From d89c9e8a63018810bb6a3e2ae55604996cc21e7b Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Sun, 20 Feb 2011 22:30:06 -0500 Subject: [PATCH] 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. --- src/internal/libc.c | 10 +++++++++- src/internal/libc.h | 13 ++++++++++--- 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; +} +#else +struct __libc __libc; +#endif 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 #include -#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()) +#else +extern struct __libc __libc; +#define libc __libc +#endif /* Designed to avoid any overhead in non-threaded processes */ -- 2.25.1