“DevMem note”的版本间的差异
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free6d1823（讨论 | 贡献） |
free6d1823（讨论 | 贡献） |
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| 第53行： | 第53行： | ||
4. mmap to /dev/mem | 4. mmap to /dev/mem | ||
| − | + | offset 如何变成是物理地址? offset 跟vma->pgoff 的关系? | |
| + | vma->vm_start = addr ? 若 addr=NULL 如何给址? | ||
| + | 如何确认offset 合理区域? length 可以有多大? | ||
| − | 5./dev/mem | + | 5./dev/mem driver in inux-kernel/drivers/char/mem.c |
<source lang="c"> | <source lang="c"> | ||
static int mmap_mem(struct file *file, struct vm_area_struct *vma) | static int mmap_mem(struct file *file, struct vm_area_struct *vma) | ||
{ | { | ||
size_t size = vma->vm_end - vma->vm_start; | size_t size = vma->vm_end - vma->vm_start; | ||
| − | + | if (!valid_mmap_phys_addr_range(vma->vm_pgoff, size))//没检查 | |
| − | + | return -EINVAL; | |
| − | + | if (!private_mapping_ok(vma))//vm_flags must have VM_MAYSHARE | |
| − | + | ||
| − | + | ||
| − | + | ||
| − | if (!valid_mmap_phys_addr_range(vma->vm_pgoff, size))return -EINVAL; | + | |
| − | + | ||
| − | if (!private_mapping_ok(vma)) | + | |
return -ENOSYS; | return -ENOSYS; | ||
| − | if (!range_is_allowed(vma->vm_pgoff, size)) | + | if (!range_is_allowed(vma->vm_pgoff, size))//check each page is allowed by calling devmem_is_allowed. ARCH_HAS_VALID_PHYS_ADDR_RANGE |
return -EPERM; | return -EPERM; | ||
if (!phys_mem_access_prot_allowed(file, vma->vm_pgoff, size, | if (!phys_mem_access_prot_allowed(file, vma->vm_pgoff, size, | ||
| − | &vma->vm_page_prot)) | + | &vma->vm_page_prot))//没检查 |
return -EINVAL; | return -EINVAL; | ||
vma->vm_page_prot = phys_mem_access_prot(file, vma->vm_pgoff, | vma->vm_page_prot = phys_mem_access_prot(file, vma->vm_pgoff, | ||
size, | size, | ||
| − | vma->vm_page_prot); | + | vma->vm_page_prot);// 跟 cache 有关 先不管 |
vma->vm_ops = &mmap_mem_ops; | vma->vm_ops = &mmap_mem_ops; | ||
/* Remap-pfn-range will mark the range VM_IO */ | /* Remap-pfn-range will mark the range VM_IO */ | ||
| − | if (remap_pfn_range(vma, | + | if (remap_pfn_range(vma, |
| − | vma->vm_start, | + | vma->vm_start, //Virt 开头位址 |
vma->vm_pgoff, | vma->vm_pgoff, | ||
size, | size, | ||
| 第95行： | 第91行： | ||
} | } | ||
</source> | </source> | ||
| + | remap_pfn_range im ./mm/memory.c | ||
| + | <source lang="c"> | ||
| + | remap_pfn_range(vma, //user vma to map to | ||
| + | addr, //target user address | ||
| + | pfn, //physic address of kernel memory. Page #? | ||
| + | size, //size of map area | ||
| + | prot //page protection flags for this mapping | ||
| + | ) | ||
| + | { | ||
| + | vma->vm_pgoff = pfn; | ||
| + | vma->flags |= VM_IO|VM_PFNMAP|VM_DONTEXPAD |VM_DONTDUMP; | ||
| + | mm = vma->mm; | ||
| + | do { | ||
| + | //for each page, update mm | ||
| + | next = pgd_addr_end(addr, end) | ||
