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34 #if !defined(lint) && !defined(_KERNEL) && defined(LIBC_SCCS)
36 static char sccsid[] = "@(#)mcount.c 8.1 (Berkeley) 6/4/93";
38 static const char rcsid[] =
39 "$FreeBSD: src/lib/libc/gmon/mcount.c,v 1.17 1999/12/29 05:04:13 peter Exp $";
42 #include <sys/param.h>
45 #include <sys/systm.h>
47 #include <vm/vm_param.h>
49 void bintr __P((void));
50 void btrap __P((void));
51 void eintr __P((void));
52 void user __P((void));
56 * mcount is called on entry to each function compiled with the profiling
57 * switch set. _mcount(), which is declared in a machine-dependent way
58 * with _MCOUNT_DECL, does the actual work and is either inlined into a
59 * C routine or called by an assembly stub. In any case, this magic is
60 * taken care of by the MCOUNT definition in <machine/profile.h>.
62 * _mcount updates data structures that represent traversals of the
63 * program's call graph edges. frompc and selfpc are the return
64 * address and function address that represents the given call graph edge.
66 * Note: the original BSD code used the same variable (frompcindex) for
67 * both frompcindex and frompc. Any reasonable, modern compiler will
68 * perform this optimization.
70 _MCOUNT_DECL(frompc, selfpc) /* _mcount; may be static, inline, etc */
71 register uintfptr_t frompc, selfpc;
76 register fptrdiff_t frompci;
77 register u_short *frompcindex;
78 register struct tostruct *top, *prevtop;
79 register struct gmonparam *p;
80 register long toindex;
86 #ifndef GUPROF /* XXX */
88 * check that we are profiling
89 * and that we aren't recursively invoked.
91 if (p->state != GMON_PROF_ON)
97 p->state = GMON_PROF_BUSY;
99 frompci = frompc - p->lowpc;
103 * When we are called from an exception handler, frompci may be
104 * for a user address. Convert such frompci's to the index of
105 * user() to merge all user counts.
107 if (frompci >= p->textsize) {
108 if (frompci + p->lowpc
109 >= (uintfptr_t)(VM_MAXUSER_ADDRESS + UPAGES * PAGE_SIZE))
111 frompci = (uintfptr_t)user - p->lowpc;
112 if (frompci >= p->textsize)
118 if (p->state != GMON_PROF_HIRES)
119 goto skip_guprof_stuff;
121 * Look at the clock and add the count of clock cycles since the
122 * clock was last looked at to a counter for frompc. This
123 * solidifies the count for the function containing frompc and
124 * effectively starts another clock for the current function.
125 * The count for the new clock will be solidified when another
126 * function call is made or the function returns.
128 * We use the usual sampling counters since they can be located
129 * efficiently. 4-byte counters are usually necessary.
131 * There are many complications for subtracting the profiling
132 * overheads from the counts for normal functions and adding
133 * them to the counts for mcount(), mexitcount() and cputime().
134 * We attempt to handle fractional cycles, but the overheads
135 * are usually underestimated because they are calibrated for
136 * a simpler than usual setup.
138 delta = cputime() - p->mcount_overhead;
139 p->cputime_overhead_resid += p->cputime_overhead_frac;
140 p->mcount_overhead_resid += p->mcount_overhead_frac;
142 *p->mcount_count += delta + p->mcount_overhead
143 - p->cputime_overhead;
144 else if (delta != 0) {
145 if (p->cputime_overhead_resid >= CALIB_SCALE) {
146 p->cputime_overhead_resid -= CALIB_SCALE;
151 if (p->mcount_overhead_resid >= CALIB_SCALE) {
152 p->mcount_overhead_resid -= CALIB_SCALE;
156 KCOUNT(p, frompci) += delta;
158 *p->mcount_count += p->mcount_overhead_sub;
160 *p->cputime_count += p->cputime_overhead;
166 * When we are called from an exception handler, frompc is faked
167 * to be for where the exception occurred. We've just solidified
168 * the count for there. Now convert frompci to the index of btrap()
169 * for trap handlers and bintr() for interrupt handlers to make
170 * exceptions appear in the call graph as calls from btrap() and
171 * bintr() instead of calls from all over.
173 if ((uintfptr_t)selfpc >= (uintfptr_t)btrap
174 && (uintfptr_t)selfpc < (uintfptr_t)eintr) {
175 if ((uintfptr_t)selfpc >= (uintfptr_t)bintr)
176 frompci = (uintfptr_t)bintr - p->lowpc;
178 frompci = (uintfptr_t)btrap - p->lowpc;
183 * check that frompc is a reasonable pc value.
184 * for example: signal catchers get called from the stack,
185 * not from text space. too bad.
187 if (frompci >= p->textsize)
190 frompcindex = &p->froms[frompci / (p->hashfraction * sizeof(*p->froms))];
191 toindex = *frompcindex;
194 * first time traversing this arc
196 toindex = ++p->tos[0].link;
197 if (toindex >= p->tolimit)
198 /* halt further profiling */
201 *frompcindex = toindex;
202 top = &p->tos[toindex];
203 top->selfpc = selfpc;
208 top = &p->tos[toindex];
209 if (top->selfpc == selfpc) {
211 * arc at front of chain; usual case.
217 * have to go looking down chain for it.
218 * top points to what we are looking at,
219 * prevtop points to previous top.
220 * we know it is not at the head of the chain.
222 for (; /* goto done */; ) {
223 if (top->link == 0) {
225 * top is end of the chain and none of the chain
226 * had top->selfpc == selfpc.
227 * so we allocate a new tostruct
228 * and link it to the head of the chain.
230 toindex = ++p->tos[0].link;
231 if (toindex >= p->tolimit)
234 top = &p->tos[toindex];
235 top->selfpc = selfpc;
237 top->link = *frompcindex;
238 *frompcindex = toindex;
242 * otherwise, check the next arc on the chain.
245 top = &p->tos[top->link];
246 if (top->selfpc == selfpc) {
249 * increment its count
250 * move it to the head of the chain.
253 toindex = prevtop->link;
254 prevtop->link = top->link;
255 top->link = *frompcindex;
256 *frompcindex = toindex;
265 p->state = GMON_PROF_ON;
269 p->state = GMON_PROF_ERROR;
277 * Actual definition of mcount function. Defined in <machine/profile.h>,
278 * which is included by <sys/gmon.h>.
288 uintfptr_t selfpcdiff;
291 selfpcdiff = selfpc - (uintfptr_t)p->lowpc;
292 if (selfpcdiff < p->textsize) {
296 * Solidify the count for the current function.
298 delta = cputime() - p->mexitcount_overhead;
299 p->cputime_overhead_resid += p->cputime_overhead_frac;
300 p->mexitcount_overhead_resid += p->mexitcount_overhead_frac;
302 *p->mexitcount_count += delta + p->mexitcount_overhead
303 - p->cputime_overhead;
304 else if (delta != 0) {
305 if (p->cputime_overhead_resid >= CALIB_SCALE) {
306 p->cputime_overhead_resid -= CALIB_SCALE;
311 if (p->mexitcount_overhead_resid
313 p->mexitcount_overhead_resid
315 ++*p->mexitcount_count;
318 KCOUNT(p, selfpcdiff) += delta;
320 *p->mexitcount_count += p->mexitcount_overhead_sub;
322 *p->cputime_count += p->cputime_overhead;