From 146755923262037fc4c54abc28c04b1103f3cc51 Mon Sep 17 00:00:00 2001 From: Jay Lan Date: Mon, 29 Sep 2014 15:36:57 -0700 Subject: [PATCH 1/9] kdb: fix incorrect counts in KDB summary command output The output of KDB 'summary' command should report MemTotal, MemFree and Buffers output in kB. Current codes report in unit of pages. A define of K(x) as is defined in the code, but not used. This patch would apply the define to convert the values to kB. Please include me on Cc on replies. I do not subscribe to linux-kernel. Signed-off-by: Jay Lan Cc: Signed-off-by: Jason Wessel --- kernel/debug/kdb/kdb_main.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index 7b40c5f07dce..c6d2c0b1565d 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -2583,7 +2583,7 @@ static int kdb_summary(int argc, const char **argv) #define K(x) ((x) << (PAGE_SHIFT - 10)) kdb_printf("\nMemTotal: %8lu kB\nMemFree: %8lu kB\n" "Buffers: %8lu kB\n", - val.totalram, val.freeram, val.bufferram); + K(val.totalram), K(val.freeram), K(val.bufferram)); return 0; } From df0036d117e6c9df36324e517728e33543065f9a Mon Sep 17 00:00:00 2001 From: Jason Wessel Date: Thu, 8 Jan 2015 15:46:55 -0600 Subject: [PATCH 2/9] kdb: Fix off by one error in kdb_cpu() There was a follow on replacement patch against the prior "kgdb: Timeout if secondary CPUs ignore the roundup". See: https://lkml.org/lkml/2015/1/7/442 This patch is the delta vs the patch that was committed upstream: * Fix an off-by-one error in kdb_cpu(). * Replace NR_CPUS with CONFIG_NR_CPUS to tell checkpatch that we really want a static limit. * Removed the "KGDB: " prefix from the pr_crit() in debug_core.c (kgdb-next contains a patch which introduced pr_fmt() to this file to the tag will now be applied automatically). Cc: Daniel Thompson Cc: Signed-off-by: Jason Wessel --- kernel/debug/debug_core.c | 2 +- kernel/debug/kdb/kdb_main.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c index 07ce18ca71e0..ac5c0f9c7a20 100644 --- a/kernel/debug/debug_core.c +++ b/kernel/debug/debug_core.c @@ -604,7 +604,7 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs, online_cpus) cpu_relax(); if (!time_left) - pr_crit("KGDB: Timed out waiting for secondary CPUs.\n"); + pr_crit("Timed out waiting for secondary CPUs.\n"); /* * At this point the primary processor is completely diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index c6d2c0b1565d..60f6bb817f70 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -2256,7 +2256,7 @@ static int kdb_cpu(int argc, const char **argv) /* * Validate cpunum */ - if ((cpunum > NR_CPUS) || !kgdb_info[cpunum].enter_kgdb) + if ((cpunum >= CONFIG_NR_CPUS) || !kgdb_info[cpunum].enter_kgdb) return KDB_BADCPUNUM; dbg_switch_cpu = cpunum; From f7d4ca8bbfda23b4f1eae9b6757ff64166b093d5 Mon Sep 17 00:00:00 2001 From: Daniel Thompson Date: Fri, 7 Nov 2014 18:37:57 +0000 Subject: [PATCH 3/9] kdb: Avoid printing KERN_ levels to consoles Currently when kdb traps printk messages then the raw log level prefix (consisting of '\001' followed by a numeral) does not get stripped off before the message is issued to the various I/O handlers supported by kdb. This causes annoying visual noise as well as causing problems grepping for ^. It is also a change of behaviour compared to normal usage of printk() usage. For example -h ends up with different output to that of kdb's "sr h". This patch addresses