powerpc/32: Wire up the trampoline code for kdump

Wire up the trampoline code for ppc32 to relay exceptions from the
vectors at address 0 to vectors at address 32MB, and modify Kconfig
to enable Kdump support for all classic powerpcs.
Signed-off-by: Dale Farnsworth <dale@farnsworth.org>
Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/Kconfig

@@ -326,7 +326,7 @@ config KEXEC
 
 config CRASH_DUMP
 	bool "Build a kdump crash kernel"
-	depends on PPC_MULTIPLATFORM && PPC64 && RELOCATABLE
+	depends on (PPC64 && RELOCATABLE) || 6xx
 	help
 	  Build a kernel suitable for use as a kdump capture kernel.
 	  The same kernel binary can be used as production kernel and dump

arch/powerpc/include/asm/kdump.h

 #ifndef _PPC64_KDUMP_H
 #define _PPC64_KDUMP_H
 
+#include <asm/page.h>
+
 /* Kdump kernel runs at 32 MB, change at your peril. */
 #define KDUMP_KERNELBASE	0x2000000
 
@@ -11,8 +13,19 @@
 
 #ifdef CONFIG_CRASH_DUMP
 
+/*
+ * On PPC64 translation is disabled during trampoline setup, so we use
+ * physical addresses. Though on PPC32 translation is already enabled,
+ * so we can't do the same. Luckily create_trampoline() creates relative
+ * branches, so we can just add the PAGE_OFFSET and don't worry about it.
+ */
+#ifdef __powerpc64__
 #define KDUMP_TRAMPOLINE_START	0x0100
 #define KDUMP_TRAMPOLINE_END	0x3000
+#else
+#define KDUMP_TRAMPOLINE_START	(0x0100 + PAGE_OFFSET)
+#define KDUMP_TRAMPOLINE_END	(0x3000 + PAGE_OFFSET)
+#endif /* __powerpc64__ */
 
 #define KDUMP_MIN_TCE_ENTRIES	2048
 

arch/powerpc/kernel/setup_32.c

@@ -126,6 +126,8 @@ notrace void __init machine_init(unsigned long dt_ptr)
 
 	probe_machine();
 
+	setup_kdump_trampoline();
+
 #ifdef CONFIG_6xx
 	if (cpu_has_feature(CPU_FTR_CAN_DOZE) ||
 	    cpu_has_feature(CPU_FTR_CAN_NAP))