[PATCH v3 8/9] bsd-user/mmap.c: Implement MAP_EXCL, required by jemalloc in head

[Warner Losh]

From: Kyle Evans <kevans@FreeBSD.org>

jemalloc requires a working MAP_EXCL. Ensure that no page is double
mapped when specified. In addition, use guest_range_valid_untagged to
test for valid ranges of pages rather than an incomplete inlined version
of the test that might be wrong.

Signed-off-by: Kyle Evans <kevans@FreeBSD.org>
Signed-off-by: Warner Losh <imp@bsdimp.com>
---
 bsd-user/mmap.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/bsd-user/mmap.c b/bsd-user/mmap.c
index 4ecd949a10..066d9c10ff 100644
--- a/bsd-user/mmap.c
+++ b/bsd-user/mmap.c
@@ -403,7 +403,7 @@ abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size)
 abi_long target_mmap(abi_ulong start, abi_ulong len, int prot,
                      int flags, int fd, off_t offset)
 {
-    abi_ulong ret, end, real_start, real_end, retaddr, host_offset, host_len;
+    abi_ulong addr, ret, end, real_start, real_end, retaddr, host_offset, 
host_len;
 
     mmap_lock();
     if (qemu_loglevel_mask(CPU_LOG_PAGE)) {
@@ -574,12 +574,10 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int 
prot,
          * It can fail only on 64-bit host with 32-bit target.
          * On any other target/host host mmap() handles this error correctly.
          */
-#if TARGET_ABI_BITS == 32 && HOST_LONG_BITS == 64
-        if ((unsigned long)start + len - 1 > (abi_ulong) -1) {
+        if (!guest_range_valid_untagged(start, len)) {
             errno = EINVAL;
             goto fail;
         }
-#endif
 
         /*
          * worst case: we cannot map the file because the offset is not
@@ -614,6 +612,12 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int 
prot,
             goto the_end;
         }
 
+        /* Reject the mapping if any page within the range is mapped */
+        if ((flags & MAP_EXCL) && page_check_range(start, len, 0) < 0) {
+            errno = EINVAL;
+            goto fail;
+        }
+
         /* handle the start of the mapping */
         if (start > real_start) {
             if (real_end == real_start + qemu_host_page_size) {
-- 
2.32.0