linux-kernel - [patch 04/15] lib/vdso: Allow the high resolution parts to be compiled out

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

Date:   Tue, 14 Jan 2020 19:52:41 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, John Stultz <john.stultz@...aro.org>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Andy Lutomirski <luto@...nel.org>,
        Christophe Leroy <christophe.leroy@....fr>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Sasha Levin <sashal@...nel.org>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paulburton@...nel.org>,
        James Hogan <jhogan@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Marc Zyngier <maz@...nel.org>
Subject: [patch 04/15] lib/vdso: Allow the high resolution parts to be compiled out

If the architecture knows at compile time that there is no VDSO capable
clocksource supported it makes sense to optimize the guts of the high
resolution parts of the VDSO out at build time. Add a helper function to
check whether the VDSO should be high resolution capable and provide a stub
which can be overridden by an architecture.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 lib/vdso/gettimeofday.c |   11 +++++++++++
 1 file changed, 11 insertions(+)

--- a/lib/vdso/gettimeofday.c
+++ b/lib/vdso/gettimeofday.c
@@ -38,6 +38,13 @@ u64 vdso_calc_delta(u64 cycles, u64 last
 }
 #endif
 
+#ifndef __arch_vdso_hres_capable
+static inline bool __arch_vdso_hres_capable(void)
+{
+	return true;
+}
+#endif
+
 #ifdef CONFIG_TIME_NS
 static int do_hres_timens(const struct vdso_data *vdns, clockid_t clk,
 			  struct __kernel_timespec *ts)
@@ -101,6 +108,10 @@ static __always_inline int do_hres(const
 	u64 cycles, last, sec, ns;
 	u32 seq;
 
+	/* Allows to compile the high resilution parts out */
+	if (!__arch_vdso_hres_capable())
+		return -1;
+
 	do {
 		/*
 		 * Open coded to handle VCLOCK_TIMENS. Time namespace