9703d9d7f7
The patch adds the kernel booting and the initial setup code. Documentation/arm64/booting.txt describes the booting protocol on the AArch64 Linux kernel. This is subject to change following the work on boot standardisation, ACPI. Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Acked-by: Nicolas Pitre <nico@linaro.org> Acked-by: Tony Lindgren <tony@atomide.com> Acked-by: Olof Johansson <olof@lixom.net> Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com> Acked-by: Arnd Bergmann <arnd@arndb.de>
510 lines
13 KiB
ArmAsm
510 lines
13 KiB
ArmAsm
/*
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* Low-level CPU initialisation
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* Based on arch/arm/kernel/head.S
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*
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* Copyright (C) 1994-2002 Russell King
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* Copyright (C) 2003-2012 ARM Ltd.
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* Authors: Catalin Marinas <catalin.marinas@arm.com>
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* Will Deacon <will.deacon@arm.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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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/assembler.h>
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#include <asm/ptrace.h>
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#include <asm/asm-offsets.h>
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#include <asm/memory.h>
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#include <asm/thread_info.h>
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#include <asm/pgtable-hwdef.h>
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#include <asm/pgtable.h>
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#include <asm/page.h>
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/*
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* swapper_pg_dir is the virtual address of the initial page table. We place
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* the page tables 3 * PAGE_SIZE below KERNEL_RAM_VADDR. The idmap_pg_dir has
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* 2 pages and is placed below swapper_pg_dir.
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*/
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#define KERNEL_RAM_VADDR (PAGE_OFFSET + TEXT_OFFSET)
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#if (KERNEL_RAM_VADDR & 0xfffff) != 0x80000
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#error KERNEL_RAM_VADDR must start at 0xXXX80000
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#endif
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#define SWAPPER_DIR_SIZE (3 * PAGE_SIZE)
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#define IDMAP_DIR_SIZE (2 * PAGE_SIZE)
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.globl swapper_pg_dir
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.equ swapper_pg_dir, KERNEL_RAM_VADDR - SWAPPER_DIR_SIZE
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.globl idmap_pg_dir
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.equ idmap_pg_dir, swapper_pg_dir - IDMAP_DIR_SIZE
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.macro pgtbl, ttb0, ttb1, phys
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add \ttb1, \phys, #TEXT_OFFSET - SWAPPER_DIR_SIZE
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sub \ttb0, \ttb1, #IDMAP_DIR_SIZE
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.endm
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#ifdef CONFIG_ARM64_64K_PAGES
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#define BLOCK_SHIFT PAGE_SHIFT
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#define BLOCK_SIZE PAGE_SIZE
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#else
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#define BLOCK_SHIFT SECTION_SHIFT
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#define BLOCK_SIZE SECTION_SIZE
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#endif
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#define KERNEL_START KERNEL_RAM_VADDR
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#define KERNEL_END _end
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/*
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* Initial memory map attributes.
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*/
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#ifndef CONFIG_SMP
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#define PTE_FLAGS PTE_TYPE_PAGE | PTE_AF
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#define PMD_FLAGS PMD_TYPE_SECT | PMD_SECT_AF
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#else
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#define PTE_FLAGS PTE_TYPE_PAGE | PTE_AF | PTE_SHARED
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#define PMD_FLAGS PMD_TYPE_SECT | PMD_SECT_AF | PMD_SECT_S
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#endif
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#ifdef CONFIG_ARM64_64K_PAGES
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#define MM_MMUFLAGS PTE_ATTRINDX(MT_NORMAL) | PTE_FLAGS
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#define IO_MMUFLAGS PTE_ATTRINDX(MT_DEVICE_nGnRE) | PTE_XN | PTE_FLAGS
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#else
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#define MM_MMUFLAGS PMD_ATTRINDX(MT_NORMAL) | PMD_FLAGS
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#define IO_MMUFLAGS PMD_ATTRINDX(MT_DEVICE_nGnRE) | PMD_SECT_XN | PMD_FLAGS
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#endif
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/*
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* Kernel startup entry point.
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* ---------------------------
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*
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* The requirements are:
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* MMU = off, D-cache = off, I-cache = on or off,
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* x0 = physical address to the FDT blob.
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*
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* This code is mostly position independent so you call this at
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* __pa(PAGE_OFFSET + TEXT_OFFSET).
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*
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* Note that the callee-saved registers are used for storing variables
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* that are useful before the MMU is enabled. The allocations are described
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* in the entry routines.
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*/
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__HEAD
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/*
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* DO NOT MODIFY. Image header expected by Linux boot-loaders.
