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Disable libunwind cross-architecture unwinding #141375

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Disable libunwind cross-architecture unwinding #141375

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@kraj kraj commented May 22, 2025

Building with _LIBUNWIND_IS_NATIVE_ONLY disables code for cross-architecture unwinding It also enables some additional code that handles PAC-specific unwind info it helps compiling with the -mbranch-protection=pac or -mbranch-protection=standard flags

This fixes build with clang/musl on aarch64

@kraj
Disable libunwind cross-architecture unwinding
ecc0a33 
Building with _LIBUNWIND_IS_NATIVE_ONLY disables code for cross-architecture unwinding
It also enables some additional code that handles PAC-specific unwind info
it helps compiling with the -mbranch-protection=pac or -mbranch-protection=standard flags

This fixes build with clang/musl on aarch64

Signed-off-by: Khem Raj <raj.khem@gmail.com>
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rustbot commented May 22, 2025

r? @Mark-Simulacrum

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@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-bootstrap Relevant to the bootstrap subteam: Rust's build system (x.py and src/bootstrap) labels May 22, 2025
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rustbot commented May 22, 2025

This PR changes how LLVM is built. Consider updating src/bootstrap/download-ci-llvm-stamp.

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kraj commented May 22, 2025

This is the error that happens when compiling rust for aarch64/musl using clang compiler with -mbranch-protection=standard turned on.

cargo:warning=/mnt/b/yoe/master/sources/poky/build/tmp/work/cortexa57-poky-linux-musl/rust/1.85.1/rustc-1.85.1-src/src/llvm-project/libunwind/src/UnwindLevel1.c:313:9: error: invalid input constraint 'D' in asm
cargo:warning=  313 |         __unw_phase2_resume(cursor, framesWalked);
cargo:warning=      |         ^
cargo:warning=/mnt/b/yoe/master/sources/poky/build/tmp/work/cortexa57-poky-linux-musl/rust/1.85.1/rustc-1.85.1-src/src/llvm-project/libunwind/src/UnwindLevel1.c:62:42: note: expanded from macro '__unw_phase2_resume'
cargo:warning=   62 |                      "jmp *%%edx\n\t" :: "D"(cetRegContext),                   \
cargo:warning=      |                                          ^
cargo:warning=/mnt/b/yoe/master/sources/poky/build/tmp/work/cortexa57-poky-linux-musl/rust/1.85.1/rustc-1.85.1-src/src/llvm-project/libunwind/src/UnwindLevel1.c:415:9: error: invalid input constraint 'D' in asm
cargo:warning=  415 |         __unw_phase2_resume(cursor, framesWalked);
cargo:warning=      |         ^
cargo:warning=/mnt/b/yoe/master/sources/poky/build/tmp/work/cortexa57-poky-linux-musl/rust/1.85.1/rustc-1.85.1-src/src/llvm-project/libunwind/src/UnwindLevel1.c:62:42: note: expanded from macro '__unw_phase2_resume'
cargo:warning=   62 |                      "jmp *%%edx\n\t" :: "D"(cetRegContext),                   \
cargo:warning=      |                                          ^
cargo:warning=2 errors generated.


