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zld: populate sections from the top rather than from bottom

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This commit is contained in:
Jakub Konka 2021-07-10 22:39:31 +02:00
parent 714e0c4761
commit 95aeb09b9b
2 changed files with 32 additions and 19 deletions
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1
src/link/MachO/Object.zig
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@ -502,6 +502,7 @@ pub fn parseTextBlocks(self: *Object, zld: *Zld) !void {
// Is there any padding between symbols within the section?
const is_splittable = self.header.?.flags & macho.MH_SUBSECTIONS_VIA_SYMBOLS != 0;
// const is_splittable = false;
next: {
if (is_splittable) blocks: {

50
src/link/MachO/Zld.zig
View File

@ -1046,22 +1046,28 @@ fn allocateTextBlocks(self: *Zld) !void {
const match = entry.key_ptr.*;
var block: *TextBlock = entry.value_ptr.*;
// Find the first block
while (block.prev) |prev| {
block = prev;
}
const seg = self.load_commands.items[match.seg].Segment;
const sect = seg.sections.items[match.sect];
var base_addr: u64 = sect.addr + sect.size;
log.debug(" within section {s},{s}", .{ segmentName(sect), sectionName(sect) });
log.debug(" {}", .{sect});
var base_addr: u64 = sect.addr;
log.warn(" within section {s},{s}", .{ segmentName(sect), sectionName(sect) });
log.warn(" {}", .{sect});
while (true) {
const block_alignment = try math.powi(u32, 2, block.alignment);
base_addr = mem.alignBackwardGeneric(u64, base_addr - block.size, block_alignment);
base_addr = mem.alignForwardGeneric(u64, base_addr, block_alignment);
const sym = self.locals.items[block.local_sym_index];
assert(sym.payload == .regular);
sym.payload.regular.address = base_addr;
log.debug(" {s}: start=0x{x}, end=0x{x}, size={}, align={}", .{
log.warn(" {s}: start=0x{x}, end=0x{x}, size={}, align={}", .{
sym.name,
base_addr,
base_addr + block.size,
@ -1087,8 +1093,10 @@ fn allocateTextBlocks(self: *Zld) !void {
}
}
if (block.prev) |prev| {
block = prev;
base_addr += block.size;
if (block.next) |next| {
block = next;
} else break;
}
}
@ -1102,12 +1110,16 @@ fn writeTextBlocks(self: *Zld) !void {
const match = entry.key_ptr.*;
var block: *TextBlock = entry.value_ptr.*;
while (block.prev) |prev| {
block = prev;
}
const seg = self.load_commands.items[match.seg].Segment;
const sect = seg.sections.items[match.sect];
const sect_type = sectionType(sect);
log.debug(" for section {s},{s}", .{ segmentName(sect), sectionName(sect) });
log.debug(" {}", .{sect});
log.warn(" for section {s},{s}", .{ segmentName(sect), sectionName(sect) });
log.warn(" {}", .{sect});
var code = try self.allocator.alloc(u8, sect.size);
defer self.allocator.free(code);
@ -1115,15 +1127,14 @@ fn writeTextBlocks(self: *Zld) !void {
if (sect_type == macho.S_ZEROFILL or sect_type == macho.S_THREAD_LOCAL_ZEROFILL) {
mem.set(u8, code, 0);
} else {
var base_off: u64 = sect.size;
var base_off: u64 = 0;
while (true) {
const block_alignment = try math.powi(u32, 2, block.alignment);
const unaligned_base_off = base_off - block.size;
const aligned_base_off = mem.alignBackwardGeneric(u64, unaligned_base_off, block_alignment);
const aligned_base_off = mem.alignForwardGeneric(u64, base_off, block_alignment);
const sym = self.locals.items[block.local_sym_index];
log.debug(" {s}: start=0x{x}, end=0x{x}, size={}, align={}", .{
log.warn(" {s}: start=0x{x}, end=0x{x}, size={}, align={}", .{
sym.name,
aligned_base_off,
aligned_base_off + block.size,
@ -1135,16 +1146,17 @@ fn writeTextBlocks(self: *Zld) !void {
mem.copy(u8, code[aligned_base_off..][0..block.size], block.code);
// TODO NOP for machine code instead of just zeroing out
const padding_off = aligned_base_off + block.size;
const padding_len = unaligned_base_off - aligned_base_off;
mem.set(u8, code[padding_off..][0..padding_len], 0);
const padding_len = aligned_base_off - base_off;
mem.set(u8, code[base_off..][0..padding_len], 0);
base_off = aligned_base_off;
base_off = aligned_base_off + block.size;
if (block.prev) |prev| {
block = prev;
if (block.next) |next| {
block = next;
} else break;
}
mem.set(u8, code[base_off..], 0);
}
try self.file.?.pwriteAll(code, sect.offset);