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SubjectRe: [PATCH v2 1/2] scripts: ftrace - move the sort-processing in ftrace_init to compile time
On Tue, Nov 16, 2021 at 08:42:28PM +0800, Yinan Liu wrote:
>
>
> 在 2021/11/16 下午4:07, Peter Zijlstra 写道:
>
> > /me hands a bucket of {} your way.
>
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -6406,8 +6406,10 @@ static int ftrace_process_locs(struct module *mod,
> if (!count)
> return 0;
>
> - sort(start, count, sizeof(*start),
> - ftrace_cmp_ips, NULL);
> + if (mod) {
> + sort(start, count, sizeof(*start),
> + ftrace_cmp_ips, NULL);
> + }
>
> hi,peter
>
> you mean like this? I hope I'm not mistaken.

Exactly.

>
> > Also, can't sorttable be ran on modules ?
>
> The .ko file will be relocated after insmod or modprobe.
> And the mcount redirection in .ko is based on ".text",
> ".init.text", ".ref.text", ".sched.text", ".spinlock.text",
> ".irqentry .text", ".softirqentry.text", ".kprobes.text", ".cpuidle.text",
> ".text.unlikely". These sections‘ loading
> position are not in definite order.
>
> So sorting this part at compile time doesn't make much sense.

Bah.. I thought the sections would retain relative position at least,
but alas. if that isn't done you're quite right that sorting seems
pointless.

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