Re: [PATCH] twist: allow converting pr_devel()/pr_debug() into printk(KERN_DEBUG)

From: Joe Perches
Date: Mon May 25 2020 - 02:07:29 EST


On Mon, 2020-05-25 at 14:03 +0900, Tetsuo Handa wrote:
> On 2020/05/25 4:18, Ondrej Mosnacek wrote:
> > I'm also not sure if this is really worth it... It would help localize
> > the bug in this specific case, but there is nothing systematic about
> > it. Are there that many debug print statements that dereference
> > pointers that are later passed to functions, but not dereferenced
> > otherwise? Maybe yes, but it seems to be quite an optimistic
> > assumption... I don't consider it such a big problem that a bug in
> > function X only manifests itself deeper in the callchain. There will
> > always be such bugs, no matter how many moles you whack.
>
> There are about 1400 pr_debug() callers. About 1000 pr_debug() callers seem
> to pass plain '%p' (which is now likely useless for debugging purpose due to
> default ptr_to_id() conversion inside pointer()), and about 400 pr_debug()
> callers seem to pass '%p[a-zA-Z]' (which does some kind of dereference inside
> pointer()). Thus, we might find some bugs by evaluating '%p[a-zA-Z]'.
>
>
>
> On Sun, May 24, 2020 at 7:38 PM Joe Perches <joe@xxxxxxxxxxx> wrote:
> > While I think this is rather unnecessary,
> > what about dev_dbg/netdev_dbg/netif_dbg et al ?
>
> Maybe a good idea, for there are about 24000 *dev_dbg() callers, and
> 479 callers pass '%p[a-zA-Z]'. But we can defer to another patch, in
> case this patch finds crashes before fuzz testing process starts.

There are a bunch more than that.
Some use other macros, some are functions.

$ grep-2.5.4 --include=*.[ch] -n -rP '\w+_dbg\s*\((?:[^,"]+,){0,3}\s*"[^"]+%p\w+\b[^"]*"' * | \
perl -e 'local $/; while (<>) { s/\n\s+/ /g; print; }' | \
grep -o -P '\w+_dbg' | \
sort | uniq -c | sort -rn
415 dev_dbg
116 netdev_dbg
100 batadv_dbg
80 ath10k_dbg
53 mwifiex_dbg
49 ath11k_dbg
29 brcmf_dbg
28 ath_dbg
26 ht_dbg
20 ath6kl_dbg
17 wcn36xx_dbg
15 netif_dbg
15 cifs_dbg
14 tdls_dbg
13 ibss_dbg
11 mpl_dbg
10 memblock_dbg
10 bt_dev_dbg
9 ps_dbg
8 wiphy_dbg
8 mps_dbg
8 mlme_dbg
8 mhwmp_dbg
8 ipoib_dbg
7 sta_dbg
7 slave_dbg
7 pci_dbg
7 ibdev_dbg
6 mpath_dbg
6 en_dbg
6 drm_dbg
5 usnic_dbg
5 mlx5_core_dbg
4 vin_dbg
4 msync_dbg
3 rsi_dbg
3 cal_dbg
2 v4l2_dbg
2 siw_dbg
2 sdata_dbg
2 ocb_dbg
2 musb_dbg
2 hw_dbg
2 eeh_edev_dbg
2 cifs_server_dbg
2 at76_dbg
1 rt2x00_eeprom_dbg
1 pnp_dbg
1 mthca_dbg
1 mlx5_ib_dbg
1 mlx4_dbg
1 isp_dbg
1 gfs2_print_dbg
1 erofs_dbg
1 dynamic_drbd_dbg
1 ctx_dbg
1 cs89_dbg