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linux/arch/mn10300/kernel/kgdb.c
David Howells 5141c46c61 MN10300: Emulate single stepping in KGDB on MN10300 
Emulate single stepping in KGDB on MN10300 by way of temporary breakpoint
insertion.  These breakpoints are never actually seen by KGDB, and will overlay
KGDB's own breakpoints.

The breakpoints are removed by switch_to() and reinstalled on switching back so
that if preemption occurs, the preempting task doesn't hit them (though it will
still hit KGDB's regular breakpoints).  If KGDB is reentered for any reason,
then the single step breakpoint is completely erased and must be set again by
the debugger.

We take advantage of the fact that KGDB will effectively halt all other CPUs
whilst this CPU is single-stepping to avoid SMP problems.

If the single-stepping task is preempted and killed without KGDB being
reinvoked, then the breakpoint(s) will be cleared and KGDB will be jumped back
into.

Signed-off-by: David Howells <dhowells@redhat.com>
2011-03-18 16:54:32 +00:00

503 lines
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/* kgdb support for MN10300
*
* Copyright (C) 2010 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public Licence
* as published by the Free Software Foundation; either version
* 2 of the Licence, or (at your option) any later version.
*/
#include <linux/slab.h>
#include <linux/ptrace.h>
#include <linux/kgdb.h>
#include <linux/uaccess.h>
#include <unit/leds.h>
#include <unit/serial.h>
#include <asm/debugger.h>
#include <asm/serial-regs.h>
#include "internal.h"
/*
* Software single-stepping breakpoint save (used by __switch_to())
*/
static struct thread_info *kgdb_sstep_thread;
u8 *kgdb_sstep_bp_addr[2];
u8 kgdb_sstep_bp[2];
/*
* Copy kernel exception frame registers to the GDB register file
*/
void pt_regs_to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *regs)
{
unsigned long ssp = (unsigned long) (regs + 1);
gdb_regs[GDB_FR_D0] = regs->d0;
gdb_regs[GDB_FR_D1] = regs->d1;
gdb_regs[GDB_FR_D2] = regs->d2;
gdb_regs[GDB_FR_D3] = regs->d3;
gdb_regs[GDB_FR_A0] = regs->a0;
gdb_regs[GDB_FR_A1] = regs->a1;
gdb_regs[GDB_FR_A2] = regs->a2;
gdb_regs[GDB_FR_A3] = regs->a3;
gdb_regs[GDB_FR_SP] = (regs->epsw & EPSW_nSL) ? regs->sp : ssp;
gdb_regs[GDB_FR_PC] = regs->pc;
gdb_regs[GDB_FR_MDR] = regs->mdr;
gdb_regs[GDB_FR_EPSW] = regs->epsw;
gdb_regs[GDB_FR_LIR] = regs->lir;
gdb_regs[GDB_FR_LAR] = regs->lar;
gdb_regs[GDB_FR_MDRQ] = regs->mdrq;
gdb_regs[GDB_FR_E0] = regs->e0;
gdb_regs[GDB_FR_E1] = regs->e1;
gdb_regs[GDB_FR_E2] = regs->e2;
gdb_regs[GDB_FR_E3] = regs->e3;
gdb_regs[GDB_FR_E4] = regs->e4;
gdb_regs[GDB_FR_E5] = regs->e5;
gdb_regs[GDB_FR_E6] = regs->e6;
gdb_regs[GDB_FR_E7] = regs->e7;
gdb_regs[GDB_FR_SSP] = ssp;
gdb_regs[GDB_FR_MSP] = 0;
gdb_regs[GDB_FR_USP] = regs->sp;
gdb_regs[GDB_FR_MCRH] = regs->mcrh;
gdb_regs[GDB_FR_MCRL] = regs->mcrl;
gdb_regs[GDB_FR_MCVF] = regs->mcvf;
gdb_regs[GDB_FR_DUMMY0] = 0;
gdb_regs[GDB_FR_DUMMY1] = 0;
gdb_regs[GDB_FR_FS0] = 0;
}
/*
* Extracts kernel SP/PC values understandable by gdb from the values
* saved by switch_to().
