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Support duplicate ELF sections when linking
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@koute
koute committed Feb 2, 2024
1 parent 7022b3e commit da598af
Showing 1 changed file with 32 additions and 39 deletions.
71 changes: 32 additions & 39 deletions crates/polkavm-linker/src/program_from_elf.rs
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
use polkavm_common::abi::{GuestMemoryConfig, VM_ADDR_USER_MEMORY, VM_CODE_ADDRESS_ALIGNMENT, VM_MAX_PAGE_SIZE, VM_PAGE_SIZE};
use polkavm_common::elf::INSTRUCTION_ECALLI;
use polkavm_common::program::{self, FrameKind, Instruction, LineProgramOp, ProgramBlob, ProgramSymbol};
use polkavm_common::utils::align_to_next_page_u64;
use polkavm_common::utils::{align_to_next_page_u32, align_to_next_page_u64};
use polkavm_common::varint;
use polkavm_common::writer::{ProgramBlobBuilder, Writer};

Expand Down Expand Up @@ -972,7 +972,7 @@ fn extract_memory_config(
sections_ro_data: &[SectionIndex],
sections_rw_data: &[SectionIndex],
sections_bss: &[SectionIndex],
section_min_stack_size: Option<SectionIndex>,
sections_min_stack_size: &[SectionIndex],
base_address_for_section: &mut HashMap<SectionIndex, u64>,
) -> Result<MemoryConfig, ProgramFromElfError> {
let mut memory_end = u64::from(VM_ADDR_USER_MEMORY);
Expand Down Expand Up @@ -1115,24 +1115,22 @@ fn extract_memory_config(
bss_size = align_to_next_page_u64(u64::from(VM_PAGE_SIZE), bss_size)
.ok_or(ProgramFromElfError::other("out of range size for BSS sections"))?;

let stack_size = if let Some(section_index) = section_min_stack_size {
let mut stack_size = VM_PAGE_SIZE;
for &section_index in sections_min_stack_size {
let section = elf.section_by_index(section_index);
let data = section.data();
if data.len() % 4 != 0 {
return Err(ProgramFromElfError::other(format!("section '{}' has invalid size", section.name())));
}

let mut stack_size = 0;
for xs in data.chunks_exact(4) {
let value = u32::from_le_bytes([xs[0], xs[1], xs[2], xs[3]]);
stack_size = core::cmp::max(stack_size, value);
}
}

align_to_next_page_u64(u64::from(VM_PAGE_SIZE), u64::from(stack_size))
.ok_or(ProgramFromElfError::other("out of range size for the stack"))?
} else {
u64::from(VM_PAGE_SIZE)
};
let stack_size =
align_to_next_page_u32(VM_PAGE_SIZE, stack_size).ok_or(ProgramFromElfError::other("out of range size for the stack"))?;

log::trace!("Configured stack size: 0x{stack_size:x}");

Expand All @@ -1144,7 +1142,7 @@ fn extract_memory_config(
assert!(ro_data_size_physical <= ro_data_size);
assert!(rw_data_size_physical <= rw_data_size);

let config = match GuestMemoryConfig::new(ro_data_size, rw_data_size, bss_size, stack_size) {
let config = match GuestMemoryConfig::new(ro_data_size, rw_data_size, bss_size, u64::from(stack_size)) {
Ok(config) => config,
Err(error) => {
return Err(ProgramFromElfError::other(error));
Expand All @@ -1159,7 +1157,7 @@ fn extract_memory_config(
ro_data,
rw_data,
bss_size: bss_size as u32,
stack_size: stack_size as u32,
stack_size,
};

Ok(memory_config)
Expand Down Expand Up @@ -6356,9 +6354,9 @@ pub fn program_from_elf(config: Config, data: &[u8]) -> Result<ProgramBlob, Prog
let mut sections_rw_data = Vec::new();
let mut sections_bss = Vec::new();
let mut sections_code = Vec::new();
let mut section_metadata = None;
let mut section_exports = None;
let mut section_min_stack_size = None;
let mut sections_metadata = Vec::new();
let mut sections_exports = Vec::new();
let mut sections_min_stack_size = Vec::new();
let mut sections_other = Vec::new();

for section in elf.sections() {
Expand Down Expand Up @@ -6402,20 +6400,11 @@ pub fn program_from_elf(config: Config, data: &[u8]) -> Result<ProgramBlob, Prog

sections_code.push(section.index());
} else if name == ".polkavm_metadata" {
if section_metadata.is_some() {
return Err(ProgramFromElfError::other("found duplicate '.polkavm_metadata' section"));
}
section_metadata = Some(section.index());
sections_metadata.push(section.index());
} else if name == ".polkavm_exports" {
if section_exports.is_some() {
return Err(ProgramFromElfError::other("found duplicate '.polkavm_exports' section"));
}
section_exports = Some(section.index());
sections_exports.push(section.index());
} else if name == ".polkavm_min_stack_size" {
if section_min_stack_size.is_some() {
return Err(ProgramFromElfError::other("found duplicate '.polkavm_min_stack_size' section"));
}
section_min_stack_size = Some(section.index());
sections_min_stack_size.push(section.index());
} else if name == ".eh_frame" || name == ".got" {
continue;
} else if section.is_allocated() {
Expand All @@ -6439,8 +6428,8 @@ pub fn program_from_elf(config: Config, data: &[u8]) -> Result<ProgramBlob, Prog
.chain(sections_rw_data.iter())
.chain(sections_bss.iter()) // Shouldn't need relocations, but just in case.
.chain(sections_other.iter())
.chain(section_metadata.iter())
.chain(section_exports.iter())
.chain(sections_metadata.iter())
.chain(sections_exports.iter())
.copied();

let mut relocations = BTreeMap::new();
Expand All @@ -6455,12 +6444,14 @@ pub fn program_from_elf(config: Config, data: &[u8]) -> Result<ProgramBlob, Prog
harvest_code_relocations(&elf, section, &mut instruction_overrides, &mut relocations)?;
}

let exports = if let Some(section_index) = section_exports {
let section = elf.section_by_index(section_index);
extract_exports(&elf, &relocations, section)?
} else {
Default::default()
};
let exports = sections_exports
.iter()
.map(|&section_index| {
let section = elf.section_by_index(section_index);
extract_exports(&elf, &relocations, section)
})
.collect::<Result<Vec<_>, _>>()?;
let exports: Vec<_> = exports.into_iter().flatten().collect();

let mut instructions = Vec::new();
let mut imports = Vec::new();
Expand Down Expand Up @@ -6501,10 +6492,12 @@ pub fn program_from_elf(config: Config, data: &[u8]) -> Result<ProgramBlob, Prog
.iter()
.all(|(source, _)| source.offset_range.start < source.offset_range.end));

relocations.retain(|relocation_target, _| {
let section_index = relocation_target.section_index;
!(section_metadata.map_or(false, |index| index == section_index) || section_exports.map_or(false, |index| index == section_index))
});
{
let strip_relocations_for_sections: HashSet<_> =
sections_metadata.iter().copied().chain(sections_exports.iter().copied()).collect();

relocations.retain(|relocation_target, _| !strip_relocations_for_sections.contains(&relocation_target.section_index));
}

let data_sections_set: HashSet<SectionIndex> = sections_ro_data
.iter()
Expand Down Expand Up @@ -6671,7 +6664,7 @@ pub fn program_from_elf(config: Config, data: &[u8]) -> Result<ProgramBlob, Prog
&sections_ro_data,
&sections_rw_data,
&sections_bss,
section_min_stack_size,
&sections_min_stack_size,
&mut base_address_for_section,
)?;

Expand Down

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