Struct solana_rbpf::EbpfVmFixedMbuff

pub struct EbpfVmFixedMbuff<'a> { /* fields omitted */ }

A virtual machine to run eBPF program. This kind of VM is used for programs expecting to work on a metadata buffer containing pointers to packet data, but it internally handles the buffer so as to save the effort to manually handle the metadata buffer for the user.

This struct implements a static internal buffer that is passed to the program. The user has to indicate the offset values at which the eBPF program expects to find the start and the end of packet data in the buffer. On calling the execute_program() or execute_program_jit() functions, the struct automatically updates the addresses in this static buffer, at the appointed offsets, for the start and the end of the packet data the program is called upon.

Examples

This was compiled with clang from the following program, in C:

#include <linux/bpf.h>
#include "path/to/linux/samples/bpf/bpf_helpers.h"

SEC(".classifier")
int classifier(struct __sk_buff *skb)
{
  void *data = (void *)(long)skb->data;
  void *data_end = (void *)(long)skb->data_end;

  // Check program is long enough.
  if (data + 5 > data_end)
    return 0;

  return *((char *)data + 5);
}

Some small modifications have been brought to have it work, see comments.

let prog = &[
    0xb7, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // mov r0, 0
    // Here opcode 0x61 had to be replace by 0x79 so as to load a 8-bytes long address.
    // Also, offset 0x4c had to be replace with e.g. 0x40 so as to prevent the two pointers
    // from overlapping in the buffer.
    0x79, 0x12, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, // load pointer to mem from r1[0x40] to r2
    0x07, 0x02, 0x00, 0x00, 0x05, 0x00, 0x00, 0x00, // add r2, 5
    // Here opcode 0x61 had to be replace by 0x79 so as to load a 8-bytes long address.
    0x79, 0x11, 0x50, 0x00, 0x00, 0x00, 0x00, 0x00, // load ptr to mem_end from r1[0x50] to r1
    0x2d, 0x12, 0x03, 0x00, 0x00, 0x00, 0x00, 0x00, // if r2 > r1 skip 3 instructions
    0x71, 0x20, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // load r2 (= *(mem + 5)) into r0
    0x67, 0x00, 0x00, 0x00, 0x38, 0x00, 0x00, 0x00, // r0 >>= 56
    0xc7, 0x00, 0x00, 0x00, 0x38, 0x00, 0x00, 0x00, // r0 <<= 56 (arsh) extend byte sign to u64
    0x95, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00  // exit
];
let mem1 = &mut [
    0xaa, 0xbb, 0x11, 0x22, 0xcc, 0xdd
];
let mem2 = &mut [
    0xaa, 0xbb, 0x11, 0x22, 0xcc, 0x27
];

// Instantiate a VM. Note that we provide the start and end offsets for mem pointers.
let mut vm = solana_rbpf::EbpfVmFixedMbuff::new(Some(prog), 0x40, 0x50).unwrap();

// Provide only a reference to the packet data. We do not manage the metadata buffer.
let res = vm.execute_program(mem1).unwrap();
assert_eq!(res, 0xffffffffffffffdd);

let res = vm.execute_program(mem2).unwrap();
assert_eq!(res, 0x27);

Methods

impl<'a> EbpfVmFixedMbuff<'a>

pub fn new(     prog: Option<&'a [u8]>,     data_offset: usize,     data_end_offset: usize ) -> Result<EbpfVmFixedMbuff<'a>, Error>

Create a new virtual machine instance, and load an eBPF program into that instance. When attempting to load the program, it passes through a simple verifier.

