/* SPDX-License-Identifier: GPL-2.0+ */ /* * crt0 - C-runtime startup Code for AArch64 U-Boot * * (C) Copyright 2013 * David Feng * * (C) Copyright 2012 * Albert ARIBAUD */ #include #include #include #include /* * This file handles the target-independent stages of the U-Boot * start-up where a C runtime environment is needed. Its entry point * is _main and is branched into from the target's start.S file. * * _main execution sequence is: * * 1. Set up initial environment for calling board_init_f(). * This environment only provides a stack and a place to store * the GD ('global data') structure, both located in some readily * available RAM (SRAM, locked cache...). In this context, VARIABLE * global data, initialized or not (BSS), are UNAVAILABLE; only * CONSTANT initialized data are available. GD should be zeroed * before board_init_f() is called. * * 2. Call board_init_f(). This function prepares the hardware for * execution from system RAM (DRAM, DDR...) As system RAM may not * be available yet, , board_init_f() must use the current GD to * store any data which must be passed on to later stages. These * data include the relocation destination, the future stack, and * the future GD location. * * 3. Set up intermediate environment where the stack and GD are the * ones allocated by board_init_f() in system RAM, but BSS and * initialized non-const data are still not available. * * 4a.For U-Boot proper (not SPL), call relocate_code(). This function * relocates U-Boot from its current location into the relocation * destination computed by board_init_f(). * * 4b.For SPL, board_init_f() just returns (to crt0). There is no * code relocation in SPL. * * 5. Set up final environment for calling board_init_r(). This * environment has BSS (initialized to 0), initialized non-const * data (initialized to their intended value), and stack in system * RAM (for SPL moving the stack and GD into RAM is optional - see * CONFIG_SPL_STACK_R). GD has retained values set by board_init_f(). * * TODO: For SPL, implement stack relocation on AArch64. * * 6. For U-Boot proper (not SPL), some CPUs have some work left to do * at this point regarding memory, so call c_runtime_cpu_setup. * * 7. Branch to board_init_r(). * * For more information see 'Board Initialisation Flow in README. */ ENTRY(_main) /* * Set up initial C runtime environment and call board_init_f(0). */ #if defined(CONFIG_TPL_BUILD) && defined(CONFIG_TPL_NEEDS_SEPARATE_STACK) ldr x0, =(CONFIG_TPL_STACK) #elif defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_STACK) ldr x0, =(CONFIG_SPL_STACK) #elif defined(CONFIG_INIT_SP_RELATIVE) #if CONFIG_POSITION_INDEPENDENT adrp x0, __bss_start /* x0 <- Runtime &__bss_start */ add x0, x0, #:lo12:__bss_start #else adr x0, __bss_start #endif add x0, x0, #CONFIG_SYS_INIT_SP_BSS_OFFSET #else ldr x0, =(CONFIG_SYS_INIT_SP_ADDR) #endif bic sp, x0, #0xf /* 16-byte alignment for ABI compliance */ mov x0, sp bl board_init_f_alloc_reserve mov sp, x0 /* set up gd here, outside any C code */ mov x18, x0 bl board_init_f_init_reserve mov x0, #0 bl board_init_f #if !defined(CONFIG_SPL_BUILD) /* * Set up intermediate environment (new sp and gd) and call * relocate_code(addr_moni). Trick here is that we'll return * 'here' but relocated. */ ldr x0, [x18, #GD_START_ADDR_SP] /* x0 <- gd->start_addr_sp */ bic sp, x0, #0xf /* 16-byte alignment for ABI compliance */ ldr x18, [x18, #GD_NEW_GD] /* x18 <- gd->new_gd */ /* Skip relocation in case gd->gd_flags & GD_FLG_SKIP_RELOC */ ldr x0, [x18, #GD_FLAGS] /* x0 <- gd->flags */ tbnz x0, 11, relocation_return /* GD_FLG_SKIP_RELOC is bit 11 */ adr lr, relocation_return #if CONFIG_POSITION_INDEPENDENT /* Add in link-vs-runtime offset */ adrp x0, _start /* x0 <- Runtime value of _start */ add x0, x0, #:lo12:_start ldr x9, _TEXT_BASE /* x9 <- Linked value of _start */ sub x9, x9, x0 /* x9 <- Run-vs-link offset */ add lr, lr, x9 #if defined(CONFIG_SYS_RELOC_GD_ENV_ADDR) ldr x0, [x18, #GD_ENV_ADDR] /* x0 <- gd->env_addr */ add x0, x0, x9 str x0, [x18, #GD_ENV_ADDR] #endif #endif /* Add in link-vs-relocation offset */ ldr x9, [x18, #GD_RELOC_OFF] /* x9 <- gd->reloc_off */ add lr, lr, x9 /* new return address after relocation */ ldr x0, [x18, #GD_RELOCADDR] /* x0 <- gd->relocaddr */ b relocate_code relocation_return: /* * Set up final (full) environment */ bl c_runtime_cpu_setup /* still call old routine */ #endif /* !CONFIG_SPL_BUILD */ #if !defined(CONFIG_SPL_BUILD) || CONFIG_IS_ENABLED(FRAMEWORK) #if defined(CONFIG_SPL_BUILD) bl spl_relocate_stack_gd /* may return NULL */ /* set up gd here, outside any C code, if new stack is returned */ cmp x0, #0 csel x18, x0, x18, ne /* * Perform 'sp = (x0 != NULL) ? x0 : sp' while working * around the constraint that conditional moves can not * have 'sp' as an operand */ mov x1, sp cmp x0, #0 csel x0, x0, x1, ne mov sp, x0 #endif /* * Clear BSS section */ ldr x0, =__bss_start /* this is auto-relocated! */ ldr x1, =__bss_end /* this is auto-relocated! */ clear_loop: str xzr, [x0], #8 cmp x0, x1 b.lo clear_loop /* call board_init_r(gd_t *id, ulong dest_addr) */ mov x0, x18 /* gd_t */ ldr x1, [x18, #GD_RELOCADDR] /* dest_addr */ b board_init_r /* PC relative jump */ /* NOTREACHED - board_init_r() does not return */ #endif ENDPROC(_main)