the problem by stripping log levels from messages before they are issued to the I/O handlers. printk() which can also act as an i/o handler in some cases is special cased; if the caller provided a log level then the prefix will be preserved when sent to printk(). The addition of non-printable characters to the output of kdb commands is a regression, albeit and extremely elderly one, introduced by commit 04d2c8c83d0e ("printk: convert the format for KERN_ to a 2 byte pattern"). Note also that this patch does *not* restore the original behaviour from v3.5. Instead it makes printk() from within a kdb command display the message without any prefix (i.e. like printk() normally does). Signed-off-by: Daniel Thompson Cc: Joe Perches Cc: stable@vger.kernel.org Signed-off-by: Jason Wessel --- include/linux/kdb.h | 8 +++++++- kernel/debug/kdb/kdb_io.c | 22 +++++++++++++--------- kernel/printk/printk.c | 2 +- 3 files changed, 21 insertions(+), 11 deletions(-) diff --git a/include/linux/kdb.h b/include/linux/kdb.h index 75ae2e2631fc..a19bcf9e762e 100644 --- a/include/linux/kdb.h +++ b/include/linux/kdb.h @@ -156,8 +156,14 @@ typedef enum { KDB_REASON_SYSTEM_NMI, /* In NMI due to SYSTEM cmd; regs valid */ } kdb_reason_t; +enum kdb_msgsrc { + KDB_MSGSRC_INTERNAL, /* direct call to kdb_printf() */ + KDB_MSGSRC_PRINTK, /* trapped from printk() */ +}; + extern int kdb_trap_printk; -extern __printf(1, 0) int vkdb_printf(const char *fmt, va_list args); +extern __printf(2, 0) int vkdb_printf(enum kdb_msgsrc src, const char *fmt, + va_list args); extern __printf(1, 2) int kdb_printf(const char *, ...); typedef __printf(1, 2) int (*kdb_printf_t)(const char *, ...); diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c index 7c70812caea5..a550afb99ebe 100644 --- a/kernel/debug/kdb/kdb_io.c +++ b/kernel/debug/kdb/kdb_io.c @@ -548,7 +548,7 @@ static int kdb_search_string(char *searched, char *searchfor) return 0; } -int vkdb_printf(const char *fmt, va_list ap) +int vkdb_printf(enum kdb_msgsrc src, const char *fmt, va_list ap) { int diag; int linecount; @@ -691,19 +691,20 @@ int vkdb_printf(const char *fmt, va_list ap) * Write to all consoles. */ retlen = strlen(kdb_buffer); + cp = (char *) printk_skip_level(kdb_buffer); if (!dbg_kdb_mode && kgdb_connected) { - gdbstub_msg_write(kdb_buffer, retlen); + gdbstub_msg_write(cp, retlen - (cp - kdb_buffer)); } else { if (dbg_io_ops && !dbg_io_ops->is_console) { - len = retlen; - cp = kdb_buffer; + len = retlen - (cp - kdb_buffer); + cp2 = cp; while (len--) { - dbg_io_ops->write_char(*cp); - cp++; + dbg_io_ops->write_char(*cp2); + cp2++; } } while (c) { - c->write(c, kdb_buffer, retlen); + c->write(c, cp, retlen - (cp - kdb_buffer)); touch_nmi_watchdog(); c = c->next; } @@ -711,7 +712,10 @@ int vkdb_printf(const char *fmt, va_list ap) if (logging) { saved_loglevel = console_loglevel; console_loglevel = CONSOLE_LOGLEVEL_SILENT; - printk(KERN_INFO "%s", kdb_buffer); + if (printk_get_level(kdb_buffer) || src == KDB_MSGSRC_PRINTK) + printk("%s", kdb_buffer); + else + pr_info("%s", kdb_buffer); } if (KDB_STATE(PAGER)) { @@ -844,7 +848,7 @@ int kdb_printf(const char *fmt, ...) int r; va_start(ap, fmt); - r = vkdb_printf(fmt, ap); + r = vkdb_printf(KDB_MSGSRC_INTERNAL, fmt, ap); va_end(ap); return r; diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 02d6b6d28796..fae29e3ffbf0 