selftests/bpf: Check that JMP32 pointer vs zero jumps are not predictedgrafted

Add jmp32_ptr_vs_zero_jne: the fall-through of the 32-bit compare, which
the verifier used to skip, contains an out of bounds map value access,
hence w/o the previous patch the program is accepted. See previous patch
for detailed description.

Reported-by: Nicholas Carlini <npc@anthropic.com>
Suggested-by: Nicholas Carlini <npc@anthropic.com>
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/bpf/20260904083325.2083493-6-eddyz87@gmail.com
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>

1 files changed, 32 insertions, 0 deletions

diff --git a/scripts/mod/mk_elfconfig.c b/scripts/mod/mk_elfconfig.c
new file mode 100644
index 000000000..e8cee4e4b
--- /dev/null
+++ b/scripts/mod/mk_elfconfig.c
@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <elf.h>
+
+int
+main(int argc, char **argv)
+{
+	unsigned char ei[EI_NIDENT];
+
+	if (fread(ei, 1, EI_NIDENT, stdin) != EI_NIDENT) {
+		fprintf(stderr, "Error: input truncated\n");
+		return 1;
+	}
+	if (memcmp(ei, ELFMAG, SELFMAG) != 0) {
+		fprintf(stderr, "Error: not ELF\n");
+		return 1;
+	}
+	switch (ei[EI_CLASS]) {
+	case ELFCLASS32:
+		printf("#define KERNEL_ELFCLASS ELFCLASS32\n");
+		break;
+	case ELFCLASS64:
+		printf("#define KERNEL_ELFCLASS ELFCLASS64\n");
+		break;
+	default:
+		exit(1);
+	}
+
+	return 0;
+}