[PATCH 26/32] s390/mm: Define KMSAN metadata for vmalloc and modules

Ilya Leoshkevich
2023-11-15T20:36:51Z

The pages for the KMSAN metadata associated with most kernel mappings
are taken from memblock by the common code. However, vmalloc and module
metadata needs to be defined by the architectures.

Be a little bit more careful than x86: allocate exactly MODULES_LEN
for the module shadow and origins, and then take 2/3 of vmalloc for
the vmalloc shadow and origins. This ensures that users passing small
vmalloc= values on the command line do not cause module metadata
collisions.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
arch/s390/boot/startup.c | 8 ++++++++
arch/s390/include/asm/pgtable.h | 10 ++++++++++
2 files changed, 18 insertions(+)

diff --git a/arch/s390/boot/startup.c b/arch/s390/boot/startup.c
index 8104e0e3d188..297c1062372a 100644
--- a/arch/s390/boot/startup.c
+++ b/arch/s390/boot/startup.c
@@ -253,9 +253,17 @@ static unsigned long setup_kernel_memory_layout(void)
MODULES_END = round_down(__abs_lowcore, _SEGMENT_SIZE);
MODULES_VADDR = MODULES_END - MODULES_LEN;
VMALLOC_END = MODULES_VADDR;
+#ifdef CONFIG_KMSAN
+ VMALLOC_END -= MODULES_LEN * 2;
+#endif

/* 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));
+#ifdef CONFIG_KMSAN
+ /* take 2/3 of vmalloc area for KMSAN shadow and origins */
+ vmalloc_size = round_down(vmalloc_size / 3, PAGE_SIZE);
+ VMALLOC_END -= vmalloc_size * 2;
+#endif
VMALLOC_START = VMALLOC_END - vmalloc_size;

/* split remaining virtual space between 1:1 mapping & vmemmap array */
diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index 601e87fa8a9a..d764abeb9e6d 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -107,6 +107,16 @@ static inline int is_module_addr(void *addr)
return 1;
}

+#ifdef CONFIG_KMSAN
+#define KMSAN_VMALLOC_SIZE (VMALLOC_END - VMALLOC_START)
+#define KMSAN_VMALLOC_SHADOW_START VMALLOC_END
+#define KMSAN_VMALLOC_ORIGIN_START (KMSAN_VMALLOC_SHADOW_START + \
+ KMSAN_VMALLOC_SIZE)
+#define KMSAN_MODULES_SHADOW_START (KMSAN_VMALLOC_ORIGIN_START + \
+ KMSAN_VMALLOC_SIZE)
+#define KMSAN_MODULES_ORIGIN_START (KMSAN_MODULES_SHADOW_START + MODULES_LEN)
+#endif
+
/*
* A 64 bit pagetable entry of S390 has following format:
* | PFRA |0IPC| OS |
--
2.41.0