LoongArch: kdump: Add single kernel image implementation

This feature depends on the kernel being relocatable.

Enable using single kernel image for kdump, and then no longer need to
build two kernels (production kernel and capture kernel share a single
kernel image).

Also enable CONFIG_CRASH_DUMP in loongson3_defconfig.
Signed-off-by: Youling Tang <tangyouling@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

arch/loongarch/Kconfig

@@ -473,6 +473,7 @@ config KEXEC
 
 config CRASH_DUMP
 	bool "Build kdump crash kernel"
+	select RELOCATABLE
 	help
 	  Generate crash dump after being started by kexec. This should
 	  be normally only set in special crash dump kernels which are
@@ -482,17 +483,6 @@ config CRASH_DUMP
 
 	  For more details see Documentation/admin-guide/kdump/kdump.rst
 
-config PHYSICAL_START
-	hex "Physical address where the kernel is loaded"
-	default "0x90000000a0000000"
-	depends on CRASH_DUMP
-	help
-	  This gives the XKPRANGE address where the kernel is loaded.
-	  If you plan to use kernel for capturing the crash dump change
-	  this value to start of the reserved region (the "X" value as
-	  specified in the "crashkernel=YM@XM" command line boot parameter
-	  passed to the panic-ed kernel).
-
 config RELOCATABLE
 	bool "Relocatable kernel"
 	help

arch/loongarch/Makefile

@@ -79,11 +79,7 @@ endif
 cflags-y += -ffreestanding
 cflags-y += $(call cc-option, -mno-check-zero-division)
 
-ifndef CONFIG_PHYSICAL_START
 load-y		= 0x9000000000200000
-else
-load-y		= $(CONFIG_PHYSICAL_START)
-endif
 bootvars-y	= VMLINUX_LOAD_ADDRESS=$(load-y)
 
 drivers-$(CONFIG_PCI)		+= arch/loongarch/pci/

arch/loongarch/configs/loongson3_defconfig

@@ -48,6 +48,7 @@ CONFIG_HOTPLUG_CPU=y
 CONFIG_NR_CPUS=64
 CONFIG_NUMA=y
 CONFIG_KEXEC=y
+CONFIG_CRASH_DUMP=y
 CONFIG_SUSPEND=y
 CONFIG_HIBERNATION=y
 CONFIG_ACPI=y

arch/loongarch/include/asm/addrspace.h

@@ -125,4 +125,6 @@ extern unsigned long vm_map_base;
 #define ISA_IOSIZE	SZ_16K
 #define IO_SPACE_LIMIT	(PCI_IOSIZE - 1)
 
+#define PHYS_LINK_KADDR	PHYSADDR(VMLINUX_LOAD_ADDRESS)
+
 #endif /* _ASM_ADDRSPACE_H */

arch/loongarch/kernel/head.S

@@ -24,7 +24,7 @@ _head:
 	.org	0x8
 	.dword	kernel_entry		/* Kernel entry point */
 	.dword	_end - _text		/* Kernel image effective size */
-	.quad	0			/* Kernel image load offset from start of RAM */
+	.quad	PHYS_LINK_KADDR		/* Kernel image load offset from start of RAM */
 	.org	0x38			/* 0x20 ~ 0x37 reserved */
 	.long	LINUX_PE_MAGIC
 	.long	pe_header - _head	/* Offset to the PE header */