| Kyle Swenson | 8d8f654 | 2021-03-15 11:02:55 -0600 | [diff] [blame^] | 1 | /* |
| 2 | * |
| 3 | * Trampoline.S Derived from Setup.S by Linus Torvalds |
| 4 | * |
| 5 | * 4 Jan 1997 Michael Chastain: changed to gnu as. |
| 6 | * |
| 7 | * This is only used for booting secondary CPUs in SMP machine |
| 8 | * |
| 9 | * Entry: CS:IP point to the start of our code, we are |
| 10 | * in real mode with no stack, but the rest of the |
| 11 | * trampoline page to make our stack and everything else |
| 12 | * is a mystery. |
| 13 | * |
| 14 | * We jump into arch/x86/kernel/head_32.S. |
| 15 | * |
| 16 | * On entry to trampoline_start, the processor is in real mode |
| 17 | * with 16-bit addressing and 16-bit data. CS has some value |
| 18 | * and IP is zero. Thus, we load CS to the physical segment |
| 19 | * of the real mode code before doing anything further. |
| 20 | */ |
| 21 | |
| 22 | #include <linux/linkage.h> |
| 23 | #include <asm/segment.h> |
| 24 | #include <asm/page_types.h> |
| 25 | #include "realmode.h" |
| 26 | |
| 27 | .text |
| 28 | .code16 |
| 29 | |
| 30 | .balign PAGE_SIZE |
| 31 | ENTRY(trampoline_start) |
| 32 | wbinvd # Needed for NUMA-Q should be harmless for others |
| 33 | |
| 34 | LJMPW_RM(1f) |
| 35 | 1: |
| 36 | mov %cs, %ax # Code and data in the same place |
| 37 | mov %ax, %ds |
| 38 | |
| 39 | cli # We should be safe anyway |
| 40 | |
| 41 | movl tr_start, %eax # where we need to go |
| 42 | |
| 43 | movl $0xA5A5A5A5, trampoline_status |
| 44 | # write marker for master knows we're running |
| 45 | |
| 46 | /* |
| 47 | * GDT tables in non default location kernel can be beyond 16MB and |
| 48 | * lgdt will not be able to load the address as in real mode default |
| 49 | * operand size is 16bit. Use lgdtl instead to force operand size |
| 50 | * to 32 bit. |
| 51 | */ |
| 52 | lidtl tr_idt # load idt with 0, 0 |
| 53 | lgdtl tr_gdt # load gdt with whatever is appropriate |
| 54 | |
| 55 | movw $1, %dx # protected mode (PE) bit |
| 56 | lmsw %dx # into protected mode |
| 57 | |
| 58 | ljmpl $__BOOT_CS, $pa_startup_32 |
| 59 | |
| 60 | .section ".text32","ax" |
| 61 | .code32 |
| 62 | ENTRY(startup_32) # note: also used from wakeup_asm.S |
| 63 | jmp *%eax |
| 64 | |
| 65 | .bss |
| 66 | .balign 8 |
| 67 | GLOBAL(trampoline_header) |
| 68 | tr_start: .space 4 |
| 69 | tr_gdt_pad: .space 2 |
| 70 | tr_gdt: .space 6 |
| 71 | END(trampoline_header) |
| 72 | |
| 73 | #include "trampoline_common.S" |