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openrisc: use shadow registers to save regs on exception
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Previously, the area between 0x0-0x100 have been used as a "scratch"
memory area to temporarily store regs during exception entry. In a
multi-core environment, this will not work.

This change is to use shadow registers for nested context.

Currently only the "critical" temp load/stores are covered, the
EMERGENCY_PRINT ones are left as is (when they are used, it's game over
anyway), they need to be handled as well in the future.

Signed-off-by: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
Signed-off-by: Stafford Horne <shorne@gmail.com>
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Stefan Kristiansson authored and Stafford Horne committed Nov 3, 2017
1 parent ddc92be commit 91993c8
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Showing 2 changed files with 80 additions and 26 deletions.
11 changes: 11 additions & 0 deletions arch/openrisc/Kconfig
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Original file line number Diff line number Diff line change
Expand Up @@ -124,6 +124,17 @@ config OPENRISC_NO_SPR_SR_DSX
Say N here if you know that your OpenRISC processor has
SPR_SR_DSX bit implemented. Say Y if you are unsure.

config OPENRISC_HAVE_SHADOW_GPRS
bool "Support for shadow gpr files" if !SMP
default y if SMP
help
Say Y here if your OpenRISC processor features shadowed
register files. They will in such case be used as a
scratch reg storage on exception entry.

On SMP systems, this feature is mandatory.
On a unicore system it's safe to say N here if you are unsure.

config CMDLINE
string "Default kernel command string"
default ""
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95 changes: 69 additions & 26 deletions arch/openrisc/kernel/head.S
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Original file line number Diff line number Diff line change
Expand Up @@ -49,9 +49,31 @@

/* ============================================[ tmp store locations ]=== */

#define SPR_SHADOW_GPR(x) ((x) + SPR_GPR_BASE + 32)

/*
* emergency_print temporary stores
*/
#ifdef CONFIG_OPENRISC_HAVE_SHADOW_GPRS
#define EMERGENCY_PRINT_STORE_GPR4 l.mtspr r0,r4,SPR_SHADOW_GPR(14)
#define EMERGENCY_PRINT_LOAD_GPR4 l.mfspr r4,r0,SPR_SHADOW_GPR(14)

#define EMERGENCY_PRINT_STORE_GPR5 l.mtspr r0,r5,SPR_SHADOW_GPR(15)
#define EMERGENCY_PRINT_LOAD_GPR5 l.mfspr r5,r0,SPR_SHADOW_GPR(15)

#define EMERGENCY_PRINT_STORE_GPR6 l.mtspr r0,r6,SPR_SHADOW_GPR(16)
#define EMERGENCY_PRINT_LOAD_GPR6 l.mfspr r6,r0,SPR_SHADOW_GPR(16)

#define EMERGENCY_PRINT_STORE_GPR7 l.mtspr r0,r7,SPR_SHADOW_GPR(7)
#define EMERGENCY_PRINT_LOAD_GPR7 l.mfspr r7,r0,SPR_SHADOW_GPR(7)

#define EMERGENCY_PRINT_STORE_GPR8 l.mtspr r0,r8,SPR_SHADOW_GPR(8)
#define EMERGENCY_PRINT_LOAD_GPR8 l.mfspr r8,r0,SPR_SHADOW_GPR(8)

#define EMERGENCY_PRINT_STORE_GPR9 l.mtspr r0,r9,SPR_SHADOW_GPR(9)
#define EMERGENCY_PRINT_LOAD_GPR9 l.mfspr r9,r0,SPR_SHADOW_GPR(9)

#else /* !CONFIG_OPENRISC_HAVE_SHADOW_GPRS */
#define EMERGENCY_PRINT_STORE_GPR4 l.sw 0x20(r0),r4
#define EMERGENCY_PRINT_LOAD_GPR4 l.lwz r4,0x20(r0)

Expand All @@ -70,13 +92,28 @@
#define EMERGENCY_PRINT_STORE_GPR9 l.sw 0x34(r0),r9
#define EMERGENCY_PRINT_LOAD_GPR9 l.lwz r9,0x34(r0)

#endif

/*
* TLB miss handlers temorary stores
*/
#define EXCEPTION_STORE_GPR9 l.sw 0x10(r0),r9
#define EXCEPTION_LOAD_GPR9 l.lwz r9,0x10(r0)
#ifdef CONFIG_OPENRISC_HAVE_SHADOW_GPRS
#define EXCEPTION_STORE_GPR2 l.mtspr r0,r2,SPR_SHADOW_GPR(2)
#define EXCEPTION_LOAD_GPR2 l.mfspr r2,r0,SPR_SHADOW_GPR(2)

#define EXCEPTION_STORE_GPR3 l.mtspr r0,r3,SPR_SHADOW_GPR(3)
#define EXCEPTION_LOAD_GPR3 l.mfspr r3,r0,SPR_SHADOW_GPR(3)

#define EXCEPTION_STORE_GPR4 l.mtspr r0,r4,SPR_SHADOW_GPR(4)
#define EXCEPTION_LOAD_GPR4 l.mfspr r4,r0,SPR_SHADOW_GPR(4)

#define EXCEPTION_STORE_GPR5 l.mtspr r0,r5,SPR_SHADOW_GPR(5)
#define EXCEPTION_LOAD_GPR5 l.mfspr r5,r0,SPR_SHADOW_GPR(5)

#define EXCEPTION_STORE_GPR6 l.mtspr r0,r6,SPR_SHADOW_GPR(6)
#define EXCEPTION_LOAD_GPR6 l.mfspr r6,r0,SPR_SHADOW_GPR(6)

