v4.19.13 snapshot.
diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile
new file mode 100644
index 0000000..3cf302b
--- /dev/null
+++ b/arch/x86/purgatory/Makefile
@@ -0,0 +1,37 @@
+# SPDX-License-Identifier: GPL-2.0
+OBJECT_FILES_NON_STANDARD := y
+
+purgatory-y := purgatory.o stack.o setup-x86_$(BITS).o sha256.o entry64.o string.o
+
+targets += $(purgatory-y)
+PURGATORY_OBJS = $(addprefix $(obj)/,$(purgatory-y))
+
+$(obj)/sha256.o: $(srctree)/lib/sha256.c FORCE
+ $(call if_changed_rule,cc_o_c)
+
+LDFLAGS_purgatory.ro := -e purgatory_start -r --no-undefined -nostdlib -z nodefaultlib
+targets += purgatory.ro
+
+KASAN_SANITIZE := n
+KCOV_INSTRUMENT := n
+
+# Default KBUILD_CFLAGS can have -pg option set when FTRACE is enabled. That
+# in turn leaves some undefined symbols like __fentry__ in purgatory and not
+# sure how to relocate those. Like kexec-tools, use custom flags.
+
+KBUILD_CFLAGS := -fno-strict-aliasing -Wall -Wstrict-prototypes -fno-zero-initialized-in-bss -fno-builtin -ffreestanding -c -Os -mcmodel=large
+KBUILD_CFLAGS += -m$(BITS)
+KBUILD_CFLAGS += $(call cc-option,-fno-PIE)
+
+$(obj)/purgatory.ro: $(PURGATORY_OBJS) FORCE
+ $(call if_changed,ld)
+
+targets += kexec-purgatory.c
+
+quiet_cmd_bin2c = BIN2C $@
+ cmd_bin2c = $(objtree)/scripts/bin2c kexec_purgatory < $< > $@
+
+$(obj)/kexec-purgatory.c: $(obj)/purgatory.ro FORCE
+ $(call if_changed,bin2c)
+
+obj-$(CONFIG_KEXEC_FILE) += kexec-purgatory.o
diff --git a/arch/x86/purgatory/entry64.S b/arch/x86/purgatory/entry64.S
new file mode 100644
index 0000000..d1a4291
--- /dev/null
+++ b/arch/x86/purgatory/entry64.S
@@ -0,0 +1,101 @@
+/*
+ * Copyright (C) 2003,2004 Eric Biederman (ebiederm@xmission.com)
+ * Copyright (C) 2014 Red Hat Inc.
+
+ * Author(s): Vivek Goyal <vgoyal@redhat.com>
+ *
+ * This code has been taken from kexec-tools.
+ *
+ * This source code is licensed under the GNU General Public License,
+ * Version 2. See the file COPYING for more details.