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -1811,7 +1811,7 @@ int vprintk_default(const char *fmt, va_list args) #ifdef CONFIG_KGDB_KDB if (unlikely(kdb_trap_printk)) { - r = vkdb_printf(fmt, args); + r = vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args); return r; } #endif From 5454388113938d9592d6a6d5424469014da4ee86 Mon Sep 17 00:00:00 2001 From: Daniel Thompson Date: Thu, 6 Nov 2014 15:32:13 +0000 Subject: [PATCH 4/9] kdb: Remove stack dump when entering kgdb due to NMI Issuing a stack dump feels ergonomically wrong when entering due to NMI. Entering due to NMI is normally a reaction to a user request, either the NMI button on a server or a "magic knock" on a UART. Therefore the backtrace behaviour on entry due to NMI should be like SysRq-g (no stack dump) rather than like oops. Note also that the stack dump does not offer any information that cannot be trivial retrieved using the 'bt' command. Signed-off-by: Daniel Thompson Signed-off-by: Jason Wessel --- kernel/debug/kdb/kdb_main.c | 1 - 1 file changed, 1 deletion(-) diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index 60f6bb817f70..0a22f455060a 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -1247,7 +1247,6 @@ static int kdb_local(kdb_reason_t reason, int error, struct pt_regs *regs, kdb_printf("due to NonMaskable Interrupt @ " kdb_machreg_fmt "\n", instruction_pointer(regs)); - kdb_dumpregs(regs); break; case KDB_REASON_SSTEP: case KDB_REASON_BREAK: From ab08e464a2cd8242fdc6e4f87f3480808364a97a Mon Sep 17 00:00:00 2001 From: Daniel Thompson Date: Thu, 11 Sep 2014 09:58:29 +0100 Subject: [PATCH 5/9] kdb: Fix a prompt management bug when using | grep Currently when the "| grep" feature is used to filter the output of a command then the prompt is not displayed for the subsequent command. Likewise any characters typed by the user are also not echoed to the display. This rather disconcerting problem eventually corrects itself when the user presses Enter and the kdb_grepping_flag is cleared as kdb_parse() tries to make sense of whatever they typed. This patch resolves the problem by moving the clearing of this flag from the middle of command processing to the beginning. Signed-off-by: Daniel Thompson Signed-off-by: Jason Wessel --- kernel/debug/kdb/kdb_main.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index 0a22f455060a..420418360b81 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -915,13 +915,12 @@ int kdb_parse(const char *cmdstr) char *cp; char *cpp, quoted; kdbtab_t *tp; - int i, escaped, ignore_errors = 0, check_grep; + int i, escaped, ignore_errors = 0, check_grep = 0; /* * First tokenize the command string. */ cp = (char *)cmdstr; - kdb_grepping_flag = check_grep = 0; if (KDB_FLAG(CMD_INTERRUPT)) { /* Previous command was interrupted, newline must not @@ -1280,6 +1279,7 @@ static int kdb_local(kdb_reason_t reason, int error, struct pt_regs *regs, */ kdb_nextline = 1; KDB_STATE_CLEAR(SUPPRESS); + kdb_grepping_flag = 0; cmdbuf = cmd_cur; *cmdbuf = '\0'; From fb6daa7520f9d17a97e84a3d5a947819e0313f28 Mon Sep 17 00:00:00 2001 From: Daniel Thompson Date: Thu, 11 Sep 2014 10:37:10 +0100 Subject: [PATCH 6/9] kdb: Provide forward search at more prompt Currently kdb allows the output of comamnds to be filtered using the | grep feature. This is useful but does not permit the output emitted shortly after a string match to be examined without wading through