androm3da

Bug Report: memd + dealloc_return packet causes callee-saved register corruption

Summary

The Hexagon compiler/assembler (clang 21.1.8) generates packets containing both a memd register-pair load and a dealloc_return instruction. When executed under QEMU system emulation, this packet corrupts callee-saved registers: the upper byte of a restored kernel pointer is zeroed (e.g., 0xc0ca5960 becomes 0x00ca5960), leading to a page fault and kernel panic.

androm3da

Hexagon Backend Release Report: LLVM 21.x

Timeframe: January 29, 2025 - July 15, 2025 Report Generated: January 20, 2026

Summary

During the LLVM 21.x development cycle, the Hexagon backend saw 27 merged pull requests and 10 issues reported.

Merged Pull Requests by Category

androm3da

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androm3da

#!/bin/bash

set -euo pipefail

echo creating init file
echo <<EOF > input.S
.section .text
EOF
echo '' > keep_syms.txt
for i in $(seq 0 100000)

androm3da

FROM ubuntu:16.04
VOLUME ['/tmp/']
RUN apt-get update && apt-get install -y --force-yes build-essential subversion chrpath wget file python python-virtualenv cmake ninja-build tar tcl && \
    cd /tmp && \
    wget --quiet https://raw.githubusercontent.com/llvm/llvm-project/master/llvm/utils/release/test-release.sh && \
    wget --quiet https://releases.llvm.org/8.0.0/clang+llvm-8.0.0-x86_64-linux-gnu-ubuntu-14.04.tar.xz && \
    tar xf clang+llvm-8.0.0-x86_64-linux-gnu-ubuntu-14.04.tar.xz && \
    chmod +x test-release.sh && \
    /usr/bin/env CXX=/tmp/clang+llvm-8.0.0-x86_64-linux-gnu-ubuntu-14.04/bin/clang++ \

androm3da

+ mkdir obj_target_v60_83latest_test-suite
+ cd obj_target_v60_83latest_test-suite
+ cmake -GNinja -DCMAKE_C_COMPILER=hexagon-linux-clang -DCMAKE_CXX_COMPILER=hexagon-linux-clang++ -C/local/mnt/workspace/testing/test-suite/cmake/caches/O0.cmake -DTEST_SUITE_EXTRA_C_FLAGS=-mv60 -DTEST_SUITE_EXTRA_CXX_FLAGS=-mv60 -DTEST_SUITE_EXTRA_EXE_LINKER_FLAGS=-mv60 -DARCH:STRING=Hexagon -DTEST_SUITE_CXX_ABI_LIBNAME:STRING=libc++abi -DBENCHMARK_USE_LIBCXX:BOOL=ON -DTEST_SUITE_REMOTE_CLIENT:STRING=ssh -DTEST_SUITE_REMOTE_HOST:STRING=aus-dragon820-05 -DTEST_SUITE_LIT_FLAGS:STRING=-vj4 -DFP_TOLERANCE:STRING=1.5 -DFP_ABSTOLERANCE:STRING=1.5 /local/mnt/workspace/testing/test-suite
loading initial cache file /local/mnt/workspace/testing/test-suite/cmake/caches/O0.cmake
-- The C compiler identification is Clang 7.0.0
-- The CXX compiler identification is Clang 7.0.0
-- Check for working C compiler using: Ninja
-- Check for working C compiler using: Ninja -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info -

androm3da

#!/bin/bash -x

set -euo pipefail

test_suite=$(readlink -f ${1-../test-suite/})
PATH=/prj/dsp/qdsp6/release/internal/HEXAGON/branch-8.4lnx/latest/Tools/bin:$PATH
qemu=~bcain/src/hexagon-clang/qemu.sh
Q6_ARCH=v65
opt=O0
flavor=qemu_${Q6_ARCH}_84latest_${opt}

androm3da

#!/bin/bash -x

# Run the llvm test-suite on target (v60)

set -euo pipefail

Q6_ARCH=v60
test_suite=$(readlink -f ${1})
PATH=/prj/dsp/qdsp6/release/internal/HEXAGON/branch-8.3lnx/latest/Tools/bin:$PATH
flavor=target_${Q6_ARCH}_83latest

androm3da

+ stage=1
+ ./x.py build --stage 1 -vvvv --config ../hexagon-linux-83.toml src/liblibc
running: /local/mnt/workspace/rust/rust/build/x86_64-unknown-linux-gnu/stage0/bin/cargo build --manifest-path /local/mnt/workspace/rust/rust/src/bootstrap/Cargo.toml --verbose --verbose --verbose
       Fresh unicode-xid v0.1.0
       Fresh cc v1.0.35
       Fresh ordermap v0.3.5
       Fresh unicode-width v0.1.5
       Fresh cfg-if v0.1.8
       Fresh itoa v0.4.4
       Fresh fixedbitset v0.1.9

androm3da

+ stage=1
+ ./x.py build --stage 1 -vvvv --config ../hexagon-linux-83.toml src/liblibc
running: /local/mnt/workspace/rust/rust/build/x86_64-unknown-linux-gnu/stage0/bin/cargo build --manifest-path /local/mnt/workspace/rust/rust/src/bootstrap/Cargo.toml --verbose --verbose --verbose
       Fresh unicode-xid v0.1.0
       Fresh cc v1.0.35
       Fresh ordermap v0.3.5
       Fresh unicode-width v0.1.5
       Fresh cfg-if v0.1.8
       Fresh itoa v0.4.4
       Fresh fixedbitset v0.1.9