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util/nvmutil: re-try reads if errno is EINTR

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this is a bit of fault tolerance. a bit bloated too,
but it should make the code more resilient.

we limited the number of retries to 200 retries.

EINTR is when the syscall (read/pread) is interrupted.

we still error out on other conditions; we also still
error out on EINTR if the number of re-tries surpasses
200.

during this re-try loop, if *another* error occurs, we
exit as normal. this is done for both files: the gbe
file, and /dev/urandom.

Signed-off-by: Leah Rowe <leah@libreboot.org>
This commit is contained in:
Leah Rowe
2026-03-03 21:43:32 +00:00
parent 493e3cf069
commit 21b8de87ff
1 changed files with 44 additions and 7 deletions
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util/nvmutil/nvmutil.c
+44 -7
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@@ -27,6 +27,8 @@ static void check_mac_separator(int);
static void set_mac_nib(int, int, uint8_t *);
static uint8_t hextonum(char);
static uint8_t rhex(void);
static void read_urandom(uint8_t *, ssize_t);
static int valid_read(const char *, ssize_t, ssize_t, int);
static int write_mac_part(int);
static void cmd_dump(void);
static void print_mac_address(int);
@@ -57,6 +59,8 @@ static void set_err(int);
#define SIZE_16KB 0x4000
#define SIZE_128KB 0x20000
#define MAX_RETRY_READ 200
#define items(x) (sizeof((x)) / sizeof((x)[0]))
static uint8_t buf[SIZE_8KB];
@@ -241,10 +245,17 @@ read_gbe(void)
static void
read_gbe_part(int p, int invert)
{
if (pread(fd, buf + (SIZE_4KB * (p ^ invert)), SIZE_4KB, p * partsize)
!= (ssize_t) SIZE_4KB)
err(ECANCELED,
"Can't read %d b from '%s' p%d", SIZE_4KB, fname, p);
int retry;
ssize_t rval;
for (retry = 0; retry < (int) MAX_RETRY_READ; retry++) {
rval = pread(fd, buf + (SIZE_4KB * (p ^ invert)),
SIZE_4KB, p * partsize);
if (valid_read(fname, rval, (ssize_t) SIZE_4KB, retry))
break;
}
swap(p ^ invert); /* handle big-endian host CPU */
}
@@ -349,14 +360,40 @@ rhex(void)
if (!n) {
n = sizeof(rnum) - 1;
if (read(rfd, (uint8_t *) &rnum, sizeof(rnum))
!= (ssize_t) (sizeof(rnum)))
err(ECANCELED, "Could not read from /dev/urandom");
read_urandom((uint8_t *) rnum, sizeof(rnum));
}
return rnum[n--] & 0xf;
}
static void
read_urandom(uint8_t *rnum, ssize_t rsize)
{
int retry = 0;
ssize_t rval;
for (retry = 0; retry < (int) MAX_RETRY_READ; retry++) {
rval = read(rfd, (uint8_t *) rnum, rsize);
if (valid_read("/dev/urandom", rval, rsize, retry))
break;
}
}
static int
valid_read(const char *rpath, ssize_t rval, ssize_t rsize, int retry)
{
if (rval == (ssize_t) rsize)
return 1;
if (rval != -1)
err(ECANCELED, "Short read, %lld: %s", rval, rpath);
if (errno != EINTR)
err(ECANCELED, "read '%s'", rpath);
if (retry == MAX_RETRY_READ - 1)
err(EINTR, "read: max retries exceeded: %s", rpath);
return (errno = 0);
}
static int
write_mac_part(int partnum)
{