Hi Thomas,
On Fri, 20 Mar 2020 19:00:00 +0100
Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> Instrumentation is forbidden in the .noinstr.text section. Make kprobes
> respect this.
>
> This lacks support for .noinstr.text sections in modules, which is required
> to handle VMX and SVM.
>
Would you have any plan to list or mark the noinstr symbols on
some debugfs interface? I need a blacklist of those symbols so that
user (and perf-probe) can check which function can not be probed.
It is just calling kprobe_add_area_blacklist() like below.
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 2625c241ac00..4835b644bd2b 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -2212,6 +2212,10 @@ static int __init populate_kprobe_blacklist(unsigned long *start,
ret = kprobe_add_area_blacklist((unsigned long)__kprobes_text_start,
(unsigned long)__kprobes_text_end);
+ /* Symbols in noinstr section are blacklisted */
+ ret = kprobe_add_area_blacklist((unsigned long)__noinstr_text_start,
+ (unsigned long)__noinstr_text_end);
+
return ret ? : arch_populate_kprobe_blacklist();
}
Thank you,
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> ---
> kernel/kprobes.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -1443,10 +1443,21 @@ static bool __within_kprobe_blacklist(un
> return false;
> }
>
> +/* Functions in .noinstr.text must not be probed */
> +static bool within_noinstr_text(unsigned long addr)
> +{
> + /* FIXME: Handle module .noinstr.text */
> + return addr >= (unsigned long)__noinstr_text_start &&
> + addr < (unsigned long)__noinstr_text_end;
> +}
> +
> bool within_kprobe_blacklist(unsigned long addr)
> {
> char symname[KSYM_NAME_LEN], *p;
>
> + if (within_noinstr_text(addr))
> + return true;
> +
> if (__within_kprobe_blacklist(addr))
> return true;
>
>
--
Masami Hiramatsu <mhiramat@xxxxxxxxxx>
