From 1d0a1ee04d616d1e90d4f91ae4a1170fe6358dc7 Mon Sep 17 00:00:00 2001 From: Yonghong Song Date: Tue, 18 May 2021 08:35:59 -0700 Subject: [PATCH] BPF: Add more relocation kinds Currently, BPF only contains three relocations: R_BPF_NONE for no relocation R_BPF_64_64 for LD_imm64 and normal 64-bit data relocation R_BPF_64_32 for call insn and normal 32-bit data relocation Also .BTF and .BTF.ext sections contain symbols in allocated program and data sections. These two sections reserved 32bit space to hold the offset relative to the symbol's section. When LLVM JIT is used, the LLVM ExecutionEngine RuntimeDyld may attempt to resolve relocations for .BTF and .BTF.ext, which we want to prevent. So we used R_BPF_NONE for such relocations. This all works fine until when we try to do linking of multiple objects. . R_BPF_64_64 handling of LD_imm64 vs. normal 64-bit data is different, so lld target->relocate() needs more context to do a correct job. . The same for R_BPF_64_32. More context is needed for lld target->relocate() to differentiate call insn vs. normal 32-bit data relocation. . Since relocations in .BTF and .BTF.ext are set to R_BPF_NONE, they will not be relocated properly when multiple .BTF/.BTF.ext sections are merged by lld. This patch intends to address this issue by adding additional relocation kinds: R_BPF_64_ABS64 for normal 64-bit data relocation R_BPF_64_ABS32 for normal 32-bit data relocation R_BPF_64_NODYLD32 for .BTF and .BTF.ext style relocations. The old R_BPF_64_{64,32} semantics: R_BPF_64_64 for LD_imm64 relocation R_BPF_64_32 for call insn relocation The existing R_BPF_64_64/R_BPF_64_32 mapping to numeric values is maintained. They are the most common use cases for bpf programs and we want to maintain backward compatibility as much as possible. ExecutionEngine RuntimeDyld BPF relocations are adjusted as well. R_BPF_64_{ABS64,ABS32} relocations will be resolved properly and other relocations will be ignored. Two tests are added for RuntimeDyld. Not handling R_BPF_64_NODYLD32 in RuntimeDyldELF.cpp will result in "Relocation type not implemented yet!" fatal error. FK_SecRel_4 usages in BPFAsmBackend.cpp and BPFELFObjectWriter.cpp are removed as they are not triggered in BPF backend. BPF backend used FK_SecRel_8 for LD_imm64 instruction operands. Differential Revision: https://reviews.llvm.org/D102712 --- include/llvm/BinaryFormat/ELFRelocs/BPF.def | 3 + .../RuntimeDyld/RuntimeDyldELF.cpp | 7 +- lib/Target/BPF/MCTargetDesc/BPFAsmBackend.cpp | 2 +- .../BPF/MCTargetDesc/BPFELFObjectWriter.cpp | 20 ++--- test/CodeGen/BPF/reloc-2.ll | 60 +++++++++++++++ test/CodeGen/BPF/reloc-3.ll | 25 ++++++ test/CodeGen/BPF/reloc-btf-2.ll | 4 +- test/CodeGen/BPF/reloc-btf.ll | 6 +- test/CodeGen/BPF/reloc.ll | 2 +- .../RuntimeDyld/BPF/abs64-relocation.s | 26 +++++++ .../RuntimeDyld/BPF/lit.local.cfg | 2 + .../RuntimeDyld/BPF/nodyld32-64-relocations.s | 77 +++++++++++++++++++ 12 files changed, 215 insertions(+), 19 deletions(-) create mode 100644 test/CodeGen/BPF/reloc-2.ll create mode 100644 test/CodeGen/BPF/reloc-3.ll create mode 100644 test/ExecutionEngine/RuntimeDyld/BPF/abs64-relocation.s