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Altera_Forum
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14 years ago

Modifying EPCS bootloader

Skip to tl;dr at the bottom if so inclined. Background and such is there to cover some possible questions. background: (Developing in Q10.1) I am developing a project with two separate fir...
Altera_Forum's avatar
Altera_Forum
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14 years ago

I agree with ljabbott's earlier comment:

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It seems to be just an option to build the elf file with a particular offset for debugging purposes. This only affects the ELF headers, as the actual assembled code is position-independent.

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The assembler code in the boot loader was very carefully written to avoid any absolute memory addresses as indicated in the code comments:
// This is not a very complex job, but there is one requirement
// that makes this program tricky:
//
//   (*) We want to make the exact-same binary code run on any system,
//       at any (cache-line-aligned) address, and still work properly.
//
// Thus, this program must be position-independent, use no
// memory-variables, and derive all payload-specific data from the
// payload itself.
No matter what CODE_BASE you specify, the resulting hex file should be the same. You do not need to recompile the boot loader if you change the EPCS controller address (unless you modified the stock boot loader to include absolute references).