zig

commit 704f8f4013dee59c899f8900ee2289983bb9d5da (tree)
parent ef9fb428b7433238b9c0bd38d3ff36accf0f3d12
Author: Alexandre Janon <alex14fr@gmail.com>
Date:   Sun, 28 Apr 2024 11:45:50 +0200

Fix ELF alignment for freestanding targets (#19766)

* Fix the ELF binaries for freestanding target created with the self-hosted linker.

    The ELF specification (generic ABI) states that ``loadable process segments must have congruent
    values for p_vaddr and p_offset, modulo the page size''. Linux refuses to load binaries that
    don't meet this requirement (execve() fails with EINVAL).
Diffstat:
M
src/link/Elf.zig
 | 
11
++++-------

1 file changed, 4 insertions(+), 7 deletions(-)
diff --git a/src/link/Elf.zig b/src/link/Elf.zig
@@ -648,7 +648,6 @@ pub fn initMetadata(self: *Elf, options: InitMetadataOptions) !void {
     const ptr_size = self.ptrWidthBytes();
     const target = self.base.comp.root_mod.resolved_target.result;
     const ptr_bit_width = target.ptrBitWidth();
-    const has_os = target.os.tag != .freestanding;
     const zig_object = self.zigObjectPtr().?;
 
     const fillSection = struct {
@@ -684,9 +683,7 @@ pub fn initMetadata(self: *Elf, options: InitMetadataOptions) !void {
         }
 
         if (self.phdr_zig_got_index == null) {
-            // We really only need ptr alignment but since we are using PROGBITS, linux requires
-            // page align.
-            const alignment = if (has_os) self.page_size else @as(u16, ptr_size);
+            const alignment = self.page_size;
             const filesz = @as(u64, ptr_size) * options.symbol_count_hint;
             const off = self.findFreeSpace(filesz, alignment);
             self.phdr_zig_got_index = try self.addPhdr(.{
@@ -701,7 +698,7 @@ pub fn initMetadata(self: *Elf, options: InitMetadataOptions) !void {
         }
 
         if (self.phdr_zig_load_ro_index == null) {
-            const alignment = if (has_os) self.page_size else @as(u16, ptr_size);
+            const alignment = self.page_size;
             const filesz: u64 = 1024;
             const off = self.findFreeSpace(filesz, alignment);
             self.phdr_zig_load_ro_index = try self.addPhdr(.{
@@ -716,7 +713,7 @@ pub fn initMetadata(self: *Elf, options: InitMetadataOptions) !void {
         }
 
         if (self.phdr_zig_load_rw_index == null) {
-            const alignment = if (has_os) self.page_size else @as(u16, ptr_size);
+            const alignment = self.page_size;
             const filesz: u64 = 1024;
             const off = self.findFreeSpace(filesz, alignment);
             self.phdr_zig_load_rw_index = try self.addPhdr(.{
@@ -731,7 +728,7 @@ pub fn initMetadata(self: *Elf, options: InitMetadataOptions) !void {
         }
 
         if (self.phdr_zig_load_zerofill_index == null) {
-            const alignment = if (has_os) self.page_size else @as(u16, ptr_size);
+            const alignment = self.page_size;
             self.phdr_zig_load_zerofill_index = try self.addPhdr(.{
                 .type = elf.PT_LOAD,
                 .addr = if (ptr_bit_width >= 32) 0x14000000 else 0xf000,