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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
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@jjohnstn
jjohnstn committed Aug 7, 2015
1 parent 4098f69 commit 31cf34f
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Showing 4 changed files with 149 additions and 39 deletions.
6 changes: 6 additions & 0 deletions libgloss/ChangeLog
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Original file line number Diff line number Diff line change
@@ -1,3 +1,9 @@
2015-08-07 Stefan Wallentowitz <[email protected]>

* or1k/crt0.S: Add exception nesting
* or1k/exceptions-asm.S: ditto
* or1k/util.c: ditto

2015-08-07 Stefan Wallentowitz <[email protected]>

* or1k/sbrk.c: Make heap end globally visible
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149 changes: 110 additions & 39 deletions libgloss/or1k/crt0.S
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Original file line number Diff line number Diff line change
Expand Up @@ -66,14 +66,18 @@
// function
#define EXCEPTION_STACK_FRAME 136

#define REDZONE 128

.extern _or1k_stack_top /* points to the next address after the stack */
.extern _or1k_stack_bottom /* points to the last address in the stack */
.extern _or1k_exception_stack_top
.extern _or1k_exception_stack_bottom
.extern _or1k_exception_level /* Nesting level of exceptions */

.section .data
.global _or1k_stack_size /* reserved stack size */
.global _or1k_exception_stack_size
.global _or1k_exception_level

_or1k_stack_size: .word STACK_SIZE
_or1k_exception_stack_size: .word EXCEPTION_STACK_SIZE
Expand All @@ -95,13 +99,35 @@ _or1k_exception_stack_size: .word EXCEPTION_STACK_SIZE
#define GPR_BUF_OFFSET(x) (x << 2)

