Messages in this thread | | | From | Ard Biesheuvel <> | Date | Mon, 19 Feb 2024 11:57:04 +0100 | Subject | Re: [PATCH v2] arm64: jump_label: use constraints "Si" instead of "i" |
| |
On Mon, 19 Feb 2024 at 11:56, Ard Biesheuvel <ardb@kernel.org> wrote: > > On Mon, 19 Feb 2024 at 11:03, Geert Uytterhoeven <geert@linux-m68k.org> wrote: > > > > Hi Fangrui, > > > > On Tue, Feb 6, 2024 at 8:46 AM Fangrui Song <maskray@google.com> wrote: > > > The generic constraint "i" seems to be copied from x86 or arm (and with > > > a redundant generic operand modifier "c"). It works with -fno-PIE but > > > not with -fPIE/-fPIC in GCC's aarch64 port. > > > > Thanks for your patch, which is now commit f9daab0ad01cf9d1 ("arm64: > > jump_label: use constraints "Si" instead of "i"") in v6.8-rc5. > > > > > The machine constraint "S", which denotes a symbol or label reference > > > with a constant offset, supports PIC and has been available in GCC since > > > 2012 and in Clang since 7.0. However, Clang before 19 does not support > > > "S" on a symbol with a constant offset [1] (e.g. > > > `static_key_false(&nf_hooks_needed[pf][hook])` in > > > include/linux/netfilter.h), so we use "i" as a fallback. > > > > https://gcc.gnu.org/releases.html says gcc-5 was released in 2015, > > i.e. after 2012 ... > > > > > Suggested-by: Ard Biesheuvel <ardb@kernel.org> > > > Signed-off-by: Fangrui Song <maskray@google.com> > > > Link: https://github.com/llvm/llvm-project/pull/80255 [1] > > > > > > --- > > > Changes from > > > arm64: jump_label: use constraint "S" instead of "i" (https://lore.kernel.org/all/20240131065322.1126831-1-maskray@google.com/) > > > > > > * Use "Si" as Ard suggested to support Clang<19 > > > * Make branch a separate operand > > > > > > Changes from v1: > > > > > > * Use asmSymbolicName for readability > > > > But it still fails on gcc-5: > > > > arch/arm64/include/asm/jump_label.h:25:2: error: invalid 'asm': > > invalid operand > > asm goto( > > ^ > > > > http://kisskb.ellerman.id.au/kisskb/buildresult/15129281/ > > > > How odd. godbolt.org has 5.4 and it seems perfectly happy with it. > > https://godbolt.org/z/szzG3s59K
Wrong link
https://godbolt.org/z/GTnf3vPaT
| |