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From: Konstantin Belousov <kib@FreeBSD.org>
Date: Sat, 8 Jan 2011 17:13:43 +0000 (UTC)
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Subject: svn commit: r217154 - head/lib/libc/gen
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Author: kib
Date: Sat Jan  8 17:13:43 2011
New Revision: 217154
URL: http://svn.freebsd.org/changeset/base/217154

Log:
  Implement __pthread_map_stacks_exec() callback for libc, to change the
  stack protection to allow execution for single-threaded processes.

Modified:
  head/lib/libc/gen/Symbol.map
  head/lib/libc/gen/dlfcn.c
  head/lib/libc/gen/elf_utils.c

Modified: head/lib/libc/gen/Symbol.map
==============================================================================
--- head/lib/libc/gen/Symbol.map	Sat Jan  8 17:11:49 2011	(r217153)
+++ head/lib/libc/gen/Symbol.map	Sat Jan  8 17:13:43 2011	(r217154)
@@ -453,6 +453,7 @@ FBSDprivate_1.0 {
 	_rtld_atfork_pre;
 	_rtld_atfork_post;
 	_rtld_error;		/* for private use */
+	_rtld_get_stack_prot;
 	_rtld_thread_init;	/* for private use */
 	__elf_phdr_match_addr;
 	_err;
@@ -499,4 +500,5 @@ FBSDprivate_1.0 {
 	_libc_sem_getvalue_compat;
 
 	__elf_aux_vector;
+	__pthread_map_stacks_exec;
 };

Modified: head/lib/libc/gen/dlfcn.c
==============================================================================
--- head/lib/libc/gen/dlfcn.c	Sat Jan  8 17:11:49 2011	(r217153)
+++ head/lib/libc/gen/dlfcn.c	Sat Jan  8 17:13:43 2011	(r217154)
@@ -30,6 +30,7 @@ __FBSDID("$FreeBSD$");
 /*
  * Linkage to services provided by the dynamic linker.
  */
+#include <sys/mman.h>
 #include <dlfcn.h>
 #include <link.h>
 #include <stddef.h>
@@ -165,3 +166,12 @@ _rtld_addr_phdr(const void *addr, struct
 
 	return (0);
 }
+
+#pragma weak _rtld_get_stack_prot
+int
+_rtld_get_stack_prot(void)
+{
+
+	return (PROT_EXEC | PROT_READ | PROT_WRITE);
+}
+

Modified: head/lib/libc/gen/elf_utils.c
==============================================================================
--- head/lib/libc/gen/elf_utils.c	Sat Jan  8 17:11:49 2011	(r217153)
+++ head/lib/libc/gen/elf_utils.c	Sat Jan  8 17:13:43 2011	(r217154)
@@ -26,7 +26,12 @@
  * $FreeBSD$
  */
 
+#include <sys/types.h>
+#include <sys/mman.h>
+#include <sys/resource.h>
+#include <sys/sysctl.h>
 #include <link.h>
+#include <stddef.h>
 
 int
 __elf_phdr_match_addr(struct dl_phdr_info *phdr_info, void *addr)
@@ -45,3 +50,25 @@ __elf_phdr_match_addr(struct dl_phdr_inf
 	}
 	return (i != phdr_info->dlpi_phnum);
 }
+
+#pragma weak __pthread_map_stacks_exec
+void
+__pthread_map_stacks_exec(void)
+{
+	int mib[2];
+	struct rlimit rlim;
+	u_long usrstack;
+	size_t len;
+	
+	mib[0] = CTL_KERN;
+	mib[1] = KERN_USRSTACK;
+	len = sizeof(usrstack);
+	if (sysctl(mib, sizeof(mib) / sizeof(mib[0]), &usrstack, &len, NULL, 0)
+	    == -1)
+		return;
+	if (getrlimit(RLIMIT_STACK, &rlim) == -1)
+		return;
+	mprotect((void *)(uintptr_t)(usrstack - rlim.rlim_cur),
+	    rlim.rlim_cur, _rtld_get_stack_prot());
+}
+