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Subject[RFC PATCH v1 24/41] powerpc/32: Replace ASM exception exit by C exception exit from ppc64
Date
This patch replaces the PPC32 ASM exceptio exit by C exception exit.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
arch/powerpc/kernel/entry_32.S | 466 +++++++++------------------------
1 file changed, 122 insertions(+), 344 deletions(-)

diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index bbce2de4c6a8..9a75ccb800e7 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -130,9 +130,7 @@ transfer_to_handler_cont:
stw r12,TI_LOCAL_FLAGS(r2)
lwz r9,_MSR(r11) /* if sleeping, clear MSR.EE */
rlwinm r9,r9,0,~MSR_EE
- lwz r12,_LINK(r11) /* and return to address in LR */
- kuap_restore r11, r2, r3, r4, r5
- lwz r2, GPR2(r11)
+ stw r9,_MSR(r11)
b fast_exception_return
#endif
_ASM_NOKPROBE_SYMBOL(transfer_to_handler)
@@ -334,69 +332,20 @@ END_FTR_SECTION_IFSET(CPU_FTR_SPE)

.globl fast_exception_return
fast_exception_return:
+ lwz r6,_MSR(r1)
+ andi. r0,r6,MSR_PR
+ bne .Lfast_user_interrupt_return
+ li r3,0 /* 0 return value, no EMULATE_STACK_STORE */
#if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
- andi. r10,r9,MSR_RI /* check for recoverable interrupt */
- beq 1f /* if not, we've got problems */
-#endif
-
-2: REST_4GPRS(3, r11)
- lwz r10,_CCR(r11)
- REST_GPR(1, r11)
- mtcr r10
- lwz r10,_LINK(r11)
- mtlr r10
- /* Clear the exception_marker on the stack to avoid confusing stacktrace */
- li r10, 0
- stw r10, 8(r11)
- REST_GPR(10, r11)
-#if defined(CONFIG_PPC_8xx) && defined(CONFIG_PERF_EVENTS)
- mtspr SPRN_NRI, r0
-#endif
- mtspr SPRN_SRR1,r9
- mtspr SPRN_SRR0,r12
- REST_GPR(9, r11)
- REST_GPR(12, r11)
- lwz r11,GPR11(r11)
- rfi
-#ifdef CONFIG_40x
- b . /* Prevent prefetch past rfi */
-#endif
-_ASM_NOKPROBE_SYMBOL(fast_exception_return)
-
-#if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
-/* check if the exception happened in a restartable section */
-1: lis r3,exc_exit_restart_end@ha
- addi r3,r3,exc_exit_restart_end@l
- cmplw r12,r3
- bge 3f
- lis r4,exc_exit_restart@ha
- addi r4,r4,exc_exit_restart@l
- cmplw r12,r4
- blt 3f
- lis r3,fee_restarts@ha
- tophys(r3,r3)
- lwz r5,fee_restarts@l(r3)
- addi r5,r5,1
- stw r5,fee_restarts@l(r3)
- mr r12,r4 /* restart at exc_exit_restart */
- b 2b
-
- .section .bss
- .align 2
-fee_restarts:
- .space 4
- .previous
-
-/* aargh, a nonrecoverable interrupt, panic */
-/* aargh, we don't know which trap this is */
-3:
- li r10,-1
- stw r10,_TRAP(r11)
+ andi. r0,r6,MSR_RI
+ bne+ .Lfast_kernel_interrupt_return
addi r3,r1,STACK_FRAME_OVERHEAD
- bl transfer_to_handler_full
bl unrecoverable_exception
- b ret_from_except
+ trap /* should not get here */
+#else
+ b .Lfast_kernel_interrupt_return
#endif
+_ASM_NOKPROBE_SYMBOL(fast_exception_return)

.globl ret_from_except_full
ret_from_except_full:
@@ -405,213 +354,141 @@ ret_from_except_full:

.globl ret_from_except
ret_from_except:
- /* Hard-disable interrupts so that current_thread_info()->flags
- * can't change between when we test it and when we return
- * from the interrupt. */
- /* Note: We don't bother telling lockdep about it */
- LOAD_REG_IMMEDIATE(r10,MSR_KERNEL)
- mtmsr r10 /* disable interrupts */
-
- lwz r3,_MSR(r1) /* Returning to user mode? */
- andi. r0,r3,MSR_PR
- beq resume_kernel
-
-user_exc_return: /* r10 contains MSR_KERNEL here */
- /* Check current_thread_info()->flags */
- lwz r9,TI_FLAGS(r2)
- andi. r0,r9,_TIF_USER_WORK_MASK
- bne do_work
-
-restore_user:
-#if defined(CONFIG_4xx) || defined(CONFIG_BOOKE)
- /* Check whether this process has its own DBCR0 value. The internal
- debug mode bit tells us that dbcr0 should be loaded. */
- lwz r0,THREAD+THREAD_DBCR0(r2)
- andis. r10,r0,DBCR0_IDM@h
- bnel- load_dbcr0
-#endif
- ACCOUNT_CPU_USER_EXIT(r2, r10, r11)
+_ASM_NOKPROBE_SYMBOL(ret_from_except)
+
+ .globl interrupt_return
+interrupt_return:
+ lwz r4,_MSR(r1)
+ andi. r0,r4,MSR_PR
+ beq .Lkernel_interrupt_return
+ addi r3,r1,STACK_FRAME_OVERHEAD
+ bl interrupt_exit_user_prepare
+ cmpwi r3,0
+ bne- .Lrestore_nvgprs
+
+.Lfast_user_interrupt_return:
#ifdef CONFIG_PPC_BOOK3S_32
kuep_unlock r10, r11
#endif
+ kuap_check r2, r4
+ lwz r11,_NIP(r1)
+ lwz r12,_MSR(r1)
+ mtspr SPRN_SRR0,r11
+ mtspr SPRN_SRR1,r12

- b restore
-
-/* N.B. the only way to get here is from the beq following ret_from_except. */
-resume_kernel:
- /* check current_thread_info, _TIF_EMULATE_STACK_STORE */
- lwz r8,TI_FLAGS(r2)
- andis. r0,r8,_TIF_EMULATE_STACK_STORE@h
- beq+ 1f
+BEGIN_FTR_SECTION
+ stwcx. r0,0,r1 /* to clear the reservation */
+FTR_SECTION_ELSE
+ lwarx r0,0,r1
+ALT_FTR_SECTION_END_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS)

- addi r8,r1,INT_FRAME_SIZE /* Get the kprobed function entry */
+ lwz r3,_CCR(r1)
+ lwz r4,_LINK(r1)
+ lwz r5,_CTR(r1)
+ lwz r6,_XER(r1)
+ li r0,0

- lwz r3,GPR1(r1)
- subi r3,r3,INT_FRAME_SIZE /* dst: Allocate a trampoline exception frame */
- mr r4,r1 /* src: current exception frame */
- mr r1,r3 /* Reroute the trampoline frame to r1 */
+ REST_4GPRS(7, r1)
+ REST_2GPRS(11, r1)

- /* Copy from the original to the trampoline. */
- li r5,INT_FRAME_SIZE/4 /* size: INT_FRAME_SIZE */
- li r6,0 /* start offset: 0 */
+ mtcr r3
+ mtlr r4
mtctr r5
-2: lwzx r0,r6,r4
- stwx r0,r6,r3
- addi r6,r6,4
- bdnz 2b
-
- /* Do real store operation to complete stwu */
- lwz r5,GPR1(r1)
- stw r8,0(r5)
-
- /* Clear _TIF_EMULATE_STACK_STORE flag */
- lis r11,_TIF_EMULATE_STACK_STORE@h
- addi r5,r2,TI_FLAGS
-0: lwarx r8,0,r5
- andc r8,r8,r11
- stwcx. r8,0,r5
- bne- 0b
-1:
+ mtspr SPRN_XER,r6

