Re: (ltc-kernel 9786) [PATCH ftrace/core v4 0/4] ftrace, kprobes: Introduce IPMODIFY flag for ftrace_ops to detect conflicts

[Josh Poimboeuf]

On Fri, Aug 08, 2014 at 08:05:13PM +0900, Masami Hiramatsu wrote:
> Ping?

For the series:

Tested-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>

> 
> BTW, I'd like to add this testcase if ftracetest is accepted.
> 
> Thank you,
> 
> (2014/07/28 14:22), Masami Hiramatsu wrote:
> > Hi,
> > 
> > Here is the 4th version 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.
> > This version is basically an update of previous version, and
> > I've splitted a patch which adding IPMODIFY to kprobes from ftrace
> > IPMODIFY introducing patch.
> > 
> > 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 ftrace_ops with IPMODIFY flag requires at least one
> > entry for filter hash, and its notrace_hash must be empty,
> > because the IPMODIFY action is very address sensitve and
> > user must consider the ip address.
> > 
> > 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. 
> > 
> > Here is the new testcase.
> > -------
> > #!/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 target=$ADDR && echo "Case1: [FAIL]" || echo "Case1: [OK]"
> > rmmod kprobe_example jprobe_example
> > 
> > echo "Case2: jprobe->kprobe->ipmodify(fail)"
> > modprobe jprobe_example
> > modprobe kprobe_example
> > insmod ./ipmodify.ko target=$ADDR && echo "Case2: [FAIL]" || echo "Case2: [OK]"
> > rmmod kprobe_example jprobe_example
> > 
> > echo "Case3: jprobe->ipmodify(fail)"
> > modprobe jprobe_example
> > insmod ./ipmodify.ko target=$ADDR && echo "Case3: [FAIL]" || echo "Case3: [OK]"
> > rmmod jprobe_example
> > 
> > echo "Case4: ipmodify->jprobe(fail)"
> > insmod ./ipmodify.ko target=$ADDR
> > modprobe jprobe_example && echo "Case4: [FAIL]" || echo "Case4: [OK]"
> > rmmod ipmodify
> > 
> > echo "Case5: ipmodify->kprobe->jprobe(fail)"
> > insmod ./ipmodify.ko target=$ADDR
> > modprobe kprobe_example
> > modprobe jprobe_example && echo "Case5: [FAIL]" || echo "Case5: [OK]"
> > rmmod ipmodify kprobe_example
> > 
> > echo "Case6: ipmodify with targeting all functions(fail)"
> > insmod ./ipmodify.ko && echo "Case6: [FAIL]" || echo "Case6: [OK]"
> > rmmod ipmodify
> > 
> > echo "Case7: ipmodify with notrace filter (fail)"
> > insmod ./ipmodify.ko target=$ADDR noexp="do_fork" && echo "Case7: [FAIL]" || echo "Case7: [OK]"
> > rmmod ipmodify
> > -------
> > 
> > And ipmodify.c
> > -------
> > #include <linux/kernel.h>
> > #include <linux/module.h>
> > #include <linux/ftrace.h>
> > 
> > 
> > static void ftrace_ipmodify_handler(unsigned long a0, unsigned long a1,
> >                                 struct ftrace_ops *op, struct pt_regs *regs)
> > {
> >         return;
> > }
> > 
> > static struct ftrace_ops test_ops __read_mostly = {
> >         .func = ftrace_ipmodify_handler,
> >         .flags = FTRACE_OPS_FL_SAVE_REGS | FTRACE_OPS_FL_IPMODIFY,
> > };
> > 
> > static unsigned long target;
> > module_param(target, ulong, 0444);
> > static char *noexp = "";
> > module_param(noexp, charp, 0444);
> > 
> > static int __init ipmodify_init(void)
> > {
> >         int ret;
> >         unsigned long ip = target;
> > 
> >         if (strlen(noexp) != 0) {
> >                 ret = ftrace_set_notrace(&test_ops, noexp, 0, 0);
> >                 pr_err("ipmodify_test: set notrace \"%s\", ret = %d\n",
> >                         noexp, ret);
> >         }
> >         if (ret < 0)
> >                 return ret;
> > 
> >         ret = ftrace_set_filter_ip(&test_ops, ip, 0, 0);
> >         pr_err("ipmodify_test: set filter ip 0x%lx, ret = %d\n", ip, ret);
> > 
> >         if (ret >= 0) {
> >                 ret = register_ftrace_function(&test_ops);
> >                 pr_err("ipmodify_test: register ftrace on 0x%lx, ret = %d\n",
> >                         ip, ret);
> >         }
> > 
> >         return ret;
> > }
> > 
> > static void __exit ipmodify_exit(void)
> > {
> >         int ret;
> >         unsigned long ip = target;
> > 
> >         ret = unregister_ftrace_function(&test_ops);
> >         pr_err("ipmodify_test: unregister ftrace on 0x%lx, ret = %d\n", ip, ret);
> >         if (ret >= 0) {
> >                 ret = ftrace_set_filter_ip(&test_ops, ip, 1, 0);
> >                 pr_err("ipmodify_test: clear filter ip 0x%lx, ret = %d\n",
> >                         ip, ret);
> >         }
> > }
> > 
> > module_init(ipmodify_init)
> > module_exit(ipmodify_exit)
> > MODULE_LICENSE("GPL");
> > -------
> > 
> > Thank you,
> > 
> > ---
> > 
> > Masami Hiramatsu (4):
> >       kprobes/ftrace: Recover original IP if pre_handler doesn't change it
> >       ftrace, kprobes: Support IPMODIFY flag to find IP modify conflict
> >       kprobes: Add IPMODIFY flag to kprobe_ftrace_ops
> >       kprobes: Set IPMODIFY flag only if the probe can change regs->ip
> > 
> > 
> >  Documentation/kprobes.txt        |   12 +--
> >  Documentation/trace/ftrace.txt   |    5 +
> >  arch/x86/kernel/kprobes/ftrace.c |    9 ++
> >  include/linux/ftrace.h           |   16 ++++
> >  kernel/kprobes.c                 |  123 +++++++++++++++++++++++++++++----
> >  kernel/trace/ftrace.c            |  143 +++++++++++++++++++++++++++++++++++++-
> >  6 files changed, 279 insertions(+), 29 deletions(-)
> > 
> > --
> > 
> > 
> 
> 
> -- 
> Masami HIRAMATSU
> IT Management Research Dept. Linux Technology Center
> Hitachi, Ltd., Yokohama Research Laboratory
> E-mail: masami.hiramatsu.pt@xxxxxxxxxxx
> 
> 

-- 
Josh
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