Diffstat (limited to 'arch/x86/realmode/rm/trampoline_32.S')
1 files changed, 74 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
@@ -0,0 +1,74 @@
+ * 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.
+ .balign PAGE_SIZE
+ 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 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"
+ENTRY(startup_32) # note: also used from wakeup_asm.S
+ jmp *%eax
+ .balign 8
+ tr_start: .space 4
+ tr_gdt_pad: .space 2
+ tr_gdt: .space 6