Module Name: src
Committed By: dholland
Date: Sat Nov 26 21:17:06 UTC 2016
Modified Files:
src/lib/libc/misc: initfini.c
Log Message:
More of previous.
To generate a diff of this commit:
cvs rdiff -u -r1.12 -r1.13 src/lib/libc/misc/initfini.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/lib/libc/misc/initfini.c
diff -u src/lib/libc/misc/initfini.c:1.12 src/lib/libc/misc/initfini.c:1.13
--- src/lib/libc/misc/initfini.c:1.12 Sat Nov 26 20:38:20 2016
+++ src/lib/libc/misc/initfini.c Sat Nov 26 21:17:06 2016
@@ -1,4 +1,4 @@
-/* $NetBSD: initfini.c,v 1.12 2016/11/26 20:38:20 dholland Exp $ */
+/* $NetBSD: initfini.c,v 1.13 2016/11/26 21:17:06 dholland Exp $ */
/*-
* Copyright (c) 2007 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
*/
#include <sys/cdefs.h>
-__RCSID("$NetBSD: initfini.c,v 1.12 2016/11/26 20:38:20 dholland Exp $");
+__RCSID("$NetBSD: initfini.c,v 1.13 2016/11/26 21:17:06 dholland Exp $");
#ifdef _LIBC
#include "namespace.h"
@@ -83,6 +83,20 @@ struct ps_strings *__ps_strings;
* In static binaries the explicit call is first; in dynamically linked
* binaries the global constructors of libc are called from ld.elf_so
* before crt0.o is reached.
+ *
+ * Note that __ps_strings is set by crt0.o. So in the dynamic case, it
+ * hasn't been set yet when we get here, and __libc_dlauxinfo is not
+ * (ever) assigned. But this is ok because __libc_dlauxinfo is only
+ * used in static binaries, because it's there to substitute for the
+ * dynamic linker. In static binaries __ps_strings will have been set
+ * up when we get here and we get a valid __libc_dlauxinfo.
+ *
+ * This code causes problems for Emacs because Emacs's undump
+ * mechanism saves the __ps_strings value from the startup execution;
+ * then running the resulting binary it gets here before crt0 has
+ * assigned the current execution's value to __ps_strings, and in an
+ * environment with ASLR this can cause the assignment of
+ * __libc_dlauxinfo to receive SIGSEGV.
*/
void __section(".text.startup")
_libc_init(void)
