| 1 | /* |
| 2 | * Use vmsplice to fill some user memory into a pipe. vmsplice writes |
| 3 | * to stdout, so that must be a pipe. |
| 4 | */ |
| 5 | #include <stdio.h> |
| 6 | #include <stdlib.h> |
| 7 | #include <unistd.h> |
| 8 | #include <limits.h> |
| 9 | #include <string.h> |
| 10 | #include <getopt.h> |
| 11 | #include <sys/poll.h> |
| 12 | #include <sys/types.h> |
| 13 | |
| 14 | #include "splice.h" |
| 15 | |
| 16 | #define PAGE_SIZE 4096 |
| 17 | #define PAGE_MASK (PAGE_SIZE - 1) |
| 18 | |
| 19 | static int alloc_stack; |
| 20 | static int cross_page; |
| 21 | static int force_align; |
| 22 | static int full_page; |
| 23 | static int gift; |
| 24 | |
| 25 | int do_vmsplice(int fd, struct iovec *iov, unsigned long nr_vecs) |
| 26 | { |
| 27 | struct pollfd pfd = { .fd = fd, .events = POLLOUT, }; |
| 28 | long written; |
| 29 | |
| 30 | while (nr_vecs) { |
| 31 | /* |
| 32 | * in a real app you'd be more clever with poll of course, |
| 33 | * here we are basically just blocking on output room and |
| 34 | * not using the free time for anything interesting. |
| 35 | */ |
| 36 | if (poll(&pfd, 1, -1) < 0) |
| 37 | return error("poll"); |
| 38 | |
| 39 | written = svmsplice(fd, iov, nr_vecs, gift ? SPLICE_F_GIFT : 0); |
| 40 | |
| 41 | if (written <= 0) |
| 42 | return error("vmsplice"); |
| 43 | |
| 44 | while (written) { |
| 45 | int this_len = iov->iov_len; |
| 46 | |
| 47 | if (this_len > written) |
| 48 | this_len = written; |
| 49 | |
| 50 | iov->iov_len -= this_len; |
| 51 | if (!iov->iov_len) { |
| 52 | nr_vecs--; |
| 53 | iov++; |
| 54 | } |
| 55 | |
| 56 | written -= this_len; |
| 57 | } |
| 58 | } |
| 59 | |
| 60 | return 0; |
| 61 | } |
| 62 | |
| 63 | static int usage(char *name) |
| 64 | { |
| 65 | fprintf(stderr, "%s [-s(tack)] [-c(ross page)] [-a(lign)] [-f(ull page)] [-g(ift)] | ...\n", name); |
| 66 | return 1; |
| 67 | } |
| 68 | |
| 69 | static int parse_options(int argc, char *argv[]) |
| 70 | { |
| 71 | int c, index = 1; |
| 72 | |
| 73 | while ((c = getopt(argc, argv, "scafg")) != -1) { |
| 74 | switch (c) { |
| 75 | case 's': |
| 76 | alloc_stack = 1; |
| 77 | index++; |
| 78 | break; |
| 79 | case 'c': |
| 80 | cross_page = 1; |
| 81 | index++; |
| 82 | break; |
| 83 | case 'a': |
| 84 | force_align = 1; |
| 85 | index++; |
| 86 | break; |
| 87 | case 'f': |
| 88 | full_page = 1; |
| 89 | index++; |
| 90 | break; |
| 91 | case 'g': |
| 92 | gift = 1; |
| 93 | index++; |
| 94 | break; |
| 95 | default: |
| 96 | return -1; |
| 97 | } |
| 98 | } |
| 99 | |
| 100 | if (cross_page && force_align) { |
| 101 | fprintf(stderr, "Can't get both aligning and cross page spanning\n"); |
| 102 | return -1; |
| 103 | } |
| 104 | |
| 105 | return index; |
| 106 | } |
| 107 | |
| 108 | #define ASIZE (3 * PAGE_SIZE) |
