[gcc r14-7011] bpf: Correct BTF for kernel_helper attributed decls

[Cupertino Miranda]

https://gcc.gnu.org/g:dfc88fb51c1f9c26215adf6a308c18e23992cdd9

commit r14-7011-gdfc88fb51c1f9c26215adf6a308c18e23992cdd9
Author: Cupertino Miranda <cupertino.miranda@oracle.com>
Date:   Wed Jan 3 11:37:34 2024 +0000

    bpf: Correct BTF for kernel_helper attributed decls
    
    This patch fix a problem with kernel_helper attribute BTF information,
    which incorrectly generates BTF_KIND_FUNC entry.
    This BTF entry although accurate with traditional extern function
    declarations, once the function is attributed with kernel_helper, it is
    semantically incompatible of the kernel helpers in BPF infrastructure.
    
    gcc/ChangeLog:
            PR target/113225
            * btfout.cc (btf_collect_datasec): Skip creating BTF info for
            extern and kernel_helper attributed function decls.
    gcc/testsuite/ChangeLog:
            * gcc.target/bpf/attr-kernel-helper.c: New test.

Diff:
---
 gcc/btfout.cc                                     |  7 +++++++
 gcc/testsuite/gcc.target/bpf/attr-kernel-helper.c | 15 +++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/gcc/btfout.cc b/gcc/btfout.cc
index 669d357dfd6..dcf751f8fe0 100644
--- a/gcc/btfout.cc
+++ b/gcc/btfout.cc
@@ -35,6 +35,8 @@ along with GCC; see the file COPYING3.  If not see
 #include "diagnostic-core.h"
 #include "cgraph.h"
 #include "varasm.h"
+#include "stringpool.h"  /* For lookup_attribute.  */
+#include "attribs.h" /* For lookup_attribute.  */
 #include "dwarf2out.h" /* For lookup_decl_die.  */
 
 static int btf_label_num;
@@ -440,6 +442,11 @@ btf_collect_datasec (ctf_container_ref ctfc)
       if (dtd == NULL)
 	continue;
 
+      if (DECL_EXTERNAL (func->decl)
+	  && (lookup_attribute ("kernel_helper",
+				DECL_ATTRIBUTES (func->decl))) != NULL_TREE)
+	continue;
+
       /* Functions actually get two types: a BTF_KIND_FUNC_PROTO, and
 	 also a BTF_KIND_FUNC.  But the CTF container only allocates one
 	 type per function, which matches closely with BTF_KIND_FUNC_PROTO.
diff --git a/gcc/testsuite/gcc.target/bpf/attr-kernel-helper.c b/gcc/testsuite/gcc.target/bpf/attr-kernel-helper.c
new file mode 100644
index 00000000000..7c5a0007c97
--- /dev/null
+++ b/gcc/testsuite/gcc.target/bpf/attr-kernel-helper.c
@@ -0,0 +1,15 @@
+/* Basic test for kernel_helper attribute BTF information.  */
+
+/* { dg-do compile } */
+/* { dg-options "-O0 -dA -gbtf" } */
+
+extern int foo_helper(int) __attribute((kernel_helper(42)));
+extern int foo_nohelper(int);
+
+int bar (int arg)
+{
+  return foo_helper (arg) + foo_nohelper (arg);
+}
+
+/* { dg-final { scan-assembler-times "BTF_KIND_FUNC 'foo_nohelper'" 1 } } */
+/* { dg-final { scan-assembler-times "BTF_KIND_FUNC 'foo_helper'" 0 } } */