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Message-Id: <1cc8a5580ae3a642fea137b7fe9c526402d4af33.1487098440.git.naveen.n.rao@linux.vnet.ibm.com>
Date: Wed, 15 Feb 2017 00:28:34 +0530
From: "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To: Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>,
Masami Hiramatsu <mhiramat@...nel.org>,
Michael Ellerman <mpe@...erman.id.au>
Cc: linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH 1/3] powerpc: kprobes: add support for KPROBES_ON_FTRACE
Allow kprobes to be placed on ftrace _mcount() call sites. This
optimization avoids the use of a trap, by riding on ftrace
infrastructure.
This depends on HAVE_DYNAMIC_FTRACE_WITH_REGS which depends on
MPROFILE_KERNEL, which is only currently enabled on powerpc64le with
newer toolchains.
Based on the x86 code by Masami.
Signed-off-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>
---
arch/powerpc/Kconfig | 1 +
arch/powerpc/include/asm/kprobes.h | 10 ++++
arch/powerpc/kernel/Makefile | 3 ++
arch/powerpc/kernel/kprobes-ftrace.c | 100 +++++++++++++++++++++++++++++++++++
arch/powerpc/kernel/kprobes.c | 4 +-
arch/powerpc/kernel/optprobes.c | 3 ++
6 files changed, 120 insertions(+), 1 deletion(-)
create mode 100644 arch/powerpc/kernel/kprobes-ftrace.c
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 260dd6a371e0..78419919556d 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -101,6 +101,7 @@ config PPC
select HAVE_EFFICIENT_UNALIGNED_ACCESS if !(CPU_LITTLE_ENDIAN && POWER7_CPU)
select HAVE_KPROBES
select HAVE_OPTPROBES if PPC64
+ select HAVE_KPROBES_ON_FTRACE
select HAVE_ARCH_KGDB
select HAVE_KRETPROBES
select HAVE_ARCH_TRACEHOOK
diff --git a/arch/powerpc/include/asm/kprobes.h b/arch/powerpc/include/asm/kprobes.h
index e7ada061aa12..3305a12286fa 100644
--- a/arch/powerpc/include/asm/kprobes.h
+++ b/arch/powerpc/include/asm/kprobes.h
@@ -153,6 +153,16 @@ extern int kprobe_exceptions_notify(struct notifier_block *self,
extern int kprobe_fault_handler(struct pt_regs *regs, int trapnr);
extern int kprobe_handler(struct pt_regs *regs);
extern int kprobe_post_handler(struct pt_regs *regs);
+#ifdef CONFIG_KPROBES_ON_FTRACE
+extern int skip_singlestep(struct kprobe *p, struct pt_regs *regs,
+ struct kprobe_ctlblk *kcb);
+#else
+static inline int skip_singlestep(struct kprobe *p, struct pt_regs *regs,
+ struct kprobe_ctlblk *kcb)
+{
+ return 0;
+}
+#endif
#else
static inline int kprobe_handler(struct pt_regs *regs) { return 0; }
static inline int kprobe_post_handler(struct pt_regs *regs) { return 0; }
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index a048b37b9b27..88b21427ccc7 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -101,6 +101,7 @@ obj-$(CONFIG_BOOTX_TEXT) += btext.o
obj-$(CONFIG_SMP) += smp.o
obj-$(CONFIG_KPROBES) += kprobes.o
obj-$(CONFIG_OPTPROBES) += optprobes.o optprobes_head.o
+obj-$(CONFIG_KPROBES_ON_FTRACE) += kprobes-ftrace.o
obj-$(CONFIG_UPROBES) += uprobes.o
obj-$(CONFIG_PPC_UDBG_16550) += legacy_serial.o udbg_16550.o
obj-$(CONFIG_STACKTRACE) += stacktrace.o
@@ -154,6 +155,8 @@ GCOV_PROFILE_machine_kexec_32.o := n
UBSAN_SANITIZE_machine_kexec_32.o := n
GCOV_PROFILE_kprobes.o := n
UBSAN_SANITIZE_kprobes.o := n
+GCOV_PROFILE_kprobes-ftrace.o := n
+UBSAN_SANITIZE_kprobes-ftrace.o := n
UBSAN_SANITIZE_vdso.o := n
