musl/crt/rcrt1.c

#define START "_start"
#define _dlstart_c _start_c
#include "../ldso/dlstart.c"

int main();
weak void _init();
weak void _fini();
int __libc_start_main(int (*)(), int, char **,
	void (*)(), void(*)(), void(*)());

hidden void __dls2(unsigned char *base, size_t *sp)
{
	__libc_start_main(main, *sp, (void *)(sp+1), _init, _fini, 0);
}
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. 2015-05-26 07:37:41 +00:00			`#define START "_start"`
			`#define _dlstart_c _start_c`
move dynamic linker to its own top-level directory, ldso this eliminates the last need for the SHARED macro to control how files in the src tree are compiled. the same code is used for both libc.a and libc.so, with additional code for the dynamic linker (from the new ldso tree) being added to libc.so but not libc.a. separate .o and .lo object files still exist for the src tree, but the only difference is that the .lo files are built as PIC. in the future, if/when we add dlopen support for static-linked programs, much of the code in dynlink.c may be moved back into the src tree, but properly factored into separate source files. in that case, the code in the ldso tree will be reduced to just the dynamic linker entry point, self-relocation, and loading of libraries needed by the main application. 2016-01-26 00:29:55 +00:00			`#include "../ldso/dlstart.c"`
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. 2015-05-26 07:37:41 +00:00
			`int main();`
define and use internal macros for hidden visibility, weak refs this cleans up what had become widespread direct inline use of "GNU C" style attributes directly in the source, and lowers the barrier to increased use of hidden visibility, which will be useful to recovering some of the efficiency lost when the protected visibility hack was dropped in commit dc2f368e565c37728b0d620380b849c3a1ddd78f, especially on archs where the PLT ABI is costly. 2018-09-05 16:43:34 +00:00			`weak void _init();`
			`weak void _fini();`
remove unnecessary and problematic _Noreturn from crt/ldso startup after commit a48ccc159a5fa061a18419296100ee48a1cd6cc9 removed the use of _Noreturn on the stage3_func type (which only worked due to it being defined to the "GNU C" attribute in C99 mode), GCC could no longer assume that the ends of __dls2 and __dls2b are unreachable, and produced a warning that a function marked _Noreturn returns. also, since commit 4390383b32250a941ec616e8bff6f568a801b1c0, the _Noreturn declaration for __libc_start_main in crt1/rcrt1 has been not only inconsistent with the definition, but wrong. formally, __libc_start_main does return, via a (hopefully) tail call to a helper function after the barrier. incorrect usage of _Noreturn in the declaration was probably formal UB. the _Noreturn specifiers were not useful in any of these places, so remove them all. now, the only remaining usage of _Noreturn is in public interfaces where _Noreturn is part of their contract. 2019-06-25 22:50:05 +00:00			`int __libc_start_main(int ()(), int, char *,`
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. 2015-05-26 07:37:41 +00:00			`void ()(), void()(), void(*)());`

remove unnecessary and problematic _Noreturn from crt/ldso startup after commit a48ccc159a5fa061a18419296100ee48a1cd6cc9 removed the use of _Noreturn on the stage3_func type (which only worked due to it being defined to the "GNU C" attribute in C99 mode), GCC could no longer assume that the ends of __dls2 and __dls2b are unreachable, and produced a warning that a function marked _Noreturn returns. also, since commit 4390383b32250a941ec616e8bff6f568a801b1c0, the _Noreturn declaration for __libc_start_main in crt1/rcrt1 has been not only inconsistent with the definition, but wrong. formally, __libc_start_main does return, via a (hopefully) tail call to a helper function after the barrier. incorrect usage of _Noreturn in the declaration was probably formal UB. the _Noreturn specifiers were not useful in any of these places, so remove them all. now, the only remaining usage of _Noreturn is in public interfaces where _Noreturn is part of their contract. 2019-06-25 22:50:05 +00:00			`hidden void __dls2(unsigned char base, size_t sp)`
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. 2015-05-26 07:37:41 +00:00			`{`
			`__libc_start_main(main, sp, (void )(sp+1), _init, _fini, 0);`
			`}`