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*/
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b stext // branch to kernel start, magic
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.long 0 // reserved
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.quad TEXT_OFFSET // Image load offset from start of RAM
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.quad 0 // reserved
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.quad 0 // reserved
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ENTRY(stext)
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mov x21, x0 // x21=FDT
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bl el2_setup // Drop to EL1
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mrs x22, midr_el1 // x22=cpuid
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mov x0, x22
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bl lookup_processor_type
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mov x23, x0 // x23=current cpu_table
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cbz x23, __error_p // invalid processor (x23=0)?
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bl __calc_phys_offset // x24=PHYS_OFFSET, x28=PHYS_OFFSET-PAGE_OFFSET
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bl __vet_fdt
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bl __create_page_tables // x25=TTBR0, x26=TTBR1
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/*
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* The following calls CPU specific code in a position independent
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* manner. See arch/arm64/mm/proc.S for details. x23 = base of
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* cpu_info structure selected by lookup_processor_type above.
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* On return, the CPU will be ready for the MMU to be turned on and
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* the TCR will have been set.
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*/
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ldr x27, __switch_data // address to jump to after
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// MMU has been enabled
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adr lr, __enable_mmu // return (PIC) address
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ldr x12, [x23, #CPU_INFO_SETUP]
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add x12, x12, x28 // __virt_to_phys
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br x12 // initialise processor
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ENDPROC(stext)
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/*
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* If we're fortunate enough to boot at EL2, ensure that the world is
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* sane before dropping to EL1.
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*/
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ENTRY(el2_setup)
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mrs x0, CurrentEL
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cmp x0, #PSR_MODE_EL2t
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ccmp x0, #PSR_MODE_EL2h, #0x4, ne
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b.eq 1f
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ret
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/* Hyp configuration. */
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1: mov x0, #(1 << 31) // 64-bit EL1
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msr hcr_el2, x0
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/* Generic timers. */
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mrs x0, cnthctl_el2
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orr x0, x0, #3 // Enable EL1 physical timers
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msr cnthctl_el2, x0
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/* Populate ID registers. */
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mrs x0, midr_el1
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mrs x1, mpidr_el1
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msr vpidr_el2, x0
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msr vmpidr_el2, x1
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/* sctlr_el1 */
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mov x0, #0x0800 // Set/clear RES{1,0} bits
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movk x0, #0x30d0, lsl #16
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msr sctlr_el1, x0
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/* Coprocessor traps. */
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mov x0, #0x33ff
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msr cptr_el2, x0 // Disable copro. traps to EL2
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#ifdef CONFIG_COMPAT
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msr hstr_el2, xzr // Disable CP15 traps to EL2
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#endif
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/* spsr */
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mov x0, #(PSR_F_BIT | PSR_I_BIT | PSR_A_BIT | PSR_D_BIT |\
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PSR_MODE_EL1h)
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msr spsr_el2, x0
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msr elr_el2, lr
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eret
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ENDPROC(el2_setup)
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.align 3
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2: .quad .
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.quad PAGE_OFFSET
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#ifdef CONFIG_SMP
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.pushsection .smp.pen.text, "ax"
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.align 3
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1: .quad .
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.quad secondary_holding_pen_release
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/*
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* This provides a "holding pen" for platforms to hold all secondary
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* cores are held until we're ready for them to initialise.
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*/
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ENTRY(secondary_holding_pen)
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bl el2_setup // Drop to EL1
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mrs x0, mpidr_el1
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and x0, x0, #15 // CPU number
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adr x1, 1b
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ldp x2, x3, [x1]
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sub x1, x1, x2
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add x3, x3, x1
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pen: ldr x4, [x3]
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cmp x4, x0
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b.eq secondary_startup
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wfe
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b pen
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ENDPROC(secondary_holding_pen)
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.popsection
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ENTRY(secondary_startup)
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/*
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* Common entry point for secondary CPUs.
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*/
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mrs x22, midr_el1 // x22=cpuid
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mov x0, x22
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bl lookup_processor_type
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mov x23, x0 // x23=current cpu_table
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cbz x23, __error_p // invalid processor (x23=0)?
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bl __calc_phys_offset // x24=phys offset
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pgtbl x25, x26, x24 // x25=TTBR0, x26=TTBR1
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ldr x12, [x23, #CPU_INFO_SETUP]
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add x12, x12, x28 // __virt_to_phys
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blr x12 // initialise processor
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ldr x21, =secondary_data
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ldr x27, =__secondary_switched // address to jump to after enabling the MMU
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b __enable_mmu
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ENDPROC(secondary_startup)
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ENTRY(__secondary_switched)
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ldr x0, [x21] // get secondary_data.stack
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mov sp, x0
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mov x29, #0
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b secondary_start_kernel
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ENDPROC(__secondary_switched)
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#endif /* CONFIG_SMP */
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/*
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* Setup common bits before finally enabling the MMU. Essentially this is just
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* loading the page table pointer and vector base registers.
