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Date: Mon, 14 Nov 2022 11:44:46 +1100
From: Alexey Kardashevskiy <aik@...abs.ru>
To: Masahiro Yamada <masahiroy@...nel.org>
Cc: linux-kernel@...r.kernel.org, Nick Terrell <terrelln@...com>,
Nick Desaulniers <ndesaulniers@...gle.com>,
Nathan Chancellor <nathan@...nel.org>,
Nicholas Piggin <npiggin@...il.com>,
kernel test robot <lkp@...el.com>
Subject: Re: [PATCH kernel v3] zstd: Fixing mixed module-builtin objects
On 12/11/2022 07:58, Masahiro Yamada wrote:
> On Thu, Sep 29, 2022 at 11:08 AM Alexey Kardashevskiy <aik@...abs.ru> wrote:
>>
>> With CONFIG_ZSTD_COMPRESS=m and CONFIG_ZSTD_DECOMPRESS=y we end up in
>> a situation when files from lib/zstd/common/ are compiled once to be
>> linked later for ZSTD_DECOMPRESS (build-in) and ZSTD_COMPRESS (module)
>> even though CFLAGS are different for builtins and modules.
>> So far somehow this was not a problem but enabling LLVM LTO exposes
>> the problem as:
>>
>> ld.lld: error: linking module flags 'Code Model': IDs have conflicting values in 'lib/built-in.a(zstd_common.o at 5868)' and 'ld-temp.o'
>>
>> This particular conflict is caused by KBUILD_CFLAGS=-mcmodel=medium vs.
>> KBUILD_CFLAGS_MODULE=-mcmodel=large , modules use the large model on
>> POWERPC as explained at
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/powerpc/Makefile?h=v5.18-rc4#n127
>> but the current use of common files is wrong anyway.
>
>
> BTW, how to reproduce this error?
>
> You referred to the arch/powerpc/Makefile,
> but ARCH=powerpc cannot enable Clang LTO.
> (powerpc does not select ARCH_SUPPORTS_LTO_CLANG).
I posted a patch for that a while back but it did not get much interest
as there appears to be an alternative to LTO which does not require the
compiler support, I forgot the name of that thing and changed the
employer since then so lost track of this entirely :)
https://patchwork.ozlabs.org/project/linuxppc-dev/patch/20220629083011.1763768-1-aik@ozlabs.ru/
>
>
>
>
>
>> This works around the issue by introducing a zstd_common module with
>> shared code.
>>
>> Cc: Masahiro Yamada <masahiroy@...nel.org>
>> Signed-off-by: Alexey Kardashevskiy <aik@...abs.ru>
>> [robot found a problem in v2]
>> Reported-by: kernel test robot <lkp@...el.com>
>> ---
>> Changes:
>> v3:
>> * added EXPORT_SYMBOL_GPL to compile with:
>> CONFIG_ZSTD_COMMON=m
>> CONFIG_ZSTD_COMPRESS=m
>> CONFIG_ZSTD_DECOMPRESS=m
>> Vast majority of cases have CONFIG_ZSTD_COMMON=y so this went unnoticed
>> ---
>> lib/zstd/Makefile | 18 ++++++++----------
>> lib/zstd/common/entropy_common.c | 5 ++++-
>> lib/zstd/common/zstd_common.c | 10 ++++++++++
>> lib/Kconfig | 8 ++++++--
>> 4 files changed, 28 insertions(+), 13 deletions(-)
>>
>> diff --git a/lib/zstd/Makefile b/lib/zstd/Makefile
>> index fc45339fc3a3..440bd0007ae2 100644
>> --- a/lib/zstd/Makefile
>> +++ b/lib/zstd/Makefile
>> @@ -10,14 +10,10 @@
>> # ################################################################
>> obj-$(CONFIG_ZSTD_COMPRESS) += zstd_compress.o
>> obj-$(CONFIG_ZSTD_DECOMPRESS) += zstd_decompress.o
>> +obj-$(CONFIG_ZSTD_COMMON) += zstd_common.o
>>
>> zstd_compress-y := \
>> zstd_compress_module.o \
>> - common/debug.o \
>> - common/entropy_common.o \
>> - common/error_private.o \
>> - common/fse_decompress.o \
>> - common/zstd_common.o \
>> compress/fse_compress.o \
>> compress/hist.o \
>> compress/huf_compress.o \
>> @@ -33,12 +29,14 @@ zstd_compress-y := \
>>
>> zstd_decompress-y := \
>> zstd_decompress_module.o \
>> - common/debug.o \
>> - common/entropy_common.o \
>> - common/error_private.o \
>> - common/fse_decompress.o \
>> - common/zstd_common.o \
>> decompress/huf_decompress.o \
>> decompress/zstd_ddict.o \
>> decompress/zstd_decompress.o \
>> decompress/zstd_decompress_block.o \
>> +
>> +zstd_common-y := \
>> + common/debug.o \
>> + common/entropy_common.o \
>> + common/error_private.o \
>> + common/fse_decompress.o \
>> + common/zstd_common.o \
>> diff --git a/lib/zstd/common/entropy_common.c b/lib/zstd/common/entropy_common.c
>> index 53b47a2b52ff..a311808c0d56 100644
>> --- a/lib/zstd/common/entropy_common.c
>> +++ b/lib/zstd/common/entropy_common.c
>> @@ -15,6 +15,7 @@
>> /* *************************************
>> * Dependencies
>> ***************************************/
>> +#include <linux/module.h>
>> #include "mem.h"
>> #include "error_private.h" /* ERR_*, ERROR */
>> #define FSE_STATIC_LINKING_ONLY /* FSE_MIN_TABLELOG */
>> @@ -239,7 +240,7 @@ size_t FSE_readNCount(
>> {
>> return FSE_readNCount_bmi2(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize, /* bmi2 */ 0);
>> }
>> -
>> +EXPORT_SYMBOL_GPL(FSE_readNCount);
>>
>> /*! HUF_readStats() :
>> Read compact Huffman tree, saved by HUF_writeCTable().
