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    SubjectRe: [PATCH 01/19] compat ABI: use non-compat openat and open_by_handle_at variants
    On Thu, Aug 25, 2016 at 05:52:11PM +0200, Arnd Bergmann wrote:
    > On Monday, August 15, 2016 5:30:28 PM CEST Yury Norov wrote:
    > > On Mon, Jun 27, 2016 at 09:47:38AM +0200, Andreas Schwab wrote:
    > > > Yury Norov <ynorov@caviumnetworks.com> writes:
    > > >
    > > > > The only difference is that non-compat version forces O_LARGEFILE,
    > > > > and it should be the default behaviour for all architectures, as
    > > > > we don't support 32-bit off_t. The only exception is tile32, that
    > > > > continues with compat version of syscalls.
    > > > >
    > > > > Signed-off-by: Yury Norov <ynorov@caviumnetworks.com>
    > > > > Acked-by: Arnd Bergmann <arnd@arndb.de>
    > > > > Acked-by: Chris Metcalf <cmetcalf@ezchip.com> [for tile]
    > > > > ---
    > > > > arch/tile/kernel/compat.c | 3 +++
    > > > > 1 file changed, 3 insertions(+)
    > > > >
    > > > > diff --git a/arch/tile/kernel/compat.c b/arch/tile/kernel/compat.c
    > > > > index 4912084..489ae19 100644
    > > > > --- a/arch/tile/kernel/compat.c
    > > > > +++ b/arch/tile/kernel/compat.c
    > > > > @@ -94,6 +94,9 @@ COMPAT_SYSCALL_DEFINE5(llseek, unsigned int, fd, unsigned int, offset_high,
    > > > > #define compat_sys_readahead sys32_readahead
    > > > > #define sys_llseek compat_sys_llseek
    > > > >
    > > > > +#define sys_openat compat_sys_openat
    > > > > +#define sys_open_by_handle_at compat_sys_open_by_handle_at
    > > > > +
    > > > > /* Call the assembly trampolines where necessary. */
    > > > > #define compat_sys_rt_sigreturn _compat_sys_rt_sigreturn
    > > > > #define sys_clone _sys_clone
    > > >
    > > > This is a no-op. Did you mean to add this? Without that the testsuite
    > > > of tar fails on ILP32.
    > >
    > > The change you suggest below is what I originally sent at the end of
    > > December, but that chunk was lost after one of numerous rebases probably.
    > >
    > > http://lkml.iu.edu/hypermail/linux/kernel/1512.3/00510.html
    > >
    > > IIRC, the only difference between this couple of syscalls and their
    > > compat versions is that non-compat syscalls set O_LARGEFILE depending
    > > on (BITS_PER_LONG != 32). Next patch of this series introduces
    > > ARCH_32BIT_OFF_T config option to force O_LARGEFILE for 64-bit arches,
    > > and all new 32-bit arches, as ARCH_32BIT_OFF_T is enabled for existing
    > > 32-bit arches explicitly.
    > >
    > > O_LARGEFILE is controlled like this:
    > > -#define force_o_largefile() (BITS_PER_LONG != 32)
    > > +#define force_o_largefile() (!IS_ENABLED(CONFIG_ARCH_32BIT_OFF_T))
    > >
    > > So if I restore original patch, everything will work. But my question
    > > is: if ARCH_32BIT_OFF_T disables O_LARGEFILE for tile32 anyway, what
    > > for we redirect native syscall handlers to compat ones? They are
    > > looking identical...
    >
    > I've lost context here, but let me try to recall what we had
    > discussed in the past:
    >
    > - native 32-bit architectures are handled using CONFIG_ARCH_32BIT_OFF_T
    > - native 64-bit architectures keep setting the flag.
    > - compat 32-bit architectures need special cases, but the only one
    > that exists is tile, which has to keep not setting O_LARGEFILE
    > while new compat architectures (ilp32) should set it.
    >
    > > If my understanding is correct, we can drop the change in
    > > arch/tile/kernel/compat.c and join this patch with next one in this
    > > series.
    > >
    > > Chris, Arnd?
    >
    > The change in arch/tile/kernel/compat.c can either come before the
    > below change, or in the same patch, but not later.
    >
    > Arnd

    Correct, I'll add it to this patch

    >
    > > > diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h
    > > > index a26415b..4dcc38d 100644
    > > > --- a/include/uapi/asm-generic/unistd.h
    > > > +++ b/include/uapi/asm-generic/unistd.h
    > > > @@ -178,7 +178,7 @@ __SYSCALL(__NR_fchownat, sys_fchownat)
    > > > #define __NR_fchown 55
    > > > __SYSCALL(__NR_fchown, sys_fchown)
    > > > #define __NR_openat 56
    > > > -__SC_COMP(__NR_openat, sys_openat, compat_sys_openat)
    > > > +__SYSCALL(__NR_openat, sys_openat)
    > > > #define __NR_close 57
    > > > __SYSCALL(__NR_close, sys_close)
    > > > #define __NR_vhangup 58
    > > > @@ -676,8 +676,7 @@ __SYSCALL(__NR_fanotify_mark, sys_fanotify_mark)
    > > > #define __NR_name_to_handle_at 264
    > > > __SYSCALL(__NR_name_to_handle_at, sys_name_to_handle_at)
    > > > #define __NR_open_by_handle_at 265
    > > > -__SC_COMP(__NR_open_by_handle_at, sys_open_by_handle_at, \
    > > > - compat_sys_open_by_handle_at)
    > > > +__SYSCALL(__NR_open_by_handle_at, sys_open_by_handle_at)
    > > > #define __NR_clock_adjtime 266
    > > > __SC_COMP(__NR_clock_adjtime, sys_clock_adjtime, compat_sys_clock_adjtime)
    > > > #define __NR_syncfs 267
    > >
    >

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