/* * 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 * Will Deacon * * 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 . */ #include #include #include #include #include #include #include #include #include #include #include #include /* * 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. */ b stext // branch to kernel start, magic .long 0 // reserved .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 .word 0 // reserved ENTRY(stext) mov x21, x0 // x21=FDT bl __calc_phys_offset // x24=PHYS_OFFSET, x28=PHYS_OFFSET-PAGE_OFFSET bl el2_setup // Drop to EL1 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. */ ENTRY(el2_setup) mrs x0, CurrentEL cmp x0, #PSR_MODE_EL2t ccmp x0, #PSR_MODE_EL2h, #0x4, ne ldr x0, =__boot_cpu_mode // Compute __boot_cpu_mode add x0, x0, x28 b.eq 1f str wzr, [x0] // Remember we don't have EL2... ret /* Hyp configuration. */ 1: ldr w1, =BOOT_CPU_MODE_EL2 str w1, [x0, #4] // This CPU has EL2 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 movk x0, #0x30d0, lsl #16 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 eret ENDPROC(el2_setup) /* * 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 ENTRY(__boot_cpu_mode) .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 __calc_phys_offset // x24=phys offset bl el2_setup // Drop to EL1 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 __calc_phys_offset // x2=phys offset bl el2_setup // Drop to EL1 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, idmap=0 lsr \phys, \phys, #BLOCK_SHIFT .if \idmap and \start, \phys, #PTRS_PER_PTE - 1 // table index .else lsr \start, \start, #BLOCK_SHIFT and \start, \start, #PTRS_PER_PTE - 1 // table index .endif orr \phys, \flags, \phys, lsl #BLOCK_SHIFT // table entry .ifnc \start,\end lsr \end, \end, #BLOCK_SHIFT and \end, \end, #PTRS_PER_PTE - 1 // table end index .endif 9999: str \phys, [\tbl, \start, lsl #3] // store the entry .ifnc \start,\end add \start, \start, #1 // next entry add \phys, \phys, #BLOCK_SIZE // next block cmp \start, \end b.ls 9999b .endif .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) * - UART mapping if CONFIG_EARLY_PRINTK is enabled (TTBR1) */ __create_page_tables: pgtbl x25, x26, x24 // idmap_pg_dir and swapper_pg_dir addresses /* * 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 adr x3, __turn_mmu_on // virtual/physical address create_pgd_entry x25, x0, x3, x5, x6 create_block_map x0, x7, x3, x5, x5, idmap=1 /* * 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 - 1 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: #ifdef CONFIG_EARLY_PRINTK /* * Create the pgd entry for the UART mapping. The full mapping is done * later based earlyprintk kernel parameter. */ ldr x5, =EARLYCON_IOBASE // UART virtual address add x0, x26, #2 * PAGE_SIZE // section table address create_pgd_entry x26, x0, x5, x6, x7 #endif ret ENDPROC(__create_page_tables) .ltorg .align 3 .type __switch_data, %object __switch_data: .quad __mmap_switched .quad __data_loc // x4 .quad _data // x5 .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 x4, x5, [x3], #16 ldp x6, x7, [x3], #16 cmp x4, x5 // Copy data segment if needed 1: ccmp x5, x6, #4, ne b.eq 2f ldr x16, [x4], #8 str x16, [x5], #8 b 1b 2: 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)