From: Arnd Bergmann <arnd@arndb.de>
To: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Thomas Gleixner <tglx@linutronix.de>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
Andy Lutomirski <luto@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
"open list:BROADCOM NVRAM DRIVER" <linux-mips@vger.kernel.org>,
"the arch/x86 maintainers" <x86@kernel.org>
Subject: Re: [RFC PATCH v2 01/10] lib: vdso: ensure all arches have 32bit fallback
Date: Thu, 2 Jan 2020 12:29:12 +0100 [thread overview]
Message-ID: <CAK8P3a1gHvW2XEMDSHCcdOQ8NSs3iHk9GpujwkWZnnZ0dnw96w@mail.gmail.com> (raw)
In-Reply-To: <CAK8P3a0QGtjygLJUWX_1-s1vfCzE6UoOzrb+OZWwjaBdh=RpVQ@mail.gmail.com>
On Mon, Dec 30, 2019 at 1:27 PM Arnd Bergmann <arnd@arndb.de> wrote:
> On Mon, Dec 23, 2019 at 3:31 PM Christophe Leroy <christophe.leroy@c-s.fr> wrote:
> > +static __always_inline
> > +long clock_getres32_fallback(clockid_t _clkid, struct old_timespec32 *_ts)
> > +{
> > + struct __kernel_timespec ts;
> > + int ret = clock_getres_fallback(clock, &ts);
> > +
> > + if (likely(!ret && _ts)) {
> > + _ts->tv_sec = ts.tv_sec;
> > + _ts->tv_nsec = ts.tv_nsec;
> > + }
> > + return ret;
> > +}
>
> Please change these to call __NR_clock_gettime and __NR_clock_getres_time
> instead of __NR_clock_gettime64/__NR_clock_getres_time64 for multiple reasons.
>
> - When doing migration between containers, the vdso may get copied into
> an application running on a kernel that does not support the time64
> variants, and then the fallback fails.
>
> - When CONFIG_COMPAT_32BIT_TIME is disabled, the time32 syscalls
> return -ENOSYS, and the vdso version should have the exact same behavior
> to avoid surprises. In particular an application that checks clock_gettime()
> to see if the time32 are in part of the kernel would get an incorrect result
> here.
>
> arch/arm64/include/asm/vdso/compat_gettimeofday.h already does this,
> I think you can just copy the implementation or find a way to share it.
There was a related discussion on this after a vdso regression on mips,
and I suggested to drop the time32 functions completely from the
vdso when CONFIG_COMPAT_32BIT_TIME is disabled, such as
diff --git a/arch/powerpc/kernel/vdso32/vdso32.lds.S
b/arch/powerpc/kernel/vdso32/vdso32.lds.S
index 00c025ba4a92..605f259fa24c 100644
--- a/arch/powerpc/kernel/vdso32/vdso32.lds.S
+++ b/arch/powerpc/kernel/vdso32/vdso32.lds.S
@@ -145,10 +145,12 @@ VERSION
__kernel_get_syscall_map;
#ifndef CONFIG_PPC_BOOK3S_601
+#ifdef CONFIG_COMPAT_32BIT_TIME
__kernel_gettimeofday;
__kernel_clock_gettime;
__kernel_clock_getres;
__kernel_time;
+#endif
__kernel_get_tbfreq;
#endif
__kernel_sync_dicache;
Any opinions on this? If everyone agrees with that approach, I can
send a cross-architecture patch to do this everywhere. It's probably
best though if Christophe adds that to his series as it touches a lot
of the same files and I would prefer to avoid conflicting changes.
Arnd
next prev parent reply other threads:[~2020-01-02 11:29 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-23 14:31 [RFC PATCH v2 00/10] powerpc/32: switch VDSO to C implementation Christophe Leroy
2019-12-23 14:31 ` [RFC PATCH v2 01/10] lib: vdso: ensure all arches have 32bit fallback Christophe Leroy
2019-12-24 2:07 ` Andy Lutomirski
2020-01-10 20:56 ` Thomas Gleixner
2020-01-10 21:02 ` Andy Lutomirski
2019-12-30 12:27 ` Arnd Bergmann
2020-01-02 11:29 ` Arnd Bergmann [this message]
2020-01-09 15:43 ` Christophe Leroy
2019-12-23 14:31 ` [RFC PATCH v2 02/10] lib: vdso: move call to fallback out of common code Christophe Leroy
2019-12-24 2:24 ` Andy Lutomirski
2019-12-24 11:41 ` christophe leroy
2019-12-24 12:09 ` Andy Lutomirski
2019-12-23 14:31 ` [RFC PATCH v2 03/10] lib: vdso: Change __cvdso_clock_gettime/getres_common() to __cvdso_clock_gettime/getres() Christophe Leroy
2019-12-23 14:31 ` [RFC PATCH v2 04/10] lib: vdso: get pointer to vdso data from the arch Christophe Leroy
2019-12-24 2:27 ` Andy Lutomirski
2019-12-24 11:53 ` christophe leroy
2019-12-24 12:15 ` Andy Lutomirski
2019-12-24 12:41 ` Andy Lutomirski
2019-12-24 14:46 ` Segher Boessenkool
2019-12-23 14:31 ` [RFC PATCH v2 05/10] lib: vdso: inline do_hres() Christophe Leroy
2019-12-24 2:29 ` Andy Lutomirski
2019-12-30 12:07 ` Arnd Bergmann
2020-01-10 21:07 ` Thomas Gleixner
2020-01-11 9:06 ` Christophe Leroy
2019-12-23 14:31 ` [RFC PATCH v2 06/10] lib: vdso: make do_coarse() return 0 Christophe Leroy
2019-12-23 14:31 ` [RFC PATCH v2 07/10] lib: vdso: don't use READ_ONCE() in __c_kernel_time() Christophe Leroy
2019-12-24 1:58 ` Andy Lutomirski
2019-12-24 11:12 ` christophe leroy
2019-12-24 12:04 ` Andy Lutomirski
2020-01-10 21:12 ` Thomas Gleixner
2020-01-11 8:05 ` Christophe Leroy
2020-01-11 11:07 ` Thomas Gleixner
2020-01-13 6:52 ` Christophe Leroy
2019-12-23 14:31 ` [RFC PATCH v2 08/10] lib: vdso: Avoid duplication in __cvdso_clock_getres() Christophe Leroy
2019-12-24 1:59 ` Andy Lutomirski
2019-12-23 14:31 ` [RFC PATCH v2 09/10] powerpc/vdso32: inline __get_datapage() Christophe Leroy
2019-12-23 14:31 ` [RFC PATCH v2 10/10] powerpc/32: Switch VDSO to C implementation Christophe Leroy
2020-01-09 17:52 ` Surprising code generated for vdso_read_begin() Christophe Leroy
2020-01-09 20:07 ` Segher Boessenkool
2020-01-10 6:45 ` Christophe Leroy
2020-01-11 11:33 ` Segher Boessenkool
2020-02-16 18:10 ` Arnd Bergmann
2020-02-19 8:45 ` Christophe Leroy
2020-02-19 9:52 ` Arnd Bergmann
2020-02-19 13:08 ` Segher Boessenkool
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