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Diffstat (limited to 'arch/arm64/kernel/head.S')
| -rw-r--r-- | arch/arm64/kernel/head.S | 709 |
1 files changed, 709 insertions, 0 deletions
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S new file mode 100644 index 00000000000..a2c1195abb7 --- /dev/null +++ b/arch/arm64/kernel/head.S @@ -0,0 +1,709 @@ +/* + * Low-level CPU initialisation + * Based on arch/arm/kernel/head.S + * + * Copyright (C) 1994-2002 Russell King + * Copyright (C) 2003-2012 ARM Ltd. + * Authors: Catalin Marinas <catalin.marinas@arm.com> + * Will Deacon <will.deacon@arm.com> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program. If not, see <http://www.gnu.org/licenses/>. + */ + +#include <linux/linkage.h> +#include <linux/init.h> + +#include <asm/assembler.h> +#include <asm/ptrace.h> +#include <asm/asm-offsets.h> +#include <asm/cache.h> +#include <asm/cputype.h> +#include <asm/memory.h> +#include <asm/thread_info.h> +#include <asm/pgtable-hwdef.h> +#include <asm/pgtable.h> +#include <asm/page.h> +#include <asm/virt.h> + +/* + * swapper_pg_dir is the virtual address of the initial page table. We place + * the page tables 3 * PAGE_SIZE below KERNEL_RAM_VADDR. The idmap_pg_dir has + * 2 pages and is placed below swapper_pg_dir. + */ +#define KERNEL_RAM_VADDR (PAGE_OFFSET + TEXT_OFFSET) + +#if (KERNEL_RAM_VADDR & 0xfffff) != 0x80000 +#error KERNEL_RAM_VADDR must start at 0xXXX80000 +#endif + +#define SWAPPER_DIR_SIZE (3 * PAGE_SIZE) +#define IDMAP_DIR_SIZE (2 * PAGE_SIZE) + + .globl swapper_pg_dir + .equ swapper_pg_dir, KERNEL_RAM_VADDR - SWAPPER_DIR_SIZE + + .globl idmap_pg_dir + .equ idmap_pg_dir, swapper_pg_dir - IDMAP_DIR_SIZE + + .macro pgtbl, ttb0, ttb1, phys + add \ttb1, \phys, #TEXT_OFFSET - SWAPPER_DIR_SIZE + sub \ttb0, \ttb1, #IDMAP_DIR_SIZE + .endm + +#ifdef CONFIG_ARM64_64K_PAGES +#define BLOCK_SHIFT PAGE_SHIFT +#define BLOCK_SIZE PAGE_SIZE +#else +#define BLOCK_SHIFT SECTION_SHIFT +#define BLOCK_SIZE SECTION_SIZE +#endif + +#define KERNEL_START KERNEL_RAM_VADDR +#define KERNEL_END _end + +/* + * Initial memory map attributes. + */ +#ifndef CONFIG_SMP +#define PTE_FLAGS PTE_TYPE_PAGE | PTE_AF +#define PMD_FLAGS PMD_TYPE_SECT | PMD_SECT_AF +#else +#define PTE_FLAGS PTE_TYPE_PAGE | PTE_AF | PTE_SHARED +#define PMD_FLAGS PMD_TYPE_SECT | PMD_SECT_AF | PMD_SECT_S +#endif + +#ifdef CONFIG_ARM64_64K_PAGES +#define MM_MMUFLAGS PTE_ATTRINDX(MT_NORMAL) | PTE_FLAGS +#else +#define MM_MMUFLAGS PMD_ATTRINDX(MT_NORMAL) | PMD_FLAGS +#endif + +/* + * Kernel startup entry point. + * --------------------------- + * + * The requirements are: + * MMU = off, D-cache = off, I-cache = on or off, + * x0 = physical address to the FDT blob. + * + * This code is mostly position independent so you call this at + * __pa(PAGE_OFFSET + TEXT_OFFSET). + * + * Note that the callee-saved registers are used for storing variables + * that are useful before the MMU is enabled. The allocations are described + * in the entry routines. + */ + __HEAD + + /* + * DO NOT MODIFY. Image header expected by Linux boot-loaders. + */ +#ifdef CONFIG_EFI +efi_head: + /* + * This add instruction has no meaningful effect except that + * its opcode forms the magic "MZ" signature required by UEFI. + */ + add x13, x18, #0x16 + b stext +#else + b stext // branch to kernel start, magic + .long 0 // reserved +#endif + .quad TEXT_OFFSET // Image load offset from start of RAM + .quad 0 // reserved + .quad 0 // reserved + .quad 0 // reserved + .quad 0 // reserved + .quad 0 // reserved + .byte 0x41 // Magic number, "ARM\x64" + .byte 0x52 + .byte 0x4d + .byte 0x64 +#ifdef CONFIG_EFI + .long pe_header - efi_head // Offset to the PE header. +#else + .word 0 // reserved +#endif + +#ifdef CONFIG_EFI + .align 3 +pe_header: + .ascii "PE" + .short 0 +coff_header: + .short 0xaa64 // AArch64 + .short 2 // nr_sections + .long 0 // TimeDateStamp + .long 0 // PointerToSymbolTable + .long 1 // NumberOfSymbols + .short section_table - optional_header // SizeOfOptionalHeader + .short 0x206 // Characteristics. + // IMAGE_FILE_DEBUG_STRIPPED | + // IMAGE_FILE_EXECUTABLE_IMAGE | + // IMAGE_FILE_LINE_NUMS_STRIPPED +optional_header: + .short 0x20b // PE32+ format + .byte 0x02 // MajorLinkerVersion + .byte 0x14 // MinorLinkerVersion + .long _edata - stext // SizeOfCode + .long 0 // SizeOfInitializedData + .long 0 // SizeOfUninitializedData + .long efi_stub_entry - efi_head // AddressOfEntryPoint + .long stext - efi_head // BaseOfCode + +extra_header_fields: + .quad 0 // ImageBase + .long 0x20 // SectionAlignment + .long 0x8 // FileAlignment + .short 0 // MajorOperatingSystemVersion + .short 0 // MinorOperatingSystemVersion + .short 0 // MajorImageVersion + .short 0 // MinorImageVersion + .short 0 // MajorSubsystemVersion + .short 0 // MinorSubsystemVersion + .long 0 // Win32VersionValue + + .long _edata - efi_head // SizeOfImage + + // Everything before the kernel image is considered part of the header + .long stext - efi_head // SizeOfHeaders + .long 0 // CheckSum + .short 0xa // Subsystem (EFI application) + .short 0 // DllCharacteristics + .quad 0 // SizeOfStackReserve + .quad 0 // SizeOfStackCommit + .quad 0 // SizeOfHeapReserve + .quad 0 // SizeOfHeapCommit + .long 0 // LoaderFlags + .long 0x6 // NumberOfRvaAndSizes + + .quad 0 // ExportTable + .quad 0 // ImportTable + .quad 0 // ResourceTable + .quad 0 // ExceptionTable + .quad 0 // CertificationTable + .quad 0 // BaseRelocationTable + + // Section table +section_table: + + /* + * The EFI application loader requires a relocation section + * because EFI applications must be relocatable. This is a + * dummy section as far as we are concerned. + */ + .ascii ".reloc" + .byte 0 + .byte 0 // end of 0 padding of section name + .long 0 + .long 0 + .long 0 // SizeOfRawData + .long 0 // PointerToRawData + .long 0 // PointerToRelocations + .long 0 // PointerToLineNumbers + .short 0 // NumberOfRelocations + .short 0 // NumberOfLineNumbers + .long 0x42100040 // Characteristics (section flags) + + + .ascii ".text" + .byte 0 + .byte 0 + .byte 0 // end of 0 padding of section name + .long _edata - stext // VirtualSize + .long stext - efi_head // VirtualAddress + .long _edata - stext // SizeOfRawData + .long stext - efi_head // PointerToRawData + + .long 0 // PointerToRelocations (0 for executables) + .long 0 // PointerToLineNumbers (0 for executables) + .short 0 // NumberOfRelocations (0 for executables) + .short 0 // NumberOfLineNumbers (0 for executables) + .long 0xe0500020 // Characteristics (section flags) + .align 5 +#endif + +ENTRY(stext) + mov x21, x0 // x21=FDT + bl el2_setup // Drop to EL1, w20=cpu_boot_mode + bl __calc_phys_offset // x24=PHYS_OFFSET, x28=PHYS_OFFSET-PAGE_OFFSET + bl set_cpu_boot_mode_flag + mrs x22, midr_el1 // x22=cpuid + mov x0, x22 + bl lookup_processor_type + mov x23, x0 // x23=current cpu_table + cbz x23, __error_p // invalid processor (x23=0)? + bl __vet_fdt + bl __create_page_tables // x25=TTBR0, x26=TTBR1 + /* + * The following calls CPU specific code in a position independent + * manner. See arch/arm64/mm/proc.S for details. x23 = base of + * cpu_info structure selected by lookup_processor_type above. + * On return, the CPU will be ready for the MMU to be turned on and + * the TCR will have been set. + */ + ldr x27, __switch_data // address to jump to after + // MMU has been enabled + adr lr, __enable_mmu // return (PIC) address + ldr x12, [x23, #CPU_INFO_SETUP] + add x12, x12, x28 // __virt_to_phys + br x12 // initialise processor +ENDPROC(stext) + +/* + * If we're fortunate enough to boot at EL2, ensure that the world is + * sane before dropping to EL1. + * + * Returns either BOOT_CPU_MODE_EL1 or BOOT_CPU_MODE_EL2 in x20 if + * booted in EL1 or EL2 respectively. + */ +ENTRY(el2_setup) + mrs x0, CurrentEL + cmp x0, #CurrentEL_EL2 + b.ne 1f + mrs x0, sctlr_el2 +CPU_BE( orr x0, x0, #(1 << 25) ) // Set the EE bit for EL2 +CPU_LE( bic x0, x0, #(1 << 25) ) // Clear the EE bit for EL2 + msr sctlr_el2, x0 + b 2f +1: mrs x0, sctlr_el1 +CPU_BE( orr x0, x0, #(3 << 24) ) // Set the EE and E0E bits for EL1 +CPU_LE( bic x0, x0, #(3 << 24) ) // Clear the EE and E0E bits for EL1 + msr sctlr_el1, x0 + mov w20, #BOOT_CPU_MODE_EL1 // This cpu booted in EL1 + isb + ret + + /* Hyp configuration. */ +2: mov x0, #(1 << 31) // 64-bit EL1 + msr hcr_el2, x0 + + /* Generic timers. */ + mrs x0, cnthctl_el2 + orr x0, x0, #3 // Enable EL1 physical timers + msr cnthctl_el2, x0 + msr cntvoff_el2, xzr // Clear virtual offset + + /* Populate ID registers. */ + mrs x0, midr_el1 + mrs x1, mpidr_el1 + msr vpidr_el2, x0 + msr vmpidr_el2, x1 + + /* sctlr_el1 */ + mov x0, #0x0800 // Set/clear RES{1,0} bits +CPU_BE( movk x0, #0x33d0, lsl #16 ) // Set EE and E0E on BE systems +CPU_LE( movk x0, #0x30d0, lsl #16 ) // Clear EE and E0E on LE systems + msr sctlr_el1, x0 + + /* Coprocessor traps. */ + mov x0, #0x33ff + msr cptr_el2, x0 // Disable copro. traps to EL2 + +#ifdef CONFIG_COMPAT + msr hstr_el2, xzr // Disable CP15 traps to EL2 +#endif + + /* Stage-2 translation */ + msr vttbr_el2, xzr + + /* Hypervisor stub */ + adr x0, __hyp_stub_vectors + msr vbar_el2, x0 + + /* spsr */ + mov x0, #(PSR_F_BIT | PSR_I_BIT | PSR_A_BIT | PSR_D_BIT |\ + PSR_MODE_EL1h) + msr spsr_el2, x0 + msr elr_el2, lr + mov w20, #BOOT_CPU_MODE_EL2 // This CPU booted in