Commit d61f82d0 authored by Steven Rostedt's avatar Steven Rostedt Committed by Thomas Gleixner
Browse files

ftrace: use dynamic patching for updating mcount calls 



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: default avatarSteven Rostedt <srostedt@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 3c1720f0

arch/x86/kernel/entry_32.S

+44 −3
Original line number Diff line number Diff line
@@ -1110,10 +1110,50 @@ ENDPROC(xen_failsafe_callback) 
#endif	/* CONFIG_XEN */



#ifdef CONFIG_FTRACE

#ifdef CONFIG_DYNAMIC_FTRACE



ENTRY(mcount)

	pushl %eax

	pushl %ecx

	pushl %edx

	movl 0xc(%esp), %eax



.globl mcount_call

mcount_call:

	call ftrace_stub



	popl %edx

	popl %ecx

	popl %eax



	ret

END(mcount)



ENTRY(ftrace_caller)

	pushl %eax

	pushl %ecx

	pushl %edx

	movl 0xc(%esp), %eax

	movl 0x4(%ebp), %edx



.globl ftrace_call

ftrace_call:

	call ftrace_stub



	popl %edx

	popl %ecx

	popl %eax



.globl ftrace_stub

ftrace_stub:

	ret

END(ftrace_caller)



#else /* ! CONFIG_DYNAMIC_FTRACE */



ENTRY(mcount)

	cmpl $ftrace_stub, ftrace_trace_function

	jnz trace



.globl ftrace_stub

ftrace_stub:

	ret
@@ -1134,7 +1174,8 @@ trace: 


	jmp ftrace_stub

END(mcount)

#endif

#endif /* CONFIG_DYNAMIC_FTRACE */

#endif /* CONFIG_FTRACE */



.section .rodata,"a"

#include "syscall_table_32.S"

arch/x86/kernel/entry_64.S

+66 −1
Original line number Diff line number Diff line
@@ -55,6 +55,70 @@ 
	.code64



#ifdef CONFIG_FTRACE

#ifdef CONFIG_DYNAMIC_FTRACE

ENTRY(mcount)



	subq $0x38, %rsp

	movq %rax, (%rsp)

	movq %rcx, 8(%rsp)

	movq %rdx, 16(%rsp)

	movq %rsi, 24(%rsp)

	movq %rdi, 32(%rsp)

	movq %r8, 40(%rsp)

	movq %r9, 48(%rsp)



	movq 0x38(%rsp), %rdi



.globl mcount_call

mcount_call:

	call ftrace_stub



	movq 48(%rsp), %r9

	movq 40(%rsp), %r8

	movq 32(%rsp), %rdi

	movq 24(%rsp), %rsi

	movq 16(%rsp), %rdx

	movq 8(%rsp), %rcx

	movq (%rsp), %rax

	addq $0x38, %rsp



	retq

END(mcount)



ENTRY(ftrace_caller)



	/* taken from glibc */

	subq $0x38, %rsp

	movq %rax, (%rsp)

	movq %rcx, 8(%rsp)

	movq %rdx, 16(%rsp)

	movq %rsi, 24(%rsp)

	movq %rdi, 32(%rsp)

	movq %r8, 40(%rsp)

	movq %r9, 48(%rsp)



	movq 0x38(%rsp), %rdi

	movq 8(%rbp), %rsi



.globl ftrace_call

ftrace_call:

	call ftrace_stub



	movq 48(%rsp), %r9

	movq 40(%rsp), %r8

	movq 32(%rsp), %rdi

	movq 24(%rsp), %rsi

	movq 16(%rsp), %rdx

	movq 8(%rsp), %rcx

	movq (%rsp), %rax

	addq $0x38, %rsp



.globl ftrace_stub

ftrace_stub:

	retq

END(ftrace_caller)



#else /* ! CONFIG_DYNAMIC_FTRACE */

ENTRY(mcount)

	cmpq $ftrace_stub, ftrace_trace_function

	jnz trace
@@ -89,7 +153,8 @@ trace: 


	jmp ftrace_stub

END(mcount)

#endif

#endif /* CONFIG_DYNAMIC_FTRACE */

#endif /* CONFIG_FTRACE */



#ifndef CONFIG_PREEMPT

#define retint_kernel retint_restore_args

arch/x86/kernel/ftrace.c

+40 −1
Original line number Diff line number Diff line
@@ -109,10 +109,49 @@ ftrace_modify_code(unsigned long ip, unsigned char *old_code, 
	return faulted;

}



int __init ftrace_dyn_arch_init(void)

notrace int ftrace_update_ftrace_func(ftrace_func_t func)

{

	unsigned long ip = (unsigned long)(&ftrace_call);

	unsigned char old[5], *new;

	int ret;



	ip += CALL_BACK;



	memcpy(old, &ftrace_call, 5);

	new = ftrace_call_replace(ip, (unsigned long)func);

	ret = ftrace_modify_code(ip, old, new);



	return ret;

}



notrace int ftrace_mcount_set(unsigned long *data)

{

	unsigned long ip = (long)(&mcount_call);

	unsigned long *addr = data;

	unsigned char old[5], *new;



	/* ip is at the location, but modify code will subtact this */

	ip += CALL_BACK;



	/*

	 * Replace the mcount stub with a pointer to the

	 * ip recorder function.

	 */

	memcpy(old, &mcount_call, 5);

	new = ftrace_call_replace(ip, *addr);

	*addr = ftrace_modify_code(ip, old, new);



	return 0;

}



int __init ftrace_dyn_arch_init(void *data)

{

	const unsigned char *const *noptable = find_nop_table();



	/* This is running in kstop_machine */



	ftrace_mcount_set(data);



	ftrace_nop = (unsigned long *)noptable[CALL_BACK];



	return 0;

include/linux/ftrace.h

+6 −1
Original line number Diff line number Diff line
@@ -56,9 +56,14 @@ struct dyn_ftrace { 
extern int ftrace_ip_converted(unsigned long ip);

extern unsigned char *ftrace_nop_replace(void);

extern unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr);

extern int ftrace_dyn_arch_init(void);

extern int ftrace_dyn_arch_init(void *data);

extern int ftrace_mcount_set(unsigned long *data);

extern int ftrace_modify_code(unsigned long ip, unsigned char *old_code,

			      unsigned char *new_code);

extern int ftrace_update_ftrace_func(ftrace_func_t func);

extern void ftrace_caller(void);

extern void ftrace_call(void);

extern void mcount_call(void);

#endif



#ifdef CONFIG_FRAME_POINTER

kernel/trace/ftrace.c

+105 −78
Original line number Diff line number Diff line
@@ -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)

	if (ftraced_suspend == 1)

		command |= FTRACE_ENABLE_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;

	__unregister_ftrace_function(&ftrace_shutdown_ops);



	if (ftrace_enabled)

		ftrace_run_startup_code();

	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)

		goto out;

	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 (ftrace_enabled)

		ftrace_run_shutdown_code();

	if (!command || !ftrace_enabled)

		goto out;



	__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();



	mutex_unlock(&ftrace_sysctl_lock);



	return ret;

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