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Merge branch 'kgdb-fixes' of git://git.kernel.org/pub/scm/linux/kerne…
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…l/git/jwessel/linux-2.6-kgdb

* 'kgdb-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jwessel/linux-2.6-kgdb:
  kgdb: Turn off tracing while in the debugger
  kgdb: use atomic_inc and atomic_dec instead of atomic_set
  kgdb: eliminate kgdb_wait(), all cpus enter the same way
  kgdbts,sh: Add in breakpoint pc offset for superh
  kgdb: have ebin2mem call probe_kernel_write once
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Linus Torvalds committed Apr 3, 2010
2 parents 24b99d1 + 4da75b9 commit 5e123e5
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Showing 2 changed files with 109 additions and 102 deletions.
6 changes: 6 additions & 0 deletions drivers/misc/kgdbts.c
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Original file line number Diff line number Diff line change
Expand Up @@ -295,6 +295,10 @@ static int check_and_rewind_pc(char *put_str, char *arg)
/* On x86 a breakpoint stop requires it to be decremented */
if (addr + 1 == kgdbts_regs.ip)
offset = -1;
#elif defined(CONFIG_SUPERH)
/* On SUPERH a breakpoint stop requires it to be decremented */
if (addr + 2 == kgdbts_regs.pc)
offset = -2;
#endif
if (strcmp(arg, "silent") &&
instruction_pointer(&kgdbts_regs) + offset != addr) {
Expand All @@ -305,6 +309,8 @@ static int check_and_rewind_pc(char *put_str, char *arg)
#ifdef CONFIG_X86
/* On x86 adjust the instruction pointer if needed */
kgdbts_regs.ip += offset;
#elif defined(CONFIG_SUPERH)
kgdbts_regs.pc += offset;
#endif
return 0;
}
Expand Down
205 changes: 103 additions & 102 deletions kernel/kgdb.c
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Original file line number Diff line number Diff line change
Expand Up @@ -69,9 +69,16 @@ struct kgdb_state {
struct pt_regs *linux_regs;
};

/* Exception state values */
#define DCPU_WANT_MASTER 0x1 /* Waiting to become a master kgdb cpu */
#define DCPU_NEXT_MASTER 0x2 /* Transition from one master cpu to another */
#define DCPU_IS_SLAVE 0x4 /* Slave cpu enter exception */
#define DCPU_SSTEP 0x8 /* CPU is single stepping */

static struct debuggerinfo_struct {
void *debuggerinfo;
struct task_struct *task;
int exception_state;
} kgdb_info[NR_CPUS];

/**
Expand Down Expand Up @@ -391,27 +398,22 @@ int kgdb_mem2hex(char *mem, char *buf, int count)

/*
* Copy the binary array pointed to by buf into mem. Fix $, #, and
* 0x7d escaped with 0x7d. Return a pointer to the character after
* the last byte written.
* 0x7d escaped with 0x7d. Return -EFAULT on failure or 0 on success.
* The input buf is overwitten with the result to write to mem.
*/
static int kgdb_ebin2mem(char *buf, char *mem, int count)
{
int err = 0;
char c;
int size = 0;
char *c = buf;

while (count-- > 0) {
c = *buf++;
if (c == 0x7d)
c = *buf++ ^ 0x20;

err = probe_kernel_write(mem, &c, 1);
if (err)
break;

mem++;
c[size] = *buf++;
if (c[size] == 0x7d)
c[size] = *buf++ ^ 0x20;
size++;
}

return err;
return probe_kernel_write(mem, c, size);
}

/*
Expand Down Expand Up @@ -562,49 +564,6 @@ static struct task_struct *getthread(struct pt_regs *regs, int tid)
return find_task_by_pid_ns(tid, &init_pid_ns);
}

/*
* CPU debug state control:
*/

#ifdef CONFIG_SMP
static void kgdb_wait(struct pt_regs *regs)
{
unsigned long flags;
int cpu;

local_irq_save(flags);
cpu = raw_smp_processor_id();
kgdb_info[cpu].debuggerinfo = regs;
kgdb_info[cpu].task = current;
/*
* Make sure the above info reaches the primary CPU before
* our cpu_in_kgdb[] flag setting does:
*/
smp_wmb();
atomic_set(&cpu_in_kgdb[cpu], 1);