error occurred: Command "/mnt/b/yoe/master/sources/poky/build/tmp/work/cortexa57-poky-linux-musl/rust/1.85.1/wrapper/target-rust-cc" "-I" "/mnt/b/yoe/master/sources/poky/build/tmp/work/cortexa57-poky-linux-musl/rust/1.85.1/rustc-1.85.1-src/src/llvm-project/libunwind/include" "-O2" "-g" "-ffile-prefix-map=/mnt/b/yoe/master/sources/poky/build/tmp/work/cortexa57-poky-linux-musl/rust/1.85.1/rustc-1.85.1-src=/usr/src/debug/rust/1.85.1" "-ffile-prefix-map=/mnt/b/yoe/master/sources/poky/build/tmp/work/cortexa57-poky-linux-musl/rust/1.85.1/rustc-1.85.1-src=/usr/src/debug/rust/1.85.1" "-ffile-prefix-map=/mnt/b/yoe/master/sources/poky/build/tmp/work/cortexa57-poky-linux-musl/rust/1.85.1/recipe-sysroot=" "-ffile-prefix-map=/mnt/b/yoe/master/sources/poky/build/tmp/work/cortexa57-poky-linux-musl/rust/1.85.1/recipe-sysroot-native=" "-pipe" "-fstrict-aliasing" "-funwind-tables" "-fvisibility=hidden" "-D_LIBUNWIND_DISABLE_VISIBILITY_ANNOTATIONS" "-o" "/mnt/b/yoe/master/sources/poky/build/tmp/work/cortexa57-poky-linux-musl/rust/1.85.1/rustc-1.85.1-src/build/aarch64-poky-linux-musl/native/libunwind/d440502555900257-UnwindLevel1.o" "-c" "/mnt/b/yoe/master/sources/poky/build/tmp/work/cortexa57-poky-linux-musl/rust/1.85.1/rustc-1.85.1-src/src/llvm-project/libunwind/src/UnwindLevel1.c" with args target-rust-cc did not execute successfully (status code exit status: 1).

/mnt/b/yoe/master/sources/poky/build/tmp/work/cortexa57-poky-linux-musl/rust/1.85.1/wrapper/target-rust-cc

is

#!/usr/bin/env python3
import os, sys
orig_binary = "aarch64-poky-linux-musl-clang  -mcpu=cortex-a57+crc -mbranch-protection=standard  --dyld-prefix=/usr -fstack-protector-strong  -O2 -D_FORTIFY_SOURCE=2 -Wformat -Wformat-security -Werror=format-security --sysroot=/mnt/b/yoe/master/sources/poky/build/tmp/work/cortexa57-poky-linux-musl/rust/1.85.1/recipe-sysroot -Wl,-O1 -Wl,--hash-style=gnu -Wl,--as-needed  -ffile-prefix-map=/mnt/b/yoe/master/sources/poky/build/tmp/work/cortexa57-poky-linux-musl/rust/1.85.1/rustc-1.85.1-src=/usr/src/debug/rust/1.85.1  -ffile-prefix-map=/mnt/b/yoe/master/sources/poky/build/tmp/work/cortexa57-poky-linux-musl/rust/1.85.1/rustc-1.85.1-src=/usr/src/debug/rust/1.85.1  -ffile-prefix-map=/mnt/b/yoe/master/sources/poky/build/tmp/work/cortexa57-poky-linux-musl/rust/1.85.1/recipe-sysroot=  -ffile-prefix-map=/mnt/b/yoe/master/sources/poky/build/tmp/work/cortexa57-poky-linux-musl/rust/1.85.1/recipe-sysroot-native=  -Wl,-z,relro,-z,now"
extras = "-lssp_nonshared"

# Apply a required subset of CC crate compiler flags
# when we build a target recipe for a non-bare-metal target.
# https://github.com/rust-lang/cc-rs/blob/main/src/lib.rs#L1614
if "CRATE_CC_NO_DEFAULTS" in os.environ.keys() and         "TARGET" in os.environ.keys() and not "-none-" in os.environ["TARGET"]:
    orig_binary += " -ffunction-sections -fdata-sections -fPIC"

binary = orig_binary.split()[0]
args = orig_binary.split() + sys.argv[1:]
if extras:
    args.append(extras)
os.execvp(binary, args)

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kraj commented May 22, 2025

Gentoo has a similar bug report - https://bugs.gentoo.org/950171

bjorn3
bjorn3 reviewed May 23, 2025
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src/bootstrap/src/core/build_steps/llvm.rs
@@ -1454,6 +1454,9 @@ impl Step for Libunwind {
cfg.define("_LIBUNWIND_HIDE_SYMBOLS", "1");
cfg.define("_LIBUNWIND_IS_NATIVE_ONLY", "1");
}
if self.target.starts_with("aarch64") && self.target.contains("musl") {
cfg.define("_LIBUNWIND_IS_NATIVE_ONLY", "1");
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Maybe this should be enabled on all targets except fortanix?

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