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ftrace: use dynamic patching for updating mcount calls

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This patch replaces the indirect call to the mcount function
pointer with a direct call that will be patched by the
dynamic ftrace routines.

On boot up, the mcount function calls the ftace_stub function.
When the dynamic ftrace code is initialized, the ftrace_stub
is replaced with a call to the ftrace_record_ip, which records
the instruction pointers of the locations that call it.

Later, the ftraced daemon will call kstop_machine and patch all
the locations to nops.

When a ftrace is enabled, the original calls to mcount will now
be set top call ftrace_caller, which will do a direct call
to the registered ftrace function. This direct call is also patched
when the function that should be called is updated.

All patching is performed by a kstop_machine routine to prevent any
type of race conditions that is associated with modifying code
on the fly.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Steven Rostedt
2008-05-12 21:20:43 +02:00
committed by Thomas Gleixner
parent 3c1720f00b
commit d61f82d066
5 changed files with 262 additions and 85 deletions
Download Patch File Download Diff File Expand all files Collapse all files

185
kernel/trace/ftrace.c
View File

@@ -26,14 +26,8 @@
#include "trace.h"
#ifdef CONFIG_DYNAMIC_FTRACE
# define FTRACE_ENABLED_INIT 1
#else
# define FTRACE_ENABLED_INIT 0
#endif
int ftrace_enabled = FTRACE_ENABLED_INIT;
static int last_ftrace_enabled = FTRACE_ENABLED_INIT;
int ftrace_enabled;
static int last_ftrace_enabled;
static DEFINE_SPINLOCK(ftrace_lock);
static DEFINE_MUTEX(ftrace_sysctl_lock);
@@ -149,6 +143,14 @@ static int notrace __unregister_ftrace_function(struct ftrace_ops *ops)
#ifdef CONFIG_DYNAMIC_FTRACE
enum {
FTRACE_ENABLE_CALLS = (1 << 0),
FTRACE_DISABLE_CALLS = (1 << 1),
FTRACE_UPDATE_TRACE_FUNC = (1 << 2),
FTRACE_ENABLE_MCOUNT = (1 << 3),
FTRACE_DISABLE_MCOUNT = (1 << 4),
};
static struct hlist_head ftrace_hash[FTRACE_HASHSIZE];
static DEFINE_PER_CPU(int, ftrace_shutdown_disable_cpu);
@@ -199,12 +201,8 @@ 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)
static notrace struct dyn_ftrace *ftrace_alloc_dyn_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;
@@ -215,7 +213,7 @@ static notrace struct dyn_ftrace *ftrace_alloc_shutdown_node(unsigned long ip)
}
static void notrace
ftrace_record_ip(unsigned long ip, unsigned long parent_ip)
ftrace_record_ip(unsigned long ip)
{
struct dyn_ftrace *node;
unsigned long flags;
@@ -223,6 +221,9 @@ ftrace_record_ip(unsigned long ip, unsigned long parent_ip)
int resched;
int atomic;
if (!ftrace_enabled)
return;
resched = need_resched();
preempt_disable_notrace();
@@ -251,11 +252,12 @@ ftrace_record_ip(unsigned long ip, unsigned long parent_ip)
/*
* 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.
* hash and reset here. If it is already converted, skip it.
*/
node = ftrace_alloc_shutdown_node(ip);
if (ftrace_ip_converted(ip))
goto out_unlock;
node = ftrace_alloc_dyn_node(ip);
if (!node)
goto out_unlock;
@@ -277,11 +279,7 @@ ftrace_record_ip(unsigned long ip, unsigned long parent_ip)
