zig

commit 37275c0f69769774ba4f1fc577b04aa36e24ac6f (tree)
parent b52e05426160c193c29e01072736a319e5fb6f24
Author: Alex Rønne Petersen <alex@alexrp.com>
Date:   Mon, 29 Jul 2024 12:19:15 +0200

std.os.linux.tls: Fix layout computation for the modified Variant I.

Diffstat:
M
lib/std/os/linux/tls.zig
 | 
20
+++++++++++++++++++-

1 file changed, 19 insertions(+), 1 deletion(-)
diff --git a/lib/std/os/linux/tls.zig b/lib/std/os/linux/tls.zig
@@ -313,7 +313,7 @@ fn computeAreaDesc(phdrs: []elf.Phdr) void {
     // Compute the total size of the ABI-specific data plus our own `ZigTcb` structure. All the
     // offsets calculated here assume a well-aligned base address.
     const area_size = switch (current_variant) {
-        .I_original, .I_modified => blk: {
+        .I_original => blk: {
             var l: usize = 0;
             dtv_offset = l;
             l += @sizeOf(Dtv);
@@ -330,6 +330,24 @@ fn computeAreaDesc(phdrs: []elf.Phdr) void {
             l += block_size;
             break :blk l;
         },
+        .I_modified => blk: {
+            var l: usize = 0;
+            dtv_offset = l;
+            l += @sizeOf(Dtv);
+            // In this variant, the TLS blocks must begin immediately after the end of the ABI TCB,
+            // with the TP pointing to the beginning of the TLS blocks. Add padding so that the TP
+            // (`abi_tcb_offset`) is aligned to `align_factor` and the `ZigTcb` structure can be
+            // found by subtracting `@sizeOf(AbiTcb) + @sizeOf(ZigTcb)` from the TP.
+            const delta = (l + @sizeOf(ZigTcb) + @sizeOf(AbiTcb)) & (align_factor - 1);
+            if (delta > 0)
+                l += align_factor - delta;
+            l += @sizeOf(ZigTcb);
+            abi_tcb_offset = l;
+            l += @sizeOf(AbiTcb);
+            block_offset = l;
+            l += block_size;
+            break :blk l;
+        },
         .II => blk: {
             var l: usize = 0;
             block_offset = l;