NetBSD

History

matt 2ad451b6ca Add a common crtbegin.c file and use a machine dependent crtbegin.h to fill in .init/.fini. Add mips support for USE_COMPILERCRTSTUFF=no (compiled only)		2013-06-22 02:37:09 +00:00
..
alpha	Convert to use c89 function declaration.	2012-03-22 13:02:15 +00:00
arch	Add a common crtbegin.c file and use a machine dependent crtbegin.h to	2013-06-22 02:37:09 +00:00
arm_elf	back out elf note changes since we can use e_flags to determine EABI usage	2012-08-05 01:44:43 +00:00
common	Add a common crtbegin.c file and use a machine dependent crtbegin.h to	2013-06-22 02:37:09 +00:00
common_elf	Use COPTS instead of CFLAGS	2012-08-04 14:59:05 +00:00
hppa	Pass down ELF Auxillary Vectors for static NetBSD binaries too.	2011-03-07 05:09:09 +00:00
ia64	Pass down ELF Auxillary Vectors for static NetBSD binaries too.	2011-03-07 05:09:09 +00:00
m68k_elf	Pass down ELF Auxillary Vectors for static NetBSD binaries too.	2011-03-07 05:09:09 +00:00
mips	Introduce __weakref_visible to handle the different required visibility	2011-02-22 05:45:05 +00:00
powerpc	Make this adhere to the SVR4 ABI.	2011-07-02 07:28:08 +00:00
powerpc64	remove -I- from CPPFLAGS.	2011-10-29 10:28:37 +00:00
sh3_elf	Pass down ELF Auxillary Vectors for static NetBSD binaries too.	2011-03-07 05:09:09 +00:00
sparc64	Slightly simplify and make position independend.	2012-08-10 16:37:31 +00:00
sparc_elf	Make this position independend (for -pie executables)	2012-08-10 12:37:39 +00:00
vax_elf	Don't include <machine/asm.h>	2011-07-30 15:28:58 +00:00
Makefile	Make all earm variants use earm.	2013-04-28 06:09:52 +00:00
README	Switch i386 and x86_64 to the new CRT layout. The crt0.c body is shared	2010-08-07 18:01:32 +00:00

README

Overview of the common runtime support

The common runtime support contains two modules, crtbegin and crtend.
crtbegin is linked before all other object files of the program or
dynamic library, crtend after all other object files.  They frame the
lists of constructors, destructors, Java types and exception handling frames.

If done correctly, crtend contains no code and is therefore position
independent.  crtendS.o is therefore just a link to crtend.o.

crtbegin should be position-independent code.  crtbeginT.o doesn't have
to be PIC as it is statically linked.  The overhead is generally not
worth the trouble though.


Section types:
.ctor: writeable
.dtor: writeable
.eh_frame: read-only if platform allows mixing read-only and read-write
sections.  This is supported by GNU ld.
.jcr: writeable
.init: executable
.fini: executable


Non-local symbols:

Weak references:
- _Jv_RegisterClasses,
- __cxa_finalize (crtbeginS.o)
- __deregister_frame_info
- __register_frame_info

Hidden:
- __dso_handle: pointer to self for crtbeginS.o, NULL otherwise.
- __CTOR_LIST_END__


Initialisation (called from .init):

1.  Check that the init code hasn't started already, otherwise bail out.
2.  If __register_frame_info is NULL, skip to 4
3.  Call __register_frame_info with start of .eh_frame as first argument
    and a data object of at least 8 pointers as second argument.
4:  If _Jv_RegisterClasses is NULL, skip to 6
5:  Call _Jv_RegisterClasses with the first pointer of the .jcr section
    as argument.
6:  Iterate from the end of the .ctor section to the start.  Skip the
    terminating NULL and stop when reaching the starting (void *)-1 element.
    Call the pointers as void (*)(void) functions.


Deinitialisation (called from .fini):

1.  Check if the init code has already started, otherwise bail out.
2.  If this is not crtbeginS.o or __cxa_finalize is NULL, skip to 4.
3.  Call __cxa_finalize with a pointer into this Dynamic Shared Object (DSO)
    as first argument.
4.  Iterate from the start of the .dtor section to the send.  Skip the
    initial (void *)-1 and stop when reaching the terminating NULL element.
    Call the pointers as void (*)(void) functions.
5.  If __deregister_frame_info is NULL, return.
6.  Call __deregister_frame_info with the start of .eh_frame as the argument.