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