netdev - Re: [PATCH v9 02/11] fprobe: Add ftrace based probe APIs

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Date:   Mon, 7 Mar 2022 23:00:27 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Jiri Olsa <olsajiri@...il.com>
Cc:     Jiri Olsa <jolsa@...hat.com>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, lkml <linux-kernel@...r.kernel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        "Naveen N . Rao" <naveen.n.rao@...ux.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        "David S . Miller" <davem@...emloft.net>
Subject: Re: [PATCH v9 02/11] fprobe: Add ftrace based probe APIs

On Mon, 7 Mar 2022 13:55:31 +0100
Jiri Olsa <olsajiri@...il.com> wrote:

> On Sun, Mar 06, 2022 at 06:36:03PM +0900, Masami Hiramatsu wrote:
> 
> SNIP
> 
> > +}
> > +NOKPROBE_SYMBOL(fprobe_handler);
> > +
> > +/* Convert ftrace location address from symbols */
> > +static unsigned long *get_ftrace_locations(const char **syms, int num)
> > +{
> > +	unsigned long addr, size;
> > +	unsigned long *addrs;
> > +	int i;
> > +
> > +	/* Convert symbols to symbol address */
> > +	addrs = kcalloc(num, sizeof(*addrs), GFP_KERNEL);
> > +	if (!addrs)
> > +		return ERR_PTR(-ENOMEM);
> > +
> > +	for (i = 0; i < num; i++) {
> > +		addrs[i] = kallsyms_lookup_name(syms[i]);
> > +		if (!addrs[i])	/* Maybe wrong symbol */
> > +			goto error;
> > +	}
> > +
> > +	/* Convert symbol address to ftrace location. */
> > +	for (i = 0; i < num; i++) {
> > +		if (!kallsyms_lookup_size_offset(addrs[i], &size, NULL) || !size)
> > +			goto error;
> > +		addr = ftrace_location_range(addrs[i], addrs[i] + size - 1);
> > +		if (!addr) /* No dynamic ftrace there. */
> > +			goto error;
> > +		addrs[i] = addr;
> > +	}
> 
> why not one just single loop ?

Indeed :-D Thanks!

> 
> jirka
> 
> 
> > +
> > +	return addrs;
> > +
> > +error:
> > +	kfree(addrs);
> > +
> > +	return ERR_PTR(-ENOENT);
> > +}
> > +
> > +static void fprobe_init(struct fprobe *fp)
> > +{
> > +	fp->nmissed = 0;
> > +	fp->ops.func = fprobe_handler;
> > +	fp->ops.flags |= FTRACE_OPS_FL_SAVE_REGS;
> > +}
> 
> SNIP


-- 
Masami Hiramatsu <mhiramat@...nel.org>