| Message ID | 20180828201421.157735-3-jannh@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | x86: BUG() on #GP / kernel #PF in uaccess | expand |
On Tue, 28 Aug 2018 22:14:16 +0200 Jann Horn <jannh@google.com> wrote: > The opaque plumbing of #GP from do_general_protection() through > notify_die() into kprobe_exceptions_notify() makes it hard to understand > what's going on. OK, this seems reasonable optimization, since kprobe_exceptions_notify only handles DIE_GPF now. Acked-by: Masami Hiramatsu <mhiramat@kernel.org> Hmm, I think I should introduce ARCH_KPROBE_HANDLE_EXCEPTION and if it is enabled, kernel/kprobes.c stops using exception notifier. It is no more needed on x86. Thank you! > > Suggested-by: Andy Lutomirski <luto@kernel.org> > Signed-off-by: Jann Horn <jannh@google.com> > --- > arch/x86/kernel/kprobes/core.c | 31 +------------------------------ > arch/x86/kernel/traps.c | 10 ++++++++++ > 2 files changed, 11 insertions(+), 30 deletions(-) > > diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c > index b0d1e81c96bb..467ac22691b0 100644 > --- a/arch/x86/kernel/kprobes/core.c > +++ b/arch/x86/kernel/kprobes/core.c > @@ -1028,42 +1028,13 @@ int kprobe_fault_handler(struct pt_regs *regs, int trapnr) > if (fixup_exception(regs, trapnr)) > return 1; > > - /* > - * fixup routine could not handle it, > - * Let do_page_fault() fix it. > - */ > + /* fixup routine could not handle it. */ > } > > return 0; > } > NOKPROBE_SYMBOL(kprobe_fault_handler); > > -/* > - * Wrapper routine for handling exceptions. > - */ > -int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val, > - void *data) > -{ > - struct die_args *args = data; > - int ret = NOTIFY_DONE; > - > - if (args->regs && user_mode(args->regs)) > - return ret; > - > - if (val == DIE_GPF) { > - /* > - * To be potentially processing a kprobe fault and to > - * trust the result from kprobe_running(), we have > - * be non-preemptible. > - */ > - if (!preemptible() && kprobe_running() && > - kprobe_fault_handler(args->regs, args->trapnr)) > - ret = NOTIFY_STOP; > - } > - return ret; > -} > -NOKPROBE_SYMBOL(kprobe_exceptions_notify); > - > bool arch_within_kprobe_blacklist(unsigned long addr) > { > bool is_in_entry_trampoline_section = false; > diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c > index e6db475164ed..bf9ab1aaa175 100644 > --- a/arch/x86/kernel/traps.c > +++ b/arch/x86/kernel/traps.c > @@ -556,6 +556,16 @@ do_general_protection(struct pt_regs *regs, long error_code) > > tsk->thread.error_code = error_code; > tsk->thread.trap_nr = X86_TRAP_GP; > + > + /* > + * To be potentially processing a kprobe fault and to > + * trust the result from kprobe_running(), we have to > + * be non-preemptible. > + */ > + if (!preemptible() && kprobe_running() && > + kprobe_fault_handler(regs, X86_TRAP_GP)) > + return; > + > if (notify_die(DIE_GPF, "general protection fault", regs, error_code, > X86_TRAP_GP, SIGSEGV) != NOTIFY_STOP) > die("general protection fault", regs, error_code); > -- > 2.19.0.rc0.228.g281dcd1b4d0-goog >
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c index b0d1e81c96bb..467ac22691b0 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -1028,42 +1028,13 @@ int kprobe_fault_handler(struct pt_regs *regs, int trapnr) if (fixup_exception(regs, trapnr)) return 1; - /* - * fixup routine could not handle it, - * Let do_page_fault() fix it. - */ + /* fixup routine could not handle it. */ } return 0; } NOKPROBE_SYMBOL(kprobe_fault_handler); -/* - * Wrapper routine for handling exceptions. - */ -int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val, - void *data) -{ - struct die_args *args = data; - int ret = NOTIFY_DONE; - - if (args->regs && user_mode(args->regs)) - return ret; - - if (val == DIE_GPF) { - /* - * To be potentially processing a kprobe fault and to - * trust the result from kprobe_running(), we have - * be non-preemptible. - */ - if (!preemptible() && kprobe_running() && - kprobe_fault_handler(args->regs, args->trapnr)) - ret = NOTIFY_STOP; - } - return ret; -} -NOKPROBE_SYMBOL(kprobe_exceptions_notify); - bool arch_within_kprobe_blacklist(unsigned long addr) { bool is_in_entry_trampoline_section = false; diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index e6db475164ed..bf9ab1aaa175 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -556,6 +556,16 @@ do_general_protection(struct pt_regs *regs, long error_code) tsk->thread.error_code = error_code; tsk->thread.trap_nr = X86_TRAP_GP; + + /* + * To be potentially processing a kprobe fault and to + * trust the result from kprobe_running(), we have to + * be non-preemptible. + */ + if (!preemptible() && kprobe_running() && + kprobe_fault_handler(regs, X86_TRAP_GP)) + return; + if (notify_die(DIE_GPF, "general protection fault", regs, error_code, X86_TRAP_GP, SIGSEGV) != NOTIFY_STOP) die("general protection fault", regs, error_code);
The opaque plumbing of #GP from do_general_protection() through notify_die() into kprobe_exceptions_notify() makes it hard to understand what's going on. Suggested-by: Andy Lutomirski <luto@kernel.org> Signed-off-by: Jann Horn <jannh@google.com> --- arch/x86/kernel/kprobes/core.c | 31 +------------------------------ arch/x86/kernel/traps.c | 10 ++++++++++ 2 files changed, 11 insertions(+), 30 deletions(-)