// SPDX-License-Identifier: GPL-2.0/* * binfmt_misc_ops handler for the loader-substitution case: match the * marker the harness poked into the payload's e_ident padding and ask for * the selected interpreter to be substituted for the binary's PT_INTERP, * so the binary itself runs as a fully native exec. */#include "vmlinux.h"#include <bpf/bpf_helpers.h>#include <bpf/bpf_tracing.h> char _license[] SEC("license") = "GPL"; #define EI_CLASS	4#define EI_PAD		9#define ELFCLASS64	2 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(loader_match, struct linux_binprm *bprm){	if (bprm->buf[0] != 0x7f || bprm->buf[1] != 'E' ||	    bprm->buf[2] != 'L' || bprm->buf[3] != 'F' ||	    bprm->buf[EI_CLASS] != ELFCLASS64)		return false; 	/* The harness marks the payload with "LDRTST" at EI_PAD. */	return bprm->buf[EI_PAD + 0] == 'L' && bprm->buf[EI_PAD + 1] == 'D' &&	       bprm->buf[EI_PAD + 2] == 'R' && bprm->buf[EI_PAD + 3] == 'T' &&	       bprm->buf[EI_PAD + 4] == 'S' && bprm->buf[EI_PAD + 5] == 'T';} SEC("struct_ops.s/load")int BPF_PROG(loader_load, struct linux_binprm *bprm){	char interp[] = "/tmp/binfmt_loader_interp";	int err; 	err = bpf_binprm_set_flags(bprm, BPF_BINPRM_LOADER);	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 loader = {	.match = (void *)loader_match,	.load = (void *)loader_load,	.name = "loader",};