mirror of
https://github.com/torvalds/linux.git
synced 2024-11-01 09:41:44 +00:00
73649dab0f
The following patch adds the x86_64 architecture specific implementation
for function return probes.
Function return probes is a mechanism built on top of kprobes that allows
a caller to register a handler to be called when a given function exits.
For example, to instrument the return path of sys_mkdir:
static int sys_mkdir_exit(struct kretprobe_instance *i, struct pt_regs *regs)
{
printk("sys_mkdir exited\n");
return 0;
}
static struct kretprobe return_probe = {
.handler = sys_mkdir_exit,
};
<inside setup function>
return_probe.kp.addr = (kprobe_opcode_t *) kallsyms_lookup_name("sys_mkdir");
if (register_kretprobe(&return_probe)) {
printk(KERN_DEBUG "Unable to register return probe!\n");
/* do error path */
}
<inside cleanup function>
unregister_kretprobe(&return_probe);
The way this works is that:
* At system initialization time, kernel/kprobes.c installs a kprobe
on a function called kretprobe_trampoline() that is implemented in
the arch/x86_64/kernel/kprobes.c (More on this later)
* When a return probe is registered using register_kretprobe(),
kernel/kprobes.c will install a kprobe on the first instruction of the
targeted function with the pre handler set to arch_prepare_kretprobe()
which is implemented in arch/x86_64/kernel/kprobes.c.
* arch_prepare_kretprobe() will prepare a kretprobe instance that stores:
- nodes for hanging this instance in an empty or free list
- a pointer to the return probe
- the original return address
- a pointer to the stack address
With all this stowed away, arch_prepare_kretprobe() then sets the return
address for the targeted function to a special trampoline function called
kretprobe_trampoline() implemented in arch/x86_64/kernel/kprobes.c
* The kprobe completes as normal, with control passing back to the target
function that executes as normal, and eventually returns to our trampoline
function.
* Since a kprobe was installed on kretprobe_trampoline() during system
initialization, control passes back to kprobes via the architecture
specific function trampoline_probe_handler() which will lookup the
instance in an hlist maintained by kernel/kprobes.c, and then call
the handler function.
* When trampoline_probe_handler() is done, the kprobes infrastructure
single steps the original instruction (in this case just a top), and
then calls trampoline_post_handler(). trampoline_post_handler() then
looks up the instance again, puts the instance back on the free list,
and then makes a long jump back to the original return instruction.
So to recap, to instrument the exit path of a function this implementation
will cause four interruptions:
- A breakpoint at the very beginning of the function allowing us to
switch out the return address
- A single step interruption to execute the original instruction that
we replaced with the break instruction (normal kprobe flow)
- A breakpoint in the trampoline function where our instrumented function
returned to
- A single step interruption to execute the original instruction that
we replaced with the break instruction (normal kprobe flow)
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
|
||
|---|---|---|
| .. | ||
| 8253pit.h | ||
| a.out.h | ||
| acpi.h | ||
| agp.h | ||
| apic.h | ||
| apicdef.h | ||
| atomic.h | ||
| bitops.h | ||
| boot.h | ||
| bootsetup.h | ||
| bug.h | ||
| bugs.h | ||
| byteorder.h | ||
| cache.h | ||
| cacheflush.h | ||
| calling.h | ||
| checksum.h | ||
| compat.h | ||
| cpu.h | ||
| cpufeature.h | ||
| cputime.h | ||
| current.h | ||
| debugreg.h | ||
| delay.h | ||
| desc.h | ||
| div64.h | ||
| dma-mapping.h | ||
| dma.h | ||
| dwarf2.h | ||
| e820.h | ||
| elf.h | ||
| errno.h | ||
| fcntl.h | ||
| fixmap.h | ||
| floppy.h | ||
| fpu32.h | ||
| genapic.h | ||
| hardirq.h | ||
| hdreg.h | ||
| hpet.h | ||
| hw_irq.h | ||
| i387.h | ||
| ia32_unistd.h | ||
| ia32.h | ||
| ide.h | ||
| io_apic.h | ||
| io.h | ||
| ioctl.h | ||
| ioctls.h | ||
| ipcbuf.h | ||
| ipi.h | ||
| irq.h | ||
| kdebug.h | ||
| kmap_types.h | ||
| kprobes.h | ||
| ldt.h | ||
| linkage.h | ||
| local.h | ||
| mach_apic.h | ||
| mc146818rtc.h | ||
| mce.h | ||
| mman.h | ||
| mmsegment.h | ||
| mmu_context.h | ||
| mmu.h | ||
| mmx.h | ||
| mmzone.h | ||
| module.h | ||
| mpspec.h | ||
| msgbuf.h | ||
| msi.h | ||
| msr.h | ||
| mtrr.h | ||
| namei.h | ||
| nmi.h | ||
| node.h | ||
| numa.h | ||
| numnodes.h | ||
| page.h | ||
| param.h | ||
| parport.h | ||
| pci-direct.h | ||
| pci.h | ||
| pda.h | ||
| percpu.h | ||
| pgalloc.h | ||
| pgtable.h | ||
| poll.h | ||
| posix_types.h | ||
| prctl.h | ||
| processor.h | ||
| proto.h | ||
| ptrace.h | ||
| resource.h | ||
| rtc.h | ||
| rwlock.h | ||
| rwsem.h | ||
| scatterlist.h | ||
| seccomp.h | ||
| sections.h | ||
| segment.h | ||
| semaphore.h | ||
| sembuf.h | ||
| serial.h | ||
| setup.h | ||
| shmbuf.h | ||
| shmparam.h | ||
| sigcontext32.h | ||
| sigcontext.h | ||
| siginfo.h | ||
| signal.h | ||
| smp.h | ||
| socket.h | ||
| sockios.h | ||
| sparsemem.h | ||
| spinlock.h | ||
| stat.h | ||
| statfs.h | ||
| string.h | ||
| suspend.h | ||
| swiotlb.h | ||
| system.h | ||
| termbits.h | ||
| termios.h | ||
| thread_info.h | ||
| timex.h | ||
| tlb.h | ||
| tlbflush.h | ||
| topology.h | ||
| types.h | ||
| uaccess.h | ||
| ucontext.h | ||
| unaligned.h | ||
| unistd.h | ||
| user32.h | ||
| user.h | ||
| vga.h | ||
| vsyscall32.h | ||
| vsyscall.h | ||
| xor.h | ||