[PATCH v7 05/12] powerpc/fsl_booke/32: introduce reloc_kernel_entry() helper

[Jason Yan]

Add a new helper reloc_kernel_entry() to jump back to the start of the
new kernel. After we put the new kernel in a randomized place we can use
this new helper to enter the kernel and begin to relocate again.

Signed-off-by: Jason Yan <yanaijie@xxxxxxxxxx>
Cc: Diana Craciun <diana.craciun@xxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Christophe Leroy <christophe.leroy@xxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Reviewed-by: Christophe Leroy <christophe.leroy@xxxxxx>
Reviewed-by: Diana Craciun <diana.craciun@xxxxxxx>
Tested-by: Diana Craciun <diana.craciun@xxxxxxx>
---
 arch/powerpc/kernel/head_fsl_booke.S | 13 +++++++++++++
 arch/powerpc/mm/mmu_decl.h           |  1 +
 2 files changed, 14 insertions(+)

diff --git a/arch/powerpc/kernel/head_fsl_booke.S b/arch/powerpc/kernel/head_fsl_booke.S
index 8c1928176ffe..d9f599b01ff1 100644
--- a/arch/powerpc/kernel/head_fsl_booke.S
+++ b/arch/powerpc/kernel/head_fsl_booke.S
@@ -1149,6 +1149,19 @@ _GLOBAL(create_kaslr_tlb_entry)
 	sync
 	blr
 
+/*
+ * Return to the start of the relocated kernel and run again
+ * r3 - virtual address of fdt
+ * r4 - entry of the kernel
+ */
+_GLOBAL(reloc_kernel_entry)
+	mfmsr	r7
+	rlwinm	r7, r7, 0, ~(MSR_IS | MSR_DS)
+
+	mtspr	SPRN_SRR0,r4
+	mtspr	SPRN_SRR1,r7
+	rfi
+
 /*
  * Create a tlb entry with the same effective and physical address as
  * the tlb entry used by the current running code. But set the TS to 1.
diff --git a/arch/powerpc/mm/mmu_decl.h b/arch/powerpc/mm/mmu_decl.h
index a492ece08f64..55e86a0bf562 100644
--- a/arch/powerpc/mm/mmu_decl.h
+++ b/arch/powerpc/mm/mmu_decl.h
@@ -143,6 +143,7 @@ extern void adjust_total_lowmem(void);
 extern int switch_to_as1(void);
 extern void restore_to_as0(int esel, int offset, void *dt_ptr, int bootcpu);
 void create_kaslr_tlb_entry(int entry, unsigned long virt, phys_addr_t phys);
+void reloc_kernel_entry(void *fdt, int addr);
 #endif
 extern void loadcam_entry(unsigned int index);
 extern void loadcam_multi(int first_idx, int num, int tmp_idx);
-- 
2.17.2