Implemented non-statistical kernel profiling. This is based on

looking at a high resolution clock for each of the following events:
function call, function return, interrupt entry, interrupt exit,
and interesting branches.  The differences between the times of
these events are added at appropriate places in a ordinary histogram
(as if very fast statistical profiling sampled the pc at those
places) so that ordinary gprof can be used to analyze the times.

gmon.h:
Histogram counters need to be 4 bytes for microsecond resolutions.
They will need to be larger for the 586 clock.
The comments were vax-centric and wrong even on vaxes.  Does anyone
disagree?

gprof4.c:
The standard gprof should support counters of all integral sizes
and the size of the counter should be in the gmon header.  This
hack will do until then.  (Use gprof4 -u to examine the results
of non-statistical profiling.)

config/*:
Non-statistical profiling is configured with `config -pp'.
`config -p' still gives ordinary profiling.

kgmon/*:
Non-statistical profiling is enabled with `kgmon -B'.  `kgmon -b'
still enables ordinary profiling (and distables non-statistical
profiling) if non-statistical profiling is configured.

1 files changed, 153 insertions, 0 deletions

diff --git a/sys/i386/isa/prof_machdep.c b/sys/i386/isa/prof_machdep.c
new file mode 100644
index 0000000..2aa6787
--- /dev/null
+++ b/sys/i386/isa/prof_machdep.c
@@ -0,0 +1,153 @@
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <machine/clock.h>
+#include <i386/isa/isa.h>
+#include <i386/isa/timerreg.h>
+
+#ifdef GUPROF
+extern u_int	cputime __P((void));
+#endif
+
+#ifdef __GNUC__
+asm("
+GM_STATE	=	0
+GMON_PROF_OFF	=	3
+
+	.text
+	.align	4,0x90
+	.globl	__mcount
+__mcount:
+	#
+	# Check that we are profiling.  Do it early for speed.
+	#
+	cmpl	$GMON_PROF_OFF,__gmonparam+GM_STATE
+ 	je	Lmcount_exit
+ 	#
+ 	# __mcount is the same as mcount except the caller hasn't changed
+ 	# the stack except to call here, so the caller's raddr is above
+ 	# our raddr.
+ 	#
+ 	movl	4(%esp),%edx
+ 	jmp	Lgot_frompc
+ 
+ 	.align	4,0x90
+ 	.globl	mcount
+mcount:
+	cmpl	$GMON_PROF_OFF,__gmonparam+GM_STATE
+	je	Lmcount_exit
+	#
+	# The caller's stack frame has already been built, so %ebp is
+	# the caller's frame pointer.  The caller's raddr is in the
+	# caller's frame following the caller's caller's frame pointer.
+	#
+	movl	4(%ebp),%edx
+Lgot_frompc:
+	#
+	# Our raddr is the caller's pc.
+	#
+	movl	(%esp),%eax
+
+	pushf
+	pushl	%eax
+	pushl	%edx
+	cli
+	call	_mcount
+	addl	$8,%esp
+	popf
+Lmcount_exit:
+	ret
+");
+#else /* !__GNUC__ */
+#error
+#endif /* __GNUC__ */
+
+#ifdef GUPROF
+/*
+ * mexitcount saves the return register(s), loads selfpc and calls
+ * mexitcount(selfpc) to do the work.  Someday it should be in a machine
+ * dependent file together with cputime(), __mcount and mcount.  cputime()
+ * can't just be put in machdep.c because it has to be compiled without -pg.
+ */
+#ifdef __GNUC__
+asm("
+	.text
+#
+# Dummy label to be seen when gprof -u hides mexitcount.
+#
+	.align	4,0x90
+	.globl	__mexitcount
+__mexitcount:
+	nop
+
+GMON_PROF_HIRES	=	4
+
+	.align	4,0x90
+	.globl	mexitcount
+mexitcount:
+	cmpl	$GMON_PROF_HIRES,__gmonparam+GM_STATE
+	jne	Lmexitcount_exit
+	pushl	%edx
+	pushl	%eax
+	movl	8(%esp),%eax
+	pushf
+	pushl	%eax
+	cli
+	call	_mexitcount
+	addl	$4,%esp
+	popf
+	popl	%eax
+	popl	%edx
+Lmexitcount_exit:
+	ret
+");
+#else /* !__GNUC__ */
+#error
+#endif /* __GNUC__ */
+
+/*
+ * Return the time elapsed since the last call.  The units are machine-
+ * dependent.
+ */
+u_int
+cputime()
+{
+	u_int count;
+	u_int delta;
+	u_char low;
+	static u_int prev_count;
+
+	/*
+	 * Read the current value of the 8254 timer counter 0.
+	 */
+	outb(TIMER_MODE, TIMER_SEL0 | TIMER_LATCH);
+	low = inb(TIMER_CNTR0);
+	count = low | (inb(TIMER_CNTR0) << 8);
+
+	/*
+	 * The timer counts down from TIMER_CNTR0_MAX to 0 and then resets.
+	 * While profiling is enabled, this routine is called at least twice
+	 * per timer reset (for mcounting and mexitcounting hardclock()),
+	 * so at most one reset has occurred since the last call, and one
+	 * has occurred iff the current count is larger than the previous
+	 * count.  This allows counter underflow to be detected faster
+	 * than in microtime().
+	 */
+	delta = prev_count - count;
+	prev_count = count;
+	if ((int) delta <= 0)
+		return (delta + timer0_max_count);
+	return (delta);
+}
+#else /* not GUPROF */
+#ifdef __GNUC__
+asm("
+	.text
+	.align	4,0x90
+	.globl	mexitcount
+mexitcount:
+	ret
+");
+#else /* !__GNUC__ */
+#error
+#endif /* __GNUC__ */
+#endif /* GUPROF */