powerpc/32: Always enable data translation on syscall entry

If the code can use a stack in vm area, it can also use a
stack in linear space.

Simplify code by removing old non VMAP stack code on PPC32 in syscall.

That means the data translation is now re-enabled early in
syscall entry in all cases, not only when using VMAP stacks.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/412c6c1786922d991bbb89c2ad2e82cffe8ab112.1612796617.git.christophe.leroy@csgroup.eu

arch/powerpc/kernel/head_32.h

@@ -118,50 +118,31 @@
 .macro SYSCALL_ENTRY trapno
 	mfspr	r12,SPRN_SPRG_THREAD
 	mfspr	r9, SPRN_SRR1
-#ifdef CONFIG_VMAP_STACK
 	mfspr	r11, SPRN_SRR0
 	mtctr	r11
 	andi.	r11, r9, MSR_PR
 	mr	r11, r1
 	lwz	r1,TASK_STACK-THREAD(r12)
 	beq-	99f
 	addi	r1, r1, THREAD_SIZE - INT_FRAME_SIZE
-	li	r10, MSR_KERNEL & ~(MSR_IR | MSR_RI) /* can take DTLB miss */
+	LOAD_REG_IMMEDIATE(r10, MSR_KERNEL & ~(MSR_IR | MSR_RI)) /* can take DTLB miss */
 	mtmsr	r10
 	isync
 	tovirt(r12, r12)
 	stw	r11,GPR1(r1)
 	stw	r11,0(r1)
 	mr	r11, r1
-#else
-	andi.	r11, r9, MSR_PR
-	lwz	r11,TASK_STACK-THREAD(r12)
-	beq-	99f
-	addi	r11, r11, THREAD_SIZE - INT_FRAME_SIZE
-	tophys(r11, r11)
-	stw	r1,GPR1(r11)
-	stw	r1,0(r11)
-	tovirt(r1, r11)		/* set new kernel sp */
-#endif
 	mflr	r10
 	stw	r10, _LINK(r11)
-#ifdef CONFIG_VMAP_STACK
 	mfctr	r10
-#else
-	mfspr	r10,SPRN_SRR0
-#endif
 	stw	r10,_NIP(r11)
 	mfcr	r10
 	rlwinm	r10,r10,0,4,2	/* Clear SO bit in CR */
 	stw	r10,_CCR(r11)		/* save registers */
 #ifdef CONFIG_40x
 	rlwinm	r9,r9,0,14,12		/* clear MSR_WE (necessary?) */
 #else
-#ifdef CONFIG_VMAP_STACK
 	LOAD_REG_IMMEDIATE(r10, MSR_KERNEL & ~MSR_IR) /* can take exceptions */
-#else
-	LOAD_REG_IMMEDIATE(r10, MSR_KERNEL & ~(MSR_IR|MSR_DR)) /* can take exceptions */
-#endif
 	mtmsr	r10			/* (except for mach check in rtas) */
 #endif
 	lis	r10,STACK_FRAME_REGS_MARKER@ha /* exception frame marker */
@@ -190,7 +171,6 @@
 	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
@@ -200,7 +180,6 @@
 #endif
 
 3:
-	tovirt_novmstack r2, r2 	/* set r2 to current */
 	lis	r11, transfer_to_syscall@h
 	ori	r11, r11, transfer_to_syscall@l
 #ifdef CONFIG_TRACE_IRQFLAGS

arch/powerpc/kernel/head_booke.h

@@ -144,7 +144,6 @@ ALT_FTR_SECTION_END_IFSET(CPU_FTR_EMB_HV)
 	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
 #ifdef CONFIG_SMP
 	lwz	r10, TASK_CPU(r2)
@@ -158,7 +157,6 @@ ALT_FTR_SECTION_END_IFSET(CPU_FTR_EMB_HV)
 	stw	r12,4(r11)
 
 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