(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.
> Please refer my previous patch once more :)
>
> And How about define kprobe_blacklist_initialized as boolean?
Good idea :)
Thank you,
--
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@xxxxxxxxxxx
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