Changeset 544c5b4 in mainline

Timestamp:

2025-01-25T16:25:39Z (10 days ago)

Author:

Matěj Volf <git@…>

Children:

4ef27eb

Parents:

328b89f

git-author:

Matěj Volf <git@…> (2025-01-24 23:59:36)

git-committer:

Matěj Volf <git@…> (2025-01-25 16:25:39)

Message:

a few comments for TLS allocation

File:

• uspace/lib/c/generic/thread/tls.c (modified) (2 diffs)

uspace/lib/c/generic/thread/tls.c

@@ -85 +85 @@
 static tcb_t *tls_make_generic(const void *elf, void *(*alloc)(size_t, size_t))
 {
+        /*
+         * See also rtld/module.c -> modules_process_tls(), where we have less
+         * messy code for the dynamic-linking version of this.
+         */
         assert(!elf_get_phdr(elf, PT_DYNAMIC));
 #ifdef CONFIG_RTLD
@@ -128 +132 @@
         uintptr_t bias = elf_get_bias(elf);
 
+        /*
+         * FIXME: I couldn't convince myself this is correct, but I couldn't
+         * find a case where it breaks either: if the actual alloc_size is
+         * bigger than the requested size (tls->p_memsz), the alignment padding
+         * will be placed at the beginning (because TLS is (at least sometimes?)
+         * indexed with negative offsets from the TCB pointer).
+         *
+         * Now we will copy the initialization data to a position at the start of
+         * the allocation, so if the padding has nonzero size, if think the initialization
+         * data is now incorrectly offset by its size?
+         */
+
         /* Copy thread local data from the initialization image. */
         memcpy(data, (void *)(tls->p_vaddr + bias), tls->p_filesz);