diff options
| -rw-r--r-- | fw/fe310/bsp/gloss/crt0.S | 295 | ||||
| -rw-r--r-- | fw/fe310/bsp/init/Makefile | 13 | ||||
| -rw-r--r-- | fw/fe310/bsp/init/entry.S | 63 |
3 files changed, 139 insertions, 232 deletions
diff --git a/fw/fe310/bsp/gloss/crt0.S b/fw/fe310/bsp/gloss/crt0.S index 920ee4b..a8c5a74 100644 --- a/fw/fe310/bsp/gloss/crt0.S +++ b/fw/fe310/bsp/gloss/crt0.S @@ -1,246 +1,77 @@ -/* Copyright (c) 2017-2018 SiFive Inc. All rights reserved. +#========================================================================= +# crt0.S : Entry point for RISC-V user programs +#========================================================================= - This copyrighted material is made available to anyone wishing to use, - modify, copy, or redistribute it subject to the terms and conditions - of the FreeBSD License. This program is distributed in the hope that - it will be useful, but WITHOUT ANY WARRANTY expressed or implied, - including the implied warranties of MERCHANTABILITY or FITNESS FOR - A PARTICULAR PURPOSE. A copy of this license is available at - http://www.opensource.org/licenses. -*/ - -/* crt0.S: Entry point for RISC-V METAL programs. */ - -.section .text.libgloss.start -.global _start -.type _start, @function - - /* _start is defined by the METAL to have been called with the following - * arguments: - * a0: the hart ID of the currently executing hart. Harts can start at - * any arbitrary point, it's the C library's job to ensure the code is - * safe. - * a1: a pointer to a description of the machine on which this code is - * currently executing. This is probably 0 on an embedded system - * because they tend to not be dynamically portable. As such, newlib - * ignores this argument. - * a2: a pointer to a function that must be run after the envirnoment has - * been initialized, but before user code can be expected to be run. - * If this is 0 then there is no function to be run. */ + .section .text.libgloss.start + .global _start + .type _start, @function _start: -.cfi_startproc -.cfi_undefined ra - - /* This is a bit funky: it's not usually sane for _start to return, but in - * this case we actually want to in order to signal an error to the METAL. */ - mv s0, ra - - /* Before doing anything we must initialize the global pointer, as we cannot - * safely perform any access that may be relaxed without GP being set. This - * is done with relaxation disabled to avoid relaxing the address calculation - * to just "addi gp, gp, 0". */ -.option push -.option norelax - la gp, __global_pointer$ -.option pop - - /* The METAL is designed for a bare-metal environment and therefor is expected - * to define its own stack pointer. We also align the stack pointer here - * because the only RISC-V ABI that's currently defined mandates 16-byte - * stack alignment. */ - la sp, _sp - - /* Increment by hartid number of stack sizes */ - li t0, 0 - la t1, __stack_size -1: - beq t0, a0, 1f - add sp, sp, t1 - addi t0, t0, 1 - j 1b -1: - andi sp, sp, -16 - - /* If we're not hart 0, skip the initialization work */ - la t0, __metal_boot_hart - bne a0, t0, _skip_init + # Initialize global pointer + .option push + .option norelax +1:auipc gp, %pcrel_hi(__global_pointer$) + addi gp, gp, %pcrel_lo(1b) + .option pop + + # Clear the bss segment + la a0, metal_segment_bss_start + la a2, metal_segment_bss_end + sub a2, a2, a0 + li a1, 0 + call memset + + # Copy data segment + la a0, metal_segment_data_target_start + la a1, metal_segment_data_source_start + la a2, metal_segment_data_target_end + sub a2, a2, a0 + call memcpy - /* Embedded systems frequently require relocating the data segment before C - * code can be run -- for example, the data segment may exist in flash upon - * boot and then need to get relocated into a non-persistant writable memory - * before C code can execute. If this is the case we do so