Examples

let prog = &[
    0xb7, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // mov r0, 0
    0x79, 0x12, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, // load mem from r1[0x40] to r2
    0x07, 0x02, 0x00, 0x00, 0x05, 0x00, 0x00, 0x00, // add r2, 5
    0x79, 0x11, 0x50, 0x00, 0x00, 0x00, 0x00, 0x00, // load mem_end from r1[0x50] to r1
    0x2d, 0x12, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, // if r2 > r1 skip 3 instructions
    0x71, 0x20, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // load r2 (= *(mem + 5)) into r0
    0x95, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00  // exit
];

// Instantiate a VM. Note that we provide the start and end offsets for mem pointers.
let mut vm = solana_rbpf::EbpfVmFixedMbuff::new(Some(prog), 0x40, 0x50).unwrap();

pub fn set_program(     &mut self,     prog: &'a [u8],     data_offset: usize,     data_end_offset: usize ) -> Result<(), Error>

Load a new eBPF program into the virtual machine instance.

At the same time, load new offsets for storing pointers to start and end of packet data in the internal metadata buffer.

Examples

let prog1 = &[
    0xb7, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // mov r0, 0
    0x95, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00  // exit
];
let prog2 = &[
    0xb7, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // mov r0, 0
    0x79, 0x12, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, // load mem from r1[0x40] to r2
    0x07, 0x02, 0x00, 0x00, 0x05, 0x00, 0x00, 0x00, // add r2, 5
    0x79, 0x11, 0x50, 0x00, 0x00, 0x00, 0x00, 0x00, // load mem_end from r1[0x50] to r1
    0x2d, 0x12, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, // if r2 > r1 skip 3 instructions
    0x71, 0x20, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // load r2 (= *(mem + 5)) into r0
    0x95, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00  // exit
];

let mem = &mut [
    0xaa, 0xbb, 0x11, 0x22, 0xcc, 0x27,
];

let mut vm = solana_rbpf::EbpfVmFixedMbuff::new(Some(prog1), 0, 0).unwrap();
vm.set_program(prog2, 0x40, 0x50);

let res = vm.execute_program(mem).unwrap();
assert_eq!(res, 0x27);

pub fn set_verifier(&mut self, verifier: Verifier) -> Result<(), Error>

Set a new verifier function. The function should return an Error if the program should be rejected by the virtual machine. If a program has been loaded to the VM already, the verifier is immediately run.

Examples

use std::io::{Error, ErrorKind};
use solana_rbpf::ebpf;

// Define a simple verifier function.
fn verifier(prog: &[u8]) -> Result<(), Error> {
    let last_insn = ebpf::get_insn(prog, (prog.len() / ebpf::INSN_SIZE) - 1);
    if last_insn.opc != ebpf::EXIT {
        return Err(Error::new(ErrorKind::Other, 
                   "[Verifier] Error: program does not end with “EXIT” instruction"));
    }
    Ok(())
}

let prog1 = &[
    0xb7, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // mov r0, 0
    0x95, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00  // exit
];

// Instantiate a VM.
let mut vm = solana_rbpf::EbpfVmMbuff::new(Some(prog1)).unwrap();
// Change the verifier.
vm.set_verifier(verifier).unwrap();

pub fn set_max_instruction_count(&mut self, count: u64) -> Result<(), Error>

Set a cap on the maximum number of instructions that a program may execute. If the maximum is set to zero, then no cap will be applied.

Examples

use std::io::{Error, ErrorKind};
use solana_rbpf::ebpf;

let prog = &[
    0xb7, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // mov r0, 0
    0x95, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00  // exit
];

// Instantiate a VM.
let mut vm = solana_rbpf::EbpfVmMbuff::new(Some(prog)).unwrap();
// Set maximum instruction count.
vm.set_max_instruction_count(1000).unwrap();

pub fn get_last_instruction_count(&self) -> u64

Returns the number of instructions executed by the last program.

Examples

use std::io::{Error, ErrorKind};
use solana_rbpf::ebpf;

let prog = &[
    0xb7, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // mov r0, 0
    0x95, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00  // exit
];
 
let mem = &mut [
    0xaa, 0xbb, 0x11, 0x22, 0xcc, 0x09,
];

// Instantiate a VM.
let mut vm = solana_rbpf::EbpfVmFixedMbuff::new(Some(prog), 0x40, 0x50).unwrap();
// Execute the program.
let res = vm.execute_program(mem).unwrap();
// Get the number of instructions executed.
let count = vm.get_last_instruction_count();

pub fn register_helper(     &mut self,     key: u32,     function: HelperFunction ) -> Result<(), Error>

Register a built-in or user-defined helper function in order to use it later from within the eBPF program. The helper is registered into a hashmap, so the key can be any u32.

