sysctl: add cold_boot sysctl entry

Add a cold_boot parameter which supplements the
boot_reason sysctl entry with information about
whether the system was booted from cold or warm state.

/proc/sys/kernel/cold_boot entry is updated with 1 or 0 when
system was booted from cold or warm boot state respecitively.

CRs-Fixed: 461256
Change-Id: I2bc5d80c8f26eb9e9dbb4b34960d991a51a224e4
Signed-off-by: David Keitel <dkeitel@codeaurora.org>

Documentation/sysctl/kernel.txt

@@ -26,6 +26,7 @@ show up in /proc/sys/kernel:
 - boot_reason		     [ ARM only ]
 - callhome		     [ S390 only ]
 - cap_last_cap
+- cold_boot		     [ ARM only ]
 - core_pattern
 - core_pipe_limit
 - core_uses_pid
@@ -203,6 +204,16 @@ cap_last_cap
 Highest valid capability of the running kernel.  Exports
 CAP_LAST_CAP from the kernel.
 
+===============================================================
+
+cold_boot
+
+ARM -- indicator for system cold boot
+
+A single bit will be set in the unsigned integer value to identify
+whether the device was booted from a cold or warm state. Zero
+indicating a warm boot and one indicating a cold boot.
+
 ==============================================================
 
 core_pattern:

arch/arm/include/asm/processor.h

@@ -31,6 +31,7 @@
 #endif
 
 extern unsigned int boot_reason;
+extern unsigned int cold_boot;
 
 struct debug_info {
 #ifdef CONFIG_HAVE_HW_BREAKPOINT

arch/arm/kernel/setup.c

@@ -119,6 +119,9 @@ EXPORT_SYMBOL(arch_read_hardware_id);
 unsigned int boot_reason;
 EXPORT_SYMBOL(boot_reason);
 
+unsigned int cold_boot;
+EXPORT_SYMBOL(cold_boot);
+
 #ifdef MULTI_CPU
 struct processor processor __ro_after_init;
 #endif

include/uapi/linux/sysctl.h

@@ -154,6 +154,7 @@ enum
 	KERN_PANIC_ON_NMI=76, /* int: whether we will panic on an unrecovered */
 	KERN_PANIC_ON_WARN=77, /* int: call panic() in WARN() functions */
 	KERN_BOOT_REASON=78, /* int: identify reason system was booted */
+	KERN_COLD_BOOT=79, /* int: identify if system cold booted */
 };
 
 

kernel/sysctl.c

@@ -1241,7 +1241,15 @@ static struct ctl_table kern_table[] = {
 		.maxlen		= sizeof(int),
 		.mode		= 0444,
 		.proc_handler	= proc_dointvec,
-},
+	},
+
+	{
+		.procname	= "cold_boot",
+		.data		= &cold_boot,
+		.maxlen		= sizeof(int),
+		.mode		= 0444,
+		.proc_handler	= proc_dointvec,
+	},
 #endif
 	{ }
 };

kernel/sysctl_binary.c

@@ -141,6 +141,7 @@ static const struct bin_table bin_kern_table[] = {
 	{ CTL_INT,	KERN_PANIC_ON_NMI,		"panic_on_unrecovered_nmi" },
 	{ CTL_INT,	KERN_PANIC_ON_WARN,		"panic_on_warn" },
 	{ CTL_INT,	KERN_BOOT_REASON,		"boot_reason" },
+	{ CTL_INT,	KERN_COLD_BOOT,			"cold_boot" },
 	{}
 };