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jeremybenn |
Preliminary Notes on Porting BFD
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The 'host' is the system a tool runs *on*.
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The 'target' is the system a tool runs *for*, i.e.
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a tool can read/write the binaries of the target.
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Porting to a new host
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---------------------
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Pick a name for your host. Call that .
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( might be sun4, ...)
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Create a file hosts/.mh.
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Porting to a new target
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-----------------------
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Pick a name for your target. Call that .
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Call the name for your CPU architecture .
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You need to create .c and config/.mt,
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and add a case for it to a case statements in bfd/configure.host and
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bfd/config.bfd, which associates each canonical host type with a BFD
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host type (used as the base of the makefile fragment names), and to the
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table in bfd/configure.in which associates each target vector with
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the .o files it uses.
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config/.mt is a Makefile fragment.
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The following is usually enough:
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DEFAULT_VECTOR=_vec
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SELECT_ARCHITECTURES=bfd__arch
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See the list of cpu types in archures.c, or "ls cpu-*.c".
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If your architecture is new, you need to add it to the tables
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in bfd/archures.c, opcodes/configure.in, and binutils/objdump.c.
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For more information about .mt and .mh files, see config/README.
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The file .c is the hard part. It implements the
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bfd_target _vec, which includes pointers to
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functions that do the actual -specific methods.
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Porting to a that uses the a.out binary format
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-------------------------------------------------------
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In this case, the include file aout-target.h probaby does most
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of what you need. The program gen-aout generates .c for
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you automatically for many a.out systems. Do:
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make gen-aout
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./gen-aout > .c
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(This only works if you are building on the target ("native").
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If you must make a cross-port from scratch, copy the most
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similar existing file that includes aout-target.h, and fix what is wrong.)
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Check the parameters in .c, and fix anything that is wrong.
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(Also let us know about it; perhaps we can improve gen-aout.c.)
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TARGET_IS_BIG_ENDIAN_P
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Should be defined if is big-endian.
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N_HEADER_IN_TEXT(x)
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See discussion in ../include/aout/aout64.h.
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BYTES_IN_WORD
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Number of bytes per word. (Usually 4 but can be 8.)
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ARCH
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Number of bits per word. (Usually 32, but can be 64.)
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ENTRY_CAN_BE_ZERO
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Define if the extry point (start address of an
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executable program) can be 0x0.
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TEXT_START_ADDR
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The address of the start of the text segemnt in
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virtual memory. Normally, the same as the entry point.
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TARGET_PAGE_SIZE
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SEGMENT_SIZE
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Usually, the same as the TARGET_PAGE_SIZE.
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Alignment needed for the data segment.
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TARGETNAME
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The name of the target, for run-time lookups.
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Usually "a.out-"
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