From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugzilla@gcc.gnu.org>
Received: by sourceware.org (Postfix, from userid 48)
	id F27583858C62; Wed,  3 Jan 2024 20:54:41 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org F27583858C62
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1704315281;
	bh=q7EZ84r2yh5U6DjESVutoAr/fBNN+ciAieJ+0/OZdsc=;
	h=From:To:Subject:Date:From;
	b=DGlncs8koLjcyqXeoNcavo2rGEC+0u7c7N2iZXAvR2TA4oPCJ1MqjAMuP331sOH3x
	 Zonhoz1rlvriNgc/CGEFMS0cxMVsJ+cAU1MJi8Eop6bjennPVWb2SJqK3O79ODSYCL
	 yiqIppMr0v65U+AENqND1CzOT/I8Xs241sMaZ4wk=
From: "cupertino.miranda at oracle dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/113225] New: bpf: attributekernel_helper function
 declarations create a BTF_FUNC_EXTERN.
Date: Wed, 03 Jan 2024 20:54:41 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: target
X-Bugzilla-Version: unknown
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: cupertino.miranda at oracle dot com
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: bug_id short_desc product version bug_status
 bug_severity priority component assigned_to reporter target_milestone
Message-ID: <bug-113225-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
List-Id: <gcc-bugs.sourceware.org>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D113225

            Bug ID: 113225
           Summary: bpf: attributekernel_helper function declarations
                    create a BTF_FUNC_EXTERN.
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: cupertino.miranda at oracle dot com
  Target Milestone: ---

When using attribute kernel_helper such as the one in the example:

extern int foo (int arg) __attribute__((kernel_helper (666)));

int bar ()
{
  return foo (20);
}

The following BTF entries are created:=20

[1] int 'int'(1U#B) size=3D4U#B offset=3D0UB#b bits=3D32UB#b SIGNED=20
[2] func_proto <anonymous> type=3D1
         param '' type=3D1
[3] func_proto <anonymous> type=3D1
[4] func 'foo'(5U#B) type=3D2 linkage=3D0 (extern)
[5] func 'bar'(9U#B) type=3D3 linkage=3D1 (global)

BTF information is generated for the extern function declaration, imposing =
some
problem to tools such as bpftool that relies on BTF information to validate
completeness of the BTF information.
Since kernel helpers are not true functions the BTF information created,
although accurate with how the function is declared, it is not accurate with
its semantics.

Plan resolution is to skip btf output to any attributed kernel_helper funct=
ion
declaration, since the BTF information in this case is not really required.=