linux arm64 nokaslr内核起始地址随机化

arm64 linux 支持内核起始地址随机化

kallsymbols 得到的符号地址大都是编译阶段就可以决定的，决定于lds链接obj文件的顺序，编译生成obj时会把不同类型的变量放到固定的section内，如下实例 编译环境是cygwin64下的gcc:

uboot 命令:addboot nokaslr

linux 命令: echo 1 > /proc/sys/kernel/kptr_restrict

                cat /proc/kallsymbols |grep "XXX"

多次重启得到的symbol的地址相同即验证成功

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nokaslr 源码位置 :/arch/arm64/kernel/kaslr.c

kaslr_early_init  函数会判断cmdline中有无kaslr参数 如果没有就不进行随机起始地址的计算

说明如下:

/*

 * This routine will be executed with the kernel mapped at its default virtual
 * address, and if it returns successfully, the kernel will be remapped, and
 * start_kernel() will be executed from a randomized virtual offset. The
 * relocation will result in all absolute references (e.g., static variables
 * containing function pointers) to be reinitialized, and zero-initialized
 * .bss variables will be reset to 0.
 */