preempt_enable_notrace();
}
static struct ftrace_ops ftrace_shutdown_ops __read_mostly =
{
.func = ftrace_record_ip,
};
#define FTRACE_ADDR ((long)(&ftrace_caller))
#define MCOUNT_ADDR ((long)(&mcount))
static void notrace ftrace_replace_code(int saved)
@@ -309,9 +307,9 @@ static void notrace ftrace_replace_code(int saved)
ip = rec->ip;
if (saved)
new = ftrace_call_replace(ip, MCOUNT_ADDR);
new = ftrace_call_replace(ip, FTRACE_ADDR);
else
old = ftrace_call_replace(ip, MCOUNT_ADDR);
old = ftrace_call_replace(ip, FTRACE_ADDR);
failed = ftrace_modify_code(ip, old, new);
if (failed)
@@ -320,16 +318,6 @@ static void notrace ftrace_replace_code(int saved)
}
}
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)
@@ -339,16 +327,8 @@ static notrace void ftrace_shutdown_replenish(void)
ftrace_pages->next = (void *)get_zeroed_page(GFP_KERNEL);
}
static int notrace __ftrace_modify_code(void *data)
{
void (*func)(void) = data;
func();
return 0;
}
static notrace void
ftrace_code_disable(struct dyn_ftrace *rec, unsigned long addr)
ftrace_code_disable(struct dyn_ftrace *rec)
{
unsigned long ip;
unsigned char *nop, *call;
@@ -357,67 +337,113 @@ ftrace_code_disable(struct dyn_ftrace *rec, unsigned long addr)
ip = rec->ip;
nop = ftrace_nop_replace();
call = ftrace_call_replace(ip, addr);
call = ftrace_call_replace(ip, MCOUNT_ADDR);
failed = ftrace_modify_code(ip, call, nop);
if (failed)
rec->flags |= FTRACE_FL_FAILED;
}
static void notrace ftrace_run_startup_code(void)
static int notrace __ftrace_modify_code(void *data)
{
stop_machine_run(__ftrace_modify_code, ftrace_startup_code, NR_CPUS);
unsigned long addr;
int *command = data;
if (*command & FTRACE_ENABLE_CALLS)
ftrace_replace_code(1);
else if (*command & FTRACE_DISABLE_CALLS)
ftrace_replace_code(0);
if (*command & FTRACE_UPDATE_TRACE_FUNC)
ftrace_update_ftrace_func(ftrace_trace_function);
if (*command & FTRACE_ENABLE_MCOUNT) {
addr = (unsigned long)ftrace_record_ip;
ftrace_mcount_set(&addr);
} else if (*command & FTRACE_DISABLE_MCOUNT) {
addr = (unsigned long)ftrace_stub;
ftrace_mcount_set(&addr);
}
return 0;
}
static void notrace ftrace_run_shutdown_code(void)
static void notrace ftrace_run_update_code(int command)
{
stop_machine_run(__ftrace_modify_code, ftrace_shutdown_code, NR_CPUS);
stop_machine_run(__ftrace_modify_code, &command, NR_CPUS);
}
static ftrace_func_t saved_ftrace_func;
static void notrace ftrace_startup(void)
{
int command = 0;
mutex_lock(&ftraced_lock);
ftraced_suspend++;
if (ftraced_suspend != 1)
goto out;
__unregister_ftrace_function(&ftrace_shutdown_ops);
if (ftraced_suspend == 1)
command |= FTRACE_ENABLE_CALLS;
if (ftrace_enabled)
ftrace_run_startup_code();
if (saved_ftrace_func != ftrace_trace_function) {
saved_ftrace_func = ftrace_trace_function;
command |= FTRACE_UPDATE_TRACE_FUNC;
}
if (!command || !ftrace_enabled)
goto out;
ftrace_run_update_code(command);
out:
mutex_unlock(&ftraced_lock);
}
static void notrace ftrace_shutdown(void)
{
int command = 0;
mutex_lock(&ftraced_lock);
ftraced_suspend--;
if (ftraced_suspend)
if (!ftraced_suspend)
command |= FTRACE_DISABLE_CALLS;
if (saved_ftrace_func != ftrace_trace_function) {
saved_ftrace_func = ftrace_trace_function;
