983d5dbdb2
o This fix was posted for i386 long back. Posting it for x86_64. http://marc.theaimsgroup.com/?l=linux-kernel&m=110380103229830&w=2 o This patch fixes the problem of secondary cpus boot up. This situation is faced when kernel is built for default locations like 16MB and onwards. In this configuration, only primary cpu (BP) comes and secondary cpus don't boot. o Problem occurs because in trampoline code, lgdt is not able to load the GDT as it happens to be situated beyond 16MB. This is due to the fact that cpu is still in real mode and default operand size is 16bit. o This patch uses lgdtl instead of lgdt to force operand size to 32 instead of 16. Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com> Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
71 lines
1.9 KiB
ArmAsm
71 lines
1.9 KiB
ArmAsm
/*
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*
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* Trampoline.S Derived from Setup.S by Linus Torvalds
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*
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* 4 Jan 1997 Michael Chastain: changed to gnu as.
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*
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* Entry: CS:IP point to the start of our code, we are
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* in real mode with no stack, but the rest of the
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* trampoline page to make our stack and everything else
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* is a mystery.
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*
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* In fact we don't actually need a stack so we don't
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* set one up.
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*
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* On entry to trampoline_data, the processor is in real mode
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* with 16-bit addressing and 16-bit data. CS has some value
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* and IP is zero. Thus, data addresses need to be absolute
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* (no relocation) and are taken with regard to r_base.
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*
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* If you work on this file, check the object module with objdump
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* --full-contents --reloc to make sure there are no relocation
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* entries. For the GDT entry we do hand relocation in smpboot.c
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* because of 64bit linker limitations.
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*/
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#include <linux/linkage.h>
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#include <asm/segment.h>
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#include <asm/page.h>
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.data
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.code16
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ENTRY(trampoline_data)
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r_base = .
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wbinvd
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mov %cs, %ax # Code and data in the same place
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mov %ax, %ds
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cli # We should be safe anyway
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movl $0xA5A5A5A5, trampoline_data - r_base
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# write marker for master knows we're running
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/*
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* GDT tables in non default location kernel can be beyond 16MB and
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* lgdt will not be able to load the address as in real mode default
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* operand size is 16bit. Use lgdtl instead to force operand size
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* to 32 bit.
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*/
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lidtl idt_48 - r_base # load idt with 0, 0
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lgdtl gdt_48 - r_base # load gdt with whatever is appropriate
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xor %ax, %ax
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inc %ax # protected mode (PE) bit
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lmsw %ax # into protected mode
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# flaush prefetch and jump to startup_32 in arch/x86_64/kernel/head.S
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ljmpl $__KERNEL32_CS, $(startup_32-__START_KERNEL_map)
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# Careful these need to be in the same 64K segment as the above;
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idt_48:
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.word 0 # idt limit = 0
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.word 0, 0 # idt base = 0L
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gdt_48:
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.short __KERNEL32_CS + 7 # gdt limit
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.long cpu_gdt_table-__START_KERNEL_map
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.globl trampoline_end
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trampoline_end:
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