create mode 100644 test/ExecutionEngine/RuntimeDyld/BPF/lit.local.cfg create mode 100644 test/ExecutionEngine/RuntimeDyld/BPF/nodyld32-64-relocations.s diff --git a/include/llvm/BinaryFormat/ELFRelocs/BPF.def b/include/llvm/BinaryFormat/ELFRelocs/BPF.def index 5dd7f70b696..cc18a65d1fd 100644 --- a/include/llvm/BinaryFormat/ELFRelocs/BPF.def +++ b/include/llvm/BinaryFormat/ELFRelocs/BPF.def @@ -5,4 +5,7 @@ // No relocation ELF_RELOC(R_BPF_NONE, 0) ELF_RELOC(R_BPF_64_64, 1) +ELF_RELOC(R_BPF_64_ABS64, 2) +ELF_RELOC(R_BPF_64_ABS32, 3) +ELF_RELOC(R_BPF_64_NODYLD32, 4) ELF_RELOC(R_BPF_64_32, 10) diff --git a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp index 30c3856f77e..efe0b9cd61c 100644 --- a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp +++ b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp @@ -951,14 +951,17 @@ void RuntimeDyldELF::resolveBPFRelocation(const SectionEntry &Section, report_fatal_error("Relocation type not implemented yet!"); break; case ELF::R_BPF_NONE: + case ELF::R_BPF_64_64: + case ELF::R_BPF_64_32: + case ELF::R_BPF_64_NODYLD32: break; - case ELF::R_BPF_64_64: { + case ELF::R_BPF_64_ABS64: { write(isBE, Section.getAddressWithOffset(Offset), Value + Addend); LLVM_DEBUG(dbgs() << "Writing " << format("%p", (Value + Addend)) << " at " << format("%p\n", Section.getAddressWithOffset(Offset))); break; } - case ELF::R_BPF_64_32: { + case ELF::R_BPF_64_ABS32: { Value += Addend; assert(Value <= UINT32_MAX); write(isBE, Section.getAddressWithOffset(Offset), static_cast(Value)); diff --git a/lib/Target/BPF/MCTargetDesc/BPFAsmBackend.cpp b/lib/Target/BPF/MCTargetDesc/BPFAsmBackend.cpp index 29e9d5da083..6687dbe2536 100644 --- a/lib/Target/BPF/MCTargetDesc/BPFAsmBackend.cpp +++ b/lib/Target/BPF/MCTargetDesc/BPFAsmBackend.cpp @@ -63,7 +63,7 @@ void BPFAsmBackend::applyFixup(const MCAssembler &Asm, const MCFixup &Fixup, MutableArrayRef Data, uint64_t Value, bool IsResolved, const MCSubtargetInfo *STI) const { - if (Fixup.getKind() == FK_SecRel_4 || Fixup.getKind() == FK_SecRel_8) { + if (Fixup.getKind() == FK_SecRel_8) { // The Value is 0 for global variables, and the in-section offset // for static variables. Write to the immediate field of the inst. assert(Value <= UINT32_MAX); diff --git a/lib/Target/BPF/MCTargetDesc/BPFELFObjectWriter.cpp b/lib/Target/BPF/MCTargetDesc/BPFELFObjectWriter.cpp index ef4e324c3bd..7c0c23a86de 100644 --- a/lib/Target/BPF/MCTargetDesc/BPFELFObjectWriter.cpp +++ b/lib/Target/BPF/MCTargetDesc/BPFELFObjectWriter.cpp @@ -43,12 +43,13 @@ unsigned BPFELFObjectWriter::getRelocType(MCContext &Ctx, const MCValue &Target, default: llvm_unreachable("invalid fixup kind!"); case FK_SecRel_8: + // LD_imm64 instruction. return ELF::R_BPF_64_64; case FK_PCRel_4: - case FK_SecRel_4: + // CALL instruction. return ELF::R_BPF_64_32; case FK_Data_8: - return ELF::R_BPF_64_64; + return ELF::R_BPF_64_ABS64; case FK_Data_4: if (const MCSymbolRefExpr *A = Target.getSymA()) { const MCSymbol &Sym = A->getSymbol(); @@ -63,23 +64,22 @@ unsigned BPFELFObjectWriter::getRelocType(MCContext &Ctx, const MCValue &Target, if (Sym.isTemporary()) { // .BTF.ext generates FK_Data_4 relocations for // insn offset by creating temporary labels. - // The insn offset is within the code section and - // already been fulfilled by applyFixup(). No - // further relocation is needed. // The reloc symbol should be in text section. + // Use a different relocation to instruct ExecutionEngine + // RuntimeDyld not to do relocation for it, yet still to + // allow lld to do proper adjustment when merging sections. if ((Flags & ELF::SHF_ALLOC) && (Flags & ELF::SHF_EXECINSTR)) - return ELF::R_BPF_NONE; + return ELF::R_BPF_64_NODYLD32; } else { // .BTF generates FK_Data_4 relocations for variable - // offset in DataSec kind. Similar to the above .BTF.ext - // insn offset, no further relocation is needed. + // offset in DataSec kind. // The reloc symbol should be in data section. if ((Flags & ELF::SHF_ALLOC) && (Flags & ELF::SHF_WRITE)) - return ELF::R_BPF_NONE; + return ELF::R_BPF_64_NODYLD32; } } } - return ELF::R_BPF_64_32; + return ELF::R_BPF_64_ABS32; } } diff --git a/test/CodeGen/BPF/reloc-2.ll b/test/CodeGen/BPF/reloc-2.ll new file mode 100644 index 00000000000..301ac3e164d --- /dev/null +++ b/test/CodeGen/BPF/reloc-2.ll @@ -0,0 +1,60 @@ +; RUN: llc -march=bpfel -filetype=obj -o %t.el < %s +; RUN: llvm-objdump -r %t.el | FileCheck --check-prefix=RELOC %s +; RUN: llvm-objdump -d --no-show-raw-insn %t.el | FileCheck --check-prefix=DUMP %s +; RUN: llc -march=bpfeb -filetype=obj -o %t.eb < %s +; RUN: llvm-objdump -r %t.eb | FileCheck --check-prefix=RELOC %s +; RUN: llvm-objdump -d --no-show-raw-insn %t.eb | FileCheck --check-prefix=DUMP %s + +; source code: +; static __attribute__((noinline)) __attribute__((section("sec1"))) +; int add(int a, int b) { +; return a + b; +; } +; static __attribute__((noinline)) +; int sub(int a, int b) { +; return a - b; +; } +; int test(int a, int b) { +; return add(a, b) + sub(a, b); +; } +; compilation flag: +; clang -target bpf -O2 -emit-llvm -S test.c + +define dso_local i32 @test(i32 %a, i32 %b) local_unnamed_addr #0 { +entry: + %call = tail call fastcc i32 @add(i32 %a, i32 %b) + %call1 = tail call fastcc i32 @sub(i32 %a, i32 %b) + %add = add nsw i32 %call1, %call + ret i32 %add +} + +define internal fastcc i32 @add(i32 %a, i32 %b) unnamed_addr #1 section "sec1" { +entry: + %add = add nsw i32 %b, %a + ret i32 %add +} + +; Function Attrs: nofree noinline norecurse nosync nounwind readnone willreturn mustprogress +define internal fastcc i32 @sub(i32 %a, i32 %b) unnamed_addr #1 { +entry: + %sub = sub nsw i32 %a, %b + ret i32 %sub +} + +; DUMP: .text: +; DUMP-EMPTY: +; DUMP-NEXT: +; DUMP-NEXT: r[[#]] = r[[#]] +; DUMP-NEXT: r[[#]] = r[[#]] +; DUMP-NEXT: call -1 + +; DUMP: sec1: +; DUMP-EMPTY: +; DUMP-NEXT: + +; RELOC: RELOCATION RECORDS FOR [.text]: +; RELOC: R_BPF_64_32 sec1 +; RELOC-NOT: R_BPF_64_32 + +attributes #0 = { nofree norecurse nosync nounwind readnone willreturn mustprogress "frame-pointer"="all" "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" } +attributes #1 = { nofree noinline norecurse nosync nounwind readnone willreturn mustprogress "frame-pointer"="all" "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" } diff --git a/test/CodeGen/BPF/reloc-3.ll b/test/CodeGen/BPF/reloc-3.ll new file mode 100644 index 00000000000..0acf2d93856 --- /dev/null +++ b/test/CodeGen/BPF/reloc-3.ll @@ -0,0 +1,25 @@ +; RUN: llc -march=bpfel -filetype=obj -o %t.el < %s +; RUN: llvm-readelf -r %t.el | FileCheck %s +; RUN: llc -march=bpfeb -filetype=obj -o %t.eb < %s +; RUN: llvm-readelf -r %t.eb | FileCheck %s + +; source code: +; int g() { return 0; } +; struct t { void *p; } gbl = { g }; +; compilation flag: +; clang -target bpf -O2 -emit-llvm -S test.c + +%struct.t = type { i8* } + +@gbl = dso_local local_unnamed_addr global %struct.t { i8* bitcast (i32 ()* @g to i8*) }, align 8 + +; CHECK: '.rel.data' +; CHECK: 0000000000000000 0000000200000002 R_BPF_64_ABS64 0000000000000000 g + +; Function Attrs: nofree norecurse nosync nounwind readnone willreturn mustprogress +define dso_local i32 @g() #0 { +entry: + ret i32 0 +} + +attributes #0 = { nofree norecurse nosync nounwind readnone willreturn mustprogress "frame-pointer"="all" "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" } diff --git a/test/CodeGen/BPF/reloc-btf-2.ll b/test/CodeGen/BPF/reloc-btf-2.ll index 68f00081d7d..7a287ae2ce5 100644 --- a/test/CodeGen/BPF/reloc-btf-2.ll +++ b/test/CodeGen/BPF/reloc-btf-2.ll @@ -23,8 +23,8 @@ define dso_local i32 @test() local_unnamed_addr #0 !dbg !14 { ; CHECK-RELOC: file format elf64-bpf ; CHECK-RELOC: RELOCATION RECORDS FOR [.BTF]: -; CHECK-RELOC: R_BPF_NONE .bss -; CHECK-RELOC: R_BPF_NONE g +; CHECK-RELOC: R_BPF_64_NODYLD32 .bss +; CHECK-RELOC: R_BPF_64_NODYLD32 g ; CHECK-RELOC: RELOCATION RECORDS FOR [.BTF.ext]: attributes #0 = { norecurse nounwind "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "min-legal-vector-width"="0" "frame-pointer"="all" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" } diff --git a/test/CodeGen/BPF/reloc-btf.ll b/test/CodeGen/BPF/reloc-btf.ll index c6f34fbde46..aa929257e03 100644 --- a/test/CodeGen/BPF/reloc-btf.ll +++ b/test/CodeGen/BPF/reloc-btf.ll @@ -8,10 +8,10 @@ entry: ; CHECK-RELOC: file format elf64-bpf ; CHECK-RELOC: RELOCATION RECORDS FOR [.debug_info]: -; CHECK-RELOC: R_BPF_64_32 .debug_abbrev -; CHECK-RELOC: R_BPF_64_64 .text +; CHECK-RELOC: R_BPF_64_ABS32 .debug_abbrev +; CHECK-RELOC: R_BPF_64_ABS64 .text ; CHECK-RELOC: RELOCATION RECORDS FOR [.BTF.ext]: -; CHECK-RELOC: R_BPF_NONE .text +; CHECK-RELOC: R_BPF_64_NODYLD32 .text attributes #0 = { norecurse nounwind readnone "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "min-legal-vector-width"="0" "frame-pointer"="all" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" } diff --git a/test/CodeGen/BPF/reloc.ll b/test/CodeGen/BPF/reloc.ll index e00dfdb5d2f..123de485174 100644 --- a/test/CodeGen/BPF/reloc.ll +++ b/test/CodeGen/BPF/reloc.ll @@ -34,7 +34,7 @@ define i32 @bpf_prog1(%struct.bpf_context* nocapture %ctx) #0 section "events/ne ; CHECK-RELOC: file format elf64-bpf ; CHECK-RELOC: RELOCATION RECORDS FOR [.eh_frame]: -; CHECK-RELOC: R_BPF_64_64 events/net/netif_receive_skb +; CHECK-RELOC: R_BPF_64_ABS64 