Re: [PATCH 05/11 v2] kprobes/ftrace: Add recursion protection to the ftrace callback
On Fri, 30 Oct 2020 17:31:47 -0400 Steven Rostedt wrote: > From: "Steven Rostedt (VMware)" > > 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/20201028115613.140212...@goodmis.org > > Cc: Andrew Morton > Cc: Masami Hiramatsu > Cc: Guo Ren > Cc: "James E.J. Bottomley" > Cc: Helge Deller > Cc: Michael Ellerman > Cc: Benjamin Herrenschmidt > Cc: Paul Mackerras > Cc: Heiko Carstens > Cc: Vasily Gorbik > Cc: Christian Borntraeger > Cc: Thomas Gleixner > Cc: Borislav Petkov > Cc: x...@kernel.org > Cc: "H. Peter Anvin" > Cc: "Naveen N. Rao" > Cc: Anil S Keshavamurthy > Cc: "David S. Miller" > Cc: linux-c...@vger.kernel.org > Cc: linux-par...@vger.kernel.org > Cc: linuxppc-dev@lists.ozlabs.org > Cc: linux-s...@vger.kernel.org > Signed-off-by: Steven Rostedt (VMware) > --- > 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,
[PATCH 05/11 v2] kprobes/ftrace: Add recursion protection to the ftrace callback
From: "Steven Rostedt (VMware)" 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/20201028115613.140212...@goodmis.org Cc: Andrew Morton Cc: Masami Hiramatsu Cc: Guo Ren Cc: "James E.J. Bottomley" Cc: Helge Deller Cc: Michael Ellerman Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Heiko Carstens Cc: Vasily Gorbik Cc: Christian Borntraeger Cc: Thomas Gleixner Cc: Borislav Petkov Cc: x...@kernel.org Cc: "H. Peter Anvin" Cc: "Naveen N. Rao" Cc: Anil S Keshavamurthy Cc: "David S. Miller" Cc: linux-c...@vger.kernel.org Cc: linux-par...@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org Cc: linux-s...@vger.kernel.org Signed-off-by: Steven Rostedt (VMware) --- 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 (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 ---