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kdb: Implement disable_nmi command

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This command disables NMI-entry. If NMI source has been previously shared
with a serial console ("debug port"), this effectively releases the port
from KDB exclusive use, and makes the console available for normal use.

Of course, NMI can be reenabled, enable_nmi modparam is used for that:

	echo 1 > /sys/module/kdb/parameters/enable_nmi

Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Acked-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Anton Vorontsov 2012-09-24 14:27:51 -07:00 committed by Greg Kroah-Hartman
parent 5a14fead07
commit ad394f66fa
1 changed files with 31 additions and 0 deletions
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31
kernel/debug/kdb/kdb_main.c
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@ -21,6 +21,7 @@
#include <linux/smp.h>
#include <linux/utsname.h>
#include <linux/vmalloc.h>
#include <linux/atomic.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/init.h>
@ -2107,6 +2108,32 @@ static int kdb_dmesg(int argc, const char **argv)
return 0;
}
#endif /* CONFIG_PRINTK */
/* Make sure we balance enable/disable calls, must disable first. */
static atomic_t kdb_nmi_disabled;
static int kdb_disable_nmi(int argc, const char *argv[])
{
if (atomic_read(&kdb_nmi_disabled))
return 0;
atomic_set(&kdb_nmi_disabled, 1);
arch_kgdb_ops.enable_nmi(0);
return 0;
}
static int kdb_param_enable_nmi(const char *val, const struct kernel_param *kp)
{
if (!atomic_add_unless(&kdb_nmi_disabled, -1, 0))
return -EINVAL;
arch_kgdb_ops.enable_nmi(1);
return 0;
}
static const struct kernel_param_ops kdb_param_ops_enable_nmi = {
.set = kdb_param_enable_nmi,
};
module_param_cb(enable_nmi, &kdb_param_ops_enable_nmi, NULL, 0600);
/*
* kdb_cpu - This function implements the 'cpu' command.
* cpu [<cpunum>]
@ -2851,6 +2878,10 @@ static void __init kdb_inittab(void)
kdb_register_repeat("dmesg", kdb_dmesg, "[lines]",
"Display syslog buffer", 0, KDB_REPEAT_NONE);
#endif
if (arch_kgdb_ops.enable_nmi) {
kdb_register_repeat("disable_nmi", kdb_disable_nmi, "",
"Disable NMI entry to KDB", 0, KDB_REPEAT_NONE);
}
kdb_register_repeat("defcmd", kdb_defcmd, "name \"usage\" \"help\"",
"Define a set of commands, down to endefcmd", 0, KDB_REPEAT_NONE);
kdb_register_repeat("kill", kdb_kill, "<-signal> <pid>",