llvm/ompiler-rt sanitizer 不支持 aarch64 ilp32：asan_interceptors_vfork.S 与 aarch64 ilp32 不兼容答案

【问题标题】：llvm/ompiler-rt sanitizer not support aarch64 ilp32: asan_interceptors_vfork.S incompatible with aarch64 ilp32llvm/ompiler-rt sanitizer 不支持 aarch64 ilp32：asan_interceptors_vfork.S 与 aarch64 ilp32 不兼容
【发布时间】：2021-01-20 09:29:03
【问题描述】：

我正在从 compiler-rt(https://github.com/llvm/llvm-project) 构建 libasan.so，在使用 https://patches.linaro.org/patch/129368/ 修补源后，所有 cpp 都可以正确构建。但是我被 ASM (asan/asan_interceptors_vfork.S) 阻止了，在 aarch64 中，这指的是 https://github.com/llvm/llvm-project/blob/main/compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors_vfork_aarch64.inc.S。

错误信息：

aarch64_be-linux-gnu/bin/ld: warning: alignment 4 of symbol `_ZN14__interception10real_vforkE' in CMakeFiles/asan.dir/asan/asan_interceptors.cpp.o is smaller than 8 in CMakeFiles/asan.dir/asan/asan_interceptors_vfork.S.o
aarch64_be-linux-gnu/7.3.0/../../../../aarch64_be-linux-gnu/bin/ld: CMakeFiles/asan.dir/asan/asan_interceptors_vfork.S.o: relocation R_AARCH64_P32_ADR_PREL_PG_HI21 against symbol `_ZN14__interception10real_vforkE' which may bind externally can not be used when making a shared object; recompile with -fPIC
CMakeFiles/asan.dir/asan/asan_interceptors_vfork.S.o: in function `__interceptor_vfork':
llvm-project/compiler-rt/lib/./sanitizer_common/sanitizer_common_interceptors_vfork_aarch64.inc.S:19:(.text+0x10): dangerous relocation: unsupported relocation
llvm-project/compiler-rt/lib/./sanitizer_common/sanitizer_common_interceptors_vfork_aarch64.inc.S:20:(.text+0x14): relocation truncated to fit: R_AARCH64_P32_LDST64_ABS_LO12_NC against symbol `__interception::real_vfork' defined in .bss section in CMakeFiles/asan.dir/asan/asan_interceptors.cpp.o
aarch64_be-linux-gnu/7.3.0/../../../../aarch64_be-linux-gnu/bin/ld: /cdev/ASAN/llvm-project/compiler-rt/lib/./sanitizer_common/sanitizer_common_interceptors_vfork_aarch64.inc.S:20: warning: one possible cause of this error is that the symbol is being referenced in the indicated code as if it had a larger alignment than was declared where it was defined
collect2: error: ld returned 1 exit status
lib/CMakeFiles/asan.dir/build.make:1770: recipe for target 'lib/libasan.so' failed

我猜背后的原因是 asan_interceptors_vfork.S 是默认的 ILP64 格式？

ps：我在构建 asan_interceptors_vfork.S.o 时确实有 -fPIC

【问题讨论】：

标签： arm64 sanitizer

【解决方案1】：

需要修改compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors_vfork_aarch64.inc.S：

ldr     x0, [x0, :lo12:_ZN14__interception10real_vforkE]

应该是

ldr     w0, [x0, :lo12:_ZN14__interception10real_vforkE]

在构建 ILP32 代码时。

【讨论】：

非常感谢。我将 x0 更改为 w0 并且 R_AARCH64_P32_LDST64_ABS_LO12_NC 错误消失了。还是relocation R_AARCH64_P32_ADR_PREL_PG_HI21 against symbol _ZN14__interception10real_vforkE' 可能会在外部绑定，在制作共享对象时不能使用；使用 -fPIC` 重新编译。我不确定如何使用 fPIC 重新编译没有 C/CPP 源的 ASM。
7 .comm _ZN14__interception10real_vforkE,4,4 19 adrp x0, :got:_ZN14__interception10real_vforkE 20 ldr w0, [x0, :got_lo12:_ZN14__interception10real_vforkE] 解决了这个问题。