#ifndef __OR1K_MULTICORE__
#define CALL_EXCEPTION_HANDLER \
/* store current stack pointer to address 4 */ \
#define CALL_EXCEPTION_HANDLER(id) \
/* Store current stack pointer to address 4 */ \
l.sw 0x4(r0),r1; \
/* Load address of exception nesting level */ \
l.movhi r1,hi(_or1k_exception_level); \
l.ori r1,r1,lo(_or1k_exception_level); \
/* Load the current nesting level */ \
l.lwz r1,0(r1); \
/* Set flag if this is the outer (first) exception */ \
l.sfeq r1,r0; \
/* Branch to the code for nested exceptions */ \
OR1K_DELAYED_NOP( \
OR1K_INST(l.bnf .Lnested_##id) \
); \
/* Load top of the exception stack */ \
l.movhi r1,hi(_or1k_exception_stack_top); \
l.ori r1,r1,lo(_or1k_exception_stack_top); \
l.lwz r1,0(r1); \
OR1K_DELAYED( \
/* Load value from array to stack pointer */ \
OR1K_INST(l.lwz r1,0(r1)), \
/* and jump over the nested code */ \
OR1K_INST(l.j .Lnesting_done_##id) \
); \
.Lnested_##id: \
/* Load back the stack pointer */ \
l.lwz r1,0x4(r0)); \
/* Add redzone, nesting needs this */ \
l.addi r1,r1,-REDZONE; \
.Lnesting_done_##id: \
/* Reserve red zone and context space */ \
l.addi r1,r1,-EXCEPTION_STACK_FRAME; \
/* Store GPR3 in context */ \
Expand All @@ -112,6 +138,15 @@ _or1k_exception_stack_size: .word EXCEPTION_STACK_SIZE
l.sw GPR_BUF_OFFSET(1)(r1),r3; \
/* Store GPR4 in the context */ \
l.sw GPR_BUF_OFFSET(4)(r1),r4; \
/* Load address of the exception level */ \
l.movhi r3,hi(_or1k_exception_level); \
l.ori r3,r3,lo(_or1k_exception_level); \
/* Load current value */ \
l.lwz r4,0(r3); \
/* Increment level */ \
l.addi r4,r4,1; \
/* Store back */ \
l.sw 0(r3),r4; \
/* Copy the current program counter as first */ \
/* argument for the exception handler. This */ \
/* is then used to determine the exception. */ \
Expand All @@ -124,11 +159,36 @@ _or1k_exception_stack_size: .word EXCEPTION_STACK_SIZE
OR1K_INST(l.j _or1k_exception_handler) \
)
#else
#define CALL_EXCEPTION_HANDLER \
/* store current stack pointer to shadow reg */ \
#define CALL_EXCEPTION_HANDLER(id) \
/* Store current stack pointer to shadow reg */ \
l.mtspr r0,r1,SHADOW_REG(1); \
/* store current GPR3 as we need it */ \
/* Store current GPR3 for temporary use */ \
l.mtspr r0,r3,SHADOW_REG(2); \
/* Store current GPR2 for the level pointer */ \
l.mtspr r0,r4,SHADOW_REG(3); \
/* Load nesting level of exceptions */ \
l.movhi r4,hi(_or1k_exception_level); \
l.ori r4,r4,lo(_or1k_exception_level); \
/* Load array pointer */ \
l.lwz r4,0(r4); \
/* Get core id */ \
l.mfspr r3,r0,OR1K_SPR_SYS_COREID_ADDR; \
/* Generate offset */ \
l.slli r3,r3,2; \
/* Generate core nesting level address */ \
l.add r4,r4,r3; \
/* Load nesting level */ \
l.lwz r3,0(r4); \
/* Increment nesting level */ \
l.addi r3,r3,1; \
/* Write back nesting level */ \
l.sw 0(r4),r3; \
/* Set flag if this is the outer (first) exception */ \
l.sfeqi r3,1; \
/* Branch to the code for nested exceptions */ \
OR1K_DELAYED_NOP( \
OR1K_INST(l.bnf .Lnested_##id) \
); \
/* Load pointer to exception stack array */ \
l.movhi r1,hi(_or1k_exception_stack_core); \
l.ori r1,r1,lo(_or1k_exception_stack_core); \
Expand All @@ -137,10 +197,19 @@ _or1k_exception_stack_size: .word EXCEPTION_STACK_SIZE
l.mfspr r3,r0,OR1K_SPR_SYS_COREID_ADDR; \
/* Calculate offset in array */ \
l.slli r3,r3,2; \
/* Load value from array to stack pointer */ \
l.add r1,r1,r3; \
l.lwz r1,0(r1); \
/* Reserve red zone and context space */ \
OR1K_DELAYED( \
/* Load value from array to stack pointer */ \
OR1K_INST(l.lwz r1,0(r1)), \
/* and jump over nested exception pointer */ \
OR1K_INST(l.j .Lnesting_done_##id) \
); \
.Lnested_##id: \
/* The stack pointer is still active */ \
/* Add redzone, nesting needs this */ \
l.addi r1,r1,-REDZONE; \
.Lnesting_done_##id: \
/* Reserve context space */ \
l.addi r1,r1,-EXCEPTION_STACK_FRAME; \
/* Load back software's stack pointer */ \
l.mfspr r3,r0,SHADOW_REG(1); \
Expand All @@ -150,6 +219,8 @@ _or1k_exception_stack_size: .word EXCEPTION_STACK_SIZE
l.mfspr r3,r0,SHADOW_REG(2); \
/* Store this in the context */ \
l.sw GPR_BUF_OFFSET(3)(r1),r3; \
/* Load back GPR4 */ \
l.mfspr r4,r0,SHADOW_REG(3); \
/* Store GPR4 in the context */ \
l.sw GPR_BUF_OFFSET(4)(r1),r4; \
/* Copy the current program counter as first */ \
Expand Down Expand Up @@ -223,107 +294,107 @@ _or1k_reset:
OR1K_DELAYED_NOP(OR1K_INST(l.jr r4))

.org 0x200
CALL_EXCEPTION_HANDLER
CALL_EXCEPTION_HANDLER(2)

/* 0x300: Data Page Fault exception */
.org 0x300
CALL_EXCEPTION_HANDLER
CALL_EXCEPTION_HANDLER(3)

/* 0x400: Insn Page Fault exception */
.org 0x400
CALL_EXCEPTION_HANDLER
CALL_EXCEPTION_HANDLER(4)

/* 0x500: Timer exception */
.org 0x500
CALL_EXCEPTION_HANDLER
CALL_EXCEPTION_HANDLER(5)

/* 0x600: Aligment exception */
.org 0x600
CALL_EXCEPTION_HANDLER
CALL_EXCEPTION_HANDLER(6)

/* 0x700: Illegal insn exception */
.org 0x700
CALL_EXCEPTION_HANDLER
CALL_EXCEPTION_HANDLER(7)

/* 0x800: External interrupt exception */
.org 0x800
CALL_EXCEPTION_HANDLER
CALL_EXCEPTION_HANDLER(8)

/* 0x900: DTLB miss exception */
.org 0x900
CALL_EXCEPTION_HANDLER
CALL_EXCEPTION_HANDLER(9)

