[PATCH v3 2/2] powerpc: Uprobes port to powerpc

From: Ananth N Mavinakayanahalli
Date: Thu Jul 26 2012 - 01:20:32 EST

From: Ananth N Mavinakayanahalli <ananth@xxxxxxxxxx>

This is the port of uprobes to powerpc. Usage is similar to x86.

[root@xxxx ~]# ./bin/perf probe -x /lib64/libc.so.6 malloc
Added new event:
probe_libc:malloc (on 0xb4860)

You can now use it in all perf tools, such as:

perf record -e probe_libc:malloc -aR sleep 1

[root@xxxx ~]# ./bin/perf record -e probe_libc:malloc -aR sleep 20
[ perf record: Woken up 22 times to write data ]
[ perf record: Captured and wrote 5.843 MB perf.data (~255302 samples) ]
[root@xxxx ~]# ./bin/perf report --stdio
...

# Samples: 83K of event 'probe_libc:malloc'
# Event count (approx.): 83484
#
# Overhead Command Shared Object Symbol
# ........ ............ ............. ..........
#
69.05% tar libc-2.12.so [.] malloc
28.57% rm libc-2.12.so [.] malloc
1.32% avahi-daemon libc-2.12.so [.] malloc
0.58% bash libc-2.12.so [.] malloc
0.28% sshd libc-2.12.so [.] malloc
0.08% irqbalance libc-2.12.so [.] malloc
0.05% bzip2 libc-2.12.so [.] malloc
0.04% sleep libc-2.12.so [.] malloc
0.03% multipathd libc-2.12.so [.] malloc
0.01% sendmail libc-2.12.so [.] malloc
0.01% automount libc-2.12.so [.] malloc

Patch applies on the current master branch of Linus' tree (bdc0077af).
The trap_nr addition patch is a prereq.

Signed-off-by: Ananth N Mavinakayanahalli <ananth@xxxxxxxxxx>
---

Tested on POWER6; I don't see anything here that should stop it from
working on a ppc32; since I don't have access to a ppc32 machine, it
would be good if somoene could verify that part.

V3:
Added abort_xol() logic for powerpc, using thread_struct.trap_nr to
determine if the stepped instruction caused an exception.

V2:
a. arch_uprobe_analyze_insn() now gets unsigned long addr.
b. Verified that mtmsr[d] and rfi[d] are handled correctly by
emulate_step() (no changes to this patch).

arch/powerpc/Kconfig | 3
arch/powerpc/include/asm/thread_info.h | 4
arch/powerpc/include/asm/uprobes.h | 50 +++++++++
arch/powerpc/kernel/Makefile | 1
arch/powerpc/kernel/signal.c | 6 +
arch/powerpc/kernel/uprobes.c | 174 +++++++++++++++++++++++++++++++++
6 files changed, 237 insertions(+), 1 deletion(-)

Index: linux-26jul/arch/powerpc/include/asm/thread_info.h
===================================================================
--- linux-26jul.orig/arch/powerpc/include/asm/thread_info.h
+++ linux-26jul/arch/powerpc/include/asm/thread_info.h
@@ -102,6 +102,7 @@ static inline struct thread_info *curren
#define TIF_RESTOREALL 11 /* Restore all regs (implies NOERROR) */
#define TIF_NOERROR 12 /* Force successful syscall return */
#define TIF_NOTIFY_RESUME 13 /* callback before returning to user */
+#define TIF_UPROBE 14 /* breakpointed or single-stepping */
#define TIF_SYSCALL_TRACEPOINT 15 /* syscall tracepoint instrumentation */

/* as above, but as bit values */
@@ -118,12 +119,13 @@ static inline struct thread_info *curren
#define _TIF_RESTOREALL (1<<TIF_RESTOREALL)
#define _TIF_NOERROR (1<<TIF_NOERROR)
#define _TIF_NOTIFY_RESUME (1<<TIF_NOTIFY_RESUME)
+#define _TIF_UPROBE (1<<TIF_UPROBE)
#define _TIF_SYSCALL_TRACEPOINT (1<<TIF_SYSCALL_TRACEPOINT)
#define _TIF_SYSCALL_T_OR_A (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
_TIF_SECCOMP | _TIF_SYSCALL_TRACEPOINT)

#define _TIF_USER_WORK_MASK (_TIF_SIGPENDING | _TIF_NEED_RESCHED | \
- _TIF_NOTIFY_RESUME)
+ _TIF_NOTIFY_RESUME | _TIF_UPROBE)
#define _TIF_PERSYSCALL_MASK (_TIF_RESTOREALL|_TIF_NOERROR)

