kprobes: Introduce NOKPROBE_SYMBOL() macro to maintain kprobes blacklist
Introduce NOKPROBE_SYMBOL() macro which builds a kprobes blacklist at kernel build time. The usage of this macro is similar to EXPORT_SYMBOL(), placed after the function definition: NOKPROBE_SYMBOL(function); Since this macro will inhibit inlining of static/inline functions, this patch also introduces a nokprobe_inline macro for static/inline functions. In this case, we must use NOKPROBE_SYMBOL() for the inline function caller. When CONFIG_KPROBES=y, the macro stores the given function address in the "_kprobe_blacklist" section. Since the data structures are not fully initialized by the macro (because there is no "size" information), those are re-initialized at boot time by using kallsyms. Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Link: http://lkml.kernel.org/r/20140417081705.26341.96719.stgit@ltc230.yrl.intra.hitachi.co.jp Cc: Alok Kataria <akataria@vmware.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Christopher Li <sparse@chrisli.org> Cc: Chris Wright <chrisw@sous-sol.org> Cc: David S. Miller <davem@davemloft.net> Cc: Jan-Simon Möller <dl9pf@gmx.de> Cc: Jeremy Fitzhardinge <jeremy@goop.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: linux-arch@vger.kernel.org Cc: linux-doc@vger.kernel.org Cc: linux-sparse@vger.kernel.org Cc: virtualization@lists.linux-foundation.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -22,8 +22,9 @@ Appendix B: The kprobes sysctl interface
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Kprobes enables you to dynamically break into any kernel routine and
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collect debugging and performance information non-disruptively. You
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can trap at almost any kernel code address, specifying a handler
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can trap at almost any kernel code address(*), specifying a handler
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routine to be invoked when the breakpoint is hit.
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(*: some parts of the kernel code can not be trapped, see 1.5 Blacklist)
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There are currently three types of probes: kprobes, jprobes, and
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kretprobes (also called return probes). A kprobe can be inserted
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@ -273,6 +274,19 @@ using one of the following techniques:
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or
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- Execute 'sysctl -w debug.kprobes_optimization=n'
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1.5 Blacklist
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Kprobes can probe most of the kernel except itself. This means
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that there are some functions where kprobes cannot probe. Probing
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(trapping) such functions can cause a recursive trap (e.g. double
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fault) or the nested probe handler may never be called.
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Kprobes manages such functions as a blacklist.
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If you want to add a function into the blacklist, you just need
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to (1) include linux/kprobes.h and (2) use NOKPROBE_SYMBOL() macro
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to specify a blacklisted function.
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Kprobes checks the given probe address against the blacklist and
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rejects registering it, if the given address is in the blacklist.
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2. Architectures Supported
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Kprobes, jprobes, and return probes are implemented on the following
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@ -57,6 +57,12 @@
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.long (from) - . ; \
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.long (to) - . + 0x7ffffff0 ; \
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.popsection
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# define _ASM_NOKPROBE(entry) \
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.pushsection "_kprobe_blacklist","aw" ; \
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_ASM_ALIGN ; \
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_ASM_PTR (entry); \
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.popsection
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#else
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# define _ASM_EXTABLE(from,to) \
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" .pushsection \"__ex_table\",\"a\"\n" \
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@ -71,6 +77,7 @@
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" .long (" #from ") - .\n" \
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" .long (" #to ") - . + 0x7ffffff0\n" \
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" .popsection\n"
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/* For C file, we already have NOKPROBE_SYMBOL macro */
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#endif
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#endif /* _ASM_X86_ASM_H */
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@ -23,6 +23,7 @@
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#include <linux/efi.h>
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#include <linux/bcd.h>
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#include <linux/highmem.h>
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#include <linux/kprobes.h>
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#include <asm/bug.h>
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#include <asm/paravirt.h>
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@ -389,6 +390,9 @@ __visible struct pv_cpu_ops pv_cpu_ops = {
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.end_context_switch = paravirt_nop,
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};
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/* At this point, native_get_debugreg has a real function entry */
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NOKPROBE_SYMBOL(native_get_debugreg);
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struct pv_apic_ops pv_apic_ops = {
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#ifdef CONFIG_X86_LOCAL_APIC
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.startup_ipi_hook = paravirt_nop,
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@ -109,6 +109,14 @@
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#define BRANCH_PROFILE()
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#endif
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#ifdef CONFIG_KPROBES
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#define KPROBE_BLACKLIST() VMLINUX_SYMBOL(__start_kprobe_blacklist) = .; \
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*(_kprobe_blacklist) \
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VMLINUX_SYMBOL(__stop_kprobe_blacklist) = .;
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#else
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#define KPROBE_BLACKLIST()
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#endif
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#ifdef CONFIG_EVENT_TRACING
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#define FTRACE_EVENTS() . = ALIGN(8); \
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VMLINUX_SYMBOL(__start_ftrace_events) = .; \
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@ -507,6 +515,7 @@
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*(.init.rodata) \
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FTRACE_EVENTS() \
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TRACE_SYSCALLS() \
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KPROBE_BLACKLIST() \
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MEM_DISCARD(init.rodata) \
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CLK_OF_TABLES() \
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RESERVEDMEM_OF_TABLES() \
