1 files changed, 85 insertions, 0 deletions

diff --git a/arch/x86/kernel/trampoline_32.S b/arch/x86/kernel/trampoline_32.S
new file mode 100644
index 000000000000..f62815f8d06a
--- /dev/null
+++ b/arch/x86/kernel/trampoline_32.S
@@ -0,0 +1,85 @@
+/*
+ *
+ *      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
+ */
+
+#include <linux/linkage.h>
+#include <asm/segment.h>
+#include <asm/page.h>
+
+.data
+
+/* We can free up trampoline after bootup if cpu hotplug is not supported. */
+#ifndef CONFIG_HOTPLUG_CPU
+.section ".init.data","aw",@progbits
+#endif
+
+.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_descr - r_base # load idt with 0, 0
+        lgdtl   boot_gdt_descr - 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_descr:
+        .word   __BOOT_DS + 7                   # gdt limit
+        .long   boot_gdt - __PAGE_OFFSET        # gdt base
+
+boot_idt_descr:
+        .word   0                               # idt limit = 0
+        .long   0                               # idt base = 0L
+
+.globl trampoline_end
+trampoline_end: