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powerpc/32: implement fast entry for syscalls on non BOOKE 

This patch implements a fast entry for syscalls.

Syscalls don't have to preserve non volatile registers except LR.

This patch then implement a fast entry for syscalls, where
volatile registers get clobbered.

As this entry is dedicated to syscall it always sets MSR_EE
and warns in case MSR_EE was previously off

It also assumes that the call is always from user, system calls are
unexpected from kernel.

The overall series improves null_syscall selftest by 12,5% on an 83xx
and by 17% on a 8xx.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Christophe Leroy 2019-04-30 12:39:02 +00:00 committed by Michael Ellerman
parent 40530db7c6
commit b86fb88855
5 changed files with 116 additions and 10 deletions
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32
arch/powerpc/kernel/entry_32.S
View File

@ -342,6 +342,35 @@ stack_ovf:
SYNC
RFI
#ifndef CONFIG_BOOKE /* to be removed once BOOKE uses fast syscall entry */
#ifdef CONFIG_TRACE_IRQFLAGS
trace_syscall_entry_irq_off:
/*
* Syscall shouldn't happen while interrupts are disabled,
* so let's do a warning here.
*/
0: trap
EMIT_BUG_ENTRY 0b,__FILE__,__LINE__, BUGFLAG_WARNING
bl trace_hardirqs_on
/* Now enable for real */
LOAD_MSR_KERNEL(r10, MSR_KERNEL | MSR_EE)
mtmsr r10
REST_GPR(0, r1)
REST_4GPRS(3, r1)
REST_2GPRS(7, r1)
b DoSyscall
#endif /* CONFIG_TRACE_IRQFLAGS */
.globl transfer_to_syscall
transfer_to_syscall:
#ifdef CONFIG_TRACE_IRQFLAGS
andi. r12,r9,MSR_EE
beq- trace_syscall_entry_irq_off
#endif /* CONFIG_TRACE_IRQFLAGS */
#endif /* !CONFIG_BOOKE */
/*
* Handle a system call.
*/
@ -353,9 +382,11 @@ _GLOBAL(DoSyscall)
stw r3,ORIG_GPR3(r1)
li r12,0
stw r12,RESULT(r1)
#ifdef CONFIG_BOOKE /* to be removed once BOOKE uses fast syscall entry */
lwz r11,_CCR(r1) /* Clear SO bit in CR */
rlwinm r11,r11,0,4,2
stw r11,_CCR(r1)
#endif
#ifdef CONFIG_TRACE_IRQFLAGS
/* Make sure interrupts are enabled */
mfmsr r11
@ -1219,6 +1250,7 @@ load_dbcr0:
.section .bss
.align 4
.global global_dbcr0
global_dbcr0:
.space 8*NR_CPUS
.previous

3
arch/powerpc/kernel/head_32.S
View File

@ -374,8 +374,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_FPU_UNAVAILABLE)
. = 0xc00
DO_KVM 0xc00
SystemCall:
EXCEPTION_PROLOG
EXC_XFER_SYS(0xc00, DoSyscall)
SYSCALL_ENTRY 0xc00
/* Single step - not used on 601 */
EXCEPTION(0xd00, SingleStep, single_step_exception, EXC_XFER_STD)

