On Fri, 30 Oct 2020 17:31:47 -0400 Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx> > > If a ftrace callback does not supply its own recursion protection and > does not set the RECURSION_SAFE flag in its ftrace_ops, then ftrace will > make a helper trampoline to do so before calling the callback instead of > just calling the callback directly. > > The default for ftrace_ops is going to change. It will expect that handlers > provide their own recursion protection, unless its ftrace_ops states > otherwise. > > Link: https://lkml.kernel.org/r/20201028115613.140212174@xxxxxxxxxxx > > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx> > Cc: Guo Ren <guoren@xxxxxxxxxx> > Cc: "James E.J. Bottomley" <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> > Cc: Helge Deller <deller@xxxxxx> > Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx> > Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> > Cc: Paul Mackerras <paulus@xxxxxxxxx> > Cc: Heiko Carstens <hca@xxxxxxxxxxxxx> > Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx> > Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Cc: Borislav Petkov <bp@xxxxxxxxx> > Cc: x86@xxxxxxxxxx > Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> > Cc: "Naveen N. Rao" <naveen.n.rao@xxxxxxxxxxxxx> > Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@xxxxxxxxx> > Cc: "David S. Miller" <davem@xxxxxxxxxxxxx> > Cc: linux-csky@xxxxxxxxxxxxxxx > Cc: linux-parisc@xxxxxxxxxxxxxxx > Cc: linuxppc-dev@xxxxxxxxxxxxxxxx > Cc: linux-s390@xxxxxxxxxxxxxxx > Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> > --- > arch/csky/kernel/probes/ftrace.c | 12 ++++++++++-- > arch/parisc/kernel/ftrace.c | 13 +++++++++++-- > arch/powerpc/kernel/kprobes-ftrace.c | 11 ++++++++++- > arch/s390/kernel/ftrace.c | 13 +++++++++++-- > arch/x86/kernel/kprobes/ftrace.c | 12 ++++++++++-- > 5 files changed, 52 insertions(+), 9 deletions(-) > > diff --git a/arch/csky/kernel/probes/ftrace.c b/arch/csky/kernel/probes/ftrace.c > index 5264763d05be..5eb2604fdf71 100644 > --- a/arch/csky/kernel/probes/ftrace.c > +++ b/arch/csky/kernel/probes/ftrace.c > @@ -13,16 +13,21 @@ int arch_check_ftrace_location(struct kprobe *p) > void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, > struct ftrace_ops *ops, struct pt_regs *regs) > { > + int bit; > bool lr_saver = false; > struct kprobe *p; > struct kprobe_ctlblk *kcb; > > - /* Preempt is disabled by ftrace */ > + bit = ftrace_test_recursion_trylock(); > + if (bit < 0) > + return; > + > + preempt_disable_notrace(); > p = get_kprobe((kprobe_opcode_t *)ip); > if (!p) { > p = get_kprobe((kprobe_opcode_t *)(ip - MCOUNT_INSN_SIZE)); > if (unlikely(!p) || kprobe_disabled(p)) > - return; > + goto out; > lr_saver = true; > } > > @@ -56,6 +61,9 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, > */ > __this_cpu_write(current_kprobe, NULL); > } > +out: > + preempt_enable_notrace(); > + ftrace_test_recursion_unlock(bit); > } > NOKPROBE_SYMBOL(kprobe_ftrace_handler); > > diff --git a/arch/parisc/kernel/ftrace.c b/arch/parisc/kernel/ftrace.c > index 63e3ecb9da81..4b1fdf15662c 100644 > --- a/arch/parisc/kernel/ftrace.c > +++ b/arch/parisc/kernel/ftrace.c > @@ -208,13 +208,19 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, > { > struct kprobe_ctlblk *kcb; > struct kprobe *p = get_kprobe((kprobe_opcode_t *)ip); > + int bit; > > - if (unlikely(!p) || kprobe_disabled(p)) > + bit = ftrace_test_recursion_trylock(); > + if (bit < 0) > return; > > + preempt_disable_notrace(); If