From ea424055b771a165c9abd3ae109255a3b825c745 Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Wed, 30 Aug 2006 19:37:11 +0200 Subject: [PATCH] x86: Make backtracer fallback logic more bullet-proof The unwinder fallback logic still had potential for falling through to the legacy stack trace code without printing an indication (at once serving as a separator) of this. Further, the stack pointer retrieval for the fallback should be as restrictive as possible (in order to avoid having the legacy stack tracer try to access invalid memory). The patch tightens that, but this could certainly be further improved. Also making the call_trace command line option now conditional upon CONFIG_STACK_UNWIND (as it's meaningless otherwise). Signed-off-by: Jan Beulich Signed-off-by: Andi Kleen Signed-off-by: Linus Torvalds --- arch/i386/kernel/traps.c | 27 ++++++++++++++++----------- 1 file changed, 16 insertions(+), 11 deletions(-) (limited to 'arch/i386') diff --git a/arch/i386/kernel/traps.c b/arch/i386/kernel/traps.c index 82e0fd02af1..7e9edafffd8 100644 --- a/arch/i386/kernel/traps.c +++ b/arch/i386/kernel/traps.c @@ -92,7 +92,11 @@ asmlinkage void spurious_interrupt_bug(void); asmlinkage void machine_check(void); static int kstack_depth_to_print = 24; +#ifdef CONFIG_STACK_UNWIND static int call_trace = 1; +#else +#define call_trace (-1) +#endif ATOMIC_NOTIFIER_HEAD(i386die_chain); int register_die_notifier(struct notifier_block *nb) @@ -187,22 +191,21 @@ static void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs, if (unwind_init_blocked(&info, task) == 0) unw_ret = show_trace_unwind(&info, log_lvl); } - if (unw_ret > 0 && !arch_unw_user_mode(&info)) { -#ifdef CONFIG_STACK_UNWIND - print_symbol("DWARF2 unwinder stuck at %s\n", - UNW_PC(&info)); - if (call_trace == 1) { - printk("Leftover inexact backtrace:\n"); - if (UNW_SP(&info)) + if (unw_ret > 0) { + if (call_trace == 1 && !arch_unw_user_mode(&info)) { + print_symbol("DWARF2 unwinder stuck at %s\n", + UNW_PC(&info)); + if (UNW_SP(&info) >= PAGE_OFFSET) { + printk("Leftover inexact backtrace:\n"); stack = (void *)UNW_SP(&info); - } else if (call_trace > 1) + } else + printk("Full inexact backtrace again:\n"); + } else if (call_trace >= 1) return; else printk("Full inexact backtrace again:\n"); -#else + } else printk("Inexact backtrace:\n"); -#endif - } } if (task == current) { @@ -1241,6 +1244,7 @@ static int __init kstack_setup(char *s) } __setup("kstack=", kstack_setup); +#ifdef CONFIG_STACK_UNWIND static int __init call_trace_setup(char *s) { if (strcmp(s, "old") == 0) @@ -1254,3 +1258,4 @@ static int __init call_trace_setup(char *s) return 1; } __setup("call_trace=", call_trace_setup); +#endif -- cgit v1.2.3