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https://github.com/torvalds/linux
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4822b7fc6d
Common infrastructure for low memory trampolines. This code installs the trampolines permanently in low memory very early. It also permits multiple pieces of code to be used for this purpose. This code also introduces a standard infrastructure for computing symbol addresses in the trampoline code. The only change to the actual SMP trampolines themselves is that the 64-bit trampoline has been made reusable -- the previous version would overwrite the code with a status variable; this moves the status variable to a separate location. Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> LKML-Reference: <4D5DFBE4.7090104@intel.com> Cc: Rafael J. Wysocki <rjw@sisk.pl> Cc: Matthieu Castet <castet.matthieu@free.fr> Cc: Stephen Rothwell <sfr@canb.auug.org.au>
84 lines
2.3 KiB
ArmAsm
84 lines
2.3 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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* This is only used for booting secondary CPUs in SMP machine
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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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* We jump into arch/x86/kernel/head_32.S.
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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
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* objdump --reloc to make sure there are no relocation
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* entries except for:
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*
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* TYPE VALUE
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* R_386_32 startup_32_smp
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* R_386_32 boot_gdt
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*/
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#include <linux/linkage.h>
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#include <linux/init.h>
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#include <asm/segment.h>
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#include <asm/page_types.h>
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#ifdef CONFIG_SMP
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.section ".x86_trampoline","a"
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.balign PAGE_SIZE
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.code16
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ENTRY(trampoline_data)
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r_base = .
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wbinvd # Needed for NUMA-Q should be harmless for others
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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_status - r_base
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# write marker for master knows we're running
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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 boot_idt_descr - r_base # load idt with 0, 0
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lgdtl boot_gdt_descr - 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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# flush prefetch and jump to startup_32_smp in arch/i386/kernel/head.S
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ljmpl $__BOOT_CS, $(startup_32_smp-__PAGE_OFFSET)
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# These need to be in the same 64K segment as the above;
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# hence we don't use the boot_gdt_descr defined in head.S
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boot_gdt_descr:
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.word __BOOT_DS + 7 # gdt limit
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.long boot_gdt - __PAGE_OFFSET # gdt base
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boot_idt_descr:
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.word 0 # idt limit = 0
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.long 0 # idt base = 0L
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ENTRY(trampoline_status)
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.long 0
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.globl trampoline_end
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trampoline_end:
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#endif /* CONFIG_SMP */
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