bmputil 1.0.0

Black Magic Probe companion utility
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98

// SPDX-License-Identifier: MIT OR Apache-2.0
// SPDX-FileCopyrightText: 2022-2025 1BitSquared <info@1bitsquared.com>
// SPDX-FileContributor: Written by Mikaela Szekely <mikaela.szekely@qyriad.me>
// SPDX-FileContributor: Modified by Rachel Mant <git@dragonmux.network>

use color_eyre::eyre::Result;
use goblin::elf::{Elf, SectionHeader};
use goblin::error::Error as GoblinError;

/// Convenience extensions to [Elf].
trait ElfExt
{
	/// Get a reference to a section header with the given name. Returns None if
	/// a section by that name does not exist.
	fn get_section_by_name(&self, name: &str) -> Option<&goblin::elf::SectionHeader>;
}

impl<'a> ElfExt for Elf<'a>
{
	fn get_section_by_name(&self, name: &str) -> Option<&goblin::elf::SectionHeader>
	{
		for section in &self.section_headers {
			let parsed_name = self.shdr_strtab.get_at(section.sh_name)?;

			if parsed_name == name {
				return Some(section);
			}
		}

		None
	}
}

/// Convenience extensions to [SectionHeader].
trait SectionHeaderExt
{
	/// Get the raw data of this section, given the full ELF data.
	fn get_data<'s>(&'s self, parent_data: &'s [u8]) -> Result<&'s [u8]>;
}

impl SectionHeaderExt for SectionHeader
{
	fn get_data<'s>(&'s self, parent_data: &'s [u8]) -> Result<&'s [u8]>
	{
		let start_idx = self.sh_offset as usize;
		let size = self.sh_size;
		let end_idx = start_idx + size as usize;
		let data: &[u8] = parent_data.get(start_idx..end_idx).ok_or_else(|| {
			GoblinError::Malformed(format!(
				"ELF section header does not point to a valid section (offset [{}..{}])",
				start_idx, end_idx,
			))
		})?;

		Ok(data)
	}
}

/// Extracts binary data from raw ELF data.
///
/// This should be equivalent to `$ arm-none-eabi-objcopy -Obinary`, but is not yet robust
/// enough to automatically detect what sections should be copied.
/// Currently, `.text`, `.ARM.exidx`, and `.data` are copied.
pub fn extract_binary(elf_data: &[u8]) -> Result<Vec<u8>>
{
	let elf = Elf::parse(elf_data)?;

	// FIXME: Dynamically detect what sections should be copied.
	// arm-none-eabi-objcopy seems to only copy these three, but I'm not yet certain why only these three
	// (as these aren't the only three that have PROGBITS set).

	let text = elf
		.get_section_by_name(".text")
		.ok_or_else(|| GoblinError::Malformed("ELF .text section not found".into()))?
		.get_data(elf_data)?;

	// Allow .ARM.exidx to not exist.
	let arm_exidx = elf
		.get_section_by_name(".ARM.exidx")
		.and_then(|v| v.get_data(elf_data).ok());
	let arm_exidx_len = arm_exidx.map(|sect| sect.len()).unwrap_or(0);

	let data = elf
		.get_section_by_name(".data")
		.ok_or_else(|| GoblinError::Malformed("ELF .data section not found".into()))?
		.get_data(elf_data)?;

	let mut extracted = Vec::with_capacity(text.len() + arm_exidx_len + data.len());

	extracted.extend_from_slice(text);
	if let Some(arm_exidx) = arm_exidx {
		extracted.extend_from_slice(arm_exidx);
	}

	extracted.extend_from_slice(data);

	Ok(extracted)
}