kernel/profile.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  linux/kernel/profile.c
   4  *  Simple profiling. Manages a direct-mapped profile hit count buffer,
   5  *  with configurable resolution, support for restricting the cpus on
   6  *  which profiling is done, and switching between cpu time and
   7  *  schedule() calls via kernel command line parameters passed at boot.
   8  *
   9  *  Scheduler profiling support, Arjan van de Ven and Ingo Molnar,
  10  *      Red Hat, July 2004
  11  *  Consolidation of architecture support code for profiling,
  12  *      Nadia Yvette Chambers, Oracle, July 2004
  13  *  Amortized hit count accounting via per-cpu open-addressed hashtables
  14  *      to resolve timer interrupt livelocks, Nadia Yvette Chambers,
  15  *      Oracle, 2004
  16  */
  17
  18 #include <linux/export.h>
  19 #include <linux/profile.h>
  20 #include <linux/memblock.h>
  21 #include <linux/notifier.h>
  22 #include <linux/mm.h>
  23 #include <linux/cpumask.h>
  24 #include <linux/cpu.h>
  25 #include <linux/highmem.h>
  26 #include <linux/mutex.h>
  27 #include <linux/slab.h>
  28 #include <linux/vmalloc.h>
  29 #include <linux/sched/stat.h>
  30
  31 #include <asm/sections.h>
  32 #include <asm/irq_regs.h>
  33 #include <asm/ptrace.h>
  34
  35 struct profile_hit {
  36         u32 pc, hits;
  37 };
  38 #define PROFILE_GRPSHIFT        3
  39 #define PROFILE_GRPSZ           (1 << PROFILE_GRPSHIFT)
  40 #define NR_PROFILE_HIT          (PAGE_SIZE/sizeof(struct profile_hit))
  41 #define NR_PROFILE_GRP          (NR_PROFILE_HIT/PROFILE_GRPSZ)
  42
  43 static atomic_t *prof_buffer;
  44 static unsigned long prof_len;
  45 static unsigned short int prof_shift;
  46
  47 int prof_on __read_mostly;
  48 EXPORT_SYMBOL_GPL(prof_on);
  49
  50 int profile_setup(char *str)
  51 {
  52         static const char schedstr[] = "schedule";
  53         static const char kvmstr[] = "kvm";
  54         const char *select = NULL;
  55         int par;
  56
  57         if (!strncmp(str, schedstr, strlen(schedstr))) {
  58                 prof_on = SCHED_PROFILING;
  59                 select = schedstr;
  60         } else if (!strncmp(str, kvmstr, strlen(kvmstr))) {
  61                 prof_on = KVM_PROFILING;
  62                 select = kvmstr;
  63         } else if (get_option(&str, &par)) {
  64                 prof_shift = clamp(par, 0, BITS_PER_LONG - 1);
  65                 prof_on = CPU_PROFILING;
  66                 pr_info("kernel profiling enabled (shift: %u)\n",
  67                         prof_shift);
  68         }
  69
  70         if (select) {
  71                 if (str[strlen(select)] == ',')
  72                         str += strlen(select) + 1;
  73                 if (get_option(&str, &par))
  74                         prof_shift = clamp(par, 0, BITS_PER_LONG - 1);
  75                 pr_info("kernel %s profiling enabled (shift: %u)\n",
  76                         select, prof_shift);
  77         }
  78
  79         return 1;
  80 }
  81 __setup("profile=", profile_setup);
  82
  83
  84 int __ref profile_init(void)
  85 {
  86         int buffer_bytes;
  87         if (!prof_on)
  88                 return 0;
  89
  90         /* only text is profiled */
  91         prof_len = (_etext - _stext) >> prof_shift;
  92
  93         if (!prof_len) {
  94                 pr_warn("profiling shift: %u too large\n", prof_shift);
  95                 prof_on = 0;
  96                 return -EINVAL;
  97         }
  98
  99         buffer_bytes = prof_len*sizeof(atomic_t);
 100
 101         prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL|__GFP_NOWARN);
 102         if (prof_buffer)
 103                 return 0;
 104
 105         prof_buffer = alloc_pages_exact(buffer_bytes,
 106                                         GFP_KERNEL|__GFP_ZERO|__GFP_NOWARN);
 107         if (prof_buffer)
 108                 return 0;
 109
 110         prof_buffer = vzalloc(buffer_bytes);
 111         if (prof_buffer)
