util/nvmutil: add useful code comments
Leah Rowe
parent
7c403fcd9b
commit
d3ad50dcb4
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@ -21,6 +21,11 @@
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* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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/*
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* This file is part of the Libreboot project. Documentation available here:
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* https://libreboot.org/docs/install/nvmutil.html
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*/
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#include <stdint.h>
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#include <string.h>
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#include <stdlib.h>
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@ -78,33 +83,33 @@ main(int argc, char *argv[])
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const char *strMac = NULL, *strRMac = "??:??:??:??:??:??";
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#ifdef HAVE_PLEDGE
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if (pledge("stdio wpath", NULL) == -1)
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err(errno, "pledge");
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if (pledge("stdio wpath", NULL) == -1) /* only used on openbsd */
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err(errno, "pledge"); /* https://man.openbsd.org/pledge.2 */
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#endif
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buf = (uint8_t *) &buf16;
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gbe[1] = (gbe[0] = (size_t) buf) + SIZE_4KB;
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test = 1;
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big_endian = ((uint8_t *) &test)[0] ^ 1;
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big_endian = ((uint8_t *) &test)[0] ^ 1; /* check host endianness */
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if (argc == 3) {
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if (strcmp(COMMAND, "dump") == 0) {
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#ifdef HAVE_PLEDGE
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if (pledge("stdio rpath", NULL) == -1)
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err(errno, "pledge");
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err(errno, "pledge"); /* not very puffy */
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#endif
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flags = O_RDONLY;
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cmd = &cmd_dump;
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} else if (strcmp(COMMAND, "setmac") == 0)
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strMac = (char *) strRMac;
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strMac = (char *) strRMac; /* random mac address */
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else if (strcmp(COMMAND, "swap") == 0)
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cmd = &cmd_swap;
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} else if (argc == 4) {
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if (strcmp(COMMAND, "setmac") == 0)
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strMac = MAC_ADDRESS;
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strMac = MAC_ADDRESS; /* user-supplied mac address */
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else if ((!((part = PARTNUM[0] - '0') == 0 || part == 1))
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|| PARTNUM[1])
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|| PARTNUM[1]) /* only allow '1' or '0' */
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errno = EINVAL;
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else if (strcmp(COMMAND, "setchecksum") == 0)
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cmd = &cmd_setchecksum;
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@ -129,6 +134,7 @@ main(int argc, char *argv[])
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readGbeFile(&fd, FILENAME, flags, nr);
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/* perform operation specified by the user */
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if (strMac != NULL)
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cmd_setmac(strMac);
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else if (cmd != NULL)
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@ -145,6 +151,7 @@ nvmutil_exit:
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return errno;
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}
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/* load the gbe file into memory */
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void
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readGbeFile(int *fd, const char *path, int flags, size_t nr)
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{
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@ -174,6 +181,7 @@ readGbeFile(int *fd, const char *path, int flags, size_t nr)
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}
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}
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/* set mac address on valid nvm parts, per user input */
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void
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cmd_setmac(const char *strMac)
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{
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@ -193,12 +201,13 @@ cmd_setmac(const char *strMac)
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if (!validChecksum(partnum))
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continue;
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for (int w = 0; w < 3; w++)
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setWord(w, partnum, mac[w]);
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setWord(w, partnum, mac[w]); /* do not use memcpy! */
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part = partnum;
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cmd_setchecksum();
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}
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}
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/* read mac address from user input */
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int
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parseMacAddress(const char *strMac, uint16_t *mac)
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{
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@ -239,11 +248,12 @@ hextonum(char ch)
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else if ((ch >= 'a') && (ch <= 'f'))
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return ch - 'a' + 10;
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else if (ch == '?')
