On Wed, Nov 8, 2023 at 5:26 PM Xi Ruoyao <xry111@xxxxxxxxxxx> wrote: > > On Wed, 2023-11-08 at 17:20 +0800, WANG Rui wrote: > > > then the linked binary triggers a SIGBUS. Ideally this should be > > > detected by the linker at link time, but currently the BFD linker > > > fails > > > to detect this error (FWIW this flaw is caused by a really nasty > > > method > > > for the medium code model implementation). So to me -fno-direct- > > > access- > > > external-data is the default. I also grepped for -fdirect-access- > > > external-data in the kernel building system but I've not found any > > > match. > > > > > > Are you using a different version of Clang, or maybe Clang has some > > > configuration-time option to make -fdirect-access-external-data the > > > default? > > > > The clang enables `direct-access-external-data` by default in PIC and > > disables it by default in no-PIC. This also applies to PIE. [1] > > Oh sh*t: > > xry111@nanmen2 ~ $ clang t1.c -O2 -fno-pie -no-pie > xry111@nanmen2 ~ $ ./a.out > Bus error (core dumped) > > I'll consider it a Clang bug then. That's it, no copy relocations. As far as I know, copying relocations has some issues and is not recommended by Fangrui. For modules, if distance is not a problem, `no-pic` and `direct-access-external-data` can be together because the code is writable. Does it seem reasonable to exist? > > -- > Xi Ruoyao <xry111@xxxxxxxxxxx> > School of Aerospace Science and Technology, Xidian University > -- WANG Rui