*/
void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
{
gdb_regs[GDB_FR_SSP] = p->thread.sp;
gdb_regs[GDB_FR_PC] = p->thread.pc;
gdb_regs[GDB_FR_A3] = p->thread.a3;
gdb_regs[GDB_FR_USP] = p->thread.usp;
gdb_regs[GDB_FR_FPCR] = p->thread.fpu_state.fpcr;
}
/*
* Fill kernel exception frame registers from the GDB register file
*/
void gdb_regs_to_pt_regs(unsigned long *gdb_regs, struct pt_regs *regs)
{
regs->d0 = gdb_regs[GDB_FR_D0];
regs->d1 = gdb_regs[GDB_FR_D1];
regs->d2 = gdb_regs[GDB_FR_D2];
regs->d3 = gdb_regs[GDB_FR_D3];
regs->a0 = gdb_regs[GDB_FR_A0];
regs->a1 = gdb_regs[GDB_FR_A1];
regs->a2 = gdb_regs[GDB_FR_A2];
regs->a3 = gdb_regs[GDB_FR_A3];
regs->sp = gdb_regs[GDB_FR_SP];
regs->pc = gdb_regs[GDB_FR_PC];
regs->mdr = gdb_regs[GDB_FR_MDR];
regs->epsw = gdb_regs[GDB_FR_EPSW];
regs->lir = gdb_regs[GDB_FR_LIR];
regs->lar = gdb_regs[GDB_FR_LAR];
regs->mdrq = gdb_regs[GDB_FR_MDRQ];
regs->e0 = gdb_regs[GDB_FR_E0];
regs->e1 = gdb_regs[GDB_FR_E1];
regs->e2 = gdb_regs[GDB_FR_E2];
regs->e3 = gdb_regs[GDB_FR_E3];
regs->e4 = gdb_regs[GDB_FR_E4];
regs->e5 = gdb_regs[GDB_FR_E5];
regs->e6 = gdb_regs[GDB_FR_E6];
regs->e7 = gdb_regs[GDB_FR_E7];
regs->sp = gdb_regs[GDB_FR_SSP];
/* gdb_regs[GDB_FR_MSP]; */
// regs->usp = gdb_regs[GDB_FR_USP];
regs->mcrh = gdb_regs[GDB_FR_MCRH];
regs->mcrl = gdb_regs[GDB_FR_MCRL];
regs->mcvf = gdb_regs[GDB_FR_MCVF];
/* gdb_regs[GDB_FR_DUMMY0]; */
/* gdb_regs[GDB_FR_DUMMY1]; */
// regs->fpcr = gdb_regs[GDB_FR_FPCR];
// regs->fs0 = gdb_regs[GDB_FR_FS0];
}
struct kgdb_arch arch_kgdb_ops = {
.gdb_bpt_instr = { 0xff },
.flags = KGDB_HW_BREAKPOINT,
};
static const unsigned char mn10300_kgdb_insn_sizes[256] =
{
/* 1 2 3 4 5 6 7 8 9 a b c d e f */
1, 3, 3, 3, 1, 3, 3, 3, 1, 3, 3, 3, 1, 3, 3, 3, /* 0 */
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, /* 1 */
2, 2, 2, 2, 3, 3, 3, 3, 2, 2, 2, 2, 3, 3, 3, 3, /* 2 */
3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 1, 1, 1, 1, /* 3 */
1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, /* 4 */
1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, /* 5 */
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, /* 6 */
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, /* 7 */
2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, /* 8 */
2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, /* 9 */
2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, /* a */
2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, /* b */
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 2, 2, /* c */
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* d */
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, /* e */
0, 2, 2, 2, 2, 2, 2, 4, 0, 3, 0, 4, 0, 6, 7, 1 /* f */
};
/*
* Attempt to emulate single stepping by means of breakpoint instructions.
* Although there is a single-step trace flag in EPSW, its use is not
* sufficiently documented and is only intended for use with the JTAG debugger.
