/* * 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 #include #include #include #include #include #include #include #include #define __PHYS_OFFSET (KERNEL_START - TEXT_OFFSET) #if (TEXT_OFFSET & 0xfff) != 0 #error TEXT_OFFSET must be at least 4KB aligned #elif (PAGE_OFFSET & 0x1fffff) != 0 #error PAGE_OFFSET must be at least 2MB aligned #elif TEXT_OFFSET > 0x1fffff #error TEXT_OFFSET must be less than 2MB #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 _head: /* * DO NOT MODIFY. Image header expected by Linux boot-loaders. */ #ifdef CONFIG_EFI /* * 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 le64sym _kernel_offset_le // Image load offset from start of RAM, little-endian le64sym _kernel_size_le // Effective size of kernel image, little-endian le64sym _kernel_flags_le // Informative flags, little-endian .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 - _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 _end - efi_header_end // SizeOfCode .long 0 // SizeOfInitializedData .long 0 // SizeOfUninitializedData .long __efistub_entry - _head // AddressOfEntryPoint .long efi_header_end - _head // BaseOfCode extra_header_fields: .quad 0 // ImageBase .long 0x1000 // SectionAlignment .long PECOFF_FILE_ALIGNMENT // FileAlignment .short 0 // MajorOperatingSystemVersion .short 0 // MinorOperatingSystemVersion .short 0 // MajorImageVersion .short 0 // MinorImageVersion .short 0 // MajorSubsystemVersion .short 0 // MinorSubsystemVersion .long 0 // Win32VersionValue .long _end - _head // SizeOfImage // Everything before the kernel image is considered part of the header .long efi_header_end - _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 _end - efi_header_end // VirtualSize .long efi_header_end - _head // VirtualAddress .long _edata - efi_header_end // SizeOfRawData .long efi_header_end - _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) /* * EFI will load .text onwards at the 4k section alignment * described in the PE/COFF header. To ensure that instruction * sequences using an adrp and a :lo12: immediate will function * correctly at this alignment, we must ensure that .text is * placed at a 4k boundary in the Image to begin with. */ .align 12 efi_header_end: #endif __INIT ENTRY(stext) bl preserve_boot_args bl el2_setup // Drop to EL1, w20=cpu_boot_mode adrp x24, __PHYS_OFFSET and x23, x24, MIN_KIMG_ALIGN - 1 // KASLR offset, defaults to 0 bl set_cpu_boot_mode_flag bl __create_page_tables /* * The following calls CPU setup code, see arch/arm64/mm/proc.S for * details. * On return, the CPU will be ready for the MMU to be turned on and * the TCR will have been set. */ bl __cpu_setup // initialise processor adr_l x27, __primary_switch // address to jump to after // MMU has been enabled b __enable_mmu ENDPROC(stext) /* * Preserve the arguments passed by the bootloader in x0 .. x3 */ preserve_boot_args: mov x21, x0 // x21=FDT adr_l x0, boot_args // record the contents of stp x21, x1, [x0] // x0 .. x3 at kernel entry stp x2, x3, [x0, #16] dmb sy // needed before dc ivac with // MMU off add x1, x0, #0x20 // 4 x 8 bytes b __inval_cache_range // tail call ENDPROC(preserve_boot_args) /* * Macro to create a table entry to the next page. * * tbl: page table address * virt: virtual address * shift: #imm page table shift * ptrs: #imm pointers per table page * * Preserves: virt * Corrupts: tmp1, tmp2 * Returns: tbl -> next level table page address */ .macro create_table_entry, tbl, virt, shift, ptrs, tmp1, tmp2 lsr \tmp1, \virt, #\shift and \tmp1, \tmp1, #\ptrs - 1 // table index add \tmp2, \tbl, #PAGE_SIZE orr \tmp2, \tmp2, #PMD_TYPE_TABLE // address of next table and entry type str \tmp2, [\tbl, \tmp1, lsl #3] add \tbl, \tbl, #PAGE_SIZE // next level table page .endm /* * Macro to populate the PGD (and possibily PUD) for the corresponding * block entry in the next level (tbl) for the given virtual address. * * Preserves: tbl, next, virt * Corrupts: tmp1, tmp2 */ .macro create_pgd_entry, tbl, virt, tmp1, tmp2 create_table_entry \tbl, \virt, PGDIR_SHIFT, PTRS_PER_PGD, \tmp1, \tmp2 #if SWAPPER_PGTABLE_LEVELS > 3 create_table_entry \tbl, \virt, PUD_SHIFT, PTRS_PER_PUD, \tmp1, \tmp2 #endif #if SWAPPER_PGTABLE_LEVELS > 2 create_table_entry \tbl, \virt, SWAPPER_TABLE_SHIFT, PTRS_PER_PTE, \tmp1, \tmp2 #endif .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, #SWAPPER_BLOCK_SHIFT lsr \start, \start, #SWAPPER_BLOCK_SHIFT and \start, \start, #PTRS_PER_PTE - 1 // table index orr \phys, \flags, \phys, lsl #SWAPPER_BLOCK_SHIFT // table entry lsr \end, \end, #SWAPPER_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, #SWAPPER_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 */ __create_page_tables: mov x28, lr /* * Invalidate the idmap and swapper page tables to avoid potential * dirty cache lines being evicted. */ adrp x0, idmap_pg_dir adrp x1, swapper_pg_dir + SWAPPER_DIR_SIZE bl __inval_cache_range /* * Clear the idmap and swapper page tables. */ adrp x0, idmap_pg_dir adrp x6, swapper_pg_dir + 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 mov x7, SWAPPER_MM_MMUFLAGS /* * Create the identity mapping. */ adrp x0, idmap_pg_dir adrp x3, __idmap_text_start // __pa(__idmap_text_start) #ifndef CONFIG_ARM64_VA_BITS_48 #define EXTRA_SHIFT (PGDIR_SHIFT + PAGE_SHIFT - 3) #define EXTRA_PTRS (1 << (48 - EXTRA_SHIFT)) /* * If VA_BITS < 48, it may be too small to allow for an ID mapping to be * created that covers system RAM if that is located sufficiently high * in the physical address space. So for the ID map, use an extended * virtual range in that case, by configuring an additional translation * level. * First, we have to verify our assumption that the current value of * VA_BITS was chosen such that all translation levels are fully * utilised, and that lowering T0SZ will always result in an additional * translation level to be configured. */ #if VA_BITS != EXTRA_SHIFT #error "Mismatch between VA_BITS and page size/number of translation levels" #endif /* * Calculate the maximum allowed value for TCR_EL1.T0SZ so that the * entire ID map region can be mapped. As T0SZ == (64 - #bits used), * this number conveniently equals the number of leading zeroes in * the physical address of __idmap_text_end. */ adrp x5, __idmap_text_end clz x5, x5 cmp x5, TCR_T0SZ(VA_BITS) // default T0SZ small enough? b.ge 1f // .. then skip additional level adr_l x6, idmap_t0sz str x5, [x6] dmb sy dc ivac, x6 // Invalidate potentially stale cache line create_table_entry x0, x3, EXTRA_SHIFT, EXTRA_PTRS, x5, x6 1: #endif create_pgd_entry x0, x3, x5, x6 mov x5, x3 // __pa(__idmap_text_start) adr_l x6, __idmap_text_end // __pa(__idmap_text_end) create_block_map x0, x7, x3, x5, x6 /* * Map the kernel image (starting with PHYS_OFFSET). */ adrp x0, swapper_pg_dir mov_q x5, KIMAGE_VADDR + TEXT_OFFSET // compile time __va(_text) add x5, x5, x23 // add KASLR displacement create_pgd_entry x0, x5, x3, x6 adrp x6, _end // runtime __pa(_end) adrp x3, _text // runtime __pa(_text) sub x6, x6, x3 // _end - _text add x6, x6, x5 // runtime __va(_end) create_block_map x0, x7, x3, x5, x6 /* * 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. */ adrp x0, idmap_pg_dir adrp x1, swapper_pg_dir + SWAPPER_DIR_SIZE dmb sy bl __inval_cache_range ret x28 ENDPROC(__create_page_tables) .ltorg /* * The following fragment of code is