If using JIT-compiled eBPF programs, be sure to register all helpers before compiling the program. You should be able to change registered helpers after compiling, but not to add new ones (i.e. with new keys).

Examples

use solana_rbpf::helpers;

// This program was compiled with clang, from a C program containing the following single
// instruction: `return bpf_trace_printk("foo %c %c %c\n", 10, 1, 2, 3);`
let prog = &[
    0xb7, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // mov r0, 0
    0x79, 0x12, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, // load mem from r1[0x40] to r2
    0x07, 0x02, 0x00, 0x00, 0x05, 0x00, 0x00, 0x00, // add r2, 5
    0x79, 0x11, 0x50, 0x00, 0x00, 0x00, 0x00, 0x00, // load mem_end from r1[0x50] to r1
    0x2d, 0x12, 0x06, 0x00, 0x00, 0x00, 0x00, 0x00, // if r2 > r1 skip 6 instructions
    0x71, 0x21, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // load r2 (= *(mem + 5)) into r1
    0xb7, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // mov r2, 0
    0xb7, 0x03, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // mov r3, 0
    0xb7, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // mov r4, 0
    0xb7, 0x05, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // mov r5, 0
    0x85, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, // call helper with key 1
    0x95, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00  // exit
];

let mem = &mut [
    0xaa, 0xbb, 0x11, 0x22, 0xcc, 0x09,
];

// Instantiate a VM.
let mut vm = solana_rbpf::EbpfVmFixedMbuff::new(Some(prog), 0x40, 0x50).unwrap();

// Register a helper. This helper will store the result of the square root of r1 into r0.
vm.register_helper(1, helpers::sqrti);

let res = vm.execute_program(mem).unwrap();
assert_eq!(res, 3);

pub fn register_helper_ex(     &mut self,     name: &str,     verifier: Option<HelperVerifier>,     function: HelperFunction ) -> Result<(), Error>

Register a user-defined helper function in order to use it later from within the eBPF program. Normally helper functions are referred to by an index. (See helpers) but this function takes the name of the function. The name is then hashed into a 32 bit number and used in the call instructions imm field. If calling set_elf then the elf's relocations must reference this symbol using the same name. This can usually be achieved by building the elf with unresolved symbols (think extern foo(void)). If providing a program directly via set_program then any call instructions must already have the hash of the symbol name in its imm field. To generate the correct hash of the symbol name use ebpf::helpers::hash_symbol_name.

Helper functions may treat their arguments as pointers, but there are safety issues in doing so. To protect against bad pointer usage the VM will call the helper verifier function before calling the real helper. The user-supplied helper verifier should be implemented so that it checks the usage of the pointers and returns an error if a problem is encountered. For example, if the helper function treats argument 1 as a pointer to a string then the helper verification function must validate that argument 1 is indeed a valid pointer and that it is fully contained in one of the provided memory regions.

This function can be used along with jitted programs but be aware that unlike interpreted programs, jitted programs will not call the verification functions. If you don't inherently trust the parameters being passed to helpers then jitted programs must only use helper's arguments as values.

If using JIT-compiled eBPF programs, be sure to register all helpers before compiling the program. You should be able to change registered helpers after compiling, but not to add new ones (i.e. with new keys).

pub fn execute_program(&mut self, mem: &mut [u8]) -> Result<u64, Error>

Execute the program loaded, with the given packet data.

If the program is made to be compatible with Linux kernel, it is expected to load the address of the beginning and of the end of the memory area used for packet data from some metadata buffer, which in the case of this VM is handled internally. The offsets at which the addresses should be placed should have be set at the creation of the VM.

