Thanks for your input guys!
On 04:16 Fri 05 Apr , Masami Hiramatsu wrote:
> (2013/04/05 9:56), Joonsoo Kim wrote:
> > Hello, Oskar.
> >
> > On Thu, Apr 04, 2013 at 02:51:26PM +0200, Oskar Andero wrote:
> >> From: Toby Collett <toby.collett@xxxxxxxxxxxxxx>
> >>
> >> The symbol lookup can take a long time and kprobes is
> >> initialised very early in boot, so delay symbol lookup
> >> until the blacklist is first used.
> >>
> >> Cc: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
> >> Cc: David S. Miller <davem@xxxxxxxxxxxxx>
> >> Reviewed-by: Radovan Lekanovic <radovan.lekanovic@xxxxxxxxxxxxxx>
> >> Signed-off-by: Toby Collett <toby.collett@xxxxxxxxxxxxxx>
> >> Signed-off-by: Oskar Andero <oskar.andero@xxxxxxxxxxxxxx>
> >> ---
> >> kernel/kprobes.c | 98 ++++++++++++++++++++++++++++++++++----------------------
> >> 1 file changed, 60 insertions(+), 38 deletions(-)
> >>
> >> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> >> index e35be53..0a270e5 100644
> >> --- a/kernel/kprobes.c
> >> +++ b/kernel/kprobes.c
> >> @@ -68,6 +68,7 @@
> >> #endif
> >>
> >> static int kprobes_initialized;
> >> +static int kprobe_blacklist_initialized;
> >> static struct hlist_head kprobe_table[KPROBE_TABLE_SIZE];
> >> static struct hlist_head kretprobe_inst_table[KPROBE_TABLE_SIZE];
> >>
> >> @@ -102,6 +103,60 @@ static struct kprobe_blackpoint kprobe_blacklist[] = {
> >> {NULL} /* Terminator */
> >> };
> >>
> >> +/* it can take some time ( > 100ms ) to initialise the
> >> + * blacklist so we delay this until we actually need it
> >> + */
> >> +static void init_kprobe_blacklist(void)
> >> +{
> >> + int i;
> >> + unsigned long offset = 0, size = 0;
> >> + char *modname, namebuf[128];
> >> + const char *symbol_name;
> >> + void *addr;
> >> + struct kprobe_blackpoint *kb;
> >> +
> >> + mutex_lock(&kprobe_mutex);
> >> + if (kprobe_blacklist_initialized)
> >> + goto out;
> >> +
> >> + /*
> >> + * Lookup and populate the kprobe_blacklist.
> >> + *
> >> + * Unlike the kretprobe blacklist, we'll need to determine
> >> + * the range of addresses that belong to the said functions,
> >> + * since a kprobe need not necessarily be at the beginning
> >> + * of a function.
> >> + */
> >> + for (kb = kprobe_blacklist; kb->name != NULL; kb++) {
> >> + kprobe_lookup_name(kb->name, addr);
> >> + if (!addr)
> >> + continue;
> >> +
> >> + kb->start_addr = (unsigned long)addr;
> >> + symbol_name = kallsyms_lookup(kb->start_addr,
> >> + &size, &offset, &modname, namebuf);
> >> + if (!symbol_name)
> >> + kb->range = 0;
> >> + else
> >> + kb->range = size;
> >> + }
> >> +
> >> + if (kretprobe_blacklist_size) {
> >> + /* lookup the function address from its name */
> >> + for (i = 0; kretprobe_blacklist[i].name != NULL; i++) {
> >> + kprobe_lookup_name(kretprobe_blacklist[i].name,
> >> + kretprobe_blacklist[i].addr);
> >> + if (!kretprobe_blacklist[i].addr)
> >> + printk("kretprobe: lookup failed: %s\n",
> >> + kretprobe_blacklist[i].name);
> >> + }
> >> + }
> >> + kprobe_blacklist_initialized = 1;
> >
> > You need smp_wmb() before assigning 'kprobe_blacklist_initialized = 1'.
> > This guarantee that who see kprobe_blacklist_initialized = 1 will get
> > updated data of kprobe_blacklist.
>
> Right, to ensure blacklist is updated, memory barrier is required.
Agreed.
> > Please refer my previous patch once more :)
> >
> > And How about define kprobe_blacklist_initialized as boolean?
>
> Good idea :)
>
I'll fix it for v3.
-Oskar
>
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