kexec: support for kexec on panic using new system call

This patch adds support for loading a kexec on panic (kdump) kernel usning
new system call.

It prepares ELF headers for memory areas to be dumped and for saved cpu
registers.  Also prepares the memory map for second kernel and limits its
boot to reserved areas only.

Signed-off-by: Vivek Goyal <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Michael Kerrisk <[email protected]>
Cc: Yinghai Lu <[email protected]>
Cc: Eric Biederman <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Matthew Garrett <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Dave Young <[email protected]>
Cc: WANG Chao <[email protected]>
Cc: Baoquan He <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

arch/x86/include/asm/crash.h

@@ -0,0 +1,9 @@
+#ifndef _ASM_X86_CRASH_H
+#define _ASM_X86_CRASH_H
+
+int crash_load_segments(struct kimage *image);
+int crash_copy_backup_region(struct kimage *image);
+int crash_setup_memmap_entries(struct kimage *image,
+		struct boot_params *params);
+
+#endif /* _ASM_X86_CRASH_H */

arch/x86/include/asm/kexec.h

@@ -25,6 +25,8 @@
 #include <asm/ptrace.h>
 #include <asm/bootparam.h>
 
+struct kimage;
+
 /*
  * KEXEC_SOURCE_MEMORY_LIMIT maximum page get_free_page can return.
  * I.e. Maximum page that is mapped directly into kernel memory,
@@ -62,6 +64,10 @@
 # define KEXEC_ARCH KEXEC_ARCH_X86_64
 #endif
 
+/* Memory to backup during crash kdump */
+#define KEXEC_BACKUP_SRC_START	(0UL)
+#define KEXEC_BACKUP_SRC_END	(640 * 1024UL)	/* 640K */
+
 /*
  * CPU does not save ss and sp on stack if execution is already
  * running in kernel mode at the time of NMI occurrence. This code
@@ -161,17 +167,35 @@ struct kimage_arch {
 	pud_t *pud;
 	pmd_t *pmd;
 	pte_t *pte;
+	/* Details of backup region */
+	unsigned long backup_src_start;
+	unsigned long backup_src_sz;
+
+	/* Physical address of backup segment */
+	unsigned long backup_load_addr;
+
+	/* Core ELF header buffer */
+	void *elf_headers;
+	unsigned long elf_headers_sz;
+	unsigned long elf_load_addr;
 };
+#endif /* CONFIG_X86_32 */
 
+#ifdef CONFIG_X86_64
+/*
+ * Number of elements and order of elements in this structure should match
+ * with the ones in arch/x86/purgatory/entry64.S. If you make a change here
+ * make an appropriate change in purgatory too.
+ */
 struct kexec_entry64_regs {
 	uint64_t rax;
-	uint64_t rbx;
 	uint64_t rcx;
 	uint64_t rdx;
-	uint64_t rsi;
-	uint64_t rdi;
+	uint64_t rbx;
 	uint64_t rsp;
 	uint64_t rbp;
+	uint64_t rsi;
+	uint64_t rdi;
 	uint64_t r8;
 	uint64_t r9;
 	uint64_t r10;