// SPDX-License-Identifier: GPL-2.0/* * binfmt_misc_ops handler for the selftest's fixed-interpreter case: match a * 64-bit aarch64 ELF header from the prefetched buffer and route it to a fixed * interpreter chosen by the program. This is the portable, self-contained * equivalent of routing a foreign binary to an emulator: it matches * programmatically and computes the interpreter, but points at a test binary * the harness installs rather than a system emulator. */#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_AARCH64	183 extern int bpf_binprm_set_interp(struct linux_binprm *bprm, const char *path,				 size_t path__sz) __ksym; /* * A magic-style decision needs nothing beyond the prefetched bprm->buf, * even though the match program could read the file. */SEC("struct_ops.s/match")bool BPF_PROG(bpf_interp_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_AARCH64;} SEC("struct_ops.s/load")int BPF_PROG(bpf_interp_load, struct linux_binprm *bprm){	/*	 * Keep the path on the (writable) stack: bpf_binprm_set_interp() takes	 * a sized memory arg and the verifier rejects a read-only .rodata	 * buffer for it. The harness installs the interpreter at this path.	 */	char interp[] = "/tmp/binfmt_bpf_interp"; 	/* @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 bpf_interp = {	.match = (void *)bpf_interp_match,	.load = (void *)bpf_interp_load,	.name = "bpf_interp",};