EL2 + eret +ENDPROC(el2_setup) + +/* + * Sets the __boot_cpu_mode flag depending on the CPU boot mode passed + * in x20. See arch/arm64/include/asm/virt.h for more info. + */ +ENTRY(set_cpu_boot_mode_flag) + ldr x1, =__boot_cpu_mode // Compute __boot_cpu_mode + add x1, x1, x28 + cmp w20, #BOOT_CPU_MODE_EL2 + b.ne 1f + add x1, x1, #4 +1: str w20, [x1] // This CPU has booted in EL1 + dmb sy + dc ivac, x1 // Invalidate potentially stale cache line + ret +ENDPROC(set_cpu_boot_mode_flag) + +/* + * We need to find out the CPU boot mode long after boot, so we need to + * store it in a writable variable. + * + * This is not in .bss, because we set it sufficiently early that the boot-time + * zeroing of .bss would clobber it. + */ + .pushsection .data..cacheline_aligned +ENTRY(__boot_cpu_mode) + .align L1_CACHE_SHIFT + .long BOOT_CPU_MODE_EL2 + .long 0 + .popsection + + .align 3 +2: .quad . + .quad PAGE_OFFSET + +#ifdef CONFIG_SMP + .align 3 +1: .quad . + .quad secondary_holding_pen_release + + /* + * This provides a "holding pen" for platforms to hold all secondary + * cores are held until we're ready for them to initialise. + */ +ENTRY(secondary_holding_pen) + bl el2_setup // Drop to EL1, w20=cpu_boot_mode + bl __calc_phys_offset // x24=PHYS_OFFSET, x28=PHYS_OFFSET-PAGE_OFFSET + bl set_cpu_boot_mode_flag + mrs x0, mpidr_el1 + ldr x1, =MPIDR_HWID_BITMASK + and x0, x0, x1 + adr x1, 1b + ldp x2, x3, [x1] + sub x1, x1, x2 + add x3, x3, x1 +pen: ldr x4, [x3] + cmp x4, x0 + b.eq secondary_startup + wfe + b pen +ENDPROC(secondary_holding_pen) + + /* + * Secondary entry point that jumps straight into the kernel. Only to + * be used where CPUs are brought online dynamically by the kernel. + */ +ENTRY(secondary_entry) + bl el2_setup // Drop to EL1 + bl __calc_phys_offset // x24=PHYS_OFFSET, x28=PHYS_OFFSET-PAGE_OFFSET + bl set_cpu_boot_mode_flag + b secondary_startup +ENDPROC(secondary_entry) + +ENTRY(secondary_startup) + /* + * Common entry point for secondary CPUs. + */ + mrs x22, midr_el1 // x22=cpuid + mov x0, x22 + bl lookup_processor_type + mov x23, x0 // x23=current cpu_table + cbz x23, __error_p // invalid processor (x23=0)? + + pgtbl x25, x26, x24 // x25=TTBR0, x26=TTBR1 + ldr x12, [x23, #CPU_INFO_SETUP] + add x12, x12, x28 // __virt_to_phys + blr x12 // initialise processor + + ldr x21, =secondary_data + ldr x27, =__secondary_switched // address to jump to after enabling the MMU + b __enable_mmu +ENDPROC(secondary_startup) + +ENTRY(__secondary_switched) + ldr x0, [x21] // get secondary_data.stack + mov sp, x0 + mov x29, #0 + b secondary_start_kernel +ENDPROC(__secondary_switched) +#endif /* CONFIG_SMP */ + +/* + * Setup common bits before finally enabling the MMU. Essentially this is just + * loading the page table pointer and vector base registers. + * + * On entry to this code, x0 must contain the SCTLR_EL1 value for turning on + * the MMU. + */ +__enable_mmu: + ldr x5, =vectors + msr vbar_el1, x5 + msr ttbr0_el1, x25 // load TTBR0 + msr ttbr1_el1, x26 // load TTBR1 + isb + b __turn_mmu_on +ENDPROC(__enable_mmu) + +/* + * Enable the MMU. This completely