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@ -374,7 +374,9 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
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/* Ignore/forbid kprobes attach on very low level functions marked by this attribute: */
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#ifdef CONFIG_KPROBES
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# define __kprobes __attribute__((__section__(".kprobes.text")))
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# define nokprobe_inline __always_inline
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#else
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# define __kprobes
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# define nokprobe_inline inline
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#endif
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#endif /* __LINUX_COMPILER_H */
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@ -205,10 +205,10 @@ struct kretprobe_blackpoint {
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void *addr;
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};
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struct kprobe_blackpoint {
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const char *name;
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struct kprobe_blacklist_entry {
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struct list_head list;
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unsigned long start_addr;
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unsigned long range;
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unsigned long end_addr;
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};
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#ifdef CONFIG_KPROBES
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@ -477,4 +477,18 @@ static inline int enable_jprobe(struct jprobe *jp)
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return enable_kprobe(&jp->kp);
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}
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#ifdef CONFIG_KPROBES
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/*
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* Blacklist ganerating macro. Specify functions which is not probed
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* by using this macro.
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*/
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#define __NOKPROBE_SYMBOL(fname) \
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static unsigned long __used \
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__attribute__((section("_kprobe_blacklist"))) \
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_kbl_addr_##fname = (unsigned long)fname;
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#define NOKPROBE_SYMBOL(fname) __NOKPROBE_SYMBOL(fname)
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#else
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#define NOKPROBE_SYMBOL(fname)
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#endif
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#endif /* _LINUX_KPROBES_H */
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100
kernel/kprobes.c
100
kernel/kprobes.c
@ -86,18 +86,8 @@ static raw_spinlock_t *kretprobe_table_lock_ptr(unsigned long hash)
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return &(kretprobe_table_locks[hash].lock);
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}
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/*
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* Normally, functions that we'd want to prohibit kprobes in, are marked
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* __kprobes. But, there are cases where such functions already belong to
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* a different section (__sched for preempt_schedule)
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*
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* For such cases, we now have a blacklist
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*/
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static struct kprobe_blackpoint kprobe_blacklist[] = {
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{"preempt_schedule",},
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{"native_get_debugreg",},
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{NULL} /* Terminator */
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};
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/* Blacklist -- list of struct kprobe_blacklist_entry */
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static LIST_HEAD(kprobe_blacklist);
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#ifdef __ARCH_WANT_KPROBES_INSN_SLOT
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/*
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@ -1328,24 +1318,22 @@ bool __weak arch_within_kprobe_blacklist(unsigned long addr)
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addr < (unsigned long)__kprobes_text_end;
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}
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static int __kprobes in_kprobes_functions(unsigned long addr)
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static bool __kprobes within_kprobe_blacklist(unsigned long addr)
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{
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struct kprobe_blackpoint *kb;
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struct kprobe_blacklist_entry *ent;
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if (arch_within_kprobe_blacklist(addr))
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return -EINVAL;
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return true;
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/*
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* If there exists a kprobe_blacklist, verify and
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* fail any probe registration in the prohibited area
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*/
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for (kb = kprobe_blacklist; kb->name != NULL; kb++) {
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if (kb->start_addr) {
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if (addr >= kb->start_addr &&
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addr < (kb->start_addr + kb->range))
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return -EINVAL;
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}
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list_for_each_entry(ent, &kprobe_blacklist, list) {
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if (addr >= ent->start_addr && addr < ent->end_addr)
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return true;
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}
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return 0;
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return false;
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}
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/*
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@ -1436,7 +1424,7 @@ static __kprobes int check_kprobe_address_safe(struct kprobe *p,
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/* Ensure it is not in reserved area nor out of text */
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if (!kernel_text_address((unsigned long) p->addr) ||
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in_kprobes_functions((unsigned long) p->addr) ||
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within_kprobe_blacklist((unsigned long) p->addr) ||
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jump_label_text_reserved(p->addr, p->addr)) {
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ret = -EINVAL;
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goto out;
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@ -2022,6 +2010,38 @@ void __kprobes dump_kprobe(struct kprobe *kp)
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kp->symbol_name, kp->addr, kp->offset);
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}
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/*
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* Lookup and populate the kprobe_blacklist.