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*
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* On entry to this code, x0 must contain the SCTLR_EL1 value for turning on
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* the MMU.
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*/
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__enable_mmu:
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ldr x5, =vectors
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msr vbar_el1, x5
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msr ttbr0_el1, x25 // load TTBR0
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msr ttbr1_el1, x26 // load TTBR1
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isb
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b __turn_mmu_on
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ENDPROC(__enable_mmu)
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/*
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* Enable the MMU. This completely changes the structure of the visible memory
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* space. You will not be able to trace execution through this.
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*
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* x0 = system control register
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* x27 = *virtual* address to jump to upon completion
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*
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* other registers depend on the function called upon completion
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*/
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.align 6
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__turn_mmu_on:
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msr sctlr_el1, x0
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isb
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br x27
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ENDPROC(__turn_mmu_on)
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/*
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* Calculate the start of physical memory.
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*/
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__calc_phys_offset:
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adr x0, 1f
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ldp x1, x2, [x0]
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sub x28, x0, x1 // x28 = PHYS_OFFSET - PAGE_OFFSET
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add x24, x2, x28 // x24 = PHYS_OFFSET
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ret
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ENDPROC(__calc_phys_offset)
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.align 3
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1: .quad .
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.quad PAGE_OFFSET
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/*
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* Macro to populate the PGD for the corresponding block entry in the next
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* level (tbl) for the given virtual address.
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*
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* Preserves: pgd, tbl, virt
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* Corrupts: tmp1, tmp2
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*/
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.macro create_pgd_entry, pgd, tbl, virt, tmp1, tmp2
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lsr \tmp1, \virt, #PGDIR_SHIFT
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and \tmp1, \tmp1, #PTRS_PER_PGD - 1 // PGD index
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orr \tmp2, \tbl, #3 // PGD entry table type
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str \tmp2, [\pgd, \tmp1, lsl #3]
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.endm
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/*
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* Macro to populate block entries in the page table for the start..end
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* virtual range (inclusive).
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*
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* Preserves: tbl, flags
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* Corrupts: phys, start, end, pstate
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*/
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.macro create_block_map, tbl, flags, phys, start, end, idmap=0
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lsr \phys, \phys, #BLOCK_SHIFT
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.if \idmap
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and \start, \phys, #PTRS_PER_PTE - 1 // table index
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.else
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lsr \start, \start, #BLOCK_SHIFT
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and \start, \start, #PTRS_PER_PTE - 1 // table index
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.endif
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orr \phys, \flags, \phys, lsl #BLOCK_SHIFT // table entry
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.ifnc \start,\end
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lsr \end, \end, #BLOCK_SHIFT
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and \end, \end, #PTRS_PER_PTE - 1 // table end index
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.endif
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9999: str \phys, [\tbl, \start, lsl #3] // store the entry
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.ifnc \start,\end
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add \start, \start, #1 // next entry
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add \phys, \phys, #BLOCK_SIZE // next block
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cmp \start, \end
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b.ls 9999b
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.endif
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.endm
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/*
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* Setup the initial page tables. We only setup the barest amount which is
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* required to get the kernel running. The following sections are required:
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* - identity mapping to enable the MMU (low address, TTBR0)
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* - first few MB of the kernel linear mapping to jump to once the MMU has
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* been enabled, including the FDT blob (TTBR1)
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*/
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__create_page_tables:
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pgtbl x25, x26, x24 // idmap_pg_dir and swapper_pg_dir addresses
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/*
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* Clear the idmap and swapper page tables.
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*/
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mov x0, x25
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add x6, x26, #SWAPPER_DIR_SIZE
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1: stp xzr, xzr, [x0], #16
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stp xzr, xzr, [x0], #16
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stp xzr, xzr, [x0], #16
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stp xzr, xzr, [x0], #16
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cmp x0, x6
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b.lo 1b
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ldr x7, =MM_MMUFLAGS
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/*
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* Create the identity mapping.
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*/
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add x0, x25, #PAGE_SIZE // section table address
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adr x3, __turn_mmu_on // virtual/physical address
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create_pgd_entry x25, x0, x3, x5, x6
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create_block_map x0, x7, x3, x5, x5, idmap=1
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/*
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* Map the kernel image (starting with PHYS_OFFSET).
