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Subject[PATCH v4 06/16] dyndbg: fix a BUG_ON in ddebug_describe_flags
Date
ddebug_describe_flags currently fills a caller provided string buffer,
after testing its size (also passed) in a BUG_ON. Fix this with a
struct containing a known-big-enough string buffer, and passing it
instead.

Also simplify ddebug_describe_flags sig, and de-ref the struct in the
caller; this makes function reusable (soon) in contexts where flags
are already unpacked.

-v3 fix compile err introduced in patchset grooming.
Reported-by: kbuild test robot <lkp@intel.com>

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
lib/dynamic_debug.c | 31 +++++++++++++++----------------
1 file changed, 15 insertions(+), 16 deletions(-)

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index b5fb0aa0fbc3..49cb24948e12 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -62,6 +62,8 @@ struct ddebug_iter {
unsigned int idx;
};

+struct flagsbuf { char buf[12]; }; /* big enough to hold all the flags */
+
static DEFINE_MUTEX(ddebug_lock);
static LIST_HEAD(ddebug_tables);
static int verbose;
@@ -88,21 +90,19 @@ static struct { unsigned flag:8; char opt_char; } opt_array[] = {
};

/* format a string into buf[] which describes the _ddebug's flags */
-static char *ddebug_describe_flags(struct _ddebug *dp, char *buf,
- size_t maxlen)
+static char *ddebug_describe_flags(unsigned int flags, struct flagsbuf *fb)
{
- char *p = buf;
+ char *p = fb->buf;
int i;

- BUG_ON(maxlen < 6);
for (i = 0; i < ARRAY_SIZE(opt_array); ++i)
- if (dp->flags & opt_array[i].flag)
+ if (flags & opt_array[i].flag)
*p++ = opt_array[i].opt_char;
- if (p == buf)
+ if (p == fb->buf)
*p++ = '_';
*p = '\0';

- return buf;
+ return fb->buf;
}

#define vnpr_info(lvl, fmt, ...) \
@@ -142,13 +142,13 @@ static void vpr_info_dq(const struct ddebug_query *query, const char *msg)
* logs the changes. Takes ddebug_lock.
*/
static int ddebug_change(const struct ddebug_query *query,
- unsigned int flags, unsigned int mask)
+ unsigned int pflags, unsigned int mask)
{
int i;
struct ddebug_table *dt;
unsigned int newflags;
unsigned int nfound = 0;
- char flagbuf[10];
+ struct flagsbuf flags;

/* search for matching ddebugs */
mutex_lock(&ddebug_lock);
@@ -191,22 +191,21 @@ static int ddebug_change(const struct ddebug_query *query,

nfound++;

- newflags = (dp->flags & mask) | flags;
+ newflags = (dp->flags & mask) | pflags;
if (newflags == dp->flags)
continue;
#ifdef CONFIG_JUMP_LABEL
if (dp->flags & _DPRINTK_FLAGS_PRINT) {
- if (!(flags & _DPRINTK_FLAGS_PRINT))
+ if (!(pflags & _DPRINTK_FLAGS_PRINT))
static_branch_disable(&dp->key.dd_key_true);
- } else if (flags & _DPRINTK_FLAGS_PRINT)
+ } else if (pflags & _DPRINTK_FLAGS_PRINT)
static_branch_enable(&dp->key.dd_key_true);
#endif
dp->flags = newflags;
vpr_info("changed %s:%d [%s]%s =%s\n",
trim_prefix(dp->filename), dp->lineno,
dt->mod_name, dp->function,
- ddebug_describe_flags(dp, flagbuf,
- sizeof(flagbuf)));
+ ddebug_describe_flags(dp->flags, &flags));
}
}
mutex_unlock(&ddebug_lock);
@@ -820,7 +819,7 @@ static int ddebug_proc_show(struct seq_file *m, void *p)
{
struct ddebug_iter *iter = m->private;
struct _ddebug *dp = p;
- char flagsbuf[10];
+ struct flagsbuf flags;

v9pr_info("called m=%p p=%p\n", m, p);

@@ -833,7 +832,7 @@ static int ddebug_proc_show(struct seq_file *m, void *p)
seq_printf(m, "%s:%u [%s]%s =%s \"",
trim_prefix(dp->filename), dp->lineno,
iter->table->mod_name, dp->function,
- ddebug_describe_flags(dp, flagsbuf, sizeof(flagsbuf)));
+ ddebug_describe_flags(dp->flags, &flags));
seq_escape(m, dp->format, "\t\r\n\"");
seq_puts(m, "\"\n");

--
2.23.0
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