The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/amd64/amd64/prof_machdep.c

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    1 /*-
    2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
    3  *
    4  * Copyright (c) 1996 Bruce D. Evans.
    5  * All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 1. Redistributions of source code must retain the above copyright
   11  *    notice, this list of conditions and the following disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  *
   16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   26  * SUCH DAMAGE.
   27  */
   28 
   29 #include <sys/cdefs.h>
   30 __FBSDID("$FreeBSD: head/sys/amd64/amd64/prof_machdep.c 334522 2018-06-02 05:48:44Z bde $");
   31 
   32 #ifdef GUPROF
   33 
   34 #include <sys/param.h>
   35 #include <sys/systm.h>
   36 #include <sys/bus.h>
   37 #include <sys/cpu.h>
   38 #include <sys/eventhandler.h>
   39 #include <sys/gmon.h>
   40 #include <sys/kernel.h>
   41 #include <sys/smp.h>
   42 #include <sys/sysctl.h>
   43 
   44 #include <machine/clock.h>
   45 #include <machine/timerreg.h>
   46 
   47 #define CPUTIME_CLOCK_UNINITIALIZED     0
   48 #define CPUTIME_CLOCK_I8254             1
   49 #define CPUTIME_CLOCK_TSC               2
   50 #define CPUTIME_CLOCK_I8254_SHIFT       7
   51 
   52 int     cputime_bias = 1;       /* initialize for locality of reference */
   53 
   54 static int      cputime_clock = CPUTIME_CLOCK_UNINITIALIZED;
   55 static int      cputime_prof_active;
   56 #endif /* GUPROF */
   57 
   58 #ifdef __GNUCLIKE_ASM
   59 #if defined(SMP) && defined(GUPROF)
   60 #define MPLOCK "                                                \n\
   61         movl    $1,%edx                                         \n\
   62 9:                                                              \n\
   63         xorl    %eax,%eax                                       \n\
   64         lock                                                    \n\
   65         cmpxchgl %edx,mcount_lock                               \n\
   66         jne     9b                                              \n"
   67 #define MPUNLOCK "movl  $0,mcount_lock                          \n"
   68 #else /* !(SMP && GUPROF) */
   69 #define MPLOCK
   70 #define MPUNLOCK
   71 #endif /* SMP && GUPROF */
   72 
   73 __asm("                                                         \n\
   74 GM_STATE        =       0                                       \n\
   75 GMON_PROF_OFF   =       3                                       \n\
   76                                                                 \n\
   77         .text                                                   \n\
   78         .p2align 4,0x90                                         \n\
   79         .globl  __mcount                                        \n\
   80         .type   __mcount,@function                              \n\
   81 __mcount:                                                       \n\
   82         #                                                       \n\
   83         # Check that we are profiling.  Do it early for speed.  \n\
   84         #                                                       \n\
   85         cmpl    $GMON_PROF_OFF,_gmonparam+GM_STATE              \n\
   86         je      .mcount_exit                                    \n\
   87         #                                                       \n\
   88         # __mcount is the same as [.]mcount except the caller   \n\
   89         # hasn't changed the stack except to call here, so the  \n\
   90         # caller's raddr is above our raddr.                    \n\
   91         #                                                       \n\
   92         pushq   %rax                                            \n\
   93         pushq   %rdx                                            \n\
   94         pushq   %rcx                                            \n\
   95         pushq   %rsi                                            \n\
   96         pushq   %rdi                                            \n\
   97         pushq   %r8                                             \n\
   98         pushq   %r9                                             \n\
   99         movq    7*8+8(%rsp),%rdi                                \n\
  100         jmp     .got_frompc                                     \n\
  101                                                                 \n\
  102         .p2align 4,0x90                                         \n\
  103         .globl  .mcount                                         \n\
  104 .mcount:                                                        \n\
  105         cmpl    $GMON_PROF_OFF,_gmonparam+GM_STATE              \n\
  106         je      .mcount_exit                                    \n\
  107         #                                                       \n\
  108         # The caller's stack frame has already been built, so   \n\
  109         # %rbp is the caller's frame pointer.  The caller's     \n\
  110         # raddr is in the caller's frame following the caller's \n\
  111         # caller's frame pointer.                               \n\
  112         #                                                       \n\
  113         pushq   %rax                                            \n\
  114         pushq   %rdx                                            \n\
  115         pushq   %rcx                                            \n\
  116         pushq   %rsi                                            \n\
  117         pushq   %rdi                                            \n\
  118         pushq   %r8                                             \n\
  119         pushq   %r9                                             \n\
  120         movq    8(%rbp),%rdi                                    \n\