changes the structure of the visible memory + * space. You will not be able to trace execution through this. + * + * x0 = system control register + * x27 = *virtual* address to jump to upon completion + * + * other registers depend on the function called upon completion + */ + .align 6 +__turn_mmu_on: + msr sctlr_el1, x0 + isb + br x27 +ENDPROC(__turn_mmu_on) + +/* + * Calculate the start of physical memory. + */ +__calc_phys_offset: + adr x0, 1f + ldp x1, x2, [x0] + sub x28, x0, x1 // x28 = PHYS_OFFSET - PAGE_OFFSET + add x24, x2, x28 // x24 = PHYS_OFFSET + ret +ENDPROC(__calc_phys_offset) + + .align 3 +1: .quad . + .quad PAGE_OFFSET + +/* + * Macro to populate the PGD for the corresponding block entry in the next + * level (tbl) for the given virtual address. + * + * Preserves: pgd, tbl, virt + * Corrupts: tmp1, tmp2 + */ + .macro create_pgd_entry, pgd, tbl, virt, tmp1, tmp2 + lsr \tmp1, \virt, #PGDIR_SHIFT + and \tmp1, \tmp1, #PTRS_PER_PGD - 1 // PGD index + orr \tmp2, \tbl, #3 // PGD entry table type + str \tmp2, [\pgd, \tmp1, lsl #3] + .endm + +/* + * Macro to populate block entries in the page table for the start..end + * virtual range (inclusive). + * + * Preserves: tbl, flags + * Corrupts: phys, start, end, pstate + */ + .macro create_block_map, tbl, flags, phys, start, end + lsr \phys, \phys, #BLOCK_SHIFT + lsr \start, \start, #BLOCK_SHIFT + and \start, \start, #PTRS_PER_PTE - 1 // table index + orr \phys, \flags, \phys, lsl #BLOCK_SHIFT // table entry + lsr \end, \end, #BLOCK_SHIFT + and \end, \end, #PTRS_PER_PTE - 1 // table end index +9999: str \phys, [\tbl, \start, lsl #3] // store the entry + add \start, \start, #1 // next entry + add \phys, \phys, #BLOCK_SIZE // next block + cmp \start, \end + b.ls 9999b + .endm + +/* + * Setup the initial page tables. We only setup the barest amount which is + * required to get the kernel running. The following sections are required: + * - identity mapping to enable the MMU (low address, TTBR0) + * - first few MB of the kernel linear mapping to jump to once the MMU has + * been enabled, including the FDT blob (TTBR1) + * - pgd entry for fixed mappings (TTBR1) + */ +__create_page_tables: + pgtbl x25, x26, x24 // idmap_pg_dir and swapper_pg_dir addresses + mov x27, lr + + /* + * Invalidate the idmap and swapper page tables to avoid potential + * dirty cache lines being evicted. + */ + mov x0, x25 + add x1, x26, #SWAPPER_DIR_SIZE + bl __inval_cache_range + + /* + * Clear the idmap and swapper page tables. + */ + mov x0, x25 + add x6, x26, #SWAPPER_DIR_SIZE +1: stp xzr, xzr, [x0], #16 + stp xzr, xzr, [x0], #16 + stp xzr, xzr, [x0], #16 + stp xzr, xzr, [x0], #16 + cmp x0, x6 + b.lo 1b + + ldr x7, =MM_MMUFLAGS + + /* + * Create the identity mapping. + */ + add x0, x25, #PAGE_SIZE // section table address + ldr x3, =KERNEL_START + add x3, x3, x28 // __pa(KERNEL_START) + create_pgd_entry x25, x0, x3, x5, x6 + ldr x6, =KERNEL_END + mov x5, x3 // __pa(KERNEL_START) + add x6, x6, x28 // __pa(KERNEL_END) + create_block_map x0, x7, x3, x5, x6 + + /* + * Map the kernel image (starting with PHYS_OFFSET). + */ + add