diff options
Diffstat (limited to 'arch/x86/realmode/rm/trampoline_32.S')
| -rw-r--r-- | arch/x86/realmode/rm/trampoline_32.S | 86 |
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 |