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linux/arch/sh/kernel/kgdb.c
Gustavo A. R. Silva df561f6688 treewide: Use fallthrough pseudo-keyword 
Replace the existing /* fall through */ comments and its variants with
the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary
fall-through markings when it is the case.

[1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
2020-08-23 17:36:59 -05:00

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// SPDX-License-Identifier: GPL-2.0
/*
* SuperH KGDB support
*
* Copyright (C) 2008 - 2012 Paul Mundt
*
* Single stepping taken from the old stub by Henry Bell and Jeremy Siegel.
*/
#include <linux/kgdb.h>
#include <linux/kdebug.h>
#include <linux/irq.h>
#include <linux/io.h>
#include <linux/sched.h>
#include <linux/sched/task_stack.h>
#include <asm/cacheflush.h>
#include <asm/traps.h>
/* Macros for single step instruction identification */
#define OPCODE_BT(op) (((op) & 0xff00) == 0x8900)
#define OPCODE_BF(op) (((op) & 0xff00) == 0x8b00)
#define OPCODE_BTF_DISP(op) (((op) & 0x80) ? (((op) | 0xffffff80) << 1) : \
(((op) & 0x7f ) << 1))
#define OPCODE_BFS(op) (((op) & 0xff00) == 0x8f00)
#define OPCODE_BTS(op) (((op) & 0xff00) == 0x8d00)
#define OPCODE_BRA(op) (((op) & 0xf000) == 0xa000)
#define OPCODE_BRA_DISP(op) (((op) & 0x800) ? (((op) | 0xfffff800) << 1) : \
(((op) & 0x7ff) << 1))
#define OPCODE_BRAF(op) (((op) & 0xf0ff) == 0x0023)
#define OPCODE_BRAF_REG(op) (((op) & 0x0f00) >> 8)
#define OPCODE_BSR(op) (((op) & 0xf000) == 0xb000)
#define OPCODE_BSR_DISP(op) (((op) & 0x800) ? (((op) | 0xfffff800) << 1) : \
(((op) & 0x7ff) << 1))
#define OPCODE_BSRF(op) (((op) & 0xf0ff) == 0x0003)
#define OPCODE_BSRF_REG(op) (((op) >> 8) & 0xf)
#define OPCODE_JMP(op) (((op) & 0xf0ff) == 0x402b)
#define OPCODE_JMP_REG(op) (((op) >> 8) & 0xf)
#define OPCODE_JSR(op) (((op) & 0xf0ff) == 0x400b)
#define OPCODE_JSR_REG(op) (((op) >> 8) & 0xf)
#define OPCODE_RTS(op) ((op) == 0xb)
#define OPCODE_RTE(op) ((op) == 0x2b)
#define SR_T_BIT_MASK 0x1
#define STEP_OPCODE 0xc33d
/* Calculate the new address for after a step */
static short *get_step_address(struct pt_regs *linux_regs)
{
insn_size_t op = __raw_readw(linux_regs->pc);
long addr;
/* BT */
if (OPCODE_BT(op)) {
if (linux_regs->sr & SR_T_BIT_MASK)
addr = linux_regs->pc + 4 + OPCODE_BTF_DISP(op);
else
addr = linux_regs->pc + 2;
}
/* BTS */
else if (OPCODE_BTS(op)) {
if (linux_regs->sr & SR_T_BIT_MASK)
addr = linux_regs->pc + 4 + OPCODE_BTF_DISP(op);
else
addr = linux_regs->pc + 4; /* Not in delay slot */
}
/* BF */
else if (OPCODE_BF(op)) {
if (!(linux_regs->sr & SR_T_BIT_MASK))
addr = linux_regs->pc + 4 + OPCODE_BTF_DISP(op);
else
addr = linux_regs->pc + 2;
}
/* BFS */
else if (OPCODE_BFS(op)) {
if (!(linux_regs->sr & SR_T_BIT_MASK))
addr = linux_regs->pc + 4 + OPCODE_BTF_DISP(op);
else
addr = linux_regs->pc + 4; /* Not in delay slot */
}
/* BRA */
else if (OPCODE_BRA(op))
addr = linux_regs->pc + 4 + OPCODE_BRA_DISP(op);
/* BRAF */
else if (OPCODE_BRAF(op))
addr = linux_regs->pc + 4
+ linux_regs->regs[OPCODE_BRAF_REG(op)];
/* BSR */
else if (OPCODE_BSR(op))
addr = linux_regs->pc + 4 + OPCODE_BSR_DISP(op);
/* BSRF */
else if (OPCODE_BSRF(op))
addr = linux_regs->pc + 4
+ linux_regs->regs[OPCODE_BSRF_REG(op)];
/* JMP */
else if (OPCODE_JMP(op))
addr = linux_regs->regs[OPCODE_JMP_REG(op)];
/* JSR */
else if (OPCODE_JSR(op))
addr = linux_regs->regs[OPCODE_JSR_REG(op)];
/* RTS */
else if (OPCODE_RTS(op))
addr = linux_regs->pr;
/* RTE */
else if (OPCODE_RTE(op))
addr = linux_regs->regs[15];
/* Other */
else
addr = linux_regs->pc + instruction_size(op);
flush_icache_range(addr, addr + instruction_size(op));
