问题描述
我正在实现https://apenwarr.ca/log/20190216的变体。长话短说，主要的想法是在内存中留出空间，以便在软重启/出现紧急情况后保留信息并检索该信息。
就我而言，我只想保留一些变量，以免重新引导到另一个变量。因此，我已经研究了此机制的一个简单变体来完成这项工作。该代码只是原始补丁的复制粘贴，并进行了一些原始改编。我添加了一个系统调用以进入内核模式以执行此代码（此处未显示）。
struct logbits {
int magic; /* needed to verify the memory across reboots */
int state;
int nb_reboot;
};
#define PERSIST_SEARCH_START 0
#ifdef CONfig_NO_BOOTMEM
#define PERSIST_SEARCH_END 0x5e000000
#else
#define PERSIST_SEARCH_END 0xfe000000
#endif
#define PERSIST_SEARCH_JUMP (4*1024)
#define PERSIST_MAGIC 0xba5eba11
/*
* arm uses one memory model,mips uses another
*/
phys_addr_t physmem_reserve(phys_addr_t size) {
#ifdef CONfig_NO_BOOTMEM
phys_addr_t alloc;
alloc = memblock_find_in_range_node(size,SMP_CACHE_BYTES,PERSIST_SEARCH_START,PERSIST_SEARCH_END,NUMA_NO_NODE);
if (!alloc) return alloc;
if (memblock_reserve(alloc,size)) {
pr_err("info_keeper: memblock_reserve Failed\n");
return 0;
}
return alloc;
#else
unsigned long where;
for (where = PERSIST_SEARCH_END - size;
where >= PERSIST_SEARCH_START && where <= PERSIST_SEARCH_END - size;
where -= PERSIST_SEARCH_JUMP) {
if (reserve_bootmem(where,size,BOOTMEM_EXCLUSIVE))
continue;
else
return where;
}
return 0;
#endif
}
struct logbits *log_buf_alloc(char **new_logbuf)
{
char *buf;
phys_addr_t alloc;
unsigned long size = sizeof(struct logbits);
unsigned long full_size = size;
struct logbits *new_logbits;
alloc = physmem_reserve(full_size);
if (alloc) {
printk(KERN_INFO "info_keeper: memory reserved @ 0x%08x\n",alloc);
buf = phys_to_virt(alloc);
if(buf){
*new_logbuf = buf;
new_logbits = (void*)buf;
printk(KERN_INFO "info_keeper: memory virtual @ 0x%08x\n",buf);
if (new_logbits->magic != PERSIST_MAGIC) {
printk(KERN_INFO "info_keeper: header invalid," "cleared.\n");
memset(buf,full_size);
memset(new_logbits,sizeof(*new_logbits));
new_logbits->magic = PERSIST_MAGIC;
} else {
printk(KERN_INFO "info_keeper: header valid; " "state=%d\n" "nb_reboot=%d\n",new_logbits->state,new_logbits->nb_reboot);
}
return new_logbits;
}else{
printk(KERN_ERR "info_keeper: Failed to get phys to virt");
buf = alloc_bootmem(full_size);
*new_logbuf = buf;
new_logbits = (struct logbits*)(buf);
memset(buf,full_size);
}
} else {
/* replace the buffer */
printk(KERN_ERR "info_keeper: Failed to reserve bootmem " "area. disabled.\n");
buf = alloc_bootmem(full_size);
*new_logbuf = buf;
new_logbits = (struct logbits*)(buf);
memset(buf,full_size);
}
return new_logbits;
}
执行后，physmem_reserve函数成功并返回一个内存区域。然后，我从phys_to_virt获得了物理到虚拟内存的映射。然后，当我尝试访问内存时，出现此Unable to handle kernel paging request at virtual address错误。
以下是示例输出：
[ 42.489639] info_keeper: memory reserved @ 0x5dffffc0
[ 42.494781] info_keeper: memory virtual @ 0x0dffffc0
[ 42.499778] Unable to handle kernel paging request at virtual address 0dffffc0
有什么想法吗？
解决方法
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