On Thu, Feb 29, 2024 at 10:49:26AM -0500, Sasha Levin wrote: > From: Fangrui Song <maskray@xxxxxxxxxx> > > [ Upstream commit f9daab0ad01cf9d165dbbbf106ca4e61d06e7fe8 ] Please drop this; same story as wit the v6.7 backport: https://lore.kernel.org/lkml/ZeCpOPDi18OBEclz@FVFF77S0Q05N/ Mark. > 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. > > 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. > > Suggested-by: Ard Biesheuvel <ardb@xxxxxxxxxx> > Signed-off-by: Fangrui Song <maskray@xxxxxxxxxx> > Link: https://github.com/llvm/llvm-project/pull/80255 [1] > Acked-by: Mark Rutland <mark.rutland@xxxxxxx> > Link: https://lore.kernel.org/r/20240206074552.541154-1-maskray@xxxxxxxxxx > Signed-off-by: Will Deacon <will@xxxxxxxxxx> > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> > --- > arch/arm64/include/asm/jump_label.h | 12 ++++++++---- > 1 file changed, 8 insertions(+), 4 deletions(-) > > diff --git a/arch/arm64/include/asm/jump_label.h b/arch/arm64/include/asm/jump_label.h > index 48ddc0f45d228..b7716b215f91a 100644 > --- a/arch/arm64/include/asm/jump_label.h > +++ b/arch/arm64/include/asm/jump_label.h > @@ -15,6 +15,10 @@ > > #define JUMP_LABEL_NOP_SIZE AARCH64_INSN_SIZE > > +/* > + * Prefer the constraint "S" to support PIC with GCC. Clang before 19 does not > + * support "S" on a symbol with a constant offset, so we use "i" as a fallback. > + */ > static __always_inline bool arch_static_branch(struct static_key * const key, > const bool branch) > { > @@ -23,9 +27,9 @@ static __always_inline bool arch_static_branch(struct static_key * const key, > " .pushsection __jump_table, \"aw\" \n\t" > " .align 3 \n\t" > " .long 1b - ., %l[l_yes] - . \n\t" > - " .quad %c0 - . \n\t" > + " .quad (%[key] - .) + %[bit0] \n\t" > " .popsection \n\t" > - : : "i"(&((char *)key)[branch]) : : l_yes); > + : : [key]"Si"(key), [bit0]"i"(branch) : : l_yes); > > return false; > l_yes: > @@ -40,9 +44,9 @@ static __always_inline bool arch_static_branch_jump(struct static_key * const ke > " .pushsection __jump_table, \"aw\" \n\t" > " .align 3 \n\t" > " .long 1b - ., %l[l_yes] - . \n\t" > - " .quad %c0 - . \n\t" > + " .quad (%[key] - .) + %[bit0] \n\t" > " .popsection \n\t" > - : : "i"(&((char *)key)[branch]) : : l_yes); > + : : [key]"Si"(key), [bit0]"i"(branch) : : l_yes); > > return false; > l_yes: > -- > 2.43.0 >
