On 2/13/23 14:27, Warner Losh wrote:
+/*
+ * Convert the old value from host to target.
host vs guest is clearer language; "target" gets overloaded, even though still present in
the code base.
+ *
+ * For LONG and ULONG on ABI32, we need to 'down convert' the 8 byte quantities
+ * to 4 bytes. The caller setup a buffer in host memory to get this data from
+ * the kernel and pass it to us. We do the down conversion and adjust the
length
+ * so the caller knows what to write as the returned length into the target
when
+ * it copies the down converted values into the target.
+ *
+ * For normal integral types, we just need to byte swap. No size changes.
+ *
+ * For strings and node data, there's no conversion needed.
+ *
+ * For opaque data, per sysctl OID converts take care of it.
+ */
+static void G_GNUC_UNUSED h2t_old_sysctl(void *holdp, size_t *holdlen,
uint32_t kind)
h2g.
+ /*
+ * hlen == 0 for CTLTYPE_STRING and CTLTYPE_NODE, which need no conversion
+ * as well as CTLTYPE_OPAQUE, which needs special converters.
+ */
+ if (hlen == 0) {
+ return;
+ }
+
+ while (len < *holdlen) {
+ if (hlen == tlen) {
+ switch (hlen) {
+ case 1:
+ /* Nothing needed: no byteswapping and assigning in place */
+ break;
+ case 2:
+ *(uint16_t *)tp = tswap16(*(uint16_t *)hp);
+ break;
+ case 4:
+ *(uint32_t *)tp = tswap32(*(uint32_t *)hp);
+ break;
+ case 8:
+ *(uint64_t *)tp = tswap64(*(uint64_t *)hp);
+ break;
+ }
default: g_assert_not_reached().
+ }
+#ifdef TARGET_ABI32
+ else {
+ /*
+ * Saturating assignment for the only two types that differ between
+ * 32-bit and 64-bit machines. All other integral types have the
+ * same, fixed size and will be converted w/o loss of precision
+ * in the above switch.
+ */
+ switch (kind & CTLTYPE) {
+ case CTLTYPE_LONG:
+ *(abi_long *)tp = tswap32(h2t_long_sat(*(long *)hp));
+ break;
+ case CTLTYPE_ULONG:
+ *(abi_ulong *)tp = tswap32(h2t_ulong_sat(*(u_long *)hp));
+ break;
+ }
default: g_assert_not_reached().
+ }
+#endif
#else
g_assert_not_reached();
r~