| + | remap_pud_range(mm, pgd, addr, next, pfn+page#, prot) | ||
| + | pgd++, addr = next, | ||
| + | }while (addr != end) | ||
| + | |||
| + | |||
| + | |||
| + | </source> | ||
| + | |||
| + | |||
vm_area_struct结构体 | vm_area_struct结构体 | ||
2019年11月5日 (二) 18:03的版本
1.devmem ADDRESS [WIDTH [VALUE]]
Read/write from physical address ADDRESS Address to act upon WIDTH Width (8/16/...) VALUE Data to be written
2. devmem -> mmap
int devmem_main(int argc UNUSED_PARAM, char **argv) { fd = xopen("/dev/mem", argv[3] ? (O_RDWR | O_SYNC) : (O_RDONLY | O_SYNC)); //根据第三个参数确定是以只读形式打开，还是以读写形式打开。 mapped_size = page_size = getpagesize(); //4K bytes //if cross page, mapped_size *=2 map_base = mmap(NULL, mapped_size, // argv[3] ? (PROT_READ | PROT_WRITE) : PROT_READ, MAP_SHARED, fd, target & ~(off_t)(page_size - 1)//offset from 0x0000, page start address ); virt_addr = (char*)map_base + offset_in_page; }
3. mmap
#include <sys/mman.h> void *mmap(void *addr, size_t length, int prot, int flags, int fd, off_t offset); int munmap(void *addr, size_t length);
详细参数如下:
| 参数 | 详细说明 |
|---|---|
| addr | 需要映射的虚拟内存地址；如果为NULL，系统会自动选定。映射成功后返回该地址 |
| length | 需要映射多大的数据量. Mus be multiple of PAGE SIZE |
| prot | 描述映射区域内存保护方式，包括：PROT_EXEC、PROT_READ、PROT_WRITE、PROT_NONE. |
| flags | 描述映射区域的特性，比如是否对其他进程共享，是否建立匿名映射，是否创建私有的cow. |
| fd | 要映射到内存中的文件描述符 |
| offset | 文件映射的偏移量 |
4. mmap to /dev/mem
offset 如何变成是物理地址? offset 跟vma->pgoff 的关系?
vma->vm_start = addr ? 若 addr=NULL 如何给址?
如何确认offset 合理区域? length 可以有多大?
5./dev/mem driver in inux-kernel/drivers/char/mem.c
static int mmap_mem(struct file *file, struct vm_area_struct *vma) { size_t size = vma->vm_end - vma->vm_start; if (!valid_mmap_phys_addr_range(vma->vm_pgoff, size))//没检查 return -EINVAL; if (!private_mapping_ok(vma))//vm_flags must have VM_MAYSHARE return -ENOSYS; if (!range_is_allowed(vma->vm_pgoff, size))//check each page is allowed by calling devmem_is_allowed. ARCH_HAS_VALID_PHYS_ADDR_RANGE return -EPERM; if (!phys_mem_access_prot_allowed(file, vma->vm_pgoff, size, &vma->vm_page_prot))//没检查 return -EINVAL; vma->vm_page_prot = phys_mem_access_prot(file, vma->vm_pgoff, size, vma->vm_page_prot);// 跟 cache 有关 先不管 vma->vm_ops = &mmap_mem_ops; /* Remap-pfn-range will mark the range VM_IO */ if (remap_pfn_range(vma, vma->vm_start, //Virt 开头位址 vma->vm_pgoff, size, vma->vm_page_prot)) { return -EAGAIN; } return 0; }
remap_pfn_range im ./mm/memory.c
remap_pfn_range(vma, //user vma to map to addr, //target user address pfn, //physic address of kernel memory. Page #? size, //size of map area prot //page protection flags for this mapping ) { vma->vm_pgoff = pfn; vma->flags |= VM_IO|VM_PFNMAP|VM_DONTEXPAD |VM_DONTDUMP; mm = vma->mm; do { //for each page, update mm next = pgd_addr_end(addr, end) remap_pud_range(mm, pgd, addr, next, pfn+page#, prot) pgd++, addr = next, }while (addr != end)
vm_area_struct结构体
