linux-user: Use 'last' instead of 'end' in target_mmap

Complete the transition within the mmap functions to a formulation
that does not overflow at the end of the address space.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20230707204054.8792-20-richard.henderson@linaro.org>

1 files changed, 23 insertions, 22 deletions

diff --git a/linux-user/mmap.c b/linux-user/mmap.c
index 738b9b7..bb9cbe5 100644
--- a/linux-user/mmap.c
+++ b/linux-user/mmap.c
@@ -456,8 +456,8 @@ abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size, abi_ulong align)
 abi_long target_mmap(abi_ulong start, abi_ulong len, int target_prot,
                      int flags, int fd, off_t offset)
 {
-    abi_ulong ret, end, real_start, real_end, retaddr, host_len,
-              passthrough_start = -1, passthrough_end = -1;
+    abi_ulong ret, last, real_start, real_last, retaddr, host_len;
+    abi_ulong passthrough_start = -1, passthrough_last = 0;
     int page_flags;
     off_t host_offset;
 
@@ -581,29 +581,30 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int target_prot,
             host_start += offset - host_offset;
         }
         start = h2g(host_start);
+        last = start + len - 1;
         passthrough_start = start;
-        passthrough_end = start + len;
+        passthrough_last = last;
     } else {
         if (start & ~TARGET_PAGE_MASK) {
             errno = EINVAL;
             goto fail;
         }
-        end = start + len;
-        real_end = HOST_PAGE_ALIGN(end);
+        last = start + len - 1;
+        real_last = HOST_PAGE_ALIGN(last) - 1;
 
         /*
          * Test if requested memory area fits target address space
          * It can fail only on 64-bit host with 32-bit target.
          * On any other target/host host mmap() handles this error correctly.
          */
-        if (end < start || !guest_range_valid_untagged(start, len)) {
+        if (last < start || !guest_range_valid_untagged(start, len)) {
             errno = ENOMEM;
             goto fail;
         }
 
         /* Validate that the chosen range is empty. */
         if ((flags & MAP_FIXED_NOREPLACE)
-            && !page_check_range_empty(start, end - 1)) {
+            && !page_check_range_empty(start, last)) {
             errno = EEXIST;
             goto fail;
         }
@@ -642,9 +643,9 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int target_prot,
 
         /* handle the start of the mapping */
         if (start > real_start) {
-            if (real_end == real_start + qemu_host_page_size) {
+            if (real_last == real_start + qemu_host_page_size - 1) {
                 /* one single host page */
-                if (!mmap_frag(real_start, start, end - 1,
+                if (!mmap_frag(real_start, start, last,
                                target_prot, flags, fd, offset)) {
                     goto fail;
                 }
@@ -658,18 +659,18 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int target_prot,
             real_start += qemu_host_page_size;
         }
         /* handle the end of the mapping */
-        if (end < real_end) {
-            if (!mmap_frag(real_end - qemu_host_page_size,
-                           real_end - qemu_host_page_size, end - 1,
+        if (last < real_last) {
+            abi_ulong real_page = real_last - qemu_host_page_size + 1;
+            if (!mmap_frag(real_page, real_page, last,
                            target_prot, flags, fd,
-                           offset + real_end - qemu_host_page_size - start)) {
+                           offset + real_page - start)) {
                 goto fail;
             }
-            real_end -= qemu_host_page_size;
+            real_last -= qemu_host_page_size;
         }
 
         /* map the middle (easier) */
-        if (real_start < real_end) {
+        if (real_start < real_last) {
             void *p;
             off_t offset1;
 
@@ -678,13 +679,13 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int target_prot,
             } else {
                 offset1 = offset + real_start - start;
             }
-            p = mmap(g2h_untagged(real_start), real_end - real_start,
+            p = mmap(g2h_untagged(real_start), real_last - real_start + 1,
                      target_to_host_prot(target_prot), flags, fd, offset1);
             if (p == MAP_FAILED) {
                 goto fail;
             }
             passthrough_start = real_start;
-            passthrough_end = real_end;
+            passthrough_last = real_last;
         }
     }
  the_end1:
@@ -692,16 +693,16 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int target_prot,
         page_flags |= PAGE_ANON;
     }
     page_flags |= PAGE_RESET;
-    if (passthrough_start == passthrough_end) {
-        page_set_flags(start, start + len - 1, page_flags);
+    if (passthrough_start > passthrough_last) {
+        page_set_flags(start, last, page_flags);
     } else {
         if (start < passthrough_start) {
             page_set_flags(start, passthrough_start - 1, page_flags);
         }
-        page_set_flags(passthrough_start, passthrough_end - 1,
+        page_set_flags(passthrough_start, passthrough_last,
                        page_flags | PAGE_PASSTHROUGH);
-        if (passthrough_end < start + len) {
-            page_set_flags(passthrough_end, start + len - 1, page_flags);
+        if (passthrough_last < last) {
+            page_set_flags(passthrough_last + 1, last, page_flags);
         }
     }
  the_end: