Messages in this thread | | | Date | Tue, 13 Nov 2007 17:10:12 -0500 | From | Mathieu Desnoyers <> | Subject | Re: [patch 06/11] Text Edit Lock - Alternative code for x86 |
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* pageexec@freemail.hu (pageexec@freemail.hu) wrote: > On 13 Nov 2007 at 13:46, Mathieu Desnoyers wrote: > > > +void *text_poke_early(void *addr, const void *opcode, size_t len) > > +{ > > + memcpy(addr, opcode, len); > > + text_sync(addr, len); > > + return addr; > > +} > > why do you need this function (vs. using text_poke throughout)? >
Because it's not safe to use read_cr0() in paravirtualization before the alternatives are set.
> > +#define kernel_wp_save(cr0) \ > > + do { \ > > + preempt_disable(); \ > > + cr0 = read_cr0(); \ > > + if (cpu_data(smp_processor_id()).wp_works_ok) \ > > why do you need this test? if cr0.wp is ineffective, then it doesn't > matter whether it's on or off (in fact, at least the intel manual > says that 386s would not even let you change its value, they'll > silently ignore attempts of setting the wp bit). >
Ok.. then this test could go away then. I prefered to use a conservative approach. Will fix. Thanks for the hint.
Mathieu
> > + write_cr0(cr0 & ~X86_CR0_WP); \ > > + } while (0) > > + > > +#define kernel_wp_restore(cr0) \ > > + do { \ > > + if (cpu_data(smp_processor_id()).wp_works_ok) \ > > ditto... > > > + write_cr0(cr0); \ > > + preempt_enable(); \ > > + } while (0) > > > > #endif /* _I386_ALTERNATIVE_H */ > >
-- Mathieu Desnoyers Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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