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 + * + * 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 +#include +#include +#include +#include +#include + +#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< +#include +#include +#include +#include +#include #include +#include +#include +#include + +#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; }