| 1 | |
| 2 | |
| 3 | * binfmt_misc_ops handler for the transparent-mode case: match a synthetic
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| 4 | * riscv ELF header and run the asserting interpreter transparently - the
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| 5 | * argument vector untouched, the binary in AT_EXECFD and mm->exe_file
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| 6 | * labeled with the binary.
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| 7 |
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| 8 | #include "vmlinux.h"
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| 9 | #include <bpf/bpf_helpers.h>
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| 10 | #include <bpf/bpf_tracing.h>
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| 11 |
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| 12 | char _license[] SEC("license") = "GPL";
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| 13 |
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| 14 | #define EI_CLASS 4
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| 15 | #define ELFCLASS64 2
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| 16 | #define EM_RISCV 243
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| 17 |
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| 18 | extern int bpf_binprm_set_interp(struct linux_binprm *bprm, const char *path,
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| 19 | size_t path__sz) __ksym;
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| 20 | extern int bpf_binprm_set_flags(struct linux_binprm *bprm,
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| 21 | enum bpf_binprm_flags flags) __ksym;
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| 22 |
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| 23 | SEC("struct_ops.s/match")
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| 24 | bool BPF_PROG(transparent_match, struct linux_binprm *bprm)
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| 25 | {
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| 26 | __u16 machine;
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| 27 |
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| 28 | if (bprm->buf[0] != 0x7f || bprm->buf[1] != 'E' ||
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| 29 | bprm->buf[2] != 'L' || bprm->buf[3] != 'F' ||
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| 30 | bprm->buf[EI_CLASS] != ELFCLASS64)
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| 31 | return false;
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| 32 |
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| 33 |
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| 34 | machine = (__u8)bprm->buf[18] | ((__u16)(__u8)bprm->buf[19] << 8);
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| 35 | return machine == EM_RISCV;
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| 36 | }
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| 37 |
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| 38 | SEC("struct_ops.s/load")
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| 39 | int BPF_PROG(transparent_load, struct linux_binprm *bprm)
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| 40 | {
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| 41 | char interp[] = "/tmp/binfmt_transparent_interp";
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| 42 | int err;
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| 43 |
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| 44 | err = bpf_binprm_set_flags(bprm, BPF_BINPRM_TRANSPARENT);
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| 45 | if (err)
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| 46 | return err;
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| 47 |
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| 48 |
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| 49 | return bpf_binprm_set_interp(bprm, interp, sizeof(interp));
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| 50 | }
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| 51 |
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| 52 | SEC(".struct_ops.link")
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| 53 | struct binfmt_misc_ops transparent = {
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| 54 | .match = (void *)transparent_match,
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| 55 | .load = (void *)transparent_load,
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| 56 | .name = "transparent",
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| 57 | };
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