libsa: Add support for timestamp logging (tslog)

At present this only supports x86, due to the use of the rdtsc
instruction; and is inert unless a buffer is allocated and passed to
the tslog code (which will be done by a future commit).

Reviewed by:	kevans

stand/libsa/Makefile

@@ -16,7 +16,7 @@ LIB?=		sa
 SRCS+=	gzguts.h zutil.h __main.c abort.c assert.c bcd.c environment.c \
 	getopt.c gets.c globals.c \
 	hexdump.c pager.c panic.c printf.c strdup.c strerror.c \
-	random.c sbrk.c twiddle.c zalloc.c zalloc_malloc.c
+	random.c sbrk.c tslog.c twiddle.c zalloc.c zalloc_malloc.c
 
 # private (pruned) versions of libc string functions
 SRCS+=	strcasecmp.c

stand/libsa/stand.h

@@ -473,4 +473,13 @@ caddr_t ptov(uintptr_t);
 /* hexdump.c */
 void	hexdump(caddr_t region, size_t len);
 
+/* tslog.c */
+#define TSRAW(a, b, c) tslog(a, b, c)
+#define TSENTER() TSRAW("ENTER", __func__, NULL)
+#define TSEXIT() TSRAW("EXIT", __func__, NULL)
+#define TSLINE() TSRAW("EVENT", __FILE__, __XSTRING(__LINE__))
+void tslog(const char *, const char *, const char *);
+void tslog_setbuf(void * buf, size_t len);
+void tslog_getbuf(void ** buf, size_t * len);
+
 #endif	/* STAND_H */

stand/libsa/tslog.c

@@ -0,0 +1,78 @@
+/*-
+ * Copyright (c) 2021 Colin Percival
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/types.h>
+
+#include <machine/cpufunc.h>
+
+#include <stand.h>
+
+/* Buffer for holding tslog data in string format. */
+static char * tslog_buf = NULL;
+static size_t tslog_buflen = 0;
+static size_t tslog_bufpos = 0;
+
+void
+tslog_setbuf(void * buf, size_t len)
+{
+
+	tslog_buf = (char *)buf;
+	tslog_buflen = len;
+	tslog_bufpos = 0;
+}
+
+void
+tslog_getbuf(void ** buf, size_t * len)
+{
+
+	*buf = (void *)tslog_buf;
+	*len = tslog_bufpos;
+}
+
+void
+tslog(const char * type, const char * f, const char * s)
+{
+#if defined(__amd64__) || defined(__i386__)
+	uint64_t tsc = rdtsc();
+#else
+	uint64_t tsc = 0;
+#endif
+	int len;
+
+	/* If we have no buffer, do nothing. */
+	if (tslog_buf == NULL)
+		return;
+
+	/* Append to existing buffer, if we have enough space. */
+	len = snprintf(&tslog_buf[tslog_bufpos],
+	    tslog_buflen - tslog_bufpos, "0x0 %llu %s %s%s%s\n",
+	    (unsigned long long)tsc, type, f, s ? " " : "", s ? s : "");
+	if ((len > 0) && (tslog_bufpos + len <= tslog_buflen))
+		tslog_bufpos += len;
+}