On Thu, 17 Feb 2022 17:06:25 +0530
"Naveen N. Rao" <naveen.n....@linux.vnet.ibm.com> wrote:
> On certain architectures, ftrace can reserve multiple instructions at
> function entry. Rather than rejecting kprobe on addresses other than the
> exact ftrace call instruction, use the address returned by ftrace to
> probe at the correct address when CONFIG_KPROBES_ON_FTRACE is enabled.
>
> Signed-off-by: Naveen N. Rao <naveen.n....@linux.vnet.ibm.com>
> ---
> kernel/kprobes.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index 94cab8c9ce56cc..0a797ede3fdf37 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -1497,6 +1497,10 @@ bool within_kprobe_blacklist(unsigned long addr)
> static kprobe_opcode_t *_kprobe_addr(kprobe_opcode_t *addr,
> const char *symbol_name, unsigned int offset)
> {
> +#ifdef CONFIG_KPROBES_ON_FTRACE
> + unsigned long ftrace_addr = 0;
> +#endif
> +
> if ((symbol_name && addr) || (!symbol_name && !addr))
> goto invalid;
>
> @@ -1507,6 +1511,14 @@ static kprobe_opcode_t *_kprobe_addr(kprobe_opcode_t
> *addr,
> }
>
> addr = (kprobe_opcode_t *)(((char *)addr) + offset);
> +
> +#ifdef CONFIG_KPROBES_ON_FTRACE
> + if (addr)
> + ftrace_addr = ftrace_location((unsigned long)addr);
> + if (ftrace_addr)
> + return (kprobe_opcode_t *)ftrace_addr;
As I said, this must be
if (ftrace_addr != addr)
return -EILSEQ;
This will prevent users from being confused by the results of probing
that 'func' and 'func+4' are the same. (now only 'func' is allowed to
be probed.)
Thank you,
> +#endif
> +
> if (addr)
> return addr;
>
> --
> 2.35.1
>
--
Masami Hiramatsu <mhira...@kernel.org>
