path: root/src/internal
diff options
authorRich Felker <>2011-02-20 22:30:06 -0500
committerRich Felker <>2011-02-20 22:30:06 -0500
commitd89c9e8a63018810bb6a3e2ae55604996cc21e7b (patch)
tree294b84c7be389e049d478ca9a5777276f84c4a88 /src/internal
parent4ee039f3545976f9e3e25a7e5d7b58f1f2316dc3 (diff)
use an accessor function for __libc data pointer when compiled as PIC
prior to this change, a large portion of libc was unusable prior to relocation by the dynamic linker, due to dependence on the global data in the __libc structure and the need to obtain its address through the GOT. with this patch, the accessor function __libc_loc is now able to obtain the address of __libc via PC-relative addressing without using the GOT. this means the majority of libc functionality is now accessible right away. naturally, the above statements all depend on having an architecture where PC-relative addressing and jumps/calls are feasible, and a compiler that generates the appropriate code.
Diffstat (limited to 'src/internal')
2 files changed, 19 insertions, 4 deletions
diff --git a/src/internal/libc.c b/src/internal/libc.c
index 5e8e9d95..954efedf 100644
--- a/src/internal/libc.c
+++ b/src/internal/libc.c
@@ -1,3 +1,11 @@
#include "libc.h"
-struct libc libc;
+#ifdef __PIC__
+struct __libc *__libc_loc()
+ static struct __libc __libc;
+ return &__libc;
+struct __libc __libc;
diff --git a/src/internal/libc.h b/src/internal/libc.h
index ea221b6f..8a84be0b 100644
--- a/src/internal/libc.h
+++ b/src/internal/libc.h
@@ -4,8 +4,7 @@
#include <stdlib.h>
#include <stdio.h>
-#define libc __libc
-extern struct libc {
+struct __libc {
void (*lock)(volatile int *);
void (*cancelpt)(int);
int (*atexit)(void (*)(void));
@@ -16,7 +15,15 @@ extern struct libc {
int (*rsyscall)(int, long, long, long, long, long, long);
void (**tsd_keys)(void *);
void (*fork_handler)(int);
-} libc;
+#ifdef __PIC__
+extern struct __libc *__libc_loc(void) __attribute__((const));
+#define libc (*__libc_loc())
+extern struct __libc __libc;
+#define libc __libc
/* Designed to avoid any overhead in non-threaded processes */