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[bpf] add relocation support 

. there should be no runtime relocation inside the bpf function.
  . relocation supported here mostly for debugging.
  . a test case is added.

Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
llvm-svn: 302055
This commit is contained in:
Alexei Starovoitov 2017-05-03 17:30:56 +00:00
parent 21ebbf74ac
commit 4198f2a702
4 changed files with 82 additions and 0 deletions
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32
llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp
View File

@ -819,6 +819,34 @@ void RuntimeDyldELF::resolveSystemZRelocation(const SectionEntry &Section,
}
}
void RuntimeDyldELF::resolveBPFRelocation(const SectionEntry &Section,
uint64_t Offset, uint64_t Value,
uint32_t Type, int64_t Addend) {
bool isBE = Arch == Triple::bpfeb;
switch (Type) {
default:
llvm_unreachable("Relocation type not implemented yet!");
break;
case ELF::R_BPF_NONE:
break;
case ELF::R_BPF_64_64: {
write(isBE, Section.getAddressWithOffset(Offset), Value + Addend);
DEBUG(dbgs() << "Writing " << format("%p", (Value + Addend)) << " at "
<< format("%p\n", Section.getAddressWithOffset(Offset)));
break;
}
case ELF::R_BPF_64_32: {
Value += Addend;
assert(Value <= UINT32_MAX);
write(isBE, Section.getAddressWithOffset(Offset), static_cast<uint32_t>(Value));
DEBUG(dbgs() << "Writing " << format("%p", Value) << " at "
<< format("%p\n", Section.getAddressWithOffset(Offset)));
break;
}
}
}
// The target location for the relocation is described by RE.SectionID and
// RE.Offset. RE.SectionID can be used to find the SectionEntry. Each
// SectionEntry has three members describing its location.
@ -879,6 +907,10 @@ void RuntimeDyldELF::resolveRelocation(const SectionEntry &Section,
case Triple::systemz:
resolveSystemZRelocation(Section, Offset, Value, Type, Addend);
break;
case Triple::bpfel:
case Triple::bpfeb:
resolveBPFRelocation(Section, Offset, Value, Type, Addend);
break;
default:
llvm_unreachable("Unsupported CPU type!");
}

3
llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.h
View File

@ -58,6 +58,9 @@ class RuntimeDyldELF : public RuntimeDyldImpl {
void resolveSystemZRelocation(const SectionEntry &Section, uint64_t Offset,
uint64_t Value, uint32_t Type, int64_t Addend);
void resolveBPFRelocation(const SectionEntry &Section, uint64_t Offset,
uint64_t Value, uint32_t Type, int64_t Addend);
unsigned getMaxStubSize() override {
if (Arch == Triple::aarch64 || Arch == Triple::aarch64_be)
return 20; // movz; movk; movk; movk; br

4
llvm/lib/MC/MCObjectFileInfo.cpp
View File

@ -286,6 +286,10 @@ void MCObjectFileInfo::initELFMCObjectFileInfo(const Triple &T) {
((CMModel == CodeModel::Large) ? dwarf::DW_EH_PE_sdata8
: dwarf::DW_EH_PE_sdata4);
break;
case Triple::bpfel:
case Triple::bpfeb:
FDECFIEncoding = dwarf::DW_EH_PE_sdata8;
break;
default:
FDECFIEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
break;

43
llvm/test/CodeGen/BPF/reloc.ll Normal file
View File

@ -0,0 +1,43 @@
; RUN: llc -march=bpfel -filetype=obj < %s | llvm-objdump -r - | FileCheck --check-prefix=CHECK-RELOC %s
%struct.bpf_context = type { i64, i64, i64, i64, i64, i64, i64 }
%struct.sk_buff = type { i64, i64, i64, i64, i64, i64, i64 }
%struct.net_device = type { i64, i64, i64, i64, i64, i64, i64 }
@bpf_prog1.devname = private unnamed_addr constant [3 x i8] c"lo\00", align 1
@bpf_prog1.fmt = private unnamed_addr constant [15 x i8] c"skb %x dev %x\0A\00", align 1
; Function Attrs: norecurse
define i32 @bpf_prog1(%struct.bpf_context* nocapture %ctx) #0 section "events/net/netif_receive_skb" {
%devname = alloca [3 x i8], align 1
%fmt = alloca [15 x i8], align 1
%1 = getelementptr inbounds [3 x i8], [3 x i8]* %devname, i64 0, i64 0
call void @llvm.memcpy.p0i8.p0i8.i64(i8* %1, i8* getelementptr inbounds ([3 x i8], [3 x i8]* @bpf_prog1.devname, i64 0, i64 0), i64 3, i32 1, i1 false)
%2 = getelementptr inbounds %struct.bpf_context, %struct.bpf_context* %ctx, i64 0, i32 0
%3 = load i64, i64* %2, align 8
%4 = inttoptr i64 %3 to %struct.sk_buff*
%5 = getelementptr inbounds %struct.sk_buff, %struct.sk_buff* %4, i64 0, i32 2
%6 = bitcast i64* %5 to i8*
%7 = call i8* inttoptr (i64 4 to i8* (i8*)*)(i8* %6) #1
%8 = call i32 inttoptr (i64 9 to i32 (i8*, i8*, i32)*)(i8* %7, i8* %1, i32 2) #1
%9 = icmp eq i32 %8, 0
br i1 %9, label %10, label %13
; <label>:10 ; preds = %0
%11 = getelementptr inbounds [15 x i8], [15 x i8]* %fmt, i64 0, i64 0
call void @llvm.memcpy.p0i8.p0i8.i64(i8* %11, i8* getelementptr inbounds ([15 x i8], [15 x i8]* @bpf_prog1.fmt, i64 0, i64 0), i64 15, i32 1, i1 false)
%12 = call i32 (i8*, i32, ...) inttoptr (i64 11 to i32 (i8*, i32, ...)*)(i8* %11, i32 15, %struct.sk_buff* %4, i8* %7) #1
br label %13
; <label>:13 ; preds = %10, %0
ret i32 0
; CHECK-RELOC: file format ELF64-BPF
; CHECK-RELOC: RELOCATION RECORDS FOR [.rel.eh_frame]:
; CHECK-RELOC: R_BPF_64_64 events/net/netif_receive_skb
}
; Function Attrs: nounwind
declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture, i8* nocapture, i64, i32, i1) #1
attributes #0 = { norecurse }