Messages in this thread | | | Date | Thu, 07 Jun 2018 17:12:18 +0530 | From | "Naveen N. Rao" <> | Subject | Re: [RFC PATCH -tip v5 24/27] bpf: error-inject: kprobes: Clear current_kprobe and enable preempt in kprobe |
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Masami Hiramatsu wrote: > Clear current_kprobe and enable preemption in kprobe > even if pre_handler returns !0. > > This simplifies function override using kprobes. > > Jprobe used to require to keep the preemption disabled and > keep current_kprobe until it returned to original function > entry. For this reason kprobe_int3_handler() and similar > arch dependent kprobe handers checks pre_handler result > and exit without enabling preemption if the result is !0. > > After removing the jprobe, Kprobes does not need to > keep preempt disabled even if user handler returns !0 > anymore. > > But since the function override handler in error-inject > and bpf is also returns !0 if it overrides a function, > to balancing the preempt count, it enables preemption > and reset current kprobe by itself. > > That is a bad design that is very buggy. This fixes > such unbalanced preempt-count and current_kprobes setting > in kprobes, bpf and error-inject. > > Note: for powerpc and x86, this removes all preempt_disable > from kprobe_ftrace_handler because ftrace callbacks are > called under preempt disabled. > > Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> > Cc: Vineet Gupta <vgupta@synopsys.com> > Cc: Russell King <linux@armlinux.org.uk> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will.deacon@arm.com> > Cc: Tony Luck <tony.luck@intel.com> > Cc: Fenghua Yu <fenghua.yu@intel.com> > Cc: Ralf Baechle <ralf@linux-mips.org> > Cc: James Hogan <jhogan@kernel.org> > Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> > Cc: Paul Mackerras <paulus@samba.org> > Cc: Michael Ellerman <mpe@ellerman.id.au> > Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> > Cc: Heiko Carstens <heiko.carstens@de.ibm.com> > Cc: Yoshinori Sato <ysato@users.sourceforge.jp> > Cc: Rich Felker <dalias@libc.org> > Cc: "David S. Miller" <davem@davemloft.net> > Cc: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> > Cc: Josef Bacik <jbacik@fb.com> > Cc: Alexei Starovoitov <ast@kernel.org> > Cc: x86@kernel.org > Cc: linux-snps-arc@lists.infradead.org > Cc: linux-kernel@vger.kernel.org > Cc: linux-arm-kernel@lists.infradead.org > Cc: linux-ia64@vger.kernel.org > Cc: linux-mips@linux-mips.org > Cc: linuxppc-dev@lists.ozlabs.org > Cc: linux-s390@vger.kernel.org > Cc: linux-sh@vger.kernel.org > Cc: sparclinux@vger.kernel.org > --- > Changes in v5: > - Fix kprobe_ftrace_handler in arch/powerpc too. > --- > arch/arc/kernel/kprobes.c | 5 +++-- > arch/arm/probes/kprobes/core.c | 10 +++++----- > arch/arm64/kernel/probes/kprobes.c | 10 +++++----- > arch/ia64/kernel/kprobes.c | 13 ++++--------- > arch/mips/kernel/kprobes.c | 4 ++-- > arch/powerpc/kernel/kprobes-ftrace.c | 15 ++++++--------- > arch/powerpc/kernel/kprobes.c | 7 +++++--
For the powerpc bits: Acked-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Thanks, Naveen
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