lkml.org 
[lkml]   [2020]   [Jul]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH v6 1/8] lib: prepare zstd for preboot environment
    Date
    From: Nick Terrell <terrelln@fb.com>

    * Don't export symbols if ZSTD_PREBOOT is defined.
    * Remove a double definition of the CHECK_F macro when the zstd
    library is amalgamated.
    * Switch ZSTD_copy8() to __builtin_memcpy(), because in the preboot
    environment on x86 gcc can't inline `memcpy()` otherwise.
    * Limit the gcc hack in ZSTD_wildcopy() to the broken gcc version. See
    https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81388.

    These changes are necessary to get the build to work in the preboot
    environment, and to get reasonable performance. ZSTD_copy8() and
    ZSTD_wildcopy() are in the core of the zstd hot loop. So outlining
    these calls to memcpy(), and having an extra branch are very
    detrimental to performance.

    Reviewed-by: Kees Cook <keescook@chromium.org>
    Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
    Signed-off-by: Nick Terrell <terrelln@fb.com>
    ---
    lib/zstd/decompress.c | 2 ++
    lib/zstd/fse_decompress.c | 9 +--------
    lib/zstd/zstd_internal.h | 14 ++++++++++++--
    3 files changed, 15 insertions(+), 10 deletions(-)

    diff --git a/lib/zstd/decompress.c b/lib/zstd/decompress.c
    index 269ee9a796c1..73ded63278cf 100644
    --- a/lib/zstd/decompress.c
    +++ b/lib/zstd/decompress.c
    @@ -2490,6 +2490,7 @@ size_t ZSTD_decompressStream(ZSTD_DStream *zds, ZSTD_outBuffer *output, ZSTD_inB
    }
    }

    +#ifndef ZSTD_PREBOOT
    EXPORT_SYMBOL(ZSTD_DCtxWorkspaceBound);
    EXPORT_SYMBOL(ZSTD_initDCtx);
    EXPORT_SYMBOL(ZSTD_decompressDCtx);
    @@ -2529,3 +2530,4 @@ EXPORT_SYMBOL(ZSTD_insertBlock);

    MODULE_LICENSE("Dual BSD/GPL");
    MODULE_DESCRIPTION("Zstd Decompressor");
    +#endif
    diff --git a/lib/zstd/fse_decompress.c b/lib/zstd/fse_decompress.c
    index a84300e5a013..0b353530fb3f 100644
    --- a/lib/zstd/fse_decompress.c
    +++ b/lib/zstd/fse_decompress.c
    @@ -47,6 +47,7 @@
    ****************************************************************/
    #include "bitstream.h"
    #include "fse.h"
    +#include "zstd_internal.h"
    #include <linux/compiler.h>
    #include <linux/kernel.h>
    #include <linux/string.h> /* memcpy, memset */
    @@ -60,14 +61,6 @@
    enum { FSE_static_assert = 1 / (int)(!!(c)) }; \
    } /* use only *after* variable declarations */

    -/* check and forward error code */
    -#define CHECK_F(f) \
    - { \
    - size_t const e = f; \
    - if (FSE_isError(e)) \
    - return e; \
    - }
    -
    /* **************************************************************
    * Templates
    ****************************************************************/
    diff --git a/lib/zstd/zstd_internal.h b/lib/zstd/zstd_internal.h
    index 1a79fab9e13a..dac753397f86 100644
    --- a/lib/zstd/zstd_internal.h
    +++ b/lib/zstd/zstd_internal.h
    @@ -127,7 +127,14 @@ static const U32 OF_defaultNormLog = OF_DEFAULTNORMLOG;
    * Shared functions to include for inlining
    *********************************************/
    ZSTD_STATIC void ZSTD_copy8(void *dst, const void *src) {
    - memcpy(dst, src, 8);
    + /*
    + * zstd relies heavily on gcc being able to analyze and inline this
    + * memcpy() call, since it is called in a tight loop. Preboot mode
    + * is compiled in freestanding mode, which stops gcc from analyzing
    + * memcpy(). Use __builtin_memcpy() to tell gcc to analyze this as a
    + * regular memcpy().
    + */
    + __builtin_memcpy(dst, src, 8);
    }
    /*! ZSTD_wildcopy() :
    * custom version of memcpy(), can copy up to 7 bytes too many (8 bytes if length==0) */
    @@ -137,13 +144,16 @@ ZSTD_STATIC void ZSTD_wildcopy(void *dst, const void *src, ptrdiff_t length)
    const BYTE* ip = (const BYTE*)src;
    BYTE* op = (BYTE*)dst;
    BYTE* const oend = op + length;
    - /* Work around https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81388.
    +#if defined(GCC_VERSION) && GCC_VERSION >= 70000 && GCC_VERSION < 70200
    + /*
    + * Work around https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81388.
    * Avoid the bad case where the loop only runs once by handling the
    * special case separately. This doesn't trigger the bug because it
    * doesn't involve pointer/integer overflow.
    */
    if (length <= 8)
    return ZSTD_copy8(dst, src);
    +#endif
    do {
    ZSTD_copy8(op, ip);
    op += 8;
    --
    2.27.0
    \
     
     \ /
      Last update: 2020-07-07 05:53    [W:4.191 / U:0.704 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site