Re: swsusp critical code rewritten to assembly

[Linus Torvalds]

On Sun, 10 Nov 2002, Pavel Machek wrote:
> 
> do_magic was really too fragile to be written in C. This patch
> rewrites it into assembly, to make sure C compiler does not generate
> stack access and corrupt memory that way. Plus it cleans up suspend.c
> a bit, makes it really free memory it needs, an no longer calls
> drivers from atomic context.

But this still has stuff in C:

> +	asm volatile ("movl %0, %%esp" :: "m" (saved_context_esp));
> +	asm volatile ("movl %0, %%ebp" :: "m" (saved_context_ebp));
> +	asm volatile ("movl %0, %%eax" :: "m" (saved_context_eax));
> +	asm volatile ("movl %0, %%ebx" :: "m" (saved_context_ebx));
> +	asm volatile ("movl %0, %%ecx" :: "m" (saved_context_ecx));
> +	asm volatile ("movl %0, %%edx" :: "m" (saved_context_edx));
> +	asm volatile ("movl %0, %%esi" :: "m" (saved_context_esi));
> +	asm volatile ("movl %0, %%edi" :: "m" (saved_context_edi));
>  
> -	fix_processor_context();
> +	restore_processor_state();

What's up with that? There's no way you can safely restore regular 
registers and _especially_ %%esp from C code, since the compiler may be 
using them for other things.

		Linus