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    SubjectRe: [PATCH -tip -v10 7/7] tracing: add kprobe-based event tracer
    Frederic Weisbecker wrote:
    >> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
    >> index 206cb7d..65945eb 100644
    >> --- a/kernel/trace/trace.h
    >> +++ b/kernel/trace/trace.h
    >> @@ -45,6 +45,8 @@ enum trace_type {
    >> TRACE_POWER,
    >> TRACE_BLK,
    >> TRACE_KSYM,
    >> + TRACE_KPROBE,
    >> + TRACE_KRETPROBE,
    >>
    >> __TRACE_LAST_TYPE,
    >> };
    >> @@ -227,6 +229,22 @@ struct trace_ksym {
    >> char ksym_name[KSYM_NAME_LEN];
    >> char p_name[TASK_COMM_LEN];
    >> };
    >> +#define TRACE_KPROBE_ARGS 6
    >> +
    >> +struct kprobe_trace_entry {
    >> + struct trace_entry ent;
    >> + unsigned long ip;
    >> + int nargs;
    >> + unsigned long args[TRACE_KPROBE_ARGS];
    >
    >
    >
    > I see that you actually make use of arg as a dynamic sizeable
    > array.
    > For clarity, args[TRACE_KPROBE_ARGS] could be args[0].
    >
    > It's just a neat and wouldn't affect the code nor the data
    > but would be clearer for readers of that code.

    Hmm. In that case, I think we'll need a new macro for field
    definition, like TRACE_FIELD_ZERO(type, item).

    >> +};
    >> +
    >> +struct kretprobe_trace_entry {
    >> + struct trace_entry ent;
    >> + unsigned long func;
    >> + unsigned long ret_ip;
    >> + int nargs;
    >> + unsigned long args[TRACE_KPROBE_ARGS];
    >> +};
    >
    >
    > ditto
    >
    >
    >
    >> /*
    >> * trace_flag_type is an enumeration that holds different
    >> @@ -344,6 +362,10 @@ extern void __ftrace_bad_type(void);
    >> IF_ASSIGN(var, ent, struct syscall_trace_exit, \
    >> TRACE_SYSCALL_EXIT); \
    >> IF_ASSIGN(var, ent, struct trace_ksym, TRACE_KSYM); \
    >> + IF_ASSIGN(var, ent, struct kprobe_trace_entry, \
    >> + TRACE_KPROBE); \
    >> + IF_ASSIGN(var, ent, struct kretprobe_trace_entry, \
    >> + TRACE_KRETPROBE); \
    >> __ftrace_bad_type(); \
    >> } while (0)
    >>
    >> diff --git a/kernel/trace/trace_event_types.h b/kernel/trace/trace_event_types.h
    >> index 6db005e..ec2e6f3 100644
    >> --- a/kernel/trace/trace_event_types.h
    >> +++ b/kernel/trace/trace_event_types.h
    >> @@ -175,4 +175,24 @@ TRACE_EVENT_FORMAT(kmem_free, TRACE_KMEM_FREE, kmemtrace_free_entry, ignore,
    >> TP_RAW_FMT("type:%u call_site:%lx ptr:%p")
    >> );
    >>
    >> +TRACE_EVENT_FORMAT(kprobe, TRACE_KPROBE, kprobe_trace_entry, ignore,
    >> + TRACE_STRUCT(
    >> + TRACE_FIELD(unsigned long, ip, ip)
    >> + TRACE_FIELD(int, nargs, nargs)
    >> + TRACE_FIELD_SPECIAL(unsigned long args[TRACE_KPROBE_ARGS],
    >> + args, TRACE_KPROBE_ARGS, args)
    >> + ),
    >> + TP_RAW_FMT("%08lx: args:0x%lx ...")
    >> +);
    >> +
    >> +TRACE_EVENT_FORMAT(kretprobe, TRACE_KRETPROBE, kretprobe_trace_entry, ignore,
    >> + TRACE_STRUCT(
    >> + TRACE_FIELD(unsigned long, func, func)
    >> + TRACE_FIELD(unsigned long, ret_ip, ret_ip)
    >> + TRACE_FIELD(int, nargs, nargs)
    >> + TRACE_FIELD_SPECIAL(unsigned long args[TRACE_KPROBE_ARGS],
    >> + args, TRACE_KPROBE_ARGS, args)
    >> + ),
    >> + TP_RAW_FMT("%08lx <- %08lx: args:0x%lx ...")
    >> +);
    >> #undef TRACE_SYSTEM
    >> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
    >> new file mode 100644
    >> index 0000000..0951512
    >> --- /dev/null
    >> +++ b/kernel/trace/trace_kprobe.c
    >> @@ -0,0 +1,1183 @@
    >> +/*
    >> + * kprobe based kernel tracer
    >> + *
    >> + * Created by Masami Hiramatsu <mhiramat@redhat.com>
    >> + *
    >> + * This program is free software; you can redistribute it and/or modify
    >> + * it under the terms of the GNU General Public License version 2 as
    >> + * published by the Free Software Foundation.
    >> + *
    >> + * 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
    >> + */
    >> +
    >> +#include <linux/module.h>
    >> +#include <linux/uaccess.h>
    >> +#include <linux/kprobes.h>
    >> +#include <linux/seq_file.h>
    >> +#include <linux/slab.h>
    >> +#include <linux/smp.h>
    >> +#include <linux/debugfs.h>
    >> +#include <linux/types.h>
    >> +#include <linux/string.h>
    >> +#include <linux/ctype.h>
    >> +#include <linux/ptrace.h>
    >> +
    >> +#include "trace.h"
    >> +#include "trace_output.h"
    >> +
    >> +#define MAX_ARGSTR_LEN 63
    >> +
    >> +/* currently, trace_kprobe only supports X86. */
    >> +
    >> +struct fetch_func {
    >> + unsigned long (*func)(struct pt_regs *, void *);
    >> + void *data;
    >> +};
    >> +
    >> +static __kprobes unsigned long call_fetch(struct fetch_func *f,
    >> + struct pt_regs *regs)
    >> +{
    >> + return f->func(regs, f->data);
    >> +}
    >> +
    >> +/* fetch handlers */
    >> +static __kprobes unsigned long fetch_register(struct pt_regs *regs,
    >> + void *offset)
    >> +{
    >> + return regs_get_register(regs, (unsigned)((unsigned long)offset));
    >> +}
    >> +
    >> +static __kprobes unsigned long fetch_stack(struct pt_regs *regs,
    >> + void *num)
    >> +{
    >> + return regs_get_kernel_stack_nth(regs, (unsigned)((unsigned long)num));
    >
    >
    > You seem to often use unsigned as an implicit type.
    > Would be better to explicitly use unsigned int.

    Agreed.

    > Anyway, I guess we can merge it in -tip and give it a try.

    Thank you!


    --
    Masami Hiramatsu

    Software Engineer
    Hitachi Computer Products (America), Inc.
    Software Solutions Division

    e-mail: mhiramat@redhat.com



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