Commit 235d074f authored by Huacai Chen's avatar Huacai Chen
Browse files

LoongArch: Support access filter to /dev/mem interface 



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: default avatarWeihao Li <liweihao@loongson.cn>
Signed-off-by: default avatarHuacai Chen <chenhuacai@loongson.cn>
parent b61a40af

arch/loongarch/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -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

arch/loongarch/include/asm/io.h

+4 −0
Original line number Diff line number Diff line
@@ -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 */

arch/loongarch/mm/mmap.c

+29 −0
Original line number Diff line number Diff line
@@ -3,6 +3,8 @@ 
 * Copyright (C) 2020-2022 Loongson Technology Corporation Limited

 */

#include <linux/export.h>

#include <linux/io.h>

#include <linux/memblock.h>

#include <linux/mm.h>

#include <linux/mman.h>
@@ -116,3 +118,30 @@ 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)));

}