the entire unfiltered output of the command. Such a feature is particularly useful to navigate function traces because these traces often have a useful trigger string *before* the point of interest. This patch reuses the existing filtering logic to introduce a simple forward search to kdb that can be triggered from the more prompt. Signed-off-by: Daniel Thompson Signed-off-by: Jason Wessel --- kernel/debug/kdb/kdb_io.c | 22 ++++++++++++++++++++-- kernel/debug/kdb/kdb_main.c | 7 ++++--- kernel/debug/kdb/kdb_private.h | 2 ++ 3 files changed, 26 insertions(+), 5 deletions(-) diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c index a550afb99ebe..ca13e6215537 100644 --- a/kernel/debug/kdb/kdb_io.c +++ b/kernel/debug/kdb/kdb_io.c @@ -680,6 +680,12 @@ int vkdb_printf(enum kdb_msgsrc src, const char *fmt, va_list ap) size_avail = sizeof(kdb_buffer) - len; goto kdb_print_out; } + if (kdb_grepping_flag >= KDB_GREPPING_FLAG_SEARCH) + /* + * This was a interactive search (using '/' at more + * prompt) and it has completed. Clear the flag. + */ + kdb_grepping_flag = 0; /* * at this point the string is a full line and * should be printed, up to the null. @@ -798,11 +804,23 @@ int vkdb_printf(enum kdb_msgsrc src, const char *fmt, va_list ap) kdb_nextline = linecount - 1; kdb_printf("\r"); suspend_grep = 1; /* for this recursion */ + } else if (buf1[0] == '/' && !kdb_grepping_flag) { + kdb_printf("\r"); + kdb_getstr(kdb_grep_string, KDB_GREP_STRLEN, + kdbgetenv("SEARCHPROMPT") ?: "search> "); + *strchrnul(kdb_grep_string, '\n') = '\0'; + kdb_grepping_flag += KDB_GREPPING_FLAG_SEARCH; + suspend_grep = 1; /* for this recursion */ } else if (buf1[0] && buf1[0] != '\n') { /* user hit something other than enter */ suspend_grep = 1; /* for this recursion */ - kdb_printf("\nOnly 'q' or 'Q' are processed at more " - "prompt, input ignored\n"); + if (buf1[0] != '/') + kdb_printf( + "\nOnly 'q', 'Q' or '/' are processed at " + "more prompt, input ignored\n"); + else + kdb_printf("\n'/' cannot be used during | " + "grep filtering, input ignored\n"); } else if (kdb_grepping_flag) { /* user hit enter */ suspend_grep = 1; /* for this recursion */ diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index 420418360b81..4121345498e0 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -50,8 +50,7 @@ static int kdb_cmd_enabled = CONFIG_KDB_DEFAULT_ENABLE; module_param_named(cmd_enable, kdb_cmd_enabled, int, 0600); -#define GREP_LEN 256 -char kdb_grep_string[GREP_LEN]; +char kdb_grep_string[KDB_GREP_STRLEN]; int kdb_grepping_flag; EXPORT_SYMBOL(kdb_grepping_flag); int kdb_grep_leading; @@ -870,7 +869,7 @@ static void parse_grep(const char *str) len = strlen(cp); if (!len) return; - if (len >= GREP_LEN) { + if (len >= KDB_GREP_STRLEN) { kdb_printf("search string too long\n"); return; } @@ -1280,6 +1279,8 @@ static int kdb_local(kdb_reason_t reason, int error, struct pt_regs *regs, kdb_nextline = 1; KDB_STATE_CLEAR(SUPPRESS); kdb_grepping_flag = 0; + /* ensure the old search does not leak into '/' commands */ + kdb_grep_string[0] = '\0'; cmdbuf = cmd_cur; *cmdbuf = '\0'; diff --git a/kernel/debug/kdb/kdb_private.h b/kernel/debug/kdb/kdb_private.h index eaacd1693954..da93894db7ba 100644 --- a/kernel/debug/kdb/kdb_private.h +++ b/kernel/debug/kdb/kdb_private.h @@ -196,7 +196,9 @@ extern int kdb_main_loop(kdb_reason_t, kdb_reason_t, /* Miscellaneous