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riscv-isa-sim
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debug: Use a more practical debug ROM

pull/94/head
Megan Wachs 9 years ago
parent
12b772563a
commit
d46f694d85
4 changed files with 83 additions and 161 deletions
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  1. 10
      debug_rom/Makefile
  2. 203
      debug_rom/debug_rom.S
  3. 23
      debug_rom/debug_rom.h
  4. 4
      debug_rom/link.ld

10
debug_rom/Makefile
View File

@ -6,7 +6,7 @@ OBJCOPY = $(RISCV)/bin/riscv64-unknown-elf-objcopy
COMPILE = $(CC) -nostdlib -nostartfiles -I.. -Tlink.ld
ELFS = debug_rom debug_rom32 debug_rom64
ELFS = debug_rom
DEPS = debug_rom.S link.ld
all: $(patsubst %,%.h,$(ELFS))
@ -18,13 +18,7 @@ all: $(patsubst %,%.h,$(ELFS))
$(OBJCOPY) -O binary --only-section .text $^ $@
debug_rom: $(DEPS)
$(COMPILE) -DRV32 -DRV64 -o $@ $^
debug_rom32: $(DEPS)
$(COMPILE) -DRV32 -DDEBUG_RAM_SIZE=28 -o $@ $^
debug_rom64: $(DEPS)
$(COMPILE) -DRV64 -o $@ $^
$(COMPILE) -o $@ $^
clean:
rm -f $(ELFS) debug_rom*.raw debug_rom*.h

