1 files changed, 80 insertions, 0 deletions
diff --git a/arch/i386/kernel/trampoline.S b/arch/i386/kernel/trampoline.S
new file mode 100644
index 000000000000..fcce0e61b0e7
--- /dev/null
+++ b/arch/i386/kernel/trampoline.S
@@ -0,0 +1,80 @@
+/*
+ *
+ *	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.
+ *
+ *	In fact we don't actually need a stack so we don't
+ *	set one up.
+ *
+ *	We jump into the boot/compressed/head.S code. So you'd
+ *	better be running a compressed kernel image or you
+ *	won't get very far.
+ *
+ *	On entry to trampoline_data, the processor is in real mode
+ *	with 16-bit addressing and 16-bit data.  CS has some value
+ *	and IP is zero.  Thus, data addresses need to be absolute
+ *	(no relocation) and are taken with regard to r_base.
+ *
+ *	If you work on this file, check the object module with
+ *	objdump --reloc to make sure there are no relocation
+ *	entries except for:
+ *
+ *	TYPE              VALUE
+ *	R_386_32          startup_32_smp
+ *	R_386_32          boot_gdt_table
+ */
+
+#include <linux/linkage.h>
+#include <asm/segment.h>
+#include <asm/page.h>
+
+.data
+
+.code16
+
+ENTRY(trampoline_data)
+r_base = .
+	wbinvd			# Needed for NUMA-Q should be harmless for others
+	mov	%cs, %ax	# Code and data in the same place
+	mov	%ax, %ds
+
+	cli			# We should be safe anyway
+
+	movl	$0xA5A5A5A5, trampoline_data - r_base
+				# 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	boot_idt - r_base	# load idt with 0, 0
+	lgdtl	boot_gdt - r_base	# load gdt with whatever is appropriate
+
+	xor	%ax, %ax
+	inc	%ax		# protected mode (PE) bit
+	lmsw	%ax		# into protected mode
+	# flush prefetch and jump to startup_32_smp in arch/i386/kernel/head.S
+	ljmpl	$__BOOT_CS, $(startup_32_smp-__PAGE_OFFSET)
+
+	# These need to be in the same 64K segment as the above;
+	# hence we don't use the boot_gdt_descr defined in head.S
+boot_gdt:
+	.word	__BOOT_DS + 7			# gdt limit
+	.long	boot_gdt_table-__PAGE_OFFSET	# gdt base
+
+boot_idt:
+	.word	0				# idt limit = 0
+	.long	0				# idt base = 0L
+
+.globl trampoline_end
+trampoline_end: