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Signed-off-by: Alan Jowett <[email protected]>
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@Alan-Jowett
Alan-Jowett committed Jan 8, 2025
1 parent 76a6a71 commit 14b2b3f
Showing 1 changed file with 24 additions and 20 deletions.
44 changes: 24 additions & 20 deletions src/asm_files.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -162,16 +162,16 @@ get_program_name_and_size(const ELFIO::section& sec, const ELFIO::Elf_Xword star
return {program_name, size};
}

void relocate_map(ebpf_inst& inst, const std::string& symbol_name,
void relocate_map(ebpf_inst& reloc_inst, const std::string& symbol_name,
const std::variant<size_t, std::map<std::string, size_t>>& map_record_size_or_map_offsets,
const program_info& info, const ELFIO::Elf64_Addr offset, const ELFIO::Elf_Word index,
const ELFIO::const_symbol_section_accessor& symbols) {
// Only permit loading the address of the map.
if ((inst.opcode & INST_CLS_MASK) != INST_CLS_LD) {
if ((reloc_inst.opcode & INST_CLS_MASK) != INST_CLS_LD) {
throw UnmarshalError("Illegal operation on symbol " + symbol_name + " at location " +
std::to_string(offset / sizeof(ebpf_inst)));
}
inst.src = INST_LD_MODE_MAP_FD;
reloc_inst.src = INST_LD_MODE_MAP_FD;

// Relocation value is an offset into the "maps" or ".maps" section.
size_t reloc_value = std::numeric_limits<size_t>::max();
Expand All @@ -193,20 +193,22 @@ void relocate_map(ebpf_inst& inst, const std::string& symbol_name,
throw UnmarshalError("Bad reloc value (" + std::to_string(reloc_value) + "). " +
"Make sure to compile with -O2.");
}
inst.imm = info.map_descriptors.at(reloc_value).original_fd;
reloc_inst.imm = info.map_descriptors.at(reloc_value).original_fd;
}

void relocate_global_variable(
ebpf_inst& inst, ebpf_inst& inst_next, const std::string& symbol_name, const program_info& info,
const std::variant<size_t, std::map<std::string, size_t>>& map_record_size_or_map_offsets) {
void relocate_global_variable(ebpf_inst& reloc_inst, ebpf_inst& next_reloc_inst, const std::string& symbol_name,
const program_info& info,
const std::variant<size_t, std::map<std::string, size_t>>& map_record_size_or_map_offsets,
const ELFIO::Elf64_Addr offset) {
// Only permit loading the address of the global variable.
if ((inst.opcode & INST_CLS_MASK) != INST_CLS_LD) {
throw UnmarshalError("Illegal operation on symbol " + symbol_name);
if ((reloc_inst.opcode & INST_CLS_MASK) != INST_CLS_LD) {
throw UnmarshalError("Illegal operation on symbol " + symbol_name + " at location " +
std::to_string(offset / sizeof(ebpf_inst)));
}

// Copy the immediate value to the next instruction.
inst_next.imm = inst.imm;
inst.src = INST_LD_MODE_MAP_VALUE;
next_reloc_inst.imm = reloc_inst.imm;
reloc_inst.src = INST_LD_MODE_MAP_VALUE;

size_t reloc_value = std::numeric_limits<size_t>::max();
auto& map_descriptors_offsets = std::get<1>(map_record_size_or_map_offsets);
Expand All @@ -219,7 +221,7 @@ void relocate_global_variable(
throw UnmarshalError("Bad reloc value (" + std::to_string(reloc_value) + "). " +
"Make sure to compile with -O2.");
}
inst.imm = info.map_descriptors.at(reloc_value).original_fd;
reloc_inst.imm = info.map_descriptors.at(reloc_value).original_fd;
}

// Structure used to keep track of subprogram relocation data until any subprograms
Expand Down Expand Up @@ -471,15 +473,15 @@ vector<raw_program> read_elf(std::istream& input_stream, const std::string& path
if (offset / sizeof(ebpf_inst) >= prog.prog.size()) {
throw UnmarshalError("Invalid relocation data");
}
ebpf_inst& inst = prog.prog[offset / sizeof(ebpf_inst)];
ebpf_inst& inst_next = offset / sizeof(ebpf_inst) + 1 < prog.prog.size()
? prog.prog[offset / sizeof(ebpf_inst) + 1]
: inst;
ebpf_inst& reloc_inst = prog.prog[offset / sizeof(ebpf_inst)];
ebpf_inst& next_reloc_inst = offset / sizeof(ebpf_inst) + 1 < prog.prog.size()
? prog.prog[offset / sizeof(ebpf_inst) + 1]
: reloc_inst;

auto [symbol_name, symbol_section_index] = get_symbol_name_and_section_index(symbols, index);

// Queue up relocation for function symbols.
if (inst.opcode == INST_OP_CALL && inst.src == INST_CALL_LOCAL) {
if (reloc_inst.opcode == INST_OP_CALL && reloc_inst.src == INST_CALL_LOCAL) {
function_relocation fr{.prog_index = res.size(),
.source_offset = offset / sizeof(ebpf_inst),
.relocation_entry_index = index,
Expand All @@ -490,13 +492,15 @@ vector<raw_program> read_elf(std::istream& input_stream, const std::string& path

// Perform relocation for symbols located in the maps section.
if (map_section_indices.contains(symbol_section_index)) {
relocate_map(inst, symbol_name, map_record_size_or_map_offsets, info, offset, index, symbols);
relocate_map(reloc_inst, symbol_name, map_record_size_or_map_offsets, info, offset, index,
symbols);
continue;
}

if (global_variable_section_indices.contains(symbol_section_index)) {
relocate_global_variable(inst, inst_next, reader.sections[symbol_section_index]->get_name(),
info, map_record_size_or_map_offsets);
relocate_global_variable(reloc_inst, next_reloc_inst,
reader.sections[symbol_section_index]->get_name(), info,
map_record_size_or_map_offsets, offset);
continue;
}

Expand Down

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