Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [RFC PATCH v3 08/12] lib: vdso: allow arches to provide vdso data pointer | Date | Thu, 16 Jan 2020 11:35:17 +0100 |
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Christophe Leroy <christophe.leroy@c-s.fr> writes: > Le 15/01/2020 à 07:15, Christophe Leroy a écrit : > From your point of view, what should I do: > A/ __arch_get_vdso_data() handled entirely at arch level and arches > handing over the vdso data pointer to generic C VDSO functions all the > time (as in my v2 series) ?
No. That's again moving the same code to all architectures.
> B/ Data pointer being handed over all the way up for arches wanting to > do so, no changes at all for others (as in my v3 series) ?
Too much ifdeffery
> C/ __arch_get_vdso_data() being called at the outermost generic level > for arches not interested in handling data pointer from the caller (as > suggested by Thomas) ? > > Andy, with A/ you were concerned about arches being able to do PC > related accesses. Would it be an issue for C/ as well ? If not, I guess > C/ would be cleaner than B/ allthought not as clean as A which doesn't > add any #ifdefery at all.
You can avoid ifdeffery with C if you do:
static __maybe_unused int __cvdso_data_clock_gettime(clockid_t clock, struct __kernel_timespec *ts, const struct vdso_data *vd) { ..... }
static __maybe_unused int __cvdso_clock_gettime(clockid_t clock, struct __kernel_timespec *ts) { const struct vdso_data *vd = __arch_get_vdso_data();
return __cvdso_data_clock_gettime(clock, ts, vd); }
and then use __cvdso_data_clock_gettime on PPC and let the other archs unmodified.
Thanks,
tglx
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