203
debug_rom/debug_rom.S
View File

@ -1,152 +1,81 @@
# This code should be functional. Doesn't have to be optimal.
# I'm writing it to prove that it can be done.
// See LICENSE.SiFive for license details.
#include "riscv/encoding.h"
#include "spike/encoding.h"
# TODO: Update these constants once they're finalized in the doc.
// These are implementation-specific addresses in the Debug Module
#define HALTED 0x100
#define GOING 0x104
#define RESUMING 0x108
#define EXCEPTION 0x10C
#define DEBUG_RAM 0x400
#ifndef DEBUG_RAM_SIZE
# define DEBUG_RAM_SIZE 64
#endif
#define CLEARDEBINT 0x100
#define SETHALTNOT 0x10c
#if (defined(RV32) + defined(RV64) + defined(RV128)) > 1
# define MULTI_XLEN
#elif (defined(RV32) + defined(RV64) + defined(RV128)) == 0
# error define one or more of RV32, RV64, RV128
#endif
// Region of memory where each hart has 1
// byte to read.
#define FLAGS 0x400
#define FLAG_GO 0
#define FLAG_RESUME 1
.option norvc
.global entry
.global resume
.global exception
# 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.
// Entry location on ebreak, Halt, or Breakpoint
// It is the same for all harts. They branch when
// their GO or RESUME bit is set.
entry:
jal zero, _entry
resume:
j _resume
jal zero, _resume
exception:
# Set the last word of Debug RAM to all ones, to indicate that we hit
# an exception.
li s0, ~0
j _resume2
jal zero, _exception
_resume:
li s0, 0
_resume2:
_entry:
// This fence is required because the execution may have written something
// into the Abstract Data or Program Buffer registers.
fence
csrw CSR_DSCRATCH, s0 // Save s0 to allow signaling MHARTID
# Restore s1.
#ifdef MULTI_XLEN
csrr s1, CSR_MISA
#endif
#ifdef RV32
# ifdef MULTI_XLEN
bltz s1, restore_not_32
# endif
restore_32:
lw s1, (DEBUG_RAM + DEBUG_RAM_SIZE - 4)(zero)
# if defined(RV64) || defined(RV128)
j finish_restore
# endif
#endif
restore_not_32:
#if defined(RV64) && defined(RV128)
slli s1, s1, 1
bltz s1, restore_128
#endif
#ifdef RV64
restore_64:
ld s1, (DEBUG_RAM + DEBUG_RAM_SIZE - 8)(zero)
#endif
#if defined(RV64) && defined(RV128)
j finish_restore
#endif
#ifdef RV128
restore_128:
lq s1, (DEBUG_RAM + DEBUG_RAM_SIZE - 16)(zero)
#endif
finish_restore:
# s0 contains ~0 if we got here through an exception, and 0 otherwise.
# Store this to the last word in Debug RAM so the debugger can tell if
# an exception occurred.
sw s0, (DEBUG_RAM + DEBUG_RAM_SIZE - 4)(zero)
# Clear debug interrupt.
// We continue to let the hart know that we are halted in order that
// a DM which was reset is still made aware that a hart is halted.
// We keep checking both whether there is something the debugger wants
// us to do, or whether we should resume.
entry_loop:
csrr s0, CSR_MHARTID
sw s0, CLEARDEBINT(zero)
check_halt:
csrr s0, CSR_DCSR
andi s0, s0, DCSR_HALT
bnez s0, wait_for_interrupt
exit:
# Restore s0.
csrr s0, CSR_DSCRATCH
dret
_entry:
# Save s0 in DSCRATCH
csrw CSR_DSCRATCH, s0
# Check why we're here
csrr s0, CSR_DCSR
# cause is in bits 8:6 of dcsr
andi s0, s0, DCSR_CAUSE
addi s0, s0, -(DCSR_CAUSE_DEBUGINT<<6)
bnez s0, spontaneous_halt
jdebugram:
# Save s1 so that the debug program can use two registers.
#ifdef MULTI_XLEN
csrr s0, CSR_MISA
#endif
#ifdef RV32
# ifdef MULTI_XLEN
bltz s0, save_not_32
# endif
save_32:
sw s1, (DEBUG_RAM + DEBUG_RAM_SIZE - 4)(zero)
jr zero, DEBUG_RAM
#endif
save_not_32:
#if defined(RV64) && defined(RV128)
slli s0, s0, 1
bltz s0, save_128
#endif
#ifdef RV64
save_64:
sd s1, (DEBUG_RAM + DEBUG_RAM_SIZE - 8)(zero)
jr zero, DEBUG_RAM
#endif
#ifdef RV128
save_128:
sq s1, (DEBUG_RAM + DEBUG_RAM_SIZE - 16)(zero)
jr zero, DEBUG_RAM
#endif
spontaneous_halt:
sw s0, HALTED(zero)
lbu s0, FLAGS(s0) // 1 byte flag per hart. Only one hart advances here.
andi s0, s0, (1 << FLAG_GO)
bnez s0, going
csrr s0, CSR_MHARTID
sw s0, SETHALTNOT(zero)
csrsi CSR_DCSR, DCSR_HALT
wait_for_interrupt:
csrr s0, CSR_DCSR
andi s0, s0, DCSR_DEBUGINT
beqz s0, wait_for_interrupt
lbu s0, FLAGS(s0) // multiple harts can resume here
andi s0, s0, (1 << FLAG_RESUME)
bnez s0, resume
jal zero, entry_loop
_exception:
sw zero, EXCEPTION(zero) // Let debug module know you got an exception.
ebreak
going:
csrr s0, CSR_DSCRATCH // Restore s0 here
sw zero, GOING(zero) // When debug module sees this write, the GO flag is reset.
jalr zero, zero, %lo(whereto) // Rocket-Chip has a specific hack which is that jalr in
// Debug Mode will flush the I-Cache. We need that so that the
// remainder of the variable instructions will be what Debug Module
// intends.
_resume:
csrr s0, CSR_MHARTID
sw s0, RESUMING(zero) // When Debug Module sees this write, the RESUME flag is reset.
csrr s0, CSR_DSCRATCH // Restore s0
dret
j jdebugram
// END OF ACTUAL "ROM" CONTENTS. BELOW IS JUST FOR LINKER SCRIPT.
.section .whereto
whereto:
nop
// Variable "ROM" This is : jal x0 abstract, jal x0 program_buffer,
// or jal x0 resume, as desired.
// Debug Module state machine tracks what is 'desired'.
// We don't need/want to use jalr here because all of the
// Variable ROM contents are set by
// Debug Module before setting the OK_GO byte.