return (short *)addr;
}
/*
* Replace the instruction immediately after the current instruction
* (i.e. next in the expected flow of control) with a trap instruction,
* so that returning will cause only a single instruction to be executed.
* Note that this model is slightly broken for instructions with delay
* slots (e.g. B[TF]S, BSR, BRA etc), where both the branch and the
* instruction in the delay slot will be executed.
*/
static unsigned long stepped_address;
static insn_size_t stepped_opcode;
static void do_single_step(struct pt_regs *linux_regs)
{
/* Determine where the target instruction will send us to */
unsigned short *addr = get_step_address(linux_regs);
stepped_address = (int)addr;
/* Replace it */
stepped_opcode = __raw_readw((long)addr);
*addr = STEP_OPCODE;
/* Flush and return */
flush_icache_range((long)addr, (long)addr +
instruction_size(stepped_opcode));
}
/* Undo a single step */
static void undo_single_step(struct pt_regs *linux_regs)
{
/* If we have stepped, put back the old instruction */
/* Use stepped_address in case we stopped elsewhere */
if (stepped_opcode != 0) {
__raw_writew(stepped_opcode, stepped_address);
flush_icache_range(stepped_address, stepped_address + 2);
}
stepped_opcode = 0;
}
struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] = {
{ "r0", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[0]) },
{ "r1", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[1]) },
{ "r2", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[2]) },
{ "r3", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[3]) },
{ "r4", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[4]) },
{ "r5", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[5]) },
{ "r6", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[6]) },
{ "r7", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[7]) },
{ "r8", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[8]) },
{ "r9", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[9]) },
{ "r10", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[10]) },
{ "r11", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[11]) },
{ "r12", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[12]) },
{ "r13", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[13]) },
{ "r14", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[14]) },
{ "r15", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[15]) },
{ "pc", GDB_SIZEOF_REG, offsetof(struct pt_regs, pc) },
{ "pr", GDB_SIZEOF_REG, offsetof(struct pt_regs, pr) },
{ "sr", GDB_SIZEOF_REG, offsetof(struct pt_regs, sr) },
{ "gbr", GDB_SIZEOF_REG, offsetof(struct pt_regs, gbr) },
{ "mach", GDB_SIZEOF_REG, offsetof(struct pt_regs, mach) },
{ "macl", GDB_SIZEOF_REG, offsetof(struct pt_regs, macl) },
{ "vbr", GDB_SIZEOF_REG, -1 },
};
int dbg_set_reg(int regno, void *mem, struct pt_regs *regs)
{
if (regno < 0 || regno >= DBG_MAX_REG_NUM)
return -EINVAL;
if (dbg_reg_def[regno].offset != -1)
memcpy((void *)regs + dbg_reg_def[regno].offset, mem,
dbg_reg_def[regno].size);
return 0;
}
char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs)
{
if (regno >= DBG_MAX_REG_NUM || regno < 0)
return NULL;
if (dbg_reg_def[regno].size != -1)
memcpy(mem, (void *)regs + dbg_reg_def[regno].offset,
dbg_reg_def[regno].size);
switch (regno) {
case GDB_VBR:
__asm__ __volatile__ ("stc vbr, %0" : "=r" (mem));
break;
}
return dbg_reg_def[regno].name;
}
void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
{
struct pt_regs *thread_regs = task_pt_regs(p);
int reg;
/* Initialize to zero */
for (reg = 0; reg < DBG_MAX_REG_NUM; reg++)
gdb_regs[reg] = 0;
/*
* Copy out GP regs 8 to 14.
