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

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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

1
arch/mips/kernel/kgdb.c
View File

@ -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;

1
arch/powerpc/kernel/kgdb.c
View File

@ -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());
}

12
arch/x86/kernel/kgdb.c
View File

@ -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))

8
kernel/kgdb.c
View File

@ -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);
/*