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Commit d7161a65 authored by Jason Wessel's avatar Jason Wessel
Browse files

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



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: default avatarJason Wessel <jason.wessel@windriver.com>
parent 18d6522b

arch/arm/kernel/kgdb.c

+0 −2
Original line number Diff line number Diff line
@@ -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

arch/mips/kernel/kgdb.c

+1 −2
Original line number Diff line number Diff line
@@ -236,7 +236,6 @@ 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);



		return 0;

arch/powerpc/kernel/kgdb.c

+2 −3
Original line number Diff line number Diff line
@@ -347,7 +347,6 @@ 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());

		}

arch/x86/kernel/kgdb.c

+11 −7
Original line number Diff line number Diff line
@@ -378,11 +378,9 @@ 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());

		}

		}



		get_debugreg(dr6, 6);

		if (!(dr6 & 0x4000)) {
@@ -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))

		    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))

kernel/kgdb.c

+4 −4
Original line number Diff line number Diff line
@@ -1462,7 +1462,7 @@ kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs) 
	 * 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 @@ kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs) 


#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 @@ kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs) 
	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 @@ kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs) 
	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);

		/*