user: Introduce 'user/guest-host.h' header

Extract all declarations related to 'guest from/to host'
address translation to a new "user/guest-host.h" header.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20241212185341.2857-2-philmd@linaro.org>

include/user/guest-host.h

@@ -0,0 +1,87 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * guest <-> host helpers.
+ *
+ *  Copyright (c) 2003 Fabrice Bellard
+ */
+
+#ifndef USER_GUEST_HOST_H
+#define USER_GUEST_HOST_H
+
+#include "user/abitypes.h"
+#include "user/guest-base.h"
+#include "cpu.h"
+
+/*
+ * If non-zero, the guest virtual address space is a contiguous subset
+ * of the host virtual address space, i.e. '-R reserved_va' is in effect
+ * either from the command-line or by default.  The value is the last
+ * byte of the guest address space e.g. UINT32_MAX.
+ *
+ * If zero, the host and guest virtual address spaces are intermingled.
+ */
+extern unsigned long reserved_va;
+
+/*
+ * Limit the guest addresses as best we can.
+ *
+ * When not using -R reserved_va, we cannot really limit the guest
+ * to less address space than the host.  For 32-bit guests, this
+ * acts as a sanity check that we're not giving the guest an address
+ * that it cannot even represent.  For 64-bit guests... the address
+ * might not be what the real kernel would give, but it is at least
+ * representable in the guest.
+ *
+ * TODO: Improve address allocation to avoid this problem, and to
+ * avoid setting bits at the top of guest addresses that might need
+ * to be used for tags.
+ */
+#define GUEST_ADDR_MAX_                                                 \
+    ((MIN_CONST(TARGET_VIRT_ADDR_SPACE_BITS, TARGET_ABI_BITS) <= 32) ?  \
+     UINT32_MAX : ~0ul)
+#define GUEST_ADDR_MAX    (reserved_va ? : GUEST_ADDR_MAX_)
+
+#ifndef TARGET_TAGGED_ADDRESSES
+static inline abi_ptr cpu_untagged_addr(CPUState *cs, abi_ptr x)
+{
+    return x;
+}
+#endif
+
+/* All direct uses of g2h and h2g need to go away for usermode softmmu.  */
+static inline void *g2h_untagged(abi_ptr x)
+{
+    return (void *)((uintptr_t)(x) + guest_base);
+}
+
+static inline void *g2h(CPUState *cs, abi_ptr x)
+{
+    return g2h_untagged(cpu_untagged_addr(cs, x));
+}
+
+static inline bool guest_addr_valid_untagged(abi_ulong x)
+{
+    return x <= GUEST_ADDR_MAX;
+}
+
+static inline bool guest_range_valid_untagged(abi_ulong start, abi_ulong len)
+{
+    return len - 1 <= GUEST_ADDR_MAX && start <= GUEST_ADDR_MAX - len + 1;
+}
+
+#define h2g_valid(x) \
+    (HOST_LONG_BITS <= TARGET_VIRT_ADDR_SPACE_BITS || \
+     (uintptr_t)(x) - guest_base <= GUEST_ADDR_MAX)
+
+#define h2g_nocheck(x) ({ \
+    uintptr_t __ret = (uintptr_t)(x) - guest_base; \
+    (abi_ptr)__ret; \
+})
+
+#define h2g(x) ({ \
+    /* Check if given address fits target address space */ \
+    assert(h2g_valid(x)); \
+    h2g_nocheck(x); \
+})
+
+#endif