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Enable copy-on-write heap initialization by default (#3825)

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* Enable copy-on-write heap initialization by default

This commit enables the `Config::memfd` feature by default now that it's
been fuzzed for a few weeks on oss-fuzz, and will continue to be fuzzed
leading up to the next release of Wasmtime in early March. The
documentation of the `Config` option has been updated as well as adding
a CLI flag to disable the feature.

* Remove ubiquitous "memfd" terminology

Switch instead to forms of "memory image" or "cow" or some combination
thereof.

* Update new option names
This commit is contained in:
Alex Crichton
2022-02-22 17:12:18 -06:00
committed by GitHub
parent 593f8d96aa
commit bbd4a4a500
16 changed files with 294 additions and 275 deletions
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16
crates/runtime/build.rs
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@@ -11,17 +11,13 @@ fn main() {
.file("src/helpers.c")
.compile("wasmtime-helpers");
// Check to see if we are on Unix and the `memfd` feature is
// active. If so, enable the `memfd` rustc cfg so `#[cfg(memfd)]`
// will work.
//
// Note that while this is called memfd it only actually uses the `memfd`
// crate on Linux and on other Unix platforms this tries to reuse mmap'd
// `*.cwasm` files.
// Check to see if we are on Unix and the `memory-init-cow` feature is
// active. If so, enable the `memory_init_cow` rustc cfg so
// `#[cfg(memory_init_cow)]` will work.
let family = env::var("CARGO_CFG_TARGET_FAMILY").unwrap();
let is_memfd = env::var("CARGO_FEATURE_MEMFD").is_ok();
let memory_init_cow = env::var("CARGO_FEATURE_MEMORY_INIT_COW").is_ok();
let is_uffd = env::var("CARGO_FEATURE_UFFD").is_ok();
if &family == "unix" && is_memfd && !is_uffd {
println!("cargo:rustc-cfg=memfd");
if &family == "unix" && memory_init_cow && !is_uffd {
println!("cargo:rustc-cfg=memory_init_cow");
}
}