executed with the MMU enabled. */ .set initial_sp, init_thread_union + THREAD_START_SP __primary_switched: mov x28, lr // preserve LR adr_l x8, vectors // load VBAR_EL1 with virtual msr vbar_el1, x8 // vector table address isb // Clear BSS adr_l x0, __bss_start mov x1, xzr adr_l x2, __bss_stop sub x2, x2, x0 bl __pi_memset dsb ishst // Make zero page visible to PTW adr_l sp, initial_sp, x4 mov x4, sp and x4, x4, #~(THREAD_SIZE - 1) msr sp_el0, x4 // Save thread_info str_l x21, __fdt_pointer, x5 // Save FDT pointer ldr_l x4, kimage_vaddr // Save the offset between sub x4, x4, x24 // the kernel virtual and str_l x4, kimage_voffset, x5 // physical mappings mov x29, #0 #ifdef CONFIG_KASAN bl kasan_early_init #endif #ifdef CONFIG_RANDOMIZE_BASE tst x23, ~(MIN_KIMG_ALIGN - 1) // already running randomized? b.ne 0f mov x0, x21 // pass FDT address in x0 mov x1, x23 // pass modulo offset in x1 bl kaslr_early_init // parse FDT for KASLR options cbz x0, 0f // KASLR disabled? just proceed orr x23, x23, x0 // record KASLR offset ret x28 // we must enable KASLR, return // to __enable_mmu() 0: #endif b start_kernel ENDPROC(__primary_switched) /* * end early head section, begin head code that is also used for * hotplug and needs to have the same protections as the text region */ .section ".text","ax" ENTRY(kimage_vaddr) .quad _text - TEXT_OFFSET /* * 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 2: #ifdef CONFIG_ARM64_VHE /* * Check for VHE being present. For the rest of the EL2 setup, * x2 being non-zero indicates that we do have VHE, and that the * kernel is intended to run at EL2. */ mrs x2, id_aa64mmfr1_el1 ubfx x2, x2, #8, #4 #else mov x2, xzr #endif /* Hyp configuration. */ mov x0, #HCR_RW // 64-bit EL1 cbz x2, set_hcr orr x0, x0, #HCR_TGE // Enable Host Extensions orr x0, x0, #HCR_E2H set_hcr: msr hcr_el2, x0 isb /* 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 #ifdef CONFIG_ARM_GIC_V3 /* GICv3 system register access */ mrs x0, id_aa64pfr0_el1 ubfx x0, x0, #24, #4 cmp x0, #1 b.ne 3f mrs_s x0, ICC_SRE_EL2 orr x0, x0, #ICC_SRE_EL2_SRE // Set ICC_SRE_EL2.SRE==1 orr x0, x0, #ICC_SRE_EL2_ENABLE // Set ICC_SRE_EL2.Enable==1 msr_s ICC_SRE_EL2, x0 isb // Make sure SRE is now set mrs_s x0, ICC_SRE_EL2 // Read SRE back, tbz x0, #0, 3f // and check that it sticks msr_s ICH_HCR_EL2, xzr // Reset ICC_HCR_EL2 to defaults 3: #endif /* Populate ID registers. */ mrs x0, midr_el1 mrs x1, mpidr_el1 msr vpidr_el2, x0 msr vmpidr_el2, x1 /* * When VHE is not in use, early init of EL2 and EL1 needs to be * done here. * When VHE _is_ in use, EL1 will not be used in the host and * requires no configuration, and all non-hyp-specific EL2 setup * will be done via the _EL1 system register aliases in __cpu_setup. */ cbnz x2, 1f /* 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 1: #ifdef CONFIG_COMPAT msr hstr_el2, xzr // Disable CP15 traps to EL2 #endif /* EL2 debug */ mrs x0, id_aa64dfr0_el1 // Check ID_AA64DFR0_EL1 PMUVer sbfx x0, x0, #8, #4 cmp x0, #1 b.lt 4f // Skip if no PMU present mrs x0, pmcr_el0 // Disable debug access traps ubfx x0, x0, #11, #5 // to EL2 and allow access to msr mdcr_el2, x0 // all PMU counters from EL1 4: /* Stage-2 translation */ msr vttbr_el2, xzr cbz x2, install_el2_stub mov w20, #BOOT_CPU_MODE_EL2 // This CPU booted in EL2 isb ret install_el2_stub: /* Hypervisor stub */ adrp x0, __hyp_stub_vectors add x0, x0, #:lo12:__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. */ set_cpu_boot_mode_flag: adr_l x1, __boot_cpu_mode 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 .align L1_CACHE_SHIFT ENTRY(__boot_cpu_mode) .long BOOT_CPU_MODE_EL2 .long BOOT_CPU_MODE_EL1 .popsection /* * 