/* Disable any cpu specific hw breakpoints */
kgdb_disable_hw_debug(regs);

/* Wait till primary CPU is done with debugging */
while (atomic_read(&passive_cpu_wait[cpu]))
cpu_relax();

kgdb_info[cpu].debuggerinfo = NULL;
kgdb_info[cpu].task = NULL;

/* fix up hardware debug registers on local cpu */
if (arch_kgdb_ops.correct_hw_break)
arch_kgdb_ops.correct_hw_break();

/* Signal the primary CPU that we are done: */
atomic_set(&cpu_in_kgdb[cpu], 0);
touch_softlockup_watchdog_sync();
clocksource_touch_watchdog();
local_irq_restore(flags);
}
#endif

/*
* Some architectures need cache flushes when we set/clear a
* breakpoint:
Expand Down Expand Up @@ -1400,48 +1359,57 @@ static int kgdb_reenter_check(struct kgdb_state *ks)
return 1;
}

/*
* kgdb_handle_exception() - main entry point from a kernel exception
*
* Locking hierarchy:
* interface locks, if any (begin_session)
* kgdb lock (kgdb_active)
*/
int
kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs)
{
struct kgdb_state kgdb_var;
struct kgdb_state *ks = &kgdb_var;
unsigned long flags;
int sstep_tries = 100;
int error = 0;
int i, cpu;

ks->cpu = raw_smp_processor_id();
ks->ex_vector = evector;
ks->signo = signo;
ks->ex_vector = evector;
ks->err_code = ecode;
ks->kgdb_usethreadid = 0;
ks->linux_regs = regs;

if (kgdb_reenter_check(ks))
return 0; /* Ouch, double exception ! */

int trace_on = 0;
acquirelock:
/*
* Interrupts will be restored by the 'trap return' code, except when
* single stepping.
*/
local_irq_save(flags);

cpu = raw_smp_processor_id();
cpu = ks->cpu;
kgdb_info[cpu].debuggerinfo = regs;
kgdb_info[cpu].task = current;
/*
* Make sure the above info reaches the primary CPU before
* our cpu_in_kgdb[] flag setting does:
*/
atomic_inc(&cpu_in_kgdb[cpu]);

/*
* Acquire the kgdb_active lock:
* CPU will loop if it is a slave or request to become a kgdb
* master cpu and acquire the kgdb_active lock:
*/
while (atomic_cmpxchg(&kgdb_active, -1, cpu) != -1)
while (1) {
if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) {
if (atomic_cmpxchg(&kgdb_active, -1, cpu) == cpu)
break;
} else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) {
if (!atomic_read(&passive_cpu_wait[cpu]))
goto return_normal;
} else {
return_normal:
/* Return to normal operation by executing any
* hw breakpoint fixup.
*/
if (arch_kgdb_ops.correct_hw_break)
arch_kgdb_ops.correct_hw_break();
if (trace_on)
tracing_on();
atomic_dec(&cpu_in_kgdb[cpu]);
touch_softlockup_watchdog_sync();
clocksource_touch_watchdog();
local_irq_restore(flags);
return 0;
}
cpu_relax();
}

/*
* For single stepping, try to only enter on the processor
Expand Down Expand Up @@ -1475,9 +1443,6 @@ kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
if (kgdb_io_ops->pre_exception)
kgdb_io_ops->pre_exception();

kgdb_info[ks->cpu].debuggerinfo = ks->linux_regs;
kgdb_info[ks->cpu].task = current;

kgdb_disable_hw_debug(ks->linux_regs);

/*
Expand All @@ -1486,15 +1451,9 @@ kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
*/
if (!kgdb_single_step) {
for (i = 0; i < NR_CPUS; i++)
atomic_set(&passive_cpu_wait[i], 1);
atomic_inc(&passive_cpu_wait[i]);
}

