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Change how wasm DWARF is inserted into artifacts (#5358)

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This commit fixes a bug with components by changing how DWARF
information from a wasm binary is copied over to the final compiled
artifact. Note that this is not the Wasmtime-generated DWARF but rather
the native wasm DWARF itself used in backtraces.

Previously the wasm dwarf was inserted into sections `.*.wasm` where `*`
was `debug_info`, `debug_str`, etc -- one per `gimli::SectionId` as
found in the original wasm module. This does not work with components,
however, where modules did not correctly separate their debug
information into separate sections or otherwise disambiguate. The fix in
this commit is to instead smash all the debug information together into
one large section and store offsets into that giant section. This is
similar to the `name`-section scraping or the trap metadata section
where one section contains all the data for all the modules in a component.

This simplifies the object file parsing by only looking for one section
name and doesn't add all that much complexity to serializing and looking
up dwarf information as well.
This commit is contained in:
Alex Crichton
2022-12-06 14:29:13 -06:00
committed by GitHub
parent 51b6a0436c
commit 08d44e3746
3 changed files with 65 additions and 68 deletions
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57
crates/jit/src/code_memory.rs
View File

@@ -32,10 +32,7 @@ pub struct CodeMemory {
address_map_data: Range<usize>,
func_name_data: Range<usize>,
info_data: Range<usize>,
/// Map of dwarf sections indexed by `gimli::SectionId` which points to the
/// range within `code_memory`'s mmap as to the contents of the section.
dwarf_sections: Vec<Range<usize>>,
dwarf: Range<usize>,
}
impl Drop for CodeMemory {
@@ -60,8 +57,6 @@ impl CodeMemory {
/// The returned `CodeMemory` manages the internal `MmapVec` and the
/// `publish` method is used to actually make the memory executable.
pub fn new(mmap: MmapVec) -> Result<Self> {
use gimli::SectionId::*;
let obj = File::parse(&mmap[..])
.with_context(|| "failed to parse internal compilation artifact")?;
@@ -73,7 +68,7 @@ impl CodeMemory {
let mut address_map_data = 0..0;
let mut func_name_data = 0..0;
let mut info_data = 0..0;
let mut dwarf_sections = Vec::new();
let mut dwarf = 0..0;
for section in obj.sections() {
let data = section.data()?;
let name = section.name()?;
@@ -90,14 +85,6 @@ impl CodeMemory {
}
}
let mut gimli = |id: gimli::SectionId| {
let idx = id as usize;
if dwarf_sections.len() <= idx {
dwarf_sections.resize(idx + 1, 0..0);
}
dwarf_sections[idx] = range.clone();
};
match name {
obj::ELF_WASM_BTI => match data.len() {
1 => enable_branch_protection = Some(data[0] != 0),
@@ -118,31 +105,7 @@ impl CodeMemory {
obj::ELF_WASMTIME_TRAPS => trap_data = range,
obj::ELF_NAME_DATA => func_name_data = range,
obj::ELF_WASMTIME_INFO => info_data = range,
// Register dwarf sections into the `dwarf_sections`
// array which is indexed by `gimli::SectionId`
".debug_abbrev.wasm" => gimli(DebugAbbrev),
".debug_addr.wasm" => gimli(DebugAddr),
".debug_aranges.wasm" => gimli(DebugAranges),
".debug_frame.wasm" => gimli(DebugFrame),
".eh_frame.wasm" => gimli(EhFrame),
".eh_frame_hdr.wasm" => gimli(EhFrameHdr),
".debug_info.wasm" => gimli(DebugInfo),
".debug_line.wasm" => gimli(DebugLine),
".debug_line_str.wasm" => gimli(DebugLineStr),
".debug_loc.wasm" => gimli(DebugLoc),
".debug_loc_lists.wasm" => gimli(DebugLocLists),
".debug_macinfo.wasm" => gimli(DebugMacinfo),
".debug_macro.wasm" => gimli(DebugMacro),
".debug_pub_names.wasm" => gimli(DebugPubNames),
".debug_pub_types.wasm" => gimli(DebugPubTypes),
".debug_ranges.wasm" => gimli(DebugRanges),
".debug_rng_lists.wasm" => gimli(DebugRngLists),
".debug_str.wasm" => gimli(DebugStr),
".debug_str_offsets.wasm" => gimli(DebugStrOffsets),
".debug_types.wasm" => gimli(DebugTypes),
".debug_cu_index.wasm" => gimli(DebugCuIndex),
".debug_tu_index.wasm" => gimli(DebugTuIndex),
obj::ELF_WASMTIME_DWARF => dwarf = range,
_ => log::debug!("ignoring section {name}"),
}
@@ -158,7 +121,7 @@ impl CodeMemory {
trap_data,
address_map_data,
func_name_data,
dwarf_sections,
dwarf,
info_data,
wasm_data,
})
@@ -175,15 +138,9 @@ impl CodeMemory {
&self.mmap[self.text.clone()]
}
/// Returns the data in the corresponding dwarf section, or an empty slice
/// if the section wasn't present.
pub fn dwarf_section(&self, section: gimli::SectionId) -> &[u8] {
let range = self
.dwarf_sections
.get(section as usize)
.cloned()
.unwrap_or(0..0);
&self.mmap[range]
/// Returns the contents of the `ELF_WASMTIME_DWARF` section.
pub fn dwarf(&self) -> &[u8] {
&self.mmap[self.dwarf.clone()]
}
/// Returns the data in the `ELF_NAME_DATA` section.