Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

Avoid increased alignment of TLS segments on Fuchsia #53180

Closed
wants to merge 1 commit into from
Closed

Avoid increased alignment of TLS segments on Fuchsia #53180

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
10 changes: 8 additions & 2 deletions src/librustc_codegen_llvm/consts.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -345,7 +345,7 @@ pub fn codegen_static<'a, 'tcx>(
if attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL) {
llvm::set_thread_local_mode(g, cx.tls_model);

// Do not allow LLVM to change the alignment of a TLS on macOS.
// Do not allow LLVM to change the alignment of a TLS on macOS and Fuchsia.
//
// By default a global's alignment can be freely increased.
// This allows LLVM to generate more performant instructions
Expand All @@ -355,6 +355,10 @@ pub fn codegen_static<'a, 'tcx>(
// respect any alignment given on the TLS (radar 24221680).
// This will violate the alignment assumption, and causing segfault at runtime.
//
// Fuchsia's libc currently does not support greater than 16-byte alignment
// of TLS segments, so this hack is also enabled temporarily for Fuchsia targets
// until libc is fixed.
//
// This bug is very easy to trigger. In `println!` and `panic!`,
// the `LOCAL_STDOUT`/`LOCAL_STDERR` handles are stored in a TLS,
// which the values would be `mem::replace`d on initialization.
Expand All @@ -374,7 +378,9 @@ pub fn codegen_static<'a, 'tcx>(
// will use load-unaligned instructions instead, and thus avoiding the crash.
//
// We could remove this hack whenever we decide to drop macOS 10.10 support.
if cx.tcx.sess.target.target.options.is_like_osx {
if cx.tcx.sess.target.target.options.is_like_osx ||
(cx.tcx.sess.target.target.target_os == "fuchsia")
{
let sect_name = if alloc.bytes.iter().all(|b| *b == 0) {
CStr::from_bytes_with_nul_unchecked(b"__DATA,__thread_bss\0")
} else {
Expand Down