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Date: Wed, 8 Feb 2017 23:06:34 +0100 From: Arnd Bergmann <arnd@...db.de> To: Andrew Morton <akpm@...ux-foundation.org> Cc: Sven Schmidt <4sschmid@...ormatik.uni-hamburg.de>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org> Subject: Re: [PATCH] lz4: fix KERNEL_LZ4 support On Wed, Feb 8, 2017 at 10:34 PM, Andrew Morton <akpm@...ux-foundation.org> wrote: > On Wed, 8 Feb 2017 22:19:23 +0100 Arnd Bergmann <arnd@...db.de> 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? This symbol means the kernel (bzImage) itself is compressed with lz4, an we include the lz4_decompress.c code from arch/x86/boot/compressed/misc.c >> 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? I was trying to keep the modification small, to simplify adding it the next time we update the lz4 library. > + > +#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 > This seems fine too, but then we probably want to keep the #ifndef around the MODULE_LICENSE()/MODULE_DESCRIPTION() macros as well, like we do in the other decompressors that we can use for boot image. lib/inflate.c also marks all functions as STATIC, but the other algorithms don't, so I'm not sure whether we should do the same here. Arnd
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