// SPDX-License-Identifier: GPL-2.0-only/* *  linux/kernel/profile.c *  Simple profiling. Manages a direct-mapped profile hit count buffer, *  with configurable resolution, support for restricting the cpus on *  which profiling is done, and switching between cpu time and *  schedule() calls via kernel command line parameters passed at boot. * *  Scheduler profiling support, Arjan van de Ven and Ingo Molnar, *	Red Hat, July 2004 *  Consolidation of architecture support code for profiling, *	Nadia Yvette Chambers, Oracle, July 2004 *  Amortized hit count accounting via per-cpu open-addressed hashtables *	to resolve timer interrupt livelocks, Nadia Yvette Chambers, *	Oracle, 2004 */ #include <linux/export.h>#include <linux/profile.h>#include <linux/memblock.h>#include <linux/notifier.h>#include <linux/mm.h>#include <linux/cpumask.h>#include <linux/cpu.h>#include <linux/highmem.h>#include <linux/mutex.h>#include <linux/slab.h>#include <linux/vmalloc.h>#include <linux/sched/stat.h> #include <asm/sections.h>#include <asm/irq_regs.h>#include <asm/ptrace.h> struct profile_hit {	u32 pc, hits;};#define PROFILE_GRPSHIFT	3#define PROFILE_GRPSZ		(1 << PROFILE_GRPSHIFT)#define NR_PROFILE_HIT		(PAGE_SIZE/sizeof(struct profile_hit))#define NR_PROFILE_GRP		(NR_PROFILE_HIT/PROFILE_GRPSZ) static atomic_t *prof_buffer;static unsigned long prof_len;static unsigned short int prof_shift; int prof_on __read_mostly;EXPORT_SYMBOL_GPL(prof_on); static cpumask_var_t prof_cpu_mask;#if defined(CONFIG_SMP) && defined(CONFIG_PROC_FS)static DEFINE_PER_CPU(struct profile_hit *[2], cpu_profile_hits);static DEFINE_PER_CPU(int, cpu_profile_flip);static DEFINE_MUTEX(profile_flip_mutex);#endif /* CONFIG_SMP */ int profile_setup(char *str){	static const char schedstr[] = "schedule";	static const char sleepstr[] = "sleep";	static const char kvmstr[] = "kvm";	const char *select = NULL;	int par; 	if (!strncmp(str, sleepstr, strlen(sleepstr))) {#ifdef CONFIG_SCHEDSTATS		force_schedstat_enabled();		prof_on = SLEEP_PROFILING;		select = sleepstr;#else		pr_warn("kernel sleep profiling requires CONFIG_SCHEDSTATS\n");#endif /* CONFIG_SCHEDSTATS */	} else if (!strncmp(str, schedstr, strlen(schedstr))) {		prof_on = SCHED_PROFILING;		select = schedstr;	} else if (!strncmp(str, kvmstr, strlen(kvmstr))) {		prof_on = KVM_PROFILING;		select = kvmstr;	} else if (get_option(&str, &par)) {		prof_shift = clamp(par, 0, BITS_PER_LONG - 1);		prof_on = CPU_PROFILING;		pr_info("kernel profiling enabled (shift: %u)\n",			prof_shift);	} 	if (select) {		if (str[strlen(select)] == ',')			str += strlen(select) + 1;		if (get_option(&str, &par))			prof_shift = clamp(par, 0, BITS_PER_LONG - 1);		pr_info("kernel %s profiling enabled (shift: %u)\n",			select, prof_shift);	} 	return 1;}__setup("profile=", profile_setup);  int __ref profile_init(void){	int buffer_bytes;	if (!prof_on)		return 0; 	/* only text is profiled */	prof_len = (_etext - _stext) >> prof_shift; 	if (!prof_len) {		pr_warn("profiling shift: %u too large\n", prof_shift);		prof_on = 0;		return -EINVAL;	} 	buffer_bytes = prof_len*sizeof(atomic_t); 	if (!alloc_cpumask_var(&prof_cpu_mask, GFP_KERNEL))		return -ENOMEM; 	cpumask_copy(prof_cpu_mask, cpu_possible_mask); 	prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL|__GFP_NOWARN);	if (prof_buffer)		return 0; 	prof_buffer = alloc_pages_exact(buffer_bytes,					GFP_KERNEL|__GFP_ZERO|__GFP_NOWARN);	if (prof_buffer)		return 0; 	prof_buffer = vzalloc(buffer_bytes);	if (prof_buffer)		return 0; 	free_cpumask_var(prof_cpu_mask);	return -ENOMEM;} #if defined(CONFIG_SMP) && defined(CONFIG_PROC_FS)/* * Each cpu has a pair of open-addressed hashtables for pending * profile hits. read_profile() IPI's all cpus to request them * to flip buffers and flushes their contents to prof_buffer itself. * Flip requests are serialized by the profile_flip_mutex. The sole * use of having a second hashtable is for avoiding cacheline * contention that would otherwise happen during flushes of pending * profile hits required for the accuracy of reported profile hits * and so resurrect the interrupt livelock issue. * * The open-addressed hashtables are indexed by profile buffer slot * and hold the number of pending hits to that profile buffer slot on * a cpu in an entry. When the hashtable overflows, all pending hits * are accounted to their corresponding