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

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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: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
This commit is contained in:
Heiko Carstens 2023-08-25 14:29:50 +02:00
parent 3eeb07788f
commit a6e49f10f4
1 changed files with 5 additions and 2 deletions
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7
arch/s390/mm/vmem.c
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@ -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()) {