Accidental access to /dev/mem is obviously disastrous, but specific
access can be used by people debugging the kernel. So select GENERIC_
LIB_DEVMEM_IS_ALLOWED, as well as define ARCH_HAS_VALID_PHYS_ADDR_RANGE
and related helpers, to support access filter to /dev/mem interface.
Signed-off-by: Weihao Li <liweihao@xxxxxxxxxxx>
Signed-off-by: Huacai Chen <chenhuacai@xxxxxxxxxxx>
---
arch/loongarch/Kconfig | 1 +
arch/loongarch/include/asm/io.h | 4 ++++
arch/loongarch/mm/mmap.c | 28 ++++++++++++++++++++++++++++
3 files changed, 33 insertions(+)
diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index fcb5f9489ffd..9c36eb29096a 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -70,6 +70,7 @@ config LOONGARCH
select GENERIC_LIB_CMPDI2
select GENERIC_LIB_LSHRDI3
select GENERIC_LIB_UCMPDI2
+ select GENERIC_LIB_DEVMEM_IS_ALLOWED
select GENERIC_PCI_IOMAP
select GENERIC_SCHED_CLOCK
select GENERIC_SMP_IDLE_THREAD
diff --git a/arch/loongarch/include/asm/io.h b/arch/loongarch/include/asm/io.h
index 999944ea1cea..398d1a7b3dd6 100644
--- a/arch/loongarch/include/asm/io.h
+++ b/arch/loongarch/include/asm/io.h
@@ -107,4 +107,8 @@ extern void __memcpy_fromio(void *to, const volatile void __iomem *from, size_t
#include <asm-generic/io.h>
+#define ARCH_HAS_VALID_PHYS_ADDR_RANGE
+extern int valid_phys_addr_range(phys_addr_t addr, size_t size);
+extern int valid_mmap_phys_addr_range(unsigned long pfn, size_t size);
+
#endif /* _ASM_IO_H */
diff --git a/arch/loongarch/mm/mmap.c b/arch/loongarch/mm/mmap.c
index 381a569635a9..71d45bdffc9e 100644
--- a/arch/loongarch/mm/mmap.c
+++ b/arch/loongarch/mm/mmap.c
@@ -3,6 +3,7 @@
* Copyright (C) 2020-2022 Loongson Technology Corporation Limited
*/
#include <linux/export.h>
+#include <linux/memblock.h>
#include <linux/mm.h>
#include <linux/mman.h>
@@ -116,3 +117,30 @@ int __virt_addr_valid(volatile void *kaddr)
return pfn_valid(PFN_DOWN(PHYSADDR(kaddr)));
}
EXPORT_SYMBOL_GPL(__virt_addr_valid);
+
+/*
+ * You really shouldn't be using read() or write() on /dev/mem. This might go
+ * away in the future.
+ */
+int valid_phys_addr_range(phys_addr_t addr, size_t size)
+{
+ /*
+ * Check whether addr is covered by a memory region without the
+ * MEMBLOCK_NOMAP attribute, and whether that region covers the
+ * entire range. In theory, this could lead to false negatives
+ * if the range is covered by distinct but adjacent memory regions
+ * that only differ in other attributes. However, few of such
+ * attributes have been defined, and it is debatable whether it
+ * follows that /dev/mem read() calls should be able traverse
+ * such boundaries.
+ */
+ return memblock_is_region_memory(addr, size) && memblock_is_map_memory(addr);
+}
+
+/*
+ * Do not allow /dev/mem mappings beyond the supported physical range.
+ */
+int valid_mmap_phys_addr_range(unsigned long pfn, size_t size)
+{
+ return !(((pfn << PAGE_SHIFT) + size) & ~(GENMASK_ULL(cpu_pabits, 0)));
+}
--
2.31.1
