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| author | Rich Felker <dalias@aerifal.cx> | 2011-02-20 22:30:06 -0500 |
|---|---|---|
| committer | Rich Felker <dalias@aerifal.cx> | 2011-02-20 22:30:06 -0500 |
| commit | d89c9e8a63018810bb6a3e2ae55604996cc21e7b (patch) | |
| tree | 294b84c7be389e049d478ca9a5777276f84c4a88 | |
| parent | 4ee039f3545976f9e3e25a7e5d7b58f1f2316dc3 (diff) | |
| download | musl-d89c9e8a63018810bb6a3e2ae55604996cc21e7b.tar.gz | |
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.
| -rw-r--r-- | src/internal/libc.c | 10 | ||||
| -rw-r--r-- | 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 <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()) +#else +extern struct __libc __libc; +#define libc __libc +#endif /* Designed to avoid any overhead in non-threaded processes */ |