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s390/boot: simplify and fix kernel memory layout setup 

Initial KASAN shadow memory range was picked to preserve original kernel
modules area position. With protected execution support, which might
impose addressing limitation on vmalloc area and hence affect modules
area position, current fixed KASAN shadow memory range is only making
kernel memory layout setup more complex. So move it to the very end of
available virtual space and simplify calculations.

At the same time return to previous kernel address space split. In
particular commit 0c4f2623b9 ("s390: setup kernel memory layout
early") introduced precise identity map size calculation and keeping
vmemmap left most starting from a fresh region table entry. This didn't
take into account additional mapping region requirement for potential
DCSS mapping above available physical memory. So go back to virtual
space split between 1:1 mapping & vmemmap array once vmalloc area size
is subtracted.

Cc: stable@vger.kernel.org
Fixes: 0c4f2623b9 ("s390: setup kernel memory layout early")
Reported-by: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
This commit is contained in:
Vasily Gorbik 2021-10-14 13:53:54 +02:00 committed by Heiko Carstens
parent 6ad5f024d1
commit 9a39abb7c9
2 changed files with 32 additions and 58 deletions
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2
arch/s390/Kconfig
View File

@ -47,7 +47,7 @@ config ARCH_SUPPORTS_UPROBES
config KASAN_SHADOW_OFFSET
hex
depends on KASAN
default 0x18000000000000
default 0x1C000000000000
config S390
def_bool y

88
arch/s390/boot/startup.c
View File

@ -149,82 +149,56 @@ static void setup_ident_map_size(unsigned long max_physmem_end)
static void setup_kernel_memory_layout(void)
{
bool vmalloc_size_verified = false;
unsigned long vmemmap_off;
unsigned long vspace_left;
unsigned long vmemmap_start;
unsigned long rte_size;
unsigned long pages;
unsigned long vmax;
pages = ident_map_size / PAGE_SIZE;
/* vmemmap contains a multiple of PAGES_PER_SECTION struct pages */
vmemmap_size = SECTION_ALIGN_UP(pages) * sizeof(struct page);
/* choose kernel address space layout: 4 or 3 levels. */
vmemmap_off = round_up(ident_map_size, _REGION3_SIZE);
vmemmap_start = round_up(ident_map_size, _REGION3_SIZE);
if (IS_ENABLED(CONFIG_KASAN) ||
vmalloc_size > _REGION2_SIZE ||
vmemmap_off + vmemmap_size + vmalloc_size + MODULES_LEN > _REGION2_SIZE)
vmax = _REGION1_SIZE;
else
vmax = _REGION2_SIZE;
/* keep vmemmap_off aligned to a top level region table entry */
rte_size = vmax == _REGION1_SIZE ? _REGION2_SIZE : _REGION3_SIZE;
MODULES_END = vmax;
if (is_prot_virt_host()) {
/*
* forcing modules and vmalloc area under the ultravisor
* secure storage limit, so that any vmalloc allocation
* we do could be used to back secure guest storage.
*/
adjust_to_uv_max(&MODULES_END);
}
#ifdef CONFIG_KASAN
if (MODULES_END < vmax) {
/* force vmalloc and modules below kasan shadow */
MODULES_END = min(MODULES_END, KASAN_SHADOW_START);
vmemmap_start + vmemmap_size + vmalloc_size + MODULES_LEN >
_REGION2_SIZE) {
MODULES_END = _REGION1_SIZE;
rte_size = _REGION2_SIZE;
} else {
/*
* leave vmalloc and modules above kasan shadow but make
* sure they don't overlap with it
*/
vmalloc_size = min(vmalloc_size, vmax - KASAN_SHADOW_END - MODULES_LEN);
vmalloc_size_verified = true;
vspace_left = KASAN_SHADOW_START;
MODULES_END = _REGION2_SIZE;
rte_size = _REGION3_SIZE;
}
/*
* forcing modules and vmalloc area under the ultravisor
* secure storage limit, so that any vmalloc allocation
* we do could be used to back secure guest storage.
*/
adjust_to_uv_max(&MODULES_END);
#ifdef CONFIG_KASAN
/* force vmalloc and modules below kasan shadow */
MODULES_END = min(MODULES_END, KASAN_SHADOW_START);
#endif
MODULES_VADDR = MODULES_END - MODULES_LEN;
VMALLOC_END = MODULES_VADDR;
if (vmalloc_size_verified) {
VMALLOC_START = VMALLOC_END - vmalloc_size;
} else {
vmemmap_off = round_up(ident_map_size, rte_size);
/* allow vmalloc area to occupy up to about 1/2 of the rest virtual space left */
vmalloc_size = min(vmalloc_size, round_down(VMALLOC_END / 2, _REGION3_SIZE));
VMALLOC_START = VMALLOC_END - vmalloc_size;
if (vmemmap_off + vmemmap_size > VMALLOC_END ||
vmalloc_size > VMALLOC_END - vmemmap_off - vmemmap_size) {
/*
* allow vmalloc area to occupy up to 1/2 of
* the rest virtual space left.
*/
vmalloc_size = min(vmalloc_size, VMALLOC_END / 2);
}
VMALLOC_START = VMALLOC_END - vmalloc_size;
vspace_left = VMALLOC_START;
}
pages = vspace_left / (PAGE_SIZE + sizeof(struct page));
/* split remaining virtual space between 1:1 mapping & vmemmap array */
pages = VMALLOC_START / (PAGE_SIZE + sizeof(struct page));
pages = SECTION_ALIGN_UP(pages);
vmemmap_off = round_up(vspace_left - pages * sizeof(struct page), rte_size);
/* keep vmemmap left most starting from a fresh region table entry */
vmemmap_off = min(vmemmap_off, round_up(ident_map_size, rte_size));
/* take care that identity map is lower then vmemmap */
ident_map_size = min(ident_map_size, vmemmap_off);
/* keep vmemmap_start aligned to a top level region table entry */
vmemmap_start = round_down(VMALLOC_START - pages * sizeof(struct page), rte_size);
/* vmemmap_start is the future VMEM_MAX_PHYS, make sure it is within MAX_PHYSMEM */
vmemmap_start = min(vmemmap_start, 1UL << MAX_PHYSMEM_BITS);
/* make sure identity map doesn't overlay with vmemmap */
ident_map_size = min(ident_map_size, vmemmap_start);
vmemmap_size = SECTION_ALIGN_UP(ident_map_size / PAGE_SIZE) * sizeof(struct page);
VMALLOC_START = max(vmemmap_off + vmemmap_size, VMALLOC_START);
vmemmap = (struct page *)vmemmap_off;
/* make sure vmemmap doesn't overlay with vmalloc area */
VMALLOC_START = max(vmemmap_start + vmemmap_size, VMALLOC_START);
vmemmap = (struct page *)vmemmap_start;
}
/*