linux-user: Split out mmap_h_eq_g

Move the MAX_FIXED_NOREPLACE check for reserved_va earlier.
Move the computation of host_prot earlier.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Acked-by: Helge Deller <deller@gmx.de>
Message-Id: <20240102015808.132373-22-richard.henderson@linaro.org>

linux-user/mmap.c

@@ -542,6 +542,33 @@ static abi_long mmap_end(abi_ulong start, abi_ulong last,
     return start;
 }
 
+/*
+ * Special case host page size == target page size,
+ * where there are no edge conditions.
+ */
+static abi_long mmap_h_eq_g(abi_ulong start, abi_ulong len,
+                            int host_prot, int flags, int page_flags,
+                            int fd, off_t offset)
+{
+    void *p, *want_p = g2h_untagged(start);
+    abi_ulong last;
+
+    p = mmap(want_p, len, host_prot, flags, fd, offset);
+    if (p == MAP_FAILED) {
+        return -1;
+    }
+    /* If the host kernel does not support MAP_FIXED_NOREPLACE, emulate. */
+    if ((flags & MAP_FIXED_NOREPLACE) && p != want_p) {
+        do_munmap(p, len);
+        errno = EEXIST;
+        return -1;
+    }
+
+    start = h2g(p);
+    last = start + len - 1;
+    return mmap_end(start, last, start, last, flags, page_flags);
+}
+
 static abi_long target_mmap__locked(abi_ulong start, abi_ulong len,
                                     int target_prot, int flags, int page_flags,
                                     int fd, off_t offset)
@@ -550,6 +577,7 @@ static abi_long target_mmap__locked(abi_ulong start, abi_ulong len,
     abi_ulong ret, last, real_start, real_last, retaddr, host_len;
     abi_ulong passthrough_start = -1, passthrough_last = 0;
     off_t host_offset;
+    int host_prot;
 
     real_start = start & -host_page_size;
     host_offset = offset & -host_page_size;
@@ -558,16 +586,33 @@ static abi_long target_mmap__locked(abi_ulong start, abi_ulong len,
      * For reserved_va, we are in full control of the allocation.
      * Find a suitable hole and convert to MAP_FIXED.
      */
-    if (reserved_va && !(flags & (MAP_FIXED | MAP_FIXED_NOREPLACE))) {
-        host_len = len + offset - host_offset;
-        start = mmap_find_vma(real_start, host_len,
-                              MAX(host_page_size, TARGET_PAGE_SIZE));
-        if (start == (abi_ulong)-1) {
-            errno = ENOMEM;
-            return -1;
+    if (reserved_va) {
+        if (flags & MAP_FIXED_NOREPLACE) {
+            /* Validate that the chosen range is empty. */
+            if (!page_check_range_empty(start, start + len - 1)) {
+                errno = EEXIST;
+                return -1;
+            }
+            flags = (flags & ~MAP_FIXED_NOREPLACE) | MAP_FIXED;
+        } else if (!(flags & MAP_FIXED)) {
+            size_t real_len = len + offset - host_offset;
+            abi_ulong align = MAX(host_page_size, TARGET_PAGE_SIZE);
+
+            start = mmap_find_vma(real_start, real_len, align);
+            if (start == (abi_ulong)-1) {
+                errno = ENOMEM;
+                return -1;
+            }
+            start += offset - host_offset;
+            flags |= MAP_FIXED;
         }
-        start += offset - host_offset;
-        flags |= MAP_FIXED;
+    }
+
+    host_prot = target_to_host_prot(target_prot);
+
+    if (host_page_size == TARGET_PAGE_SIZE) {
+        return mmap_h_eq_g(start, len, host_prot, flags,
+                           page_flags, fd, offset);
     }
 
     /*
@@ -603,12 +648,10 @@ static abi_long target_mmap__locked(abi_ulong start, abi_ulong len,
 
     if (!(flags & (MAP_FIXED | MAP_FIXED_NOREPLACE))) {
         uintptr_t host_start;
-        int host_prot;
         void *p;
 
         host_len = len + offset - host_offset;
         host_len = ROUND_UP(host_len, host_page_size);
-        host_prot = target_to_host_prot(target_prot);
 
         /* Note: we prefer to control the mapping address. */
         p = mmap(g2h_untagged(start), host_len, host_prot,
@@ -731,8 +774,7 @@ static abi_long target_mmap__locked(abi_ulong start, abi_ulong len,
             len1 = real_last - real_start + 1;
             want_p = g2h_untagged(real_start);
 
-            p = mmap(want_p, len1, target_to_host_prot(target_prot),
-                     flags, fd, offset1);
+            p = mmap(want_p, len1, host_prot, flags, fd, offset1);
             if (p != want_p) {
                 if (p != MAP_FAILED) {
                     do_munmap(p, len1);