 112                 return 0;
 113
 114         return -ENOMEM;
 115 }
 116
 117 static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
 118 {
 119         unsigned long pc;
 120         pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
 121         if (pc < prof_len)
 122                 atomic_add(nr_hits, &prof_buffer[pc]);
 123 }
 124
 125 void profile_hits(int type, void *__pc, unsigned int nr_hits)
 126 {
 127         if (prof_on != type || !prof_buffer)
 128                 return;
 129         do_profile_hits(type, __pc, nr_hits);
 130 }
 131 EXPORT_SYMBOL_GPL(profile_hits);
 132
 133 void profile_tick(int type)
 134 {
 135         struct pt_regs *regs = get_irq_regs();
 136
 137         /* This is the old kernel-only legacy profiling */
 138         if (!user_mode(regs))
 139                 profile_hit(type, (void *)profile_pc(regs));
 140 }
 141
 142 #ifdef CONFIG_PROC_FS
 143 #include <linux/proc_fs.h>
 144 #include <linux/seq_file.h>
 145 #include <linux/uaccess.h>
 146
 147 /*
 148  * This function accesses profiling information. The returned data is
 149  * binary: the sampling step and the actual contents of the profile
 150  * buffer. Use of the program readprofile is recommended in order to
 151  * get meaningful info out of these data.
 152  */
 153 static ssize_t
 154 read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 155 {
 156         unsigned long p = *ppos;
 157         ssize_t read;
 158         char *pnt;
 159         unsigned long sample_step = 1UL << prof_shift;
 160
 161         if (p >= (prof_len+1)*sizeof(unsigned int))
 162                 return 0;
 163         if (count > (prof_len+1)*sizeof(unsigned int) - p)
 164                 count = (prof_len+1)*sizeof(unsigned int) - p;
 165         read = 0;
 166
 167         while (p < sizeof(unsigned int) && count > 0) {
 168                 if (put_user(*((char *)(&sample_step)+p), buf))
 169                         return -EFAULT;
 170                 buf++; p++; count--; read++;
 171         }
 172         pnt = (char *)prof_buffer + p - sizeof(atomic_t);
 173         if (copy_to_user(buf, (void *)pnt, count))
 174                 return -EFAULT;
 175         read += count;
 176         *ppos += read;
 177         return read;
 178 }
 179
 180 /* default is to not implement this call */
 181 int __weak setup_profiling_timer(unsigned mult)
 182 {
 183         return -EINVAL;
 184 }
 185
 186 /*
 187  * Writing to /proc/profile resets the counters
 188  *
 189  * Writing a 'profiling multiplier' value into it also re-sets the profiling
 190  * interrupt frequency, on architectures that support this.
 191  */
 192 static ssize_t write_profile(struct file *file, const char __user *buf,
 193                              size_t count, loff_t *ppos)
 194 {
 195 #ifdef CONFIG_SMP
 196         if (count == sizeof(int)) {
 197                 unsigned int multiplier;
 198
 199                 if (copy_from_user(&multiplier, buf, sizeof(int)))
 200                         return -EFAULT;
 201
 202                 if (setup_profiling_timer(multiplier))
 203                         return -EINVAL;
 204         }
 205 #endif
 206         memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
 207         return count;
 208 }
 209
 210 static const struct proc_ops profile_proc_ops = {
 211         .proc_read      = read_profile,
 212         .proc_write     = write_profile,
 213         .proc_lseek     = default_llseek,
 214 };
 215
 216 int __ref create_proc_profile(void)
 217 {
 218         struct proc_dir_entry *entry;
 219         int err = 0;
 220
 221         if (!prof_on)
 222                 return 0;
 223         entry = proc_create("profile", S_IWUSR | S_IRUGO,
 224                             NULL, &profile_proc_ops);
 225         if (entry)
 226                 proc_set_size(entry, (1 + prof_len) * sizeof(atomic_t));
 227         return err;
 228 }
 229 subsys_initcall(create_proc_profile);
 230 #endif /* CONFIG_PROC_FS */