  121 .got_frompc:                                                    \n\
  122         #                                                       \n\
  123         # Our raddr is the caller's pc.                         \n\
  124         #                                                       \n\
  125         movq    7*8(%rsp),%rsi                                  \n\
  126                                                                 \n\
  127         pushfq                                                  \n\
  128         cli                                                     \n"
  129         MPLOCK "                                                \n\
  130         call    mcount                                          \n"
  131         MPUNLOCK "                                              \n\
  132         popfq                                                   \n\
  133         popq    %r9                                             \n\
  134         popq    %r8                                             \n\
  135         popq    %rdi                                            \n\
  136         popq    %rsi                                            \n\
  137         popq    %rcx                                            \n\
  138         popq    %rdx                                            \n\
  139         popq    %rax                                            \n\
  140 .mcount_exit:                                                   \n\
  141         ret     $0                                              \n\
  142 ");
  143 #else /* !__GNUCLIKE_ASM */
  144 #error "this file needs to be ported to your compiler"
  145 #endif /* __GNUCLIKE_ASM */
  146 
  147 #ifdef GUPROF
  148 /*
  149  * [.]mexitcount saves the return register(s), loads selfpc and calls
  150  * mexitcount(selfpc) to do the work.  Someday it should be in a machine
  151  * dependent file together with cputime(), __mcount and [.]mcount.  cputime()
  152  * can't just be put in machdep.c because it has to be compiled without -pg.
  153  */
  154 #ifdef __GNUCLIKE_ASM
  155 __asm("                                                         \n\
  156         .text                                                   \n\
  157 #                                                               \n\
  158 # Dummy label to be seen when gprof -u hides [.]mexitcount.     \n\
  159 #                                                               \n\
  160         .p2align 4,0x90                                         \n\
  161         .globl  __mexitcount                                    \n\
  162         .type   __mexitcount,@function                          \n\
  163 __mexitcount:                                                   \n\
  164         nop                                                     \n\
  165                                                                 \n\
  166 GMON_PROF_HIRES =       4                                       \n\
  167                                                                 \n\
  168         .p2align 4,0x90                                         \n\
  169         .globl  .mexitcount                                     \n\
  170 .mexitcount:                                                    \n\
  171         cmpl    $GMON_PROF_HIRES,_gmonparam+GM_STATE            \n\
  172         jne     .mexitcount_exit                                \n\
  173         pushq   %rax                                            \n\
  174         pushq   %rdx                                            \n\
  175         pushq   %rcx                                            \n\
  176         pushq   %rsi                                            \n\
  177         pushq   %rdi                                            \n\
  178         pushq   %r8                                             \n\
  179         pushq   %r9                                             \n\
  180         movq    7*8(%rsp),%rdi                                  \n\
  181         pushfq                                                  \n\
  182         cli                                                     \n"
  183         MPLOCK "                                                \n\
  184         call    mexitcount                                      \n"
  185         MPUNLOCK "                                              \n\
  186         popfq                                                   \n\
  187         popq    %r9                                             \n\
  188         popq    %r8                                             \n\
  189         popq    %rdi                                            \n\
  190         popq    %rsi                                            \n\
  191         popq    %rcx                                            \n\
  192         popq    %rdx                                            \n\
  193         popq    %rax                                            \n\
  194 .mexitcount_exit:                                               \n\
  195         ret     $0                                              \n\
  196 ");
  197 #endif /* __GNUCLIKE_ASM */
  198 
  199 /*
  200  * Return the time elapsed since the last call.  The units are machine-
  201  * dependent.
  202  */
  203 int
  204 cputime()
  205 {
  206         u_int count;
  207         int delta;
  208         u_char high, low;
  209         static u_int prev_count;
  210 
  211         if (cputime_clock == CPUTIME_CLOCK_TSC) {
  212                 /*
  213                  * Scale the TSC a little to make cputime()'s frequency
  214                  * fit in an int, assuming that the TSC frequency fits
  215                  * in a u_int.  Use a fixed scale since dynamic scaling
  216                  * would be slower and we can't really use the low bit
  217                  * of precision.
