virt_to_phys on 5.4 kernel

 

virt_to_phys on 5.4 kernel

5.4\arch\arm64\include\asm\Memory.h

static inline phys_addr_t virt_to_phys(const volatile void *x)
{
    return __virt_to_phys((unsigned long)(x));
}

 

#define __is_lm_address(addr)    (((u64)(addr) ^ PAGE_OFFSET) < (PAGE_END - PAGE_OFFSET))

#define __lm_to_phys(addr)    (((addr) & ~PAGE_OFFSET) + PHYS_OFFSET)
#define __kimg_to_phys(addr)    ((addr) - kimage_voffset)

#define __virt_to_phys_nodebug(x) ({                    \
    phys_addr_t __x = (phys_addr_t)(__tag_reset(x));        \
    __is_lm_address(__x) ? __lm_to_phys(__x) : __kimg_to_phys(__x);    \
})

 

PAGE_OFFSET is 0xffffff8000000000, PHYS_OFFSET: 0x0

PAGE_END is 0xffffffc000000000, (PAGE_END - PAGE_OFFSET) is 0x4000000000

 

kimage_voffset计算

arch/arm64/kernel/head.S

ENTRY(kimage_vaddr)
    .quad        _text - TEXT_OFFSET
EXPORT_SYMBOL(kimage_vaddr)

 

 

#define __PHYS_OFFSET    (KERNEL_START - TEXT_OFFSET)
    ldr    x8, =__primary_switched
    adrp    x0, __PHYS_OFFSET
    blr    x8

 

__primary_switched:
    ldr_l    x4, kimage_vaddr        // Save the offset between
    sub    x4, x4, x0            // the kernel virtual and
    str_l    x4, kimage_voffset, x5        // physical mappings

 

x0是调用__primary_switched的第一个参数，为__PHYS_OFFSET，它表示kernel起始物理地址

kernel链接常见macro定义

. KERNEL_START

arch\arm64\include\asm\Memory.h

#define KERNEL_START _text
#define KERNEL_END _end

. TEXT_OFFSET
arch/arm64/Makefile

# The byte offset of the kernel image in RAM from the start of RAM.
ifeq ($(CONFIG_ARM64_RANDOMIZE_TEXT_OFFSET), y)
TEXT_OFFSET := $(shell awk "BEGIN {srand(); printf \"0x%06x\n\", \
         int(2 * 1024 * 1024 / (2 ^ $(CONFIG_ARM64_PAGE_SHIFT)) * \
         rand()) * (2 ^ $(CONFIG_ARM64_PAGE_SHIFT))}")
else
TEXT_OFFSET := 0x00080000
endif