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s390/Kconfig: Define non-zero ILLEGAL_POINTER_VALUE

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Define CONFIG_ILLEGAL_POINTER_VALUE to the eye-catching non-zero value
of 0xdead000000000000, consistent with other architectures. Assert at
compile-time that the poison pointers that include/linux/poison.h
defines based on this illegal pointer are beyond the largest useful
virtual addresses. Also, assert at compile-time that the range of poison
pointers per include/linux/poison.h (currently a range of less than
0x10000 addresses) does not overlap with the range used for address
handles for s390's non-MIO PCI instructions.

This enables s390 to track the DMA mappings by the network stack's
page_pool that was introduced with [0]. Other functional changes are not
intended.

Other archictectures have introduced this for various other reasons with
commit 5c178472af ("riscv: define ILLEGAL_POINTER_VALUE for 64bit")
commit f6853eb561 ("powerpc/64: Define ILLEGAL_POINTER_VALUE for 64-bit")
commit bf0c4e0473 ("arm64: kconfig: Move LIST_POISON to a safe value")
commit a29815a333 ("core, x86: make LIST_POISON less deadly")

[0] https://lore.kernel.org/all/20250409-page-pool-track-dma-v9-0-6a9ef2e0cba8@redhat.com/

Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Gerd Bayer <gbayer@linux.ibm.com>
Acked-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
This commit is contained in:
Gerd Bayer 2026-01-16 16:02:42 +01:00 committed by Heiko Carstens
parent 0875816a58
commit 0d453ba040
5 changed files with 12 additions and 0 deletions
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4
Documentation/arch/s390/mm.rst
View File

@ -109,3 +109,7 @@ Virtual memory layout
| KASAN shadow | KASAN untracked
| |
+------------------+ ASCE limit
| |
| CONFIG_ILLEGAL_POINTER_VALUE causes memory access fault
| |
+------------------+

4
arch/s390/Kconfig
View File

@ -719,6 +719,10 @@ config ARCH_SPARSEMEM_ENABLE
config ARCH_SPARSEMEM_DEFAULT
def_bool y
config ILLEGAL_POINTER_VALUE
hex
default 0xdead000000000000
config MAX_PHYSMEM_BITS
int "Maximum size of supported physical memory in bits (42-53)"
range 42 53

1
arch/s390/boot/startup.c
View File

@ -336,6 +336,7 @@ static unsigned long setup_kernel_memory_layout(unsigned long kernel_size)
BUILD_BUG_ON(!IS_ALIGNED(TEXT_OFFSET, THREAD_SIZE));
BUILD_BUG_ON(!IS_ALIGNED(__NO_KASLR_START_KERNEL, THREAD_SIZE));
BUILD_BUG_ON(__NO_KASLR_END_KERNEL > _REGION1_SIZE);
BUILD_BUG_ON(CONFIG_ILLEGAL_POINTER_VALUE < _REGION1_SIZE);
vsize = get_vmem_size(ident_map_size, vmemmap_size, vmalloc_size, _REGION3_SIZE);
boot_debug("vmem size estimated: 0x%016lx\n", vsize);
if (IS_ENABLED(CONFIG_KASAN) || __NO_KASLR_END_KERNEL > _REGION2_SIZE ||

1
arch/s390/include/asm/pci_io.h
View File

@ -18,6 +18,7 @@
#define ZPCI_IOMAP_SHIFT 48
#define ZPCI_IOMAP_ADDR_SHIFT 62
#define ZPCI_IOMAP_ADDR_BASE (1UL << ZPCI_IOMAP_ADDR_SHIFT)
#define ZPCI_IOMAP_ADDR_MAX ((1UL << (ZPCI_IOMAP_ADDR_SHIFT + 1)) - 1)
#define ZPCI_IOMAP_ADDR_OFF_MASK ((1UL << ZPCI_IOMAP_SHIFT) - 1)
#define ZPCI_IOMAP_MAX_ENTRIES \
(1UL << (ZPCI_IOMAP_ADDR_SHIFT - ZPCI_IOMAP_SHIFT))

2
arch/s390/pci/pci.c
View File

@ -1065,6 +1065,8 @@ static int zpci_mem_init(void)
{
BUILD_BUG_ON(!is_power_of_2(__alignof__(struct zpci_fmb)) ||
__alignof__(struct zpci_fmb) < sizeof(struct zpci_fmb));
BUILD_BUG_ON((CONFIG_ILLEGAL_POINTER_VALUE + 0x10000 > ZPCI_IOMAP_ADDR_BASE) &&
(CONFIG_ILLEGAL_POINTER_VALUE <= ZPCI_IOMAP_ADDR_MAX));
zdev_fmb_cache = kmem_cache_create("PCI_FMB_cache", sizeof(struct zpci_fmb),
__alignof__(struct zpci_fmb), 0, NULL);