[RFC PATCH v6 25/34] dyndbg: make site pointer and checks on it optional (almost)

Jim Cromie
2021-05-29T20:03:34Z

Hide declaration and uses of _ddebug.site pointer in SITE_* macros,
defined alternately for SITE_CHK true/undefined.

Mostly, this eliminates all the WARN_ONs in ddebug_site_get(),
which seem to be mostly proven (they were BUG_ONs).

NOTE:

This breaks when !defined SITE_CHK - the header, being just a struct
_ddebug, also loses the .site member. Need to specialize the header
struct to keep it, then unionize it back into the sites vector.

In DEFINE_DYNAMIC_DEBUG_TABLE, we keep the raw initialization;
we want this init when specialization & unionization is finished.

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
include/linux/dynamic_debug.h | 18 +++++++++++++++---
lib/dynamic_debug.c | 13 ++++++++++---
2 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index a99973221f94..7acd4c88411d 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -6,6 +6,18 @@
#include <linux/jump_label.h>
#endif

+#define SITE_CHK /* include .site pointer and checks on it */
+
+#ifdef SITE_CHK
+#define SITE_CHK_(...) __VA_ARGS__
+#define SITE_COND(_i, _s) (_s == _i->site)
+#define SITE_INIT_(_name) .site = &_name,
+#else
+#define SITE_CHK_(...)
+#define SITE_COND(_i, _s) (true)
+#define SITE_INIT_(name)
+#endif
+
/*
* A pair of these structs are created in 2 special ELF sections
* (__dyndbg, __dyndbg_sites) for every dynamic debug callsite.
@@ -25,7 +37,7 @@ struct _ddebug_site {
} __aligned(8);

struct _ddebug {
- struct _ddebug_site *site;
+ SITE_CHK_(struct _ddebug_site *site;)
/* format is always needed, lineno shares word with flags */
const char *format;
const unsigned lineno:18;
@@ -106,7 +118,7 @@ void __dynamic_ibdev_dbg(struct _ddebug *descriptor,
}; \
static struct _ddebug __aligned(8) \
__section("__dyndbgs") name = { \
- .site = &name##_site, \
+ SITE_INIT_(name##_site) \
.format = (fmt), \
.lineno = __LINE__, \
.flags = _DPRINTK_FLAGS_DEFAULT, \
@@ -144,7 +156,7 @@ void __dynamic_ibdev_dbg(struct _ddebug *descriptor,

/* The header initializations as a distinguishing predicate */
#define is_dyndbg_header_pair(iter, sitep) \
- (sitep == iter->site \
+ (SITE_COND(iter, sitep) \
&& (!iter->lineno) \
&& (iter->format == sitep->modname) \
&& (sitep->modname == sitep->function) \
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 9a089b8d2ccd..f333fcb6cf1f 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -151,7 +151,7 @@ static struct _ddebug_site *ddebug_site_get(struct _ddebug *dp)
struct _ddebug *dh = dp - (dp->_index);

WARN_ON(!is_dyndbg_header_pair(dh, dh->site));
-
+#ifdef SITE_CHK
if (dp >= __start___dyndbg && dp < __stop___dyndbg) {

v5pr_info("get: %s is builtin: %d %s:%s:%d\n",
@@ -177,6 +177,9 @@ static struct _ddebug_site *ddebug_site_get(struct _ddebug *dp)
WARN_ON(&dh->site[dp->_index] != dp->site);

return dp->site;
+#else
+ return &dh->site[dp->_index];
+#endif
}
static inline void ddebug_site_put(struct _ddebug *dp)
{
@@ -241,6 +244,7 @@ static void ddebug_alter_site(struct _ddebug *dp,
} else if (modifiers->flags & _DPRINTK_FLAGS_PRINT)
static_branch_enable(&dp->key.dd_key_true);
#endif
+#ifdef SITE_CHK
/* delete site info for this callsite */
if (modifiers->flags & _DPRINTK_FLAGS_DELETE_SITE) {
if (dp->site) {
@@ -249,6 +253,7 @@ static void ddebug_alter_site(struct _ddebug *dp,
dp->site = NULL;
}
}
+#endif
}

/*
@@ -1073,7 +1078,9 @@ static int __ddebug_add_module(struct _ddebug *tab, struct _ddebug_site *sites,

v3pr_info(" header: %d %s.%s.%d\n", tab[0]._index, modname,
tab[0].site->function, tab[0].lineno);
- WARN_ON(tab[0].site != &sites[0]);
+
+ SITE_CHK_(BUG_ON(tab[0].site != &sites[0]));
+
if (numdbgs <= 1) {
v3pr_info(" skip header %s\n", modname);
return 0;
@@ -1251,7 +1258,7 @@ static int __init dynamic_debug_init(void)

for (i = 0; iter < __stop___dyndbg; iter++, site++, i++) {

- WARN_ON(site != iter->site);
+ SITE_CHK_(WARN_ON(site != iter->site));

if (strcmp(modname, site->modname)) {
modct++;
--
2.31.1