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mips: add native backtrace implementation

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Should make debugging crashes on native MIPS targets far easier.
This is by no means a 100% complete or robust implementation but
it seems to handle the vast majority of functions.

Change-Id: Id5f430270e02b5092b79026b6876675c784aa649
This commit is contained in:
Aidan MacDonald 2022-05-16 14:33:26 +01:00
parent cade488b08
commit 981e972839
9 changed files with 357 additions and 3 deletions
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3
firmware/export/backtrace.h
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@ -25,6 +25,9 @@
#ifdef BACKTRACE_UNWARMINDER #ifdef BACKTRACE_UNWARMINDER
#include "backtrace-unwarminder.h" #include "backtrace-unwarminder.h"
#endif #endif
#ifdef BACKTRACE_MIPSUNWINDER
#include "backtrace-mipsunwinder.h"
#endif
/* Print a backtrace using lcd_* functions, starting at the given line and updating /* Print a backtrace using lcd_* functions, starting at the given line and updating
* the line number. On targets that support it (typically native targets), the * the line number. On targets that support it (typically native targets), the

3
firmware/export/system.h
View file

@ -258,7 +258,8 @@ static inline void cpu_boost_unlock(void)
#endif #endif
/* Define this if target has support for generating backtraces */ /* Define this if target has support for generating backtraces */
#ifdef CPU_ARM #if defined(CPU_ARM) || \
(defined(CPU_MIPS) && (CONFIG_PLATFORM & PLATFORM_NATIVE))
#define HAVE_RB_BACKTRACE #define HAVE_RB_BACKTRACE
#endif #endif

10
firmware/panic.c
View file

@ -32,9 +32,9 @@
#include "system.h" #include "system.h"
#include "logf.h" #include "logf.h"
#if defined(CPU_ARM) #ifdef HAVE_RB_BACKTRACE
#include "gcc_extensions.h" #include "gcc_extensions.h"
#include <backtrace.h> #include "backtrace.h"
#endif #endif
static char panic_buf[128]; static char panic_buf[128];
@ -65,6 +65,12 @@ void panicf_f( const char *fmt, ...)
); );
int pc = (int)__builtin_return_address(0); int pc = (int)__builtin_return_address(0);
#elif defined(BACKTRACE_MIPSUNWINDER)
void panicf( const char *fmt, ... )
{
/* NOTE: these are obtained by the backtrace lib */
const int pc = 0;
const int sp = 0;
#else #else
void panicf( const char *fmt, ...) void panicf( const char *fmt, ...)
{ {

2
lib/mipsunwinder/SOURCES Normal file
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@ -0,0 +1,2 @@
backtrace-mips32.c
init_context_32.S

