Messages in this thread | | | From | Oskar Andero <> | Date | Thu, 4 Apr 2013 09:57:18 +0200 | Subject | Re: [PATCH 1/4] kprobes: delay blacklist symbol lookup until we actually need it |
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On 08:44 Thu 04 Apr , Masami Hiramatsu wrote: > (2013/04/03 17:28), oskar.andero@sonymobile.com wrote: > > > > +/* 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; > > + > > + /* > > + * 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; > > +} > > + > > #ifdef __ARCH_WANT_KPROBES_INSN_SLOT > > /* > > * kprobe->ainsn.insn points to the copy of the instruction to be > > @@ -1331,6 +1379,9 @@ 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 (!kprobe_blacklist_initialized) > > + init_kprobe_blacklist(); > > /* > > * If there exists a kprobe_blacklist, verify and > > * fail any probe registration in the prohibited area > > @@ -1816,6 +1867,8 @@ int __kprobes register_kretprobe(struct kretprobe *rp) > > void *addr; > > > > if (kretprobe_blacklist_size) { > > + if (!kprobe_blacklist_initialized) > > + init_kprobe_blacklist(); > > Joonsoo reminds me that these calling points are not protected by kprobe_mutex, > thus we have to do something for avoiding concurrent initialization. > > Perhaps, the easiest way is to protect init_kprobe_blacklist() by kprobe_mutex > and check kprobe_blacklist_initialized again in the top of that.
Yes, you are right. I had a second look at Joonsoo's patch and I will add a similar mutex for v2.
-Oskar
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