>> @@ -255,6 +256,7 @@ size_t HUF_readStats(BYTE* huffWeight, size_t hwSize, U32* rankStats,
>> U32 wksp[HUF_READ_STATS_WORKSPACE_SIZE_U32];
>> return HUF_readStats_wksp(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, wksp, sizeof(wksp), /* bmi2 */ 0);
>> }
>> +EXPORT_SYMBOL_GPL(HUF_readStats);
>>
>> FORCE_INLINE_TEMPLATE size_t
>> HUF_readStats_body(BYTE* huffWeight, size_t hwSize, U32* rankStats,
>> @@ -355,3 +357,4 @@ size_t HUF_readStats_wksp(BYTE* huffWeight, size_t hwSize, U32* rankStats,
>> (void)bmi2;
>> return HUF_readStats_body_default(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, workSpace, wkspSize);
>> }
>> +EXPORT_SYMBOL_GPL(HUF_readStats_wksp);
>> diff --git a/lib/zstd/common/zstd_common.c b/lib/zstd/common/zstd_common.c
>> index 3d7e35b309b5..0f1f63be25d9 100644
>> --- a/lib/zstd/common/zstd_common.c
>> +++ b/lib/zstd/common/zstd_common.c
>> @@ -13,6 +13,7 @@
>> /*-*************************************
>> * Dependencies
>> ***************************************/
>> +#include <linux/module.h>
>> #define ZSTD_DEPS_NEED_MALLOC
>> #include "zstd_deps.h" /* ZSTD_malloc, ZSTD_calloc, ZSTD_free, ZSTD_memset */
>> #include "error_private.h"
>> @@ -35,14 +36,17 @@ const char* ZSTD_versionString(void) { return ZSTD_VERSION_STRING; }
>> * tells if a return value is an error code
>> * symbol is required for external callers */
>> unsigned ZSTD_isError(size_t code) { return ERR_isError(code); }
>> +EXPORT_SYMBOL_GPL(ZSTD_isError);
>>
>> /*! ZSTD_getErrorName() :
>> * provides error code string from function result (useful for debugging) */
>> const char* ZSTD_getErrorName(size_t code) { return ERR_getErrorName(code); }
>> +EXPORT_SYMBOL_GPL(ZSTD_getErrorName);
>>
>> /*! ZSTD_getError() :
>> * convert a `size_t` function result into a proper ZSTD_errorCode enum */
>> ZSTD_ErrorCode ZSTD_getErrorCode(size_t code) { return ERR_getErrorCode(code); }
>> +EXPORT_SYMBOL_GPL(ZSTD_getErrorCode);
>>
>> /*! ZSTD_getErrorString() :
>> * provides error code string from enum */
>> @@ -59,6 +63,7 @@ void* ZSTD_customMalloc(size_t size, ZSTD_customMem customMem)
>> return customMem.customAlloc(customMem.opaque, size);
>> return ZSTD_malloc(size);
>> }
>> +EXPORT_SYMBOL_GPL(ZSTD_customMalloc);
>>
>> void* ZSTD_customCalloc(size_t size, ZSTD_customMem customMem)
>> {
>> @@ -71,6 +76,7 @@ void* ZSTD_customCalloc(size_t size, ZSTD_customMem customMem)
>> }
>> return ZSTD_calloc(1, size);
>> }
>> +EXPORT_SYMBOL_GPL(ZSTD_customCalloc);
>>
>> void ZSTD_customFree(void* ptr, ZSTD_customMem customMem)
>> {
>> @@ -81,3 +87,7 @@ void ZSTD_customFree(void* ptr, ZSTD_customMem customMem)
>> ZSTD_free(ptr);
>> }
>> }
>> +EXPORT_SYMBOL_GPL(ZSTD_customFree);
>> +
>> +MODULE_LICENSE("Dual BSD/GPL");
>> +MODULE_DESCRIPTION("Zstd Common");
>> diff --git a/lib/Kconfig b/lib/Kconfig
>> index dc1ab2ed1dc6..3ea8941ab18d 100644
>> --- a/lib/Kconfig
>> +++ b/lib/Kconfig
>> @@ -343,12 +343,16 @@ config LZ4HC_COMPRESS
>> config LZ4_DECOMPRESS
>> tristate
>>
>> +config ZSTD_COMMON
>> + select XXHASH
>> + tristate
>> +
>> config ZSTD_COMPRESS
>> - select XXHASH
>> + select ZSTD_COMMON
>> tristate
>>
>> config ZSTD_DECOMPRESS
>> - select XXHASH
>> + select ZSTD_COMMON
>> tristate
>>
>> source "lib/xz/Kconfig"
>> --
>> 2.37.3
>>
>
>
--
Alexey
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