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Contents of README:Introduction This document covers the native NetBSD compiler runtime. Machine independent sources can be found in common. The crtbegin.c in that directory is a useful template for deriving compact assembler versions. That is preferable to decouple the result from changes in the compiler logic. A new platform should provide the following content in arch/${MACHINE_ARCH} or arch/${MACHINE_CPU}: - Makefile.inc: provides ELFSIZE corresponding to 32/64bit file format. If using the common C code instead of crtbegin.S also provide a -I option to find crtbegin.h in your arch subdir. - crt0.S: provides setup code and the call to ___start. - crtbegin.S or crtbegin.h: see below - crtend.S: see below, most likely just a copy of an existing architecture - crti.S: prefix part of .init/.fini sections, i.e. to ensure stack alignment - crtn.S: suffix part of the .init/.fini sections, i.e. return to caller. 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. Since most of this can easily be done in C code, instead of providing a crtbegin.S you can also chose to use the generic C implementation. Provide a crtbegin.h file instead of crtbegin.S. In there put inline assembler stubs (mostly copied from some other arch) and implement calls to the helper functions __do_global_ctors_aux/__do_global_dtors_aux. |
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CVS/ 16-Aug-2024 05:01 -
arch/ 20-Sep-2014 05:04 -
common/ 20-Jan-2024 04:01 -
Makefile 21-Apr-2021 05:01 675
README 23-Apr-2014 05:53 3.5K
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