[PATCH v3 04/11] bsd-user: various helper routines for sysctl

[Warner Losh <imp@bsdimp.com>]

cap_memory - Caps the memory to just below MAXINT
scale_to_guest_pages - Account for difference in host / guest page size
h2g_long_sat - converts a int64_t to a int32_t, saturating at max / min values
h2g_ulong_sat - converts a uint64_t to a uint32_t, saturating at max value

Signed-off-by: Warner Losh <imp@bsdimp.com>
---
 bsd-user/freebsd/os-sys.c | 86 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 86 insertions(+)

diff --git a/bsd-user/freebsd/os-sys.c b/bsd-user/freebsd/os-sys.c
index 1676ec10f83..9b84e90cb32 100644
--- a/bsd-user/freebsd/os-sys.c
+++ b/bsd-user/freebsd/os-sys.c
@@ -21,6 +21,92 @@
 #include "qemu.h"
 #include "target_arch_sysarch.h"
 
+#include <sys/sysctl.h>
+
+/*
+ * Length for the fixed length types.
+ * 0 means variable length for strings and structures
+ * Compare with sys/kern_sysctl.c ctl_size
+ * Note: Not all types appear to be used in-tree.
+ */
+static const int G_GNUC_UNUSED guest_ctl_size[CTLTYPE+1] = {
+        [CTLTYPE_INT] = sizeof(abi_int),
+        [CTLTYPE_UINT] = sizeof(abi_uint),
+        [CTLTYPE_LONG] = sizeof(abi_long),
+        [CTLTYPE_ULONG] = sizeof(abi_ulong),
+        [CTLTYPE_S8] = sizeof(int8_t),
+        [CTLTYPE_S16] = sizeof(int16_t),
+        [CTLTYPE_S32] = sizeof(int32_t),
+        [CTLTYPE_S64] = sizeof(int64_t),
+        [CTLTYPE_U8] = sizeof(uint8_t),
+        [CTLTYPE_U16] = sizeof(uint16_t),
+        [CTLTYPE_U32] = sizeof(uint32_t),
+        [CTLTYPE_U64] = sizeof(uint64_t),
+};
+
+static const int G_GNUC_UNUSED host_ctl_size[CTLTYPE+1] = {
+        [CTLTYPE_INT] = sizeof(int),
+        [CTLTYPE_UINT] = sizeof(u_int),
+        [CTLTYPE_LONG] = sizeof(long),
+        [CTLTYPE_ULONG] = sizeof(u_long),
+        [CTLTYPE_S8] = sizeof(int8_t),
+        [CTLTYPE_S16] = sizeof(int16_t),
+        [CTLTYPE_S32] = sizeof(int32_t),
+        [CTLTYPE_S64] = sizeof(int64_t),
+        [CTLTYPE_U8] = sizeof(uint8_t),
+        [CTLTYPE_U16] = sizeof(uint16_t),
+        [CTLTYPE_U32] = sizeof(uint32_t),
+        [CTLTYPE_U64] = sizeof(uint64_t),
+};
+
+#ifdef TARGET_ABI32
+/*
+ * Limit the amount of available memory to be most of the 32-bit address
+ * space. 0x100c000 was arrived at through trial and error as a good
+ * definition of 'most'.
+ */
+static const abi_ulong guest_max_mem = UINT32_MAX - 0x100c000 + 1;
+
+static abi_ulong G_GNUC_UNUSED cap_memory(uint64_t mem)
+{
+    return MIN(guest_max_mem, mem);
+}
+#endif
+
+static abi_ulong G_GNUC_UNUSED scale_to_guest_pages(uint64_t pages)
+{
+    /* Scale pages from host to guest */
+    pages = muldiv64(pages, qemu_real_host_page_size(), TARGET_PAGE_SIZE);
+#ifdef TARGET_ABI32
+    /* cap pages if need be */
+    pages = MIN(pages, guest_max_mem / (abi_ulong)TARGET_PAGE_SIZE);
+#endif
+    return pages;
+}
+
+#ifdef TARGET_ABI32
+/* Used only for TARGET_ABI32 */
+static abi_long G_GNUC_UNUSED h2g_long_sat(long l)
+{
+    if (l > INT32_MAX) {
+        l = INT32_MAX;
+    } else if (l < INT32_MIN) {
+        l = INT32_MIN;
+    }
+    return l;
+}
+
+static abi_ulong G_GNUC_UNUSED h2g_ulong_sat(u_long ul)
+{
+    return MIN(ul, UINT32_MAX);
+}
+#endif
+
+/*
+ * placeholder until bsd-user downstream upstreams this with its thread support
+ */
+#define bsd_get_ncpu() 1
+
 /* sysarch() is architecture dependent. */
 abi_long do_freebsd_sysarch(void *cpu_env, abi_long arg1, abi_long arg2)
 {
-- 
2.39.1