236
lib/mipsunwinder/backtrace-mips32.c Normal file
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@ -0,0 +1,236 @@
/***************************************************************************
* __________ __ ___.
* Open \______ \ ____ ____ | | _\_ |__ _______ ___
* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
* \/ \/ \/ \/ \/
* $Id$
*
* MIPS32 backtrace implementation
* Copyright (C) 2022 Aidan MacDonald
*
* References:
* https://yosefk.com/blog/getting-the-call-stack-without-a-frame-pointer.html
* https://elinux.org/images/6/68/ELC2008_-_Back-tracing_in_MIPS-based_Linux_Systems.pdf
* System V ABI MIPS Supplement, 3rd edition
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
* KIND, either express or implied.
*
****************************************************************************/
#include "backtrace.h"
#include "lcd.h"
#include <stdint.h>
#include <stdbool.h>
#include <stdalign.h>
#include <stdarg.h>
#include <stdio.h>
#define MIN_ADDR 0x80000000ul
#define MAX_ADDR (MIN_ADDR + (MEMORYSIZE * 1024 * 1024) - 1)
static bool read_check(const void* addr, size_t alignment)
{
if(addr < (const void*)MIN_ADDR ||
addr > (const void*)MAX_ADDR)
return false;
if((uintptr_t)addr & (alignment - 1))
return false;
return true;
}
static bool read32(const void* addr, uint32_t* val)
{
if(!read_check(addr, alignof(uint32_t)))
return false;
*val = *(const uint32_t*)addr;
return true;
}
#if 0
static bool read16(const void* addr, uint16_t* val)
{
if(!read_check(addr, alignof(uint16_t)))
return false;
*val = *(const uint16_t*)addr;
return true;
}
static bool read8(const void* addr, uint8_t* val)
{
if(!read_check(addr, alignof(uint8_t)))
return false;
*val = *(const uint8_t*)addr;
return true;
}
#endif
static long extract_s16(uint32_t val)
{
#if 1
/* not ISO C, but gets GCC to emit 'seh' which is more compact */
return (int32_t)(val << 16) >> 16;
#else
val &= 0xffff;
if(val > 0x7fff)
return (long)val - 0x10000l;
else
return val;
#endif
}
/* TODO - cases not handled by the backtrace algorithm
*
* 1. functions that save the frame pointer will not be handled correctly
* (need to implement the algorithm specified by the System V ABI).
*
* 2. GCC can generate functions with a "false" stack pointer decrement,
* for some examples see read_bmp_fd and walk_path. those functions
* seem to be more difficult to deal with and the SysV algorithm will
* also get confused by them, but they are not common.
*/
int mips_bt_step(struct mips_bt_context* ctx)
{
/* go backward and look for the stack pointer decrement */
uint32_t* pc = ctx->pc;
uint32_t insn;
long sp_off;
while(true) {
if(!read32(pc, &insn))
return 0;
/* addiu sp, sp, sp_off */
if((insn >> 16) == 0x27bd) {
sp_off = extract_s16(insn);
if(sp_off < 0)
break;
}
/* jr ra */
if(insn == 0x03e00008) {
/* end if this is not a leaf or we lack register info */
if(ctx->depth > 0 || !(ctx->valid & (1 << MIPSBT_RA))) {
mips_bt_debug(ctx, "unexpected leaf function");
return 0;
}
/* this is a leaf function - ra contains the return address
* and sp is unchanged */
ctx->pc = (void*)ctx->reg[MIPSBT_RA] - 8;
ctx->depth++;
return 1;
}
--pc;
}
mips_bt_debug(ctx, "found sp_off=%ld at %p", sp_off, pc);
/* now go forward and find the saved return address */
while((void*)pc < ctx->pc) {
if(!read32(pc, &insn))
return 0;
/* sw ra, ra_off(sp) */
if((insn >> 16) == 0xafbf) {
long ra_off = extract_s16(insn);
uint32_t save_ra;
/* load the saved return address */
mips_bt_debug(ctx, "load ra from %p+%ld", ctx->sp, ra_off);
if(!read32(ctx->sp + ra_off, &save_ra))
return 0;
if(save_ra == 0) {
mips_bt_debug("hit root");
return 0;
}
/* update bt context */
ctx->pc = (void*)save_ra - 8;
ctx->sp -= sp_off;
/* update saved register info */
ctx->reg[MIPSBT_RA] = save_ra;
ctx->valid |= (1 << MIPSBT_RA);
ctx->depth++;
return 1;
}
++pc;
}
/* sometimes an exception occurs before ra is saved - in this case
* the ra register should contain the caller PC, but we still need
* to adjust the stack frame. */
if(ctx->depth == 0 && (ctx->valid & (1 << MIPSBT_RA))) {
ctx->pc = (void*)ctx->reg[MIPSBT_RA] - 8;
ctx->sp -= sp_off;
ctx->depth++;
return 1;
}
mips_bt_debug(ctx, "ra not found");
return 0;
}
#ifdef MIPSUNWINDER_DEBUG
static void rb_backtrace_debugf(void* arg, const char* fmt, ...)
{
static char buf[64];
va_list ap;
va_start(ap, fmt);
vsnprintf(buf, sizeof(buf), fmt, ap);
va_end(ap);
unsigned int* line = arg;
lcd_putsf(4, (*line)++, "%s", buf);
lcd_update();
}
#endif
void rb_backtrace_ctx(void* arg, unsigned* line)
{
struct mips_bt_context* ctx = arg;
#ifdef MIPSUNWINDER_DEBUG
ctx->debugf = rb_backtrace_debugf;
ctx->debug_arg = line;
#endif
do {
lcd_putsf(0, (*line)++, "%02d pc:%08lx sp:%08lx",
ctx->depth, (unsigned long)ctx->pc, (unsigned long)ctx->sp);
lcd_update();
} while(mips_bt_step(ctx));
lcd_puts(0, (*line)++, "bt end");
lcd_update();
}
void rb_backtrace(int pcAddr, int spAddr, unsigned* line)
{
(void)pcAddr;
(void)spAddr;
struct mips_bt_context ctx;
mips_bt_start(&ctx);
mips_bt_step(&ctx); /* step over this function */
rb_backtrace_ctx(&ctx, line);
}

