(2014/06/17 20:04), Masami Hiramatsu wrote: > Hi, > > Here is the version 2 of the series of patches which introduces > IPMODIFY flag for ftrace_ops to detect conflicts of ftrace users > who can modify regs->ip in their handler. > In this version, I fixed some bugs in previous version and > added a patch which made kprobe itself free from IPMODIFY > except for jprobe. > > Currently, only kprobes can change the regs->ip in the handler, > but recently kpatch is also want to change it. Moreover, since > the ftrace itself exported to modules, it might be considerable > senario. > > Here we talked on github. > https://github.com/dynup/kpatch/issues/47 > > To protect modified regs-ip from each other, this series > introduces FTRACE_OPS_FL_IPMODIFY flag and ftrace now ensures > the flag can be set on each function entry location. If there > is someone who already reserve regs->ip on target function > entry, ftrace_set_filter_ip or register_ftrace_function will > return -EBUSY. Users must handle that. > > The 3rd patch adds a special reservation of IPMODIFY on the > jprobed address, since it is the only user who will change > the regs->ip. Other kprobes do not change it anymore. > > Testing: > BTW, I've tested it with samples/kprobes/{k,j}probe_example.ko > and a small test module which I added to the last of this mail. > > Here is the test script. I think I should put this under > tools/testing, maybe kprobes? or selftest/kprobes? > > ---- > #!/bin/bash > > echo "IPMODIFY test" > ADDR=0x`grep do_fork /proc/kallsyms | cut -f 1 -d" "` > > echo "Case1: kprobe->jprobe->ipmodify(fail)" > modprobe kprobe_example > modprobe jprobe_example > insmod ./ipmodify.ko && echo "Case1: [FAIL]" || echo "Case1: [OK]"
Oops, I missed the target=$ADDR for these insmod... Anyway, without passing target=$ADDR option, ipmodify.ko tries to register ftrace_ops with an empty filter hash which means trace all functions. So anyway jprobe and that ftrace_ops collide with each other on the do_fork and the 2nd one should be failed. Thus, of course this test doesn't fail with or without target= param. Thank you, -- Masami HIRAMATSU IT Management Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: [email protected] -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