+ */
+
+ .text
+ .balign 16
+ .code64
+ .globl entry64, entry64_regs
+
+
+entry64:
+ /* Setup a gdt that should be preserved */
+ lgdt gdt(%rip)
+
+ /* load the data segments */
+ movl $0x18, %eax /* data segment */
+ movl %eax, %ds
+ movl %eax, %es
+ movl %eax, %ss
+ movl %eax, %fs
+ movl %eax, %gs
+
+ /* Setup new stack */
+ leaq stack_init(%rip), %rsp
+ pushq $0x10 /* CS */
+ leaq new_cs_exit(%rip), %rax
+ pushq %rax
+ lretq
+new_cs_exit:
+
+ /* Load the registers */
+ movq rax(%rip), %rax
+ movq rbx(%rip), %rbx
+ movq rcx(%rip), %rcx
+ movq rdx(%rip), %rdx
+ movq rsi(%rip), %rsi
+ movq rdi(%rip), %rdi
+ movq rsp(%rip), %rsp
+ movq rbp(%rip), %rbp
+ movq r8(%rip), %r8
+ movq r9(%rip), %r9
+ movq r10(%rip), %r10
+ movq r11(%rip), %r11
+ movq r12(%rip), %r12
+ movq r13(%rip), %r13
+ movq r14(%rip), %r14
+ movq r15(%rip), %r15
+
+ /* Jump to the new code... */
+ jmpq *rip(%rip)
+
+ .section ".rodata"
+ .balign 4
+entry64_regs:
+rax: .quad 0x0
+rcx: .quad 0x0
+rdx: .quad 0x0
+rbx: .quad 0x0
+rsp: .quad 0x0
+rbp: .quad 0x0
+rsi: .quad 0x0
+rdi: .quad 0x0
+r8: .quad 0x0
+r9: .quad 0x0
+r10: .quad 0x0
+r11: .quad 0x0
+r12: .quad 0x0
+r13: .quad 0x0
+r14: .quad 0x0
+r15: .quad 0x0
+rip: .quad 0x0
+ .size entry64_regs, . - entry64_regs
+
+ /* GDT */
+ .section ".rodata"
+ .balign 16
+gdt:
+ /* 0x00 unusable segment
+ * 0x08 unused
+ * so use them as gdt ptr
+ */
+ .word gdt_end - gdt - 1
+ .quad gdt
+ .word 0, 0, 0
+
+ /* 0x10 4GB flat code segment */
+ .word 0xFFFF, 0x0000, 0x9A00, 0x00AF
+
+ /* 0x18 4GB flat data segment */
+ .word 0xFFFF, 0x0000, 0x9200, 0x00CF
+gdt_end:
+stack: .quad 0, 0
+stack_init:
diff --git a/arch/x86/purgatory/purgatory.c b/arch/x86/purgatory/purgatory.c
new file mode 100644
index 0000000..025c34a
--- /dev/null
+++ b/arch/x86/purgatory/purgatory.c
@@ -0,0 +1,72 @@
+/*
+ * purgatory: Runs between two kernels
+ *
+ * Copyright (C) 2014 Red Hat Inc.
+ *
+ * Author:
+ * Vivek Goyal <vgoyal@redhat.com>
+ *
+ * This source code is licensed under the GNU General Public License,
+ * Version 2. See the file COPYING for more details.
+ */
+
+#include <linux/bug.h>
+#include <linux/sha256.h>
+#include <asm/purgatory.h>
+
+#include "../boot/string.h"
+
+unsigned long purgatory_backup_dest __section(.kexec-purgatory);
+unsigned long purgatory_backup_src __section(.kexec-purgatory);
+unsigned long purgatory_backup_sz __section(.kexec-purgatory);
+
+u8 purgatory_sha256_digest[SHA256_DIGEST_SIZE] __section(.kexec-purgatory);
+
+struct kexec_sha_region purgatory_sha_regions[KEXEC_SEGMENT_MAX] __section(.kexec-purgatory);
+
+/*
+ * On x86, second kernel requries first 640K of memory to boot. Copy
+ * first 640K to a backup region in reserved memory range so that second
+ * kernel can use first 640K.
+ */
+static int copy_backup_region(void)
+{
+ if (purgatory_backup_dest) {
+ memcpy((void *)purgatory_backup_dest,
+ (void *)purgatory_backup_src, purgatory_backup_sz);
+ }
+ return 0;
+}
+
+static int verify_sha256_digest(void)
+{
+ struct kexec_sha_region *ptr, *end;
+ u8 digest[SHA256_DIGEST_SIZE];
+ struct sha256_state sctx;
+
+ sha256_init(&sctx);
+ end = purgatory_sha_regions + ARRAY_SIZE(purgatory_sha_regions);
+
+ for (ptr = purgatory_sha_regions; ptr < end; ptr++)
+ sha256_update(&sctx, (uint8_t *)(ptr->start), ptr->len);
+
+ sha256_final(&sctx, digest);
+
+ if (memcmp(digest, purgatory_sha256_digest, sizeof(digest)))
+ return 1;
+
+ return 0;
+}
+
+void purgatory(void)
+{
+ int ret;
+
+ ret = verify_sha256_digest();
+ if (ret) {
+ /* loop forever */
+ for (;;)
+ ;
+ }
+ copy_backup_region();
+}
diff --git a/arch/x86/purgatory/setup-x86_64.S b/arch/x86/purgatory/setup-x86_64.S
new file mode 100644
index 0000000..dfae9b9
--- /dev/null
+++ b/arch/x86/purgatory/setup-x86_64.S
@@ -0,0 +1,59 @@
+/*
+ * purgatory: setup code
+ *
+ * Copyright (C) 2003,2004 Eric Biederman (ebiederm@xmission.com)
+ * Copyright (C) 2014 Red Hat Inc.
