161 lines
3.5 KiB
C
161 lines
3.5 KiB
C
/*
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* Tool for reading QEMU fwcfg values.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <stddef.h>
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#include <stdint.h>
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#include <string.h>
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#include <unistd.h>
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#include <getopt.h>
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#define FW_CFG_PORT_OUT 0x510
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#define FW_CFG_PORT_IN 0x511
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#define FW_CFG_SELECT_QEMU 0x0000
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#define FW_CFG_SELECT_LIST 0x0019
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/* outw / inb helper functions */
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static void outports(unsigned short _port, unsigned short _data) {
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asm volatile ("outw %1, %0" : : "dN" (_port), "a" (_data));
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}
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static unsigned char inportb(unsigned short _port) {
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unsigned char rv;
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asm volatile ("inb %1, %0" : "=a" (rv) : "dN" (_port));
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return rv;
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}
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/* Despite primarily emulating x86, these are all big-endian */
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static void swap_bytes(void * in, int count) {
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char * bytes = in;
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if (count == 4) {
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uint32_t * t = in;
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*t = (bytes[0] << 24) | (bytes[1] << 12) | (bytes[2] << 8) | bytes[3];
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} else if (count == 2) {
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uint16_t * t = in;
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*t = (bytes[0] << 8) | bytes[1];
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}
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}
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/* Layout of the information returned from the fw_cfg port */
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struct fw_cfg_file {
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uint32_t size;
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uint16_t select;
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uint16_t reserved;
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char name[56];
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};
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static int usage(char * argv[]) {
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printf(
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"Obtain QEMU fw_cfg values\n"
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"\n"
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"usage: %s [-?ln] [config name]\n"
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"\n"
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" -l \033[3mlist available config entries\033[0m\n"
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" -n \033[3mdon't print a new line after image\033[0m\n"
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" -? \033[3mshow this help text\033[0m\n"
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"\n", argv[0]);
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return 1;
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}
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int main(int argc, char * argv[]) {
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uint32_t count = 0;
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uint8_t * bytes = (uint8_t *)&count;
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int found = 0;
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struct fw_cfg_file file;
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uint8_t * tmp = (uint8_t *)&file;
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int opt = 0;
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int list = 0;
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int no_newline = 0;
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int query_quietly = 0;
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while ((opt = getopt(argc, argv, "?lnq")) != -1) {
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switch (opt) {
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case '?':
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return usage(argv);
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case 'n':
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no_newline = 1;
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break;
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case 'q':
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query_quietly = 1;
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break;
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case 'l':
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list = 1;
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break;
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}
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}
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if (optind >= argc && !list) {
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return usage(argv);
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}
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/* First check for QEMU */
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outports(FW_CFG_PORT_OUT, FW_CFG_SELECT_QEMU);
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if (inportb(FW_CFG_PORT_IN) != 'Q' ||
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inportb(FW_CFG_PORT_IN) != 'E' ||
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inportb(FW_CFG_PORT_IN) != 'M' ||
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inportb(FW_CFG_PORT_IN) != 'U') {
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fprintf(stderr, "%s: this doesn't seem to be qemu\n", argv[0]);
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return 1;
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}
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/* Then get the list of "files" so we can look at names */
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outports(FW_CFG_PORT_OUT, FW_CFG_SELECT_LIST);
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for (int i = 0; i < 4; ++i) {
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bytes[i] = inportb(FW_CFG_PORT_IN);
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}
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swap_bytes(&count, sizeof(count));
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for (unsigned int i = 0; i < count; ++i) {
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/* read one file entry */
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for (unsigned int j = 0; j < sizeof(struct fw_cfg_file); ++j) {
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tmp[j] = inportb(FW_CFG_PORT_IN);
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}
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/* endian swap to get file size and selector ID */
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swap_bytes(&file.size, sizeof(file.size));
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swap_bytes(&file.select, sizeof(file.select));
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if (list) {
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/* 0x0020 org/whatever (1234 bytes) */
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fprintf(stdout, "0x%04x %s (%d byte%s)\n", file.select, file.name, (int)file.size, file.size == 1 ? "" : "s");
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} else {
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if (!strcmp(file.name, argv[optind])) {
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/* found the requested file */
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found = 1;
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break;
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}
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}
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}
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if (query_quietly) {
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return !found;
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}
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if (found) {
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/* if we found the requested file, read it from the port */
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outports(FW_CFG_PORT_OUT, file.select);
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for (unsigned int i = 0; i < file.size; ++i) {
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fputc(inportb(FW_CFG_PORT_IN), stdout);
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}
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if (!no_newline) {
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fprintf(stdout, "\n");
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} else {
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fflush(stdout);
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}
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} else if (!list) {
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fprintf(stderr, "%s: config option not found\n", argv[0]);
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return 1;
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}
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return 0;
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}
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