new file mode 100644
@@ -0,0 +1,77 @@
+/* extra tls block utils for the dynamic linker. Generic stub version.
+ Copyright (C) 2024 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#ifndef _DL_EXTRA_TLS_H
+#define _DL_EXTRA_TLS_H 1
+
+#include <stddef.h>
+#include <sys/rseq.h>
+#include <rseq-internal.h>
+#include <elf/dl-tunables.h>
+
+/* Returns the size of the extra TLS block. */
+static inline size_t
+_dl_extra_tls_get_size (void)
+{
+ bool do_rseq = true;
+ do_rseq = TUNABLE_GET_FULL (glibc, pthread, rseq, int, NULL);
+ if (do_rseq)
+ {
+ /* Make sure the rseq area size is at least the minimum ABI size and a
+ multiple of the requested aligment. */
+ return roundup (MAX (GLRO (dl_rseq_feature_size), RSEQ_AREA_MIN_SIZE),
+ GLRO (dl_rseq_align));
+ }
+
+ /* Even when disabled by tunable, an rseq area will be allocated to allow
+ application code to test the registration status with 'rseq->cpu_id >= 0'.
+ Default to the rseq ABI minimum size, this will ensure we don't use more
+ TLS than necessary. */
+ return RSEQ_AREA_MIN_SIZE;
+}
+
+/* Returns the alignment requirements of the extra TLS block. */
+static inline size_t
+_dl_extra_tls_get_align (void)
+{
+ bool do_rseq = true;
+ do_rseq = TUNABLE_GET_FULL (glibc, pthread, rseq, int, NULL);
+ if (do_rseq)
+ {
+ return GLRO (dl_rseq_align);
+ }
+
+ /* Even when disabled by tunable, an rseq area will be allocated to allow
+ application code to test the registration status with 'rseq->cpu_id >= 0'.
+ Default to the rseq ABI minimum alignment, this will ensure we don't use
+ more TLS than necessary. */
+ return RSEQ_MIN_ALIGN;
+}
+
+/* Record the offset of the extra TLS block from the thread pointer. */
+static inline void
+_dl_extra_tls_set_offset (ptrdiff_t tls_offset)
+{
+#ifdef RSEQ_SIG
+ /* Not all targets support __thread_pointer, so set __rseq_offset only if
+ the rseq registration may have happened because RSEQ_SIG is defined. */
+ _rseq_offset = tls_offset;
+#endif
+}
+
+#endif
@@ -30,6 +30,9 @@
#define RSEQ_AREA_SIZE_INITIAL 32
#define RSEQ_AREA_SIZE_INITIAL_USED 20
+/* Minimum size of the rseq area. */
+#define RSEQ_AREA_MIN_SIZE 32
+
/* Minimum feature size of the rseq area. */
#define RSEQ_MIN_FEATURE_SIZE 20
Add the Linux implementation of 'extra TLS' which will allocate space for the rseq area at the end of the TLS blocks in allocation order. Signed-off-by: Michael Jeanson <mjeanson@efficios.com> --- sysdeps/unix/sysv/linux/dl-extra_tls.h | 77 +++++++++++++++++++++++++++++++++ sysdeps/unix/sysv/linux/rseq-internal.h | 3 ++ 2 files changed, 80 insertions(+)