linux-user: save auxv length

We create our own AUXV segment on stack and save a pointer to it.
However we don't save the length of it, so any code that wants to
do anything useful with it later on has to walk it again.

Instead, let's remember the length of our AUXV segment. This
simplifies later uses by a lot.

(edited by Riku to apply to qemu HEAD)
Signed-off-by: NAlexander Graf <agraf@suse.de>
Signed-off-by: NRiku Voipio <riku.voipio@iki.fi>

linux-user/elfload.c

@@ -1245,6 +1245,7 @@ static abi_ulong create_elf_tables(abi_ulong p, int argc, int envc,
                                    struct image_info *interp_info)
 {
     abi_ulong sp;
+    abi_ulong sp_auxv;
     int size;
     int i;
     abi_ulong u_rand_bytes;
@@ -1316,6 +1317,7 @@ static abi_ulong create_elf_tables(abi_ulong p, int argc, int envc,
         sp -= n; put_user_ual(id, sp);          \
     } while(0)
 
+    sp_auxv = sp;
     NEW_AUX_ENT (AT_NULL, 0);
 
     /* There must be exactly DLINFO_ITEMS entries here.  */
@@ -1346,6 +1348,7 @@ static abi_ulong create_elf_tables(abi_ulong p, int argc, int envc,
 #undef NEW_AUX_ENT
 
     info->saved_auxv = sp;
+    info->auxv_len = sp_auxv - sp;
 
     sp = loader_build_argptr(envc, argc, sp, p, 0);
     return sp;
@@ -2326,9 +2329,8 @@ static void fill_auxv_note(struct memelfnote *note, const TaskState *ts)
 {
     elf_addr_t auxv = (elf_addr_t)ts->info->saved_auxv;
     elf_addr_t orig_auxv = auxv;
-    abi_ulong val;
     void *ptr;
-    int i, len;
+    int len = ts->info->auxv_len;
 
     /*
      * Auxiliary vector is stored in target process stack.  It contains
@@ -2336,15 +2338,6 @@ static void fill_auxv_note(struct memelfnote *note, const TaskState *ts)
      * strictly necessary but we do it here for sake of completeness.
      */
 
-    /* find out length of the vector, AT_NULL is terminator */
-    i = len = 0;
-    do {
-        get_user_ual(val, auxv);
-        i += 2;
-        auxv += 2 * sizeof (elf_addr_t);
-    } while (val != AT_NULL);
-    len = i * sizeof (elf_addr_t);
-
     /* read in whole auxv vector and copy it to memelfnote */
     ptr = lock_user(VERIFY_READ, orig_auxv, len, 0);
     if (ptr != NULL) {

linux-user/qemu.h

@@ -48,6 +48,7 @@ struct image_info {
         abi_ulong       code_offset;
         abi_ulong       data_offset;
         abi_ulong       saved_auxv;
+        abi_ulong       auxv_len;
         abi_ulong       arg_start;
         abi_ulong       arg_end;
 	int		personality;