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LoongArch: Support access filter to /dev/mem interface

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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@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
This commit is contained in:
Huacai Chen 2022-10-12 16:36:14 +08:00
parent b61a40afca
commit 235d074fdc
3 changed files with 34 additions and 0 deletions
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1
arch/loongarch/Kconfig
View File

@ -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

4
arch/loongarch/include/asm/io.h
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@ -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 */

29
arch/loongarch/mm/mmap.c
View File

@ -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)));
}