From 5a14fead07bcf4e0acc877a8d9e1d1f40a441153 Mon Sep 17 00:00:00 2001 From: Anton Vorontsov Date: Mon, 24 Sep 2012 14:27:50 -0700 Subject: kernel/debug: Mask KGDB NMI upon entry The new arch callback should manage NMIs that usually cause KGDB to enter. That is, not all NMIs should be enabled/disabled, but only those that issue kgdb_handle_exception(). We must mask it as serial-line interrupt can be used as an NMI, so if the original KGDB-entry cause was say a breakpoint, then every input to KDB console will cause KGDB to reenter, which we don't want. Signed-off-by: Anton Vorontsov Acked-by: Jason Wessel Signed-off-by: Greg Kroah-Hartman --- kernel/debug/debug_core.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) (limited to 'kernel/debug') diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c index 0557f24c6bca..17e073c309e6 100644 --- a/kernel/debug/debug_core.c +++ b/kernel/debug/debug_core.c @@ -672,6 +672,10 @@ kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs) { struct kgdb_state kgdb_var; struct kgdb_state *ks = &kgdb_var; + int ret = 0; + + if (arch_kgdb_ops.enable_nmi) + arch_kgdb_ops.enable_nmi(0); ks->cpu = raw_smp_processor_id(); ks->ex_vector = evector; @@ -681,11 +685,15 @@ kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs) ks->linux_regs = regs; if (kgdb_reenter_check(ks)) - return 0; /* Ouch, double exception ! */ + goto out; /* Ouch, double exception ! */ if (kgdb_info[ks->cpu].enter_kgdb != 0) - return 0; + goto out; - return kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER); + ret = kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER); +out: + if (arch_kgdb_ops.enable_nmi) + arch_kgdb_ops.enable_nmi(1); + return ret; } int kgdb_nmicallback(int cpu, void *regs) -- cgit v1.2.3 From ad394f66fa57ae66014cb74f337e2820bac4c417 Mon Sep 17 00:00:00 2001 From: Anton Vorontsov Date: Mon, 24 Sep 2012 14:27:51 -0700 Subject: kdb: Implement disable_nmi command This command disables NMI-entry. If NMI source has been previously shared with a serial console ("debug port"), this effectively releases the port from KDB exclusive use, and makes the console available for normal use. Of course, NMI can be reenabled, enable_nmi modparam is used for that: echo 1 > /sys/module/kdb/parameters/enable_nmi Signed-off-by: Anton Vorontsov Acked-by: Jason Wessel Signed-off-by: Greg Kroah-Hartman --- kernel/debug/kdb/kdb_main.c | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) (limited to 'kernel/debug') diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index 31df1706b9a9..1261dc7eaeb9 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -21,6 +21,7 @@ #include #include #include +#include #include #include #include @@ -2107,6 +2108,32 @@ static int kdb_dmesg(int argc, const char **argv) return 0; } #endif /* CONFIG_PRINTK */ + +/* Make sure we balance enable/disable calls, must disable first. */ +static atomic_t kdb_nmi_disabled; + +static int kdb_disable_nmi(int argc, const char *argv[]) +{ + if (atomic_read(&kdb_nmi_disabled)) + return 0; + atomic_set(&kdb_nmi_disabled, 1); + arch_kgdb_ops.enable_nmi(0); + return 0; +} + +static int kdb_param_enable_nmi(const char *val, const struct kernel_param *kp) +{ + if (!atomic_add_unless(&kdb_nmi_disabled, -1, 0)) + return -EINVAL; + arch_kgdb_ops.enable_nmi(1); + return 0; +} + +static const struct kernel_param_ops kdb_param_ops_enable_nmi = { + .set = kdb_param_enable_nmi, +}; +module_param_cb(enable_nmi, &kdb_param_ops_enable_nmi, NULL, 0600); + /* * kdb_cpu - This function implements the 'cpu' command. * cpu [] @@ -2851,6 +2878,10 @@ static void __init kdb_inittab(void) kdb_register_repeat("dmesg", kdb_dmesg, "[lines]", "Display syslog buffer", 0, KDB_REPEAT_NONE); #endif + if (arch_kgdb_ops.enable_nmi) { + kdb_register_repeat("disable_nmi", kdb_disable_nmi, "", + "Disable NMI entry to KDB", 0, KDB_REPEAT_NONE); + } kdb_register_repeat("defcmd", kdb_defcmd, "name \"usage\" \"help\"", "Define a set of commands, down to endefcmd", 0, KDB_REPEAT_NONE); kdb_register_repeat("kill", kdb_kill, "<-signal> ", -- cgit v1.2.3 From f30fed10c440a25937e509860fa207399b26efe5 Mon Sep 17 00:00:00 2001 From: Jason Wessel Date: Fri, 12 Oct 2012 06:37:33 -0500 Subject: kgdb: Add module event hooks Allow gdb to auto load kernel modules when it is attached, which makes it trivially easy to debug module init functions or pre-set breakpoints in a kernel module that has not loaded yet. Signed-off-by: Jason Wessel --- kernel/debug/debug_core.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) (limited to 'kernel/debug') diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c index 0557f24c6bca..8bfa373cd5fd 100644 --- a/kernel/debug/debug_core.c +++ b/kernel/debug/debug_core.c @@ -688,6 +688,22 @@ kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs) return kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER); } +/* + * GDB places a breakpoint at this function to know dynamically + * loaded objects. It's not defined static so that only one instance with this + * name exists in the kernel. + */ + +static int module_event(struct notifier_block *self, unsigned long val, + void *data) +{ + return 0; +} + +static struct notifier_block dbg_module_load_nb = { + .notifier_call = module_event, +}; + int kgdb_nmicallback(int cpu, void *regs) { #ifdef CONFIG_SMP @@ -816,6 +832,7 @@ static void kgdb_register_callbacks(void) kgdb_arch_init(); if (!dbg_is_early) kgdb_arch_late(); + register_module_notifier(&dbg_module_load_nb); register_reboot_notifier(&dbg_reboot_notifier); atomic_notifier_chain_register(&panic_notifier_list, &kgdb_panic_event_nb); @@ -839,6 +856,7 @@ static void kgdb_unregister_callbacks(void) if (kgdb_io_module_registered) { kgdb_io_module_registered = 0; unregister_reboot_notifier(&dbg_reboot_notifier); + unregister_module_notifier(&dbg_module_load_nb); atomic_notifier_chain_unregister(&panic_notifier_list, &kgdb_panic_event_nb); kgdb_arch_exit(); -- cgit v1.2.3 From d1871b38fccdc4b6575b0cabdea9e06bc70167eb Mon Sep 17 00:00:00 2001 From: Jason Wessel Date: Sun, 26 Aug 2012 21:43:12 -0500 Subject: kdb: Fix dmesg/bta scroll to quit with 'q' If you press 'q' the pager should exit instead of printing everything from dmesg which can really bog down a 9600 baud serial link. The same is true for the bta command. Signed-off-by: Jason Wessel --- kernel/debug/kdb/kdb_bt.c | 2 ++ kernel/debug/kdb/kdb_main.c | 2 ++ 2 files changed, 4 insertions(+) (limited to 'kernel/debug') diff --git a/kernel/debug/kdb/kdb_bt.c b/kernel/debug/kdb/kdb_bt.c index 07c9bbb94a0b..b03e0e814e43 100644 --- a/kernel/debug/kdb/kdb_bt.c +++ b/kernel/debug/kdb/kdb_bt.c @@ -129,6 +129,8 @@ kdb_bt(int argc, const char **argv) } /* Now the inactive tasks */ kdb_do_each_thread(g, p) { + if (KDB_FLAG(CMD_INTERRUPT)) + return 0; if (task_curr(p)) continue; if (kdb_bt1(p, mask, argcount, btaprompt)) diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index 31df1706b9a9..1afeb5c1e5a9 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -2100,6 +2100,8 @@ static int kdb_dmesg(int argc, const char **argv) } if (!lines--) break; + if (KDB_FLAG(CMD_INTERRUPT)) + return 0; kdb_printf("%.