1 files changed, 57 insertions, 0 deletions
diff --git a/tools/testing/selftests/exec/transparent.bpf.c b/tools/testing/selftests/exec/transparent.bpf.c
new file mode 100644
index 000000000000..7632019ebe69
--- /dev/null
+++ b/tools/testing/selftests/exec/transparent.bpf.c
@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * binfmt_misc_ops handler for the transparent-mode case: match a synthetic
+ * riscv ELF header and run the asserting interpreter transparently - the
+ * argument vector untouched, the binary in AT_EXECFD and mm->exe_file
+ * labeled with the binary.
+ */
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+#define EI_CLASS	4
+#define ELFCLASS64	2
+#define EM_RISCV	243
+
+extern int bpf_binprm_set_interp(struct linux_binprm *bprm, const char *path,
+				 size_t path__sz) __ksym;
+extern int bpf_binprm_set_flags(struct linux_binprm *bprm,
+				enum bpf_binprm_flags flags) __ksym;
+
+SEC("struct_ops.s/match")
+bool BPF_PROG(transparent_match, struct linux_binprm *bprm)
+{
+	__u16 machine;
+
+	if (bprm->buf[0] != 0x7f || bprm->buf[1] != 'E' ||
+	    bprm->buf[2] != 'L' || bprm->buf[3] != 'F' ||
+	    bprm->buf[EI_CLASS] != ELFCLASS64)
+		return false;
+
+	/* e_machine is a 16-bit little-endian field at offset 18. */
+	machine = (__u8)bprm->buf[18] | ((__u16)(__u8)bprm->buf[19] << 8);
+	return machine == EM_RISCV;
+}
+
+SEC("struct_ops.s/load")
+int BPF_PROG(transparent_load, struct linux_binprm *bprm)
+{
+	char interp[] = "/tmp/binfmt_transparent_interp";
+	int err;
+
+	err = bpf_binprm_set_flags(bprm, BPF_BINPRM_TRANSPARENT);
+	if (err)
+		return err;
+
+	/* @path__sz includes the terminating NUL; 0 commits the selection. */
+	return bpf_binprm_set_interp(bprm, interp, sizeof(interp));
+}
+
+SEC(".struct_ops.link")
+struct binfmt_misc_ops transparent = {
+	.match = (void *)transparent_match,
+	.load = (void *)transparent_load,
+	.name = "transparent",
+};