*/
static int kgdb_arch_do_singlestep(struct pt_regs *regs)
{
unsigned long arg;
unsigned size;
u8 *pc = (u8 *)regs->pc, *sp = (u8 *)(regs + 1), cur;
u8 *x = NULL, *y = NULL;
int ret;
ret = probe_kernel_read(&cur, pc, 1);
if (ret < 0)
return ret;
size = mn10300_kgdb_insn_sizes[cur];
if (size > 0) {
x = pc + size;
goto set_x;
}
switch (cur) {
/* Bxx (d8,PC) */
case 0xc0 ... 0xca:
ret = probe_kernel_read(&arg, pc + 1, 1);
if (ret < 0)
return ret;
x = pc + 2;
if (arg >= 0 && arg <= 2)
goto set_x;
y = pc + (s8)arg;
goto set_x_and_y;
/* LXX (d8,PC) */
case 0xd0 ... 0xda:
x = pc + 1;
if (regs->pc == regs->lar)
goto set_x;
y = (u8 *)regs->lar;
goto set_x_and_y;
/* SETLB - loads the next four bytes into the LIR register
* (which mustn't include a breakpoint instruction) */
case 0xdb:
x = pc + 5;
goto set_x;
/* JMP (d16,PC) or CALL (d16,PC) */
case 0xcc:
case 0xcd:
ret = probe_kernel_read(&arg, pc + 1, 2);
if (ret < 0)
return ret;
x = pc + (s16)arg;
goto set_x;
/* JMP (d32,PC) or CALL (d32,PC) */
case 0xdc:
case 0xdd:
ret = probe_kernel_read(&arg, pc + 1, 4);
if (ret < 0)
return ret;
x = pc + (s32)arg;
goto set_x;
/* RETF */
case 0xde:
x = (u8 *)regs->mdr;
goto set_x;
/* RET */
case 0xdf:
ret = probe_kernel_read(&arg, pc + 2, 1);
if (ret < 0)
return ret;
ret = probe_kernel_read(&x, sp + (s8)arg, 4);
if (ret < 0)
return ret;
goto set_x;
case 0xf0:
ret = probe_kernel_read(&cur, pc + 1, 1);
if (ret < 0)
return ret;
if (cur >= 0xf0 && cur <= 0xf7) {
/* JMP (An) / CALLS (An) */
switch (cur & 3) {
case 0: x = (u8 *)regs->a0; break;
case 1: x = (u8 *)regs->a1; break;
case 2: x = (u8 *)regs->a2; break;
case 3: x = (u8 *)regs->a3; break;
}
goto set_x;
} else if (cur == 0xfc) {
/* RETS */
ret = probe_kernel_read(&x, sp, 4);
if (ret < 0)
return ret;
goto set_x;
} else if (cur == 0xfd) {
/* RTI */
ret = probe_kernel_read(&x, sp + 4, 4);
if (ret < 0)
return ret;
goto set_x;
} else {
x = pc + 2;
goto set_x;
}
break;
/* potential 3-byte conditional branches */
case 0xf8:
ret = probe_kernel_read(&cur, pc + 1, 1);
if (ret < 0)
return ret;
x = pc + 3;
if (cur >= 0xe8 && cur <= 0xeb) {
ret = probe_kernel_read(&arg, pc + 2, 1);
if (ret < 0)
return ret;
if (arg >= 0 && arg <= 3)
goto set_x;
y = pc + (s8)arg;
goto set_x_and_y;
}
goto set_x;
case 0xfa:
ret = probe_kernel_read(&cur, pc + 1, 1);
if (ret < 0)
return ret;
if (cur == 0xff) {
/* CALLS (d16,PC) */
ret = probe_kernel_read(&arg, pc + 2, 2);
if (ret < 0)
return ret;
x = pc + (s16)arg;
goto set_x;
}
x = pc + 4;
goto set_x;
case 0xfc:
ret = probe_kernel_read(&cur, pc + 1, 1);
if (ret < 0)
return ret;
if (cur == 0xff) {
/* CALLS (d32,PC) */
ret = probe_kernel_read(&arg, pc + 2, 4);
if (ret < 0)
return ret;
x = pc + (s32)arg;
goto set_x;
}
x = pc + 6;
goto set_x;
}
return 0;
set_x:
kgdb_sstep_bp_addr[0] = x;
kgdb_sstep_bp_addr[1] = NULL;
ret = probe_kernel_read(&kgdb_sstep_bp[0], x, 1);
if (ret < 0)
return ret;
ret = probe_kernel_write(x, &arch_kgdb_ops.gdb_bpt_instr, 1);
if (ret < 0)
return ret;
kgdb_sstep_thread = current_thread_info();
debugger_local_cache_flushinv_one(x);
return ret;
set_x_and_y:
kgdb_sstep_bp_addr[0] = x;
kgdb_sstep_bp_addr[1] = y;
ret = probe_kernel_read(&kgdb_sstep_bp[0], x, 1);
if (ret < 0)
return ret;
ret = probe_kernel_read(&kgdb_sstep_bp[1], y, 1);
if (ret < 0)
return ret;
ret = probe_kernel_write(x, &arch_kgdb_ops.gdb_bpt_instr, 1);
if (ret < 0)
return ret;
ret = probe_kernel_write(y, &arch_kgdb_ops.gdb_bpt_instr, 1);
if (ret < 0) {
probe_kernel_write(kgdb_sstep_bp_addr[0],
&kgdb_sstep_bp[0], 1);
} else {
kgdb_sstep_thread = current_thread_info();
}
debugger_local_cache_flushinv_one(x);
debugger_local_cache_flushinv_one(y);
return ret;
}
/*
* Remove emplaced single-step breakpoints, returning true if we hit one of
* them.