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return rhex();
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return rhex(); /* random number */
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else
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return 16;
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}
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/* generate a random number from 0 to 15, the unix way */
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uint8_t
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rhex(void)
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{
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@ -261,6 +271,7 @@ rhex(void)
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return rval;
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}
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/* show mac address and hexdump of each nvm part */
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void
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cmd_dump(void)
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{
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@ -276,6 +287,7 @@ cmd_dump(void)
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errno = 0;
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}
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/* show formatted mac address contained within the nvm part */
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void
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showmac(int partnum)
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{
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@ -290,6 +302,7 @@ showmac(int partnum)
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}
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}
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/* output a hexdump of both nvm parts, bytes reversed to big-endian order */
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void
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hexdump(int partnum)
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{
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@ -304,6 +317,7 @@ hexdump(int partnum)
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}
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}
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/* set a valid checksum on a given part */
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void
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cmd_setchecksum(void)
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{
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@ -313,6 +327,7 @@ cmd_setchecksum(void)
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setWord(0x3F, part, 0xBABA - val16);
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}
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/* set invalid checksum, intentionally */
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void
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cmd_brick(void)
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{
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@ -320,26 +335,28 @@ cmd_brick(void)
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setWord(0x3F, part, (word(0x3F, part)) ^ 0xFF);
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}
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/* swap the words of each part with each other */
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void
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cmd_swap(void)
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{
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if (validChecksum(1) || validChecksum(0)) {
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gbe[0] ^= gbe[1];
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gbe[0] ^= gbe[1]; /* speed hack: xorswap pointers, not words */
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gbe[1] ^= gbe[0];
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gbe[0] ^= gbe[1];
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gbeFileModified = 1;
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gbeFileModified = 1; /* not using setWord, so must set these */
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nvmPartModified[0] = 1;
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nvmPartModified[1] = 1;
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errno = 0;
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}
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}
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/* overwrite one part with the other */
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void
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cmd_copy(void)
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{
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if (validChecksum(part)) {
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gbe[part ^ 1] = gbe[part];
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gbeFileModified = 1;
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gbe[part ^ 1] = gbe[part]; /* pointer-based speed hack */
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gbeFileModified = 1; /* not using setWord, so must set these */
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nvmPartModified[part ^ 1] = 1;
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}
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}
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@ -358,12 +375,14 @@ validChecksum(int partnum)
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return 0;
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}
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/* fetch a word from gbe buffer */
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uint16_t
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word(int pos16, int partnum)
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{
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return buf16[pos16 + (partnum << 11)];
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}
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/* write a word to gbe buffer, and record that a write has occured */
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void
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setWord(int pos16, int partnum, uint16_t val16)
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{
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@ -375,6 +394,7 @@ setWord(int pos16, int partnum, uint16_t val16)
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nvmPartModified[partnum] = 1;
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}
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/* big-endian host compatibility: called post-read and again pre-write */
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void
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byteswap(int n, int partnum)
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{
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@ -382,24 +402,27 @@ byteswap(int n, int partnum)
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uint8_t *nbuf = (uint8_t *) gbe[partnum];
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for (int w = 0; w < wcount; w++) {
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b1 = b2 = w << 1;
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/* xor-based swap method */
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nbuf[b1] ^= nbuf[++b2];
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nbuf[b2] ^= nbuf[b1];
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nbuf[b1] ^= nbuf[b2];
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}
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}
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/* called after all operations are done, if gbe was modified */
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void
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writeGbeFile(int *fd, const char *filename)
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{
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int p, nw;
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errno = 0;
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if ((gbe[0] != gbe[1]) && (gbe[0] < gbe[1]))
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nw = 128; /* copy/swap command, so only write the nvm part */
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nw = 128; /* write only the nvm part */
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else
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nw = SIZE_4KB;
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nw = SIZE_4KB; /* copy/swap, so only write everything */
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for (p = 0; p < 2; p++) {
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if (gbe[0] > gbe[1])
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if (gbe[0] > gbe[1]) /* write sequentially on-disk */
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p ^= 1;
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if (!nvmPartModified[p])
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goto next_part;
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