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Message-ID: <20130405005628.GA13624@lge.com>
Date: Fri, 5 Apr 2013 09:56:28 +0900
From: Joonsoo Kim <iamjoonsoo.kim@....com>
To: Oskar Andero <oskar.andero@...ymobile.com>
Cc: linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
masami.hiramatsu.pt@...achi.com, davem@...emloft.net,
anil.s.keshavamurthy@...el.com, ananth@...ibm.com,
radovan.lekanovic@...ymobile.com, bjorn.davidsson@...ymobile.com,
Toby Collett <toby.collett@...ymobile.com>
Subject: Re: [PATCH v2 1/4] kprobes: delay blacklist symbol lookup until we
actually need it
Hello, Oskar.
On Thu, Apr 04, 2013 at 02:51:26PM +0200, Oskar Andero wrote:
> From: Toby Collett <toby.collett@...ymobile.com>
>
> 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@...achi.com>
> Cc: David S. Miller <davem@...emloft.net>
> Reviewed-by: Radovan Lekanovic <radovan.lekanovic@...ymobile.com>
> Signed-off-by: Toby Collett <toby.collett@...ymobile.com>
> Signed-off-by: Oskar Andero <oskar.andero@...ymobile.com>
> ---
> 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.
Please refer my previous patch once more :)
And How about define kprobe_blacklist_initialized as boolean?
Thanks.
> +
> +out:
> + mutex_unlock(&kprobe_mutex);
> +}
> +
> #ifdef __ARCH_WANT_KPROBES_INSN_SLOT
> /*
> * kprobe->ainsn.insn points to the copy of the instruction to be
> @@ -1331,6 +1386,9 @@ static int __kprobes in_kprobes_functions(unsigned long addr)
> if (addr >= (unsigned long)__kprobes_text_start &&
> addr < (unsigned long)__kprobes_text_end)
> return -EINVAL;
> +
> + if (unlikely(!kprobe_blacklist_initialized))
> + init_kprobe_blacklist();
> /*
> * If there exists a kprobe_blacklist, verify and
> * fail any probe registration in the prohibited area
> @@ -1816,6 +1874,8 @@ int __kprobes register_kretprobe(struct kretprobe *rp)
> void *addr;
>
> if (kretprobe_blacklist_size) {
> + if (unlikely(!kprobe_blacklist_initialized))
> + init_kprobe_blacklist();
> addr = kprobe_addr(&rp->kp);
> if (IS_ERR(addr))
> return PTR_ERR(addr);
> @@ -2065,11 +2125,6 @@ static struct notifier_block kprobe_module_nb = {
> static int __init init_kprobes(void)
> {
> int i, err = 0;
> - unsigned long offset = 0, size = 0;
> - char *modname, namebuf[128];
> - const char *symbol_name;
> - void *addr;
> - struct kprobe_blackpoint *kb;
>
> /* FIXME allocate the probe table, currently defined statically */
> /* initialize all list heads */
> @@ -2079,39 +2134,6 @@ static int __init init_kprobes(void)
> raw_spin_lock_init(&(kretprobe_table_locks[i].lock));
> }
>
> - /*
> - * 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);
> - }
> - }
> -
> #if defined(CONFIG_OPTPROBES)
> #if defined(__ARCH_WANT_KPROBES_INSN_SLOT)
> /* Init kprobe_optinsn_slots */
> --
> 1.8.1.5
>
> --
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