*
* switch_to() relies on SR.RB toggling, so regs 0->7 are banked
* and need privileged instructions to get to. The r15 value we
* fetch from the thread info directly.
*/
for (reg = GDB_R8; reg < GDB_R15; reg++)
gdb_regs[reg] = thread_regs->regs[reg];
gdb_regs[GDB_R15] = p->thread.sp;
gdb_regs[GDB_PC] = p->thread.pc;
/*
* Additional registers we have context for
*/
gdb_regs[GDB_PR] = thread_regs->pr;
gdb_regs[GDB_GBR] = thread_regs->gbr;
}
int kgdb_arch_handle_exception(int e_vector, int signo, int err_code,
char *remcomInBuffer, char *remcomOutBuffer,
struct pt_regs *linux_regs)
{
unsigned long addr;
char *ptr;
/* Undo any stepping we may have done */
undo_single_step(linux_regs);
switch (remcomInBuffer[0]) {
case 'c':
case 's':
/* try to read optional parameter, pc unchanged if no parm */
ptr = &remcomInBuffer[1];
if (kgdb_hex2long(&ptr, &addr))
linux_regs->pc = addr;
fallthrough;
case 'D':
case 'k':
atomic_set(&kgdb_cpu_doing_single_step, -1);
if (remcomInBuffer[0] == 's') {
do_single_step(linux_regs);
kgdb_single_step = 1;
atomic_set(&kgdb_cpu_doing_single_step,
raw_smp_processor_id());
}
return 0;
}
/* this means that we do not want to exit from the handler: */
return -1;
}
unsigned long kgdb_arch_pc(int exception, struct pt_regs *regs)
{
if (exception == 60)
return instruction_pointer(regs) - 2;
return instruction_pointer(regs);
}
void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long ip)
{
regs->pc = ip;
}
/*
* The primary entry points for the kgdb debug trap table entries.
*/
BUILD_TRAP_HANDLER(singlestep)
{
unsigned long flags;
TRAP_HANDLER_DECL;
local_irq_save(flags);
regs->pc -= instruction_size(__raw_readw(regs->pc - 4));
kgdb_handle_exception(0, SIGTRAP, 0, regs);
local_irq_restore(flags);
}
static int __kgdb_notify(struct die_args *args, unsigned long cmd)
{
int ret;
switch (cmd) {
case DIE_BREAKPOINT:
/*
* This means a user thread is single stepping
* a system call which should be ignored
*/
if (test_thread_flag(TIF_SINGLESTEP))
return NOTIFY_DONE;
ret = kgdb_handle_exception(args->trapnr & 0xff, args->signr,
args->err, args->regs);
if (ret)
return NOTIFY_DONE;
break;
}
return NOTIFY_STOP;
}
static int
kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
{
unsigned long flags;
int ret;
local_irq_save(flags);
ret = __kgdb_notify(ptr, cmd);
local_irq_restore(flags);
return ret;
}
static struct notifier_block kgdb_notifier = {
.notifier_call = kgdb_notify,
/*
* Lowest-prio notifier priority, we want to be notified last:
*/
.priority = -INT_MAX,
};
int kgdb_arch_init(void)
{
return register_die_notifier(&kgdb_notifier);
}
void kgdb_arch_exit(void)
{
unregister_die_notifier(&kgdb_notifier);
}
const struct kgdb_arch arch_kgdb_ops = {
/* Breakpoint instruction: trapa #0x3c */
#ifdef CONFIG_CPU_LITTLE_ENDIAN
.gdb_bpt_instr = { 0x3c, 0xc3 },
#else
.gdb_bpt_instr = { 0xc3, 0x3c },
#endif
};
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