linux-kernel - Re: [patch 06/11] Text Edit Lock

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Date:	Tue, 13 Nov 2007 22:54:18 +0200
From:	pageexec@...email.hu
To:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org
CC:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [patch 06/11] Text Edit Lock - Alternative code for x86

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)?

> +#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).

> +			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 */


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