Re: [PATCH] lz4: fix KERNEL_LZ4 support

From: Andrew Morton
Date: Wed Feb 08 2017 - 17:30:57 EST


On Wed, 8 Feb 2017 22:19:23 +0100 Arnd Bergmann <arnd@xxxxxxxx> wrote:

> The updated lz4 library removed the #ifdef guards around the various
> EXPORT_SYMBOL statements in the original kernel lz4 support, which broke
> CONFIG_KERNEL_LZ4 on x86:
>
> x86_64-linux-ld: -r and -pie may not be used together
> scripts/Makefile.build:308: recipe for target 'arch/x86/boot/compressed/misc.o' failed
>
> This uses a simpler way to do the same thing, by overriding the
> EXPORT_SYMBOL macro.
>

hm, why does this CONFIG_KERNEL_LZ4 thing exist? What makes lz4
different from a billion other kernel modules?

> index 9bf918233749..a390f63bc475 100644
> --- a/lib/lz4/lz4_decompress.c
> +++ b/lib/lz4/lz4_decompress.c
> @@ -40,6 +40,11 @@
> #include <linux/kernel.h>
> #include <asm/unaligned.h>
>
> +#ifdef STATIC
> +#undef EXPORT_SYMBOL
> +#define EXPORT_SYMBOL(x)
> +#endif
> +

That is a bit hacky, and somewhat "surprising". Why not do it the old
fashioned way?

--- a/lib/lz4/lz4_decompress.c~lz4-fix-kernel_lz4-support-fix
+++ a/lib/lz4/lz4_decompress.c
@@ -328,7 +323,6 @@ int LZ4_decompress_safe(const char *sour
maxDecompressedSize, endOnInputSize, full, 0,
noDict, (BYTE *)dest, NULL, 0);
}
-EXPORT_SYMBOL(LZ4_decompress_safe);

int LZ4_decompress_safe_partial(const char *source, char *dest,
int compressedSize, int targetOutputSize, int maxDecompressedSize)
@@ -337,7 +331,6 @@ int LZ4_decompress_safe_partial(const ch
maxDecompressedSize, endOnInputSize, partial,
targetOutputSize, noDict, (BYTE *)dest, NULL, 0);
}
-EXPORT_SYMBOL(LZ4_decompress_safe_partial);

int LZ4_decompress_fast(const char *source, char *dest, int originalSize)
{
@@ -345,7 +338,6 @@ int LZ4_decompress_fast(const char *sour
endOnOutputSize, full, 0, withPrefix64k,
(BYTE *)(dest - 64 * KB), NULL, 64 * KB);
}
-EXPORT_SYMBOL(LZ4_decompress_fast);

int LZ4_setStreamDecode(LZ4_streamDecode_t *LZ4_streamDecode,
const char *dictionary, int dictSize)
@@ -358,7 +350,6 @@ int LZ4_setStreamDecode(LZ4_streamDecode
lz4sd->extDictSize = 0;
return 1;
}
-EXPORT_SYMBOL(LZ4_setStreamDecode);

/*
* *_continue() :
@@ -406,7 +397,6 @@ int LZ4_decompress_safe_continue(LZ4_str

return result;
}
-EXPORT_SYMBOL(LZ4_decompress_safe_continue);

int LZ4_decompress_fast_continue(LZ4_streamDecode_t *LZ4_streamDecode,
const char *source, char *dest, int originalSize)
@@ -441,7 +431,6 @@ int LZ4_decompress_fast_continue(LZ4_str

return result;
}
-EXPORT_SYMBOL(LZ4_decompress_fast_continue);

/*
* Advanced decoding functions :
@@ -478,7 +467,6 @@ int LZ4_decompress_safe_usingDict(const
return LZ4_decompress_usingDict_generic(source, dest,
compressedSize, maxOutputSize, 1, dictStart, dictSize);
}
-EXPORT_SYMBOL(LZ4_decompress_safe_usingDict);

int LZ4_decompress_fast_usingDict(const char *source, char *dest,
int originalSize, const char *dictStart, int dictSize)
@@ -486,7 +474,17 @@ int LZ4_decompress_fast_usingDict(const
return LZ4_decompress_usingDict_generic(source, dest, 0,
originalSize, 0, dictStart, dictSize);
}
+
+#ifndef STATIC
+EXPORT_SYMBOL(LZ4_decompress_safe);
+EXPORT_SYMBOL(LZ4_decompress_safe_partial);
+EXPORT_SYMBOL(LZ4_decompress_fast);
+EXPORT_SYMBOL(LZ4_setStreamDecode);
+EXPORT_SYMBOL(LZ4_decompress_safe_continue);
+EXPORT_SYMBOL(LZ4_decompress_fast_continue);
+EXPORT_SYMBOL(LZ4_decompress_safe_usingDict);
EXPORT_SYMBOL(LZ4_decompress_fast_usingDict);
+#endif

MODULE_LICENSE("Dual BSD/GPL");
MODULE_DESCRIPTION("LZ4 decompressor");
_