On Fri, 2016-12-02 at 13:40 +0100, Arnd Bergmann wrote: > With binutils-2.16 and before, a weak missing symbol was kept during the > final link, and a missing CRC for an export would lead to that CRC > being treated as zero implicitly. With binutils-2.17, the crc > symbol gets dropped, and any module trying to use it will fail to > load. > > This sets the weak CRC symbol to zero explicitly, making it defined > in vmlinux, which in turn lets us load the modules referring to > that CRC. > > The comment above the __CRC_SYMBOL macro suggests that this was > always the intention, although it also seems that all symbols > defined in C have a correct CRC these days, and only the exports > that are now done in assembly need this. > > > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > --- > Not sure if this is the correct way of doing it, but this seems trivial > enough and lets me build the kernel with missing CRCs with any binutils > version. I tried this along with Adam's patch on x86_64, with Debian's binutils 2.27.51.20161127. The result was that the kernel's __kcrctab held 0 for several symbols, even though there was type information in asm- prototypes.h and Module.symvers and the modules had a non-zero CRC for those symbols. With just Adam's patch, the kernel and modules agreed. Ben. > diff --git a/include/asm-generic/export.h b/include/asm-generic/export.h > index 63554e9..59a3b2f 100644 > --- a/include/asm-generic/export.h > +++ b/include/asm-generic/export.h > @@ -54,6 +54,7 @@ KSYM(__kstrtab_\name): > KSYM(__kcrctab_\name): > > __put KSYM(__crc_\name) > > .weak KSYM(__crc_\name) > > + .set KSYM(__crc_\name), 0 > > .previous > #endif > #endif > -- Ben Hutchings Absolutum obsoletum. (If it works, it's out of date.) - Stafford Beer
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