From: "Jose E. Marchesi" <jose.marchesi@oracle.com>
To: bpf@vger.kernel.org
Cc: "Jose E . Marchesi" <jose.marchesi@oracle.com>,
david.faust@oracle.com, cupertino.miranda@oracle.com,
Yonghong Song <yonghong.song@linux.dev>,
Eduard Zingerman <eddyz87@gmail.com>
Subject: [PATCH bpf-next] bpf: avoid uninitialized warnings in verifier_global_subprogs.c
Date: Tue, 7 May 2024 16:05:40 +0200 [thread overview]
Message-ID: <20240507140540.3972-1-jose.marchesi@oracle.com> (raw)
The BPF selftest verifier_global_subprogs.c contains code that
purposedly performs out of bounds access to memory, to check whether
the kernel verifier is able to catch them. For example:
__noinline int global_unsupp(const int *mem)
{
if (!mem)
return 0;
return mem[100]; /* BOOM */
}
With -O1 and higher and no inlining, GCC notices this fact and emits a
"maybe uninitialized" warning. This is by design. Note that the
emission of these warnings is highly dependent on the precise
optimizations that are performed.
This patch adds a compiler pragma to verifier_global_subprogs.c to
ignore these warnings.
Tested in bpf-next master.
No regressions.
Signed-off-by: Jose E. Marchesi <jose.marchesi@oracle.com>
Cc: david.faust@oracle.com
Cc: cupertino.miranda@oracle.com
Cc: Yonghong Song <yonghong.song@linux.dev>
Cc: Eduard Zingerman <eddyz87@gmail.com>
---
tools/testing/selftests/bpf/progs/verifier_global_subprogs.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/tools/testing/selftests/bpf/progs/verifier_global_subprogs.c b/tools/testing/selftests/bpf/progs/verifier_global_subprogs.c
index baff5ffe9405..d05dc218b7e9 100644
--- a/tools/testing/selftests/bpf/progs/verifier_global_subprogs.c
+++ b/tools/testing/selftests/bpf/progs/verifier_global_subprogs.c
@@ -8,6 +8,11 @@
#include "xdp_metadata.h"
#include "bpf_kfuncs.h"
+/* The compiler may be able to detect the access to uninitialized
+ memory in the routines performing out of bound memory accesses and
+ emit warnings about it. This is the case of GCC. */
+#pragma GCC diagnostic ignored "-Wuninitialized"
+
int arr[1];
int unkn_idx;
const volatile bool call_dead_subprog = false;
--
2.30.2
next reply other threads:[~2024-05-07 14:05 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-07 14:05 Jose E. Marchesi [this message]
2024-05-07 17:41 ` [PATCH bpf-next] bpf: avoid uninitialized warnings in verifier_global_subprogs.c Yonghong Song
2024-05-07 18:20 ` Jose E. Marchesi
2024-05-07 19:46 ` Yonghong Song
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