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 set_cpu_boot_mode_flag mrs x0, mpidr_el1 mov_q x1, MPIDR_HWID_BITMASK and x0, x0, x1 adr_l x3, secondary_holding_pen_release 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 set_cpu_boot_mode_flag b secondary_startup ENDPROC(secondary_entry) secondary_startup: /* * Common entry point for secondary CPUs. */ bl __cpu_setup // initialise processor adr_l x27, __secondary_switch // address to jump to after enabling the MMU b __enable_mmu ENDPROC(secondary_startup) __secondary_switched: adr_l x5, vectors msr vbar_el1, x5 isb adr_l x0, secondary_data ldr x0, [x0, #CPU_BOOT_STACK] // get secondary_data.stack mov sp, x0 and x0, x0, #~(THREAD_SIZE - 1) msr sp_el0, x0 // save thread_info mov x29, #0 b secondary_start_kernel ENDPROC(__secondary_switched) /* * The booting CPU updates the failed status @__early_cpu_boot_status, * with MMU turned off. * * update_early_cpu_boot_status tmp, status * - Corrupts tmp1, tmp2 * - Writes 'status' to __early_cpu_boot_status and makes sure * it is committed to memory. */ .macro update_early_cpu_boot_status status, tmp1, tmp2 mov \tmp2, #\status adr_l \tmp1, __early_cpu_boot_status str \tmp2, [\tmp1] dmb sy dc ivac, \tmp1 // Invalidate potentially stale cache line .endm .pushsection .data..cacheline_aligned .align L1_CACHE_SHIFT ENTRY(__early_cpu_boot_status) .long 0 .popsection /* * Enable the MMU. * * x0 = SCTLR_EL1 value for turning on the MMU. * x27 = *virtual* address to jump to upon completion * * Other registers depend on the function called upon completion. * * Checks if the selected granule size is supported by the CPU. * If it isn't, park the CPU */ .section ".idmap.text", "ax" ENTRY(__enable_mmu) mrs x22, sctlr_el1 // preserve old SCTLR_EL1 value mrs x1, ID_AA64MMFR0_EL1 ubfx x2, x1, #ID_AA64MMFR0_TGRAN_SHIFT, 4 cmp x2, #ID_AA64MMFR0_TGRAN_SUPPORTED b.ne __no_granule_support update_early_cpu_boot_status 0, x1, x2 adrp x1, idmap_pg_dir adrp x2, swapper_pg_dir msr ttbr0_el1, x1 // load TTBR0 msr ttbr1_el1, x2 // load TTBR1 isb msr sctlr_el1, x0 isb /* * Invalidate the local I-cache so that any instructions fetched * speculatively from the PoC are discarded, since they may have * been dynamically patched at the PoU. */ ic iallu dsb nsh isb #ifdef CONFIG_RANDOMIZE_BASE mov x19, x0 // preserve new SCTLR_EL1 value blr x27 /* * If we return here, we have a KASLR displacement in x23 which we need * to take into account by discarding the current kernel mapping and * creating a new one. */ msr sctlr_el1, x22 // disable the MMU isb bl __create_page_tables // recreate kernel mapping msr sctlr_el1, x19 // re-enable the MMU isb ic iallu // flush instructions fetched dsb nsh // via old mapping isb #endif br x27 ENDPROC(__enable_mmu) __no_granule_support: /* Indicate that this CPU can't boot and is stuck in the kernel */ update_early_cpu_boot_status CPU_STUCK_IN_KERNEL, x1, x2 1: wfe wfi b 1b ENDPROC(__no_granule_support) __primary_switch: #ifdef CONFIG_RELOCATABLE /* * Iterate over each entry in the relocation table, and apply the * relocations in place. */ ldr w9, =__rela_offset // offset to reloc table ldr w10, =__rela_size // size of reloc table mov_q x11, KIMAGE_VADDR // default virtual offset add x11, x11, x23 // actual virtual offset add x9, x9, x11 // __va(.rela) add x10, x9, x10 // __va(.rela) + sizeof(.rela) 0: cmp x9, x10 b.hs 1f ldp x11, x12, [x9], #24 ldr x13, [x9, #-8] cmp w12, #R_AARCH64_RELATIVE b.ne 0b add x13, x13, x23 // relocate str x13, [x11, x23] b 0b 1: #endif ldr x8, =__primary_switched br x8 ENDPROC(__primary_switch) __secondary_switch: ldr x8, =__secondary_switched br x8 ENDPROC(__secondary_switch)