From 45807a1df9f51d28d0ff0c6bcf900c210411d7c9 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Sun, 15 Jul 2007 23:40:10 -0700 Subject: [PATCH] vdso: print fatal signals Add the print-fatal-signals=1 boot option and the /proc/sys/kernel/print-fatal-signals runtime switch. This feature prints some minimal information about userspace segfaults to the kernel console. This is useful to find early bootup bugs where userspace debugging is very hard. Defaults to off. [akpm@linux-foundation.org: Don't add new sysctl numbers] Signed-off-by: Ingo Molnar Signed-off-by: Arjan van de Ven Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/kernel-parameters.txt | 6 ++++++ kernel/signal.c | 33 +++++++++++++++++++++++++++++ kernel/sysctl.c | 9 ++++++++ 3 files changed, 48 insertions(+) diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 182c6a39d5a..ab38322111c 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -1383,6 +1383,12 @@ and is between 256 and 4096 characters. It is defined in the file autoconfiguration. Ranges are in pairs (memory base and size). + print-fatal-signals= + [KNL] debug: print fatal signals + print-fatal-signals=1: print segfault info to + the kernel console. + default: off. + profile= [KNL] Enable kernel profiling via /proc/profile Format: [schedule,] Param: "schedule" - profile schedule points. diff --git a/kernel/signal.c b/kernel/signal.c index f9405609774..39d122753ba 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -718,6 +718,37 @@ out_set: #define LEGACY_QUEUE(sigptr, sig) \ (((sig) < SIGRTMIN) && sigismember(&(sigptr)->signal, (sig))) +int print_fatal_signals; + +static void print_fatal_signal(struct pt_regs *regs, int signr) +{ + printk("%s/%d: potentially unexpected fatal signal %d.\n", + current->comm, current->pid, signr); + +#ifdef __i386__ + printk("code at %08lx: ", regs->eip); + { + int i; + for (i = 0; i < 16; i++) { + unsigned char insn; + + __get_user(insn, (unsigned char *)(regs->eip + i)); + printk("%02x ", insn); + } + } +#endif + printk("\n"); + show_regs(regs); +} + +static int __init setup_print_fatal_signals(char *str) +{ + get_option (&str, &print_fatal_signals); + + return 1; +} + +__setup("print-fatal-signals=", setup_print_fatal_signals); static int specific_send_sig_info(int sig, struct siginfo *info, struct task_struct *t) @@ -1855,6 +1886,8 @@ relock: * Anything else is fatal, maybe with a core dump. */ current->flags |= PF_SIGNALED; + if ((signr != SIGKILL) && print_fatal_signals) + print_fatal_signal(regs, signr); if (sig_kernel_coredump(signr)) { /* * If it was able to dump core, this kills all diff --git a/kernel/sysctl.c b/kernel/sysctl.c index ccaebbbd75a..2cce2286bdc 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -61,6 +61,7 @@ extern int proc_nr_files(ctl_table *table, int write, struct file *filp, /* External variables not in a header file. */ extern int C_A_D; +extern int print_fatal_signals; extern int sysctl_overcommit_memory; extern int sysctl_overcommit_ratio; extern int sysctl_panic_on_oom; @@ -340,6 +341,14 @@ static ctl_table kern_table[] = { .proc_handler = &proc_dointvec, }, #endif + { + .ctl_name = CTL_UNNUMBERED, + .procname = "print-fatal-signals", + .data = &print_fatal_signals, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = &proc_dointvec, + }, #ifdef __sparc__ { .ctl_name = KERN_SPARC_REBOOT,