Backtraces are often broken on aarch64 binaries

[wesleywiser]

This seems to happen the most for -Cpanic=abort programs.

fn main() {
    foo();
}

fn foo() {
    panic!("hello world");
}

$ rustc -Cpanic=abort -Copt-level=3 -Cdebuginfo=2 --target aarch64-unknown-linux-gnu -C linker=aarch64-linux-gnu-gcc test.rs
$ qemu-aarch64 -E RUST_BACKTRACE=full -L /usr/aarch64-linux-gnu/ target/aarch64-unknown-linux-gnu/release/panic_test_abort
thread 'main' panicked at src/main.rs:8:5:
hello world
stack backtrace:
   0:       0x5500033b68 - std::backtrace_rs::backtrace::libunwind::trace::hee9690ac22774636
                               at /rustc/07dca489ac2d933c78d3c5158e3f43beefeb02ce/library/std/src/../../backtrace/src/backtrace/libunwind.rs:104:5
   1:       0x5500033b68 - std::backtrace_rs::backtrace::trace_unsynchronized::ha30111b5438e6e61
                               at /rustc/07dca489ac2d933c78d3c5158e3f43beefeb02ce/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:       0x5500033b68 - std::sys_common::backtrace::_print_fmt::hc2516686a74b2a42
                               at /rustc/07dca489ac2d933c78d3c5158e3f43beefeb02ce/library/std/src/sys_common/backtrace.rs:68:5
   3:       0x5500033b68 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h8984c88846573cbb
                               at /rustc/07dca489ac2d933c78d3c5158e3f43beefeb02ce/library/std/src/sys_common/backtrace.rs:44:22
   4:       0x550004ecc0 - core::fmt::rt::Argument::fmt::h071bdaa21123c9ed
                               at /rustc/07dca489ac2d933c78d3c5158e3f43beefeb02ce/library/core/src/fmt/rt.rs:142:9
   5:       0x550004ecc0 - core::fmt::write::h3f4921a7ddfa57a8
                               at /rustc/07dca489ac2d933c78d3c5158e3f43beefeb02ce/library/core/src/fmt/mod.rs:1120:17
   6:       0x5500031cb0 - std::io::Write::write_fmt::h0923e211983fe028
                               at /rustc/07dca489ac2d933c78d3c5158e3f43beefeb02ce/library/std/src/io/mod.rs:1810:15
   7:       0x5500033994 - std::sys_common::backtrace::_print::h39d471a7e51d9dbd
                               at /rustc/07dca489ac2d933c78d3c5158e3f43beefeb02ce/library/std/src/sys_common/backtrace.rs:47:5
   8:       0x5500033994 - std::sys_common::backtrace::print::h6306cb106d0c42e1
                               at /rustc/07dca489ac2d933c78d3c5158e3f43beefeb02ce/library/std/src/sys_common/backtrace.rs:34:9
   9:       0x5500034ed0 - std::panicking::default_hook::{{closure}}::h2a94c4f92161a016
  10:       0x5500034c04 - std::panicking::default_hook::hd3c29c68b55e9f50
                               at /rustc/07dca489ac2d933c78d3c5158e3f43beefeb02ce/library/std/src/panicking.rs:292:9
  11:       0x5500035364 - std::panicking::rust_panic_with_hook::ha00bbb72a4f1b899
                               at /rustc/07dca489ac2d933c78d3c5158e3f43beefeb02ce/library/std/src/panicking.rs:779:13
  12:       0x55000351ec - std::panicking::begin_panic_handler::{{closure}}::had2c64361be4b07b
                               at /rustc/07dca489ac2d933c78d3c5158e3f43beefeb02ce/library/std/src/panicking.rs:649:13
  13:       0x5500034038 - std::sys_common::backtrace::__rust_end_short_backtrace::hf92a1e94dde0ed69
                               at /rustc/07dca489ac2d933c78d3c5158e3f43beefeb02ce/library/std/src/sys_common/backtrace.rs:171:18
  14:       0x5500034fb8 - rust_begin_unwind
                               at /rustc/07dca489ac2d933c78d3c5158e3f43beefeb02ce/library/std/src/panicking.rs:645:5
  15:       0x5500009434 - core::panicking::panic_fmt::h815b849997a1324d
                               at /rustc/07dca489ac2d933c78d3c5158e3f43beefeb02ce/library/core/src/panicking.rs:72:14
  16:       0x550000ad14 - panic_test_abort::foo::h9689b6dfc03df639
                               at /home/wesley/panic_test_abort/src/main.rs:8:5
  17:       0x550000ad14 - panic_test_abort::foo::h9689b6dfc03df639
                               at /home/wesley/panic_test_abort/src/main.rs:8:5
  18:       0x550000ad14 - panic_test_abort::foo::h9689b6dfc03df639
                               at /home/wesley/panic_test_abort/src/main.rs:8:5
...
(continues forever)

Tested on

• rustc 1.76.0 (07dca489a 2024-02-04)

[wesleywiser]

I've got a fix but need to investigate adding regression tests a bit more.