/*
* spin_lock code is good enough as a barrier so we don't
* need one here:
*/
atomic_set(&cpu_in_kgdb[ks->cpu], 1);

#ifdef CONFIG_SMP
/* Signal the other CPUs to enter kgdb_wait() */
if ((!kgdb_single_step) && kgdb_do_roundup)
Expand All @@ -1518,6 +1477,9 @@ kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
kgdb_single_step = 0;
kgdb_contthread = current;
exception_level = 0;
trace_on = tracing_is_on();
if (trace_on)
tracing_off();

/* Talk to debugger with gdbserial protocol */
error = gdb_serial_stub(ks);
Expand All @@ -1526,13 +1488,11 @@ kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
if (kgdb_io_ops->post_exception)
kgdb_io_ops->post_exception();

kgdb_info[ks->cpu].debuggerinfo = NULL;
kgdb_info[ks->cpu].task = NULL;
atomic_set(&cpu_in_kgdb[ks->cpu], 0);
atomic_dec(&cpu_in_kgdb[ks->cpu]);

if (!kgdb_single_step) {
for (i = NR_CPUS-1; i >= 0; i--)
atomic_set(&passive_cpu_wait[i], 0);
atomic_dec(&passive_cpu_wait[i]);
/*
* Wait till all the CPUs have quit
* from the debugger.
Expand All @@ -1551,6 +1511,8 @@ kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
else
kgdb_sstep_pid = 0;
}
if (trace_on)
tracing_on();
/* Free kgdb_active */
atomic_set(&kgdb_active, -1);
touch_softlockup_watchdog_sync();
Expand All @@ -1560,13 +1522,52 @@ kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
return error;
}

/*
* kgdb_handle_exception() - main entry point from a kernel exception
*
* Locking hierarchy:
* interface locks, if any (begin_session)
* kgdb lock (kgdb_active)
*/
int
kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
{
struct kgdb_state kgdb_var;
struct kgdb_state *ks = &kgdb_var;
int ret;

ks->cpu = raw_smp_processor_id();
ks->ex_vector = evector;
ks->signo = signo;
ks->ex_vector = evector;
ks->err_code = ecode;
ks->kgdb_usethreadid = 0;
ks->linux_regs = regs;

if (kgdb_reenter_check(ks))
return 0; /* Ouch, double exception ! */
kgdb_info[ks->cpu].exception_state |= DCPU_WANT_MASTER;
ret = kgdb_cpu_enter(ks, regs);
kgdb_info[ks->cpu].exception_state &= ~DCPU_WANT_MASTER;
return ret;
}

int kgdb_nmicallback(int cpu, void *regs)
{
#ifdef CONFIG_SMP
struct kgdb_state kgdb_var;
struct kgdb_state *ks = &kgdb_var;

memset(ks, 0, sizeof(struct kgdb_state));
ks->cpu = cpu;
ks->linux_regs = regs;

if (!atomic_read(&cpu_in_kgdb[cpu]) &&
atomic_read(&kgdb_active) != cpu &&
atomic_read(&cpu_in_kgdb[atomic_read(&kgdb_active)])) {
kgdb_wait((struct pt_regs *)regs);
atomic_read(&kgdb_active) != -1 &&
atomic_read(&kgdb_active) != cpu) {
kgdb_info[cpu].exception_state |= DCPU_IS_SLAVE;
kgdb_cpu_enter(ks, regs);
kgdb_info[cpu].exception_state &= ~DCPU_IS_SLAVE;
return 0;
}
#endif
Expand Down Expand Up @@ -1742,11 +1743,11 @@ EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
*/
void kgdb_breakpoint(void)
{
atomic_set(&kgdb_setting_breakpoint, 1);
atomic_inc(&kgdb_setting_breakpoint);
wmb(); /* Sync point before breakpoint */
arch_kgdb_breakpoint();
wmb(); /* Sync point after breakpoint */
atomic_set(&kgdb_setting_breakpoint, 0);
atomic_dec(&kgdb_setting_breakpoint);
}
EXPORT_SYMBOL_GPL(kgdb_breakpoint);

Expand Down

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