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diff --git a/libgloss/or1k/README b/libgloss/or1k/README deleted file mode 100644 index e9b0a2048..000000000 --- a/libgloss/or1k/README +++ /dev/null @@ -1,77 +0,0 @@ -This document describes the internals of the port for OpenRISC -1000. The API is documented in or1k-support.h as Doxygen comments. - -# Data Structures - -+----------------+ 0x0 -| vectors | -+----------------+ -| text,data,.. | -+----------------+ -| bss | -+----------------+ -| heap | -| vv | -| | -| ^^ | -| stack(s) | -+----------------+ _or1k_board_mem_base + - _or1k_board_mem_size - -## Stack and Heap - -The stack is allocated at the end of available physical memory which -is defined by each board as _or1k_board_mem_base and -_or1k_board_mem_size. The _or1k_stack_top and _or1k_stack_bottom are -determined by those variables and _or1k_stack_size (which may be -overwritten in _or1k_board_init_early). - -A second stack for exceptions is allocated as we allow exceptions to -be arbitrary complex and call C functions etc. It is not an option to -re-use the current software stack as we want to be so generic, that -this can also be a virtual memory stack at moment of exception. The -exception starts below the normal software stack and is -_or1k_exception_stack_size large. - -Multicore: For each core a stack and exception stack is allocated and -the stack pointer set at boot. That is: sp(core0) = _or1k_stack_top, -sp(core1) = _or1k_stack_top - _or1k_stack_size, etc. - -## _or1k_stack_core (multicore only) - -An array of pointers to the software stacks (size: -4*or1k_numcores()). It is dynamically allocated from heap in or1k_init -by calling sbrk(). The pointers contain the values for stack top -pointers as described above. This variable is essentially used on boot -of the slave cores to configure the stack register. - -## _or1k_exception_stack_core (multicore only) - -An array of pointers to the exception stacks (size: -4*or1k_numcores()). It is allocated identical as the stack_core -array. It is loaded whenever an exception occurs to start with a clean -stack in the exception. - -## _or1k_exception_handler_table - -A table of function pointers to the handlers of the exceptions. The -generic exception handler checks if an exception handler is registered -and calls it. There are 30 exceptions defined (0x0 is not an exception -vector and 0x100 is reset which is static). This array resides in BSS -and is therefore initialized as 0 (no handler registered) after start. - -Multicore: As the number of course is not known at compile time, the -variable is a pointer to and array of arrays (cores x 30) which is -allocated in or1k_init() on heap (using sbrk). - -## _or1k_interrupt_handler_table and _or1k_interrupt_handler_table_data_ptr - -The interrupt handlers are stored identical to to the exception handler table. - -## _or1k_reent - -The struct _or1k_reent contains formerly global data and allows for -reentrancy. In the single core case, this is an allocated object, -while it is a pointer to an array of structs in the multicore library. -It is allocated in _or1k_reent_init() on the heap. - |