Changeset b27ae65a in mainline for uspace/lib/c/generic/rtld/module.c

Timestamp:

2025-01-27T12:45:12Z (11 days ago)

Author:

GitHub <noreply@…>

Branches:

master

Children:

97116a2

Parents:

eff458d

git-author:

Matěj Volf <mat.volfik@…> (2025-01-27 12:45:12)

git-committer:

GitHub <noreply@…> (2025-01-27 12:45:12)

Message:

fix calculation of TLS size for main fibril (#240)

• explain why tcb_t is added at the end of tls allocation

• fix calculation of TLS size for main fibril

Before this patch, _tcb_data_offset always used progsymbols.elfstart. However,
that is wrong when it is being called from the loader server!! Now we pass to it
a pointer to the correct ELF, falling back to elfstart in the public tls_get call.

(debugging this was quite an ordeal and took me like 5 hours, thanks for asking ('

• a few comments for TLS allocation

File:

• uspace/lib/c/generic/rtld/module.c (modified) (1 diff)

uspace/lib/c/generic/rtld/module.c

@@ -398 +398 @@
          * be correct, "zero" offset (i.e. the total size) must be aligned
          * to the strictest alignment present.
-         * Note that the padding is actually in front of the TLS data,
-         * not after it.
          */
         rtld->tls_size = ALIGN_UP(rtld->tls_size, rtld->tls_align);
 
-        /* Space for the TCB. */
+        /*
+         * Space for the TCB.
+         * Later, the TLS zero offset is equal to the pointer to tcb_t, so
+         * adding the sizeof(tcb_t) block AFTER we calculated the alignment
+         * of the remainder above is correct.
+         */
         rtld->tls_size += sizeof(tcb_t);
 #endif