Fetch the aux vector for the static libc, and use the entries to

initialize the cache of the system information as it was done for the
dynamic libc. This removes several sysctls from the static binary
startup.

Use the aux vector to fill the single struct dl_phdr_info describing
the static binary itself, to implement dl_iterate_phdr(3) for the
static binaries. [1]

Based on the submission by:	John Marino <draco marino st> [1]
Tested by:   flo (sparc64)
MFC after:	2 weeks

lib/libc/gen/aux.c

@@ -1,5 +1,5 @@
 /*-
- * Copyright 2010 Konstantin Belousov <kib@FreeBSD.ORG>.
+ * Copyright 2010, 2012 Konstantin Belousov <kib@FreeBSD.ORG>.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -36,10 +36,34 @@ __FBSDID("$FreeBSD$");
 #include "un-namespace.h"
 #include "libc_private.h"
 
-Elf_Auxinfo *__elf_aux_vector;
+extern char **environ;
+extern int _DYNAMIC;
+#pragma weak _DYNAMIC
+
+void *__elf_aux_vector;
+static pthread_once_t aux_vector_once = PTHREAD_ONCE_INIT;
+
+static void
+init_aux_vector_once(void)
+{
+	Elf_Addr *sp;
+
+	sp = (Elf_Addr *)environ;
+	while (*sp++ != 0)
+		;
+	__elf_aux_vector = (Elf_Auxinfo *)sp;
+}
+
+void
+__init_elf_aux_vector(void)
+{
+
+	if (&_DYNAMIC != NULL)
+		return;
+	_once(&aux_vector_once, init_aux_vector_once);
+}
 
 static pthread_once_t aux_once = PTHREAD_ONCE_INIT;
-
 static int pagesize, osreldate, canary_len, ncpus, pagesizes_len;
 static char *canary, *pagesizes;
 
@@ -86,6 +110,7 @@ _elf_aux_info(int aux, void *buf, int buflen)
 {
 	int res;
 
+	__init_elf_aux_vector();
 	if (__elf_aux_vector == NULL)
 		return (ENOSYS);
 	_once(&aux_once, init_aux);

lib/libc/gen/dlfcn.c

@@ -34,6 +34,10 @@ __FBSDID("$FreeBSD$");
 #include <dlfcn.h>
 #include <link.h>
 #include <stddef.h>
+#include "namespace.h"
+#include <pthread.h>
+#include "un-namespace.h"
+#include "libc_private.h"
 
 static char sorry[] = "Service unavailable";
 
@@ -138,13 +142,58 @@ _rtld_thread_init(void * li)
 	_rtld_error(sorry);
 }
 
+static pthread_once_t dl_phdr_info_once = PTHREAD_ONCE_INIT;
+static struct dl_phdr_info phdr_info;
+
+static void
+dl_init_phdr_info(void)
+{
+	Elf_Auxinfo *auxp;
+	size_t phent;
+	unsigned int i;
+
+	phent = 0;
+	for (auxp = __elf_aux_vector; auxp->a_type != AT_NULL; auxp++) {
+		switch (auxp->a_type) {
+		case AT_BASE:
+			phdr_info.dlpi_addr = (Elf_Addr)auxp->a_un.a_ptr;
+			break;
+		case AT_EXECPATH:
+			phdr_info.dlpi_name = (const char *)auxp->a_un.a_ptr;
+			break;
+		case AT_PHDR:
+			phdr_info.dlpi_phdr =
+			    (const Elf_Phdr *)auxp->a_un.a_ptr;
+			break;
+		case AT_PHENT:
+			phent = auxp->a_un.a_val;
+			break;
+		case AT_PHNUM:
+			phdr_info.dlpi_phnum = (Elf_Half)auxp->a_un.a_val;
+			break;
+		}
+	}
+	for (i = 0; i < phdr_info.dlpi_phnum; i++) {
+		if (phdr_info.dlpi_phdr[i].p_type == PT_TLS) {
+			phdr_info.dlpi_tls_modid = 1;
+			phdr_info.dlpi_tls_data =
+			    (void*)phdr_info.dlpi_phdr[i].p_vaddr;
+		}
+	}
+	phdr_info.dlpi_adds = 1;
+}
+
 #pragma weak dl_iterate_phdr
 int
 dl_iterate_phdr(int (*callback)(struct dl_phdr_info *, size_t, void *),
     void *data)
 {
-	_rtld_error(sorry);
-	return 0;
+
+	__init_elf_aux_vector();
+	if (__elf_aux_vector == NULL)
+		return (1);
+	_once(&dl_phdr_info_once, dl_init_phdr_info);
+	return (callback(&phdr_info, sizeof(phdr_info), data));
 }
 
 #pragma weak fdlopen

lib/libc/include/libc_private.h

@@ -43,6 +43,15 @@
  */
 extern int	__isthreaded;
 
+/*
+ * Elf_Auxinfo *__elf_aux_vector, the pointer to the ELF aux vector
+ * provided by kernel. Either set for us by rtld, or found at runtime
+ * on stack for static binaries.
+ *
+ * Type is void to avoid polluting whole libc with ELF types.
+ */
+extern void	*__elf_aux_vector;
+
 /*
  * libc should use libc_dlopen internally, which respects a global
  * flag where loading of new shared objects can be restricted.
@@ -229,6 +238,7 @@ int _execvpe(const char *, char * const *, char * const *);
 int _elf_aux_info(int aux, void *buf, int buflen);
 struct dl_phdr_info;
 int __elf_phdr_match_addr(struct dl_phdr_info *, void *);
+void __init_elf_aux_vector(void);
 
 void	_pthread_cancel_enter(int);
 void	_pthread_cancel_leave(int);