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33 * $FreeBSD: src/sys/libkern/mcount.c,v 1.16 1999/12/29 04:54:41 peter Exp $
34 * $DragonFly: src/sys/libkern/mcount.c,v 1.9 2007/01/12 22:12:50 dillon Exp $
37 #include <sys/param.h>
41 #include <sys/systm.h>
44 #include <vm/vm_param.h>
53 * mcount is called on entry to each function compiled with the profiling
54 * switch set. _mcount(), which is declared in a machine-dependent way
55 * with _MCOUNT_DECL, does the actual work and is either inlined into a
56 * C routine or called by an assembly stub. In any case, this magic is
57 * taken care of by the MCOUNT definition in <machine/profile.h>.
59 * _mcount updates data structures that represent traversals of the
60 * program's call graph edges. frompc and selfpc are the return
61 * address and function address that represents the given call graph edge.
63 * Note: the original BSD code used the same variable (frompcindex) for
64 * both frompcindex and frompc. Any reasonable, modern compiler will
65 * perform this optimization.
67 /* _mcount; may be static, inline, etc */
68 _MCOUNT_DECL(uintfptr_t frompc, uintfptr_t selfpc)
75 struct tostruct *top, *prevtop;
83 #ifndef GUPROF /* XXX */
85 * check that we are profiling
86 * and that we aren't recursively invoked.
88 if (p->state != GMON_PROF_ON)
94 p->state = GMON_PROF_BUSY;
96 frompci = frompc - p->lowpc;
100 * When we are called from an exception handler, frompci may be
101 * for a user address. Convert such frompci's to the index of
102 * user() to merge all user counts.
104 * XXX doesn't work properly with vkernel
106 if (frompci >= p->textsize) {
107 if (frompci + p->lowpc
108 >= (uintfptr_t)(VM_MAX_USER_ADDRESS + UPAGES * PAGE_SIZE))
110 frompci = (uintfptr_t)user - p->lowpc;
111 if (frompci >= p->textsize)
117 if (p->state == GMON_PROF_HIRES) {
119 * Count the time since cputime() was previously called
120 * against `frompc'. Compensate for overheads.
122 * cputime() sets its prev_count variable to the count when
123 * it is called. This in effect starts a counter for
124 * the next period of execution (normally from now until
125 * the next call to mcount() or mexitcount()). We set
126 * cputime_bias to compensate for our own overhead.
128 * We use the usual sampling counters since they can be
129 * located efficiently. 4-byte counters are usually
130 * necessary. gprof will add up the scattered counts
131 * just like it does for statistical profiling. All
132 * counts are signed so that underflow in the subtractions
133 * doesn't matter much (negative counts are normally
134 * compensated for by larger counts elsewhere). Underflow
135 * shouldn't occur, but may be caused by slightly wrong
136 * calibrations or from not clearing cputime_bias.
138 delta = cputime() - cputime_bias - p->mcount_pre_overhead;
139 cputime_bias = p->mcount_post_overhead;
140 KCOUNT(p, frompci) += delta;
141 *p->cputime_count += p->cputime_overhead;
142 *p->mcount_count += p->mcount_overhead;
148 * When we are called from an exception handler, frompc is faked
149 * to be for where the exception occurred. We've just solidified
150 * the count for there. Now convert frompci to the index of btrap()
151 * for trap handlers and bintr() for interrupt handlers to make
152 * exceptions appear in the call graph as calls from btrap() and
153 * bintr() instead of calls from all over.
155 if ((uintfptr_t)selfpc >= (uintfptr_t)btrap
156 && (uintfptr_t)selfpc < (uintfptr_t)eintr) {
157 if ((uintfptr_t)selfpc >= (uintfptr_t)bintr)
158 frompci = (uintfptr_t)bintr - p->lowpc;
160 frompci = (uintfptr_t)btrap - p->lowpc;
165 * check that frompc is a reasonable pc value.
166 * for example: signal catchers get called from the stack,
167 * not from text space. too bad.
169 if (frompci >= p->textsize)
172 frompcindex = &p->froms[frompci / (p->hashfraction * sizeof(*p->froms))];
173 toindex = *frompcindex;
176 * first time traversing this arc
178 toindex = ++p->tos[0].link;
179 if (toindex >= p->tolimit)
180 /* halt further profiling */
183 *frompcindex = toindex;
184 top = &p->tos[toindex];
185 top->selfpc = selfpc;
190 top = &p->tos[toindex];
191 if (top->selfpc == selfpc) {
193 * arc at front of chain; usual case.
199 * have to go looking down chain for it.
200 * top points to what we are looking at,
201 * prevtop points to previous top.
202 * we know it is not at the head of the chain.
204 for (; /* goto done */; ) {
205 if (top->link == 0) {
207 * top is end of the chain and none of the chain
208 * had top->selfpc == selfpc.
209 * so we allocate a new tostruct
210 * and link it to the head of the chain.
212 toindex = ++p->tos[0].link;
213 if (toindex >= p->tolimit)
216 top = &p->tos[toindex];
217 top->selfpc = selfpc;
219 top->link = *frompcindex;
220 *frompcindex = toindex;
224 * otherwise, check the next arc on the chain.
227 top = &p->tos[top->link];
228 if (top->selfpc == selfpc) {
231 * increment its count
232 * move it to the head of the chain.
235 toindex = prevtop->link;
236 prevtop->link = top->link;
237 top->link = *frompcindex;
238 *frompcindex = toindex;
247 p->state = GMON_PROF_ON;
251 p->state = GMON_PROF_ERROR;
259 * Actual definition of mcount function. Defined in <machine/profile.h>,
260 * which is included by <sys/gmon.h>.
266 mexitcount(uintfptr_t selfpc)
269 uintfptr_t selfpcdiff;
272 selfpcdiff = selfpc - (uintfptr_t)p->lowpc;
273 if (selfpcdiff < p->textsize) {
277 * Count the time since cputime() was previously called
278 * against `selfpc'. Compensate for overheads.
280 delta = cputime() - cputime_bias - p->mexitcount_pre_overhead;
281 cputime_bias = p->mexitcount_post_overhead;
282 KCOUNT(p, selfpcdiff) += delta;
283 *p->cputime_count += p->cputime_overhead;
284 *p->mexitcount_count += p->mexitcount_overhead;
293 for (i = 0; i < CALIB_SCALE; i++)
307 for (i = 0; i < CALIB_SCALE; i++)