[RFC PATCH 3/5] x86: add a sysctl parameter to panic on stack overflow

[Mitsuo Hayasaka]

This patch adds kernel.panic_on_stackoverflow sysctl parameter,
which can cause a panic when detecting the stack overflow.

Signed-off-by: Mitsuo Hayasaka <mitsuo.hayasaka.hu@xxxxxxxxxxx>
Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
---

 Documentation/sysctl/kernel.txt |   13 +++++++++++++
 arch/x86/kernel/irq_64.c        |    2 ++
 include/linux/kernel.h          |    1 +
 include/linux/sysctl.h          |    1 +
 kernel/sysctl.c                 |    9 +++++++++
 kernel/sysctl_binary.c          |    1 +
 6 files changed, 27 insertions(+), 0 deletions(-)

diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index 704e474..eb8d263 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -48,6 +48,7 @@ show up in /proc/sys/kernel:
 - panic
 - panic_on_oops
 - panic_on_unrecovered_nmi
+- panic_on_stackoverflow
 - pid_max
 - powersave-nap               [ PPC only ]
 - printk
@@ -385,6 +386,18 @@ Controls the kernel's behaviour when an oops or BUG is encountered.
 
 ==============================================================
 
+panic_on_stackoverflow:
+
+Controls the kernel's behaviour when detecting stack overflow.
+This file shows up if CONFIG_DEBUG_STACKOVERFLOW is enabled.
+
+0: try to continue operation.
+
+1: panic immediately.
+
+==============================================================
+
+
 pid_max:
 
 PID allocation wrap value.  When the kernel's next PID value
diff --git a/arch/x86/kernel/irq_64.c b/arch/x86/kernel/irq_64.c
index 530cfd0..d720813 100644
--- a/arch/x86/kernel/irq_64.c
+++ b/arch/x86/kernel/irq_64.c
@@ -20,6 +20,8 @@
 #include <asm/idle.h>
 #include <asm/apic.h>
 
+int sysctl_panic_on_stackoverflow;
+
 DEFINE_PER_CPU_SHARED_ALIGNED(irq_cpustat_t, irq_stat);
 EXPORT_PER_CPU_SYMBOL(irq_stat);
 
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 8eefcf7..19b3595 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -339,6 +339,7 @@ extern int panic_timeout;
 extern int panic_on_oops;
 extern int panic_on_unrecovered_nmi;
 extern int panic_on_io_nmi;
+extern int sysctl_panic_on_stackoverflow;
 extern const char *print_tainted(void);
 extern void add_taint(unsigned flag);
 extern int test_taint(unsigned flag);
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 9a1ec10..4b9dc3d 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -153,6 +153,7 @@ enum
 	KERN_MAX_LOCK_DEPTH=74, /* int: rtmutex's maximum lock depth */
 	KERN_NMI_WATCHDOG=75, /* int: enable/disable nmi watchdog */
 	KERN_PANIC_ON_NMI=76, /* int: whether we will panic on an unrecovered */
+	KERN_PANIC_ON_STACKOVERFLOW = 77, /* int: panic on stack overflow */
 };
 
 
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 11d65b5..08a18f9 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -792,6 +792,15 @@ static struct ctl_table kern_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec,
 	},
+#if defined(CONFIG_DEBUG_STACKOVERFLOW)
+	{
+		.procname	= "panic_on_stackoverflow",
+		.data		= &sysctl_panic_on_stackoverflow,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+#endif
 	{
 		.procname	= "bootloader_type",
 		.data		= &bootloader_type,
diff --git a/kernel/sysctl_binary.c b/kernel/sysctl_binary.c
index 6318b51..24fc654 100644
--- a/kernel/sysctl_binary.c
+++ b/kernel/sysctl_binary.c
@@ -137,6 +137,7 @@ static const struct bin_table bin_kern_table[] = {
 	{ CTL_INT,	KERN_COMPAT_LOG,		"compat-log" },
 	{ CTL_INT,	KERN_MAX_LOCK_DEPTH,		"max_lock_depth" },
 	{ CTL_INT,	KERN_PANIC_ON_NMI,		"panic_on_unrecovered_nmi" },
+	{ CTL_INT,	KERN_PANIC_ON_STACKOVERFLOW,	"panic_on_stackoverflow" },
 	{}
 };
 

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