Subject: [PATCH] powerpc/64: option to force run-at-load to test relocation

From: Nicholas Piggin <[email-masked]>
Date: Wed, 12 Oct 2016 17:57:19 +1100

This adds a config option that can help exercise the case when
the kernel is not running at PAGE_OFFSET.

Signed-off-by: Nicholas Piggin <[email-masked]>
---
 arch/powerpc/Kconfig               | 9 +++++++++
 arch/powerpc/kernel/head_64.S      | 4 ++++
 arch/powerpc/kernel/setup-common.c | 3 +++
 3 files changed, 16 insertions(+)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 65fba4c..5d43cb8 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -478,6 +478,15 @@ config RELOCATABLE
 	  setting can still be useful to bootwrappers that need to know the
 	  load address of the kernel (eg. u-boot/mkimage).
 
+config RELOCATABLE_TEST
+	bool "Test relocatable kernel"
+	depends on (PPC64 && RELOCATABLE)
+	default n
+	help
+	  This runs the relocatable kernel at the address it was initially
+	  loaded at, which tends to be non-zero and therefore test the
+	  relocation code.
+
 config CRASH_DUMP
 	bool "Build a kdump crash kernel"
 	depends on PPC64 || 6xx || FSL_BOOKE || (44x && !SMP)
diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index 79da0641..bc9ceac 100644
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S
@@ -111,8 +111,12 @@ __secondary_hold_acknowledge:
 	.globl	__run_at_load
 __run_at_load:
 DEFINE_FIXED_SYMBOL(__run_at_load)
+#ifdef CONFIG_RELOCATABLE_TEST
+	.long	0x1		/* Test relocation, do not relocate to 0 */
+#else
 	.long	0x72756e30	/* "run0" -- relocate to 0 by default */
 #endif
+#endif
 
 	. = 0x60
 /*
diff --git a/arch/powerpc/kernel/setup-common.c b/arch/powerpc/kernel/setup-common.c
index dba265c..18e0f19 100644
--- a/arch/powerpc/kernel/setup-common.c
+++ b/arch/powerpc/kernel/setup-common.c
@@ -795,6 +795,9 @@ static __init void print_system_info(void)
 	pr_info("mmu_features      = 0x%08x\n", cur_cpu_spec->mmu_features);
 #ifdef CONFIG_PPC64
 	pr_info("firmware_features = 0x%016lx\n", powerpc_firmware_features);
+
+	if (get_paca()->kernelbase != PAGE_OFFSET)
+		pr_info("kernelbase        = 0x%llx\n", get_paca()->kernelbase);
 #endif
 
 #ifdef CONFIG_PPC_STD_MMU_64
-- 
2.9.3