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

[Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>]

Ping?

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@hitachi.com