File-copy from v4.4.100
This is the result of 'cp' from a linux-stable tree with the 'v4.4.100'
tag checked out (commit 26d6298789e695c9f627ce49a7bbd2286405798a) on
git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Please refer to that tree for all history prior to this point.
Change-Id: I8a9ee2aea93cd29c52c847d0ce33091a73ae6afe
diff --git a/arch/x86/realmode/rm/trampoline_32.S b/arch/x86/realmode/rm/trampoline_32.S
new file mode 100644
index 0000000..48ddd76
--- /dev/null
+++ b/arch/x86/realmode/rm/trampoline_32.S
@@ -0,0 +1,73 @@
+/*
+ *
+ * Trampoline.S Derived from Setup.S by Linus Torvalds
+ *
+ * 4 Jan 1997 Michael Chastain: changed to gnu as.
+ *
+ * This is only used for booting secondary CPUs in SMP machine
+ *
+ * Entry: CS:IP point to the start of our code, we are
+ * in real mode with no stack, but the rest of the
+ * trampoline page to make our stack and everything else
+ * is a mystery.
+ *
+ * We jump into arch/x86/kernel/head_32.S.
+ *
+ * On entry to trampoline_start, the processor is in real mode
+ * with 16-bit addressing and 16-bit data. CS has some value
+ * and IP is zero. Thus, we load CS to the physical segment
+ * of the real mode code before doing anything further.
+ */
+
+#include <linux/linkage.h>
+#include <asm/segment.h>
+#include <asm/page_types.h>
+#include "realmode.h"
+
+ .text
+ .code16
+
+ .balign PAGE_SIZE
+ENTRY(trampoline_start)
+ wbinvd # Needed for NUMA-Q should be harmless for others
+
+ LJMPW_RM(1f)
+1:
+ mov %cs, %ax # Code and data in the same place
+ mov %ax, %ds
+
+ cli # We should be safe anyway
+
+ movl tr_start, %eax # where we need to go
+
+ movl $0xA5A5A5A5, trampoline_status
+ # write marker for master knows we're running
+
+ /*
+ * GDT tables in non default location kernel can be beyond 16MB and
+ * lgdt will not be able to load the address as in real mode default
+ * operand size is 16bit. Use lgdtl instead to force operand size
+ * to 32 bit.
+ */
+ lidtl tr_idt # load idt with 0, 0
+ lgdtl tr_gdt # load gdt with whatever is appropriate
+
+ movw $1, %dx # protected mode (PE) bit
+ lmsw %dx # into protected mode
+
+ ljmpl $__BOOT_CS, $pa_startup_32
+
+ .section ".text32","ax"
+ .code32
+ENTRY(startup_32) # note: also used from wakeup_asm.S
+ jmp *%eax
+
+ .bss
+ .balign 8
+GLOBAL(trampoline_header)
+ tr_start: .space 4
+ tr_gdt_pad: .space 2
+ tr_gdt: .space 6
+END(trampoline_header)
+
+#include "trampoline_common.S"