-#ifdef CONFIG_PREEMPTION
- /* check current_thread_info->preempt_count */
- lwz r0,TI_PREEMPT(r2)
- cmpwi 0,r0,0 /* if non-zero, just restore regs and return */
- bne restore_kuap
- andi. r8,r8,_TIF_NEED_RESCHED
- beq+ restore_kuap
- lwz r3,_MSR(r1)
- andi. r0,r3,MSR_EE /* interrupts off? */
- beq restore_kuap /* don't schedule if so */
-#ifdef CONFIG_TRACE_IRQFLAGS
- /* Lockdep thinks irqs are enabled, we need to call
- * preempt_schedule_irq with IRQs off, so we inform lockdep
- * now that we -did- turn them off already
- */
- bl trace_hardirqs_off
-#endif
- bl preempt_schedule_irq
-#ifdef CONFIG_TRACE_IRQFLAGS
- /* And now, to properly rebalance the above, we tell lockdep they
- * are being turned back on, which will happen when we return
- */
- bl trace_hardirqs_on
+ REST_4GPRS(2, r1)
+ REST_GPR(6, r1)
+ REST_GPR(0, r1)
+ REST_GPR(1, r1)
+ rfi
+#ifdef CONFIG_40x
+ b . /* Prevent prefetch past rfi */
#endif
-#endif /* CONFIG_PREEMPTION */
-restore_kuap:
- kuap_restore r1, r2, r9, r10, r0

- /* interrupts are hard-disabled at this point */
-restore:
-#if defined(CONFIG_44x) && !defined(CONFIG_PPC_47x)
- lis r4,icache_44x_need_flush@ha
- lwz r5,icache_44x_need_flush@l(r4)
- cmplwi cr0,r5,0
- beq+ 1f
- li r6,0
- iccci r0,r0
- stw r6,icache_44x_need_flush@l(r4)
-1:
-#endif /* CONFIG_44x */
-
- lwz r9,_MSR(r1)
-#ifdef CONFIG_TRACE_IRQFLAGS
- /* Lockdep doesn't know about the fact that IRQs are temporarily turned
- * off in this assembly code while peeking at TI_FLAGS() and such. However
- * we need to inform it if the exception turned interrupts off, and we
- * are about to trun them back on.
- */
- andi. r10,r9,MSR_EE
- beq 1f
- stwu r1,-32(r1)
- mflr r0
- stw r0,4(r1)
- bl trace_hardirqs_on
- addi r1, r1, 32
- lwz r9,_MSR(r1)
-1:
-#endif /* CONFIG_TRACE_IRQFLAGS */
+.Lrestore_nvgprs:
+ REST_NVGPRS(r1)
+ b .Lfast_user_interrupt_return

- lwz r0,GPR0(r1)
- lwz r2,GPR2(r1)
- REST_4GPRS(3, r1)
- REST_2GPRS(7, r1)
+.Lkernel_interrupt_return:
+ addi r3,r1,STACK_FRAME_OVERHEAD
+ bl interrupt_exit_kernel_prepare

- lwz r10,_XER(r1)
- lwz r11,_CTR(r1)
- mtspr SPRN_XER,r10
- mtctr r11
+.Lfast_kernel_interrupt_return:
+ cmpwi cr1,r3,0
+ kuap_restore r1, r2, r3, r4, r5
+ lwz r11,_NIP(r1)
+ lwz r12,_MSR(r1)
+ mtspr SPRN_SRR0,r11
+ mtspr SPRN_SRR1,r12

BEGIN_FTR_SECTION
- lwarx r11,0,r1
-END_FTR_SECTION_IFSET(CPU_FTR_NEED_PAIRED_STWCX)
- stwcx. r0,0,r1 /* to clear the reservation */
+ stwcx. r0,0,r1 /* to clear the reservation */
+FTR_SECTION_ELSE
+ lwarx r0,0,r1
+ALT_FTR_SECTION_END_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS)

-#if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
- andi. r10,r9,MSR_RI /* check if this exception occurred */
- beql nonrecoverable /* at a bad place (MSR:RI = 0) */
+ lwz r3,_LINK(r1)
+ lwz r4,_CTR(r1)
+ lwz r5,_XER(r1)
+ lwz r6,_CCR(r1)
+ li r0,0

- lwz r10,_CCR(r1)
- lwz r11,_LINK(r1)
- mtcrf 0xFF,r10
- mtlr r11
+ REST_4GPRS(7, r1)
+ REST_2GPRS(11, r1)
+
+ mtlr r3
+ mtctr r4
+ mtspr SPRN_XER,r5

