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Date: Wed, 22 Nov 2017 22:26:15 +0000 From: alexander.levin@...izon.com To: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "stable@...r.kernel.org" <stable@...r.kernel.org> Cc: Masami Hiramatsu <mhiramat@...nel.org>, Alexei Starovoitov <ast@...com>, Alexei Starovoitov <ast@...nel.org>, Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>, Linus Torvalds <torvalds@...ux-foundation.org>, "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>, Peter Zijlstra <peterz@...radead.org>, Steven Rostedt <rostedt@...dmis.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...nel.org>, alexander.levin@...izon.com Subject: [PATCH AUTOSEL for 4.9 22/24] kprobes/x86: Disable preemption in ftrace-based jprobes From: Masami Hiramatsu <mhiramat@...nel.org> [ Upstream commit 5bb4fc2d8641219732eb2bb654206775a4219aca ] Disable preemption in ftrace-based jprobe handlers as described in Documentation/kprobes.txt: "Probe handlers are run with preemption disabled." This will fix jprobes behavior when CONFIG_PREEMPT=y. Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org> Cc: Alexei Starovoitov <ast@...com> Cc: Alexei Starovoitov <ast@...nel.org> Cc: Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@...ux-foundation.org> Cc: Paul E . McKenney <paulmck@...ux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@...radead.org> Cc: Steven Rostedt <rostedt@...dmis.org> Cc: Thomas Gleixner <tglx@...utronix.de> Link: http://lkml.kernel.org/r/150581530024.32348.9863783558598926771.stgit@devbox Signed-off-by: Ingo Molnar <mingo@...nel.org> Signed-off-by: Sasha Levin <alexander.levin@...izon.com> --- arch/x86/kernel/kprobes/ftrace.c | 23 ++++++++++++++--------- 1 file changed, 14 insertions(+), 9 deletions(-) diff --git a/arch/x86/kernel/kprobes/ftrace.c b/arch/x86/kernel/kprobes/ftrace.c index 5f8f0b3cc674..2c0b0b645a74 100644 --- a/arch/x86/kernel/kprobes/ftrace.c +++ b/arch/x86/kernel/kprobes/ftrace.c @@ -26,7 +26,7 @@ #include "common.h" static nokprobe_inline -int __skip_singlestep(struct kprobe *p, struct pt_regs *regs, +void __skip_singlestep(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb, unsigned long orig_ip) { /* @@ -41,20 +41,21 @@ int __skip_singlestep(struct kprobe *p, struct pt_regs *regs, __this_cpu_write(current_kprobe, NULL); if (orig_ip) regs->ip = orig_ip; - return 1; } int skip_singlestep(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb) { - if (kprobe_ftrace(p)) - return __skip_singlestep(p, regs, kcb, 0); - else - return 0; + if (kprobe_ftrace(p)) { + __skip_singlestep(p, regs, kcb, 0); + preempt_enable_no_resched(); + return 1; + } + return 0; } NOKPROBE_SYMBOL(skip_singlestep); -/* Ftrace callback handler for kprobes */ +/* Ftrace callback handler for kprobes -- called under preepmt disabed */ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, struct ftrace_ops *ops, struct pt_regs *regs) { @@ -77,13 +78,17 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, /* Kprobe handler expects regs->ip = ip + 1 as breakpoint hit */ regs->ip = ip + sizeof(kprobe_opcode_t); + /* To emulate trap based kprobes, preempt_disable here */ + preempt_disable(); __this_cpu_write(current_kprobe, p); kcb->kprobe_status = KPROBE_HIT_ACTIVE; - if (!p->pre_handler || !p->pre_handler(p, regs)) + if (!p->pre_handler || !p->pre_handler(p, regs)) { __skip_singlestep(p, regs, kcb, orig_ip); + preempt_enable_no_resched(); + } /* * If pre_handler returns !0, it sets regs->ip and - * resets current kprobe. + * resets current kprobe, and keep preempt count +1. */ } end: -- 2.11.0
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