powerpc/64s: move some exception handlers out of line

stable inclusion
from linux-4.19.159
commit b4e80478115bc7fcea627110c133f4afe1a40899
CVE: CVE-2020-4788

--------------------------------

(backport only)

We're about to grow the exception handlers, which will make a bunch of them
no longer fit within the space available. We move them out of line.

This is a fiddly and error-prone business, so in the interests of reviewability
I haven't merged this in with the addition of the entry flush.
Signed-off-by: NDaniel Axtens <dja@axtens.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Reviewed-by: NJason Yan <yanaijie@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

arch/powerpc/kernel/exceptions-64s.S

@@ -572,13 +572,16 @@ ALT_MMU_FTR_SECTION_END_IFCLR(MMU_FTR_TYPE_RADIX)
 EXC_REAL_BEGIN(data_access_slb, 0x380, 0x80)
 	SET_SCRATCH0(r13)
 	EXCEPTION_PROLOG_0(PACA_EXSLB)
+	b tramp_data_access_slb
+EXC_REAL_END(data_access_slb, 0x380, 0x80)
+
+TRAMP_REAL_BEGIN(tramp_data_access_slb)
 	EXCEPTION_PROLOG_1(PACA_EXSLB, KVMTEST_PR, 0x380)
 	mr	r12,r3	/* save r3 */
 	mfspr	r3,SPRN_DAR
 	mfspr	r11,SPRN_SRR1
 	crset	4*cr6+eq
 	BRANCH_TO_COMMON(r10, slb_miss_common)
-EXC_REAL_END(data_access_slb, 0x380, 0x80)
 
 EXC_VIRT_BEGIN(data_access_slb, 0x4380, 0x80)
 	SET_SCRATCH0(r13)
@@ -616,13 +619,16 @@ ALT_MMU_FTR_SECTION_END_IFCLR(MMU_FTR_TYPE_RADIX)
 EXC_REAL_BEGIN(instruction_access_slb, 0x480, 0x80)
 	SET_SCRATCH0(r13)
 	EXCEPTION_PROLOG_0(PACA_EXSLB)
+	b tramp_instruction_access_slb
+EXC_REAL_END(instruction_access_slb, 0x480, 0x80)
+
+TRAMP_REAL_BEGIN(tramp_instruction_access_slb)
 	EXCEPTION_PROLOG_1(PACA_EXSLB, KVMTEST_PR, 0x480)
 	mr	r12,r3	/* save r3 */
 	mfspr	r3,SPRN_SRR0		/* SRR0 is faulting address */
 	mfspr	r11,SPRN_SRR1
 	crclr	4*cr6+eq
 	BRANCH_TO_COMMON(r10, slb_miss_common)
-EXC_REAL_END(instruction_access_slb, 0x480, 0x80)
 
 EXC_VIRT_BEGIN(instruction_access_slb, 0x4480, 0x80)
 	SET_SCRATCH0(r13)