/* Bits in local_flags */
Index: linux-26jul/arch/powerpc/include/asm/uprobes.h
===================================================================
--- /dev/null
+++ linux-26jul/arch/powerpc/include/asm/uprobes.h
@@ -0,0 +1,50 @@
+#ifndef _ASM_UPROBES_H
+#define _ASM_UPROBES_H
+/*
+ * User-space Probes (UProbes) for powerpc
+ *
+ * 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) IBM Corporation, 2007-2012
+ *
+ * Adapted from the x86 port by Ananth N Mavinakayanahalli <ananth@xxxxxxxxxx>
+ */
+
+#include <linux/notifier.h>
+
+typedef unsigned int uprobe_opcode_t;
+
+#define MAX_UINSN_BYTES 4
+#define UPROBE_XOL_SLOT_BYTES (MAX_UINSN_BYTES)
+
+#define UPROBE_SWBP_INSN 0x7fe00008
+#define UPROBE_SWBP_INSN_SIZE 4 /* swbp insn size in bytes */
+
+struct arch_uprobe {
+ u8 insn[MAX_UINSN_BYTES];
+};
+
+struct arch_uprobe_task {
+ unsigned long saved_trap_nr;
+};
+
+extern int arch_uprobe_analyze_insn(struct arch_uprobe *aup, struct mm_struct *mm, unsigned long addr);
+extern unsigned long uprobe_get_swbp_addr(struct pt_regs *regs);
+extern int arch_uprobe_pre_xol(struct arch_uprobe *aup, struct pt_regs *regs);
+extern int arch_uprobe_post_xol(struct arch_uprobe *aup, struct pt_regs *regs);
+extern bool arch_uprobe_xol_was_trapped(struct task_struct *tsk);
+extern int arch_uprobe_exception_notify(struct notifier_block *self, unsigned long val, void *data);
+extern void arch_uprobe_abort_xol(struct arch_uprobe *aup, struct pt_regs *regs);
+#endif /* _ASM_UPROBES_H */
Index: linux-26jul/arch/powerpc/kernel/Makefile
===================================================================
--- linux-26jul.orig/arch/powerpc/kernel/Makefile
+++ linux-26jul/arch/powerpc/kernel/Makefile
@@ -96,6 +96,7 @@ obj-$(CONFIG_MODULES) += ppc_ksyms.o
obj-$(CONFIG_BOOTX_TEXT) += btext.o
obj-$(CONFIG_SMP) += smp.o
obj-$(CONFIG_KPROBES) += kprobes.o
+obj-$(CONFIG_UPROBES) += uprobes.o
obj-$(CONFIG_PPC_UDBG_16550) += legacy_serial.o udbg_16550.o
obj-$(CONFIG_STACKTRACE) += stacktrace.o
obj-$(CONFIG_SWIOTLB) += dma-swiotlb.o
Index: linux-26jul/arch/powerpc/kernel/signal.c
===================================================================
--- linux-26jul.orig/arch/powerpc/kernel/signal.c
+++ linux-26jul/arch/powerpc/kernel/signal.c
@@ -11,6 +11,7 @@

#include <linux/tracehook.h>
#include <linux/signal.h>
+#include <linux/uprobes.h>
#include <linux/key.h>
#include <asm/hw_breakpoint.h>
#include <asm/uaccess.h>
@@ -157,6 +158,11 @@ static int do_signal(struct pt_regs *reg

void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags)
{
+ if (thread_info_flags & _TIF_UPROBE) {
+ clear_thread_flag(TIF_UPROBE);
+ uprobe_notify_resume(regs);
+ }
+
if (thread_info_flags & _TIF_SIGPENDING)
do_signal(regs);

