From dc031ee0b1ba11baa00cd7f0769e461a5f396c71 Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Tue, 26 May 2015 03:37:41 -0400 Subject: add rcrt1 start file for fully static-linked PIE static-linked PIE files need startup code to relocate themselves, much like the dynamic linker does. rcrt1.c reuses the code in dlstart.c, stage 1 of the dynamic linker, which in turn reuses crt_arch.h, to achieve static PIE with no new code. only relative relocations are supported. existing toolchains that don't yet support static PIE directly can be repurposed by passing "-shared -Wl,-Bstatic -Wl,-Bsymbolic" instead of "-static -pie" and substituting rcrt1.o in place of crt1.o. all libraries being linked must be built as PIC/PIE; TEXTRELs are not supported at this time. --- Makefile | 4 ++-- crt/rcrt1.c | 15 +++++++++++++++ 2 files changed, 17 insertions(+), 2 deletions(-) create mode 100644 crt/rcrt1.c diff --git a/Makefile b/Makefile index b9668b43..3bd7b4d7 100644 --- a/Makefile +++ b/Makefile @@ -44,7 +44,7 @@ ALL_INCLUDES = $(sort $(wildcard include/*.h include/*/*.h) $(GENH) $(ARCH_INCLU EMPTY_LIB_NAMES = m rt pthread crypt util xnet resolv dl EMPTY_LIBS = $(EMPTY_LIB_NAMES:%=lib/lib%.a) -CRT_LIBS = lib/crt1.o lib/Scrt1.o lib/crti.o lib/crtn.o +CRT_LIBS = lib/crt1.o lib/Scrt1.o lib/rcrt1.o lib/crti.o lib/crtn.o STATIC_LIBS = lib/libc.a SHARED_LIBS = lib/libc.so TOOL_LIBS = lib/musl-gcc.specs @@ -89,7 +89,7 @@ src/ldso/dlstart.lo src/ldso/dynlink.lo: src/internal/dynlink.h arch/$(ARCH)/rel crt/crt1.o crt/Scrt1.o src/ldso/dlstart.lo: $(wildcard arch/$(ARCH)/crt_arch.h) -crt/Scrt1.o: CFLAGS += -fPIC +crt/Scrt1.o crt/rcrt1.o: CFLAGS += -fPIC OPTIMIZE_SRCS = $(wildcard $(OPTIMIZE_GLOBS:%=src/%)) $(OPTIMIZE_SRCS:%.c=%.o) $(OPTIMIZE_SRCS:%.c=%.lo): CFLAGS += -O3 diff --git a/crt/rcrt1.c b/crt/rcrt1.c new file mode 100644 index 00000000..5ac612db --- /dev/null +++ b/crt/rcrt1.c @@ -0,0 +1,15 @@ +#define SHARED +#define START "_start" +#define _dlstart_c _start_c +#include "../src/ldso/dlstart.c" + +int main(); +void _init() __attribute__((weak)); +void _fini() __attribute__((weak)); +_Noreturn int __libc_start_main(int (*)(), int, char **, + void (*)(), void(*)(), void(*)()); + +_Noreturn void __dls2(unsigned char *base, size_t *sp) +{ + __libc_start_main(main, *sp, (void *)(sp+1), _init, _fini, 0); +} -- cgit 1.4.1