x0, x26, #PAGE_SIZE // section table address + mov x5, #PAGE_OFFSET + create_pgd_entry x26, x0, x5, x3, x6 + ldr x6, =KERNEL_END + mov x3, x24 // phys offset + create_block_map x0, x7, x3, x5, x6 + + /* + * Map the FDT blob (maximum 2MB; must be within 512MB of + * PHYS_OFFSET). + */ + mov x3, x21 // FDT phys address + and x3, x3, #~((1 << 21) - 1) // 2MB aligned + mov x6, #PAGE_OFFSET + sub x5, x3, x24 // subtract PHYS_OFFSET + tst x5, #~((1 << 29) - 1) // within 512MB? + csel x21, xzr, x21, ne // zero the FDT pointer + b.ne 1f + add x5, x5, x6 // __va(FDT blob) + add x6, x5, #1 << 21 // 2MB for the FDT blob + sub x6, x6, #1 // inclusive range + create_block_map x0, x7, x3, x5, x6 +1: + /* + * Create the pgd entry for the fixed mappings. + */ + ldr x5, =FIXADDR_TOP // Fixed mapping virtual address + add x0, x26, #2 * PAGE_SIZE // section table address + create_pgd_entry x26, x0, x5, x6, x7 + + /* + * Since the page tables have been populated with non-cacheable + * accesses (MMU disabled), invalidate the idmap and swapper page + * tables again to remove any speculatively loaded cache lines. + */ + mov x0, x25 + add x1, x26, #SWAPPER_DIR_SIZE + bl __inval_cache_range + + mov lr, x27 + ret +ENDPROC(__create_page_tables) + .ltorg + + .align 3 + .type __switch_data, %object +__switch_data: + .quad __mmap_switched + .quad __bss_start // x6 + .quad _end // x7 + .quad processor_id // x4 + .quad __fdt_pointer // x5 + .quad memstart_addr // x6 + .quad init_thread_union + THREAD_START_SP // sp + +/* + * The following fragment of code is executed with the MMU on in MMU mode, and + * uses absolute addresses; this is not position independent. + */ +__mmap_switched: + adr x3, __switch_data + 8 + + ldp x6, x7, [x3], #16 +1: cmp x6, x7 + b.hs 2f + str xzr, [x6], #8 // Clear BSS + b 1b +2: + ldp x4, x5, [x3], #16 + ldr x6, [x3], #8 + ldr x16, [x3] + mov sp, x16 + str x22, [x4] // Save processor ID + str x21, [x5] // Save FDT pointer + str x24, [x6] // Save PHYS_OFFSET + mov x29, #0 + b start_kernel +ENDPROC(__mmap_switched) + +/* + * Exception handling. Something went wrong and we can't proceed. We ought to + * tell the user, but since we don't have any guarantee that we're even + * running on the right architecture, we do virtually nothing. + */ +__error_p: +ENDPROC(__error_p) + +__error: +1: nop + b 1b +ENDPROC(__error) + +/* + * This function gets the processor ID in w0 and searches the cpu_table[] for + * a match. It returns a pointer to the struct cpu_info it found. The + * cpu_table[] must end with an empty (all zeros) structure. + * + * This routine can be called via C code and it needs to work with the MMU + * both disabled and enabled (the offset is calculated automatically). + */ +ENTRY(lookup_processor_type) + adr x1, __lookup_processor_type_data + ldp x2, x3, [x1] + sub x1, x1, x2 // get offset between VA and PA + add x3, x3, x1 // convert VA to PA +1: + ldp w5, w6, [x3] // load cpu_id_val and cpu_id_mask + cbz w5, 2f // end of list? + and w6, w6, w0 + cmp w5, w6 + b.eq 3f + add x3, x3, #CPU_INFO_SZ + 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) |