here. This step - * is optional: if the METAL provides an environment in which this relocation - * is not necessary then it must simply set metal_segment_data_source_start to - * be equal to metal_segment_data_target_start. */ - la t0, metal_segment_data_source_start - la t1, metal_segment_data_target_start - la t2, metal_segment_data_target_end - - beq t0, t1, 2f - bge t1, t2, 2f - -1: -#if __riscv_xlen == 32 - lw a0, 0(t0) - addi t0, t0, 4 - sw a0, 0(t1) - addi t1, t1, 4 - blt t1, t2, 1b -#else - ld a0, 0(t0) - addi t0, t0, 8 - sd a0, 0(t1) - addi t1, t1, 8 - blt t1, t2, 1b -#endif -2: - - /* Copy the ITIM section */ - la t0, metal_segment_itim_source_start - la t1, metal_segment_itim_target_start - la t2, metal_segment_itim_target_end - - beq t0, t1, 2f - bge t1, t2, 2f - -1: -#if __riscv_xlen == 32 - lw a0, 0(t0) - addi t0, t0, 4 - sw a0, 0(t1) - addi t1, t1, 4 - blt t1, t2, 1b -#else - ld a0, 0(t0) - addi t0, t0, 8 - sd a0, 0(t1) - addi t1, t1, 8 - blt t1, t2, 1b -#endif -2: - - /* Fence all subsequent instruction fetches until after the ITIM writes - complete */ fence.i - /* Zero the BSS segment. */ - la t1, metal_segment_bss_target_start - la t2, metal_segment_bss_target_end - - bge t1, t2, 2f - -1: -#if __riscv_xlen == 32 - sw x0, 0(t1) - addi t1, t1, 4 - blt t1, t2, 1b -#else - sd x0, 0(t1) - addi t1, t1, 8 - blt t1, t2, 1b -#endif -2: - - /* At this point we're in an environment that can execute C code. The first - * thing to do is to make the callback to the parent environment if it's been - * requested to do so. */ - beqz a2, 1f - jalr a2 -1: - - /* The RISC-V port only uses new-style constructors and destructors. */ - la a0, __libc_fini_array - call atexit - call __libc_init_array - -_skip_init: - - /* Synchronize harts so that secondary harts wait until hart 0 finishes - initializing */ - call __metal_synchronize_harts - - /* Check RISC-V isa and enable FS bits if Floating Point architecture. */ - csrr a5, misa - li a4, 0x10028 - and a5, a5, a4 - beqz a5, 1f - csrr a5, mstatus - lui a4, 0x2 - or a5, a5, a4 - csrw mstatus, a5 - csrwi fcsr, 0 -1: - - /* This is a C runtime, so main() is defined to have some arguments. Since - * there's nothing sane the METAL can pass we don't bother with that but - * instead just setup as close to a NOP as we can. */ - li a0, 1 /* argc=1 */ - la a1, argv /* argv = {"libgloss", NULL} */ - la a2, envp /* envp = {NULL} */ - call secondary_main - - /* Call exit to handle libc's cleanup routines. Under normal contains this - * shouldn't even get called, but I'm still not using a tail call here - * because returning to the METAL is the right thing to do in pathological - * situations. */ - call exit - - /* And here's where we return. Again, it's a bit odd but the METAL defines - * this as a bad idea (ie, as opposed to leaving it undefined) and at this - * point it's really the only thing left to do. */ - mv ra, s0 - ret - -.cfi_endproc - -/* RISC-V systems always use __libc_{init,fini}_array, but for compatibility we - * define _{init,fini} to do nothing. */ -.global _init -.type _init, @function -.global _fini -.type _fini, @function + # Copy itim segment + la a0, metal_segment_itim_target_start + la a1, metal_segment_itim_source_start + la a2, metal_segment_itim_target_end + sub a2, a2, a0 + call memcpy + + # Copy lim segment + la a0, metal_segment_lim_target_start + la a1, metal_segment_lim_source_start + la a2, metal_segment_lim_target_end + sub a2, a2, a0 + call memcpy + + la a0, __libc_fini_array # Register global termination functions + call atexit # to be called upon exit + call __libc_init_array # Run global initialization functions + + li a0, 1 # a0 = argc = 1 + la a1, argv # a1 = argv = {"libgloss", NULL} + la a2, envp # a2 = envp = NULL + call main + tail exit + .size _start, .