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Rollup merge of rust-lang#73564 - petrochenkov:ehdr, r=Amanieu
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linker: Create GNU_EH_FRAME header by default when producing ELFs

Do it in a centralized way in `link.rs` instead of individual target specs.

The opt-out is `-Clink-arg=(-Wl,)--no-eh-frame-hdr` if necessary.

Fixes rust-lang#73451
cc rust-lang#73483
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Manishearth authored Jun 30, 2020
2 parents d8f38e9 + 79a42e3 commit 9f330e4
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Showing 7 changed files with 19 additions and 14 deletions.
3 changes: 3 additions & 0 deletions src/librustc_codegen_ssa/back/link.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1597,6 +1597,9 @@ fn linker_with_args<'a, B: ArchiveBuilder<'a>>(
cmd.arg(format!("--dynamic-linker={}ld.so.1", prefix));
}

// NO-OPT-OUT, OBJECT-FILES-NO, AUDIT-ORDER
cmd.add_eh_frame_header();

// NO-OPT-OUT, OBJECT-FILES-NO
if crt_objects_fallback {
cmd.no_crt_objects();
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14 changes: 14 additions & 0 deletions src/librustc_codegen_ssa/back/linker.rs
Original file line number Diff line number Diff line change
Expand Up @@ -129,6 +129,7 @@ pub trait Linker {
fn group_start(&mut self);
fn group_end(&mut self);
fn linker_plugin_lto(&mut self);
fn add_eh_frame_header(&mut self) {}
fn finalize(&mut self);
}

Expand Down Expand Up @@ -615,6 +616,19 @@ impl<'a> Linker for GccLinker<'a> {
}
}
}

// Add the `GNU_EH_FRAME` program header which is required to locate unwinding information.
// Some versions of `gcc` add it implicitly, some (e.g. `musl-gcc`) don't,
// so we just always add it.
fn add_eh_frame_header(&mut self) {
// The condition here is "uses ELF" basically.
if !self.sess.target.target.options.is_like_osx
&& !self.sess.target.target.options.is_like_windows
&& self.sess.target.target.target_os != "uefi"
{
self.linker_arg("--eh-frame-hdr");
}
}
}

pub struct MsvcLinker<'a> {
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1 change: 0 additions & 1 deletion src/librustc_target/spec/cloudabi_base.rs
Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,6 @@ pub fn opts() -> TargetOptions {
vec![
"-Wl,-Bstatic".to_string(),
"-Wl,--no-dynamic-linker".to_string(),
"-Wl,--eh-frame-hdr".to_string(),
"-Wl,--gc-sections".to_string(),
],
);
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1 change: 0 additions & 1 deletion src/librustc_target/spec/fuchsia_base.rs
Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,6 @@ pub fn opts() -> TargetOptions {
LinkerFlavor::Lld(LldFlavor::Ld),
vec![
"--build-id".to_string(),
"--eh-frame-hdr".to_string(),
"--hash-style=gnu".to_string(),
"-z".to_string(),
"max-page-size=4096".to_string(),
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8 changes: 1 addition & 7 deletions src/librustc_target/spec/linux_musl_base.rs
Original file line number Diff line number Diff line change
@@ -1,15 +1,9 @@
use crate::spec::crt_objects::{self, CrtObjectsFallback};
use crate::spec::{LinkerFlavor, TargetOptions};
use crate::spec::TargetOptions;

pub fn opts() -> TargetOptions {
let mut base = super::linux_base::opts();

// At least when this was tested, the linker would not add the
// `GNU_EH_FRAME` program header to executables generated, which is required
// when unwinding to locate the unwinding information. I'm not sure why this
// argument is *not* necessary for normal builds, but it can't hurt!
base.pre_link_args.get_mut(&LinkerFlavor::Gcc).unwrap().push("-Wl,--eh-frame-hdr".to_string());

base.pre_link_objects_fallback = crt_objects::pre_musl_fallback();
base.post_link_objects_fallback = crt_objects::post_musl_fallback();
base.crt_objects_fallback = Some(CrtObjectsFallback::Musl);
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5 changes: 1 addition & 4 deletions src/librustc_target/spec/mipsel_sony_psp.rs
Original file line number Diff line number Diff line change
Expand Up @@ -6,10 +6,7 @@ const LINKER_SCRIPT: &str = include_str!("./mipsel_sony_psp_linker_script.ld");

pub fn target() -> TargetResult {
let mut pre_link_args = LinkArgs::new();
pre_link_args.insert(
LinkerFlavor::Lld(LldFlavor::Ld),
vec!["--eh-frame-hdr".to_string(), "--emit-relocs".to_string()],
);
pre_link_args.insert(LinkerFlavor::Lld(LldFlavor::Ld), vec!["--emit-relocs".to_string()]);

Ok(Target {
llvm_target: "mipsel-sony-psp".to_string(),
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1 change: 0 additions & 1 deletion src/librustc_target/spec/x86_64_fortanix_unknown_sgx.rs
Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,6 @@ use super::{LinkerFlavor, LldFlavor, PanicStrategy, Target, TargetOptions};
pub fn target() -> Result<Target, String> {
const PRE_LINK_ARGS: &[&str] = &[
"--as-needed",
"--eh-frame-hdr",
"-z",
"noexecstack",
"-e",
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