#else /* !CONFIG_OPENRISC_HAVE_SHADOW_GPRS */
#define EXCEPTION_STORE_GPR2 l.sw 0x64(r0),r2
#define EXCEPTION_LOAD_GPR2 l.lwz r2,0x64(r0)

Expand All @@ -92,26 +129,32 @@
#define EXCEPTION_STORE_GPR6 l.sw 0x74(r0),r6
#define EXCEPTION_LOAD_GPR6 l.lwz r6,0x74(r0)

#endif

/*
* EXCEPTION_HANDLE temporary stores
*/

#ifdef CONFIG_OPENRISC_HAVE_SHADOW_GPRS
#define EXCEPTION_T_STORE_GPR30 l.mtspr r0,r30,SPR_SHADOW_GPR(30)
#define EXCEPTION_T_LOAD_GPR30(reg) l.mfspr reg,r0,SPR_SHADOW_GPR(30)

#define EXCEPTION_T_STORE_GPR10 l.mtspr r0,r10,SPR_SHADOW_GPR(10)
#define EXCEPTION_T_LOAD_GPR10(reg) l.mfspr reg,r0,SPR_SHADOW_GPR(10)

#define EXCEPTION_T_STORE_SP l.mtspr r0,r1,SPR_SHADOW_GPR(1)
#define EXCEPTION_T_LOAD_SP(reg) l.mfspr reg,r0,SPR_SHADOW_GPR(1)

#else /* !CONFIG_OPENRISC_HAVE_SHADOW_GPRS */
#define EXCEPTION_T_STORE_GPR30 l.sw 0x78(r0),r30
#define EXCEPTION_T_LOAD_GPR30(reg) l.lwz reg,0x78(r0)

#define EXCEPTION_T_STORE_GPR10 l.sw 0x7c(r0),r10
#define EXCEPTION_T_LOAD_GPR10(reg) l.lwz reg,0x7c(r0)

#define EXCEPTION_T_STORE_SP l.sw 0x80(r0),r1
#define EXCEPTION_T_STORE_SP l.sw 0x80(r0),r1
#define EXCEPTION_T_LOAD_SP(reg) l.lwz reg,0x80(r0)

/*
* For UNHANLDED_EXCEPTION
*/

#define EXCEPTION_T_STORE_GPR31 l.sw 0x84(r0),r31
#define EXCEPTION_T_LOAD_GPR31(reg) l.lwz reg,0x84(r0)
#endif

/* =========================================================[ macros ]=== */

Expand Down Expand Up @@ -226,7 +269,7 @@
*
*/
#define UNHANDLED_EXCEPTION(handler) \
EXCEPTION_T_STORE_GPR31 ;\
EXCEPTION_T_STORE_GPR30 ;\
EXCEPTION_T_STORE_GPR10 ;\
EXCEPTION_T_STORE_SP ;\
/* temporary store r3, r9 into r1, r10 */ ;\
Expand Down Expand Up @@ -255,35 +298,35 @@
/* r1: KSP, r10: current, r31: __pa(KSP) */ ;\
/* r12: temp, syscall indicator, r13 temp */ ;\
l.addi r1,r1,-(INT_FRAME_SIZE) ;\
/* r1 is KSP, r31 is __pa(KSP) */ ;\
tophys (r31,r1) ;\
l.sw PT_GPR12(r31),r12 ;\
/* r1 is KSP, r30 is __pa(KSP) */ ;\
tophys (r30,r1) ;\
l.sw PT_GPR12(r30),r12 ;\
l.mfspr r12,r0,SPR_EPCR_BASE ;\
l.sw PT_PC(r31),r12 ;\
l.sw PT_PC(r30),r12 ;\
l.mfspr r12,r0,SPR_ESR_BASE ;\
l.sw PT_SR(r31),r12 ;\
l.sw PT_SR(r30),r12 ;\
/* save r31 */ ;\
EXCEPTION_T_LOAD_GPR31(r12) ;\
l.sw PT_GPR31(r31),r12 ;\
EXCEPTION_T_LOAD_GPR30(r12) ;\
l.sw PT_GPR30(r30),r12 ;\
/* save r10 as was prior to exception */ ;\
EXCEPTION_T_LOAD_GPR10(r12) ;\
l.sw PT_GPR10(r31),r12 ;\
l.sw PT_GPR10(r30),r12 ;\
/* save PT_SP as was prior to exception */ ;\
EXCEPTION_T_LOAD_SP(r12) ;\
l.sw PT_SP(r31),r12 ;\
l.sw PT_GPR13(r31),r13 ;\
l.sw PT_SP(r30),r12 ;\
l.sw PT_GPR13(r30),r13 ;\
/* --> */ ;\
/* save exception r4, set r4 = EA */ ;\
l.sw PT_GPR4(r31),r4 ;\
l.sw PT_GPR4(r30),r4 ;\
l.mfspr r4,r0,SPR_EEAR_BASE ;\
/* r12 == 1 if we come from syscall */ ;\
CLEAR_GPR(r12) ;\
/* ----- play a MMU trick ----- */ ;\
l.ori r31,r0,(EXCEPTION_SR) ;\
l.mtspr r0,r31,SPR_ESR_BASE ;\
l.ori r30,r0,(EXCEPTION_SR) ;\
l.mtspr r0,r30,SPR_ESR_BASE ;\
/* r31: EA address of handler */ ;\
LOAD_SYMBOL_2_GPR(r31,handler) ;\
l.mtspr r0,r31,SPR_EPCR_BASE ;\
LOAD_SYMBOL_2_GPR(r30,handler) ;\
l.mtspr r0,r30,SPR_EPCR_BASE ;\
l.rfe

/* =====================================================[ exceptions] === */
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