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util/nvmutil: add useful code comments

fsdg20230625
Leah Rowe 2023-04-06 19:30:20 +01:00
parent 7c403fcd9b
commit d3ad50dcb4
1 changed files with 39 additions and 16 deletions
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55
util/nvmutil/nvmutil.c
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@ -21,6 +21,11 @@
* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/ */
/*
* This file is part of the Libreboot project. Documentation available here:
* https://libreboot.org/docs/install/nvmutil.html
*/
#include <stdint.h> #include <stdint.h>
#include <string.h> #include <string.h>
#include <stdlib.h> #include <stdlib.h>
@ -78,33 +83,33 @@ main(int argc, char *argv[])
const char *strMac = NULL, *strRMac = "??:??:??:??:??:??"; const char *strMac = NULL, *strRMac = "??:??:??:??:??:??";
#ifdef HAVE_PLEDGE #ifdef HAVE_PLEDGE
if (pledge("stdio wpath", NULL) == -1) if (pledge("stdio wpath", NULL) == -1) /* only used on openbsd */
err(errno, "pledge"); err(errno, "pledge"); /* https://man.openbsd.org/pledge.2 */
#endif #endif
buf = (uint8_t *) &buf16; buf = (uint8_t *) &buf16;
gbe[1] = (gbe[0] = (size_t) buf) + SIZE_4KB; gbe[1] = (gbe[0] = (size_t) buf) + SIZE_4KB;
test = 1; test = 1;
big_endian = ((uint8_t *) &test)[0] ^ 1; big_endian = ((uint8_t *) &test)[0] ^ 1; /* check host endianness */
if (argc == 3) { if (argc == 3) {
if (strcmp(COMMAND, "dump") == 0) { if (strcmp(COMMAND, "dump") == 0) {
#ifdef HAVE_PLEDGE #ifdef HAVE_PLEDGE
if (pledge("stdio rpath", NULL) == -1) if (pledge("stdio rpath", NULL) == -1)
err(errno, "pledge"); err(errno, "pledge"); /* not very puffy */
#endif #endif
flags = O_RDONLY; flags = O_RDONLY;
cmd = &cmd_dump; cmd = &cmd_dump;
} else if (strcmp(COMMAND, "setmac") == 0) } else if (strcmp(COMMAND, "setmac") == 0)
strMac = (char *) strRMac; strMac = (char *) strRMac; /* random mac address */
else if (strcmp(COMMAND, "swap") == 0) else if (strcmp(COMMAND, "swap") == 0)
cmd = &cmd_swap; cmd = &cmd_swap;
} else if (argc == 4) { } else if (argc == 4) {
if (strcmp(COMMAND, "setmac") == 0) if (strcmp(COMMAND, "setmac") == 0)
strMac = MAC_ADDRESS; strMac = MAC_ADDRESS; /* user-supplied mac address */
else if ((!((part = PARTNUM[0] - '0') == 0 || part == 1)) else if ((!((part = PARTNUM[0] - '0') == 0 || part == 1))
|| PARTNUM[1]) || PARTNUM[1]) /* only allow '1' or '0' */
errno = EINVAL; errno = EINVAL;
else if (strcmp(COMMAND, "setchecksum") == 0) else if (strcmp(COMMAND, "setchecksum") == 0)
cmd = &cmd_setchecksum; cmd = &cmd_setchecksum;
@ -129,6 +134,7 @@ main(int argc, char *argv[])
readGbeFile(&fd, FILENAME, flags, nr); readGbeFile(&fd, FILENAME, flags, nr);
/* perform operation specified by the user */
if (strMac != NULL) if (strMac != NULL)
cmd_setmac(strMac); cmd_setmac(strMac);
else if (cmd != NULL) else if (cmd != NULL)
@ -145,6 +151,7 @@ nvmutil_exit:
return errno; return errno;
} }
/* load the gbe file into memory */
void void
readGbeFile(int *fd, const char *path, int flags, size_t nr) readGbeFile(int *fd, const char *path, int flags, size_t nr)
{ {
@ -174,6 +181,7 @@ readGbeFile(int *fd, const char *path, int flags, size_t nr)
} }
} }
/* set mac address on valid nvm parts, per user input */
void void
cmd_setmac(const char *strMac) cmd_setmac(const char *strMac)
{ {
@ -193,12 +201,13 @@ cmd_setmac(const char *strMac)
if (!validChecksum(partnum)) if (!validChecksum(partnum))
continue; continue;
for (int w = 0; w < 3; w++) for (int w = 0; w < 3; w++)
setWord(w, partnum, mac[w]); setWord(w, partnum, mac[w]); /* do not use memcpy! */
part = partnum; part = partnum;
cmd_setchecksum(); cmd_setchecksum();
} }
} }
/* read mac address from user input */
int int
parseMacAddress(const char *strMac, uint16_t *mac) parseMacAddress(const char *strMac, uint16_t *mac)
{ {
@ -239,11 +248,12 @@ hextonum(char ch)
else if ((ch >= 'a') && (ch <= 'f')) else if ((ch >= 'a') && (ch <= 'f'))
return ch - 'a' + 10; return ch - 'a' + 10;
else if (ch == '?') else if (ch == '?')
