Messages in this thread | | | Date | Fri, 19 Jun 2009 08:35:04 -0400 | From | Mathieu Desnoyers <> | Subject | Re: [PATCH 4/7] add syscall tracepoints |
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* Frederic Weisbecker (fweisbec@gmail.com) wrote: > On Fri, Jun 12, 2009 at 05:24:54PM -0400, Jason Baron wrote: > > > > 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> > > > > --- > > arch/x86/kernel/ptrace.c | 6 ++++-- > > include/trace/syscall.h | 18 ++++++++++++++++++ > > kernel/tracepoint.c | 38 ++++++++++++++++++++++++++++++++++++++ > > 3 files changed, 60 insertions(+), 2 deletions(-) > > > > diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c > > index 09ecbde..1c7301a 100644 > > --- a/arch/x86/kernel/ptrace.c > > +++ b/arch/x86/kernel/ptrace.c > > @@ -36,6 +36,8 @@ > > #include <asm/ds.h> > > > > #include <trace/syscall.h> > > +DEFINE_TRACE(syscall_enter); > > +DEFINE_TRACE(syscall_exit); > > > > #include "tls.h" > > > > @@ -1498,7 +1500,7 @@ 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 +1526,7 @@ 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 8cfe515..d5d8310 100644 > > --- a/include/trace/syscall.h > > +++ b/include/trace/syscall.h > > @@ -2,6 +2,24 @@ > > #define _TRACE_SYSCALL_H > > > > #include <asm/ptrace.h> > > +#include <linux/tracepoint.h> > > + > > +extern void syscall_regfunc(void); > > +extern void syscall_unregfunc(void); > > + > > +DECLARE_TRACE_REG(syscall_enter, > > + TP_PROTO(struct pt_regs *regs, long id), > > + TP_ARGS(regs, id), > > + syscall_regfunc, > > + syscall_unregfunc > > +); > > + > > +DECLARE_TRACE_REG(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..5b34ff9 100644 > > --- a/kernel/tracepoint.c > > +++ b/kernel/tracepoint.c > > > > At a first glance I wasn't sure tracepoint.c is the right > place for these. > But indeed putting those two callbacks here avoids any > dependency to the syscall tracer when someone else needs > the syscall tracepoints. > > Well, I guess we can keep them there. > > > > > @@ -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 */ > > + > > +DEFINE_MUTEX(regfunc_mutex); > > +int sys_tracepoint_refcount; > > > Looks like regfunc_mutex is only there to protect > sys_tracepoint_refcount. May be you can just make it atomic_t? >
Nope, regfunc_mutex makes sure there is no disable/enable occuring concurrently. They only take a tasklist read lock, so they can happen concurrently if it wasn't for the regfunc_mutex.
Unless I'm missing something totally obvious about the refcount, the mutex is needed, and there is no need to go for an atomic type in this case.
Thanks,
Mathieu
> Thanks, > Frederic. > > > > + > > +void syscall_regfunc(void) > > +{ > > + unsigned long flags; > > + struct task_struct *g, *t; > > + > > + mutex_lock(®func_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(®func_mutex); > > +} > > + > > +void syscall_unregfunc(void) > > +{ > > + unsigned long flags; > > + struct task_struct *g, *t; > > + > > + mutex_lock(®func_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(®func_mutex); > > +} > > -- > > 1.6.0.6 > > >
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