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*/
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add x0, x26, #PAGE_SIZE // section table address
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mov x5, #PAGE_OFFSET
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create_pgd_entry x26, x0, x5, x3, x6
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ldr x6, =KERNEL_END - 1
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mov x3, x24 // phys offset
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create_block_map x0, x7, x3, x5, x6
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/*
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* Map the FDT blob (maximum 2MB; must be within 512MB of
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* PHYS_OFFSET).
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*/
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mov x3, x21 // FDT phys address
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and x3, x3, #~((1 << 21) - 1) // 2MB aligned
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mov x6, #PAGE_OFFSET
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sub x5, x3, x24 // subtract PHYS_OFFSET
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tst x5, #~((1 << 29) - 1) // within 512MB?
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csel x21, xzr, x21, ne // zero the FDT pointer
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b.ne 1f
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add x5, x5, x6 // __va(FDT blob)
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add x6, x5, #1 << 21 // 2MB for the FDT blob
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sub x6, x6, #1 // inclusive range
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create_block_map x0, x7, x3, x5, x6
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1:
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ret
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ENDPROC(__create_page_tables)
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.ltorg
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.align 3
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.type __switch_data, %object
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__switch_data:
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.quad __mmap_switched
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.quad __data_loc // x4
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.quad _data // x5
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.quad __bss_start // x6
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.quad _end // x7
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.quad processor_id // x4
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.quad __fdt_pointer // x5
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.quad memstart_addr // x6
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.quad init_thread_union + THREAD_START_SP // sp
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/*
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* The following fragment of code is executed with the MMU on in MMU mode, and
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* uses absolute addresses; this is not position independent.
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*/
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__mmap_switched:
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adr x3, __switch_data + 8
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ldp x4, x5, [x3], #16
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ldp x6, x7, [x3], #16
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cmp x4, x5 // Copy data segment if needed
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1: ccmp x5, x6, #4, ne
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b.eq 2f
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ldr x16, [x4], #8
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str x16, [x5], #8
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b 1b
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2:
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1: cmp x6, x7
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b.hs 2f
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str xzr, [x6], #8 // Clear BSS
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b 1b
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2:
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ldp x4, x5, [x3], #16
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ldr x6, [x3], #8
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ldr x16, [x3]
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mov sp, x16
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str x22, [x4] // Save processor ID
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str x21, [x5] // Save FDT pointer
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str x24, [x6] // Save PHYS_OFFSET
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mov x29, #0
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b start_kernel
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ENDPROC(__mmap_switched)
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/*
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* Exception handling. Something went wrong and we can't proceed. We ought to
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* tell the user, but since we don't have any guarantee that we're even
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* running on the right architecture, we do virtually nothing.
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*/
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__error_p:
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ENDPROC(__error_p)
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__error:
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1: nop
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b 1b
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ENDPROC(__error)
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/*
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* This function gets the processor ID in w0 and searches the cpu_table[] for
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* a match. It returns a pointer to the struct cpu_info it found. The
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* cpu_table[] must end with an empty (all zeros) structure.
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*
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* This routine can be called via C code and it needs to work with the MMU
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* both disabled and enabled (the offset is calculated automatically).
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*/
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ENTRY(lookup_processor_type)
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adr x1, __lookup_processor_type_data
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ldp x2, x3, [x1]
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sub x1, x1, x2 // get offset between VA and PA
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add x3, x3, x1 // convert VA to PA
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1:
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ldp w5, w6, [x3] // load cpu_id_val and cpu_id_mask
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cbz w5, 2f // end of list?
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and w6, w6, w0
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cmp w5, w6
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b.eq 3f
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add x3, x3, #CPU_INFO_SZ
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b 1b
|
|
2:
|
|
mov x3, #0 // unknown processor
|
|
3:
|
|
mov x0, x3
|
|
ret
|
|
ENDPROC(lookup_processor_type)
|
|
|
|
.align 3
|
|
.type __lookup_processor_type_data, %object
|
|
__lookup_processor_type_data:
|
|
.quad .
|
|
.quad cpu_table
|
|
.size __lookup_processor_type_data, . - __lookup_processor_type_data
|
|
|
|
/*
|
|
* Determine validity of the x21 FDT pointer.
|
|
* The dtb must be 8-byte aligned and live in the first 512M of memory.
|
|
*/
|
|
__vet_fdt:
|
|
tst x21, #0x7
|
|
b.ne 1f
|
|
cmp x21, x24
|
|
b.lt 1f
|
|
mov x0, #(1 << 29)
|
|
add x0, x0, x24
|
|
cmp x21, x0
|
|
b.ge 1f
|
|
ret
|
|
1:
|
|
mov x21, #0
|
|
ret
|
|
ENDPROC(__vet_fdt)
|