[RFC PATCH v5 13/28] dyndbg+module: expose ddebug_sites to modules

From: Jim Cromie
Date: Tue May 11 2021 - 14:52:10 EST

Up until now, the "__dyndbg_sites" section was kinda dangling.

Unlike the "__dyndbg" section, it was not explicitly loaded by
module.c:load_info(); but it came along quietly, perhaps because of
the per .site initialization (by DEFINE_DYNAMIC_DEBUG_METADATA)
across the section boundary, or maybe because x86 is more permissive.
ISTM we need to treat "__dyndbg_sites" section just like "__dyndbg",
on basic principles. (And maybe do this with commit that splits the
sections, if robot tests indicate problems between).

The changes to load_info propagated out to ddebug_add_module's
prototype, which needs to manage the 2nd section like the 1st.

RFC: Maybe the 2 sections/arrays should be a single item/tuple, but I
didn't see any real benefit to adding something; recapitulating the
previous pattern was straightforward.

-v5 fix !CONFIG_DYNAMIC_DEBUG fn-stub
Reported-by: kernel test robot <lkp@xxxxxxxxx>

Signed-off-by: Jim Cromie <jim.cromie@xxxxxxxxx>
---
include/linux/dynamic_debug.h | 8 ++++----
kernel/module-internal.h | 1 +
kernel/module.c | 9 ++++++---
lib/dynamic_debug.c | 20 ++++++++++++--------
4 files changed, 23 insertions(+), 15 deletions(-)

diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index bc4e778b755c..868e0769b72d 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -66,8 +66,8 @@ struct _ddebug {
/* exported for module authors to exercise >control */
int dynamic_debug_exec_queries(const char *query, const char *modname);

-int ddebug_add_module(struct _ddebug *tab, unsigned int n,
- const char *modname);
+int ddebug_add_module(struct _ddebug *tab, struct _ddebug_site *sites,
+ unsigned int numdbgs, const char *modname);
extern int ddebug_remove_module(const char *mod_name);
extern __printf(2, 3)
void __dynamic_pr_debug(struct _ddebug *descriptor, const char *fmt, ...);
@@ -199,8 +199,8 @@ void __dynamic_ibdev_dbg(struct _ddebug *descriptor,
#include <linux/errno.h>
#include <linux/printk.h>

-static inline int ddebug_add_module(struct _ddebug *tab, unsigned int n,
- const char *modname)
+static inline int ddebug_add_module(struct _ddebug *tab, struct _ddebug_site *sites,
+ unsigned int numdbgs, const char *modname)
{
return 0;
}
diff --git a/kernel/module-internal.h b/kernel/module-internal.h
index 33783abc377b..fb61eb2f8032 100644
--- a/kernel/module-internal.h
+++ b/kernel/module-internal.h
@@ -18,6 +18,7 @@ struct load_info {
char *secstrings, *strtab;
unsigned long symoffs, stroffs, init_typeoffs, core_typeoffs;
struct _ddebug *debug;
+ struct _ddebug_site *sites;
unsigned int num_debug;
bool sig_ok;
#ifdef CONFIG_KALLSYMS
diff --git a/kernel/module.c b/kernel/module.c
index 30479355ab85..792903230acd 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2780,11 +2780,12 @@ static void add_kallsyms(struct module *mod, const struct load_info *info)
}
#endif /* CONFIG_KALLSYMS */

-static void dynamic_debug_setup(struct module *mod, struct _ddebug *debug, unsigned int num)
+static void dynamic_debug_setup(struct module *mod, struct _ddebug *debug,
+ struct _ddebug_site *sites, unsigned int num)
{
if (!debug)
return;
- ddebug_add_module(debug, num, mod->name);
+ ddebug_add_module(debug, sites, num, mod->name);
}

static void dynamic_debug_remove(struct module *mod, struct _ddebug *debug)
@@ -3333,6 +3334,8 @@ static int find_module_sections(struct module *mod, struct load_info *info)

info->debug = section_objs(info, "__dyndbg",
sizeof(*info->debug), &info->num_debug);
+ info->sites = section_objs(info, "__dyndbg_sites",
+ sizeof(*info->sites), &info->num_debug);

return 0;
}
@@ -4004,7 +4007,7 @@ static int load_module(struct load_info *info, const char __user *uargs,
goto free_arch_cleanup;
}

- dynamic_debug_setup(mod, info->debug, info->num_debug);
+ dynamic_debug_setup(mod, info->debug, info->sites, info->num_debug);

/* Ftrace init must be called in the MODULE_STATE_UNFORMED state */
ftrace_module_init(mod);
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 76315d20672a..1441b31915e7 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -49,6 +49,7 @@ struct ddebug_table {
const char *mod_name;
unsigned int num_ddebugs;
struct _ddebug *ddebugs;
+ struct _ddebug_site *sites;
};

struct ddebug_query {
@@ -1008,14 +1009,14 @@ static const struct proc_ops proc_fops = {
* Allocate a new ddebug_table for the given module
* and add it to the global list.
*/
-int ddebug_add_module(struct _ddebug *tab, unsigned int n,
- const char *name)
+int ddebug_add_module(struct _ddebug *tab, struct _ddebug_site *sites,
+ unsigned int numdbgs, const char *modname)
{
struct ddebug_table *dt;

dt = kzalloc(sizeof(*dt), GFP_KERNEL);
if (dt == NULL) {
- pr_err("error adding module: %s\n", name);
+ pr_err("error adding module: %s\n", modname);
return -ENOMEM;
}
/*
@@ -1024,15 +1025,16 @@ int ddebug_add_module(struct _ddebug *tab, unsigned int n,
* member of struct module, which lives at least as long as
* this struct ddebug_table.
*/
- dt->mod_name = name;
- dt->num_ddebugs = n;
+ dt->mod_name = modname;
+ dt->num_ddebugs = numdbgs;
dt->ddebugs = tab;
+ dt->sites = sites;

mutex_lock(&ddebug_lock);
list_add(&dt->link, &ddebug_tables);
mutex_unlock(&ddebug_lock);

- v2pr_info("%3u debug prints in module %s\n", n, dt->mod_name);
+ v2pr_info("%3u debug prints in module %s\n", numdbgs, modname);
return 0;
}

@@ -1172,7 +1174,9 @@ static int __init dynamic_debug_init(void)

if (strcmp(modname, site->modname)) {
modct++;
- ret = ddebug_add_module(iter_mod_start, site_ct, modname);
+
+ ret = ddebug_add_module(iter_mod_start, site_mod_start,
+ site_ct, modname);
if (ret)
goto out_err;
site_ct = 0;
@@ -1182,7 +1186,7 @@ static int __init dynamic_debug_init(void)
}
site_ct++;
}
- ret = ddebug_add_module(iter_mod_start, site_ct, modname);
+ ret = ddebug_add_module(iter_mod_start, site_mod_start, site_ct, modname);
if (ret)
goto out_err;

--
2.31.1