Re: [PATCH v7 bpf-next 06/10] tracepoint: compute num_args at build time

Mathieu Desnoyers
2018-03-28T13:49:24Z

----- On Mar 27, 2018, at 10:11 PM, Alexei Starovoitov ast@fb.com wrote:

> From: Alexei Starovoitov <ast@kernel.org>
>
> 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.

Hi Alexei,

Given that only eBPF needs this parameter count, we can move
it to the struct bpf_raw_event_map newly introduced by Steven,
right ? This would reduce bloat of struct tracepoint. For instance,
we don't need to keep this count around when eBPF is configured
out.

Thanks,

Mathieu

>
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
> Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> ---
> include/linux/tracepoint-defs.h | 1 +
> include/linux/tracepoint.h | 12 ++++++------
> include/trace/define_trace.h | 14 +++++++-------
> 3 files changed, 14 insertions(+), 13 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..c92f4adbc0d7 100644
> --- a/include/linux/tracepoint.h
> +++ b/include/linux/tracepoint.h
> @@ -230,18 +230,18 @@ 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 +275,8 @@ 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
> --
> 2.9.5

--
Mathieu Desnoyers
EfficiOS Inc.