command |= FTRACE_UPDATE_TRACE_FUNC;
}
if (!command || !ftrace_enabled)
goto out;
if (ftrace_enabled)
ftrace_run_shutdown_code();
__register_ftrace_function(&ftrace_shutdown_ops);
ftrace_run_update_code(command);
out:
mutex_unlock(&ftraced_lock);
}
static void notrace ftrace_startup_sysctl(void)
{
int command = FTRACE_ENABLE_MCOUNT;
mutex_lock(&ftraced_lock);
/* Force update next time */
saved_ftrace_func = NULL;
/* ftraced_suspend is true if we want ftrace running */
if (ftraced_suspend)
ftrace_run_startup_code();
command |= FTRACE_ENABLE_CALLS;
ftrace_run_update_code(command);
mutex_unlock(&ftraced_lock);
}
static void notrace ftrace_shutdown_sysctl(void)
{
int command = FTRACE_DISABLE_MCOUNT;
mutex_lock(&ftraced_lock);
/* ftraced_suspend is true if ftrace is running */
if (ftraced_suspend)
ftrace_run_shutdown_code();
command |= FTRACE_DISABLE_CALLS;
ftrace_run_update_code(command);
mutex_unlock(&ftraced_lock);
}
@@ -430,11 +456,13 @@ static int notrace __ftrace_update_code(void *ignore)
struct dyn_ftrace *p;
struct hlist_head head;
struct hlist_node *t;
int save_ftrace_enabled;
cycle_t start, stop;
int i;
/* Don't be calling ftrace ops now */
__unregister_ftrace_function(&ftrace_shutdown_ops);
/* Don't be recording funcs now */
save_ftrace_enabled = ftrace_enabled;
ftrace_enabled = 0;
start = now(raw_smp_processor_id());
ftrace_update_cnt = 0;
@@ -449,7 +477,7 @@ 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, MCOUNT_ADDR);
ftrace_code_disable(p);
ftrace_update_cnt++;
}
@@ -459,7 +487,7 @@ static int notrace __ftrace_update_code(void *ignore)
ftrace_update_time = stop - start;
ftrace_update_tot_cnt += ftrace_update_cnt;
__register_ftrace_function(&ftrace_shutdown_ops);
ftrace_enabled = save_ftrace_enabled;
return 0;
}
@@ -515,11 +543,6 @@ 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);
@@ -557,11 +580,19 @@ static int __init ftrace_dyn_table_alloc(void)
return 0;
}
static int __init notrace ftrace_shutdown_init(void)
static int __init notrace ftrace_dynamic_init(void)
{
struct task_struct *p;
unsigned long addr;
int ret;
addr = (unsigned long)ftrace_record_ip;
stop_machine_run(ftrace_dyn_arch_init, &addr, NR_CPUS);
/* ftrace_dyn_arch_init places the return code in addr */
if (addr)
return addr;
ret = ftrace_dyn_table_alloc();
if (ret)
return ret;
@@ -570,12 +601,12 @@ static int __init notrace ftrace_shutdown_init(void)
if (IS_ERR(p))
return -1;
__register_ftrace_function(&ftrace_shutdown_ops);
last_ftrace_enabled = ftrace_enabled = 1;
return 0;
}
core_initcall(ftrace_shutdown_init);
core_initcall(ftrace_dynamic_init);
#else
# define ftrace_startup() do { } while (0)
# define ftrace_shutdown() do { } while (0)
@@ -599,9 +630,8 @@ int register_ftrace_function(struct ftrace_ops *ops)
int ret;
mutex_lock(&ftrace_sysctl_lock);
ftrace_startup();
ret = __register_ftrace_function(ops);
ftrace_startup();
mutex_unlock(&ftrace_sysctl_lock);
return ret;
@@ -619,10 +649,7 @@ int unregister_ftrace_function(struct ftrace_ops *ops)
mutex_lock(&ftrace_sysctl_lock);
ret = __unregister_ftrace_function(ops);
if (ftrace_list == &ftrace_list_end)
ftrace_shutdown();
ftrace_shutdown();
mutex_unlock(&ftrace_sysctl_lock);
return ret;