svn commit: r318313 - head/libexec/rtld-elf

[Konstantin Belousov]

Author: kib
Date: Mon May 15 18:48:58 2017
New Revision: 318313
URL: https://svnweb.freebsd.org/changeset/base/318313

Log:
  Make ld-elf.so.1 directly executable.
  
  Check if passed phdr is actually phdr of the interpreter itself, and
  decide that this is the case of direct execution.  In this case, the
  binary to activate is specified in the argv[1].  After opening it,
  shift down on-stack structure with argv, env and aux vectors to
  emulate execution of the binary and not of the interpreter.
  
  Reviewed by:	emaste
  Sponsored by:	The FreeBSD Foundation
  MFC after:	2 weeks
  Differential revision:	https://reviews.freebsd.org/D10701

Modified:
  head/libexec/rtld-elf/rtld.c

Modified: head/libexec/rtld-elf/rtld.c
==============================================================================
--- head/libexec/rtld-elf/rtld.c	Mon May 15 18:47:25 2017	(r318312)
+++ head/libexec/rtld-elf/rtld.c	Mon May 15 18:48:58 2017	(r318313)
@@ -339,13 +339,14 @@ _LD(const char *var)
 func_ptr_type
 _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp)
 {
-    Elf_Auxinfo *aux, *auxp, *aux_info[AT_COUNT];
+    Elf_Auxinfo *aux, *auxp, *auxpf, *aux_info[AT_COUNT];
     Objlist_Entry *entry;
     Obj_Entry *last_interposer, *obj, *preload_tail;
     const Elf_Phdr *phdr;
     Objlist initlist;
     RtldLockState lockstate;
-    char **argv, *argv0, **env, *kexecpath, *library_path_rpath;
+    Elf_Addr *argcp;
+    char **argv, *argv0, **env, **envp, *kexecpath, *library_path_rpath;
     caddr_t imgentry;
     char buf[MAXPATHLEN];
     int argc, fd, i, mib[2], phnum;
@@ -359,6 +360,7 @@ _rtld(Elf_Addr *sp, func_ptr_type *exit_
      */
 
     /* Find the auxiliary vector on the stack. */
+    argcp = sp;
     argc = *sp++;
     argv = (char **) sp;
     sp += argc + 1;	/* Skip over arguments and NULL terminator */
@@ -410,6 +412,57 @@ _rtld(Elf_Addr *sp, func_ptr_type *exit_
 
     md_abi_variant_hook(aux_info);
 
+    fd = -1;
+    if (aux_info[AT_EXECFD] != NULL) {
+	fd = aux_info[AT_EXECFD]->a_un.a_val;
+    } else {
+	assert(aux_info[AT_PHDR] != NULL);
+	phdr = (const Elf_Phdr *)aux_info[AT_PHDR]->a_un.a_ptr;
+	if (phdr == obj_rtld.phdr) {
+	    dbg("opening main program in direct exec mode");
+	    if (argc >= 2) {
+		argv0 = argv[1];
+		fd = open(argv0, O_RDONLY | O_CLOEXEC | O_VERIFY);
+		if (fd == -1) {
+		    rtld_printf("Opening %s: %s\n", argv0,
+		      rtld_strerror(errno));
+		    rtld_die();
+		}
+
+		/*
+		 * For direct exec mode, argv[0] is the interpreter
+		 * name, we must remove it and shift arguments left by
+		 * 1 before invoking binary main.  Since stack layout
+		 * places environment pointers and aux vectors right
+		 * after the terminating NULL, we must shift
+		 * environment and aux as well.
+		 * XXX Shift will be > 1 when options are implemented.
+		 */
+		do {
+		    *argv = *(argv + 1);
+		    argv++;
+		} while (*argv != NULL);
+		*argcp -= 1;
+		main_argc = argc - 1;
+		environ = env = envp = argv;
+		do {
+		    *envp = *(envp + 1);
+		    envp++;
+		} while (*envp != NULL);
+		aux = auxp = (Elf_Auxinfo *)envp;
+		auxpf = (Elf_Auxinfo *)(envp + 1);
+		for (;; auxp++, auxpf++) {
+		    *auxp = *auxpf;
+		    if (auxp->a_type == AT_NULL)
+			    break;
+		}
+	    } else {
+		rtld_printf("no binary\n");
+		rtld_die();
+	    }
+	}
+    }
+
     ld_bind_now = getenv(_LD("BIND_NOW"));
 
     /* 
@@ -470,8 +523,7 @@ _rtld(Elf_Addr *sp, func_ptr_type *exit_
      * Load the main program, or process its program header if it is
      * already loaded.
      */
-    if (aux_info[AT_EXECFD] != NULL) {	/* Load the main program. */
-	fd = aux_info[AT_EXECFD]->a_un.a_val;
+    if (fd != -1) {	/* Load the main program. */
 	dbg("loading main program");
 	obj_main = map_object(fd, argv0, NULL);
 	close(fd);
@@ -492,7 +544,7 @@ _rtld(Elf_Addr *sp, func_ptr_type *exit_
 	    rtld_die();
     }
 
-    if (aux_info[AT_EXECPATH] != NULL) {
+    if (aux_info[AT_EXECPATH] != NULL && fd == -1) {
 	    kexecpath = aux_info[AT_EXECPATH]->a_un.a_ptr;
 	    dbg("AT_EXECPATH %p %s", kexecpath, kexecpath);
 	    if (kexecpath[0] == '/')
@@ -504,7 +556,7 @@ _rtld(Elf_Addr *sp, func_ptr_type *exit_
 	    else
 		    obj_main->path = xstrdup(buf);
     } else {
-	    dbg("No AT_EXECPATH");
+	    dbg("No AT_EXECPATH or direct exec");
 	    obj_main->path = xstrdup(argv0);
     }
     dbg("obj_main path %s", obj_main->path);