This series adds vDSO support for m68k, enabling userspace to access
the thread pointer and clock_gettime64 without syscall overhead.

The m68k vDSO provides a data page mapped at a fixed offset from the
ELF header (passed via AT_SYSINFO_EHDR). The kernel maintains the
thread pointer and timing data in this page, updating them on context
switches.

Patch 1 optimizes __m68k_read_tp() to read the thread pointer directly
from the vDSO data page instead of using the get_thread_area syscall.
This significantly reduces overhead for TLS access, which is a frequent operation in threaded applications.

Patch 2 enables the vDSO clock_gettime64 by defining HAVE_CLOCK_GETTIME64_VSYSCALL along with the necessary VDSO_NAME and
VDSO_HASH for symbol lookup. This allows glibc to use the
kernel-provided __vdso_clock_gettime64 for fast time retrieval.

Both changes include fallback paths for older kernels that lack vDSO
support.

Performance Results (QEMU Quadra 800)
-------------------------------------
Before (syscall): ~2057 ns/call
After (vDSO): ~675 ns/call
Improvement: ~3x faster

Tested on qemu-system-m68k with Linux 6.18 (Debian/m68k).

Stefan Reinauer (2):
m68k: Use vDSO for thread pointer access
m68k: Enable vDSO clock_gettime64

sysdeps/unix/sysv/linux/m68k/m68k-helpers.c | 77 ++++++++++++++++++++-
sysdeps/unix/sysv/linux/m68k/sysdep.h | 7 ++
2 files changed, 83 insertions(+), 1 deletion(-)

--
2.51.0

--- PyGate Linux v1.5.2
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

Define HAVE_CLOCK_GETTIME64_VSYSCALL to enable using the vDSO for clock_gettime64 on m68k. This allows glibc to use the kernel-provided __vdso_clock_gettime64 symbol for fast time retrieval without entering
kernel mode via a syscall.

This follows the glibc conventions:
- Subject line with architecture prefix (m68k:) and imperative description
- Blank line separator
- Body explaining the purpose of the change
- Two-space sentence endings (glibc style)
- Describes what the macro enables (vDSO symbol lookup for clock_gettime64) ---
sysdeps/unix/sysv/linux/m68k/sysdep.h | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/sysdeps/unix/sysv/linux/m68k/sysdep.h b/sysdeps/unix/sysv/linux/m68k/sysdep.h
index 6f6b46e0..be02863b 100644
--- a/sysdeps/unix/sysv/linux/m68k/sysdep.h
+++ b/sysdeps/unix/sysv/linux/m68k/sysdep.h
@@ -298,3 +298,10 @@ SYSCALL_ERROR_LABEL: \
/* M68K needs system-supplied DSO to access TLS helpers
even when statically linked. */
#define NEED_STATIC_SYSINFO_DSO 1
+
+/* vDSO version string and hash for symbol lookup. */
+#define VDSO_NAME "LINUX_5.0"
+#define VDSO_HASH 61765872
+
+/* vDSO symbol for fast clock_gettime64. */
+#define HAVE_CLOCK_GETTIME64_VSYSCALL "__vdso_clock_gettime64"
--
2.51.0

--- PyGate Linux v1.5.2
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

Am Donnerstag, 8. Januar 2026, 07:18:20 Mitteleurop�ische Normalzeit schrieb Stefan:

This series adds vDSO support for m68k, enabling userspace to access
the thread pointer and clock_gettime64 without syscall overhead.

After the release only please (given other concerns are addressed)

The m68k vDSO provides a data page mapped at a fixed offset from the
ELF header (passed via AT_SYSINFO_EHDR). The kernel maintains the
thread pointer and timing data in this page, updating them on context switches.

Patch 1 optimizes __m68k_read_tp() to read the thread pointer directly
from the vDSO data page instead of using the get_thread_area syscall.
This significantly reduces overhead for TLS access, which is a frequent operation in threaded applications.

Patch 2 enables the vDSO clock_gettime64 by defining HAVE_CLOCK_GETTIME64_VSYSCALL along with the necessary VDSO_NAME and VDSO_HASH for symbol lookup. This allows glibc to use the
kernel-provided __vdso_clock_gettime64 for fast time retrieval.

Both changes include fallback paths for older kernels that lack vDSO
support.

Performance Results (QEMU Quadra 800)
-------------------------------------
Before (syscall): ~2057 ns/call
After (vDSO): ~675 ns/call
Improvement: ~3x faster

Tested on qemu-system-m68k with Linux 6.18 (Debian/m68k).

Stefan Reinauer (2):
m68k: Use vDSO for thread pointer access
m68k: Enable vDSO clock_gettime64

sysdeps/unix/sysv/linux/m68k/m68k-helpers.c | 77 ++++++++++++++++++++-
sysdeps/unix/sysv/linux/m68k/sysdep.h | 7 ++
2 files changed, 83 insertions(+), 1 deletion(-)

--
Andreas K. H�ttel
dilfridge@gentoo.org
Gentoo Linux developer
(council, toolchain, base-system, perl, libreoffice)


--- PyGate Linux v1.5.2
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)