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or1k: Allow exception nesting

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Allow exceptions to be nested, which is especially useful with urgent
    interrupts while processing an exception.

    The implementation counts up the nesting level with each call to an
    exception. In the outer exception (level 1), the exception stack is
    started. All nested exceptions just reserve the redzone (scratch
    memory that may be used by compiler) and exception context on the
    stack, but then process on the same scratch.

    Restriction: Impure pointers are shared among all exceptions. This may
    be solved by creating an impure data structure in the stack frame with
    each nested exception.

       * or1k/crt0.S: Add exception nesting
       * or1k/exceptions-asm.S: ditto
       * or1k/util.c: ditto
This commit is contained in:
Jeff Johnston
2015-08-07 14:52:07 -04:00
parent 4098f69c43
commit 31cf34f849
4 changed files with 149 additions and 39 deletions
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19
libgloss/or1k/exceptions-asm.S
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@ -27,6 +27,7 @@
#define EXCEPTION_STACK_SIZE 136
.extern _or1k_exception_handler_table
.extern _or1k_exception_level
/* -------------------------------------------------------------------------- */
/*!Function to call appropriate exception handler
@ -159,6 +160,24 @@ _or1k_exception_handler:
#endif
l.sw 0(r21),r20
/* Decrement the exception nesting level */
// Load the exception level entry
l.movhi r2,hi(_or1k_exception_level)
l.ori r2,r2,lo(_or1k_exception_level)
#ifdef __OR1K_MULTICORE__
// In multicore this is the pointer to an array
// Load pointer value
l.lwz r2,0(r2)
// Add word offset of this core's nesting level
l.add r2,r2,r22
#endif
// Load the nesting level entry
l.lwz r3,0(r2)
// Decrement nesting level
l.addi r3,r3,-1
// Store back the nesting level
l.sw 0(r2),r3
/* Restore state */
l.lwz r2,0x80(r1)
l.mtspr r0,r2,OR1K_SPR_SYS_EPCR_BASE