Index: linux-26jul/arch/powerpc/kernel/uprobes.c
===================================================================
--- /dev/null
+++ linux-26jul/arch/powerpc/kernel/uprobes.c
@@ -0,0 +1,174 @@
+/*
+ * User-space Probes (UProbes) for powerpc
+ *
+ * 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) IBM Corporation, 2007-2012
+ *
+ * Adapted from the x86 port by Ananth N Mavinakayanahalli <ananth@xxxxxxxxxx>
+ */
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/ptrace.h>
+#include <linux/uprobes.h>
+#include <linux/uaccess.h>
+#include <linux/kdebug.h>
+
+#include <asm/sstep.h>
+
+#define UPROBE_TRAP_NR UINT_MAX
+
+/**
+ * arch_uprobe_analyze_insn
+ * @mm: the probed address space.
+ * @arch_uprobe: the probepoint information.
+ * @addr: vaddr to probe.
+ * Return 0 on success or a -ve number on error.
+ */
+int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long addr)
+{
+ if (addr & 0x03)
+ return -EINVAL;
+ return 0;
+}
+
+/*
+ * arch_uprobe_pre_xol - prepare to execute out of line.
+ * @auprobe: the probepoint information.
+ * @regs: reflects the saved user state of current task.
+ */
+int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+ struct arch_uprobe_task *autask = &current->utask->autask;
+
+ autask->saved_trap_nr = current->thread.trap_nr;
+ current->thread.trap_nr = UPROBE_TRAP_NR;
+ regs->nip = current->utask->xol_vaddr;
+ return 0;
+}
+
+/**
+ * uprobe_get_swbp_addr - compute address of swbp given post-swbp regs
+ * @regs: Reflects the saved state of the task after it has hit a breakpoint
+ * instruction.
+ * Return the address of the breakpoint instruction.
+ */
+unsigned long uprobe_get_swbp_addr(struct pt_regs *regs)
+{
+ return instruction_pointer(regs);
+}
+
+/*
+ * If xol insn itself traps and generates a signal (SIGILL/SIGSEGV/etc),
+ * then detect the case where a singlestepped instruction jumps back to its
+ * own address. It is assumed that anything like do_page_fault/do_trap/etc
+ * sets thread.trap_nr != -1.
+ *
+ * arch_uprobe_pre_xol/arch_uprobe_post_xol save/restore thread.trap_nr,
+ * arch_uprobe_xol_was_trapped() simply checks that ->trap_nr is not equal to
+ * UPROBE_TRAP_NR == -1 set by arch_uprobe_pre_xol().
+ */
+bool arch_uprobe_xol_was_trapped(struct task_struct *t)
+{
+ if (t->thread.trap_nr != UPROBE_TRAP_NR)
+ return true;
+
+ return false;
+}
+
+/*
+ * Called after single-stepping. To avoid the SMP problems that can
+ * occur when we temporarily put back the original opcode to
+ * single-step, we single-stepped a copy of the instruction.
+ *
+ * This function prepares to resume execution after the single-step.
+ */
+int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+ struct uprobe_task *utask = current->utask;
+
+ WARN_ON_ONCE(current->thread.trap_nr != UPROBE_TRAP_NR);
+
+ current->thread.trap_nr = utask->autask.saved_trap_nr;
+
+ /*
+ * On powerpc, except for loads and stores, most instructions
+ * including ones that alter code flow (branches, calls, returns)
+ * are emulated in the kernel. We get here only if the emulation
+ * support doesn't exist and have to fix-up the next instruction
+ * to be executed.
+ */
+ regs->nip = utask->vaddr + MAX_UINSN_BYTES;
+ return 0;
+}
+
+/* callback routine for handling exceptions. */
+int arch_uprobe_exception_notify(struct notifier_block *self, unsigned long val, void *data)
+{
+ struct die_args *args = data;
+ struct pt_regs *regs = args->regs;
+
+ /* We are only interested in userspace traps */
+ if (regs && !user_mode(regs))
+ return NOTIFY_DONE;
+
+ switch (val) {
+ case DIE_BPT:
+ if (uprobe_pre_sstep_notifier(regs))
+ return NOTIFY_STOP;
+ break;
+ case DIE_SSTEP:
+ if (uprobe_post_sstep_notifier(regs))
+ return NOTIFY_STOP;
+ default:
+ break;
+ }
+ return NOTIFY_DONE;
+}
+
+/*
+ * This function gets called when XOL instruction either gets trapped or
+ * the thread has a fatal signal, so reset the instruction pointer to its
+ * probed address.
+ */
+void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+ struct uprobe_task *utask = current->utask;
+
+ current->thread.trap_nr = utask->autask.saved_trap_nr;
+ instruction_pointer_set(regs, utask->vaddr);
+}
+
+/*
+ * See if the instruction can be emulated.
+ * Returns true if instruction was emulated, false otherwise.
+ */
+bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+ int ret;
+ unsigned int insn;
+
+ memcpy(&insn, auprobe->insn, MAX_UINSN_BYTES);
+
+ /*
+ * emulate_step() returns 1 if the insn was successfully emulated.
+ * For all other cases, we need to single-step in hardware.
+ */
+ ret = emulate_step(regs, insn);
+ if (ret > 0)
+ return true;
+
+ return false;
+}
Index: linux-26jul/arch/powerpc/Kconfig
===================================================================
--- linux-26jul.orig/arch/powerpc/Kconfig
+++ linux-26jul/arch/powerpc/Kconfig
@@ -237,6 +237,9 @@ config PPC_OF_PLATFORM_PCI
config ARCH_SUPPORTS_DEBUG_PAGEALLOC
def_bool y

+config ARCH_SUPPORTS_UPROBES
+ def_bool y
+
config PPC_ADV_DEBUG_REGS
bool
depends on 40x || BOOKE

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