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d15f96fe4b
Extend llvm-objdump to show CO-RE relocations when `-r` option is
passed and object file has .BTF and .BTF.ext sections.
For example, the following C program:
#define __pai __attribute__((preserve_access_index))
struct foo { int i; int j;} __pai;
struct bar { struct foo f[7]; } __pai;
extern void sink(void *);
void root(struct bar *bar) {
sink(&bar[2].f[3].j);
}
Should lead to the following objdump output:
$ clang --target=bpf -O2 -g t.c -c -o - | \
llvm-objdump --no-addresses --no-show-raw-insn -dr -
...
r2 = 0x94
CO-RE <byte_off> [2] struct bar::[2].f[3].j (2:0:3:1)
r1 += r2
call -0x1
R_BPF_64_32 sink
exit
...
More examples could be found in unit tests, see BTFParserTest.cpp.
To achieve this:
- Move CO-RE relocation kinds definitions from BPFCORE.h to BTF.h.
- Extend BTF.h with types derived from BTF::CommonType, e.g.
BTF::IntType and BTF::StrutType, to allow dyn_cast() and access to
type additional data.
- Extend BTFParser to load BTF type and relocation data.
- Modify llvm-objdump.cpp to create instance of BTFParser when
disassembly of object file with BTF sections is processed and `-r`
flag is supplied.
Additional information about CO-RE is available at [1].
[1] https://docs.kernel.org/bpf/llvm_reloc.html
Depends on D149058
Differential Revision: https://reviews.llvm.org/D150079
72 lines
2.4 KiB
C++
72 lines
2.4 KiB
C++
//===- BTFContext.cpp ---------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// Implementation of the BTFContext interface, this is used by
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// llvm-objdump tool to print source code alongside disassembly.
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// In fact, currently it is a simple wrapper for BTFParser instance.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/DebugInfo/BTF/BTFContext.h"
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#define DEBUG_TYPE "debug-info-btf-context"
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using namespace llvm;
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using object::ObjectFile;
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using object::SectionedAddress;
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DILineInfo BTFContext::getLineInfoForAddress(SectionedAddress Address,
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DILineInfoSpecifier Specifier) {
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const BTF::BPFLineInfo *LineInfo = BTF.findLineInfo(Address);
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DILineInfo Result;
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if (!LineInfo)
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return Result;
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Result.LineSource = BTF.findString(LineInfo->LineOff);
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Result.FileName = BTF.findString(LineInfo->FileNameOff);
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Result.Line = LineInfo->getLine();
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Result.Column = LineInfo->getCol();
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return Result;
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}
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DILineInfo BTFContext::getLineInfoForDataAddress(SectionedAddress Address) {
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// BTF does not convey such information.
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return {};
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}
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DILineInfoTable
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BTFContext::getLineInfoForAddressRange(SectionedAddress Address, uint64_t Size,
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DILineInfoSpecifier Specifier) {
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// This function is used only from llvm-rtdyld utility and a few
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// JITEventListener implementations. Ignore it for now.
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return {};
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}
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DIInliningInfo
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BTFContext::getInliningInfoForAddress(SectionedAddress Address,
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DILineInfoSpecifier Specifier) {
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// BTF does not convey such information
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return {};
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}
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std::vector<DILocal> BTFContext::getLocalsForAddress(SectionedAddress Address) {
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// BTF does not convey such information
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return {};
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}
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std::unique_ptr<BTFContext>
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BTFContext::create(const ObjectFile &Obj,
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std::function<void(Error)> ErrorHandler) {
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auto Ctx = std::make_unique<BTFContext>();
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BTFParser::ParseOptions Opts;
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Opts.LoadLines = true;
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if (Error E = Ctx->BTF.parse(Obj, Opts))
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ErrorHandler(std::move(E));
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return Ctx;
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}
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