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Date: Mon, 26 Mar 2018 11:02:04 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Alexei Starovoitov <ast@...com>
Cc: <davem@...emloft.net>, <daniel@...earbox.net>,
<torvalds@...ux-foundation.org>, <peterz@...radead.org>,
<netdev@...r.kernel.org>, <kernel-team@...com>,
<linux-api@...r.kernel.org>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [PATCH v5 bpf-next 06/10] tracepoint: compute num_args at build
time
On Fri, 23 Mar 2018 19:30:34 -0700
Alexei Starovoitov <ast@...com> wrote:
> From: Alexei Starovoitov <ast@...nel.org>
>
> add fancy macro to compute number of arguments passed into tracepoint
> at compile time and store it as part of 'struct tracepoint'.
> The number is necessary to check safety of bpf program access that
> is coming in subsequent patch.
>
> for_each_tracepoint_range() api has no users inside the kernel.
> Make it more useful with ability to stop for_each() loop depending
> via callback return value.
> In such form it's used in subsequent patch.
I believe this is used by LTTng.
-- Steve
>
> Signed-off-by: Alexei Starovoitov <ast@...nel.org>
> ---
> include/linux/tracepoint-defs.h | 1 +
> include/linux/tracepoint.h | 28 +++++++++++++++++++---------
> include/trace/define_trace.h | 14 +++++++-------
> kernel/tracepoint.c | 27 ++++++++++++++++-----------
> 4 files changed, 43 insertions(+), 27 deletions(-)
>
> diff --git a/include/linux/tracepoint-defs.h b/include/linux/tracepoint-defs.h
> index 64ed7064f1fa..39a283c61c51 100644
> --- a/include/linux/tracepoint-defs.h
> +++ b/include/linux/tracepoint-defs.h
> @@ -33,6 +33,7 @@ struct tracepoint {
> int (*regfunc)(void);
> void (*unregfunc)(void);
> struct tracepoint_func __rcu *funcs;
> + u32 num_args;
> };
>
> #endif
> diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
> index c94f466d57ef..2194e7c31484 100644
> --- a/include/linux/tracepoint.h
> +++ b/include/linux/tracepoint.h
> @@ -40,9 +40,19 @@ tracepoint_probe_register_prio(struct tracepoint *tp, void *probe, void *data,
> int prio);
> extern int
> tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data);
> -extern void
> -for_each_kernel_tracepoint(void (*fct)(struct tracepoint *tp, void *priv),
> - void *priv);
> +
> +#ifdef CONFIG_TRACEPOINTS
> +void *
> +for_each_kernel_tracepoint(void *(*fct)(struct tracepoint *tp, void *priv),
> + void *priv);
> +#else
> +static inline void *
> +for_each_kernel_tracepoint(void *(*fct)(struct tracepoint *tp, void *priv),
> + void *priv)
> +{
> + return NULL;
> +}
> +#endif
>
> #ifdef CONFIG_MODULES
> struct tp_module {
> @@ -230,18 +240,18 @@ extern void syscall_unregfunc(void);
> * structures, so we create an array of pointers that will be used for iteration
> * on the tracepoints.
> */
> -#define DEFINE_TRACE_FN(name, reg, unreg) \
> +#define DEFINE_TRACE_FN(name, reg, unreg, num_args) \
> static const char __tpstrtab_##name[] \
> __attribute__((section("__tracepoints_strings"))) = #name; \
> struct tracepoint __tracepoint_##name \
> __attribute__((section("__tracepoints"))) = \
> - { __tpstrtab_##name, STATIC_KEY_INIT_FALSE, reg, unreg, NULL };\
> + { __tpstrtab_##name, STATIC_KEY_INIT_FALSE, reg, unreg, NULL, num_args };\
> static struct tracepoint * const __tracepoint_ptr_##name __used \
> __attribute__((section("__tracepoints_ptrs"))) = \
> &__tracepoint_##name;
>
> -#define DEFINE_TRACE(name) \
> - DEFINE_TRACE_FN(name, NULL, NULL);
> +#define DEFINE_TRACE(name, num_args) \
> + DEFINE_TRACE_FN(name, NULL, NULL, num_args);
>
> #define EXPORT_TRACEPOINT_SYMBOL_GPL(name) \
> EXPORT_SYMBOL_GPL(__tracepoint_##name)
> @@ -275,8 +285,8 @@ extern void syscall_unregfunc(void);
