| Message ID | 20210727141119.19812-1-pavo.banicevic@sartura.hr |
|---|---|
| Headers | show |
| Series | Address compilation of eBPF related software with clang compiler on arm architecture | expand |
On Tue, Jul 27, 2021 at 7:12 AM Pavo Banicevic <pavo.banicevic@sartura.hr> wrote: > > From: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org> > > The samples/bpf with clang -emit-llvm reuses linux headers to build > bpf samples, and this w/a only for samples (samples/bpf/Makefile > CLANG-bpf). > > It allows to build samples/bpf for arm bpf using clang. > In another way clang -emit-llvm generates errors like: > > CLANG-bpf samples/bpf/tc_l2_redirect_kern.o > <inline asm>:1:2: error: invalid register/token name > rev16 r3, r0 > > This decision is arguable, probably there is another way, but > it doesn't have impact on samples/bpf, so it's easier just ignore > it for clang, at least for now. NACK The way to fix these is to sort out the header includes, not turning off arbitrary things that are used by the actual kernel build for 32b ARM. > > Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org> > --- > arch/arm/include/asm/swab.h | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/arch/arm/include/asm/swab.h b/arch/arm/include/asm/swab.h > index c6051823048b..a9fd9cd33d5e 100644 > --- a/arch/arm/include/asm/swab.h > +++ b/arch/arm/include/asm/swab.h > @@ -25,8 +25,11 @@ static inline __attribute_const__ __u32 __arch_swahb32(__u32 x) > __asm__ ("rev16 %0, %1" : "=r" (x) : "r" (x)); > return x; > } > + > +#ifndef __clang__ > #define __arch_swahb32 __arch_swahb32 > #define __arch_swab16(x) ((__u16)__arch_swahb32(x)) > +#endif > > static inline __attribute_const__ __u32 __arch_swab32(__u32 x) > { > -- > 2.32.0 >
On Tue, Jul 27, 2021 at 10:53 AM Nick Desaulniers <ndesaulniers@google.com> wrote: > > On Tue, Jul 27, 2021 at 7:12 AM Pavo Banicevic > <pavo.banicevic@sartura.hr> wrote: > > > > From: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org> > > > > The samples/bpf with clang -emit-llvm reuses linux headers to build > > bpf samples, and this w/a only for samples (samples/bpf/Makefile > > CLANG-bpf). > > > > It allows to build samples/bpf for arm bpf using clang. > > In another way clang -emit-llvm generates errors like: > > > > CLANG-bpf samples/bpf/tc_l2_redirect_kern.o > > <inline asm>:1:2: error: invalid register/token name > > rev16 r3, r0 > > > > This decision is arguable, probably there is another way, but > > it doesn't have impact on samples/bpf, so it's easier just ignore > > it for clang, at least for now. > > NACK > > The way to fix these is to sort out the header includes, not turning > off arbitrary things that are used by the actual kernel build for 32b > ARM. Would it be too horrible to just get rid of `clang -emit-llvm` and use vmlinux.h (we don't need to do CO-RE, btw, just generate vmlinux.h from the matching kernel)? Kumar has already started moving in that direction in his recent patch set ([0]). Would that get rid of all these issues? [0] https://patchwork.kernel.org/project/netdevbpf/list/?series=519281&state=* > > > > > Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org> > > --- > > arch/arm/include/asm/swab.h | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/arch/arm/include/asm/swab.h b/arch/arm/include/asm/swab.h > > index c6051823048b..a9fd9cd33d5e 100644 > > --- a/arch/arm/include/asm/swab.h > > +++ b/arch/arm/include/asm/swab.h > > @@ -25,8 +25,11 @@ static inline __attribute_const__ __u32 __arch_swahb32(__u32 x) > > __asm__ ("rev16 %0, %1" : "=r" (x) : "r" (x)); > > return x; > > } > > + > > +#ifndef __clang__ > > #define __arch_swahb32 __arch_swahb32 > > #define __arch_swab16(x) ((__u16)__arch_swahb32(x)) > > +#endif > > > > static inline __attribute_const__ __u32 __arch_swab32(__u32 x) > > { > > -- > > 2.32.0 > > > > > -- > Thanks, > ~Nick Desaulniers
On Tue, Jul 27, 2021 at 04:11:19PM +0200, Pavo Banicevic wrote: > From: Matt Redfearn <matt.redfearn@mips.com> > > Commit bc27fb68aaad ("include/uapi/linux/byteorder, swab: force inlining > of some byteswap operations") added __always_inline to swab functions > and commit 283d75737837 ("uapi/linux/stddef.h: Provide __always_inline to > userspace headers") added a definition of __always_inline for use in > exported headers when the kernel's compiler.h is not available. > > However, since swab.h does not include stddef.h, if the header soup does > not indirectly include it, the definition of __always_inline is missing, > resulting in a compilation failure, which was observed compiling the > perf tool using exported headers containing this commit: > > In file included from /usr/include/linux/byteorder/little_endian.h:12:0, > from /usr/include/asm/byteorder.h:14, > from tools/include/uapi/linux/perf_event.h:20, > from perf.h:8, > from builtin-bench.c:18: > /usr/include/linux/swab.h:160:8: error: unknown type name `__always_inline' > static __always_inline __u16 __swab16p(const __u16 *p) > > Fix this by replacing the inclusion of linux/compiler.h with > linux/stddef.h to ensure that we pick up that definition if required, > without relying on it's indirect inclusion. compiler.h is then included > indirectly, via stddef.h. > > Fixes: 283d75737837 ("uapi/linux/stddef.h: Provide __always_inline to userspace headers") > > Signed-off-by: Matt Redfearn <matt.redfearn@mips.com> > --- I use this patch in order to fix __always_inline issue for kernels 5.12+, see https://lore.kernel.org/lkml/YPGXXt6Z3O1W0AYS@arkam/ . I believe this is the correct solution. Reviewed-by: Petr Vaněk <arkamar@atlas.cz>