events/net/netif_receive_skb } ; Function Attrs: nounwind diff --git a/test/ExecutionEngine/RuntimeDyld/BPF/abs64-relocation.s b/test/ExecutionEngine/RuntimeDyld/BPF/abs64-relocation.s new file mode 100644 index 00000000000..6e7d1c16e35 --- /dev/null +++ b/test/ExecutionEngine/RuntimeDyld/BPF/abs64-relocation.s @@ -0,0 +1,26 @@ +# RUN: rm -rf %t && mkdir -p %t +# RUN: llvm-mc -triple=bpfel -filetype=obj -o %t/test_reloc_abs64.o %s +# RUN: llvm-rtdyld -triple=bpfel -verify -check=%s %t/test_reloc_abs64.o + +# test R_BPF_64_ABS64 which should have relocation resolved properly. + + .text + .file "t1.c" + .globl g # -- Begin function g + .p2align 3 + .type g,@function +g: # @g + r0 = 0 + exit +.Lfunc_end0: + .size g, .Lfunc_end0-g + # -- End function + .type gbl,@object # @gbl + .data + .globl gbl + .p2align 3 +gbl: + .quad g + .size gbl, 8 + +# rtdyld-check: *{8}gbl = section_addr(test_reloc_abs64.o, .text) diff --git a/test/ExecutionEngine/RuntimeDyld/BPF/lit.local.cfg b/test/ExecutionEngine/RuntimeDyld/BPF/lit.local.cfg new file mode 100644 index 00000000000..a4ab2624af6 --- /dev/null +++ b/test/ExecutionEngine/RuntimeDyld/BPF/lit.local.cfg @@ -0,0 +1,2 @@ +if not 'BPF' in config.root.targets: + config.unsupported = True diff --git a/test/ExecutionEngine/RuntimeDyld/BPF/nodyld32-64-relocations.s b/test/ExecutionEngine/RuntimeDyld/BPF/nodyld32-64-relocations.s new file mode 100644 index 00000000000..fbb140725ea --- /dev/null +++ b/test/ExecutionEngine/RuntimeDyld/BPF/nodyld32-64-relocations.s @@ -0,0 +1,77 @@ +# RUN: llvm-mc -triple=bpfel -filetype=obj -o %t %s +# RUN: llvm-rtdyld -triple=bpfel -verify -check=%s %t + +# test R_BPF_64_64 and R_BPF_64_NODYLD32 relocations, both should be ignored. + + .globl _main + .p2align 3 + .type _main,@function +_main: # @_main + r1 = a ll + +# rtdyld-check: decode_operand(_main, 1)[31:0] = 0x0 + + r0 = *(u32 *)(r1 + 0) + exit +.Lfunc_end0: + .size _main, .Lfunc_end0-_main + # -- End function + + .type a,@object # @a + .section .bss,"aw",@nobits + .globl a + .p2align 2 +a: + .long 0 # 0x0 + .size a, 4 + +# rtdyld-check: *{4}a = 0 + + .section .BTF,"",@progbits + .short 60319 # 0xeb9f + .byte 1 + .byte 0 + .long 24 + .long 0 + .long 80 + .long 80 + .long 87 + .long 0 # BTF_KIND_FUNC_PROTO(id = 1) + .long 218103808 # 0xd000000 + .long 2 + .long 1 # BTF_KIND_INT(id = 2) + .long 16777216 # 0x1000000 + .long 4 + .long 16777248 # 0x1000020 + .long 5 # BTF_KIND_FUNC(id = 3) + .long 201326593 # 0xc000001 + .long 1 + .long 80 # BTF_KIND_VAR(id = 4) + .long 234881024 # 0xe000000 + .long 2 + .long 1 + .long 82 # BTF_KIND_DATASEC(id = 5) + .long 251658241 # 0xf000001 + .long 0 + .long 4 +btf_a: + .long a + +# rtdyld-check: *{4}btf_a = 0 + + .long 4 + .byte 0 # string offset=0 + .ascii "int" # string offset=1 + .byte 0 + .ascii "_main" # string offset=5 + .byte 0 + .ascii ".text" # string offset=11 + .byte 0 + .ascii "/home/yhs/work/tests/llvm/rtdyld/t.c" # string offset=17 + .byte 0 + .ascii "int _main() { return a; }" # string offset=54 + .byte 0 + .byte 97 # string offset=80 + .byte 0 + .ascii ".bss" # string offset=82 + .byte 0