> -----Original Message----- > From: Alexei Starovoitov [mailto:alexei.starovoitov@xxxxxxxxx] > Sent: Tuesday, April 16, 2019 2:01 AM > To: Ananyev, Konstantin <konstantin.ananyev@xxxxxxxxx>; bpf <bpf@xxxxxxxxxxxxxxx> > Subject: Re: FW: BPF_PSEUDO_CALL question > > 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 Ok but in the example above, is it possible tell to the llvm that ffx1() is actually a kernel helper with id==X? > - call pseudo +-off -> call another bpf function > there is no arbitrary call support yet.
