diff options
Diffstat (limited to 'arch/riscv/kernel/head.S')
| -rw-r--r-- | arch/riscv/kernel/head.S | 396 |
1 files changed, 396 insertions, 0 deletions
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S new file mode 100644 index 000000000..47d1411db --- /dev/null +++ b/arch/riscv/kernel/head.S @@ -0,0 +1,396 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Copyright (C) 2012 Regents of the University of California + */ + +#include <asm/asm-offsets.h> +#include <asm/asm.h> +#include <linux/init.h> +#include <linux/linkage.h> +#include <asm/thread_info.h> +#include <asm/page.h> +#include <asm/csr.h> +#include <asm/hwcap.h> +#include <asm/image.h> +#include "efi-header.S" + +__HEAD +ENTRY(_start) + /* + * Image header expected by Linux boot-loaders. The image header data + * structure is described in asm/image.h. + * Do not modify it without modifying the structure and all bootloaders + * that expects this header format!! + */ +#ifdef CONFIG_EFI + /* + * This instruction decodes to "MZ" ASCII required by UEFI. + */ + c.li s4,-13 + j _start_kernel +#else + /* jump to start kernel */ + j _start_kernel + /* reserved */ + .word 0 +#endif + .balign 8 +#ifdef CONFIG_RISCV_M_MODE + /* Image load offset (0MB) from start of RAM for M-mode */ + .dword 0 +#else +#if __riscv_xlen == 64 + /* Image load offset(2MB) from start of RAM */ + .dword 0x200000 +#else + /* Image load offset(4MB) from start of RAM */ + .dword 0x400000 +#endif +#endif + /* Effective size of kernel image */ + .dword _end - _start + .dword __HEAD_FLAGS + .word RISCV_HEADER_VERSION + .word 0 + .dword 0 + .ascii RISCV_IMAGE_MAGIC + .balign 4 + .ascii RISCV_IMAGE_MAGIC2 +#ifdef CONFIG_EFI + .word pe_head_start - _start +pe_head_start: + + __EFI_PE_HEADER +#else + .word 0 +#endif + +.align 2 +#ifdef CONFIG_MMU +relocate: + /* Relocate return address */ + li a1, PAGE_OFFSET + la a2, _start + sub a1, a1, a2 + add ra, ra, a1 + + /* Point stvec to virtual address of intruction after satp write */ + la a2, 1f + add a2, a2, a1 + csrw CSR_TVEC, a2 + + /* Compute satp for kernel page tables, but don't load it yet */ + srl a2, a0, PAGE_SHIFT + li a1, SATP_MODE + or a2, a2, a1 + + /* + * Load trampoline page directory, which will cause us to trap to + * stvec if VA != PA, or simply fall through if VA == PA. We need a + * full fence here because setup_vm() just wrote these PTEs and we need + * to ensure the new translations are in use. + */ + la a0, trampoline_pg_dir + srl a0, a0, PAGE_SHIFT + or a0, a0, a1 + sfence.vma + csrw CSR_SATP, a0 +.align 2 +1: + /* Set trap vector to spin forever to help debug */ + la a0, .Lsecondary_park + csrw CSR_TVEC, a0 + + /* Reload the global pointer */ +.option push +.option norelax + la gp, __global_pointer$ +.option pop + + /* + * Switch to kernel page tables. A full fence is necessary in order to + * avoid using the trampoline translations, which are only correct for + * the first superpage. Fetching the fence is guarnteed to work + * because that first superpage is translated the same way. + */ + csrw CSR_SATP, a2 + sfence.vma + + ret +#endif /* CONFIG_MMU */ +#ifdef CONFIG_SMP + .global secondary_start_sbi +secondary_start_sbi: + /* Mask all interrupts */ + csrw CSR_IE, zero + csrw CSR_IP, zero + + /* Load the global pointer */ + .option push + .option norelax + la gp, __global_pointer$ + .option pop + + /* + * Disable FPU to detect illegal usage of + * floating point in kernel space + */ + li t0, SR_FS + csrc CSR_STATUS, t0 + + /* Set trap vector to spin forever to help debug */ + la a3, .Lsecondary_park + csrw CSR_TVEC, a3 + + slli a3, a0, LGREG + la a4, __cpu_up_stack_pointer + la a5, __cpu_up_task_pointer + add a4, a3, a4 + add a5, a3, a5 + REG_L sp, (a4) + REG_L tp, (a5) + + .global secondary_start_common +secondary_start_common: + +#ifdef CONFIG_MMU + /* Enable virtual memory and relocate to virtual address */ + la a0, swapper_pg_dir + call relocate +#endif + call setup_trap_vector + tail smp_callin +#endif /* CONFIG_SMP */ + +.align 2 +setup_trap_vector: + /* Set trap vector to exception handler */ + la a0, handle_exception + csrw CSR_TVEC, a0 + + /* + * Set sup0 scratch register to 0, indicating to exception vector that + * we are presently executing in kernel. + */ + csrw CSR_SCRATCH, zero + ret + +.align 2 +.Lsecondary_park: + /* We lack SMP support or have too many harts, so park this hart */ + wfi + j .Lsecondary_park + +END(_start) + + __INIT +ENTRY(_start_kernel) + /* Mask all interrupts */ + csrw CSR_IE, zero + csrw CSR_IP, zero + +#ifdef CONFIG_RISCV_M_MODE + /* flush the instruction cache */ + fence.i + + /* Reset all registers except ra, a0, a1 */ + call reset_regs + + /* + * Setup a PMP to permit access to all of memory. Some machines may + * not implement PMPs, so we set up a quick trap handler to just skip + * touching the PMPs on any trap. + */ + la a0, pmp_done + csrw CSR_TVEC, a0 + + li a0, -1 + csrw CSR_PMPADDR0, a0 + li a0, (PMP_A_NAPOT | PMP_R | PMP_W | PMP_X) + csrw CSR_PMPCFG0, a0 +.align 2 +pmp_done: + + /* + * The hartid in a0 is expected later on, and we have no firmware + * to hand it to us. + */ + csrr a0, CSR_MHARTID +#endif /* CONFIG_RISCV_M_MODE */ + + /* Load the global pointer */ +.option push +.option norelax + la gp, __global_pointer$ +.option pop + + /* + * Disable FPU to detect illegal usage of + * floating point in kernel space + */ + li t0, SR_FS + csrc CSR_STATUS, t0 + +#ifdef CONFIG_SMP + li t0, CONFIG_NR_CPUS + blt a0, t0, .Lgood_cores + tail .Lsecondary_park +.Lgood_cores: +#endif + + /* Pick one hart to run the main boot sequence */ + la a3, hart_lottery + li a2, 1 + amoadd.w a3, a2, (a3) + bnez a3, .Lsecondary_start + + /* Clear BSS for flat non-ELF images */ + la a3, __bss_start + la a4, __bss_stop + ble a4, a3, clear_bss_done +clear_bss: + REG_S zero, (a3) + add a3, a3, RISCV_SZPTR + blt a3, a4, clear_bss +clear_bss_done: + + /* Save hart ID and DTB physical address */ + mv s0, a0 + mv s1, a1 + la a2, boot_cpu_hartid + REG_S a0, (a2) + + /* Initialize page tables and relocate to virtual addresses */ + la tp, init_task + la sp, init_thread_union + THREAD_SIZE + mv a0, s1 + call setup_vm +#ifdef CONFIG_MMU + la a0, early_pg_dir + call relocate +#endif /* CONFIG_MMU */ + + call setup_trap_vector + /* Restore C environment */ + la tp, init_task + sw zero, TASK_TI_CPU(tp) + la sp, init_thread_union + THREAD_SIZE + +#ifdef CONFIG_KASAN + call kasan_early_init +#endif + /* Start the kernel */ + call soc_early_init + tail start_kernel + +.Lsecondary_start: +#ifdef CONFIG_SMP + /* Set trap vector to spin forever to help debug */ + la a3, .Lsecondary_park + csrw CSR_TVEC, a3 + + slli a3, a0, LGREG + la a1, __cpu_up_stack_pointer + la a2, __cpu_up_task_pointer + add a1, a3, a1 + add a2, a3, a2 + + /* + * This hart didn't win the lottery, so we wait for the winning hart to + * get far enough along the boot process that it should continue. + */ +.Lwait_for_cpu_up: + /* FIXME: We should WFI to save some energy here. */ + REG_L sp, (a1) + REG_L tp, (a2) + beqz sp, .Lwait_for_cpu_up + beqz tp, .Lwait_for_cpu_up + fence + + tail secondary_start_common +#endif + +END(_start_kernel) + +#ifdef CONFIG_RISCV_M_MODE +ENTRY(reset_regs) + li sp, 0 + li gp, 0 + li tp, 0 + li t0, 0 + li t1, 0 + li t2, 0 + li s0, 0 + li s1, 0 + li a2, 0 + li a3, 0 + li a4, 0 + li a5, 0 + li a6, 0 + li a7, 0 + li s2, 0 + li s3, 0 + li s4, 0 + li s5, 0 + li s6, 0 + li s7, 0 + li s8, 0 + li s9, 0 + li s10, 0 + li s11, 0 + li t3, 0 + li t4, 0 + li t5, 0 + li t6, 0 + csrw CSR_SCRATCH, 0 + +#ifdef CONFIG_FPU + csrr t0, CSR_MISA + andi t0, t0, (COMPAT_HWCAP_ISA_F | COMPAT_HWCAP_ISA_D) + beqz t0, .Lreset_regs_done + + li t1, SR_FS + csrs CSR_STATUS, t1 + fmv.s.x f0, zero + fmv.s.x f1, zero + fmv.s.x f2, zero + fmv.s.x f3, zero + fmv.s.x f4, zero + fmv.s.x f5, zero + fmv.s.x f6, zero + fmv.s.x f7, zero + fmv.s.x f8, zero + fmv.s.x f9, zero + fmv.s.x f10, zero + fmv.s.x f11, zero + fmv.s.x f12, zero + fmv.s.x f13, zero + fmv.s.x f14, zero + fmv.s.x f15, zero + fmv.s.x f16, zero + fmv.s.x f17, zero + fmv.s.x f18, zero + fmv.s.x f19, zero + fmv.s.x f20, zero + fmv.s.x f21, zero + fmv.s.x f22, zero + fmv.s.x f23, zero + fmv.s.x f24, zero + fmv.s.x f25, zero + fmv.s.x f26, zero + fmv.s.x f27, zero + fmv.s.x f28, zero + fmv.s.x f29, zero + fmv.s.x f30, zero + fmv.s.x f31, zero + csrw fcsr, 0 + /* note that the caller must clear SR_FS */ +#endif /* CONFIG_FPU */ +.Lreset_regs_done: + ret +END(reset_regs) +#endif /* CONFIG_RISCV_M_MODE */ + +__PAGE_ALIGNED_BSS + /* Empty zero page */ + .balign PAGE_SIZE |