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SubjectRe: [PATCH v7 1/3] kprobes/ftrace: Use ftrace_location() when [dis]arming probes
Date
On Wed, 25 Dec 2019 09:42:07 +0000 Jisheng Zhang wrote:
>

oops, I missed "From: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>"

I will take care this point when posting new version.


> Ftrace location could include more than a single instruction in case
> of some architectures (powerpc64, for now). In this case, kprobe is
> permitted on any of those instructions, and uses ftrace infrastructure
> for functioning.
>
> However, [dis]arm_kprobe_ftrace() uses the kprobe address when setting
> up ftrace filter IP. This won't work if the address points to any
> instruction apart from the one that has a branch to _mcount(). To
> resolve this, have [dis]arm_kprobe_ftrace() use ftrace_function() to
> identify the filter IP.
>
> Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
> Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
> ---
> kernel/kprobes.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index 53534aa258a6..5c630b424e3a 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -986,9 +986,10 @@ static int prepare_kprobe(struct kprobe *p)
> static int __arm_kprobe_ftrace(struct kprobe *p, struct ftrace_ops *ops,
> int *cnt)
> {
> + unsigned long ftrace_ip = ftrace_location((unsigned long)p->addr);
> int ret = 0;
>
> - ret = ftrace_set_filter_ip(ops, (unsigned long)p->addr, 0, 0);
> + ret = ftrace_set_filter_ip(ops, ftrace_ip, 0, 0);
> if (ret) {
> pr_debug("Failed to arm kprobe-ftrace at %pS (%d)\n",
> p->addr, ret);
> @@ -1011,7 +1012,7 @@ static int __arm_kprobe_ftrace(struct kprobe *p, struct ftrace_ops *ops,
> * At this point, sinec ops is not registered, we should be sefe from
> * registering empty filter.
> */
> - ftrace_set_filter_ip(ops, (unsigned long)p->addr, 1, 0);
> + ftrace_set_filter_ip(ops, ftrace_ip, 1, 0);
> return ret;
> }
>
> @@ -1028,6 +1029,7 @@ static int arm_kprobe_ftrace(struct kprobe *p)
> static int __disarm_kprobe_ftrace(struct kprobe *p, struct ftrace_ops *ops,
> int *cnt)
> {
> + unsigned long ftrace_ip = ftrace_location((unsigned long)p->addr);
> int ret = 0;
>
> if (*cnt == 1) {
> @@ -1038,7 +1040,7 @@ static int __disarm_kprobe_ftrace(struct kprobe *p, struct ftrace_ops *ops,
>
> (*cnt)--;
>
> - ret = ftrace_set_filter_ip(ops, (unsigned long)p->addr, 1, 0);
> + ret = ftrace_set_filter_ip(ops, ftrace_ip, 1, 0);
> WARN_ONCE(ret < 0, "Failed to disarm kprobe-ftrace at %pS (%d)\n",
> p->addr, ret);
> return ret;
> --
> 2.24.1
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> https://urldefense.proofpoint.com/v2/url?u=http-3A__lists.infradead.org_mailman_listinfo_linux-2Darm-2Dkernel&d=DwICAg&c=7dfBJ8cXbWjhc0BhImu8wQ&r=wlaKTGoVCDxOzHc2QUzpzGEf9oY3eidXlAe3OF1omvo&m=BG5GowWc97yveg-i3gFbh3N7PDT3S3FwcxnpOSRpvIs&s=plWeJUToTNi5CWx998a_VbVx3eFc-MNhUNv4fLpmyiU&e=

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