  218                  */
  219                 count = (u_int)rdtsc() & ~1u;
  220                 delta = (int)(count - prev_count) >> 1;
  221                 prev_count = count;
  222                 return (delta);
  223         }
  224 
  225         /*
  226          * Read the current value of the 8254 timer counter 0.
  227          */
  228         outb(TIMER_MODE, TIMER_SEL0 | TIMER_LATCH);
  229         low = inb(TIMER_CNTR0);
  230         high = inb(TIMER_CNTR0);
  231         count = ((high << 8) | low) << CPUTIME_CLOCK_I8254_SHIFT;
  232 
  233         /*
  234          * The timer counts down from TIMER_CNTR0_MAX to 0 and then resets.
  235          * While profiling is enabled, this routine is called at least twice
  236          * per timer reset (for mcounting and mexitcounting hardclock()),
  237          * so at most one reset has occurred since the last call, and one
  238          * has occurred iff the current count is larger than the previous
  239          * count.  This allows counter underflow to be detected faster
  240          * than in microtime().
  241          */
  242         delta = prev_count - count;
  243         prev_count = count;
  244         if ((int) delta <= 0)
  245                 return (delta + (i8254_max_count << CPUTIME_CLOCK_I8254_SHIFT));
  246         return (delta);
  247 }
  248 
  249 static int
  250 sysctl_machdep_cputime_clock(SYSCTL_HANDLER_ARGS)
  251 {
  252         int clock;
  253         int error;
  254 
  255         clock = cputime_clock;
  256         error = sysctl_handle_opaque(oidp, &clock, sizeof clock, req);
  257         if (error == 0 && req->newptr != NULL) {
  258                 if (clock < 0 || clock > CPUTIME_CLOCK_TSC)
  259                         return (EINVAL);
  260                 cputime_clock = clock;
  261         }
  262         return (error);
  263 }
  264 
  265 SYSCTL_PROC(_machdep, OID_AUTO, cputime_clock, CTLTYPE_INT | CTLFLAG_RW,
  266             0, sizeof(u_int), sysctl_machdep_cputime_clock, "I", "");
  267 
  268 /*
  269  * The start and stop routines need not be here since we turn off profiling
  270  * before calling them.  They are here for convenience.
  271  */
  272 
  273 void
  274 startguprof(gp)
  275         struct gmonparam *gp;
  276 {
  277         uint64_t freq;
  278 
  279         freq = atomic_load_acq_64(&tsc_freq);
  280         if (cputime_clock == CPUTIME_CLOCK_UNINITIALIZED) {
  281                 if (freq != 0 && mp_ncpus == 1)
  282                         cputime_clock = CPUTIME_CLOCK_TSC;
  283                 else
  284                         cputime_clock = CPUTIME_CLOCK_I8254;
  285         }
  286         if (cputime_clock == CPUTIME_CLOCK_TSC) {
  287                 gp->profrate = freq >> 1;
  288                 cputime_prof_active = 1;
  289         } else
  290                 gp->profrate = i8254_freq << CPUTIME_CLOCK_I8254_SHIFT;
  291         cputime_bias = 0;
  292         cputime();
  293 }
  294 
  295 void
  296 stopguprof(gp)
  297         struct gmonparam *gp;
  298 {
  299         if (cputime_clock == CPUTIME_CLOCK_TSC)
  300                 cputime_prof_active = 0;
  301 }
  302 
  303 /* If the cpu frequency changed while profiling, report a warning. */
  304 static void
  305 tsc_freq_changed(void *arg, const struct cf_level *level, int status)
  306 {
  307 
  308         /*
  309          * If there was an error during the transition or
  310          * TSC is P-state invariant, don't do anything.
  311          */
  312         if (status != 0 || tsc_is_invariant)
  313                 return;
  314         if (cputime_prof_active && cputime_clock == CPUTIME_CLOCK_TSC)
  315                 printf("warning: cpu freq changed while profiling active\n");
  316 }
  317 
  318 EVENTHANDLER_DEFINE(cpufreq_post_change, tsc_freq_changed, NULL,
  319     EVENTHANDLER_PRI_ANY);
  320 
  321 #endif /* GUPROF */

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