[Qemu-devel] [PATCH 2/5] linux-user: fix page_unprotect when host page size > target page size

[Aurelien Jarno]

When the host page size is bigger that the target one, unprotecting a
page should:
- mark all the target pages corresponding to the host page as writable
- invalidate all tb corresponding to the host page (and not the target
  page)

Signed-off-by: Aurelien Jarno <address@hidden>
---
 exec.c |   45 ++++++++++++++++++++++-----------------------
 1 files changed, 22 insertions(+), 23 deletions(-)

diff --git a/exec.c b/exec.c
index 0916208..1b0fe52 100644
--- a/exec.c
+++ b/exec.c
@@ -2447,8 +2447,8 @@ int page_check_range(target_ulong start, target_ulong 
len, int flags)
    page. Return TRUE if the fault was successfully handled. */
 int page_unprotect(target_ulong address, unsigned long pc, void *puc)
 {
-    unsigned int page_index, prot, pindex;
-    PageDesc *p, *p1;
+    unsigned int prot;
+    PageDesc *p;
     target_ulong host_start, host_end, addr;
 
     /* Technically this isn't safe inside a signal handler.  However we
@@ -2456,37 +2456,36 @@ int page_unprotect(target_ulong address, unsigned long 
pc, void *puc)
        practice it seems to be ok.  */
     mmap_lock();
 
-    host_start = address & qemu_host_page_mask;
-    page_index = host_start >> TARGET_PAGE_BITS;
-    p1 = page_find(page_index);
-    if (!p1) {
+    p = page_find(address >> TARGET_PAGE_BITS);
+    if (!p) {
         mmap_unlock();
         return 0;
     }
-    host_end = host_start + qemu_host_page_size;
-    p = p1;
-    prot = 0;
-    for(addr = host_start;addr < host_end; addr += TARGET_PAGE_SIZE) {
-        prot |= p->flags;
-        p++;
-    }
+
     /* if the page was really writable, then we change its
        protection back to writable */
-    if (prot & PAGE_WRITE_ORG) {
-        pindex = (address - host_start) >> TARGET_PAGE_BITS;
-        if (!(p1[pindex].flags & PAGE_WRITE)) {
-            mprotect((void *)g2h(host_start), qemu_host_page_size,
-                     (prot & PAGE_BITS) | PAGE_WRITE);
-            p1[pindex].flags |= PAGE_WRITE;
+    if ((p->flags & PAGE_WRITE_ORG) && !(p->flags & PAGE_WRITE)) {
+        host_start = address & qemu_host_page_mask;
+        host_end = host_start + qemu_host_page_size;
+
+        prot = 0;
+        for (addr = host_start ; addr < host_end ; addr += TARGET_PAGE_SIZE) {
+            p = page_find(addr >> TARGET_PAGE_BITS);
+            p->flags |= PAGE_WRITE;
+            prot |= p->flags;
+
             /* and since the content will be modified, we must invalidate
                the corresponding translated code. */
-            tb_invalidate_phys_page(address, pc, puc);
+            tb_invalidate_phys_page(addr, pc, puc);
 #ifdef DEBUG_TB_CHECK
-            tb_invalidate_check(address);
+            tb_invalidate_check(addr);
 #endif
-            mmap_unlock();
-            return 1;
         }
+        mprotect((void *)g2h(host_start), qemu_host_page_size,
+                 prot & PAGE_BITS);
+
+        mmap_unlock();
+        return 1;
     }
     mmap_unlock();
     return 0;
-- 
1.7.0.2