23
debug_rom/debug_rom.h
View File

@ -1,16 +1,11 @@
static const unsigned char debug_rom_raw[] = {
0x6f, 0x00, 0xc0, 0x04, 0x6f, 0x00, 0xc0, 0x00, 0x13, 0x04, 0xf0, 0xff,
0x6f, 0x00, 0x80, 0x00, 0x13, 0x04, 0x00, 0x00, 0x0f, 0x00, 0xf0, 0x0f,
0xf3, 0x24, 0x10, 0x30, 0x63, 0xc6, 0x04, 0x00, 0x83, 0x24, 0xc0, 0x43,
0x6f, 0x00, 0x80, 0x00, 0x83, 0x34, 0x80, 0x43, 0x23, 0x2e, 0x80, 0x42,
0x73, 0x24, 0x40, 0xf1, 0x23, 0x20, 0x80, 0x10, 0x73, 0x24, 0x00, 0x7b,
0x13, 0x74, 0x84, 0x00, 0x63, 0x12, 0x04, 0x04, 0x73, 0x24, 0x20, 0x7b,
0x73, 0x00, 0x20, 0x7b, 0x73, 0x10, 0x24, 0x7b, 0x73, 0x24, 0x00, 0x7b,
0x13, 0x74, 0x04, 0x1c, 0x13, 0x04, 0x04, 0xf4, 0x63, 0x1e, 0x04, 0x00,
0x73, 0x24, 0x10, 0x30, 0x63, 0x46, 0x04, 0x00, 0x23, 0x2e, 0x90, 0x42,
0x67, 0x00, 0x00, 0x40, 0x23, 0x3c, 0x90, 0x42, 0x67, 0x00, 0x00, 0x40,
0x73, 0x24, 0x40, 0xf1, 0x23, 0x26, 0x80, 0x10, 0x73, 0x60, 0x04, 0x7b,
0x73, 0x24, 0x00, 0x7b, 0x13, 0x74, 0x04, 0x02, 0xe3, 0x0c, 0x04, 0xfe,
0x6f, 0xf0, 0x1f, 0xfd
0x6f, 0x00, 0xc0, 0x00, 0x6f, 0x00, 0xc0, 0x04, 0x6f, 0x00, 0x40, 0x03,
0x0f, 0x00, 0xf0, 0x0f, 0x73, 0x10, 0x24, 0x7b, 0x73, 0x24, 0x40, 0xf1,
0x23, 0x20, 0x80, 0x10, 0x03, 0x44, 0x04, 0x40, 0x13, 0x74, 0x14, 0x00,
0x63, 0x10, 0x04, 0x02, 0x73, 0x24, 0x40, 0xf1, 0x03, 0x44, 0x04, 0x40,
0x13, 0x74, 0x24, 0x00, 0xe3, 0x18, 0x04, 0xfc, 0x6f, 0xf0, 0xdf, 0xfd,
0x23, 0x26, 0x00, 0x10, 0x73, 0x00, 0x10, 0x00, 0x73, 0x24, 0x20, 0x7b,
0x23, 0x22, 0x00, 0x10, 0x67, 0x00, 0x00, 0x30, 0x73, 0x24, 0x40, 0xf1,
0x23, 0x24, 0x80, 0x10, 0x73, 0x24, 0x20, 0x7b, 0x73, 0x00, 0x20, 0x7b
};
static const unsigned int debug_rom_raw_len = 148;
static const unsigned int debug_rom_raw_len = 96;

4
debug_rom/link.ld
View File

@ -2,6 +2,10 @@ OUTPUT_ARCH( "riscv" )
ENTRY( entry )
SECTIONS
{
.whereto 0x300 :
{
*(.whereto)
}
. = 0x800;
.text :
{

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