Examples

let prog = &[
    0xb7, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // mov r0, 0
    0x79, 0x12, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, // load mem from r1[0x40] to r2
    0x07, 0x02, 0x00, 0x00, 0x05, 0x00, 0x00, 0x00, // add r2, 5
    0x79, 0x11, 0x50, 0x00, 0x00, 0x00, 0x00, 0x00, // load mem_end from r1[0x50] to r1
    0x2d, 0x12, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, // if r2 > r1 skip 3 instructions
    0x71, 0x20, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // load r2 (= *(mem + 5)) into r0
    0x95, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00  // exit
];
let mem = &mut [
    0xaa, 0xbb, 0x11, 0x22, 0xcc, 0xdd
];

// Instantiate a VM. Note that we provide the start and end offsets for mem pointers.
let mut vm = solana_rbpf::EbpfVmFixedMbuff::new(Some(prog), 0x40, 0x50).unwrap();

// Provide only a reference to the packet data. We do not manage the metadata buffer.
let res = vm.execute_program(mem).unwrap();
assert_eq!(res, 0xdd);

pub fn jit_compile(&mut self) -> Result<(), Error>

JIT-compile the loaded program. No argument required for this.

If using helper functions, be sure to register them into the VM before calling this function.

Examples

let prog = &[
    0xb7, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // mov r0, 0
    0x79, 0x12, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, // load mem from r1[0x40] to r2
    0x07, 0x02, 0x00, 0x00, 0x05, 0x00, 0x00, 0x00, // add r2, 5
    0x79, 0x11, 0x50, 0x00, 0x00, 0x00, 0x00, 0x00, // load mem_end from r1[0x50] to r1
    0x2d, 0x12, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, // if r2 > r1 skip 3 instructions
    0x71, 0x20, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // load r2 (= *(mem + 5)) into r0
    0x95, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00  // exit
];

// Instantiate a VM. Note that we provide the start and end offsets for mem pointers.
let mut vm = solana_rbpf::EbpfVmFixedMbuff::new(Some(prog), 0x40, 0x50).unwrap();

vm.jit_compile();

pub unsafe fn execute_program_jit(     &mut self,     mem: &'a mut [u8] ) -> Result<u64, Error>

Execute the previously JIT-compiled program, with the given packet data, in a manner very similar to execute_program().

If the program is made to be compatible with Linux kernel, it is expected to load the address of the beginning and of the end of the memory area used for packet data from some metadata buffer, which in the case of this VM is handled internally. The offsets at which the addresses should be placed should have be set at the creation of the VM.

Safety

WARNING: JIT-compiled assembly code is not safe, in particular there is no runtime check for memory access; so if the eBPF program attempts erroneous accesses, this may end very bad (program may segfault). It may be wise to check that the program works with the interpreter before running the JIT-compiled version of it.

For this reason the function should be called from within an unsafe bloc.

Examples

let prog = &[
    0xb7, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // mov r0, 0
    0x79, 0x12, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, // load mem from r1[0x40] to r2
    0x07, 0x02, 0x00, 0x00, 0x05, 0x00, 0x00, 0x00, // add r2, 5
    0x79, 0x11, 0x50, 0x00, 0x00, 0x00, 0x00, 0x00, // load mem_end from r1[0x50] to r1
    0x2d, 0x12, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, // if r2 > r1 skip 3 instructions
    0x71, 0x20, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // load r2 (= *(mem + 5)) into r0
    0x95, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00  // exit
];
let mem = &mut [
    0xaa, 0xbb, 0x11, 0x22, 0xcc, 0xdd
];

// Instantiate a VM. Note that we provide the start and end offsets for mem pointers.
let mut vm = solana_rbpf::EbpfVmFixedMbuff::new(Some(prog), 0x40, 0x50).unwrap();

vm.jit_compile();

// Provide only a reference to the packet data. We do not manage the metadata buffer.
unsafe {
    let res = vm.execute_program_jit(mem).unwrap();
    assert_eq!(res, 0xdd);
}