OS-7345 Add support to mdb for anonymous/unnamed structs and unions.mdb-union

Reviewed by: Robert Mustacchi <rm@joyent.com>
Reviewed by: Dan McDonald <danmcd@joyent.com>
Approved by: Dan McDonald <danmcd@joyent.com>

2 files changed, 108 insertions, 5 deletions

diff --git a/usr/src/cmd/mdb/common/mdb/mdb_ctf.c b/usr/src/cmd/mdb/common/mdb/mdb_ctf.c
index 534c92f5dc..4e8f1a161f 100644
--- a/usr/src/cmd/mdb/common/mdb/mdb_ctf.c
+++ b/usr/src/cmd/mdb/common/mdb/mdb_ctf.c
@@ -838,6 +838,7 @@ static int
 member_info_cb(const char *name, mdb_ctf_id_t id, ulong_t off, void *data)
 {
 	mbr_info_t *mbrp = data;
+	int kind, ret;
 
 	if (strcmp(name, mbrp->mbr_member) == 0) {
 		if (mbrp->mbr_offp != NULL)
@@ -848,7 +849,46 @@ member_info_cb(const char *name, mdb_ctf_id_t id, ulong_t off, void *data)
 		return (1);
 	}
 
-	return (0);
+	/*
+	 * C11 as well as earlier GNU extensions allow an embedded struct
+	 * or union to be unnamed as long as there are no unambiguous member
+	 * names.  If we encounter a SOU member with a 0-length name,
+	 * recurse into it and see if any of them match.
+	 */
+	if (strlen(name) != 0)
+		return (0);
+
+	kind = mdb_ctf_type_kind(id);
+	if (kind == CTF_ERR)
+		return (-1);
+	if (kind != CTF_K_STRUCT && kind != CTF_K_UNION)
+		return (0);
+
+	/*
+	 * Search the unnamed SOU for mbrp->mbr_member, possibly recursing if
+	 * it also contains unnamed members.  If the desired member is found.
+	 * *mbrp->mbr_offp will contain the offset of the member relative to
+	 * this unnamed SOU (if the offset was requested) -- i.e.
+	 * we effectively have *mbrp->mbr_offp == offsetof("", member). We want
+	 * unnamed SOUs to act as members of the enclosing SOUs, so we need to
+	 * return the offset as relative to the outer SOU.  Since 'off' is
+	 * the offset of the unnamed SOU relative to the enclosing SOU (i.e.
+	 * off == offsetof(outer, "")), we add the two together to produce the
+	 * desired offset.  This can recurse as necessary -- the compiler
+	 * prevents any ambiguities from occurring (or else it wouldn't be
+	 * able to compile the code), and the result will be relative to
+	 * the start of the SOU given in the mdb_ctf_member_info() call.
+	 */
+	ret = mdb_ctf_member_iter(id, member_info_cb, mbrp);
+	if (ret == -1)
+		return (-1);
+	if (ret == 0)
+		return (0);
+
+	if (mbrp->mbr_offp != NULL)
+		*(mbrp->mbr_offp) += off;
+
+	return (1);
 }
 
 int
@@ -856,10 +896,21 @@ mdb_ctf_member_info(mdb_ctf_id_t id, const char *member, ulong_t *offp,
     mdb_ctf_id_t *typep)
 {
 	mbr_info_t mbr;
+	/*
+	 * We want the resulting offset (if requested -- offp != NULL) to
+	 * be relative to the start of _this_ SOU.  If we have to search any
+	 * embedded unnamed SOUs, instead of merely assigning the resulting
+	 * offset value to mbr_offp, we will have to add the offsets of
+	 * any nested SOUs along the way (see comments in member_info_cb()).
+	 * Therefore, initialize off to 0 here so we do not need to worry about
+	 * recursion depth in member_info_cb (otherwise we would need to set
+	 * mbr_offp when depth = 1, and add when depth > 1).
+	 */
+	ulong_t off = 0;
 	int rc;
 
 	mbr.mbr_member = member;
-	mbr.mbr_offp = offp;
+	mbr.mbr_offp = &off;
 	mbr.mbr_typep = typep;
 
 	rc = mdb_ctf_member_iter(id, member_info_cb, &mbr);
@@ -872,6 +923,9 @@ mdb_ctf_member_info(mdb_ctf_id_t id, const char *member, ulong_t *offp,
 	if (rc == 0)
 		return (set_errno(EMDB_CTFNOMEMB));
 
