e83f7ba2c9
. file- and functionality-compatible with previous situation
(FreeBSD csu) (with a crt1.o -> crt0.o symlink in /usr/lib)
. harmonizes source with netbsd
. harmonizes linker invocation (e.g. clang) with netbsd
. helpful to get some arm code in there for the arm port project
63 lines
2.3 KiB
Text
63 lines
2.3 KiB
Text
Overview of the common runtime support
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The common runtime support contains two modules, crtbegin and crtend.
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crtbegin is linked before all other object files of the program or
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dynamic library, crtend after all other object files. They frame the
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lists of constructors, destructors, Java types and exception handling frames.
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If done correctly, crtend contains no code and is therefore position
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independent. crtendS.o is therefore just a link to crtend.o.
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crtbegin should be position-independent code. crtbeginT.o doesn't have
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to be PIC as it is statically linked. The overhead is generally not
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worth the trouble though.
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Section types:
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.ctor: writeable
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.dtor: writeable
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.eh_frame: read-only if platform allows mixing read-only and read-write
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sections. This is supported by GNU ld.
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.jcr: writeable
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.init: executable
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.fini: executable
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Non-local symbols:
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Weak references:
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- _Jv_RegisterClasses,
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- __cxa_finalize (crtbeginS.o)
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- __deregister_frame_info
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- __register_frame_info
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Hidden:
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- __dso_handle: pointer to self for crtbeginS.o, NULL otherwise.
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- __CTOR_LIST_END__
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Initialisation (called from .init):
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1. Check that the init code hasn't started already, otherwise bail out.
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2. If __register_frame_info is NULL, skip to 4
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3. Call __register_frame_info with start of .eh_frame as first argument
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and a data object of at least 8 pointers as second argument.
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4: If _Jv_RegisterClasses is NULL, skip to 6
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5: Call _Jv_RegisterClasses with the first pointer of the .jcr section
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as argument.
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6: Iterate from the end of the .ctor section to the start. Skip the
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terminating NULL and stop when reaching the starting (void *)-1 element.
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Call the pointers as void (*)(void) functions.
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Deinitialisation (called from .fini):
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1. Check if the init code has already started, otherwise bail out.
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2. If this is not crtbeginS.o or __cxa_finalize is NULL, skip to 4.
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3. Call __cxa_finalize with a pointer into this Dynamic Shared Object (DSO)
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as first argument.
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4. Iterate from the start of the .dtor section to the send. Skip the
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initial (void *)-1 and stop when reaching the terminating NULL element.
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Call the pointers as void (*)(void) functions.
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5. If __deregister_frame_info is NULL, return.
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6. Call __deregister_frame_info with the start of .eh_frame as the argument.
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