根據trace到原始的source code部分 proc/fs/generic.c 作者寫到的使用說明： /* * How to be a proc read function * ------------------------------ * Prototype: * int f(char *buffer, char **start, off_t offset, * int count, int *peof, void *dat) * * Assume that the buffer is "count" bytes in size. * * If you know you have supplied all the data you * have, set *peof. * * You have three ways to return data: * 0) Leave *start = NULL. (This is the default.) * Put the data of the requested offset at that * offset within the buffer. Return the number (n) * of bytes there are from the beginning of the * buffer up to the last byte of data. If the * number of supplied bytes (= n - offset) is * greater than zero and you didn't signal eof * and the reader is prepared to take more data * you will be called again with the requested * offset advanced by the number of bytes * absorbed. This interface is useful for files * no larger than the buffer. 這種方法意思是指將要讀出的資料放在第一個參數欄buffer， 而將第二個參數(自訂buffer空間)設為NULL。不過因為buffer 參數的空間大小為PAGE_SIZE，亦即4096KB，所以若我超過此數 值並不適用。 * 1) Set *start = an unsigned long value less than * the buffer address but greater than zero. * Put the data of the requested offset at the * beginning of the buffer. Return the number of * bytes of data placed there. If this number is * greater than zero and you didn't signal eof * and the reader is prepared to take more data * you will be called again with the requested * offset advanced by *start. This interface is * useful when you have a large file consisting * of a series of blocks which you want to count * and return as wholes. * (Hack by [email protected]) 這個方式我就不太明白了，*start通常放的是我的自訂buffer 位置，此部分所指的unsigned long value less than the buffer address意思是？ 不知是否有使用過的前輩舉個例子說明，感謝。 * 2) Set *start = an address within the buffer. * Put the data of the requested offset at *start. * Return the number of bytes of data placed there. * If this number is greater than zero and you * didn't signal eof and the reader is prepared to * take more data you will be called again with the * requested offset advanced by the number of bytes * absorbed. */ ※ 引述《supermin (　)》之銘言： : 我使用kernel-2.6.17，撰寫kernel modules來記錄一些系統資訊， : 使用與user space溝通的機制是/proc，在開完檔案之後指定read function大致如下： : int procfile_read(char *buffer, char **buffer_location, : off_t offset, int buffer_length, int *eof, void *data) : { : if (offset > 0) { : ret = 0; : } else { : *buffer_location = my_buffer; : } : bufferLength = 0; : return bufferLength; : } : 其中my_buffer以及bufferLength為全域變數， : 我想在記錄完一堆東西之後使用cat /proc/myfile來看我記錄的東西 : 不過由於bufferLength頗大，超過10000bytes，而cat的結果被切掉了， : 只能顯示部分內容，顯然應該是buffer overflow的問題， : 這時候該怎麼解決才能看到全部內容呢？ --

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