*s\n", (int)len - 1, buf); } -- cgit v1.2.3 From 17b572e82032bc246324ce136696656b66d4e3f1 Mon Sep 17 00:00:00 2001 From: Jason Wessel Date: Sun, 26 Aug 2012 22:37:03 -0500 Subject: kdb,vt_console: Fix missed data due to pager overruns It is possible to miss data when using the kdb pager. The kdb pager does not pay attention to the maximum column constraint of the screen or serial terminal. This result is not incrementing the shown lines correctly and the pager will print more lines that fit on the screen. Obviously that is less than useful when using a VGA console where you cannot scroll back. The pager will now look at the kdb_buffer string to see how many characters are printed. It might not be perfect considering you can output ASCII that might move the cursor position, but it is a substantially better approximation for viewing dmesg and trace logs. This also means that the vt screen needs to set the kdb COLUMNS variable. Cc: Signed-off-by: Jason Wessel --- kernel/debug/kdb/kdb_io.c | 33 ++++++++++++++++++++++++++++----- 1 file changed, 28 insertions(+), 5 deletions(-) (limited to 'kernel/debug') diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c index 0a69d2adc4f3..14ff4849262c 100644 --- a/kernel/debug/kdb/kdb_io.c +++ b/kernel/debug/kdb/kdb_io.c @@ -552,6 +552,7 @@ int vkdb_printf(const char *fmt, va_list ap) { int diag; int linecount; + int colcount; int logging, saved_loglevel = 0; int saved_trap_printk; int got_printf_lock = 0; @@ -584,6 +585,10 @@ int vkdb_printf(const char *fmt, va_list ap) if (diag || linecount <= 1) linecount = 24; + diag = kdbgetintenv("COLUMNS", &colcount); + if (diag || colcount <= 1) + colcount = 80; + diag = kdbgetintenv("LOGGING", &logging); if (diag) logging = 0; @@ -690,7 +695,7 @@ kdb_printit: gdbstub_msg_write(kdb_buffer, retlen); } else { if (dbg_io_ops && !dbg_io_ops->is_console) { - len = strlen(kdb_buffer); + len = retlen; cp = kdb_buffer; while (len--) { dbg_io_ops->write_char(*cp); @@ -709,11 +714,29 @@ kdb_printit: printk(KERN_INFO "%s", kdb_buffer); } - if (KDB_STATE(PAGER) && strchr(kdb_buffer, '\n')) - kdb_nextline++; + if (KDB_STATE(PAGER)) { + /* + * Check printed string to decide how to bump the + * kdb_nextline to control when the more prompt should + * show up. + */ + int got = 0; + len = retlen; + while (len--) { + if (kdb_buffer[len] == '\n') { + kdb_nextline++; + got = 0; + } else if (kdb_buffer[len] == '\r') { + got = 0; + } else { + got++; + } + } + kdb_nextline += got / (colcount + 1); + } /* check for having reached the LINES number of printed lines */ - if (kdb_nextline == linecount) { + if (kdb_nextline >= linecount) { char buf1[16] = ""; /* Watch out for recursion here. Any routine that calls @@ -765,7 +788,7 @@ kdb_printit: kdb_grepping_flag = 0; kdb_printf("\n"); } else if (buf1[0] == ' ') { - kdb_printf("\n"); + kdb_printf("\r"); suspend_grep = 1; /* for this recursion */ } else if (buf1[0] == '\n') { kdb_nextline = linecount - 1; -- cgit v1.2.3