mirror of
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2025-08-05 16:54:27 +00:00
ee417a84d0
The current assumption is that kernel code is always executed with access key zero, which means that storage key protection does not apply. However this assumption is not correct: cmpxchg_user_key() may be executed with a non-zero key; if then the storage key of the page which belongs to the cmpxchg_user_key() code contains a key with fetch-protection enabled the result is a protection exception. For several performance optimizations storage keys are not initialized on system boot. To keep these optimizations add infrastructure which allows to define code ranges within functions which are executed with a non-default key. When such code is executed such functions must explicitly call skey_regions_initialize(). This will initialize all storage keys belonging to such code ranges in a way that no protection exceptions happen when the code is executed with a non-default access key. Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com> Signed-off-by: Heiko Carstens <hca@linux.ibm.com> Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
48 lines
1 KiB
C
48 lines
1 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
|
|
|
#include <asm/rwonce.h>
|
|
#include <asm/page.h>
|
|
#include <asm/skey.h>
|
|
|
|
int skey_regions_initialized;
|
|
|
|
static inline unsigned long load_real_address(unsigned long address)
|
|
{
|
|
unsigned long real;
|
|
|
|
asm volatile(
|
|
" lra %[real],0(%[address])\n"
|
|
: [real] "=d" (real)
|
|
: [address] "a" (address)
|
|
: "cc");
|
|
return real;
|
|
}
|
|
|
|
/*
|
|
* Initialize storage keys of registered memory regions with the
|
|
* default key. This is useful for code which is executed with a
|
|
* non-default access key.
|
|
*/
|
|
void __skey_regions_initialize(void)
|
|
{
|
|
unsigned long address, real;
|
|
struct skey_region *r, *end;
|
|
|
|
r = __skey_region_start;
|
|
end = __skey_region_end;
|
|
while (r < end) {
|
|
address = r->start & PAGE_MASK;
|
|
do {
|
|
real = load_real_address(address);
|
|
page_set_storage_key(real, PAGE_DEFAULT_KEY, 1);
|
|
address += PAGE_SIZE;
|
|
} while (address < r->end);
|
|
r++;
|
|
}
|
|
/*
|
|
* Make sure storage keys are initialized before
|
|
* skey_regions_initialized is changed.
|
|
*/
|
|
barrier();
|
|
WRITE_ONCE(skey_regions_initialized, 1);
|
|
}
|