+ *
+ * This code has been taken from kexec-tools.
+ *
+ * This source code is licensed under the GNU General Public License,
+ * Version 2. See the file COPYING for more details.
+ */
+#include <asm/purgatory.h>
+
+ .text
+ .globl purgatory_start
+ .balign 16
+purgatory_start:
+ .code64
+
+ /* Load a gdt so I know what the segment registers are */
+ lgdt gdt(%rip)
+
+ /* load the data segments */
+ movl $0x18, %eax /* data segment */
+ movl %eax, %ds
+ movl %eax, %es
+ movl %eax, %ss
+ movl %eax, %fs
+ movl %eax, %gs
+
+ /* Setup a stack */
+ leaq lstack_end(%rip), %rsp
+
+ /* Call the C code */
+ call purgatory
+ jmp entry64
+
+ .section ".rodata"
+ .balign 16
+gdt: /* 0x00 unusable segment
+ * 0x08 unused
+ * so use them as the gdt ptr
+ */
+ .word gdt_end - gdt - 1
+ .quad gdt
+ .word 0, 0, 0
+
+ /* 0x10 4GB flat code segment */
+ .word 0xFFFF, 0x0000, 0x9A00, 0x00AF
+
+ /* 0x18 4GB flat data segment */
+ .word 0xFFFF, 0x0000, 0x9200, 0x00CF
+gdt_end:
+
+ .bss
+ .balign 4096
+lstack:
+ .skip 4096
+lstack_end:
diff --git a/arch/x86/purgatory/stack.S b/arch/x86/purgatory/stack.S
new file mode 100644
index 0000000..50a4147
--- /dev/null
+++ b/arch/x86/purgatory/stack.S
@@ -0,0 +1,19 @@
+/*
+ * purgatory: stack
+ *
+ * Copyright (C) 2014 Red Hat Inc.
+ *
+ * This source code is licensed under the GNU General Public License,
+ * Version 2. See the file COPYING for more details.
+ */
+
+ /* A stack for the loaded kernel.
+ * Separate and in the data section so it can be prepopulated.
+ */
+ .data
+ .balign 4096
+ .globl stack, stack_end
+
+stack:
+ .skip 4096
+stack_end:
diff --git a/arch/x86/purgatory/string.c b/arch/x86/purgatory/string.c
new file mode 100644
index 0000000..795ca4f
--- /dev/null
+++ b/arch/x86/purgatory/string.c
@@ -0,0 +1,25 @@
+/*
+ * Simple string functions.
+ *
+ * Copyright (C) 2014 Red Hat Inc.
+ *
+ * Author:
+ * Vivek Goyal <vgoyal@redhat.com>
+ *
+ * This source code is licensed under the GNU General Public License,
+ * Version 2. See the file COPYING for more details.
+ */
+
+#include <linux/types.h>
+
+#include "../boot/string.c"
+
+void *memcpy(void *dst, const void *src, size_t len)
+{
+ return __builtin_memcpy(dst, src, len);
+}
+
+void *memset(void *dst, int c, size_t len)
+{
+ return __builtin_memset(dst, c, len);
+}