| 109 | #define S1 "header header header header header header header header " |
| 110 | #define S2 "body body body body body body body body body body body " |
| 111 | #define S3 "footer footer footer footer footer footer footer footer" |
| 112 | |
| 113 | static void check_address(void *addr, void *start, void *end, int len,char *msg) |
| 114 | { |
| 115 | if (addr < start || (addr + len - 1) > end) |
| 116 | fprintf(stderr, "%s: bad: %p < %p < %p false\n", msg, start, addr, end); |
| 117 | } |
| 118 | |
| 119 | int main(int argc, char *argv[]) |
| 120 | { |
| 121 | struct iovec vecs[3]; |
| 122 | char stack1[ASIZE], stack2[ASIZE], stack3[ASIZE]; |
| 123 | char *h_s, *h_e, *b_s, *b_e, *f_s, *f_e; |
| 124 | char *h, *b, *f; |
| 125 | |
| 126 | if (check_output_pipe()) |
| 127 | return usage(argv[0]); |
| 128 | |
| 129 | if (parse_options(argc, argv) < 0) |
| 130 | return usage(argv[0]); |
| 131 | |
| 132 | if (alloc_stack) { |
| 133 | h = stack1; |
| 134 | b = stack2; |
| 135 | f = stack3; |
| 136 | } else { |
| 137 | h = malloc(ASIZE); |
| 138 | b = malloc(ASIZE); |
| 139 | f = malloc(ASIZE); |
| 140 | } |
| 141 | |
| 142 | memset(h, 0, ASIZE); |
| 143 | memset(b, 0, ASIZE); |
| 144 | memset(f, 0, ASIZE); |
| 145 | |
| 146 | h_s = h; |
| 147 | h_e = h_s + 2 * PAGE_SIZE - 1; |
| 148 | b_s = b; |
| 149 | b_e = b_s + 2 * PAGE_SIZE - 1; |
| 150 | f_s = f; |
| 151 | f_e = f_s + 2 * PAGE_SIZE - 1; |
| 152 | |
| 153 | if (force_align || cross_page) { |
| 154 | /* align forward to start of 2nd page */ |
| 155 | unsigned long off; |
| 156 | |
| 157 | off = PAGE_SIZE - ((unsigned long) h & PAGE_MASK); |
| 158 | h += off; |
| 159 | off = PAGE_SIZE - ((unsigned long) b & PAGE_MASK); |
| 160 | b += off; |
| 161 | off = PAGE_SIZE - ((unsigned long) f & PAGE_MASK); |
| 162 | f += off; |
| 163 | if (cross_page) { |
| 164 | /* this puts half the string in both pages */ |
| 165 | h -= strlen(S1) / 2; |
| 166 | b -= strlen(S2) / 2; |
| 167 | f -= strlen(S3) / 2; |
| 168 | } |
| 169 | } |
| 170 | |
| 171 | strcpy(h, S1); |
| 172 | strcpy(b, S2); |
| 173 | strcpy(f, S3); |
| 174 | |
| 175 | vecs[0].iov_base = h; |
| 176 | vecs[1].iov_base = b; |
| 177 | vecs[2].iov_base = f; |
| 178 | if (!full_page) { |
| 179 | vecs[0].iov_len = strlen(vecs[0].iov_base); |
| 180 | vecs[1].iov_len = strlen(vecs[1].iov_base); |
| 181 | vecs[2].iov_len = strlen(vecs[2].iov_base); |
| 182 | } else { |
| 183 | vecs[0].iov_len = PAGE_SIZE; |
| 184 | vecs[1].iov_len = PAGE_SIZE; |
| 185 | vecs[2].iov_len = PAGE_SIZE; |
| 186 | } |
| 187 | |
| 188 | check_address(h, h_s, h_e, vecs[0].iov_len, "header"); |
| 189 | check_address(b, b_s, b_e, vecs[1].iov_len, "body"); |
| 190 | check_address(f, f_s, f_e, vecs[2].iov_len, "footer"); |
| 191 | |
| 192 | return do_vmsplice(STDOUT_FILENO, vecs, 3); |
| 193 | } |