extra-$(CONFIG_PPC_FPU) += fpu.o
diff --git a/arch/powerpc/kernel/kprobes-ftrace.c b/arch/powerpc/kernel/kprobes-ftrace.c
new file mode 100644
index 000000000000..0377b3013723
--- /dev/null
+++ b/arch/powerpc/kernel/kprobes-ftrace.c
@@ -0,0 +1,100 @@
+/*
+ * Dynamic Ftrace based Kprobes Optimization
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright (C) Hitachi Ltd., 2012
+ * Copyright 2016 Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>
+ * IBM Corporation
+ */
+#include <linux/kprobes.h>
+#include <linux/ptrace.h>
+#include <linux/hardirq.h>
+#include <linux/preempt.h>
+#include <linux/ftrace.h>
+
+static nokprobe_inline
+int __skip_singlestep(struct kprobe *p, struct pt_regs *regs,
+ struct kprobe_ctlblk *kcb, unsigned long orig_nip)
+{
+ /*
+ * Emulate singlestep (and also recover regs->nip)
+ * as if there is a nop
+ */
+ regs->nip = (unsigned long)p->addr + MCOUNT_INSN_SIZE;
+ if (unlikely(p->post_handler)) {
+ kcb->kprobe_status = KPROBE_HIT_SSDONE;
+ p->post_handler(p, regs, 0);
+ }
+ __this_cpu_write(current_kprobe, NULL);
+ if (orig_nip)
+ regs->nip = orig_nip;
+ 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;
+}
+NOKPROBE_SYMBOL(skip_singlestep);
+
+/* Ftrace callback handler for kprobes */
+void kprobe_ftrace_handler(unsigned long nip, unsigned long parent_nip,
+ struct ftrace_ops *ops, struct pt_regs *regs)
+{
+ struct kprobe *p;
+ struct kprobe_ctlblk *kcb;
+ unsigned long flags;
+
+ /* Disable irq for emulating a breakpoint and avoiding preempt */
+ local_irq_save(flags);
+ hard_irq_disable();
+
+ p = get_kprobe((kprobe_opcode_t *)nip);
+ if (unlikely(!p) || kprobe_disabled(p))
+ goto end;
+
+ kcb = get_kprobe_ctlblk();
+ if (kprobe_running()) {
+ kprobes_inc_nmissed_count(p);
+ } else {
+ unsigned long orig_nip = regs->nip;
+ /* Kprobe handler expects regs->nip = nip + 1 as breakpoint hit */
+ regs->nip = nip + sizeof(kprobe_opcode_t);
+
+ __this_cpu_write(current_kprobe, p);
+ kcb->kprobe_status = KPROBE_HIT_ACTIVE;
+ if (!p->pre_handler || !p->pre_handler(p, regs))
+ __skip_singlestep(p, regs, kcb, orig_nip);
+ /*
+ * If pre_handler returns !0, it sets regs->nip and
+ * resets current kprobe.
+ */
+ }
+end:
+ local_irq_restore(flags);
+}
+NOKPROBE_SYMBOL(kprobe_ftrace_handler);
+
+int arch_prepare_kprobe_ftrace(struct kprobe *p)
+{
+ p->ainsn.insn = NULL;
+ p->ainsn.boostable = -1;
+ return 0;
+}
diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index c213637b9d25..dab5e54f949c 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -233,7 +233,9 @@ int __kprobes kprobe_handler(struct pt_regs *regs)
}
p = __this_cpu_read(current_kprobe);
if (p->break_handler && p->break_handler(p, regs)) {
- goto ss_probe;
+ if (!skip_singlestep(p, regs, kcb))
+ goto ss_probe;
+ ret = 1;
}
}
goto no_kprobe;
diff --git a/arch/powerpc/kernel/optprobes.c b/arch/powerpc/kernel/optprobes.c
index e51a045f3d3b..a8f414a0b141 100644
--- a/arch/powerpc/kernel/optprobes.c
+++ b/arch/powerpc/kernel/optprobes.c
@@ -70,6 +70,9 @@ static unsigned long can_optimize(struct kprobe *p)
struct instruction_op op;
unsigned long nip = 0;
+ if (unlikely(kprobe_ftrace(p)))
+ return 0;
+
/*
* kprobe placed for kretprobe during boot time
* has a 'nop' instruction, which can be emulated.
--
2.11.0
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