// Gets slot_suffix from either the kernel cmdline / firmware or the
// misc partition. Sets |out_suffix| on success and returns 0. Returns
// -1 if slot_suffix could not be determined.
static int get_active_slot_suffix(struct fstab *fstab, char *out_suffix,
size_t suffix_len)
{
char propbuf[PROPERTY_VALUE_MAX];
// Get the suffix from the kernel commandline (note that we don't
// allow the empty suffix). On bootloaders natively supporting A/B
// we'll hit this path every time so don't bother logging it.
property_get("ro.boot.slot_suffix", propbuf, "");
if (propbuf[0] != '\0') {
strncpy(out_suffix, propbuf, suffix_len);
return 0;
}
// If we couldn't get the suffix from the kernel cmdline, try the
// the misc partition.
if (get_active_slot_suffix_from_misc(fstab, out_suffix, suffix_len) == 0) {
INFO("Using slot suffix \"%s\" from misc\n", out_suffix);
return 0;
}
ERROR("Error determining slot_suffix\n");
return -1;
}
// Gets slot_suffix from either the kernel cmdline / firmware, the
// misc partition or built-in fallback.
static void get_active_slot_suffix(struct fstab *fstab, char *out_suffix,
size_t suffix_len)
{
char propbuf[PROPERTY_VALUE_MAX];
// Get the suffix from the kernel commandline (note that we don't
// allow the empty suffix). On bootloaders natively supporting A/B
// we'll hit this path every time so don't bother logging it.
property_get("ro.boot.slot_suffix", propbuf, "");
if (propbuf[0] != '\0') {
strncpy(out_suffix, propbuf, suffix_len);
return;
}
// If we couldn't get the suffix from the kernel cmdline, try the
// the misc partition.
if (get_active_slot_suffix_from_misc(fstab, out_suffix, suffix_len) == 0) {
INFO("Using slot suffix \"%s\" from misc\n", out_suffix);
return;
}
// If that didn't work, fall back to _a. The reasoning here is
// that since the fstab has the slotselect option set (otherwise
// we wouldn't end up here) we must assume that partitions are
// indeed set up for A/B. This corner-case is important because we
// may be on this codepath on newly provisioned A/B devices where
// misc isn't set up properly (it's just zeroes) and the
// bootloader does not (yet) natively support A/B.
//
// Why '_a'? Because that's what system/extras/boot_control_copy
// is using and since the bootloader isn't A/B aware we assume
// slots are set up this way.
WARNING("Could not determine slot suffix, falling back to \"_a\"\n");
strncpy(out_suffix, "_a", suffix_len);
return;
}
