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kgdb, x86, arm, mips, powerpc: ignore user space single stepping

Browse source 
On the x86 arch, user space single step exceptions should be ignored
if they occur in the kernel space, such as ptrace stepping through a
system call.

First check if it is kgdb that is executing a single step, then ensure
it is not an accidental traversal into the user space, while in kgdb,
any other time the TIF_SINGLESTEP is set, kgdb should ignore the
exception.

On x86, arm, mips and powerpc, the kgdb_contthread usage was
inconsistent with the way single stepping is implemented in the kgdb
core.  The arch specific stub should always set the
kgdb_cpu_doing_single_step correctly if it is single stepping.  This
allows kgdb to correctly process an instruction steps if ptrace
happens to be requesting an instruction step over a system call.

Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
This commit is contained in:
Jason Wessel 2008-09-26 10:36:41 -05:00
parent 18d6522b86
commit d7161a6534
5 changed files with 18 additions and 18 deletions
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2
arch/arm/kernel/kgdb.c
View file

@ -111,8 +111,6 @@ int kgdb_arch_handle_exception(int exception_vector, int signo,
case 'D':
case 'k':
case 'c':
kgdb_contthread = NULL;
/*
* Try to read optional parameter, pc unchanged if no parm.
* If this was a compiled breakpoint, we need to move

3
arch/mips/kernel/kgdb.c
View file

@ -236,8 +236,7 @@ int kgdb_arch_handle_exception(int vector, int signo, int err_code,
atomic_set(&kgdb_cpu_doing_single_step, -1);
if (remcom_in_buffer[0] == 's')
if (kgdb_contthread)
atomic_set(&kgdb_cpu_doing_single_step, cpu);
atomic_set(&kgdb_cpu_doing_single_step, cpu);
return 0;
}

5
arch/powerpc/kernel/kgdb.c
View file

@ -347,9 +347,8 @@ int kgdb_arch_handle_exception(int vector, int signo, int err_code,
linux_regs->msr |= MSR_SE;
#endif
kgdb_single_step = 1;
if (kgdb_contthread)
atomic_set(&kgdb_cpu_doing_single_step,
raw_smp_processor_id());
atomic_set(&kgdb_cpu_doing_single_step,
raw_smp_processor_id());
}
return 0;
}

18
arch/x86/kernel/kgdb.c
View file

@ -378,10 +378,8 @@ int kgdb_arch_handle_exception(int e_vector, int signo, int err_code,
if (remcomInBuffer[0] == 's') {
linux_regs->flags |= X86_EFLAGS_TF;
kgdb_single_step = 1;
if (kgdb_contthread) {
atomic_set(&kgdb_cpu_doing_single_step,
raw_smp_processor_id());
}
atomic_set(&kgdb_cpu_doing_single_step,
raw_smp_processor_id());
}
get_debugreg(dr6, 6);
@ -466,9 +464,15 @@ static int __kgdb_notify(struct die_args *args, unsigned long cmd)
case DIE_DEBUG:
if (atomic_read(&kgdb_cpu_doing_single_step) ==
raw_smp_processor_id() &&
user_mode(regs))
return single_step_cont(regs, args);
raw_smp_processor_id()) {
if (user_mode(regs))
return single_step_cont(regs, args);
break;
} else if (test_thread_flag(TIF_SINGLESTEP))
/* This means a user thread is single stepping
* a system call which should be ignored
*/
return NOTIFY_DONE;
/* fall through */
default:
if (user_mode(regs))

8
kernel/kgdb.c
View file

@ -1462,7 +1462,7 @@ acquirelock:
* Get the passive CPU lock which will hold all the non-primary
* CPU in a spin state while the debugger is active
*/
if (!kgdb_single_step || !kgdb_contthread) {
if (!kgdb_single_step) {
for (i = 0; i < NR_CPUS; i++)
atomic_set(&passive_cpu_wait[i], 1);
}
@ -1475,7 +1475,7 @@ acquirelock:
#ifdef CONFIG_SMP
/* Signal the other CPUs to enter kgdb_wait() */
if ((!kgdb_single_step || !kgdb_contthread) && kgdb_do_roundup)
if ((!kgdb_single_step) && kgdb_do_roundup)
kgdb_roundup_cpus(flags);
#endif
@ -1494,7 +1494,7 @@ acquirelock:
kgdb_post_primary_code(ks->linux_regs, ks->ex_vector, ks->err_code);
kgdb_deactivate_sw_breakpoints();
kgdb_single_step = 0;
kgdb_contthread = NULL;
kgdb_contthread = current;
exception_level = 0;
/* Talk to debugger with gdbserial protocol */
@ -1508,7 +1508,7 @@ acquirelock:
kgdb_info[ks->cpu].task = NULL;
atomic_set(&cpu_in_kgdb[ks->cpu], 0);
if (!kgdb_single_step || !kgdb_contthread) {
if (!kgdb_single_step) {
for (i = NR_CPUS-1; i >= 0; i--)
atomic_set(&passive_cpu_wait[i], 0);
/*