Messages in this thread | | | Date | Wed, 28 Jan 2009 18:15:10 +0100 | Subject | Re: [PATCH] tracer for sys_open() - sreadahead | From | Frédéric Weisbecker <> |
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2009/1/28 Ananth N Mavinakayanahalli <ananth@in.ibm.com>: > On Wed, Jan 28, 2009 at 03:21:24PM +0100, Frédéric Weisbecker wrote: >> 2009/1/28 Ananth N Mavinakayanahalli <ananth@in.ibm.com>: >> > On Tue, Jan 27, 2009 at 11:43:05PM +0100, Frederic Weisbecker wrote: >> >> On Tue, Jan 27, 2009 at 12:08:04PM -0800, Kok, Auke wrote: > > ... > >> > Here is something I did sometime ago that uses utrace. It is per task >> > doesn't use ftrace and is just intended as a prototype. It traces both >> > syscalls and returns. >> > >> > --- >> > >> > Here is the beginnings of a simple utrace based strace. Right now, one >> > needs to invoke this program with a 'insmod <modname> tid=<tid>'. >> > >> > The output looks something like this: >> > [267352.641112] Attached to 32604 => 0xd8f60090 >> > [267353.981046] 2 >> > [267353.981085] 197 0x1 0xbff8cd84 0x86cff4 0x86d4c0 0x86d4c0 0xbff8cd50a = 0 >> > [267353.981097] 192 0x0 0x1000 0x3 0x22 0xffffffff 0x0 = b7f8d000 >> > [267353.981124] 4 0x1 0xb7f8d000 0xd 0xd 0xb7f8d000 0xbff8cda8 = d >> > [267353.981174] 4 0x1 0xb7f8d000 0x3 0x3 0xb7f8d000 0xbff8c7dc = 3 >> > [267353.981209] 252 0x0 0x0 0x86e0d0 0x0 0x86b274 0xbff8cee8 = >> > [267353.981215] Task 32604 exited >> > [267355.460180] Cannot find PID 32604 >> > >> > I know strace does a pretty print, but this is a quick and dirty >> > prototype. >> > --- >> > >> > #include <linux/module.h> >> > #include <linux/utrace.h> >> > #include <linux/err.h> >> > #include <asm/syscall.h> >> > >> > MODULE_DESCRIPTION("syscall trace"); >> > MODULE_LICENSE("GPL"); >> > >> > static int target_tid; >> > >> > module_param_named(tid, target_tid, int, 0); >> > >> > static u32 task_syscall_entry(u32 action, struct utrace_attached_engine *engine, >> > struct task_struct *task, struct pt_regs *regs) >> > { >> > long callno; >> > unsigned long args[6]; >> > >> > callno = syscall_get_nr(task, regs); >> > syscall_get_arguments(task, regs, 0, 6, args); >> > >> > printk(KERN_INFO "%ld 0x%lx 0x%lx 0x%lx 0x%lx 0x%lx 0x%lx = ", >> > callno, args[0], args[1], args[2], args[3], args[4], args[5]); >> > return UTRACE_RESUME; >> > } >> > >> > static u32 task_syscall_exit(u32 action, struct utrace_attached_engine *engine, >> > struct task_struct *task, struct pt_regs *regs) >> > { >> > long retval = syscall_get_return_value(task, regs); >> > printk("%lx\n", retval); >> > return UTRACE_RESUME; >> > } >> > >> > static u32 task_exit(enum utrace_resume_action action, >> > struct utrace_attached_engine *engine, struct task_struct *task, >> > long orig_code, long *code) >> > { >> > printk("\n"); >> > printk(KERN_INFO "Task %d exited\n", target_tid); >> > return UTRACE_DETACH; >> > } >> > >> > static const struct utrace_engine_ops syscall_ops = >> > { >> > .report_syscall_entry = task_syscall_entry, >> > .report_syscall_exit = task_syscall_exit, >> > .report_exit = task_exit, >> > }; >> > >> > static int __init strace_init(void) >> > { >> > struct pid *pid; >> > int ret = 0; >> > struct task_struct *target; >> > struct utrace_attached_engine *engine; >> > >> > pid = find_get_pid(target_tid); >> > if (pid == NULL) { >> > printk(KERN_ERR "Cannot find PID %d\n", target_tid); >> > ret = -ESRCH; >> > goto out; >> > } >> > >> > engine = utrace_attach_pid(pid, UTRACE_ATTACH_CREATE, &syscall_ops, 0); >> > if (IS_ERR(engine)) { >> > printk(KERN_ERR "utrace_attach_pid: %ld\n", PTR_ERR(engine)); >> > ret = -EINVAL; >> > goto out; >> > } else if (engine == NULL) { >> > printk(KERN_ERR "utrace_attach_pid => NULL\n"); >> > ret = -EINVAL; >> > goto out; >> > } else >> > printk(KERN_INFO "Attached to %d => 0x%p\n", >> > target_tid, engine); >> > >> > /* >> > * If utrace_attach_pid() succeeded above, we are sure the target >> > * is valid here >> > */ >> > target = pid_task(pid, PIDTYPE_PID); >> > put_pid(pid); >> > >> > ret = utrace_set_events(target, engine, UTRACE_EVENT_SYSCALL | >> > UTRACE_EVENT(EXIT)); >> > if (ret) >> > printk(KERN_ERR "utrace_set_events returned %d\n", ret); >> > >> > out: >> > return ret; >> > } >> > >> > static void __exit strace_exit(void) >> > { >> > int ret = 0; >> > struct pid *pid; >> > struct utrace_attached_engine *engine; >> > struct task_struct *target; >> > >> > pid = find_get_pid(target_tid); >> > if (pid == NULL) { >> > printk(KERN_ERR "Cannot find PID %d\n", target_tid); >> > return; >> > } >> > >> > target = pid_task(pid, PIDTYPE_PID); >> > put_pid(pid); >> > engine = utrace_attach_task(target, UTRACE_ATTACH_MATCH_OPS, >> > &syscall_ops, 0); >> > if (IS_ERR(engine)) >> > printk(KERN_ERR "Can't find self: %ld\n", PTR_ERR(engine)); >> > else if (engine == NULL) >> > printk(KERN_ERR "Can't find self: no match\n"); >> > else { >> > printk(KERN_INFO "Trying detach 0x%p from %d\n", >> > engine, target_tid); >> > ret = utrace_control(target, engine, UTRACE_DETACH); >> > if (ret) >> > printk(KERN_ERR "utrace_control returned %d\n", >> > ret); >> > } >> > } >> > >> > module_init(strace_init); >> > module_exit(strace_exit); >> > >> >> >> This is a very convenient Api. I would be glad to use it with ftrace. >> But, what is it's status currently? Some projects to merge it? > > Its currently available as a git tree: > git://git.kernel.org/pub/scm/linux/kernel/git/frob/linux-2.6-utrace.git > > There is work going on to merge it upstream. Roland McGrath will be able > to better answer when. However, one of the biggest requirements to merge > it is an in-kernel user. Hopefully Frank's prototype and/or an ftrace > integration of the above snippet should be incentive to push for some > in-tree users :-) > > Ananth >
I hope so. That would be used by the function graph tracer and a syscall tracer, and probably for other special tracers needs. If Ingo and Steven are ok with it. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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