| 1 | Preliminary Notes on Porting BFD |
| 2 | -------------------------------- |
| 3 | |
| 4 | The 'host' is the system a tool runs *on*. |
| 5 | The 'target' is the system a tool runs *for*, i.e. |
| 6 | a tool can read/write the binaries of the target. |
| 7 | |
| 8 | Porting to a new host |
| 9 | --------------------- |
| 10 | Pick a name for your host. Call that <host>. |
| 11 | (<host> might be sun4, ...) |
| 12 | Create a file hosts/h-<host>. |
| 13 | |
| 14 | Porting to a new target |
| 15 | ----------------------- |
| 16 | Pick a name for your target. Call that <target>. |
| 17 | You need to create <target>.c and config/mt-<target>. |
| 18 | |
| 19 | config/mt-<target> is a Makefile fragment. |
| 20 | The following is usually enough: |
| 21 | DEFAULT_VECTOR=<target>_vec |
| 22 | SELECT_ARCHITECTURES=bfd_<cpu>_arch |
| 23 | |
| 24 | See the list of cpu types in archures.c, or "ls cpu-*.c". |
| 25 | for more information about .mt and .mh files, see config/README. |
| 26 | |
| 27 | The file <target>.c is the hard part. It implements the |
| 28 | bfd_target <target>_vec, which includes pointers to |
| 29 | functions that do the actual <target>-specific methods. |
| 30 | |
| 31 | Porting to a <target> that uses the a.out binary format |
| 32 | ------------------------------------------------------- |
| 33 | |
| 34 | In this case, the include file aout-target.h probaby does most |
| 35 | of what you need. The program gen-aout generates <target>.c for |
| 36 | you automatically for many a.out systems. Do: |
| 37 | make gen-aout |
| 38 | ./gen-aout <target> > <target>.c |
| 39 | (This only works if you are building on the target ("native"). |
| 40 | If you must make a cross-port from scratch, copy the most |
| 41 | similar existing file that includes aout-target.h, and fix what is wrong.) |
| 42 | |
| 43 | Check the parameters in <target>.c, and fix anything that is wrong. |
| 44 | (Also let us know about it; perhaps we can improve gen-aout.c.) |
| 45 | |
| 46 | TARGET_IS_BIG_ENDIAN_P |
| 47 | Should be defined if <target> is big-endian. |
| 48 | |
| 49 | N_HEADER_IN_TEXT(x) |
| 50 | See discussion in ../include/aout/aout32.h. |
| 51 | |
| 52 | BYTES_IN_WORD |
| 53 | Number of bytes per word. (Usually 4 but can be 8.) |
| 54 | |
| 55 | ARCH |
| 56 | Number of bits per word. (Usually 32, but can be 64.) |
| 57 | |
| 58 | ENTRY_CAN_BE_ZERO |
| 59 | Define if the extry point (start address of an |
| 60 | executable program) can be 0x0. |
| 61 | |
| 62 | TEXT_START_ADDR |
| 63 | The address of the start of the text segemnt in |
| 64 | virtual memory. Normally, the same as the entry point. |
| 65 | |
| 66 | PAGE_SIZE |
| 67 | |
| 68 | SEGMENT_SIZE |
| 69 | Usually, the same as the PAGE_SIZE. |
| 70 | Alignment needed for the data segment. |
| 71 | |
| 72 | TARGETNAME |
| 73 | The name of the target, for run-time lookups. |
| 74 | Usually "a.out-<target>" |