https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85492
--- Comment #10 from Andrew Waterman <andrew at sifive dot com> --- Thanks for the suggestion. Let's go with the CFI-directive approach. On Sat, Apr 28, 2018 at 5:45 AM, aurelien at aurel32 dot net <gcc-bugzi...@gcc.gnu.org> wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85492 > > --- Comment #7 from Aurelien Jarno <aurelien at aurel32 dot net> --- > (In reply to Jim Wilson from comment #3) > Thanks a lot Jim for finding out the issue without using gdb, that was quite a > challenge. > > (In reply to Jim Wilson from comment #6) >> I suggest you handle the glibc patch. > > Should I just close this bug and open a new one on the glibc side? > >> Note that you can probably also fix this by adding unwind direcives to >> _start to say that the return address is in x0. This would avoid the minor >> code size increase, but takes a little more effort to figure out how to add >> the right unwind directives to assembly code to make this work. I haven't >> tried that. > > I think this should be done with the cfi_undefined directive, like in the > patch > below: > > --- a/sysdeps/riscv/start.S > +++ b/sysdeps/riscv/start.S > @@ -43,6 +43,8 @@ > __libc_start_main wants this in a5. */ > > ENTRY (ENTRY_POINT) > + /* Mark ra as undefined in order to stop unwinding here! */ > + cfi_undefined (ra) > call .Lload_gp > mv a5, a0 /* rtld_fini. */ > /* main may be in a shared library. */
