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util/nvmutil: don't copy data in copy/swap

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instead, use a single integer, set to 1 if using
these commands (otherwise set to 0) used as an XOR
mask.

use this to invert where data gets read. one quirk
with this is that if a copy operation is performed
from a part with a bad checksum, it's already done
in advance, in memory, but then the check on the
checksum in cmd_copy is now checking the other part,
which will be all zeroes, so i invert that too; this
means now when running cmd_copy, it'll complain about
an invalid part, but the part number is inverted.

it's a small price to pay, because this restores the
previous performance optimisations but without being
as unsafe.

this is also true when doing the swap.

Signed-off-by: Leah Rowe <leah@libreboot.org>
This commit is contained in:
Leah Rowe
2026-03-03 13:03:41 +00:00
parent 98bc523274
commit 9044b55c48
1 changed files with 17 additions and 12 deletions
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util/nvmutil/nvmutil.c
+17 -12
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@@ -18,7 +18,7 @@ void cmd_setchecksum(void), cmd_brick(void), swap(int partnum), writeGbe(void),
cmd_dump(void), cmd_setmac(void), readGbe(void), print_mac_address(int),
hexdump(int), set_mac_nib(int, int, uint8_t *), checkdir(const char *),
parseMacString(const char *strMac, uint16_t *mac), cmd_swap(void),
openFiles(void), cmd_copy(void), writeGbe_part(int), readGbe_part(int),
openFiles(void), cmd_copy(void), writeGbe_part(int), readGbe_part(int, int),
set_cmd(int, char **), setWord(int, int, uint16_t), check_bounds(int, int),
xopen(int *, const char *, int p, struct stat *), checkMacSeparator(int),
set_mac_byte(int, uint64_t *), usage(char*), set_io_flags(int, char **),
@@ -185,19 +185,29 @@ xopen(int *f, const char *l, int p, struct stat *st)
void
readGbe(void)
{
int invert = 0;
int do_read[2] = {1, 1};
if ((cmd == cmd_copy) || (cmd == cmd_brick) || (cmd == cmd_setchecksum))
do_read[part ^ 1] = 0;
/*
* speedhack: if copy/swap, flip where data gets written to memory,
* so that cmd_copy and cmd_swap don't have to work on every word
*/
if ((cmd == cmd_copy) || (cmd == cmd_swap))
invert = 1;
for (int p = 0; p < 2; p++)
if (do_read[p])
readGbe_part(p);
readGbe_part(p, invert);
}
void
readGbe_part(int p)
readGbe_part(int p, int invert)
{
if (pread(fd, buf + (SIZE_4KB * p), SIZE_4KB, p * partsize) != SIZE_4KB)
if (pread(fd, buf + (SIZE_4KB * (p ^ invert)), SIZE_4KB, p * partsize)
!= SIZE_4KB)
err(set_err(ECANCELED),
"Can't read %d b from '%s' p%d", SIZE_4KB, fname, p);
swap(p); /* handle big-endian host CPU */
@@ -378,9 +388,8 @@ cmd_brick(void)
void
cmd_copy(void)
{
err_if(!goodChecksum(part));
for (int c = 0; c < (SIZE_4KB >> 1); c++)
setWord(c, part ^ 1, word(c, part));
err_if(!goodChecksum(part ^ 1));
nvmPartModified[part ^ 1] = 1;
}
void
@@ -388,11 +397,7 @@ cmd_swap(void) {
err_if(!(goodChecksum(0) || goodChecksum(1)));
errno = 0;
for (int c = 0; c < (SIZE_4KB >> 1); c++) {
uint16_t chg = word(c, 0);
setWord(c, 0, word(c, 1));
setWord(c, 1, chg);
}
nvmPartModified[1] = nvmPartModified[0] = 1;
}
int