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Subject[PATCH kernel v2] zstd: Fixing mixed module-builtin objects
Date
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.

This works around the issue by introducing a zstd_common module with
shared code.

Cc: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
Changes:
v2:
* add a new module instead of inlining common bits

---
lib/zstd/Makefile | 18 ++++++++----------
lib/zstd/common/entropy_common.c | 4 +++-
lib/zstd/common/zstd_common.c | 7 +++++++
lib/Kconfig | 8 ++++++--
4 files changed, 24 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..f84612627471 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,
diff --git a/lib/zstd/common/zstd_common.c b/lib/zstd/common/zstd_common.c
index 3d7e35b309b5..06f62b2026d5 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"
@@ -59,6 +60,7 @@ 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 +73,7 @@ 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 +84,7 @@ 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 087e06b4cdfd..33f3a7054cdd 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -333,12 +333,16 @@ 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"
--
2.30.2
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