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, 45 insertions, 0 deletions

diff --git a/scripts/objdump-func b/scripts/objdump-func
new file mode 100755
index 000000000..7b15b873d
--- /dev/null
+++ b/scripts/objdump-func
@@ -0,0 +1,45 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# Disassemble a single function.
+#
+# usage: objdump-func <file> <func> [<func> ...]
+
+set -o errexit
+set -o nounset
+
+OBJDUMP="${CROSS_COMPILE:-}objdump"
+
+command -v gawk >/dev/null 2>&1 || die "gawk isn't installed"
+
+usage() {
+	echo "usage: objdump-func <file> <func> [<func> ...]" >&2
+	exit 1
+}
+
+[[ $# -lt 2 ]] && usage
+
+OBJ=$1; shift
+FUNCS=("$@")
+
+${OBJDUMP} -wdr $OBJ | gawk -M -v _funcs="${FUNCS[*]}" '
+	BEGIN { split(_funcs, funcs); }
+	/^$/ { func_match=0; }
+	/<.*>:/ {
+		f = gensub(/.*<(.*)>:/, "\\1", 1);
+		for (i in funcs) {
+			# match compiler-added suffixes like ".cold", etc
+			if (f ~ "^" funcs[i] "(\\..*)?") {
+				func_match = 1;
+				base = strtonum("0x" $1);
+				break;
+			}
+		}
+	}
+	{
+		if (func_match) {
+			addr = strtonum("0x" $1);
+			printf("%04x ", addr - base);
+			print;
+		}
+	}'