1 files changed, 113 insertions, 0 deletions
diff --git a/include/linux/binfmt_misc.h b/include/linux/binfmt_misc.h
new file mode 100644
index 000000000000..8045b10dd3e5
--- /dev/null
+++ b/include/linux/binfmt_misc.h
@@ -0,0 +1,113 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_BINFMT_MISC_H
+#define _LINUX_BINFMT_MISC_H
+
+#include <linux/types.h>
+
+struct bpf_prog;
+struct file;
+struct linux_binprm;
+struct ucounts;
+struct user_namespace;
+
+#define BINFMT_MISC_OPS_NAME_MAX 16
+
+/* Longest name a 'B' entry can bind an interpreter under. */
+#define BINFMT_MISC_INTERP_NAME_MAX 32
+
+/* Most interpreters one entry can bind. */
+#define BINFMT_MISC_INTERP_MAX 100
+
+/**
+ * struct binfmt_misc_interp - an interpreter an entry was registered with
+ * @list: link in the entry's list, in registration order
+ * @file: the file, opened at registration and never resolved again
+ * @ucounts: the UCOUNT_BINFMT_MISC_INTERPRETERS charge the binding took
+ * @path: the path it was registered under, used as the name the interpreter
+ *        runs under; stored after @name in the same allocation
+ * @name: the name the load program selects it by; empty for the fixed
+ *        interpreter of a static 'F' entry
+ *
+ * Owned by the entry and living exactly as long as it does. The list head
+ * is handed to the handler's load program for the duration of one exec,
+ * which picks one with bpf_binprm_select_interp().
+ */
+struct binfmt_misc_interp {
+	struct list_head	list;
+	struct file		*file;
+	struct ucounts		*ucounts;
+	const char		*path;
+	char			name[];
+};
+
+const struct binfmt_misc_interp *
+binfmt_misc_find_interp(const struct list_head *interps, const char *name);
+
+/**
+ * enum bpf_binprm_flags - per-exec invocation flags a load program can request
+ * @BPF_BINPRM_PRESERVE_ARGV0: keep the caller's argv[0] (like the 'P' flag)
+ * @BPF_BINPRM_CREDENTIALS: compute credentials from the binary; implies execfd
+ *                          (like the 'C' flag)
+ * @BPF_BINPRM_EXECFD: pass the binary via AT_EXECFD (like the 'O' flag)
+ * @BPF_BINPRM_TRANSPARENT: leave argv untouched, the interpreter takes the
+ *                          binary from AT_EXECFD (like the 'T' flag); implies
+ *                          execfd, excludes preserve-argv0
+ * @BPF_BINPRM_LOADER: substitute the interpreter for the binary's PT_INTERP
+ *                     and run the binary as a native exec (like the 'L'
+ *                     flag); excludes every other flag
+ *
+ * Set from a load program with bpf_binprm_set_flags(). Unlike a static entry,
+ * a bpf handler chooses these per exec rather than once at registration.
+ */
+enum bpf_binprm_flags {
+	BPF_BINPRM_PRESERVE_ARGV0	= (1ULL << 0),
+	BPF_BINPRM_CREDENTIALS		= (1ULL << 1),
+	BPF_BINPRM_EXECFD		= (1ULL << 2),
+	BPF_BINPRM_TRANSPARENT		= (1ULL << 3),
+	BPF_BINPRM_LOADER		= (1ULL << 4),
+};
+
+/**
+ * struct binfmt_misc_ops - bpf-backed binary type handler
+ * @match: decide whether the handler applies to @bprm; consulted from the
+ *         entry lookup walk like static magic and extension matching, in
+ *         registration order with first-match-wins semantics; sleepable,
+ *         so it can read the binary to decide, but the verifier rejects
+ *         the interpreter selection kfuncs in it
+ * @load:  select an interpreter for the matched @bprm via
+ *         bpf_binprm_set_interp(), or one the entry bound via
+ *         bpf_binprm_select_interp(), and return zero; a match is
+ *         committed, so a failure fails the exec instead of falling
+ *         through to later entries; -ENOEXEC does not fail the exec but
+ *         moves on to the remaining binary formats
+ * @name: name that 'B' entries reference the handler by
+ */
+struct binfmt_misc_ops {
+	bool (*match)(struct linux_binprm *bprm);
+	int (*load)(struct linux_binprm *bprm);
+	char name[BINFMT_MISC_OPS_NAME_MAX];
+};
+
+#ifdef CONFIG_BINFMT_MISC_BPF
+const struct binfmt_misc_ops *binfmt_misc_get_ops(struct user_namespace *user_ns,
+						  const char *name);
+void binfmt_misc_put_ops(const struct binfmt_misc_ops *ops);
+bool bpf_prog_is_binfmt_misc_ops(const struct bpf_prog *prog);
+#else
+static inline const struct binfmt_misc_ops *
+binfmt_misc_get_ops(struct user_namespace *user_ns, const char *name)
+{
+	return NULL;
+}
+
+static inline void binfmt_misc_put_ops(const struct binfmt_misc_ops *ops)
+{
+}
+
+static inline bool bpf_prog_is_binfmt_misc_ops(const struct bpf_prog *prog)
+{
+	return false;
+}
+#endif /* CONFIG_BINFMT_MISC_BPF */
+
+#endif /* _LINUX_BINFMT_MISC_H */