linux-kernel - [PATCH v6 44/57] dyndbg: extend __ddebug_add

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Date:   Sun,  4 Sep 2022 15:41:21 -0600
From:   Jim Cromie <jim.cromie@...il.com>
To:     jbaron@...mai.com, gregkh@...uxfoundation.org,
        dri-devel@...ts.freedesktop.org, amd-gfx@...ts.freedesktop.org,
        intel-gvt-dev@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Cc:     daniel.vetter@...ll.ch, seanpaul@...omium.org, robdclark@...il.com,
        linux@...musvillemoes.dk, joe@...ches.com,
        Jim Cromie <jim.cromie@...il.com>
Subject: [PATCH v6 44/57] dyndbg: extend __ddebug_add_module proto to allow packing sites

In order to actually reclaim useful blocks of memory, we need to
repack the vector of redundant site recs, not just detect the
duplicates.  To allow this, extend __ddebug_add_module()s prototype by
adding:

   struct _ddebug_site *packed_sites - address of empty "stack"
   unsigned int *packed_base - index of Top-of-Stack

This allows dynamic_debug_init() to tell __ddebug_add_module() where
to push the unique site recs it finds while de-duplicating, and to
communicate the new TOS back for the next iteration.

Since we know we are shrinking data, we can overwrite _ddebug_sites[],
for both builtins, and loadable modules, via ddebug_add_module().

For ddebug_add_module(), which is called from kernel/module/main, the
2 args: reuse the module.sites vector, with a 0 offset.  This will
allow de-duplication of the local vector.

No de-duplication is done yet, so no use of the stack.

Signed-off-by: Jim Cromie <jim.cromie@...il.com>
---
 lib/dynamic_debug.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 506a7e2e59d6..1b57e43e9c31 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -1341,7 +1341,8 @@ static void ddebug_attach_module_classes(struct ddebug_table *dt,
  * and add it to the global list.
  */
 static int __ddebug_add_module(struct _ddebug_info *di, unsigned int base,
-			       const char *modname)
+			       const char *modname, struct _ddebug_site *packed_sites,
+			       unsigned int *packed_base)
 {
 	struct ddebug_table *dt;
 	int i;
@@ -1390,7 +1391,8 @@ static int __ddebug_add_module(struct _ddebug_info *di, unsigned int base,
 
 int ddebug_add_module(struct _ddebug_info *di, const char *modname)
 {
-	return __ddebug_add_module(di, 0, modname);
+	unsigned int packed_base = 0;
+	return __ddebug_add_module(di, 0, modname, di->sites, &packed_base);
 }
 
 /* helper for ddebug_dyndbg_(boot|module)_param_cb */
@@ -1506,7 +1508,7 @@ static int __init dynamic_debug_init(void)
 {
 	struct _ddebug *iter, *iter_mod_start;
 	struct _ddebug_site *site, *site_mod_start;
-	int ret, i, mod_sites, mod_ct;
+	int ret, i, mod_sites, mod_ct, site_base;
 	const char *modname;
 	char *cmdline;
 
@@ -1550,7 +1552,8 @@ static int __init dynamic_debug_init(void)
 			di.num_descs = mod_sites;
 			di.descs = iter_mod_start;
 			di.sites = site_mod_start;
-			ret = __ddebug_add_module(&di, i - mod_sites, modname);
+			ret = __ddebug_add_module(&di, i - mod_sites, modname,
+						  __start___dyndbg_sites, &site_base);
 			if (ret)
 				goto out_err;
 
@@ -1563,11 +1566,13 @@ static int __init dynamic_debug_init(void)
 	di.num_descs = mod_sites;
 	di.descs = iter_mod_start;
 	di.sites = site_mod_start;
-	ret = __ddebug_add_module(&di, i - mod_sites, modname);
+	ret = __ddebug_add_module(&di, i - mod_sites, modname,
+				  __start___dyndbg_sites, &site_base);
 	if (ret)
 		goto out_err;
 
 	ddebug_init_success = 1;
+
 	vpr_info("%d prdebugs in %d modules, %d KiB in ddebug tables, %d kiB in __dyndbg section\n",
 		 i, mod_ct, (int)((mod_ct * sizeof(struct ddebug_table)) >> 10),
 		 (int)((i * sizeof(struct _ddebug)) >> 10));
-- 
2.37.2