Commit cd3fc3b9 authored by Jose E. Marchesi's avatar Jose E. Marchesi Committed by Alexei Starovoitov
Browse files

bpf: avoid uninitialized warnings in verifier_global_subprogs.c 



[Changes from V1:
- The warning to disable is -Wmaybe-uninitialized, not -Wuninitialized.
- This warning is only supported in GCC.]

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: default avatarJose 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>
Acked-by: default avatarYonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20240507184756.1772-1-jose.marchesi@oracle.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent e612b5c1

tools/testing/selftests/bpf/progs/verifier_global_subprogs.c

+7 −0
Original line number Diff line number Diff line
@@ -8,6 +8,13 @@ 
#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. */

#if !defined(__clang__)

#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"

#endif



int arr[1];

int unkn_idx;

const volatile bool call_dead_subprog = false;