> return false; \
> }
>
> -#define DEFINE_TRACE_FN(name, reg, unreg)
> -#define DEFINE_TRACE(name)
> +#define DEFINE_TRACE_FN(name, reg, unreg, num_args)
> +#define DEFINE_TRACE(name, num_args)
> #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
> #define EXPORT_TRACEPOINT_SYMBOL(name)
>
> diff --git a/include/trace/define_trace.h b/include/trace/define_trace.h
> index d9e3d4aa3f6e..96b22ace9ae7 100644
> --- a/include/trace/define_trace.h
> +++ b/include/trace/define_trace.h
> @@ -25,7 +25,7 @@
>
> #undef TRACE_EVENT
> #define TRACE_EVENT(name, proto, args, tstruct, assign, print) \
> - DEFINE_TRACE(name)
> + DEFINE_TRACE(name, COUNT_ARGS(args))
>
> #undef TRACE_EVENT_CONDITION
> #define TRACE_EVENT_CONDITION(name, proto, args, cond, tstruct, assign, print) \
> @@ -39,24 +39,24 @@
> #undef TRACE_EVENT_FN
> #define TRACE_EVENT_FN(name, proto, args, tstruct, \
> assign, print, reg, unreg) \
> - DEFINE_TRACE_FN(name, reg, unreg)
> + DEFINE_TRACE_FN(name, reg, unreg, COUNT_ARGS(args))
>
> #undef TRACE_EVENT_FN_COND
> #define TRACE_EVENT_FN_COND(name, proto, args, cond, tstruct, \
> assign, print, reg, unreg) \
> - DEFINE_TRACE_FN(name, reg, unreg)
> + DEFINE_TRACE_FN(name, reg, unreg, COUNT_ARGS(args))
>
> #undef DEFINE_EVENT
> #define DEFINE_EVENT(template, name, proto, args) \
> - DEFINE_TRACE(name)
> + DEFINE_TRACE(name, COUNT_ARGS(args))
>
> #undef DEFINE_EVENT_FN
> #define DEFINE_EVENT_FN(template, name, proto, args, reg, unreg) \
> - DEFINE_TRACE_FN(name, reg, unreg)
> + DEFINE_TRACE_FN(name, reg, unreg, COUNT_ARGS(args))
>
> #undef DEFINE_EVENT_PRINT
> #define DEFINE_EVENT_PRINT(template, name, proto, args, print) \
> - DEFINE_TRACE(name)
> + DEFINE_TRACE(name, COUNT_ARGS(args))
>
> #undef DEFINE_EVENT_CONDITION
> #define DEFINE_EVENT_CONDITION(template, name, proto, args, cond) \
> @@ -64,7 +64,7 @@
>
> #undef DECLARE_TRACE
> #define DECLARE_TRACE(name, proto, args) \
> - DEFINE_TRACE(name)
> + DEFINE_TRACE(name, COUNT_ARGS(args))
>
> #undef TRACE_INCLUDE
> #undef __TRACE_INCLUDE
> diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
> index 671b13457387..3f2dc5738c2b 100644
> --- a/kernel/tracepoint.c
> +++ b/kernel/tracepoint.c
> @@ -502,17 +502,22 @@ static __init int init_tracepoints(void)
> __initcall(init_tracepoints);
> #endif /* CONFIG_MODULES */
>
> -static void for_each_tracepoint_range(struct tracepoint * const *begin,
> - struct tracepoint * const *end,
> - void (*fct)(struct tracepoint *tp, void *priv),
> - void *priv)
> +static void *for_each_tracepoint_range(struct tracepoint * const *begin,
> + struct tracepoint * const *end,
> + void *(*fct)(struct tracepoint *tp, void *priv),
> + void *priv)
> {
> struct tracepoint * const *iter;
> + void *ret;
>
> if (!begin)
> - return;
> - for (iter = begin; iter < end; iter++)
> - fct(*iter, priv);
> + return NULL;
> + for (iter = begin; iter < end; iter++) {
> + ret = fct(*iter, priv);
> + if (ret)
> + return ret;
> + }
> + return NULL;
> }
>
> /**
> @@ -520,11 +525,11 @@ static void for_each_tracepoint_range(struct tracepoint * const *begin,
> * @fct: callback
> * @priv: private data
> */
> -void for_each_kernel_tracepoint(void (*fct)(struct tracepoint *tp, void *priv),
> - void *priv)
> +void *for_each_kernel_tracepoint(void *(*fct)(struct tracepoint *tp, void *priv),
> + void *priv)
> {
> - for_each_tracepoint_range(__start___tracepoints_ptrs,
> - __stop___tracepoints_ptrs, fct, priv);
> + return for_each_tracepoint_range(__start___tracepoints_ptrs,
> + __stop___tracepoints_ptrs, fct, priv);
> }
> EXPORT_SYMBOL_GPL(for_each_kernel_tracepoint);
>
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