- /* Clear the exception_marker on the stack to avoid confusing stacktrace */
- li r10, 0
- stw r10, 8(r1)
/*
- * Once we put values in SRR0 and SRR1, we are in a state
- * where exceptions are not recoverable, since taking an
- * exception will trash SRR0 and SRR1. Therefore we clear the
- * MSR:RI bit to indicate this. If we do take an exception,
- * we can't return to the point of the exception but we
- * can restart the exception exit path at the label
- * exc_exit_restart below. -- paulus
+ * Leaving a stale exception_marker on the stack can confuse
+ * the reliable stack unwinder later on. Clear it.
*/
- LOAD_REG_IMMEDIATE(r10,MSR_KERNEL & ~MSR_RI)
- mtmsr r10 /* clear the RI bit */
- .globl exc_exit_restart
-exc_exit_restart:
- lwz r12,_NIP(r1)
- mtspr SPRN_SRR0,r12
- mtspr SPRN_SRR1,r9
- REST_4GPRS(9, r1)
- lwz r1,GPR1(r1)
- .globl exc_exit_restart_end
-exc_exit_restart_end:
+ stw r0,8(r1)
+
+ REST_4GPRS(2, r1)
+
+ bne- cr1,1f /* emulate stack store */
+ mtcr r6
+ REST_GPR(6, r1)
+ REST_GPR(0, r1)
+ REST_GPR(1, r1)
rfi
-_ASM_NOKPROBE_SYMBOL(exc_exit_restart)
-_ASM_NOKPROBE_SYMBOL(exc_exit_restart_end)
+#ifdef CONFIG_40x
+ b . /* Prevent prefetch past rfi */
+#endif

-#else /* !(CONFIG_4xx || CONFIG_BOOKE) */
- /*
- * This is a bit different on 4xx/Book-E because it doesn't have
- * the RI bit in the MSR.
- * The TLB miss handler checks if we have interrupted
- * the exception exit path and restarts it if so
- * (well maybe one day it will... :).
+1: /*
+ * Emulate stack store with update. New r1 value was already calculated
+ * and updated in our interrupt regs by emulate_loadstore, but we can't
+ * store the previous value of r1 to the stack before re-loading our
+ * registers from it, otherwise they could be clobbered. Use
+ * SPRG Scratch0 in thread struct as temporary storage to hold the store
+ * data, as interrupts are disabled here so it won't be clobbered.
*/
- lwz r11,_LINK(r1)
- mtlr r11
- lwz r10,_CCR(r1)
- mtcrf 0xff,r10
- /* Clear the exception_marker on the stack to avoid confusing stacktrace */
- li r10, 0
- stw r10, 8(r1)
- REST_2GPRS(9, r1)
- .globl exc_exit_restart
-exc_exit_restart:
- lwz r11,_NIP(r1)
- lwz r12,_MSR(r1)
- mtspr SPRN_SRR0,r11
- mtspr SPRN_SRR1,r12
- REST_2GPRS(11, r1)
- lwz r1,GPR1(r1)
- .globl exc_exit_restart_end
-exc_exit_restart_end:
+ mtcr r6
+#ifdef CONFIG_BOOKE
+ mtspr SPRN_SPRG_WSCRATCH0, r9
+#else
+ mtspr SPRN_SPRG_SCRATCH0, r9
+#endif
+ addi r9,r1,INT_FRAME_SIZE /* get original r1 */
+ REST_GPR(6, r1)
+ REST_GPR(0, r1)
+ REST_GPR(1, r1)
+ stw r9,0(r1) /* perform store component of stdu */
+#ifdef CONFIG_BOOKE
+ mtspr r9, SPRN_SPRG_RSCRATCH0
+#else
+ mfspr r9, SPRN_SPRG_SCRATCH0
+#endif
rfi
- b . /* prevent prefetch past rfi */
-_ASM_NOKPROBE_SYMBOL(exc_exit_restart)
+#ifdef CONFIG_40x
+ b . /* Prevent prefetch past rfi */
+#endif
+_ASM_NOKPROBE_SYMBOL(interrupt_return)
+
+#if defined(CONFIG_4xx) || defined(CONFIG_BOOKE)

