(2014/03/22 10:05), Steven Rostedt wrote: > On Wed, 05 Mar 2014 20:59:39 +0900 > Masami Hiramatsu <[email protected]> wrote: > >> To avoid a kernel crash by probing on lockdep code, call >> kprobe_int3_handler and kprobe_debug_handler directly >> from do_int3 and do_debug. Since there is a locking code >> in notify_die, lockdep code can be invoked. And because >> the lockdep involves printk() related things, theoretically, >> we need to prohibit probing on much more code... >> >> Anyway, most of the int3 handlers in the kernel are already >> called from do_int3 directly, e.g. ftrace_int3_handler, >> poke_int3_handler, kgdb_ll_trap. Actually only >> kprobe_exceptions_notify is on the notifier_call_chain. >> >> Signed-off-by: Masami Hiramatsu <[email protected]> >> Cc: Thomas Gleixner <[email protected]> >> Cc: Ingo Molnar <[email protected]> >> Cc: "H. Peter Anvin" <[email protected]> >> Cc: Ananth N Mavinakayanahalli <[email protected]> >> Cc: Andi Kleen <[email protected]> >> Cc: Steven Rostedt <[email protected]> >> Cc: Sasha Levin <[email protected]> >> Cc: Andrew Morton <[email protected]> >> Cc: Seiji Aguchi <[email protected]> >> Cc: Frederic Weisbecker <[email protected]> >> --- >> arch/x86/include/asm/kprobes.h | 2 ++ >> arch/x86/kernel/kprobes/core.c | 24 +++--------------------- >> arch/x86/kernel/traps.c | 10 ++++++++++ >> 3 files changed, 15 insertions(+), 21 deletions(-) >> >> diff --git a/arch/x86/include/asm/kprobes.h b/arch/x86/include/asm/kprobes.h >> index 9454c16..53cdfb2 100644 >> --- a/arch/x86/include/asm/kprobes.h >> +++ b/arch/x86/include/asm/kprobes.h >> @@ -116,4 +116,6 @@ struct kprobe_ctlblk { >> extern int kprobe_fault_handler(struct pt_regs *regs, int trapnr); >> extern int kprobe_exceptions_notify(struct notifier_block *self, >> unsigned long val, void *data); >> +extern int kprobe_int3_handler(struct pt_regs *regs); >> +extern int kprobe_debug_handler(struct pt_regs *regs); >> #endif /* _ASM_X86_KPROBES_H */ >> diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c >> index 4708d6e..566958e 100644 >> --- a/arch/x86/kernel/kprobes/core.c >> +++ b/arch/x86/kernel/kprobes/core.c >> @@ -559,7 +559,7 @@ reenter_kprobe(struct kprobe *p, struct pt_regs *regs, >> struct kprobe_ctlblk *kcb >> * Interrupts are disabled on entry as trap3 is an interrupt gate and they >> * remain disabled throughout this function. >> */ >> -static int __kprobes kprobe_handler(struct pt_regs *regs) >> +int __kprobes kprobe_int3_handler(struct pt_regs *regs) >> { >> kprobe_opcode_t *addr; >> struct kprobe *p; >> @@ -857,7 +857,7 @@ no_change: >> * Interrupts are disabled on entry as trap1 is an interrupt gate and they >> * remain disabled throughout this function. >> */ >> -static int __kprobes post_kprobe_handler(struct pt_regs *regs) >> +int __kprobes kprobe_debug_handler(struct pt_regs *regs) >> { >> struct kprobe *cur = kprobe_running(); >> struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); >> @@ -960,22 +960,7 @@ kprobe_exceptions_notify(struct notifier_block *self, >> unsigned long val, void *d >> if (args->regs && user_mode_vm(args->regs)) >> return ret; >> >> - switch (val) { >> - case DIE_INT3: >> - if (kprobe_handler(args->regs)) >> - ret = NOTIFY_STOP; >> - break; >> - case DIE_DEBUG: >> - if (post_kprobe_handler(args->regs)) { >> - /* >> - * Reset the BS bit in dr6 (pointed by args->err) to >> - * denote completion of processing >> - */ >> - (*(unsigned long *)ERR_PTR(args->err)) &= ~DR_STEP; >> - ret = NOTIFY_STOP; >> - } > > The DIE_DEBUG case is removed but not added anyplace else. The change > log doesn't say why this was removed.
As you can see the above hunk, post_kprobe_handler() is now renamed as kprobe_debug_handler() which is called from do_debug() directly. What I meant in the patch comment; >> To avoid a kernel crash by probing on lockdep code, call >> kprobe_int3_handler and kprobe_debug_handler directly >> from do_int3 and do_debug. was actually pointing that change... Thank you, -- Masami HIRAMATSU IT Management Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: [email protected] -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
