diff options
| -rw-r--r-- | arch/s390/Kconfig | 13 | ||||
| -rw-r--r-- | arch/s390/boot/startup.c | 3 |
2 files changed, 15 insertions, 1 deletions
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index a822f952f64a..c60e699e99f5 100644 --- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -604,6 +604,19 @@ config RANDOMIZE_BASE as a security feature that deters exploit attempts relying on knowledge of the location of kernel internals. +config RANDOMIZE_IDENTITY_BASE + bool "Randomize the address of the identity mapping base" + depends on RANDOMIZE_BASE + default DEBUG_VM + help + The identity mapping base address is pinned to zero by default. + Allow randomization of that base to expose otherwise missed + notion of physical and virtual addresses of data structures. + That does not have any impact on the base address at which the + kernel image is loaded. + + If unsure, say N + config KERNEL_IMAGE_BASE hex "Kernel image base address" range 0x100000 0x1FFFFFE0000000 if !KASAN diff --git a/arch/s390/boot/startup.c b/arch/s390/boot/startup.c index ce232552bc1c..cff34744b5a9 100644 --- a/arch/s390/boot/startup.c +++ b/arch/s390/boot/startup.c @@ -341,7 +341,8 @@ static unsigned long setup_kernel_memory_layout(unsigned long kernel_size) BUILD_BUG_ON(MAX_DCSS_ADDR > (1UL << MAX_PHYSMEM_BITS)); max_mappable = max(ident_map_size, MAX_DCSS_ADDR); max_mappable = min(max_mappable, vmemmap_start); - __identity_base = round_down(vmemmap_start - max_mappable, rte_size); + if (IS_ENABLED(CONFIG_RANDOMIZE_IDENTITY_BASE)) + __identity_base = round_down(vmemmap_start - max_mappable, rte_size); return asce_limit; } |