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objcopy: support some more elf file variants

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"SHT_NOBITS" sections can be easily moved around in the file, they can be anywhere since there is no data...

and remove logic about the categorization of symbol tables:
  I don't understand or remember why it was needed,
  and, in my tests, it works fine without...

It previouly failed to strip an exe linked with `mold`
This commit is contained in:
Xavier Bouchoux 2023-05-12 21:45:23 +02:00
parent 423d7b848b
commit 5eacddce99
1 changed files with 7 additions and 28 deletions
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35
src/objcopy.zig
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@ -817,7 +817,7 @@ fn ElfFile(comptime is_64: bool) type {
// fill-in sections info:
// resolve the name
// find if a program segment uses the section
// categorise sections usage (used by program segments, debug datadase, common metadata, symbol table)
// categorize sections usage (used by program segments, debug datadase, common metadata, symbol table)
for (sections) |*section| {
section.segment = for (program_segments) |*seg| {
if (sectionWithinSegment(section.section, seg.*)) break seg;
@ -836,8 +836,8 @@ fn ElfFile(comptime is_64: bool) type {
if (std.mem.eql(u8, section.name, ".gnu_debuglink")) break :cat .none;
break :cat category_from_program;
},
elf.SHT_LOPROC...elf.SHT_HIPROC => .common, // don't strip unkonwn sections
elf.SHT_LOUSER...elf.SHT_HIUSER => .common, // don't strip unkonwn sections
elf.SHT_LOPROC...elf.SHT_HIPROC => .common, // don't strip unknown sections
elf.SHT_LOUSER...elf.SHT_HIUSER => .common, // don't strip unknown sections
else => category_from_program,
};
}
@ -846,7 +846,7 @@ fn ElfFile(comptime is_64: bool) type {
if (header.shstrndx != elf.SHN_UNDEF)
sections[header.shstrndx].category = .common; // string table for the headers
// recursive dependencies
// recursively propagate section categories to their linked sections, so that they are kept together
var dirty: u1 = 1;
while (dirty != 0) {
dirty = 0;
@ -856,29 +856,6 @@ fn ElfFile(comptime is_64: bool) type {
dirty |= ElfFileHelper.propagateCategory(&sections[section.section.sh_link].category, section.category);
if ((section.section.sh_flags & elf.SHF_INFO_LINK) != 0 and section.section.sh_info != elf.SHN_UNDEF)
dirty |= ElfFileHelper.propagateCategory(&sections[section.section.sh_info].category, section.category);
if (section.payload) |data| {
switch (section.section.sh_type) {
elf.DT_VERSYM => {
assert(section.section.sh_entsize == @sizeOf(Elf_Verdef));
const defs = @ptrCast([*]const Elf_Verdef, data)[0 .. @intCast(usize, section.section.sh_size) / @sizeOf(Elf_Verdef)];
for (defs) |def| {
if (def.vd_ndx != elf.SHN_UNDEF)
dirty |= ElfFileHelper.propagateCategory(&sections[def.vd_ndx].category, section.category);
}
},
elf.SHT_SYMTAB, elf.SHT_DYNSYM => {
assert(section.section.sh_entsize == @sizeOf(Elf_Sym));
const syms = @ptrCast([*]const Elf_Sym, data)[0 .. @intCast(usize, section.section.sh_size) / @sizeOf(Elf_Sym)];
for (syms) |sym| {
if (sym.st_shndx != elf.SHN_UNDEF and sym.st_shndx < elf.SHN_LORESERVE)
dirty |= ElfFileHelper.propagateCategory(&sections[sym.st_shndx].category, section.category);
}
},
else => {},
}
}
}
}
@ -994,6 +971,8 @@ fn ElfFile(comptime is_64: bool) type {
// this code only supports when they are in increasing file order.
var offset: u64 = eof_offset;
for (self.sections[1..]) |section| {
if (section.section.sh_type == elf.SHT_NOBITS)
continue;
if (section.section.sh_offset < offset) {
fatal("zig objcopy: unsuported ELF file", .{});
}
@ -1025,7 +1004,7 @@ fn ElfFile(comptime is_64: bool) type {
const addralign = if (src.sh_addralign == 0 or dest.sh_type == elf.SHT_NOBITS) 1 else src.sh_addralign;
dest.sh_offset = std.mem.alignForward(Elf_OffSize, eof_offset, addralign);
if (src.sh_offset != dest.sh_offset and section.segment != null and update.action != .empty and dest.sh_type != elf.SHT_NOTE) {
if (src.sh_offset != dest.sh_offset and section.segment != null and update.action != .empty and dest.sh_type != elf.SHT_NOTE and dest.sh_type != elf.SHT_NOBITS) {
if (src.sh_offset > dest.sh_offset) {
dest.sh_offset = src.sh_offset; // add padding to avoid modifing the program segments
} else {