lkml.org 
[lkml]   [2020]   [Aug]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    Date
    SubjectRe: [PATCH 2/4] Revert "lib/string.c: implement a basic bcmp"
    On Mon, Aug 17, 2020 at 10:44 PM Nathan Chancellor
    <natechancellor@gmail.com> wrote:
    >
    > On Mon, Aug 17, 2020 at 03:02:10PM -0700, Nick Desaulniers wrote:
    > > This reverts commit 5f074f3e192f10c9fade898b9b3b8812e3d83342.
    > >
    > > Use `-fno-builtin-bcmp` instead.
    > >
    > > The issue with using `-fno-builtin-*` flags was that they were not
    > > retained during an LTO link with LLVM. This was fixed in clang-11 by
    > > https://reviews.llvm.org/D71193
    > > (0508c994f0b14144041f2cfd3ba9f9a80f03de08), which is also the minimum
    > > supported version of clang for LTO.
    > >
    > > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
    > > ---
    > > Makefile | 1 +
    > > include/linux/string.h | 3 ---
    > > lib/string.c | 20 --------------------
    > > 3 files changed, 1 insertion(+), 23 deletions(-)
    > >
    > > diff --git a/Makefile b/Makefile
    > > index 211a1b6f6478..722ff5864275 100644
    > > --- a/Makefile
    > > +++ b/Makefile
    > > @@ -964,6 +964,7 @@ endif
    > > # to provide implementations of these routines, then prevent the compiler from
    > > # emitting calls to what will be undefined symbols.
    > > KBUILD_CFLAGS += -fno-builtin-stpcpy
    > > +KBUILD_CFLAGS += -fno-builtin-bcmp
    >
    > I personally think that this hunk should be its own patch before this
    > one then have this patch just be the revert, that way there is no
    > regression across a bisect (if one were to ever occur) and so the revert
    > is a straight 'git revert', rather than have something else mixed in
    > that requires reading the actual changelog text.
    >
    > No objections if you disagree though.

    That's a great idea. I considered it before sending, but I think it
    would be interesting to divorce the KBUILD changes which can be picked
    up quickly from the latter changes. Will send a V2.

    >
    > > # include additional Makefiles when needed
    > > include-y := scripts/Makefile.extrawarn
    > > diff --git a/include/linux/string.h b/include/linux/string.h
    > > index b1f3894a0a3e..f3bdb74bc230 100644
    > > --- a/include/linux/string.h
    > > +++ b/include/linux/string.h
    > > @@ -155,9 +155,6 @@ extern void * memscan(void *,int,__kernel_size_t);
    > > #ifndef __HAVE_ARCH_MEMCMP
    > > extern int memcmp(const void *,const void *,__kernel_size_t);
    > > #endif
    > > -#ifndef __HAVE_ARCH_BCMP
    > > -extern int bcmp(const void *,const void *,__kernel_size_t);
    > > -#endif
    > > #ifndef __HAVE_ARCH_MEMCHR
    > > extern void * memchr(const void *,int,__kernel_size_t);
    > > #endif
    > > diff --git a/lib/string.c b/lib/string.c
    > > index 6012c385fb31..69328b8353e1 100644
    > > --- a/lib/string.c
    > > +++ b/lib/string.c
    > > @@ -922,26 +922,6 @@ __visible int memcmp(const void *cs, const void *ct, size_t count)
    > > EXPORT_SYMBOL(memcmp);
    > > #endif
    > >
    > > -#ifndef __HAVE_ARCH_BCMP
    > > -/**
    > > - * bcmp - returns 0 if and only if the buffers have identical contents.
    > > - * @a: pointer to first buffer.
    > > - * @b: pointer to second buffer.
    > > - * @len: size of buffers.
    > > - *
    > > - * The sign or magnitude of a non-zero return value has no particular
    > > - * meaning, and architectures may implement their own more efficient bcmp(). So
    > > - * while this particular implementation is a simple (tail) call to memcmp, do
    > > - * not rely on anything but whether the return value is zero or non-zero.
    > > - */
    > > -#undef bcmp
    > > -int bcmp(const void *a, const void *b, size_t len)
    > > -{
    > > - return memcmp(a, b, len);
    > > -}
    > > -EXPORT_SYMBOL(bcmp);
    > > -#endif
    > > -
    > > #ifndef __HAVE_ARCH_MEMSCAN
    > > /**
    > > * memscan - Find a character in an area of memory.
    > > --
    > > 2.28.0.220.ged08abb693-goog
    > >
    >
    > Cheers,
    > Nathan



    --
    Thanks,
    ~Nick Desaulniers

    \
     
     \ /
      Last update: 2020-08-18 20:01    [W:5.906 / U:0.020 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site