diff options
Diffstat (limited to 'debug_rom')
| -rw-r--r-- | debug_rom/Makefile | 20 | ||||
| -rwxr-xr-x | debug_rom/debug_rom.S | 105 | ||||
| -rw-r--r-- | debug_rom/debug_rom.h | 18 | ||||
| -rw-r--r-- | debug_rom/link.ld | 11 |
4 files changed, 154 insertions, 0 deletions
diff --git a/debug_rom/Makefile b/debug_rom/Makefile new file mode 100644 index 0000000..d66b84f --- /dev/null +++ b/debug_rom/Makefile @@ -0,0 +1,20 @@ +# Recursive make is bad, but in this case we're cross compiling which is a +# pretty unusual use case. + +CC = $(RISCV)/bin/riscv64-unknown-elf-gcc +OBJCOPY = $(RISCV)/bin/riscv64-unknown-elf-objcopy + +%.o: %.S + $(CC) -c $< + +debug_rom.h: debug_rom.raw + xxd -i $^ | sed "s/^unsigned/static const unsigned/" > $@ + +debug_rom.raw: debug_rom + $(OBJCOPY) -O binary --only-section .text debug_rom debug_rom.raw + +debug_rom: debug_rom.o + $(CC) -nostdlib -nostartfiles -Tlink.ld -o $@ $^ + +clean: + rm -f debug_rom debug_rom.o debug_rom.raw debug_rom.h diff --git a/debug_rom/debug_rom.S b/debug_rom/debug_rom.S new file mode 100755 index 0000000..230f4b4 --- /dev/null +++ b/debug_rom/debug_rom.S @@ -0,0 +1,105 @@ +# This code should be functional. Doesn't have to be optimal. +# I'm writing it to prove that it can be done. + +# TODO: Update these constants once they're finalized in the doc. + +#define DCSR 0x790 +#define DCSR_CAUSE_DEBINT 3 +#define DCSR_HALT_OFFSET 3 +#define DCSR_DEBUGINT_OFFSET 10 + +#define DSCRATCH 0x792 + +#define MCPUID 0xf00 +#define MHARTID 0xf10 + +#define DEBUG_RAM 0x400 +#define DEBUG_RAM_SIZE 64 + +#define SETHALTNOT 0x100 +#define CLEARHALTNOT 0x104 +#define CLEARDEBINT 0x108 + + .global entry + .global resume + + # Automatically called when Debug Mode is first entered. +entry: j _entry + # Should be called by Debug RAM code that has finished execution and + # wants to return to Debug Mode. +resume: + # Clear debug interrupt. +clear_debint: + csrr s1, MHARTID + sw s1, CLEARDEBINT(zero) +clear_debint_loop: + csrr s1, DCSR + andi s1, s1, (1<<DCSR_DEBUGINT_OFFSET) + bnez s1, wait_for_interrupt + + # Restore s1. + csrr s1, MCPUID + bltz s1, restore_not_32 +restore_32: + lw s1, (DEBUG_RAM + DEBUG_RAM_SIZE - 4)(zero) + j check_halt +restore_not_32: + slli s1, s1, 1 + bltz s1, restore_128 +restore_64: + ld s1, (DEBUG_RAM + DEBUG_RAM_SIZE - 8)(zero) + j check_halt +restore_128: + nop #lq s1, (DEBUG_RAM + DEBUG_RAM_SIZE - 16)(zero) + +check_halt: + csrr s0, DCSR + andi s0, s0, (1<<DCSR_HALT_OFFSET) + beqz s0, exit + j wait_for_interrupt + +exit: + # Restore s0. + csrr s0, DSCRATCH + eret + + +_entry: + # Save s0 in DSCRATCH + csrw DSCRATCH, s0 + + # Check why we're here + csrr s0, DCSR + # cause is in bits 2:0 of dcsr + andi s0, s0, 7 + addi s0, s0, -DCSR_CAUSE_DEBINT + bnez s0, spontaneous_halt + +jdebugram: + # Save s1 so that the debug program can use two registers. + csrr s0, MCPUID + bltz s0, save_not_32 +save_32: + sw s1, (DEBUG_RAM + DEBUG_RAM_SIZE - 4)(zero) + jr zero, DEBUG_RAM +save_not_32: + slli s0, s0, 1 + bltz s0, save_128 +save_64: + sd s1, (DEBUG_RAM + DEBUG_RAM_SIZE - 8)(zero) + jr zero, DEBUG_RAM +save_128: + nop #sq s1, (DEBUG_RAM + DEBUG_RAM_SIZE - 16)(zero) + jr zero, DEBUG_RAM + +spontaneous_halt: + csrr s0, MHARTID + sw s0, SETHALTNOT(zero) + csrsi DCSR, DCSR_HALT_OFFSET + +wait_for_interrupt: + csrr s0, DCSR + andi s0, s0, (1<<DCSR_DEBUGINT_OFFSET) + beqz s0, wait_for_interrupt + + j jdebugram diff --git a/debug_rom/debug_rom.h b/debug_rom/debug_rom.h new file mode 100644 index 0000000..1c53e11 --- /dev/null +++ b/debug_rom/debug_rom.h @@ -0,0 +1,18 @@ +static const unsigned char debug_rom_raw[] = { + 0x6f, 0x00, 0x40, 0x05, 0xf3, 0x24, 0x00, 0xf1, 0x23, 0x24, 0x90, 0x10, + 0xf3, 0x24, 0x00, 0x79, 0x93, 0xf4, 0x04, 0x40, 0x63, 0x94, 0x04, 0x08, + 0xf3, 0x24, 0x00, 0xf0, 0x63, 0xc6, 0x04, 0x00, 0x83, 0x24, 0xc0, 0x43, + 0x6f, 0x00, 0x80, 0x01, 0x93, 0x94, 0x14, 0x00, 0x63, 0xc6, 0x04, 0x00, + 0x83, 0x34, 0x80, 0x43, 0x6f, 0x00, 0x80, 0x00, 0x13, 0x00, 0x00, 0x00, + 0x73, 0x24, 0x00, 0x79, 0x13, 0x74, 0x84, 0x00, 0x63, 0x04, 0x04, 0x00, + 0x6f, 0x00, 0x40, 0x05, 0x73, 0x24, 0x20, 0x79, 0x73, 0x00, 0x00, 0x10, + 0x73, 0x10, 0x24, 0x79, 0x73, 0x24, 0x00, 0x79, 0x13, 0x74, 0x74, 0x00, + 0x13, 0x04, 0xd4, 0xff, 0x63, 0x16, 0x04, 0x02, 0x73, 0x24, 0x00, 0xf0, + 0x63, 0x46, 0x04, 0x00, 0x23, 0x2e, 0x90, 0x42, 0x67, 0x00, 0x00, 0x40, + 0x13, 0x14, 0x14, 0x00, 0x63, 0x46, 0x04, 0x00, 0x23, 0x3c, 0x90, 0x42, + 0x67, 0x00, 0x00, 0x40, 0x13, 0x00, 0x00, 0x00, 0x67, 0x00, 0x00, 0x40, + 0x73, 0x24, 0x00, 0xf1, 0x23, 0x20, 0x80, 0x10, 0x73, 0xe0, 0x01, 0x79, + 0x73, 0x24, 0x00, 0x79, 0x13, 0x74, 0x04, 0x40, 0xe3, 0x0c, 0x04, 0xfe, + 0x6f, 0xf0, 0x1f, 0xfc +}; +static const unsigned int debug_rom_raw_len = 172; diff --git a/debug_rom/link.ld b/debug_rom/link.ld new file mode 100644 index 0000000..356099c --- /dev/null +++ b/debug_rom/link.ld @@ -0,0 +1,11 @@ +OUTPUT_ARCH( "riscv" ) +ENTRY( entry ) +SECTIONS +{ + . = 0xfffff800; /* TODO: 0x800 */ + .text : + { + *(.text) + } + _end = .; +} |