linux-kernel - [RFC PATCH v6 30/34] dyndbg: split/copy ._index into 2 new fields: ._back, .

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Message-Id: <20210529200029.205306-31-jim.cromie@gmail.com>
Date:   Sat, 29 May 2021 14:00:25 -0600
From:   Jim Cromie <jim.cromie@...il.com>
To:     jbaron@...mai.com, gregkh@...uxfoundation.org,
        linux-kernel@...r.kernel.org
Cc:     Jim Cromie <jim.cromie@...il.com>
Subject: [RFC PATCH v6 30/34] dyndbg: split/copy ._index into 2 new fields: ._back, ._map

In order to do:
  __dyndbgs[-N].site->__dyndbg_sites[N]

._index had 2 jobs:
  provide index back to __dyndbgs[0]
  provide index out to __dyndbg_sites[N]

So rename ._index to ._back & ._map, adjust ddebug_add_module()
to init both fields identically, and replace other ._index's
with the "correct" replacement.

NOTES:

._map is a better name better than ._out.  Since ._map is a
separate field, it can map arbitrarily.  It now maps ddebugs->sites
1->1, but it can/will-soon map N->1; all a function's pr_debugs
will share a single _ddebug_site, and we can reclaim redundant rows.

The "correct" choice of ._map/._back cannot be tested properly now,
since ._map == ._back.  Once N->1 is done, we can re-define SITE_CHK
and validate (or correct) the ._map/._back choices made here.

No functional changes.

Signed-off-by: Jim Cromie <jim.cromie@...il.com>
---
 include/linux/dynamic_debug.h |  6 ++++--
 lib/dynamic_debug.c           | 35 ++++++++++++++++++-----------------
 2 files changed, 22 insertions(+), 19 deletions(-)

diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index b2189ff94fda..fe70dda704d2 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -51,7 +51,8 @@ struct _ddebug {
 	/* format is always needed, lineno shares word with flags */
 	const char *format;
 	const unsigned lineno:18;
-	unsigned _index:14;
+	unsigned _back:14;
+	unsigned _map:14;
 	/*
 	 * The flags field controls the behaviour at the callsite.
 	 * The bits here are changed dynamically when the user
@@ -95,7 +96,8 @@ union _ddebug_header {
 		union _ddebug_site_header *site;
 		const char *format;
 		const unsigned lineno:18;
-		unsigned _index:14;
+		unsigned _back:14;
+		unsigned _map:14;
 		unsigned int flags:8;
 	};
 };
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 0e2e082b487b..524303a04462 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -148,39 +148,39 @@ static void vpr_info_dq(const struct ddebug_query *query, const char *msg)
 
 static struct _ddebug_site *ddebug_site_get(struct _ddebug *dp)
 {
-	union _ddebug_header *dh = (union _ddebug_header *) (dp - dp->_index);
+	union _ddebug_header *dh = (union _ddebug_header *) (dp - dp->_back);
 
 	if (!is_dyndbg_header_pair(dh, dh->site))
-		v3pr_info("get: header fail on %d-%d\n", dp->_index, dp->lineno);
+		v3pr_info("get: header fail on %d-%d\n", dp->_back, dp->lineno);
 
 #ifdef SITE_CHK
 	if (dp >= __start___dyndbg && dp < __stop___dyndbg) {
 
 		v5pr_info("get: %s is builtin: %d %s:%s:%d\n",
-			  dh->site[dp->_index].modname, dp->_index,
-			  dh->site[dp->_index].filename,
-			  dh->site[dp->_index].function, dp->lineno);
+			  dh->site[dp->_map].modname, dp->_back,
+			  dh->site[dp->_map].filename,
+			  dh->site[dp->_map].function, dp->lineno);
 
-		BUG_ON(dp != &__start___dyndbg[dp->_index]);
+		BUG_ON(dp != &__start___dyndbg[dp->_back]);
 
-		BUG_ON(!(dp->_index == (dp - dh) &&
-			 dp->_index == (dp - __start___dyndbg) &&
-			 dp->_index == (&__start___dyndbg_sites[dp->_index]
+		BUG_ON(!(dp->_back == (dp - dh) &&
+			 dp->_back == (dp - __start___dyndbg) &&
+			 dp->_back == (&__start___dyndbg_sites[dp->_back]
 					- &__start___dyndbg_sites[0])));
 		if (dp->site)
-			BUG_ON(&__start___dyndbg_sites[dp->_index] != dp->site);
+			BUG_ON(&__start___dyndbg_sites[dp->_map] != dp->site);
 	} else {
 		v4pr_info("get: %s is loaded: %d %s:%s:%d\n",
-			  dh->site[dp->_index].modname, dp->_index,
-			  dh->site[dp->_index].filename,
-			  dh->site[dp->_index].function, dp->lineno);
+			  dh->site[dp->_map].modname, dp->_back,
+			  dh->site[dp->_map].filename,
+			  dh->site[dp->_map].function, dp->lineno);
 	}
 	if (dp->site)
-		BUG_ON(&dh->site[dp->_index] != dp->site);
+		BUG_ON(&dh->site[dp->_map] != dp->site);
 
 	return dp->site;
 #else
-	return (struct _ddebug_site *) &dh->site[dp->_index];
+	return (struct _ddebug_site *) &dh->site[dp->_map];
 #endif
 }
 static inline void ddebug_site_put(struct _ddebug *dp)
@@ -1108,8 +1108,9 @@ static int __ddebug_add_module(struct _ddebug *tab, struct _ddebug_site *sites,
 	dt->sites = sites;
 
 	for (i = 0; i < numdbgs; i++) {
-		tab[i]._index = base + i;
-		v3pr_info(" %d %d %s.%s.%d\n", i, tab[i]._index,
+		tab[i]._back = base + i;
+		tab[i]._map = base + i;
+		v3pr_info(" %d %d %d %s.%s.%d\n", i, tab[i]._back, tab[i]._map,
 			  modname, sites[i].function, tab[i].lineno);
 	}
 
-- 
2.31.1