linux-kernel - [tip: timers/vdso] vdso/gettimeofday: Force inlining of __cvdso_clock_getres

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <176946312622.510.10415796327436735908.tip-bot2@tip-bot2>
Date: Mon, 26 Jan 2026 21:32:06 -0000
From: tip-bot2 for Thomas Weißschuh <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: "Sverdlin, Alexander" <alexander.sverdlin@...mens.com>,
 "Christophe Leroy (CS GROUP)" <chleroy@...nel.org>,
 thomas.weissschuh@...utronix.de, Thomas Gleixner <tglx@...nel.org>,
 x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: timers/vdso] vdso/gettimeofday: Force inlining of
 __cvdso_clock_getres_common()

The following commit has been merged into the timers/vdso branch of tip:

Commit-ID:     546e9289c74f606423ef72075b34cc38eda3bb49
Gitweb:        https://git.kernel.org/tip/546e9289c74f606423ef72075b34cc38eda3bb49
Author:        Thomas Weißschuh <thomas.weissschuh@...utronix.de>
AuthorDate:    Fri, 23 Jan 2026 08:35:41 +01:00
Committer:     Thomas Gleixner <tglx@...nel.org>
CommitterDate: Mon, 26 Jan 2026 22:27:07 +01:00

vdso/gettimeofday: Force inlining of __cvdso_clock_getres_common()

With CONFIG_CC_OPTIMIZE_FOR_SIZE=y, GCC may decide not to inline
__cvdso_clock_getres_common(). This introduces spurious internal
function calls in the vDSO fastpath.

Furthermore, with automatic stack variable initialization
(CONFIG_INIT_STACK_ALL_ZERO or CONFIG_INIT_STACK_ALL_PATTERN) GCC can emit
a call to memset() which is not valid in the vDSO.

Mark __cvdso_clock_getres_common() as __always_inline to avoid both issues.

Paradoxically the inlining even reduces the size of the code:

$ ./scripts/bloat-o-meter arch/powerpc/kernel/vdso/vgettimeofday-32.o.before arch/powerpc/kernel/vdso/vgettimeofday-32.o.after
add/remove: 0/1 grow/shrink: 1/1 up/down: 52/-148 (-96)
Function                                     old     new   delta
__c_kernel_clock_getres_time64                92     144     +52
__c_kernel_clock_getres                      136     132      -4
__cvdso_clock_getres_common                  144       -    -144
Total: Before=2788, After=2692, chg -3.44%

With CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE=y the functions are always inlined
and therefore the behaviour stays the same.

See also the equivalent change for clock_gettime() in commit b91c8c42ffdd
("lib/vdso: Force inlining of __cvdso_clock_gettime_common()").

Fixes: 21bbfd74044f ("x86/vdso: Provide clock_getres_time64() for x86-32")
Fixes: 1149dcdfc9ef ("ARM: VDSO: Provide clock_getres_time64()")
Fixes: f10c2e72b5de ("arm64: vdso32: Provide clock_getres_time64()")
Fixes: bec06cd6a140 ("MIPS: vdso: Provide getres_time64() for 32-bit ABIs")
Fixes: 759a1f97373f ("powerpc/vdso: Provide clock_getres_time64()")
Reported-by: Sverdlin, Alexander <alexander.sverdlin@...mens.com>
Suggested-by: Christophe Leroy (CS GROUP) <chleroy@...nel.org>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Signed-off-by: Thomas Gleixner <tglx@...nel.org>
Link: https://lore.kernel.org/lkml/230c749f-ebd6-4829-93ee-601d88000a45@kernel.org/
Link: https://patch.msgid.link/20260123-vdso-clock_getres-inline-v1-1-4d6203b90cd3@linutronix.de
Closes: https://lore.kernel.org/lkml/f45316f65a46da638b3c6aa69effd8980e6677b9.camel@siemens.com/
---
 lib/vdso/gettimeofday.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/vdso/gettimeofday.c b/lib/vdso/gettimeofday.c
index 95df015..4399e14 100644
--- a/lib/vdso/gettimeofday.c
+++ b/lib/vdso/gettimeofday.c
@@ -421,7 +421,7 @@ static __maybe_unused __kernel_old_time_t __cvdso_time(__kernel_old_time_t *time
 #endif /* VDSO_HAS_TIME */
 
 #ifdef VDSO_HAS_CLOCK_GETRES
-static __maybe_unused
+static __always_inline
 bool __cvdso_clock_getres_common(const struct vdso_time_data *vd, clockid_t clock,
 				 struct __kernel_timespec *res)
 {