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*
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* Unlike the kretprobe blacklist, we'll need to determine
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* the range of addresses that belong to the said functions,
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* since a kprobe need not necessarily be at the beginning
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* of a function.
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*/
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static int __init populate_kprobe_blacklist(unsigned long *start,
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unsigned long *end)
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{
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unsigned long *iter;
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struct kprobe_blacklist_entry *ent;
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unsigned long offset = 0, size = 0;
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for (iter = start; iter < end; iter++) {
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if (!kallsyms_lookup_size_offset(*iter, &size, &offset)) {
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pr_err("Failed to find blacklist %p\n", (void *)*iter);
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continue;
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}
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ent = kmalloc(sizeof(*ent), GFP_KERNEL);
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if (!ent)
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return -ENOMEM;
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ent->start_addr = *iter;
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ent->end_addr = *iter + size;
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INIT_LIST_HEAD(&ent->list);
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list_add_tail(&ent->list, &kprobe_blacklist);
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}
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return 0;
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}
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/* Module notifier call back, checking kprobes on the module */
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static int __kprobes kprobes_module_callback(struct notifier_block *nb,
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unsigned long val, void *data)
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@ -2065,14 +2085,13 @@ static struct notifier_block kprobe_module_nb = {
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.priority = 0
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};
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/* Markers of _kprobe_blacklist section */
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extern unsigned long __start_kprobe_blacklist[];
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extern unsigned long __stop_kprobe_blacklist[];
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static int __init init_kprobes(void)
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{
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int i, err = 0;
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unsigned long offset = 0, size = 0;
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char *modname, namebuf[KSYM_NAME_LEN];
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const char *symbol_name;
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void *addr;
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struct kprobe_blackpoint *kb;
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/* FIXME allocate the probe table, currently defined statically */
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/* initialize all list heads */
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@ -2082,26 +2101,11 @@ static int __init init_kprobes(void)
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raw_spin_lock_init(&(kretprobe_table_locks[i].lock));
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}
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/*
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* Lookup and populate the kprobe_blacklist.
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*
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* Unlike the kretprobe blacklist, we'll need to determine
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* the range of addresses that belong to the said functions,
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* since a kprobe need not necessarily be at the beginning
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* of a function.
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*/
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for (kb = kprobe_blacklist; kb->name != NULL; kb++) {
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kprobe_lookup_name(kb->name, addr);
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if (!addr)
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continue;
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kb->start_addr = (unsigned long)addr;
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symbol_name = kallsyms_lookup(kb->start_addr,
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&size, &offset, &modname, namebuf);
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if (!symbol_name)
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kb->range = 0;
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else
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kb->range = size;
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err = populate_kprobe_blacklist(__start_kprobe_blacklist,
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__stop_kprobe_blacklist);
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if (err) {
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pr_err("kprobes: failed to populate blacklist: %d\n", err);
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pr_err("Please take care of using kprobes.\n");
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}
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if (kretprobe_blacklist_size) {
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barrier();
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} while (need_resched());
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}
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NOKPROBE_SYMBOL(preempt_schedule);
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EXPORT_SYMBOL(preempt_schedule);
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#endif /* CONFIG_PREEMPT */
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