Re: arch_align_stack() seems useless

[Arjan van de Ven <arjan@infradead.org>]

On Mon, 27 Aug 2007 16:08:31 +0200
Franck Bui-Huu <vagabon.xyz@gmail.com> wrote:
> and recently mips do that. Here is the code taken from exec.c which
> calls it:
> 
> 	int setup_arg_pages(struct linux_binprm *bprm,
> 			    unsigned long stack_top,
> 			    int executable_stack)
> 	{
> 		[...]
> 	
> 		stack_top = arch_align_stack(stack_top);
> 		stack_top = PAGE_ALIGN(stack_top);
> 	
> 		[...]
> 	}
> 
> Since PAGE_ALIGN() is called right after arch_align_stack(), it seems
> to me that the call to the latter function is useless...
> 
> Am I missing something ?


arch_align_stack aligns, on x86, within a 2 page range (this is for
cache coloring).  The other thing you missed is that arch_align_stack()
is called in 2 locations, binfmt_elf.c is the primary location for
inside-the-page randomization.