From 546e9289c74f606423ef72075b34cc38eda3bb49 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Thomas=20Wei=C3=9Fschuh?= Date: Fri, 23 Jan 2026 08:35:41 +0100 Subject: [PATCH] vdso/gettimeofday: Force inlining of __cvdso_clock_getres_common() MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Suggested-by: Christophe Leroy (CS GROUP) Signed-off-by: Thomas Weißschuh Signed-off-by: Thomas Gleixner 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 95df0153f05ab..4399e143d43a5 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) { -- 2.47.3