Commit Graph

4 Commits

Author SHA1 Message Date
Fangrui Song 71c4b8dfe1 [crt][test] Add -no-pie to avoid wacky linking with crt1.o if (musl || CLANG_DEFAULT_PIE_ON_LINUX)
This works with glibc crt1.o (its crt1.o is essentially Scrt1.o plus (if static
PIE is supported for the arch) _dl_relocate_static_pie) but looks wacky.

musl crt1.o is not built with an explicit -fno-pic/-fpie/-fpic. If it was built
with a non-default-pie GCC/Clang, the linker might complain about absolute
relocations referencing _init/_fini for the -pie link:

```
ld: error: relocation R_X86_64_32 cannot be used against symbol '_fini'; recompile with -fPIC
>>> defined in obj/crt/crt1.o
>>> referenced by crt1.c
>>>               obj/crt/crt1.o:(_start_c)
```
2022-02-26 04:41:49 +00:00
Fangrui Song c520863abb [crt][test] Make ctor_dtor.c robust if DT_INIT/DT_FINI is disabled
New ports in glibc typically don't define ELF_INITFINI, so
DT_INIT/DT_FINI support is disabled.
(rhel ppc64le likely patches their glibc this way as well.)
musl can disable DT_INIT/DT_FINI via -DNO_LEGACY_INITFINI.

So we cannot guarantee ctor()/dtor() will be printed.
2021-08-12 09:31:31 -07:00
Sterling Augustine 38c356176b Fix include guard and properly order __deregister_frame_info.
Summary:
This patch fixes two problems with the crtbegin.c as written:

1. In do_init, register_frame_info is not guarded by a #define, but in
do_fini, deregister_frame_info is guarded by #ifndef
CRT_HAS_INITFINI_ARRAY. Thus when CRT_HAS_INITFINI_ARRAY is not
defined, frames are registered but then never deregistered.

The frame registry mechanism builds a linked-list from the .so's
static variable do_init.object, and when the .so is unloaded, this
memory becomes invalid and should be deregistered.

Further, libgcc's crtbegin treats the frame registry as independent
from the initfini array mechanism.

This patch fixes this by adding a new #define,
"EH_USE_FRAME_INFO_REGISTRY", which is set by the cmake option
COMPILER_RT_CRT_USE_EH_FRAME_REGISTRY Currently, do_init calls
register_frame_info, and then calls the binary's constructors. This
allows constructors to safely use libunwind. However, do_fini calls
deregister_frame_info and then calls the binary's destructors. This
prevents destructors from safely using libunwind.

This patch also switches that ordering, so that destructors can safely
use libunwind. As it happens, this is a fairly common scenario for
thread sanitizer.
2019-11-12 14:54:41 -08:00
Petr Hosek 999bb5ac27 Reland "[compiler-rt] Simple crtbegin.o and crtend.o implementation"
Clang relies on existence of certain symbols that are normally
provided by crtbegin.o/crtend.o. However, LLVM does not currently
provide implementation of these files, instead relying on either
libgcc or implementations provided as part of the system.

This change provides an initial implementation of crtbegin.o/crtend.o
that can be used on system that don't provide crtbegin.o/crtend.o as
part of their C library.

Differential Revision: https://reviews.llvm.org/D28791

llvm-svn: 359591
2019-04-30 18:13:22 +00:00