[PATCH v5 15/22] powerpc/32: Remove verification of MSR_PR on syscall in the ASM entry

Christophe Leroy
2021-02-08T16:38:06Z

system_call_exception() checks MSR_PR and BUGs if a syscall
is issued from kernel mode.

No need to handle it anymore from the ASM entry code.

null_syscall reduction 2 cycles (348 => 346 cycles)

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
arch/powerpc/kernel/entry_32.S | 30 ------------------------------
arch/powerpc/kernel/head_32.h | 3 ---
arch/powerpc/kernel/head_booke.h | 3 ---
3 files changed, 36 deletions(-)

diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index bbf7ecea6fe0..cffe58e63356 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -421,36 +421,6 @@ ret_from_kernel_thread:
li r3,0
b ret_from_syscall

- /*
- * System call was called from kernel. We get here with SRR1 in r9.
- * Mark the exception as recoverable once we have retrieved SRR0,
- * trap a warning and return ENOSYS with CR[SO] set.
- */
- .globl ret_from_kernel_syscall
-ret_from_kernel_syscall:
- mfspr r9, SPRN_SRR0
- mfspr r10, SPRN_SRR1
-#if !defined(CONFIG_4xx) && !defined(CONFIG_BOOKE)
- LOAD_REG_IMMEDIATE(r11, MSR_KERNEL & ~(MSR_IR|MSR_DR))
- mtmsr r11
-#endif
-
-0: trap
- EMIT_BUG_ENTRY 0b,__FILE__,__LINE__, BUGFLAG_WARNING
-
- li r3, ENOSYS
- crset so
-#if defined(CONFIG_PPC_8xx) && defined(CONFIG_PERF_EVENTS)
- mtspr SPRN_NRI, r0
-#endif
- mtspr SPRN_SRR0, r9
- mtspr SPRN_SRR1, r10
- rfi
-#ifdef CONFIG_40x
- b . /* Prevent prefetch past rfi */
-#endif
-_ASM_NOKPROBE_SYMBOL(ret_from_kernel_syscall)
-
/*
* Top-level page fault handling.
* This is in assembler because if do_page_fault tells us that
diff --git a/arch/powerpc/kernel/head_32.h b/arch/powerpc/kernel/head_32.h
index fea7fe00a690..282d8fd443a9 100644
--- a/arch/powerpc/kernel/head_32.h
+++ b/arch/powerpc/kernel/head_32.h
@@ -118,8 +118,6 @@
.macro SYSCALL_ENTRY trapno
mfspr r9, SPRN_SRR1
mfspr r10, SPRN_SRR0
- andi. r11, r9, MSR_PR
- beq- 99f
LOAD_REG_IMMEDIATE(r11, MSR_KERNEL) /* can take exceptions */
lis r12, 1f@h
ori r12, r12, 1f@l
@@ -174,7 +172,6 @@
3:
#endif
b transfer_to_syscall /* jump to handler */
-99: b ret_from_kernel_syscall
.endm

.macro save_dar_dsisr_on_stack reg1, reg2, sp
diff --git a/arch/powerpc/kernel/head_booke.h b/arch/powerpc/kernel/head_booke.h
index db931f1167aa..bfbd240cc8a2 100644
--- a/arch/powerpc/kernel/head_booke.h
+++ b/arch/powerpc/kernel/head_booke.h
@@ -106,10 +106,8 @@ ALT_FTR_SECTION_END_IFSET(CPU_FTR_EMB_HV)
#endif
mfspr r9, SPRN_SRR1
BOOKE_CLEAR_BTB(r11)
- andi. r11, r9, MSR_PR
lwz r11, TASK_STACK - THREAD(r10)
rlwinm r12,r12,0,4,2 /* Clear SO bit in CR */
- beq- 99f
ALLOC_STACK_FRAME(r11, THREAD_SIZE - INT_FRAME_SIZE)
stw r12, _CCR(r11) /* save various registers */
mflr r12
@@ -155,7 +153,6 @@ ALT_FTR_SECTION_END_IFSET(CPU_FTR_EMB_HV)

3:
b transfer_to_syscall /* jump to handler */
-99: b ret_from_kernel_syscall
.endm

/* To handle the additional exception priority levels on 40x and Book-E
--
2.25.0