linux-user: remove MAX_ARG_PAGES limit

Instead of creating a temporary copy for the whole environment and
the arguments, directly copy everything to the target stack.

For this to work, we have to change the order of stack creation and
copying the arguments.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>

1 files changed, 55 insertions, 55 deletions

diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index ad46530f83..fdae6a6cd1 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -1373,66 +1373,69 @@ static bool elf_check_ehdr(struct elfhdr *ehdr)
  * to be put directly into the top of new user memory.
  *
  */
-static abi_ulong copy_elf_strings(int argc,char ** argv, void **page,
-                                  abi_ulong p)
+static abi_ulong copy_elf_strings(int argc, char **argv, char *scratch,
+                                  abi_ulong p, abi_ulong stack_limit)
 {
-    char *tmp, *tmp1, *pag = NULL;
-    int len, offset = 0;
+    char *tmp;
+    int len, offset;
+    abi_ulong top = p;
 
     if (!p) {
         return 0;       /* bullet-proofing */
     }
+
+    offset = ((p - 1) % TARGET_PAGE_SIZE) + 1;
+
     while (argc-- > 0) {
         tmp = argv[argc];
         if (!tmp) {
             fprintf(stderr, "VFS: argc is wrong");
             exit(-1);
         }
-        tmp1 = tmp;
-        while (*tmp++);
-        len = tmp - tmp1;
-        if (p < len) {  /* this shouldn't happen - 128kB */
+        len = strlen(tmp) + 1;
+        tmp += len;
+
+        if (len > (p - stack_limit)) {
             return 0;
         }
         while (len) {
-            --p; --tmp; --len;
-            if (--offset < 0) {
-                offset = p % TARGET_PAGE_SIZE;
-                pag = (char *)page[p/TARGET_PAGE_SIZE];
-                if (!pag) {
-                    pag = g_try_malloc0(TARGET_PAGE_SIZE);
-                    page[p/TARGET_PAGE_SIZE] = pag;
-                    if (!pag)
-                        return 0;
-                }
-            }
-            if (len == 0 || offset == 0) {
-                *(pag + offset) = *tmp;
-            }
-            else {
-                int bytes_to_copy = (len > offset) ? offset : len;
-                tmp -= bytes_to_copy;
-                p -= bytes_to_copy;
-                offset -= bytes_to_copy;
-                len -= bytes_to_copy;
-                memcpy_fromfs(pag + offset, tmp, bytes_to_copy + 1);
+            int bytes_to_copy = (len > offset) ? offset : len;
+            tmp -= bytes_to_copy;
+            p -= bytes_to_copy;
+            offset -= bytes_to_copy;
+            len -= bytes_to_copy;
+
+            memcpy_fromfs(scratch + offset, tmp, bytes_to_copy);
+
+            if (offset == 0) {
+                memcpy_to_target(p, scratch, top - p);
+                top = p;
+                offset = TARGET_PAGE_SIZE;
             }
         }
     }
+    if (offset) {
+        memcpy_to_target(p, scratch + offset, top - p);
+    }
+
     return p;
 }
 
-static abi_ulong setup_arg_pages(abi_ulong p, struct linux_binprm *bprm,
+/* Older linux kernels provide up to MAX_ARG_PAGES (default: 32) of
+ * argument/environment space. Newer kernels (>2.6.33) allow more,
+ * dependent on stack size, but guarantee at least 32 pages for
+ * backwards compatibility.
+ */
+#define STACK_LOWER_LIMIT (32 * TARGET_PAGE_SIZE)
+
+static abi_ulong setup_arg_pages(struct linux_binprm *bprm,
                                  struct image_info *info)
 {
-    abi_ulong stack_base, size, error, guard;
-    int i;
+    abi_ulong size, error, guard;
 
-    /* Create enough stack to hold everything.  If we don't use
-       it for args, we'll use it for something else.  */
     size = guest_stack_size;
-    if (size < MAX_ARG_PAGES*TARGET_PAGE_SIZE) {
-        size = MAX_ARG_PAGES*TARGET_PAGE_SIZE;
+    if (size < STACK_LOWER_LIMIT) {
+        size = STACK_LOWER_LIMIT;
     }
     guard = TARGET_PAGE_SIZE;
     if (guard < qemu_real_host_page_size) {
@@ -1450,18 +1453,8 @@ static abi_ulong setup_arg_pages(abi_ulong p, struct linux_binprm *bprm,
     target_mprotect(error, guard, PROT_NONE);
 
     info->stack_limit = error + guard;
-    stack_base = info->stack_limit + size - MAX_ARG_PAGES*TARGET_PAGE_SIZE;
-    p += stack_base;
-
-    for (i = 0 ; i < MAX_ARG_PAGES ; i++) {
-        if (bprm->page[i]) {
-            /* FIXME - check return value of memcpy_to_target() for failure */
-            memcpy_to_target(stack_base, bprm->page[i], TARGET_PAGE_SIZE);
-            g_free(bprm->page[i]);
-        }
-        stack_base += TARGET_PAGE_SIZE;
-    }
-    return p;
+
+    return info->stack_limit + size - sizeof(void *);
 }
 
 /* Map and zero the bss.  We need to explicitly zero any fractional pages
@@ -2203,6 +2196,7 @@ int load_elf_binary(struct linux_binprm *bprm, struct image_info *info)
     struct image_info interp_info;
     struct elfhdr elf_ex;
     char *elf_interpreter = NULL;
+    char *scratch;
 
     info->start_mmap = (abi_ulong)ELF_START_MMAP;
 
@@ -2214,18 +2208,24 @@ int load_elf_binary(struct linux_binprm *bprm, struct image_info *info)
        when we load the interpreter.  */
     elf_ex = *(struct elfhdr *)bprm->buf;
 
-    bprm->p = copy_elf_strings(1, &bprm->filename, bprm->page, bprm->p);
-    bprm->p = copy_elf_strings(bprm->envc,bprm->envp,bprm->page,bprm->p);
-    bprm->p = copy_elf_strings(bprm->argc,bprm->argv,bprm->page,bprm->p);
+    /* Do this so that we can load the interpreter, if need be.  We will
+       change some of these later */
+    bprm->p = setup_arg_pages(bprm, info);
+
+    scratch = g_new0(char, TARGET_PAGE_SIZE);
+    bprm->p = copy_elf_strings(1, &bprm->filename, scratch,
+                               bprm->p, info->stack_limit);
+    bprm->p = copy_elf_strings(bprm->envc, bprm->envp, scratch,
+                               bprm->p, info->stack_limit);
+    bprm->p = copy_elf_strings(bprm->argc, bprm->argv, scratch,
+                               bprm->p, info->stack_limit);
+    g_free(scratch);
+
     if (!bprm->p) {
         fprintf(stderr, "%s: %s\n", bprm->filename, strerror(E2BIG));
         exit(-1);
     }
 
-    /* Do this so that we can load the interpreter, if need be.  We will
-       change some of these later */
-    bprm->p = setup_arg_pages(bprm->p, bprm, info);
-
     if (elf_interpreter) {
         load_elf_interp(elf_interpreter, &interp_info, bprm->buf);