*/
static bool kgdb_arch_undo_singlestep(struct pt_regs *regs)
{
bool hit = false;
u8 *x = kgdb_sstep_bp_addr[0], *y = kgdb_sstep_bp_addr[1];
u8 opcode;
if (kgdb_sstep_thread == current_thread_info()) {
if (x) {
if (x == (u8 *)regs->pc)
hit = true;
if (probe_kernel_read(&opcode, x,
1) < 0 ||
opcode != 0xff)
BUG();
probe_kernel_write(x, &kgdb_sstep_bp[0], 1);
debugger_local_cache_flushinv_one(x);
}
if (y) {
if (y == (u8 *)regs->pc)
hit = true;
if (probe_kernel_read(&opcode, y,
1) < 0 ||
opcode != 0xff)
BUG();
probe_kernel_write(y, &kgdb_sstep_bp[1], 1);
debugger_local_cache_flushinv_one(y);
}
}
kgdb_sstep_bp_addr[0] = NULL;
kgdb_sstep_bp_addr[1] = NULL;
kgdb_sstep_thread = NULL;
return hit;
}
/*
* Catch a single-step-pending thread being deleted and make sure the global
* single-step state is cleared. At this point the breakpoints should have
* been removed by __switch_to().
*/
void free_thread_info(struct thread_info *ti)
{
if (kgdb_sstep_thread == ti) {
kgdb_sstep_thread = NULL;
/* However, we may now be running in degraded mode, with most
* of the CPUs disabled until such a time as KGDB is reentered,
* so force immediate reentry */
kgdb_breakpoint();
}
kfree(ti);
}
/*
* Handle unknown packets and [CcsDk] packets
* - at this point breakpoints have been installed
*/
int kgdb_arch_handle_exception(int vector, int signo, int err_code,
char *remcom_in_buffer, char *remcom_out_buffer,
struct pt_regs *regs)
{
long addr;
char *ptr;
switch (remcom_in_buffer[0]) {
case 'c':
case 's':
/* try to read optional parameter, pc unchanged if no parm */
ptr = &remcom_in_buffer[1];
if (kgdb_hex2long(&ptr, &addr))
regs->pc = addr;
case 'D':
case 'k':
atomic_set(&kgdb_cpu_doing_single_step, -1);
if (remcom_in_buffer[0] == 's') {
kgdb_arch_do_singlestep(regs);
kgdb_single_step = 1;
atomic_set(&kgdb_cpu_doing_single_step,
raw_smp_processor_id());
}
return 0;
}
return -1; /* this means that we do not want to exit from the handler */
}
/*
* Handle event interception
* - returns 0 if the exception should be skipped, -ERROR otherwise.
*/
int debugger_intercept(enum exception_code excep, int signo, int si_code,
struct pt_regs *regs)
{
int ret;
if (kgdb_arch_undo_singlestep(regs)) {
excep = EXCEP_TRAP;
signo = SIGTRAP;
si_code = TRAP_TRACE;
}
ret = kgdb_handle_exception(excep, signo, si_code, regs);
debugger_local_cache_flushinv();
return ret;
}
/*
* Determine if we've hit a debugger special breakpoint
*/
int at_debugger_breakpoint(struct pt_regs *regs)
{
return regs->pc == (unsigned long)&__arch_kgdb_breakpoint;
}
/*
* Initialise kgdb
*/
int kgdb_arch_init(void)
{
return 0;
}
/*
* Do something, perhaps, but don't know what.
*/
void kgdb_arch_exit(void)
{
}
#ifdef CONFIG_SMP
void debugger_nmi_interrupt(struct pt_regs *regs, enum exception_code code)
{
kgdb_nmicallback(arch_smp_processor_id(), regs);
debugger_local_cache_flushinv();
}
void kgdb_roundup_cpus(unsigned long flags)
{
smp_jump_to_debugger();
}
#endif
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