1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * 4 * Trampoline.S Derived from Setup.S by Linus Torvalds 5 * 6 * 4 Jan 1997 Michael Chastain: changed to gnu as. 7 * 8 * This is only used for booting secondary CPUs in SMP machine 9 * 10 * Entry: CS:IP point to the start of our code, we are 11 * in real mode with no stack, but the rest of the 12 * trampoline page to make our stack and everything else 13 * is a mystery. 14 * 15 * We jump into arch/x86/kernel/head_32.S. 16 * 17 * On entry to trampoline_start, the processor is in real mode 18 * with 16-bit addressing and 16-bit data. CS has some value 19 * and IP is zero. Thus, we load CS to the physical segment 20 * of the real mode code before doing anything further. 21 */ 22 23 #include <linux/linkage.h> 24 #include <asm/segment.h> 25 #include <asm/page_types.h> 26 #include "realmode.h" 27 28 .text 29 .code16 30 31 .balign PAGE_SIZE 32 SYM_CODE_START(trampoline_start) 33 wbinvd # Needed for NUMA-Q should be harmless for others 34 35 LJMPW_RM(1f) 36 1: 37 mov %cs, %ax # Code and data in the same place 38 mov %ax, %ds 39 40 cli # We should be safe anyway 41 42 movl tr_start, %eax # where we need to go 43 44 /* 45 * GDT tables in non default location kernel can be beyond 16MB and 46 * lgdt will not be able to load the address as in real mode default 47 * operand size is 16bit. Use lgdtl instead to force operand size 48 * to 32 bit. 49 */ 50 lidtl tr_idt # load idt with 0, 0 51 lgdtl tr_gdt # load gdt with whatever is appropriate 52 53 movw $1, %dx # protected mode (PE) bit 54 lmsw %dx # into protected mode 55 56 ljmpl $__BOOT_CS, $pa_startup_32 57 SYM_CODE_END(trampoline_start) 58 59 .section ".text32","ax" 60 .code32 61 SYM_CODE_START(startup_32) # note: also used from wakeup_asm.S 62 jmp *%eax 63 SYM_CODE_END(startup_32) 64 65 .bss 66 .balign 8 67 SYM_DATA_START(trampoline_header) 68 SYM_DATA_LOCAL(tr_start, .space 4) 69 SYM_DATA_LOCAL(tr_gdt_pad, .space 2) 70 SYM_DATA_LOCAL(tr_gdt, .space 6) 71 SYM_DATA_END(trampoline_header) 72 73 #include "trampoline_common.S" 74