zig

commit 4d77ef25f948cac32e4d5fd3f9df019e728fcb45 (tree)
parent 7a0022725342be8d3ea555a635da51f0e8c47b25
Author: Jakub Konka <kubkon@jakubkonka.com>
Date:   Thu, 14 Apr 2022 15:16:51 +0200

elf: check symtab section headers size when writing globals

Without this, it may happen we write the globals without extending
the symtab section header's size. This can potentially lead to
clobbering some data in the file, or simply omitting the globals
from the symtab when displaying with support tooling such as `readelf`.

Diffstat:
M
src/link/Elf.zig
 | 
16
++++++++++++++++

1 file changed, 16 insertions(+), 0 deletions(-)
diff --git a/src/link/Elf.zig b/src/link/Elf.zig
@@ -2799,6 +2799,22 @@ fn writeAllGlobalSymbols(self: *Elf) !void {
         .p32 => @sizeOf(elf.Elf32_Sym),
         .p64 => @sizeOf(elf.Elf64_Sym),
     };
+    const sym_align: u16 = switch (self.ptr_width) {
+        .p32 => @alignOf(elf.Elf32_Sym),
+        .p64 => @alignOf(elf.Elf64_Sym),
+    };
+    const needed_size = (self.local_symbols.items.len + self.global_symbols.items.len) * sym_size;
+    if (needed_size > self.allocatedSize(syms_sect.sh_offset)) {
+        // Move all the symbols to a new file location.
+        const new_offset = self.findFreeSpace(needed_size, sym_align);
+        const existing_size = @as(u64, syms_sect.sh_info) * sym_size;
+        const amt = try self.base.file.?.copyRangeAll(syms_sect.sh_offset, self.base.file.?, new_offset, existing_size);
+        if (amt != existing_size) return error.InputOutput;
+        syms_sect.sh_offset = new_offset;
+    }
+    syms_sect.sh_size = needed_size; // anticipating adding the global symbols later
+    self.shdr_table_dirty = true; // TODO look into only writing one section
+
     const foreign_endian = self.base.options.target.cpu.arch.endian() != builtin.cpu.arch.endian();
     const global_syms_off = syms_sect.sh_offset + self.local_symbols.items.len * sym_size;
     switch (self.ptr_width) {