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    Subject[PATCH 05/16] tracing: Add syscall tracepoints
    Date
    From: Jason Baron <jbaron@redhat.com>

    add two tracepoints in syscall exit and entry path, conditioned on
    TIF_SYSCALL_FTRACE. Supports the syscall trace event code.

    Signed-off-by: Jason Baron <jbaron@redhat.com>
    Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
    Cc: Steven Rostedt <rostedt@goodmis.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
    Cc: Jiaying Zhang <jiayingz@google.com>
    Cc: Martin Bligh <mbligh@google.com>
    Cc: Li Zefan <lizf@cn.fujitsu.com>
    Cc: Masami Hiramatsu <mhiramat@redhat.com>
    Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
    ---
    arch/x86/kernel/ptrace.c | 7 +++++--
    include/trace/syscall.h | 20 ++++++++++++++++++++
    kernel/tracepoint.c | 38 ++++++++++++++++++++++++++++++++++++++
    3 files changed, 63 insertions(+), 2 deletions(-)

    diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
    index 09ecbde..34dd6f1 100644
    --- a/arch/x86/kernel/ptrace.c
    +++ b/arch/x86/kernel/ptrace.c
    @@ -37,6 +37,9 @@

    #include <trace/syscall.h>

    +DEFINE_TRACE(syscall_enter);
    +DEFINE_TRACE(syscall_exit);
    +
    #include "tls.h"

    enum x86_regset {
    @@ -1498,7 +1501,7 @@ asmregparm long syscall_trace_enter(struct pt_regs *regs)
    ret = -1L;

    if (unlikely(test_thread_flag(TIF_SYSCALL_FTRACE)))
    - ftrace_syscall_enter(regs);
    + trace_syscall_enter(regs, regs->orig_ax);

    if (unlikely(current->audit_context)) {
    if (IS_IA32)
    @@ -1524,7 +1527,7 @@ asmregparm void syscall_trace_leave(struct pt_regs *regs)
    audit_syscall_exit(AUDITSC_RESULT(regs->ax), regs->ax);

    if (unlikely(test_thread_flag(TIF_SYSCALL_FTRACE)))
    - ftrace_syscall_exit(regs);
    + trace_syscall_exit(regs, regs->ax);

    if (test_thread_flag(TIF_SYSCALL_TRACE))
    tracehook_report_syscall_exit(regs, 0);
    diff --git a/include/trace/syscall.h b/include/trace/syscall.h
    index c55fcce..3951d77 100644
    --- a/include/trace/syscall.h
    +++ b/include/trace/syscall.h
    @@ -1,8 +1,28 @@
    #ifndef _TRACE_SYSCALL_H
    #define _TRACE_SYSCALL_H

    +#include <linux/tracepoint.h>
    +
    #include <asm/ptrace.h>

    +
    +extern void syscall_regfunc(void);
    +extern void syscall_unregfunc(void);
    +
    +DECLARE_TRACE_WITH_CALLBACK(syscall_enter,
    + TP_PROTO(struct pt_regs *regs, long id),
    + TP_ARGS(regs, id),
    + syscall_regfunc,
    + syscall_unregfunc
    +);
    +
    +DECLARE_TRACE_WITH_CALLBACK(syscall_exit,
    + TP_PROTO(struct pt_regs *regs, long ret),
    + TP_ARGS(regs, ret),
    + syscall_regfunc,
    + syscall_unregfunc
    +);
    +
    /*
    * A syscall entry in the ftrace syscalls array.
    *
    diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
    index 1ef5d3a..070a42b 100644
    --- a/kernel/tracepoint.c
    +++ b/kernel/tracepoint.c
    @@ -24,6 +24,7 @@
    #include <linux/tracepoint.h>
    #include <linux/err.h>
    #include <linux/slab.h>
    +#include <linux/sched.h>

    extern struct tracepoint __start___tracepoints[];
    extern struct tracepoint __stop___tracepoints[];
    @@ -577,3 +578,40 @@ static int init_tracepoints(void)
    __initcall(init_tracepoints);

    #endif /* CONFIG_MODULES */
    +
    +static DEFINE_MUTEX(regfunc_mutex);
    +static int sys_tracepoint_refcount;
    +
    +void syscall_regfunc(void)
    +{
    + unsigned long flags;
    + struct task_struct *g, *t;
    +
    + mutex_lock(&regfunc_mutex);
    + if (!sys_tracepoint_refcount) {
    + read_lock_irqsave(&tasklist_lock, flags);
    + do_each_thread(g, t) {
    + set_tsk_thread_flag(t, TIF_SYSCALL_FTRACE);
    + } while_each_thread(g, t);
    + read_unlock_irqrestore(&tasklist_lock, flags);
    + }
    + sys_tracepoint_refcount++;
    + mutex_unlock(&regfunc_mutex);
    +}
    +
    +void syscall_unregfunc(void)
    +{
    + unsigned long flags;
    + struct task_struct *g, *t;
    +
    + mutex_lock(&regfunc_mutex);
    + sys_tracepoint_refcount--;
    + if (!sys_tracepoint_refcount) {
    + read_lock_irqsave(&tasklist_lock, flags);
    + do_each_thread(g, t) {
    + clear_tsk_thread_flag(t, TIF_SYSCALL_FTRACE);
    + } while_each_thread(g, t);
    + read_unlock_irqrestore(&tasklist_lock, flags);
    + }
    + mutex_unlock(&regfunc_mutex);
    +}
    --
    1.6.2.3


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