[問題] 請問free分配空間的概念

看板C_and_CPP (C/C++)作者liptonbin (我還存在耶)時間1年前 (2023/04/21 11:02)推噓3(3推 0噓 7→)

留言10則, 3人參與討論串1/1

請教一下兩個問題，如下為什麼path分配空間後,最後面寫kfree(path)會導致crash,這樣寫法是錯的嗎? 另外code寫free_token = token,然後最後kfree(free_token),為什麼要多寫一個指標去free? 謝謝 int test(struct device *dev, const char *p_i8_buf, size_t count) { int i32_ret = 0; char *temp_buf, *token, *path; char *free_temp_buf, *free_token; unsigned long fun = 0; const char *delim = " ,"; temp_buf = kzalloc(RAYDIUM_FW_BIN_PATH_LENGTH + 1, GFP_KERNEL); if (temp_buf == NULL) { return -ENOMEM; } token = kzalloc(RAYDIUM_FW_BIN_PATH_LENGTH + 1, GFP_KERNEL); if (token == NULL) { kfree(temp_buf); return -ENOMEM; } path = kzalloc(RAYDIUM_FW_BIN_PATH_LENGTH + 1, GFP_KERNEL); if (path == NULL) { kfree(temp_buf); kfree(token); return -ENOMEM; } free_token = token; free_temp_buf = temp_buf; strlcpy(temp_buf, p_i8_buf, count); token = strsep(&temp_buf, delim); if(token == NULL) { kfree(free_token); kfree(free_temp_buf); kfree(path); return -EINVAL; } i32_ret = kstrtoul(token, 16, &fun); if (i32_ret < 0) { kfree(free_token); kfree(free_temp_buf); kfree(path); return i32_ret; } path = strsep(&temp_buf, delim);//log path parse(dev, fun, path); kfree(free_token); kfree(free_temp_buf); //kfree(path); //will not crash <----------------- or kfree(path); //will crash<------------------------ return count; } crash log: [ 1316.983483] Unable to handle kernel paging request at virtual address 00005e00 [ 1316.990498] pgd = db59c000 [ 1316.993168] [00005e00] *pgd=00000000 [ 1316.996642] Internal error: Oops: 5 [#1] PREEMPT SMP ARM [ 1317.001840] Modules linked in: drmboot(P) mali_kbase [ 1317.006705] CPU: 3 PID: 1326 Comm: sh Tainted: P 3.10.0 #6612 [ 1317.013355] task: db702a00 ti: db728000 task.ti: db728000 [ 1317.018648] PC is at kmem_cache_alloc_trace+0x7c/0x1c0 [ 1317.023676] LR is at test+0x98/0x2fc [ 1317.028707] pc : [<c0100620>] r : [<c04b39a8>] sr: 20010013 [ 1317.028707] sp : db729eb0 p : 00000000 p : 00000101 [ 1317.039960] r10: 00000f53 9 : 01328000 8 : c04b39a8 2. 通常看到都是寫法3, 我在看很多別人寫的code的寫法都是1,請問是不是改成2才對？ if(!handle)等價if(handle==NULL)嗎？謝謝回答 struct input_handle *handle; (1) handle = kzalloc(sizeof(*handle), GFP_KERNEL); if (!handle) return -ENOMEM; (2) handle = kzalloc(sizeof(*handle), GFP_KERNEL); if (!handle) { kfree(handle); return -ENOMEM; } (3) handle = kzalloc(sizeof(*handle), GFP_KERNEL); if (handle == NULL) { return -ENOMEM; } kfree(handle); ----- Sent from JPTT on my Asus ASUS_Z012DA. -- ※ 發信站: 批踢踢實業坊(ptt.cc), 來自: 1.200.98.254 (臺灣) ※ 文章網址: https://www.ptt.cc/bbs/C_and_CPP/M.1682046179.A.E43.html