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 5be4d3ff5e701be9db22c9e87c6ff3662a6b56d0..80e40de446c00b384cfea833841c9df724c1bb5a 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 e63799a6e89515d0893606530b07e101f39c52fb..3734cd8f38a896d55af2ff3a3f3518707444c4fe 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 a6145050a8da21a24706d48138f1545438afdb5a..8779d64bace0b1db43672924f637f078225da8e3 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 e1b79b6a273550516a57d3f7db10c236fcdf0305..b9e79e8c722654e84cc90407f3dfc8322d4ffe23 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':