functions and data areas */ extern int kdb_grepping_flag; +#define KDB_GREPPING_FLAG_SEARCH 0x8000 extern char kdb_grep_string[]; +#define KDB_GREP_STRLEN 256 extern int kdb_grep_leading; extern int kdb_grep_trailing; extern char *kdb_cmds[]; From 32d375f6f24c3e4c9c235672695b4c314cf6b964 Mon Sep 17 00:00:00 2001 From: Daniel Thompson Date: Thu, 11 Sep 2014 10:41:12 +0100 Subject: [PATCH 7/9] kdb: Const qualifier for kdb_getstr's prompt argument All current callers of kdb_getstr() can pass constant pointers via the prompt argument. This patch adds a const qualification to make explicit the fact that this is safe. Signed-off-by: Daniel Thompson Signed-off-by: Jason Wessel --- kernel/debug/kdb/kdb_io.c | 2 +- kernel/debug/kdb/kdb_private.h | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c index ca13e6215537..fc1ef736253c 100644 --- a/kernel/debug/kdb/kdb_io.c +++ b/kernel/debug/kdb/kdb_io.c @@ -439,7 +439,7 @@ static char *kdb_read(char *buffer, size_t bufsize) * substituted for %d, %x or %o in the prompt. */ -char *kdb_getstr(char *buffer, size_t bufsize, char *prompt) +char *kdb_getstr(char *buffer, size_t bufsize, const char *prompt) { if (prompt && kdb_prompt_str != prompt) strncpy(kdb_prompt_str, prompt, CMD_BUFLEN); diff --git a/kernel/debug/kdb/kdb_private.h b/kernel/debug/kdb/kdb_private.h index da93894db7ba..75014d7f4568 100644 --- a/kernel/debug/kdb/kdb_private.h +++ b/kernel/debug/kdb/kdb_private.h @@ -211,7 +211,7 @@ extern void kdb_ps1(const struct task_struct *p); extern void kdb_print_nameval(const char *name, unsigned long val); extern void kdb_send_sig_info(struct task_struct *p, struct siginfo *info); extern void kdb_meminfo_proc_show(void); -extern char *kdb_getstr(char *, size_t, char *); +extern char *kdb_getstr(char *, size_t, const char *); extern void kdb_gdb_state_pass(char *buf); /* Defines for kdb_symbol_print */ From 5516fd7b92a7c16b9111a88aaa1b13dd937d8ac5 Mon Sep 17 00:00:00 2001 From: Colin Cross Date: Wed, 28 Jan 2015 17:02:14 +0530 Subject: [PATCH 8/9] debug: prevent entering debug mode on panic/exception. On non-developer devices, kgdb prevents the device from rebooting after a panic. Incase of panics and exceptions, to allow the device to reboot, prevent entering debug mode to avoid getting stuck waiting for the user to interact with debugger. To avoid entering the debugger on panic/exception without any extra configuration, panic_timeout is being used which can be set via /proc/sys/kernel/panic at run time and CONFIG_PANIC_TIMEOUT sets the default value. Setting panic_timeout indicates that the user requested machine to perform unattended reboot after panic. We dont want to get stuck waiting for the user input incase of panic. Cc: Andrew Morton Cc: kgdb-bugreport@lists.sourceforge.net Cc: linux-kernel@vger.kernel.org Cc: Android Kernel Team Cc: John Stultz Cc: Sumit Semwal Signed-off-by: Colin Cross [Kiran: Added context to commit message. panic_timeout is used instead of break_on_panic and break_on_exception to honor CONFIG_PANIC_TIMEOUT Modified the commit as per community feedback] Signed-off-by: Kiran Raparthy Signed-off-by: Daniel Thompson Signed-off-by: Jason Wessel --- kernel/debug/debug_core.