From bb0bb3b6596cdb08adb0b72453cc67d48e139c2c Mon Sep 17 00:00:00 2001 From: Paul Mackerras Date: Sat, 10 Sep 2005 21:13:11 +1000 Subject: [PATCH] [PATCH] ppc32: Kill init on unhandled synchronous signals This is a patch that I have had in my tree for ages. If init causes an exception that raises a signal, such as a SIGSEGV, SIGILL or SIGFPE, and it hasn't registered a handler for it, we don't deliver the signal, since init doesn't get any signals that it doesn't have a handler for. But that means that we just return to userland and generate the same exception again immediately. With this patch we print a message and kill init in this situation. This is very useful when you have a bug in the kernel that means that init doesn't get as far as executing its first instruction. :) Without this patch the system hangs when it gets to starting the userland init; with it you at least get a message giving you a clue about what has gone wrong. Signed-off-by: Paul Mackerras Signed-off-by: Linus Torvalds --- arch/ppc/kernel/traps.c | 22 ++++++++++++++++++++++ arch/ppc/mm/fault.c | 6 +----- include/asm-ppc/system.h | 1 + 3 files changed, 24 insertions(+), 5 deletions(-) diff --git a/arch/ppc/kernel/traps.c b/arch/ppc/kernel/traps.c index 8356d544fa6..961ede87be7 100644 --- a/arch/ppc/kernel/traps.c +++ b/arch/ppc/kernel/traps.c @@ -118,6 +118,28 @@ void _exception(int signr, struct pt_regs *regs, int code, unsigned long addr) info.si_code = code; info.si_addr = (void __user *) addr; force_sig_info(signr, &info, current); + + /* + * Init gets no signals that it doesn't have a handler for. + * That's all very well, but if it has caused a synchronous + * exception and we ignore the resulting signal, it will just + * generate the same exception over and over again and we get + * nowhere. Better to kill it and let the kernel panic. + */ + if (current->pid == 1) { + __sighandler_t handler; + + spin_lock_irq(¤t->sighand->siglock); + handler = current->sighand->action[signr-1].sa.sa_handler; + spin_unlock_irq(¤t->sighand->siglock); + if (handler == SIG_DFL) { + /* init has generated a synchronous exception + and it doesn't have a handler for the signal */ + printk(KERN_CRIT "init has generated signal %d " + "but has no handler for it\n", signr); + do_exit(signr); + } + } } /* diff --git a/arch/ppc/mm/fault.c b/arch/ppc/mm/fault.c index 57d9930843a..ee5e9f25baf 100644 --- a/arch/ppc/mm/fault.c +++ b/arch/ppc/mm/fault.c @@ -278,11 +278,7 @@ bad_area: /* User mode accesses cause a SIGSEGV */ if (user_mode(regs)) { - info.si_signo = SIGSEGV; - info.si_errno = 0; - info.si_code = code; - info.si_addr = (void __user *) address; - force_sig_info(SIGSEGV, &info, current); + _exception(SIGSEGV, regs, code, address); return 0; } diff --git a/include/asm-ppc/system.h b/include/asm-ppc/system.h index 513a334c581..d754ab570fe 100644 --- a/include/asm-ppc/system.h +++ b/include/asm-ppc/system.h @@ -88,6 +88,7 @@ extern void *cacheable_memcpy(void *, const void *, unsigned int); extern int do_page_fault(struct pt_regs *, unsigned long, unsigned long); extern void bad_page_fault(struct pt_regs *, unsigned long, int); extern void die(const char *, struct pt_regs *, long); +extern void _exception(int, struct pt_regs *, int, unsigned long); #ifdef CONFIG_BOOKE_WDT extern u32 booke_wdt_enabled; extern u32 booke_wdt_period; -- 2.41.1