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| -rw-r--r-- | doc/openocd.texi | 26 |
1 files changed, 22 insertions, 4 deletions
diff --git a/doc/openocd.texi b/doc/openocd.texi index 97d2e816..0e57c1af 100644 --- a/doc/openocd.texi +++ b/doc/openocd.texi @@ -6337,10 +6337,10 @@ handler. However, this means that the complete first cacheline in the mini-IC is marked valid, which makes the CPU fetch all exception handlers from the mini-IC, ignoring the code in RAM. -OpenOCD currently does not sync the mini-IC entries with the RAM -contents (which would fail anyway while the target is running), so -the user must provide appropriate values using the @code{xscale -vector_table} command. +To address this situation, OpenOCD provides the @code{xscale +vector_table} command, which allows the user to explicity write +individual entries to either the high or low vector table stored in +the mini-IC. It is recommended to place a pc-relative indirect branch in the vector table, and put the branch destination somewhere in memory. Doing so @@ -6367,6 +6367,24 @@ _vectors: .long real_fiq_handler @end example +Alternatively, you may choose to keep some or all of the mini-IC +vector table entries synced with those written to memory by your +system software. The mini-IC can not be modified while the processor +is executing, but for each vector table entry not previously defined +using the @code{xscale vector_table} command, OpenOCD will copy the +value from memory to the mini-IC every time execution resumes from a +halt. This is done for both high and low vector tables (although the +table not in use may not be mapped to valid memory, and in this case +that copy operation will silently fail). This means that you will +need to briefly halt execution at some strategic point during system +start-up; e.g., after the software has initialized the vector table, +but before exceptions are enabled. A breakpoint can be used to +accomplish this once the appropriate location in the start-up code has +been identified. A watchpoint over the vector table region is helpful +in finding the location if you're not sure. Note that the same +situation exists any time the vector table is modified by the system +software. + The debug handler must be placed somewhere in the address space using the @code{xscale debug_handler} command. The allowed locations for the debug handler are either (0x800 - 0x1fef800) or (0xfe000800 - |