On Mon, Apr 15, 2019 at 5:13 AM Ananyev, Konstantin <konstantin.ananyev@xxxxxxxxx> wrote: > > Hi Alexei, > I posted the question below on llvm-dev mailing list, but there is no answer so far. > As you seems the author of BPF_PSEUDO_CALL in LLVM (and linux kernel) thought might > be you know the answer? > I looked through the patches, but didn't spot anything myself. > Thanks > Konstantin > > -----Original Message----- > From: llvm-dev [mailto:llvm-dev-bounces@xxxxxxxxxxxxxx] On Behalf Of Ananyev, Konstantin via llvm-dev > Sent: Wednesday, April 10, 2019 7:37 PM > To: llvm-dev@xxxxxxxxxxxxxx > Subject: [llvm-dev] BPF_PSEUDO_CALL question > > > Hi everyone, > with clang 6.0 and onwards, for the following code: > $ cat t6.c > > #include <stdint.h> > > extern int ffx1(const void *p); > > uint64_t entry(const void *p) > { > return ffx1(p); > } > > clang -O2 -target bpfel -c t6.c > generates for the call BPF_PSEUDO_CALL instruction: > entry: > 0: 85 10 00 00 ff ff ff ff call -1 > 1: 67 00 00 00 20 00 00 00 r0 <<= 32 > 2: c7 00 00 00 20 00 00 00 r0 s>>= 32 > 3: 95 00 00 00 00 00 00 00 exit > > Is there any way to force clang to generate proper BPF_CALL instruction, > i.e: 85 00 00 00 ff ff ff ff (as it did in older versions)? older version of llvm generated broken code. there are only two call flavors: - call imm -> calling particular kernel helper where imm==helper_id - call pseudo +-off -> call another bpf function there is no arbitrary call support yet.
