// 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);

int profile_setup(char *str)
{
        static const char schedstr[] = "schedule";
        static const char kvmstr[] = "kvm";
        const char *select = NULL;
        int par;

        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);

        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;

        return -ENOMEM;
}

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;
        if (pc < prof_len)
                atomic_add(nr_hits, &prof_buffer[pc]);
}

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();

        /* This is the old kernel-only legacy profiling */
        if (!user_mode(regs))
                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>

/*
 * 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_t
read_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;

        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
        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;
        int err = 0;

        if (!prof_on)
                return 0;
        entry = proc_create("profile", S_IWUSR | S_IRUGO,
                            NULL, &profile_proc_ops);
        if (entry)
                proc_set_size(entry, (1 + prof_len) * sizeof(atomic_t));
        return err;
}
subsys_initcall(create_proc_profile);
#endif /* CONFIG_PROC_FS */