panic/reboot: allow specifying reboot_mode for panic only

Allow specifying reboot_mode for panic only.  This is needed on systems
where ramoops is used to store panic logs, and user wants to use warm
reset to preserve those, while still having cold reset on normal
reboots.

Link: http://lkml.kernel.org/r/20190322004735.27702-1-aaro.koskinen@iki.fi
Signed-off-by: Aaro Koskinen <aaro.koskinen@nokia.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 5be4d3f..80e40de 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4064,7 +4064,9 @@
                                [[,]s[mp]#### \
                                [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
                                [[,]f[orce]
-                       Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
+                       Where reboot_mode is one of warm (soft) or cold (hard) or gpio
+                                       (prefix with 'panic_' to set mode for panic
+                                       reboot only),
                              reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
                              reboot_force is either force or not specified,
                              reboot_cpu is s[mp]#### with #### being the processor

diff --git a/include/linux/reboot.h b/include/linux/reboot.h
index e63799a..3734cd8 100644 (file)
--- a/include/linux/reboot.h
+++ b/include/linux/reboot.h
@@ -14,6 +14,7 @@ struct device;
 #define SYS_POWER_OFF  0x0003  /* Notify of system power off */
 
 enum reboot_mode {
+       REBOOT_UNDEFINED = -1,
        REBOOT_COLD = 0,
        REBOOT_WARM,
        REBOOT_HARD,
@@ -21,6 +22,7 @@ enum reboot_mode {
        REBOOT_GPIO,
 };
 extern enum reboot_mode reboot_mode;
+extern enum reboot_mode panic_reboot_mode;
 
 enum reboot_type {
        BOOT_TRIPLE     = 't',

diff --git a/kernel/panic.c b/kernel/panic.c
index a614505..8779d64 100644 (file)
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -306,6 +306,8 @@ void panic(const char *fmt, ...)
                 * shutting down.  But if there is a chance of
                 * rebooting the system it will be rebooted.
                 */
+               if (panic_reboot_mode != REBOOT_UNDEFINED)
+                       reboot_mode = panic_reboot_mode;
                emergency_restart();
        }
 #ifdef __sparc__

diff --git a/kernel/reboot.c b/kernel/reboot.c
index e1b79b6..b9e79e8 100644 (file)
--- a/kernel/reboot.c
+++ b/kernel/reboot.c
@@ -31,6 +31,7 @@ EXPORT_SYMBOL(cad_pid);
 #define DEFAULT_REBOOT_MODE
 #endif
 enum reboot_mode reboot_mode DEFAULT_REBOOT_MODE;
+enum reboot_mode panic_reboot_mode = REBOOT_UNDEFINED;
 
 /*
  * This variable is used privately to keep track of whether or not
@@ -519,6 +520,8 @@ EXPORT_SYMBOL_GPL(orderly_reboot);
 static int __init reboot_setup(char *str)
 {
        for (;;) {
+               enum reboot_mode *mode;
+
                /*
                 * Having anything passed on the command line via
                 * reboot= will cause us to disable DMI checking
@@ -526,17 +529,24 @@ static int __init reboot_setup(char *str)
                 */
                reboot_default = 0;
 
+               if (!strncmp(str, "panic_", 6)) {
+                       mode = &panic_reboot_mode;
+                       str += 6;
+               } else {
+                       mode = &reboot_mode;
+               }
+
                switch (*str) {
                case 'w':
-                       reboot_mode = REBOOT_WARM;
+                       *mode = REBOOT_WARM;
                        break;
 
                case 'c':
-                       reboot_mode = REBOOT_COLD;
+                       *mode = REBOOT_COLD;
                        break;
 
                case 'h':
-                       reboot_mode = REBOOT_HARD;
+                       *mode = REBOOT_HARD;
                        break;
 
                case 's':
@@ -553,11 +563,11 @@ static int __init reboot_setup(char *str)
                                if (rc)
                                        return rc;
                        } else
-                               reboot_mode = REBOOT_SOFT;
+                               *mode = REBOOT_SOFT;
                        break;
                }
                case 'g':
-                       reboot_mode = REBOOT_GPIO;
+                       *mode = REBOOT_GPIO;
                        break;
 
                case 'b':