we disable preempt here, we also move the get_kprobe() here as below. (get_kprobe() accesses percpu variable) p = get_kprobe((kprobe_opcode_t *)ip); > + if (unlikely(!p) || kprobe_disabled(p)) > + goto out; > + > if (kprobe_running()) { > kprobes_inc_nmissed_count(p); > - return; > + goto out; > } > > __this_cpu_write(current_kprobe, p); > @@ -235,6 +241,9 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, > } > } > __this_cpu_write(current_kprobe, NULL); > +out: > + preempt_enable_notrace(); > + ftrace_test_recursion_unlock(bit); > } > NOKPROBE_SYMBOL(kprobe_ftrace_handler); > > diff --git a/arch/powerpc/kernel/kprobes-ftrace.c b/arch/powerpc/kernel/kprobes-ftrace.c > index 972cb28174b2..5df8d50c65ae 100644 > --- a/arch/powerpc/kernel/kprobes-ftrace.c > +++ b/arch/powerpc/kernel/kprobes-ftrace.c > @@ -18,10 +18,16 @@ void kprobe_ftrace_handler(unsigned long nip, unsigned long parent_nip, > { > struct kprobe *p; > struct kprobe_ctlblk *kcb; > + int bit; > > + bit = ftrace_test_recursion_trylock(); > + if (bit < 0) > + return; > + > + preempt_disable_notrace(); > p = get_kprobe((kprobe_opcode_t *)nip); > if (unlikely(!p) || kprobe_disabled(p)) > - return; > + goto out; > > kcb = get_kprobe_ctlblk(); > if (kprobe_running()) { > @@ -52,6 +58,9 @@ void kprobe_ftrace_handler(unsigned long nip, unsigned long parent_nip, > */ > __this_cpu_write(current_kprobe, NULL); > } > +out: > + preempt_enable_notrace(); > + ftrace_test_recursion_unlock(bit); > } > NOKPROBE_SYMBOL(kprobe_ftrace_handler); > > diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c > index b388e87a08bf..88466d7fb6b2 100644 > --- a/arch/s390/kernel/ftrace.c > +++ b/arch/s390/kernel/ftrace.c > @@ -202,13 +202,19 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, > { > struct kprobe_ctlblk *kcb; > struct kprobe *p = get_kprobe((kprobe_opcode_t *)ip); > + int bit; > > - if (unlikely(!p) || kprobe_disabled(p)) > + bit = ftrace_test_recursion_trylock(); > + if (bit < 0) > return; > > + preempt_disable_notrace(); Ditto. Others look good to me. Thank you, > + if (unlikely(!p) || kprobe_disabled(p)) > + goto out; > + > if (kprobe_running()) { > kprobes_inc_nmissed_count(p); > - return; > + goto out; > } > > __this_cpu_write(current_kprobe, p); > @@ -228,6 +234,9 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, > } > } > __this_cpu_write(current_kprobe, NULL); > +out: > + preempt_enable_notrace(); > + ftrace_test_recursion_unlock(bit); > } > NOKPROBE_SYMBOL(kprobe_ftrace_handler); > > diff --git a/arch/x86/kernel/kprobes/ftrace.c b/arch/x86/kernel/kprobes/ftrace.c > index 681a4b36e9bb..a40a6cdfcca3 100644 > --- a/arch/x86/kernel/kprobes/ftrace.c > +++ b/arch/x86/kernel/kprobes/ftrace.c > @@ -18,11 +18,16 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, > { > struct kprobe *p; > struct kprobe_ctlblk *kcb; > + int bit; > > - /* Preempt is disabled by ftrace */ > + bit = ftrace_test_recursion_trylock(); > + if (bit < 0) > + return; > + > + preempt_disable_notrace(); > p = get_kprobe((kprobe_opcode_t *)ip); > if (unlikely(!p) || kprobe_disabled(p)) > - return; > + goto out; > > kcb = get_kprobe_ctlblk(); > if (kprobe_running()) { > @@ -52,6 +57,9 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, > */ > __this_cpu_write(current_kprobe, NULL); > } > +out: > + preempt_enable_notrace(); > + ftrace_test_recursion_unlock(bit); > } > NOKPROBE_SYMBOL(kprobe_ftrace_handler); > > -- > 2.28.0 > > -- Masami Hiramatsu <mhiramat@xxxxxxxxxx>
