Commit b1d1e904 authored by Masami Hiramatsu (Google)'s avatar Masami Hiramatsu (Google)
Browse files

tracing/probes: Support BTF argument on module functions 

Since the btf returned from bpf_get_btf_vmlinux() only covers functions in
the vmlinux, BTF argument is not available on the functions in the modules.
Use bpf_find_btf_id() instead of bpf_get_btf_vmlinux()+btf_find_name_kind()
so that BTF argument can find the correct struct btf and btf_type in it.
With this fix, fprobe events can use `$arg*` on module functions as below

 # grep nf_log_ip_packet /proc/kallsyms
ffffffffa0005c00 t nf_log_ip_packet	[nf_log_syslog]
ffffffffa0005bf0 t __pfx_nf_log_ip_packet	[nf_log_syslog]
 # echo 'f nf_log_ip_packet $arg*' > dynamic_events
 # cat dynamic_events
f:fprobes/nf_log_ip_packet__entry nf_log_ip_packet net=net pf=pf hooknum=hooknum skb=skb in=in out=out loginfo=loginfo prefix=prefix

To support the module's btf which is removable, the struct btf needs to be
ref-counted. So this also records the btf in the traceprobe_parse_context
and returns the refcount when the parse has done.

Link: https://lore.kernel.org/all/169272154223.160970.3507930084247934031.stgit@devnote2/



Suggested-by: default avatarAlexei Starovoitov <alexei.starovoitov@gmail.com>
Signed-off-by: default avatarMasami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent f8bbf8b9

include/linux/btf.h

+1 −0
Original line number Diff line number Diff line
@@ -211,6 +211,7 @@ struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type 
int btf_check_and_fixup_fields(const struct btf *btf, struct btf_record *rec);

bool btf_type_is_void(const struct btf_type *t);

s32 btf_find_by_name_kind(const struct btf *btf, const char *name, u8 kind);

s32 bpf_find_btf_id(const char *name, u32 kind, struct btf **btf_p);

const struct btf_type *btf_type_skip_modifiers(const struct btf *btf,

					       u32 id, u32 *res_id);

const struct btf_type *btf_type_resolve_ptr(const struct btf *btf,

kernel/bpf/btf.c

+1 −1
Original line number Diff line number Diff line
@@ -552,7 +552,7 @@ s32 btf_find_by_name_kind(const struct btf *btf, const char *name, u8 kind) 
	return -ENOENT;

}



static s32 bpf_find_btf_id(const char *name, u32 kind, struct btf **btf_p)

s32 bpf_find_btf_id(const char *name, u32 kind, struct btf **btf_p)

{

	struct btf *btf;

	s32 ret;

kernel/trace/trace_eprobe.c

+1 −3
Original line number Diff line number Diff line
@@ -807,13 +807,11 @@ static int trace_eprobe_tp_update_arg(struct trace_eprobe *ep, const char *argv[ 
	int ret;



	ret = traceprobe_parse_probe_arg(&ep->tp, i, argv[i], &ctx);

	if (ret)

		return ret;



	/* Handle symbols "@" */

	if (!ret)

		ret = traceprobe_update_arg(&ep->tp.args[i]);



	traceprobe_finish_parse(&ctx);

	return ret;

}

kernel/trace/trace_fprobe.c

+1 −0
Original line number Diff line number Diff line
@@ -1096,6 +1096,7 @@ static int __trace_fprobe_create(int argc, const char *argv[]) 
	}



out:

	traceprobe_finish_parse(&ctx);

	trace_probe_log_clear();

	kfree(new_argv);

	kfree(symbol);

kernel/trace/trace_kprobe.c

+1 −0
Original line number Diff line number Diff line
@@ -907,6 +907,7 @@ static int __trace_kprobe_create(int argc, const char *argv[]) 
	}



out:

	traceprobe_finish_parse(&ctx);

	trace_probe_log_clear();

	kfree(new_argv);

	kfree(symbol);