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SubjectRe: [PATCH 4/7] add syscall tracepoints
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?

Thanks,
Frederic.


> +
> +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);
> +}
> --
> 1.6.0.6
>



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