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1// SPDX-License-Identifier: GPL-2.02#include <unistd.h>3#include <stdbool.h>4#include <errno.h>5#include <linux/kernel.h>6#include <internal/lib.h>7 8unsigned int page_size;9 10static ssize_t ion(bool is_read, int fd, void *buf, size_t n)11{12 void *buf_start = buf;13 size_t left = n;14 15 while (left) {16 /* buf must be treated as const if !is_read. */17 ssize_t ret = is_read ? read(fd, buf, left) :18 write(fd, buf, left);19 20 if (ret < 0 && errno == EINTR)21 continue;22 if (ret <= 0)23 return ret;24 25 left -= ret;26 buf += ret;27 }28 29 BUG_ON((size_t)(buf - buf_start) != n);30 return n;31}32 33/*34 * Read exactly 'n' bytes or return an error.35 */36ssize_t readn(int fd, void *buf, size_t n)37{38 return ion(true, fd, buf, n);39}40 41ssize_t preadn(int fd, void *buf, size_t n, off_t offs)42{43 size_t left = n;44 45 while (left) {46 ssize_t ret = pread(fd, buf, left, offs);47 48 if (ret < 0 && errno == EINTR)49 continue;50 if (ret <= 0)51 return ret;52 53 left -= ret;54 buf += ret;55 offs += ret;56 }57 58 return n;59}60 61/*62 * Write exactly 'n' bytes or return an error.63 */64ssize_t writen(int fd, const void *buf, size_t n)65{66 /* ion does not modify buf. */67 return ion(false, fd, (void *)buf, n);68}69