profile buffer slots with * atomic_add() and the hashtable emptied. As numerous pending hits * may be accounted to a profile buffer slot in a hashtable entry, * this amortizes a number of atomic profile buffer increments likely * to be far larger than the number of entries in the hashtable, * particularly given that the number of distinct profile buffer * positions to which hits are accounted during short intervals (e.g. * several seconds) is usually very small. Exclusion from buffer * flipping is provided by interrupt disablement (note that for * SCHED_PROFILING or SLEEP_PROFILING profile_hit() may be called from * process context). * The hash function is meant to be lightweight as opposed to strong, * and was vaguely inspired by ppc64 firmware-supported inverted * pagetable hash functions, but uses a full hashtable full of finite * collision chains, not just pairs of them. * * -- nyc */static void __profile_flip_buffers(void *unused){	int cpu = smp_processor_id(); 	per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu);} static void profile_flip_buffers(void){	int i, j, cpu; 	mutex_lock(&profile_flip_mutex);	j = per_cpu(cpu_profile_flip, get_cpu());	put_cpu();	on_each_cpu(__profile_flip_buffers, NULL, 1);	for_each_online_cpu(cpu) {		struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j];		for (i = 0; i < NR_PROFILE_HIT; ++i) {			if (!hits[i].hits) {				if (hits[i].pc)					hits[i].pc = 0;				continue;			}			atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);			hits[i].hits = hits[i].pc = 0;		}	}	mutex_unlock(&profile_flip_mutex);} static void profile_discard_flip_buffers(void){	int i, cpu; 	mutex_lock(&profile_flip_mutex);	i = per_cpu(cpu_profile_flip, get_cpu());	put_cpu();	on_each_cpu(__profile_flip_buffers, NULL, 1);	for_each_online_cpu(cpu) {		struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i];		memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit));	}	mutex_unlock(&profile_flip_mutex);} static void do_profile_hits(int type, void *__pc, unsigned int nr_hits){	unsigned long primary, secondary, flags, pc = (unsigned long)__pc;	int i, j, cpu;	struct profile_hit *hits; 	pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1);	i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;	secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;	cpu = get_cpu();	hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)];	if (!hits) {		put_cpu();		return;	}	/*	 * We buffer the global profiler buffer into a per-CPU	 * queue and thus reduce the number of global (and possibly	 * NUMA-alien) accesses. The write-queue is self-coalescing:	 */	local_irq_save(flags);	do {		for (j = 0; j < PROFILE_GRPSZ; ++j) {			if (hits[i + j].pc == pc) {				hits[i + j].hits += nr_hits;				goto out;			} else if (!hits[i + j].hits) {				hits[i + j].pc = pc;				hits[i + j].hits = nr_hits;				goto out;			}		}		i = (i + secondary) & (NR_PROFILE_HIT - 1);	} while (i != primary); 	/*	 * Add the current hit(s) and flush the write-queue out	 * to the global buffer:	 */	atomic_add(nr_hits, &prof_buffer[pc]);	for (i = 0; i < NR_PROFILE_HIT; ++i) {		atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);		hits[i].pc = hits[i].hits = 0;	}out:	local_irq_restore(flags);	put_cpu();} static int profile_dead_cpu(unsigned int cpu){	struct page *page;	int i; 	if (cpumask_available(prof_cpu_mask))		cpumask_clear_cpu(cpu, prof_cpu_mask); 	for (i = 0; i < 2; i++) {		if (per_cpu(cpu_profile_hits, cpu)[i]) {			page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[i]);			per_cpu(cpu_profile_hits, cpu)[i] = NULL;			__free_page(page);		}	}	return 0;} static int profile_prepare_cpu(unsigned int cpu){	int i, node = cpu_to_mem(cpu);	struct page *page; 	per_cpu(cpu_profile_flip, cpu) = 0; 	for (i = 0; i < 2; i++) {		if (per_cpu(cpu_profile_hits, cpu)[i])			continue; 		page = __alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);		if (!page) {			profile_dead_cpu(cpu);			return -ENOMEM;		}		per_cpu(cpu_profile_hits, cpu)[i] = page_address(page); 	}	return 0;} static int profile_online_cpu(unsigned int cpu){	if (cpumask_available(prof_cpu_mask))		cpumask_set_cpu(cpu, prof_cpu_mask); 	return 0;} #else /* !CONFIG_SMP */#define profile_flip_buffers()		do { } while (0)#define profile_discard_flip_buffers()	do { } while (0) static void do_profile_hits(int type, void *__pc, unsigned int nr_hits){	