65
lib/mipsunwinder/backtrace-mipsunwinder.h Normal file
View file

@ -0,0 +1,65 @@
/***************************************************************************
* __________ __ ___.
* Open \______ \ ____ ____ | | _\_ |__ _______ ___
* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
* \/ \/ \/ \/ \/
* $Id$
*
* Copyright (C) 2022 Aidan MacDonald
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
* KIND, either express or implied.
*
****************************************************************************/
#ifndef BACKTRACE_MIPSUNWINDER_H
#define BACKTRACE_MIPSUNWINDER_H
/*#define MIPSUNWINDER_DEBUG*/
#include <stdint.h>
enum {
MIPSBT_RA,
MIPSBT_NREG,
};
struct mips_bt_context {
void* pc;
void* sp;
int depth;
uint32_t valid;
uint32_t reg[MIPSBT_NREG];
#ifdef MIPSUNWINDER_DEBUG
void(*debugf)(void*, const char*, ...);
void* debug_arg;
#endif
};
int mips_bt_step(struct mips_bt_context* ctx);
void mips_bt_start(struct mips_bt_context* ctx);
#ifdef MIPSUNWINDER_DEBUG
# define mips_bt_debug(ctx, ...) \
do { struct mips_bt_context* __ctx = ctx; \
if(__ctx->debugf) \
__ctx->debugf(__ctx->debug_arg, __VA_ARGS__);\
} while(0)
#else
# define mips_bt_debug(...) do { } while(0)
#endif
/* NOTE: ignores pcAddr and spAddr, backtrace starts from caller */
void rb_backtrace(int pcAddr, int spAddr, unsigned* line);
/* given struct mips_bt_context argument, print stack traceback */
void rb_backtrace_ctx(void* arg, unsigned* line);
#endif /* BACKTRACE_MIPSUNWINDER_H */

12
lib/mipsunwinder/init_context_32.S Normal file
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@ -0,0 +1,12 @@
#include "mips.h"
.text
.global mips_bt_start
mips_bt_start:
addiu v0, ra, -8
sw v0, 0(a0) /* ctx->pc = ra - 8 */
sw sp, 4(a0) /* ctx->sp = sp */
sw zero, 8(a0) /* ctx->depth = 0 */
sw zero, 12(a0) /* ctx->valid = 0 */
jr ra

23
lib/mipsunwinder/mipsunwinder.make Normal file
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@ -0,0 +1,23 @@
# __________ __ ___.
# Open \______ \ ____ ____ | | _\_ |__ _______ ___
# Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
# Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
# Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
# \/ \/ \/ \/ \/
#
MIPSUNWINDERLIB_DIR = $(ROOTDIR)/lib/mipsunwinder
MIPSUNWINDERLIB_SRC = $(call preprocess, $(MIPSUNWINDERLIB_DIR)/SOURCES)
MIPSUNWINDERLIB_OBJ := $(call c2obj, $(MIPSUNWINDERLIB_SRC))
OTHER_SRC += $(MIPSUNWINDERLIB_SRC)
MIPSUNWINDERLIB = $(BUILDDIR)/lib/libmipsunwinder.a
CORE_LIBS += $(MIPSUNWINDERLIB)
INCLUDES += -I$(MIPSUNWINDERLIB_DIR)
DEFINES += -DBACKTRACE_MIPSUNWINDER
$(MIPSUNWINDERLIB): $(MIPSUNWINDERLIB_OBJ)
$(SILENT)$(shell rm -f $@)
$(call PRINTS,AR $(@F))$(AR) rcs $@ $^ >/dev/null

6
tools/root.make
View file

@ -75,6 +75,12 @@ ifeq (,$(findstring checkwps,$(APP_TYPE)))
include $(ROOTDIR)/lib/unwarminder/unwarminder.make include $(ROOTDIR)/lib/unwarminder/unwarminder.make
endif endif
endif endif
ifeq (arch_mips,$(ARCH))
# mips unwinder is only usable on native ports
ifeq (,$(APP_TYPE))
include $(ROOTDIR)/lib/mipsunwinder/mipsunwinder.make
endif
endif
ifeq (,$(findstring bootloader,$(APPSDIR))) ifeq (,$(findstring bootloader,$(APPSDIR)))
include $(ROOTDIR)/lib/skin_parser/skin_parser.make include $(ROOTDIR)/lib/skin_parser/skin_parser.make
include $(ROOTDIR)/lib/tlsf/libtlsf.make include $(ROOTDIR)/lib/tlsf/libtlsf.make