差異處
這裏顯示兩個版本的差異處。
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cpp:linux_kernel:show_physical_address [2017/10/14 16:38] tony [Introduction] |
cpp:linux_kernel:show_physical_address [2023/06/25 09:48] |
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| - | ====== Show Physical Memory Address of the kernel module ====== | ||
| - | ===== Introduction ===== | ||
| - | 我希望透過寫一個kernel module，透過user space的操作，去顯示某個變數值的實體記憶體位置與數值。 | ||
| - | \\ | ||
| - | Note: 由於這程式僅用於測試，因此不會特別去考慮更好的寫法；會補充這點是由於看書有看到更好的寫法。 | ||
| - | ===== How to? ===== | ||
| - | ==== Source Code ==== | ||
| - | 包含以下內容: | ||
| - | - 在init時，我建立一個字元裝置用以接受user space的操作，並初始hello_buf。 | ||
| - | - 當使用者執行cat /dev/hello時，會觸發file_operations的open與release，這裡我只實做open的對應行為: dump_physical_address。 | ||
| - | - dump_physical_address則是取得hello_buf的實體記憶體位置並dump出來。 | ||
| - | - exit就是釋放所有用到的資源。 | ||
| - | <code cpp> | ||
| - | #include <linux/init.h> | ||
| - | #include <linux/module.h> | ||
| - | #include <linux/slab.h> | ||
| - | #include <linux/string.h> | ||
| - | #include <asm/io.h> | ||
| - | #include <linux/fs.h> | ||
| - | |||
| - | MODULE_LICENSE("Dual BSD/GPL"); | ||
| - | |||
| - | static char* hello_buf; | ||
| - | |||
| - | static int dump_physical_address(struct file *filp, struct vm_area_struct *vma) | ||
| - | { | ||
| - | unsigned long virt_addr; | ||
| - | phys_addr_t phy_addr; | ||
| - | printk("damn\n"); | ||
| - | virt_addr = (unsigned long)hello_buf; | ||
| - | printk("Hello kernel: %lx, value: %c\n", virt_addr, hello_buf[0]); | ||
| - | phy_addr = virt_to_phys((void*)virt_addr); | ||
| - | printk("PA: 0x%lx\n", phy_addr); | ||
| - | pr_info("PA: %pa for VA: 0x%lx\n", &phy_addr, virt_addr); | ||
| - | return 0; | ||
| - | } | ||
| - | |||
| - | static struct file_operations hello_fops = { | ||
| - | open: dump_physical_address, | ||
| - | }; | ||
| - | |||
| - | static int hello_init(void) | ||
| - | { | ||
| - | |||
| - | int ret = register_chrdev(187, "hello", &hello_fops); | ||
| - | if(ret<0) { | ||
| - | printk("Unsable to register char device %d\n", ret); | ||
| - | return ret; | ||
| - | } | ||
| - | |||
| - | hello_buf = kmalloc(256, GFP_KERNEL); | ||
| - | memset(hello_buf,'*',256); | ||
| - | printk("Hello kernel: %c\n", hello_buf[0]); | ||
| - | return 0; | ||
| - | } | ||
| - | static void hello_exit(void) | ||
| - | { | ||
| - | if(hello_buf) { | ||
| - | printk("Goodbyte kernel: %c\n", hello_buf[0]); | ||
| - | kfree(hello_buf); | ||
| - | } | ||
| - | unregister_chrdev(187,"hello"); | ||
| - | printk(KERN_INFO "Goodbye\n"); | ||
| - | } | ||
| - | |||
| - | module_init(hello_init); | ||
| - | module_exit(hello_exit); | ||
| - | </code> | ||
| - | ==== Makefile ==== | ||
| - | <code> | ||
| - | # | ||
| - | ## Makefile for kernel test | ||
| - | # | ||
| - | #PWD := $(shell pwd) | ||
| - | KVERSION := $(shell uname -r) | ||
| - | KERNEL_DIR = /usr/src/kernels/$(KVERSION)/ | ||
| - | MODULE_NAME = hello | ||
| - | obj-m := $(MODULE_NAME).o | ||
| - | all: | ||
| - | make -C $(KERNEL_DIR) M=$(PWD) modules | ||
| - | clean: | ||
| - | make -C $(KERNEL_DIR) M=$(PWD) clean | ||
| - | </code> | ||
| - | ==== Test Script ==== | ||
| - | <code bash> | ||
| - | #!/bin/bash | ||
| - | |||
| - | #mknod /dev/hello c 187 0 | ||
| - | |||
| - | rmmod hello | ||
| - | insmod hello.ko | ||
| - | cat /dev/hello | ||
| - | dmesg | tail | ||
| - | </code> | ||
| - | ===== Reference ===== | ||
| - | * [[https://wwssllabcd.github.io/blog/2012/11/13/how-to-make-linux-module/|一個簡單的 Linux Kernel Module]] | ||
| - | * [[https://github.com/torvalds/linux/blob/master/lib/test_debug_virtual.c|virt_to_phys sample]] | ||
| - | * [[http://blog.csdn.net/freenaut/article/details/4298174|字符设备 register_chrdev_region()、alloc_chrdev_region() 和 register_chrdev()]] | ||
| - | |||
