Commit a6e49f10 authored by Heiko Carstens's avatar Heiko Carstens
Browse files

s390/mm: improve description of mapping permissions of prefix pages 



Slightly improve the description which explains why the first prefix
page must be mapped executable when the BEAR-enhancement facility is
not installed.

Reviewed-by: default avatarAlexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: default avatarHeiko Carstens <hca@linux.ibm.com>
parent 3eeb0778

arch/s390/mm/vmem.c

+5 −2
Original line number Diff line number Diff line
@@ -659,8 +659,11 @@ void __init vmem_map_init(void) 
		       (unsigned long)(_einittext - _sinittext) >> PAGE_SHIFT);

	set_memory_rox((unsigned long)__stext_amode31,

		       (unsigned long)(__etext_amode31 - __stext_amode31) >> PAGE_SHIFT);



	/* lowcore must be executable for LPSWE */

	/*

	 * If the BEAR-enhancement facility is not installed the first

	 * prefix page is used to return to the previous context with

	 * an LPSWE instruction and therefore must be executable.

	 */

	if (!static_key_enabled(&cpu_has_bear))

		set_memory_x(0, 1);

	if (debug_pagealloc_enabled()) {