return rhex(); return rhex(); /* random number */
else else
return 16; return 16;
} }
/* generate a random number from 0 to 15, the unix way */
uint8_t uint8_t
rhex(void) rhex(void)
{ {
@ -261,6 +271,7 @@ rhex(void)
return rval; return rval;
} }
/* show mac address and hexdump of each nvm part */
void void
cmd_dump(void) cmd_dump(void)
{ {
@ -276,6 +287,7 @@ cmd_dump(void)
errno = 0; errno = 0;
} }
/* show formatted mac address contained within the nvm part */
void void
showmac(int partnum) showmac(int partnum)
{ {
@ -290,6 +302,7 @@ showmac(int partnum)
} }
} }
/* output a hexdump of both nvm parts, bytes reversed to big-endian order */
void void
hexdump(int partnum) hexdump(int partnum)
{ {
@ -304,6 +317,7 @@ hexdump(int partnum)
} }
} }
/* set a valid checksum on a given part */
void void
cmd_setchecksum(void) cmd_setchecksum(void)
{ {
@ -313,6 +327,7 @@ cmd_setchecksum(void)
setWord(0x3F, part, 0xBABA - val16); setWord(0x3F, part, 0xBABA - val16);
} }
/* set invalid checksum, intentionally */
void void
cmd_brick(void) cmd_brick(void)
{ {
@ -320,26 +335,28 @@ cmd_brick(void)
setWord(0x3F, part, (word(0x3F, part)) ^ 0xFF); setWord(0x3F, part, (word(0x3F, part)) ^ 0xFF);
} }
/* swap the words of each part with each other */
void void
cmd_swap(void) cmd_swap(void)
{ {
if (validChecksum(1) || validChecksum(0)) { if (validChecksum(1) || validChecksum(0)) {
gbe[0] ^= gbe[1]; gbe[0] ^= gbe[1]; /* speed hack: xorswap pointers, not words */
gbe[1] ^= gbe[0]; gbe[1] ^= gbe[0];
gbe[0] ^= gbe[1]; gbe[0] ^= gbe[1];
gbeFileModified = 1; gbeFileModified = 1; /* not using setWord, so must set these */
nvmPartModified[0] = 1; nvmPartModified[0] = 1;
nvmPartModified[1] = 1; nvmPartModified[1] = 1;
errno = 0; errno = 0;
} }
} }
/* overwrite one part with the other */
void void
cmd_copy(void) cmd_copy(void)
{ {
if (validChecksum(part)) { if (validChecksum(part)) {
gbe[part ^ 1] = gbe[part]; gbe[part ^ 1] = gbe[part]; /* pointer-based speed hack */
gbeFileModified = 1; gbeFileModified = 1; /* not using setWord, so must set these */
nvmPartModified[part ^ 1] = 1; nvmPartModified[part ^ 1] = 1;
} }
} }
@ -358,12 +375,14 @@ validChecksum(int partnum)
return 0; return 0;
} }
/* fetch a word from gbe buffer */
uint16_t uint16_t
word(int pos16, int partnum) word(int pos16, int partnum)
{ {
return buf16[pos16 + (partnum << 11)]; return buf16[pos16 + (partnum << 11)];
} }
/* write a word to gbe buffer, and record that a write has occured */
void void
setWord(int pos16, int partnum, uint16_t val16) setWord(int pos16, int partnum, uint16_t val16)
{ {
@ -375,6 +394,7 @@ setWord(int pos16, int partnum, uint16_t val16)
nvmPartModified[partnum] = 1; nvmPartModified[partnum] = 1;
} }
/* big-endian host compatibility: called post-read and again pre-write */
void void
byteswap(int n, int partnum) byteswap(int n, int partnum)
{ {
@ -382,24 +402,27 @@ byteswap(int n, int partnum)
uint8_t *nbuf = (uint8_t *) gbe[partnum]; uint8_t *nbuf = (uint8_t *) gbe[partnum];
for (int w = 0; w < wcount; w++) { for (int w = 0; w < wcount; w++) {
b1 = b2 = w << 1; b1 = b2 = w << 1;
/* xor-based swap method */
nbuf[b1] ^= nbuf[++b2]; nbuf[b1] ^= nbuf[++b2];
nbuf[b2] ^= nbuf[b1]; nbuf[b2] ^= nbuf[b1];
nbuf[b1] ^= nbuf[b2]; nbuf[b1] ^= nbuf[b2];
} }
} }
/* called after all operations are done, if gbe was modified */
void void
writeGbeFile(int *fd, const char *filename) writeGbeFile(int *fd, const char *filename)
{ {
int p, nw; int p, nw;
errno = 0; errno = 0;
if ((gbe[0] != gbe[1]) && (gbe[0] < gbe[1])) if ((gbe[0] != gbe[1]) && (gbe[0] < gbe[1]))
nw = 128; /* copy/swap command, so only write the nvm part */ nw = 128; /* write only the nvm part */
else else
nw = SIZE_4KB; nw = SIZE_4KB; /* copy/swap, so only write everything */
for (p = 0; p < 2; p++) { for (p = 0; p < 2; p++) {
if (gbe[0] > gbe[1]) if (gbe[0] > gbe[1]) /* write sequentially on-disk */
p ^= 1; p ^= 1;
if (!nvmPartModified[p]) if (!nvmPartModified[p])
goto next_part; goto next_part;