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// 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",
};
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