/* 0xa00: ITLB miss exception */
.org 0xa00
CALL_EXCEPTION_HANDLER
CALL_EXCEPTION_HANDLER(10)

/* 0xb00: Range exception */
.org 0xb00
CALL_EXCEPTION_HANDLER
CALL_EXCEPTION_HANDLER(11)

/* 0xc00: Syscall exception */
.org 0xc00
CALL_EXCEPTION_HANDLER
CALL_EXCEPTION_HANDLER(12)

/* 0xd00: Floating point exception */
.org 0xd00
CALL_EXCEPTION_HANDLER
CALL_EXCEPTION_HANDLER(13)

/* 0xe00: Trap exception */
.org 0xe00
CALL_EXCEPTION_HANDLER
CALL_EXCEPTION_HANDLER(14)

/* 0xf00: Reserved exceptions */
.org 0xf00
CALL_EXCEPTION_HANDLER
CALL_EXCEPTION_HANDLER(15)

.org 0x1000
CALL_EXCEPTION_HANDLER
CALL_EXCEPTION_HANDLER(16)

.org 0x1100
CALL_EXCEPTION_HANDLER
CALL_EXCEPTION_HANDLER(17)

.org 0x1200
CALL_EXCEPTION_HANDLER
CALL_EXCEPTION_HANDLER(18)

.org 0x1300
CALL_EXCEPTION_HANDLER
CALL_EXCEPTION_HANDLER(19)

.org 0x1400
CALL_EXCEPTION_HANDLER
CALL_EXCEPTION_HANDLER(20)

.org 0x1500
CALL_EXCEPTION_HANDLER
CALL_EXCEPTION_HANDLER(21)

.org 0x1600
CALL_EXCEPTION_HANDLER
CALL_EXCEPTION_HANDLER(22)

.org 0x1700
CALL_EXCEPTION_HANDLER
CALL_EXCEPTION_HANDLER(23)

.org 0x1800
CALL_EXCEPTION_HANDLER
CALL_EXCEPTION_HANDLER(24)

.org 0x1900
CALL_EXCEPTION_HANDLER
CALL_EXCEPTION_HANDLER(25)

.org 0x1a00
CALL_EXCEPTION_HANDLER
CALL_EXCEPTION_HANDLER(26)

.org 0x1b00
CALL_EXCEPTION_HANDLER
CALL_EXCEPTION_HANDLER(27)

.org 0x1c00
CALL_EXCEPTION_HANDLER
CALL_EXCEPTION_HANDLER(28)

.org 0x1d00
CALL_EXCEPTION_HANDLER
CALL_EXCEPTION_HANDLER(29)

.org 0x1e00
CALL_EXCEPTION_HANDLER
CALL_EXCEPTION_HANDLER(30)

.org 0x1f00
CALL_EXCEPTION_HANDLER
CALL_EXCEPTION_HANDLER(31)

/* Pad to the end */
.org 0x1ffc
Expand Down
19 changes: 19 additions & 0 deletions libgloss/or1k/exceptions-asm.S
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,7 @@
#define EXCEPTION_STACK_SIZE 136

.extern _or1k_exception_handler_table
.extern _or1k_exception_level

/* -------------------------------------------------------------------------- */
/*!Function to call appropriate exception handler
Expand Down Expand Up @@ -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
Expand Down
14 changes: 14 additions & 0 deletions libgloss/or1k/util.c
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Original file line number Diff line number Diff line change
Expand Up @@ -23,8 +23,13 @@
#include "or1k-internals.h"

#ifdef __OR1K_MULTICORE__
// Define pointers to arrays
uint32_t* *_or1k_stack_core;
uint32_t* *_or1k_exception_stack_core;
uint32_t* *_or1k_exception_level;
#else
// Define scalar
uint32_t _or1k_exception_level;
#endif

uint32_t* _or1k_stack_top;
Expand Down Expand Up @@ -68,6 +73,15 @@ void _or1k_init() {
#else
_or1k_exception_handler_table[6] = _or1k_interrupt_handler;
#endif

#ifdef __OR1K_MULTICORE__
_or1k_exception_level = _sbrk_r(0, 4 * or1k_numcores());
for (c = 0; c < or1k_numcores(); c++) {
_or1k_exception_level[c] = 0;
}
#else
_or1k_exception_level = 0;
#endif
}

uint32_t or1k_critical_begin() {
Expand Down

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