From: Benjamin Herrenschmidt <b...@kernel.crashing.org>
Create a trampoline that works in either endian and flips to
the expected endian. Use it for primary and secondary thread
entry as well as RTAS and OF call return.
Signed-off-by: Benjamin Herrenschmidt <b...@kernel.crashing.org>
Signed-off-by: Anton Blanchard <an...@samba.org>
---
arch/powerpc/include/asm/ppc_asm.h | 31 ++++++++++++++++++++++++++++++-
arch/powerpc/kernel/entry_64.S | 36 ++++++++++++++++++++----------------
arch/powerpc/kernel/head_64.S | 2 ++
3 files changed, 52 insertions(+), 17 deletions(-)
diff --git a/arch/powerpc/include/asm/ppc_asm.h
b/arch/powerpc/include/asm/ppc_asm.h
index bc606e4..f9d8418 100644
--- a/arch/powerpc/include/asm/ppc_asm.h
+++ b/arch/powerpc/include/asm/ppc_asm.h
@@ -845,6 +845,35 @@ END_FTR_SECTION_NESTED(CPU_FTR_HAS_PPR,CPU_FTR_HAS_PPR,946)
#define N_SLINE 68
#define N_SO 100
-#endif /* __ASSEMBLY__ */
+/*
+ * Create an endian fixup trampoline
+ *
+ * This starts with a "tdi 0,0,0x48" instruction which is
+ * essentially a "trap never", and thus akin to a nop.
+ *
+ * The opcode for this instruction read with the wrong endian
+ * however results in a b . + 8
+ *
+ * So essentially we use that trick to execute the following
+ * trampoline in "reverse endian" if we are running with the
+ * MSR_LE bit set the "wrong" way for whatever endianness the
+ * kernel is built for.
+ */
+#ifdef CONFIG_PPC_BOOK3E
+#define FIXUP_ENDIAN
+#else
+#define FIXUP_ENDIAN \
+ tdi 0,0,0x48; /* Reverse endian of b . + 8 */ \
+ b $+36; /* Skip trampoline if endian is good */ \
+ .long 0x05009f42; /* bcl 20,31,$+4 */ \
+ .long 0xa602487d; /* mflr r10 */ \
+ .long 0x1c004a39; /* addi r10,r10,28 */ \
+ .long 0xa600607d; /* mfmsr r11 */ \
+ .long 0x01006b69; /* xori r11,r11,1 */ \
+ .long 0xa6035a7d; /* mtsrr0 r10 */ \
+ .long 0xa6037b7d; /* mtsrr1 r11 */ \
+ .long 0x2400004c /* rfid */
+#endif /* !CONFIG_PPC_BOOK3E */
+#endif /* __ASSEMBLY__ */
#endif /* _ASM_POWERPC_PPC_ASM_H */
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 209e8ce..5694e1f 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -1020,7 +1020,7 @@ _GLOBAL(enter_rtas)
li r9,1
rldicr r9,r9,MSR_SF_LG,(63-MSR_SF_LG)
- ori r9,r9,MSR_IR|MSR_DR|MSR_FE0|MSR_FE1|MSR_FP|MSR_RI
+ ori r9,r9,MSR_IR|MSR_DR|MSR_FE0|MSR_FE1|MSR_FP|MSR_RI|MSR_LE
andc r6,r0,r9
sync /* disable interrupts so SRR0/1 */
mtmsrd r0 /* don't get trashed */
@@ -1035,6 +1035,8 @@ _GLOBAL(enter_rtas)
b . /* prevent speculative execution */
_STATIC(rtas_return_loc)
+ FIXUP_ENDIAN
+
/* relocation is off at this point */
GET_PACA(r4)
clrldi r4,r4,2 /* convert to realmode address */
@@ -1106,28 +1108,30 @@ _GLOBAL(enter_prom)
std r10,_CCR(r1)
std r11,_MSR(r1)
- /* Get the PROM entrypoint */
- mtlr r4
+ /* Put PROM address in SRR0 */
+ mtsrr0 r4
+
+ /* Setup our trampoline return addr in LR */
+ bcl 20,31,$+4
+0: mflr r4
+ addi r4,r4,(1f - 0b)
+ mtlr r4
- /* Switch MSR to 32 bits mode
+ /* Prepare a 32-bit mode big endian MSR
*/
#ifdef CONFIG_PPC_BOOK3E
rlwinm r11,r11,0,1,31
- mtmsr r11
+ mtsrr1 r11
+ rfi
#else /* CONFIG_PPC_BOOK3E */
- mfmsr r11
- li r12,1
- rldicr r12,r12,MSR_SF_LG,(63-MSR_SF_LG)
- andc r11,r11,r12
- li r12,1
- rldicr r12,r12,MSR_ISF_LG,(63-MSR_ISF_LG)
- andc r11,r11,r12
- mtmsrd r11
+ LOAD_REG_IMMEDIATE(r12, MSR_SF | MSR_ISF | MSR_LE)
+ andc r11,r11,r12
+ mtsrr1 r11
+ rfid
#endif /* CONFIG_PPC_BOOK3E */
- isync
- /* Enter PROM here... */
- blrl
+1: /* Return from OF */
+ FIXUP_ENDIAN
/* Just make sure that r1 top 32 bits didn't get
* corrupt by OF
diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index 3d11d80..065d10f 100644
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S
@@ -68,6 +68,7 @@ _stext:
_GLOBAL(__start)
/* NOP this out unconditionally */
BEGIN_FTR_SECTION
+ FIXUP_ENDIAN
b .__start_initialization_multiplatform
END_FTR_SECTION(0, 1)
@@ -115,6 +116,7 @@ __run_at_load:
*/
.globl __secondary_hold
__secondary_hold:
+ FIXUP_ENDIAN
#ifndef CONFIG_PPC_BOOK3E
mfmsr r24
ori r24,r24,MSR_RI
--
1.8.1.2
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