unsigned long pc;	pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;	atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]);}#endif /* !CONFIG_SMP */ void profile_hits(int type, void *__pc, unsigned int nr_hits){	if (prof_on != type || !prof_buffer)		return;	do_profile_hits(type, __pc, nr_hits);}EXPORT_SYMBOL_GPL(profile_hits); void profile_tick(int type){	struct pt_regs *regs = get_irq_regs(); 	if (!user_mode(regs) && cpumask_available(prof_cpu_mask) &&	    cpumask_test_cpu(smp_processor_id(), prof_cpu_mask))		profile_hit(type, (void *)profile_pc(regs));} #ifdef CONFIG_PROC_FS#include <linux/proc_fs.h>#include <linux/seq_file.h>#include <linux/uaccess.h> static int prof_cpu_mask_proc_show(struct seq_file *m, void *v){	seq_printf(m, "%*pb\n", cpumask_pr_args(prof_cpu_mask));	return 0;} static int prof_cpu_mask_proc_open(struct inode *inode, struct file *file){	return single_open(file, prof_cpu_mask_proc_show, NULL);} static ssize_t prof_cpu_mask_proc_write(struct file *file,	const char __user *buffer, size_t count, loff_t *pos){	cpumask_var_t new_value;	int err; 	if (!zalloc_cpumask_var(&new_value, GFP_KERNEL))		return -ENOMEM; 	err = cpumask_parse_user(buffer, count, new_value);	if (!err) {		cpumask_copy(prof_cpu_mask, new_value);		err = count;	}	free_cpumask_var(new_value);	return err;} static const struct proc_ops prof_cpu_mask_proc_ops = {	.proc_open	= prof_cpu_mask_proc_open,	.proc_read	= seq_read,	.proc_lseek	= seq_lseek,	.proc_release	= single_release,	.proc_write	= prof_cpu_mask_proc_write,}; void create_prof_cpu_mask(void){	/* create /proc/irq/prof_cpu_mask */	proc_create("irq/prof_cpu_mask", 0600, NULL, &prof_cpu_mask_proc_ops);} /* * This function accesses profiling information. The returned data is * binary: the sampling step and the actual contents of the profile * buffer. Use of the program readprofile is recommended in order to * get meaningful info out of these data. */static ssize_tread_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos){	unsigned long p = *ppos;	ssize_t read;	char *pnt;	unsigned long sample_step = 1UL << prof_shift; 	profile_flip_buffers();	if (p >= (prof_len+1)*sizeof(unsigned int))		return 0;	if (count > (prof_len+1)*sizeof(unsigned int) - p)		count = (prof_len+1)*sizeof(unsigned int) - p;	read = 0; 	while (p < sizeof(unsigned int) && count > 0) {		if (put_user(*((char *)(&sample_step)+p), buf))			return -EFAULT;		buf++; p++; count--; read++;	}	pnt = (char *)prof_buffer + p - sizeof(atomic_t);	if (copy_to_user(buf, (void *)pnt, count))		return -EFAULT;	read += count;	*ppos += read;	return read;} /* default is to not implement this call */int __weak setup_profiling_timer(unsigned mult){	return -EINVAL;} /* * Writing to /proc/profile resets the counters * * Writing a 'profiling multiplier' value into it also re-sets the profiling * interrupt frequency, on architectures that support this. */static ssize_t write_profile(struct file *file, const char __user *buf,			     size_t count, loff_t *ppos){#ifdef CONFIG_SMP	if (count == sizeof(int)) {		unsigned int multiplier; 		if (copy_from_user(&multiplier, buf, sizeof(int)))			return -EFAULT; 		if (setup_profiling_timer(multiplier))			return -EINVAL;	}#endif	profile_discard_flip_buffers();	memset(prof_buffer, 0, prof_len * sizeof(atomic_t));	return count;} static const struct proc_ops profile_proc_ops = {	.proc_read	= read_profile,	.proc_write	= write_profile,	.proc_lseek	= default_llseek,}; int __ref create_proc_profile(void){	struct proc_dir_entry *entry;#ifdef CONFIG_SMP	enum cpuhp_state online_state;#endif 	int err = 0; 	if (!prof_on)		return 0;#ifdef CONFIG_SMP	err = cpuhp_setup_state(CPUHP_PROFILE_PREPARE, "PROFILE_PREPARE",				profile_prepare_cpu, profile_dead_cpu);	if (err)		return err; 	err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "AP_PROFILE_ONLINE",				profile_online_cpu, NULL);	if (err < 0)		goto err_state_prep;	online_state = err;	err = 0;#endif	entry = proc_create("profile", S_IWUSR | S_IRUGO,			    NULL, &profile_proc_ops);	if (!entry)		goto err_state_onl;	proc_set_size(entry, (1 + prof_len) * sizeof(atomic_t)); 	return err;err_state_onl:#ifdef CONFIG_SMP	cpuhp_remove_state(online_state);err_state_prep:	cpuhp_remove_state(CPUHP_PROFILE_PREPARE);#endif	return err;}subsys_initcall(create_proc_profile);

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