/*
* Returning from a critical interrupt in user mode doesn't need
@@ -747,30 +624,6 @@ ret_from_mcheck_exc:
_ASM_NOKPROBE_SYMBOL(ret_from_mcheck_exc)
#endif /* CONFIG_BOOKE */

-/*
- * Load the DBCR0 value for a task that is being ptraced,
- * having first saved away the global DBCR0. Note that r0
- * has the dbcr0 value to set upon entry to this.
- */
-load_dbcr0:
- mfmsr r10 /* first disable debug exceptions */
- rlwinm r10,r10,0,~MSR_DE
- mtmsr r10
- isync
- mfspr r10,SPRN_DBCR0
- lis r11,global_dbcr0@ha
- addi r11,r11,global_dbcr0@l
-#ifdef CONFIG_SMP
- lwz r9,TASK_CPU(r2)
- slwi r9,r9,2
- add r11,r11,r9
-#endif
- stw r10,0(r11)
- mtspr SPRN_DBCR0,r0
- li r11,-1
- mtspr SPRN_DBSR,r11 /* clear all pending debug events */
- blr
-
.section .bss
.align 4
.global global_dbcr0
@@ -779,81 +632,6 @@ global_dbcr0:
.previous
#endif /* !(CONFIG_4xx || CONFIG_BOOKE) */

-do_work: /* r10 contains MSR_KERNEL here */
- andi. r0,r9,_TIF_NEED_RESCHED
- beq do_user_signal
-
-do_resched: /* r10 contains MSR_KERNEL here */
-#ifdef CONFIG_TRACE_IRQFLAGS
- bl trace_hardirqs_on
- mfmsr r10
-#endif
- ori r10,r10,MSR_EE
- mtmsr r10 /* hard-enable interrupts */
- bl schedule
-recheck:
- /* Note: And we don't tell it we are disabling them again
- * neither. Those disable/enable cycles used to peek at
- * TI_FLAGS aren't advertised.
- */
- LOAD_REG_IMMEDIATE(r10,MSR_KERNEL)
- mtmsr r10 /* disable interrupts */
- lwz r9,TI_FLAGS(r2)
- andi. r0,r9,_TIF_NEED_RESCHED
- bne- do_resched
- andi. r0,r9,_TIF_USER_WORK_MASK
- beq restore_user
-do_user_signal: /* r10 contains MSR_KERNEL here */
- ori r10,r10,MSR_EE
- mtmsr r10 /* hard-enable interrupts */
-2: addi r3,r1,STACK_FRAME_OVERHEAD
- mr r4,r9
- bl do_notify_resume
- REST_NVGPRS(r1)
- b recheck
-
-/*
- * We come here when we are at the end of handling an exception
- * that occurred at a place where taking an exception will lose
- * state information, such as the contents of SRR0 and SRR1.
- */
-nonrecoverable:
- lis r10,exc_exit_restart_end@ha
- addi r10,r10,exc_exit_restart_end@l
- cmplw r12,r10
- bge 3f
- lis r11,exc_exit_restart@ha
- addi r11,r11,exc_exit_restart@l
- cmplw r12,r11
- blt 3f
- lis r10,ee_restarts@ha
- lwz r12,ee_restarts@l(r10)
- addi r12,r12,1
- stw r12,ee_restarts@l(r10)
- mr r12,r11 /* restart at exc_exit_restart */
- blr
-3: /* OK, we can't recover, kill this process */
- lwz r3,_TRAP(r1)
- andi. r0,r3,1
- beq 5f
- SAVE_NVGPRS(r1)
- rlwinm r3,r3,0,0,30
- stw r3,_TRAP(r1)
-5: mfspr r2,SPRN_SPRG_THREAD
- addi r2,r2,-THREAD
- tovirt(r2,r2) /* set back r2 to current */
-4: addi r3,r1,STACK_FRAME_OVERHEAD
- bl unrecoverable_exception
- /* shouldn't return */
- b 4b
-_ASM_NOKPROBE_SYMBOL(nonrecoverable)
-
- .section .bss
- .align 2
-ee_restarts:
- .space 4
- .previous
-
/*
* PROM code for specific machines follows. Put it
* here so it's easy to add arch-specific sections later.
--
2.25.0
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