85
arch/powerpc/kernel/head_32.h
View File

@ -73,6 +73,87 @@
SAVE_2GPRS(7, r11)
.endm
.macro SYSCALL_ENTRY trapno
mfspr r12,SPRN_SPRG_THREAD
mfcr r10
lwz r11,TASK_STACK-THREAD(r12)
mflr r9
addi r11,r11,THREAD_SIZE - INT_FRAME_SIZE
rlwinm r10,r10,0,4,2 /* Clear SO bit in CR */
tophys(r11,r11)
stw r10,_CCR(r11) /* save registers */
mfspr r10,SPRN_SRR0
stw r9,_LINK(r11)
mfspr r9,SPRN_SRR1
stw r1,GPR1(r11)
stw r1,0(r11)
tovirt(r1,r11) /* set new kernel sp */
stw r10,_NIP(r11)
#ifdef CONFIG_40x
rlwinm r9,r9,0,14,12 /* clear MSR_WE (necessary?) */
#else
LOAD_MSR_KERNEL(r10, MSR_KERNEL & ~(MSR_IR|MSR_DR)) /* can take exceptions */
MTMSRD(r10) /* (except for mach check in rtas) */
#endif
lis r10,STACK_FRAME_REGS_MARKER@ha /* exception frame marker */
stw r2,GPR2(r11)
addi r10,r10,STACK_FRAME_REGS_MARKER@l
stw r9,_MSR(r11)
li r2, \trapno + 1
stw r10,8(r11)
stw r2,_TRAP(r11)
SAVE_GPR(0, r11)
SAVE_4GPRS(3, r11)
SAVE_2GPRS(7, r11)
addi r11,r1,STACK_FRAME_OVERHEAD
addi r2,r12,-THREAD
stw r11,PT_REGS(r12)
#if defined(CONFIG_40x)
/* Check to see if the dbcr0 register is set up to debug. Use the
internal debug mode bit to do this. */
lwz r12,THREAD_DBCR0(r12)
andis. r12,r12,DBCR0_IDM@h
#endif
ACCOUNT_CPU_USER_ENTRY(r2, r11, r12)
#if defined(CONFIG_40x)
beq+ 3f
/* From user and task is ptraced - load up global dbcr0 */
li r12,-1 /* clear all pending debug events */
mtspr SPRN_DBSR,r12
lis r11,global_dbcr0@ha
tophys(r11,r11)
addi r11,r11,global_dbcr0@l
lwz r12,0(r11)
mtspr SPRN_DBCR0,r12
lwz r12,4(r11)
addi r12,r12,-1
stw r12,4(r11)
#endif
3:
tovirt(r2, r2) /* set r2 to current */
lis r11, transfer_to_syscall@h
ori r11, r11, transfer_to_syscall@l
#ifdef CONFIG_TRACE_IRQFLAGS
/*
* If MSR is changing we need to keep interrupts disabled at this point
* otherwise we might risk taking an interrupt before we tell lockdep
* they are enabled.
*/
LOAD_MSR_KERNEL(r10, MSR_KERNEL)
rlwimi r10, r9, 0, MSR_EE
#else
LOAD_MSR_KERNEL(r10, MSR_KERNEL | MSR_EE)
#endif
#if defined(CONFIG_PPC_8xx) && defined(CONFIG_PERF_EVENTS)
mtspr SPRN_NRI, r0
#endif
mtspr SPRN_SRR1,r10
mtspr SPRN_SRR0,r11
SYNC
RFI /* jump to handler, enable MMU */
.endm
/*
* Note: code which follows this uses cr0.eq (set if from kernel),
* r11, r12 (SRR0), and r9 (SRR1).
@ -119,8 +200,4 @@ label:
EXC_XFER_TEMPLATE(hdlr, n+1, MSR_KERNEL, transfer_to_handler, \
ret_from_except)
#define EXC_XFER_SYS(n, hdlr) \
EXC_XFER_TEMPLATE(hdlr, n+1, MSR_KERNEL | MSR_EE, transfer_to_handler, \
ret_from_except)
#endif /* __HEAD_32_H__ */

3
arch/powerpc/kernel/head_40x.S
View File

@ -348,8 +348,7 @@ _ENTRY(saved_ksp_limit)
/* 0x0C00 - System Call Exception */
START_EXCEPTION(0x0C00, SystemCall)
EXCEPTION_PROLOG
EXC_XFER_SYS(0xc00, DoSyscall)
SYSCALL_ENTRY 0xc00
EXCEPTION(0x0D00, Trap_0D, unknown_exception, EXC_XFER_STD)
EXCEPTION(0x0E00, Trap_0E, unknown_exception, EXC_XFER_STD)

3
arch/powerpc/kernel/head_8xx.S
View File

@ -185,8 +185,7 @@ Alignment:
/* System call */
. = 0xc00
SystemCall:
EXCEPTION_PROLOG
EXC_XFER_SYS(0xc00, DoSyscall)
SYSCALL_ENTRY 0xc00
/* Single step - not used on 601 */
EXCEPTION(0xd00, SingleStep, single_step_exception, EXC_XFER_STD)