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simplify mapping

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This commit is contained in:
Pascal Zittlau
2025-12-01 15:41:27 +01:00
parent 53522a6e5d
commit ba6ab39f91
1 changed files with 4 additions and 17 deletions
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21
src/main.zig
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@@ -138,18 +138,15 @@ fn loadStaticElf(ehdr: elf.Header, file_reader: *std.fs.File.Reader) !usize {
const base = try posix.mmap( const base = try posix.mmap(
hint, hint,
maxva - minva, maxva - minva,
posix.PROT.NONE, posix.PROT.WRITE,
.{ .TYPE = .PRIVATE, .ANONYMOUS = true, .FIXED = !dynamic }, .{ .TYPE = .PRIVATE, .ANONYMOUS = true, .FIXED_NOREPLACE = !dynamic },
-1, -1,
0, 0,
); );
posix.munmap(base);
const flags = posix.MAP{ .TYPE = .PRIVATE, .ANONYMOUS = true, .FIXED = true };
var phdrs = ehdr.iterateProgramHeaders(file_reader); var phdrs = ehdr.iterateProgramHeaders(file_reader);
var phdr_idx: u32 = 0;
errdefer posix.munmap(base); errdefer posix.munmap(base);
while (try phdrs.next()) |phdr| : (phdr_idx += 1) { while (try phdrs.next()) |phdr| {
if (phdr.p_type != elf.PT_LOAD) continue; if (phdr.p_type != elf.PT_LOAD) continue;
if (phdr.p_memsz == 0) continue; if (phdr.p_memsz == 0) continue;
@@ -158,17 +155,7 @@ fn loadStaticElf(ehdr: elf.Header, file_reader: *std.fs.File.Reader) !usize {
var start = mem.alignBackward(usize, phdr.p_vaddr, page_size); var start = mem.alignBackward(usize, phdr.p_vaddr, page_size);
const base_for_dyn = if (dynamic) @intFromPtr(base.ptr) else 0; const base_for_dyn = if (dynamic) @intFromPtr(base.ptr) else 0;
start += base_for_dyn; start += base_for_dyn;
// NOTE: We can't use a single file-backed mmap for the segment, because p_memsz may be const ptr: []align(page_size) u8 = @as([*]align(page_size) u8, @ptrFromInt(start))[0..size];
// larger than p_filesz. This difference accounts for the .bss section, which must be
// zero-initialized.
const ptr = try posix.mmap(
@as(?[*]align(page_size) u8, @ptrFromInt(start)),
size,
posix.PROT.WRITE,
flags,
-1,
0,
);
try file_reader.seekTo(phdr.p_offset); try file_reader.seekTo(phdr.p_offset);
if (try file_reader.read(ptr[offset..][0..phdr.p_filesz]) != phdr.p_filesz) if (try file_reader.read(ptr[offset..][0..phdr.p_filesz]) != phdr.p_filesz)
return UnfinishedReadError.UnfinishedRead; return UnfinishedReadError.UnfinishedRead;