x86, realmode: Move SMP trampoline to unified realmode code

Migrated SMP trampoline code to the real mode blob.
SMP trampoline code is not yet removed from
.x86_trampoline because it is needed by the wakeup
code.

[ hpa: always enable compiling startup_32_smp in head_32.S... it is
  only a few instructions which go into .init on UP builds, and it makes
  the rest of the code less #ifdef ugly. ]

Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@intel.com>
Link: http://lkml.kernel.org/r/1336501366-28617-6-git-send-email-jarkko.sakkinen@intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

1 files changed, 86 insertions, 0 deletions

diff --git a/arch/x86/realmode/rm/trampoline_32.S b/arch/x86/realmode/rm/trampoline_32.S
new file mode 100644
index 000000000000..18cb7fc9fad4
--- /dev/null
+++ b/arch/x86/realmode/rm/trampoline_32.S
@@ -0,0 +1,86 @@
+/*
+ *
+ *      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_data, 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.
+ *
+ *      The structure real_mode_header includes entries that need
+ *      to be set up before executing this code:
+ *
+ *      startup_32_smp
+ *      boot_gdt
+ */
+
+#include <linux/linkage.h>
+#include <linux/init.h>
+#include <asm/segment.h>
+#include <asm/page_types.h>
+
+        .text
+        .code16
+        .globl trampoline_data
+
+        .balign PAGE_SIZE
+trampoline_data:
+        wbinvd                  # Needed for NUMA-Q should be harmless for others
+
+        .byte   0xea            # ljmpw
+        .word   1f              # Offset
+        .word   real_mode_seg   # Segment
+1:
+        mov     %cs, %ax        # Code and data in the same place
+        mov     %ax, %ds
+
+        cli                     # We should be safe anyway
+
+        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   boot_idt_descr          # load idt with 0, 0
+        lgdtl   boot_gdt_descr          # 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   *(startup_32_smp)
+
+        .data
+        .globl startup_32_smp, boot_gdt, trampoline_status
+
+boot_gdt_descr:
+        .word   __BOOT_DS + 7                   # gdt limit
+boot_gdt:
+        .long   0                               # gdt base
+
+boot_idt_descr:
+        .word   0                               # idt limit = 0
+        .long   0                               # idt base = 0L
+
+trampoline_status:
+        .long   0
+
+startup_32_smp:
+        .long   0x00000000
+        .word   __BOOT_CS, 0