cpu_var(ftrace_shutdown_disable_cpu)--;
+
+ /* prevent recursion with scheduler */
+ if (resched)
+ preempt_enable_no_resched_notrace();
+ else
+ preempt_enable_notrace();
+}
+
+static struct ftrace_ops ftrace_shutdown_ops __read_mostly =
+{
+ .func = ftrace_record_ip,
+};
+
+
+static int notrace __ftrace_modify_code(void *data)
+{
+ void (*func)(void) = data;
+
+ func();
+ return 0;
+}
+
+static void notrace ftrace_run_startup_code(void)
+{
+ stop_machine_run(__ftrace_modify_code, ftrace_startup_code, NR_CPUS);
+}
+
+static void notrace ftrace_run_shutdown_code(void)
+{
+ stop_machine_run(__ftrace_modify_code, ftrace_shutdown_code, NR_CPUS);
+}
+
+static void notrace ftrace_startup(void)
+{
+ mutex_lock(&ftraced_lock);
+ ftraced_suspend++;
+ if (ftraced_suspend != 1)
+ goto out;
+ __unregister_ftrace_function(&ftrace_shutdown_ops);
+
+ ftrace_run_startup_code();
+ out:
+ mutex_unlock(&ftraced_lock);
+}
+
+static void notrace ftrace_shutdown(void)
+{
+ mutex_lock(&ftraced_lock);
+ ftraced_suspend--;
+ if (ftraced_suspend)
+ goto out;
+
+ ftrace_run_shutdown_code();
+
+ __register_ftrace_function(&ftrace_shutdown_ops);
+ out:
+ mutex_unlock(&ftraced_lock);
+}
+
+static cycle_t ftrace_update_time;
+static unsigned long ftrace_update_cnt;
+unsigned long ftrace_update_tot_cnt;
+
+static int notrace __ftrace_update_code(void *ignore)
+{
+ struct dyn_ftrace *p;
+ struct hlist_head head;
+ struct hlist_node *t;
+ cycle_t start, stop;
+ int i;
+
+ /* Don't be calling ftrace ops now */
+ __unregister_ftrace_function(&ftrace_shutdown_ops);
+
+ start = now(raw_smp_processor_id());
+ ftrace_update_cnt = 0;
+
+ /* No locks needed, the machine is stopped! */
+ for (i = 0; i < FTRACE_HASHSIZE; i++) {
+ if (hlist_empty(&ftrace_hash[i]))
+ continue;
+
+ head = ftrace_hash[i];
+ INIT_HLIST_HEAD(&ftrace_hash[i]);
+
+ /* all CPUS are stopped, we are safe to modify code */
+ hlist_for_each_entry(p, t, &head, node) {
+ ftrace_code_disable(p);
+ ftrace_update_cnt++;
+ }
+
+ }
+
+ stop = now(raw_smp_processor_id());
+ ftrace_update_time = stop - start;
+ ftrace_update_tot_cnt += ftrace_update_cnt;
+
+ __register_ftrace_function(&ftrace_shutdown_ops);
return 0;
}
+static void notrace ftrace_update_code(void)
+{
+ stop_machine_run(__ftrace_update_code, NULL, NR_CPUS);
+}
+
+static int notrace ftraced(void *ignore)
+{
+ unsigned long usecs;
+
+ set_current_state(TASK_INTERRUPTIBLE);
+
+ while (!kthread_should_stop()) {
+
+ /* check once a second */
+ schedule_timeout(HZ);
+
+ mutex_lock(&ftraced_lock);
+ if (ftraced_trigger && !ftraced_suspend) {
+ ftrace_record_suspend++;
+ ftrace_update_code();
+ usecs = nsecs_to_usecs(ftrace_update_time);
+ if (ftrace_update_tot_cnt > 100000) {
+ ftrace_update_tot_cnt = 0;
+ pr_info("hm, dftrace overflow: %lu change%s"
+ " (%lu total) in %lu usec%s\n",
+ ftrace_update_cnt,
+ ftrace_update_cnt != 1 ? "s" : "",
+ ftrace_update_tot_cnt,
+ usecs, usecs != 1 ? "s" : "");
+ WARN_ON_ONCE(1);
+ }
+ ftraced_trigger = 0;
+ ftrace_record_suspend--;
+ }
+ mutex_unlock(&ftraced_lock);
+
+ ftrace_shutdown_replenish();
+
+ set_current_state(TASK_INTERRUPTIBLE);
+ }
+ __set_current_state(TASK_RUNNING);
+ return 0;
+}
+
+static int __init notrace ftrace_shutdown_init(void)
+{
+ struct task_struct *p;
+ int ret;
+
+ ret = ftrace_shutdown_arch_init();
+ if (ret)
+ return ret;
+
+ p = kthread_run(ftraced, NULL, "ftraced");
+ if (IS_ERR(p))
+ return -1;
+
+ __register_ftrace_function(&ftrace_shutdown_ops);
+
+ return 0;
+}
+
+core_initcall(ftrace_shutdown_init);
+#else
+# define ftrace_startup() do { } while (0)
+# define ftrace_shutdown() do { } while (0)
+#endif /* CONFIG_DYNAMIC_FTRACE */
+
/**
- * clear_ftrace_function - reset the ftrace function
+ * register_ftrace_function - register a function for profiling
+ * @ops - ops structure that holds the function for profiling.
*
- * This NULLs the ftrace function and in essence stops
- * tracing. There may be lag
+ * Register a function to be called by all functions in the
+ * kernel.
+ *
+ * Note: @ops->func and all the functions it calls must be labeled
+ * with "notrace", otherwise it will go into a
+ * recursive loop.
*/
-void clear_ftrace_function(void)
+int register_ftrace_function(struct ftrace_ops *ops)
{
- ftrace_trace_function = ftrace_stub;
+ ftrace_startup();
+
+ return __register_ftrace_function(ops);
+}
+
+/**
+ * unregister_ftrace_function - unresgister a function for profiling.
+ * @ops - ops structure that holds the function to unregister
+ *
+ * Unregister a function that was added to be called by ftrace profiling.
+ */
+int unregister_ftrace_function(struct ftrace_ops *ops)
+{
+ int ret;
+
+ ret = __unregister_ftrace_function(ops);
+
+ if (ftrace_list == &ftrace_list_end)
+ ftrace_shutdown();
+
+ return ret;
}