+	if (offp != NULL)
+		*offp = off;
+
 	return (0);
 }
 
diff --git a/usr/src/cmd/mdb/common/mdb/mdb_print.c b/usr/src/cmd/mdb/common/mdb/mdb_print.c
index fe74265b68..e91bf7a2fc 100644
--- a/usr/src/cmd/mdb/common/mdb/mdb_print.c
+++ b/usr/src/cmd/mdb/common/mdb/mdb_print.c
@@ -25,7 +25,7 @@
 
 /*
  * Copyright (c) 2012, 2014 by Delphix. All rights reserved.
- * Copyright 2015 Joyent, Inc.
+ * Copyright 2018 Joyent, Inc.
  * Copyright (c) 2014 Nexenta Systems, Inc. All rights reserved.
  */
 
@@ -1681,6 +1681,52 @@ elt_print(const char *name, mdb_ctf_id_t id, mdb_ctf_id_t base,
 			mdb_printf("%s%s", pap->pa_prefix,
 			    (depth == 0) ? "" : pap->pa_suffix);
 		mdb_printf("%s", name);
+
+		/*
+		 * When no name is present (i.e. an unnamed struct or union),
+		 * display '(anon)' instead only when no prefix is present.
+		 * When printing out a struct or union (sou), prefixes are
+		 * only present (i.e. !NULL or non-empty)  when printing
+		 * individual members of that sou, e.g.
+		 * `::print struct foo f_member`.  When printing an entire sou,
+		 * the prefix will be NULL or empty.  We end up with:
+		 *
+		 *	> ::print struct foo
+		 *	{
+		 *		...
+		 *		f_member = 0xabcd
+		 *		(anon) = {
+		 *			anon_member = 0x1234
+		 *			....
+		 *		}
+		 *		...
+		 *	}
+		 *
+		 * and
+		 *
+		 *	> ::print struct foo anon_member
+		 *	anon_member = 0x1234
+		 *
+		 * instead of:
+		 *
+		 *	> ::print struct foo
+		 *	{
+		 *		...
+		 *		f_member = 0xabcd
+		 *		= {
+		 *			anon_member = 0x1234
+		 *		}
+		 *		...
+		 *	}
+		 *
+		 * and
+		 *
+		 *	> ::print struct foo anon_member
+		 *	anon_member(anon) = 0x1234
+		 */
+		if (depth > 0 && strlen(name) == 0 &&
+		    (pap->pa_prefix == NULL || strlen(pap->pa_prefix) == 0))
+			mdb_printf("(anon)");
 	}
 
 	if ((pap->pa_flags & PA_SHOWTYPE) && kind == CTF_K_INTEGER) {
@@ -1699,8 +1745,9 @@ elt_print(const char *name, mdb_ctf_id_t id, mdb_ctf_id_t base,
 	}
 
 	if (depth != 0 ||
-	    ((pap->pa_flags & PA_SHOWNAME) && pap->pa_prefix != NULL))
+	    ((pap->pa_flags & PA_SHOWNAME) && pap->pa_prefix != NULL)) {
 		mdb_printf("%s ", pap->pa_flags & PA_SHOWVAL ? " =" : "");
+	}
 
 	if (depth == 0 && pap->pa_prefix != NULL)
 		name = pap->pa_prefix;
@@ -2420,8 +2467,10 @@ cmd_print(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
 				kind = mdb_ctf_type_kind(rid);
 				if (last_deref && IS_SOU(kind)) {
 					char *end;
+					size_t len = strlen(member);
 					(void) mdb_snprintf(buf, sizeof (buf),
-					    "%s", member);
+					    "%s", (len == 0) ?
+					    "<anon>" : member);
 					end = strrchr(buf, '[');
 					*end = '\0';
 					pa.pa_suffix = "->";