[PATCH v3 10/13] loader: Relocate sigpage on conflict with reserved ranges in ARM.

[Jinoh Kang]

Today, the preloader makes no attempt to remap the sigpage when it
conflicts with reserved addresses.  If libc doesn't have its own signal
restorer, this results in inability to return from signal handlers.

Fix this by relocating sigpage to another address whenever possible.

This behaviour is enabled only when the "WINEPRELOADREMAPSIGPAGE"
environment variable is set to "on-conflict".  In the future, it could
become the default behaviour.

Signed-off-by: Jinoh Kang <jinoh.kang.kr at gmail.com>
---

Notes:
    v1 -> v2: new patch

 loader/preloader.c | 67 ++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 62 insertions(+), 5 deletions(-)

diff --git a/loader/preloader.c b/loader/preloader.c
index 7526a4fcaa4..ab89daa2972 100644
--- a/loader/preloader.c
+++ b/loader/preloader.c
@@ -212,9 +212,12 @@ struct linebuffer
 
 enum vma_type_flags
 {
-    VMA_NORMAL = 0x01,
-    VMA_VDSO   = 0x02,
-    VMA_VVAR   = 0x04,
+    VMA_NORMAL  = 0x01,
+    VMA_VDSO    = 0x02,
+    VMA_VVAR    = 0x04,
+#ifdef __arm__
+    VMA_SIGPAGE = 0x08,
+#endif
 };
 
 struct vma_area
@@ -242,7 +245,10 @@ enum remap_policy
     REMAP_POLICY_SKIP = 2,
     LAST_REMAP_POLICY,
 
-    REMAP_POLICY_DEFAULT_VDSO = REMAP_POLICY_SKIP,
+    REMAP_POLICY_DEFAULT_VDSO    = REMAP_POLICY_SKIP,
+#ifdef __arm__
+    REMAP_POLICY_DEFAULT_SIGPAGE = REMAP_POLICY_SKIP,
+#endif
 };
 
 struct remap_test_block {
@@ -1842,6 +1848,10 @@ static int parse_maps_line( struct vma_area *entry, char *line )
             item.type_flags |= VMA_VDSO;
         else if (wld_strcmp(ptr, "[vvar]") == 0)
             item.type_flags |= VMA_VVAR;
+#ifdef __arm__
+        else if (wld_strcmp(ptr, "[sigpage]") == 0)
+            item.type_flags |= VMA_SIGPAGE;
+#endif
     }
 
     *entry = item;
@@ -2246,6 +2256,47 @@ remap_restore:
     return -1;
 }
 
+#ifdef __arm__
+/* sigpage remapping shouldn't really be necessary, since modern libcs
+ * use their own signal restorer anyway.  But better be safe than sorry...
+ */
+static int remap_sigpage( struct vma_area_list *vma_list, struct preloader_state *state )
+{
+    int result;
+    unsigned long sigpage_start, sigpage_size, delta;
+    void *new_sigpage;
+
+    result = find_remap_area( vma_list, state,
+                              "WINEPRELOADREMAPSIGPAGE", REMAP_POLICY_DEFAULT_SIGPAGE,
+                              VMA_SIGPAGE, &sigpage_start, &sigpage_size );
+    if (result <= 0) return result;
+
+    new_sigpage = wld_mmap( NULL, sigpage_size, PROT_NONE,
+                         MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE, -1, 0 );
+    if (new_sigpage == (void *)-1) return -1;
+
+    delta = (unsigned long)new_sigpage - sigpage_start;
+    if (remap_multiple_vmas( vma_list, delta, VMA_SIGPAGE, 0 ) < 0) goto remap_restore;
+
+    if (test_remap_successful( vma_list, state, sigpage_start, sigpage_size, delta ) < 0)
+    {
+        /* mapping restore done by test_remap_successful */
+        return -1;
+    }
+
+    /* Refresh VMA list */
+    free_vma_list( vma_list );
+    alloc_scan_vma( vma_list );
+    return 1;
+
+remap_restore:
+    if (remap_multiple_vmas( vma_list, delta, -1, 1 ) < 0)
+        fatal_error( "Cannot restore remapped VMAs\n" );
+
+    return -1;
+}
+#endif
+
 static void map_reserve_preload_ranges( const struct vma_area_list *vma_list,
                                         const struct stackarg_info *stackinfo )
 {
@@ -2294,6 +2345,7 @@ void* wld_start( void **stack )
     struct wine_preload_info **wine_main_preload_info;
     struct preloader_state state = { 0 };
     struct vma_area_list vma_list = { NULL };
+    int remap_done;
 
     parse_stackargs( &state.s, *stack );
 
@@ -2326,7 +2378,12 @@ void* wld_start( void **stack )
     alloc_scan_vma( &vma_list );
     map_reserve_preload_ranges( &vma_list, &state.s );
 
-    if (remap_vdso( &vma_list, &state ) > 0) map_reserve_preload_ranges( &vma_list, &state.s );
+    remap_done = 0;
+    remap_done |= remap_vdso( &vma_list, &state ) > 0;
+#ifdef __arm__
+    remap_done |= remap_sigpage( &vma_list, &state ) > 0;
+#endif
+    if (remap_done) map_reserve_preload_ranges( &vma_list, &state.s );
 
     /* add an executable page at the top of the address space to defeat
      * broken no-exec protections that play with the code selector limit */
-- 
2.31.1