-_start + + .global _init + .type _init, @function + .global _fini + .type _fini, @function _init: _fini: + # These don't have to do anything since we use init_array/fini_array. ret -.size _init, .-_init -.size _fini, .-_fini - -/* By default, secondary_main will cause secondary harts to spin forever. - * Users can redefine secondary_main themselves to run code on secondary harts */ -.weak secondary_main -.global secondary_main -.type secondary_main, @function - -secondary_main: - addi sp, sp, -16 -#if __riscv_xlen == 32 - sw ra, 4(sp) -#else - sd ra, 8(sp) -#endif - csrr t0, mhartid - la t1, __metal_boot_hart - beq t0, t1, 2f -1: - wfi - j 1b -2: - call main -#if __riscv_xlen == 32 - lw ra, 4(sp) -#else - ld ra, 8(sp) -#endif - addi sp, sp, 16 - ret + .size _init, .-_init + .size _fini, .-_fini /* This shim allows main() to be passed a set of arguments that can satisfy the * requirements of the C API. */ -.section .rodata.libgloss.start + .section .rodata.libgloss.start + .balign 8 argv: -.dc.a name + .dc.a name envp: -.dc.a 0 + .dc.a 0 name: -.asciz "libgloss" - + .asciz "libgloss" diff --git a/fw/fe310/bsp/init/Makefile b/fw/fe310/bsp/init/Makefile new file mode 100644 index 0000000..2df25e7 --- /dev/null +++ b/fw/fe310/bsp/init/Makefile @@ -0,0 +1,13 @@ +include ../../common.mk +CFLAGS += -I$(bsp_dir)/include -I$(bsp_dir)/drivers + +%.o: %.c + $(CC) $(CFLAGS) -c $< + +%.o: %.S + $(CC) $(CFLAGS) -c $< + +all: entry.o + +clean: + rm -f *.o diff --git a/fw/fe310/bsp/init/entry.S b/fw/fe310/bsp/init/entry.S new file mode 100644 index 0000000..6b80217 --- /dev/null +++ b/fw/fe310/bsp/init/entry.S @@ -0,0 +1,63 @@ +/* Copyright 2018 SiFive, Inc */ +/* SPDX-License-Identifier: Apache-2.0 */ + +/* This code executes before _start, which is contained inside the C library. + * In embedded systems we want to ensure that _enter, which contains the first + * code to be executed, can be loaded at a specific address. To enable this + * feature we provide the '.text.metal.init.enter' section, which is + * defined to have the first address being where execution should start. */ +.section .text.metal.init.enter +.global _enter +_enter: + .cfi_startproc + + /* Inform the debugger that there is nowhere to backtrace past _enter. */ + .cfi_undefined ra + + /* The absolute first thing that must happen is configuring the global + * pointer register, which must be done with relaxation disabled because + * it's not valid to obtain the address of any symbol without GP + * configured. The C environment might go ahead and do this again, but + * that's safe as it's a fixed register. */ +.option push +.option norelax +1:auipc gp, %pcrel_hi(__global_pointer$) + addi gp, gp, %pcrel_lo(1b) +.option pop + + /* Set up a trap vector */ + la t0, eos_trap_vector + csrw mtvec, t0 + + /* This is a bare-metal environment and therefor is expected + * to define its own stack pointer. We also align the stack pointer here + * because the only RISC-V ABI that's currently defined mandates 16-byte + * stack alignment. */ + la sp, _sp + andi sp, sp, -16 + + /* At this point we can enter the C runtime's startup file. */ + call _start + + /* If we've made it back here then there's probably something wrong. + * There's not a whole lot we can do, just try to make some noise. */ + la t0, 1f + csrw mtvec, t0 +1: + lw t1, 0(x0) + j 1b + + .cfi_endproc + +/* The GCC port might not emit a __register_frame_info symbol, which eventually + * results in a weak undefined reference that eventually causes crash when it + * is dereference early in boot. We really shouldn't need to put this here, + * but to deal with what I think is probably a bug in the linker script I'm + * going to leave this in for now. At least it's fairly cheap :) */ +.weak __register_frame_info +.global __register_frame_info +.section .text.metal.init.__register_frame_info +__register_frame_info: + .cfi_startproc + ret + .cfi_endproc |