[RFC PATCH v2 08/10] powerpc/8xx: Enable CONFIG_VMAP_STACK

[Christophe Leroy]

This patch enables CONFIG_VMAP_STACK. For that, a few changes are
done in head_8xx.S.

Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
---
 arch/powerpc/Kconfig           |  1 +
 arch/powerpc/kernel/head_8xx.S | 47 +++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 6137f5e3bb2d..ddbec19c3c22 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -178,6 +178,7 @@ config PPC
 	select HAVE_ARCH_NVRAM_OPS
 	select HAVE_ARCH_SECCOMP_FILTER
 	select HAVE_ARCH_TRACEHOOK
+	select HAVE_ARCH_VMAP_STACK		if PPC_8xx
 	select HAVE_C_RECORDMCOUNT
 	select HAVE_CBPF_JIT			if !PPC64
 	select HAVE_STACKPROTECTOR		if PPC64 && $(cc-option,-mstack-protector-guard=tls -mstack-protector-guard-reg=r13)
diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index 2fa02ae7a88c..dfd68b72688e 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S
@@ -127,8 +127,12 @@ instruction_counter:
 	. = 0x200
 MachineCheck:
 	EXCEPTION_PROLOG
+#ifdef CONFIG_VMAP_STACK
+	lwz r4, _DAR(r11)
+#else
 	mfspr r4,SPRN_DAR
 	stw r4,_DAR(r11)
+#endif
 	li r5,RPN_PATTERN
 	mtspr SPRN_DAR,r5	/* Tag DAR, to be used in DTLB Error */
 	mfspr r5,SPRN_DSISR
@@ -143,8 +147,12 @@ MachineCheck:
 	. = 0x600
 Alignment:
 	EXCEPTION_PROLOG
+#ifdef CONFIG_VMAP_STACK
+	lwz r4, _DAR(r11)
+#else
 	mfspr	r4,SPRN_DAR
 	stw	r4,_DAR(r11)
+#endif
 	li	r5,RPN_PATTERN
 	mtspr	SPRN_DAR,r5	/* Tag DAR, to be used in DTLB Error */
 	mfspr	r5,SPRN_DSISR
@@ -467,17 +475,28 @@ DataTLBError:
 	cmpwi	cr0, r11, RPN_PATTERN
 	beq-	FixupDAR	/* must be a buggy dcbX, icbi insn. */
 DARFixed:/* Return from dcbx instruction bug workaround */
+#ifdef CONFIG_VMAP_STACK
+	li	r11, RPN_PATTERN
+	mtspr	SPRN_DAR, r11	/* Tag DAR, to be used in DTLB Error */
+	mfspr	r11, SPRN_SRR1
+#endif
 	EXCEPTION_PROLOG_1
 	EXCEPTION_PROLOG_2
 	mfspr	r5,SPRN_DSISR
 	stw	r5,_DSISR(r11)
+#ifdef CONFIG_VMAP_STACK
+	lwz r4, _DAR(r11)
+#else
 	mfspr	r4,SPRN_DAR
+#endif
 	andis.	r10,r5,DSISR_NOHPTE@h
 	beq+	.Ldtlbie
 	tlbie	r4
 .Ldtlbie:
+#ifndef CONFIG_VMAP_STACK
 	li	r10,RPN_PATTERN
 	mtspr	SPRN_DAR,r10	/* Tag DAR, to be used in DTLB Error */
+#endif
 	/* 0x300 is DataAccess exception, needed by bad_page_fault() */
 	EXC_XFER_LITE(0x300, handle_page_fault)
 
@@ -498,6 +517,9 @@ DARFixed:/* Return from dcbx instruction bug workaround */
  * using them.
  */
 do_databreakpoint:
+#ifdef CONFIG_VMAP_STACK
+	mfspr	r11, SPRN_SRR1
+#endif
 	EXCEPTION_PROLOG_1
 	EXCEPTION_PROLOG_2
 	addi	r3,r1,STACK_FRAME_OVERHEAD
@@ -508,8 +530,21 @@ do_databreakpoint:
 
 	. = 0x1c00
 DataBreakpoint:
-	EXCEPTION_PROLOG_0
+	mtspr	SPRN_SPRG_SCRATCH0, r10
+	mtspr	SPRN_SPRG_SCRATCH1, r11
+#ifdef CONFIG_VMAP_STACK
+	mfspr	r10, SPRN_SPRG_THREAD
+	mfspr	r11, SPRN_DAR
+	stw	r11, DAR(r10)
+	mfspr	r11, SPRN_SRR1
+	stw	r11, SRR1(r10)
+#endif
 	mfspr	r11, SPRN_SRR0
+#ifdef CONFIG_VMAP_STACK
+	stw	r11, SRR0(r10)
+#endif
+	mfcr	r10
+
 	cmplwi	cr0, r11, (.Ldtlbie - PAGE_OFFSET)@l
 	cmplwi	cr7, r11, (.Litlbie - PAGE_OFFSET)@l
 	cror	4*cr0+eq, 4*cr0+eq, 4*cr7+eq
@@ -625,7 +660,12 @@ modified_instr:
 	.space	4		/* this is where the add instr. is stored */
 	bne+	143f
 	subf	r10,r0,r10	/* r10=r10-r0, only if reg RA is r0 */
+#ifdef CONFIG_VMAP_STACK
+143:	mfspr	r11, SPRN_SPRG_THREAD
+	stw	r10, DAR(r11)
+#else
 143:	mtdar	r10		/* store faulting EA in DAR */
+#endif
 	mfspr	r10,SPRN_M_TW
 	b	DARFixed	/* Go back to normal TLB handling */
 #else
@@ -679,7 +719,12 @@ modified_instr:
 152:
 	mfdar	r11
 	mtctr	r11			/* restore ctr reg from DAR */
+#ifdef CONFIG_VMAP_STACK
+	mfspr	r11, SPRN_SPRG_THREAD
+	stw	r10, DAR(r11)
+#else
 	mtdar	r10			/* save fault EA to DAR */
+#endif
 	mfspr	r10,SPRN_M_TW
 	b	DARFixed		/* Go back to normal TLB handling */
 
-- 
2.13.3