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c index ac5c0f9c7a20..0874e2edd275 100644 --- a/kernel/debug/debug_core.c +++ b/kernel/debug/debug_core.c @@ -696,6 +696,14 @@ kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs) if (arch_kgdb_ops.enable_nmi) arch_kgdb_ops.enable_nmi(0); + /* + * Avoid entering the debugger if we were triggered due to an oops + * but panic_timeout indicates the system should automatically + * reboot on panic. We don't want to get stuck waiting for input + * on such systems, especially if its "just" an oops. + */ + if (signo != SIGTRAP && panic_timeout) + return 1; memset(ks, 0, sizeof(struct kgdb_state)); ks->cpu = raw_smp_processor_id(); @@ -828,6 +836,15 @@ static int kgdb_panic_event(struct notifier_block *self, unsigned long val, void *data) { + /* + * Avoid entering the debugger if we were triggered due to a panic + * We don't want to get stuck waiting for input from user in such case. + * panic_timeout indicates the system should automatically + * reboot on panic. + */ + if (panic_timeout) + return NOTIFY_DONE; + if (dbg_kdb_mode) kdb_printf("PANIC: %s\n", (char *)data); kgdb_breakpoint(); From dd8f30cc0550f36861ddfa42c27cc5c580b0bf8c Mon Sep 17 00:00:00 2001 From: Rajaneesh Acharya Date: Wed, 31 Dec 2014 17:43:19 +0000 Subject: [PATCH 9/9] kgdb, docs: Fix pdfdocs build errors kgdb.pdf failed to build from 'make pdfdocs' giving errors such as: jade:... Documentation/DocBook/kgdb.xml:200:8:E: document type does not allow element "para" here; missing one of "footnote", "caution", "important", "note", "tip", "warning", "blockquote", "informalexample" start-tag Fixing minor and issues allows kgdb.pdf to be generated under Fedora20. Originally submitted by rajaneesh.acharya@yahoo.com in 2011, discussed here: http://permalink.gmane.org/gmane.linux.documentation/3954 as patch: The following are the enhancements that removed the errors while issuing "make pdfdocs" [graham.whaley@intel.com: Improved commit message and ported to 3.18.1] Signed-off-by: Graham Whaley Signed-off-by: Jason Wessel --- Documentation/DocBook/kgdb.tmpl | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/Documentation/DocBook/kgdb.tmpl b/Documentation/DocBook/kgdb.tmpl index f77358f96930..efca2a418d5b 100644 --- a/Documentation/DocBook/kgdb.tmpl +++ b/Documentation/DocBook/kgdb.tmpl @@ -197,6 +197,7 @@ may be configured as a kernel built-in or a kernel loadable module. You can only make use of kgdbwait and early debugging if you build kgdboc into the kernel as a built-in. + Optionally you can elect to activate kms (Kernel Mode Setting) integration. When you use kms with kgdboc and you have a video driver that has atomic mode setting hooks, it is possible to @@ -206,7 +207,6 @@ crashes or doing analysis of memory with kdb while allowing the full graphics console applications to run. - kgdboc arguments Usage: kgdboc=[kms][[,]kbd][[,]serial_device][,baud] @@ -287,7 +287,6 @@ - NOTE: Kgdboc does not support interrupting the target via the gdb remote protocol. You must manually send a sysrq-g unless you have a proxy that splits console output to a terminal program. @@ -308,6 +307,7 @@ as well as on the initial connect, or to use a debugger proxy that allows an unmodified gdb to do the debugging. + @@ -353,12 +353,12 @@ + IMPORTANT NOTE: You cannot use kgdboc + kgdbcon on a tty that is an active system console. An example incorrect usage is console=ttyS0,115200 kgdboc=ttyS0 kgdbcon It is possible to use this option with kgdboc on a tty that is not a system console. - Run time parameter: kgdbreboot