On Sun, Feb 03, 2008 at 06:26:35PM +0100, Sam Ravnborg wrote: > On Sun, Feb 03, 2008 at 01:08:44PM +0000, Al Viro wrote: > > ; cat >a.c <<'EOF' > > const char foo[] __attribute__ ((__section__(".blah"))) = ""; > > const char * const bar __attribute__((__section__(".blah"))) = ""; > > EOF > > ; gcc -m32 -S a.c > > ; gcc -m64 -S a.c > > a.c:2: error: bar causes a section type conflict > > ; > > > > That's 4.1.2 on ppc. What happens is that the second declaration > > wants to make .blah writable. We actually trigger that in ppc64 > > builds on drivers/net/natsemi.c. > > > > Note that on ppc64 without explicit sections you have the second one land in > > .data.rel.ro.local, which is "aw",progbits. > > > > The reason why it didn't visibly bite us before is that usually __devinit... > > just expanded to nothing (unless you disable HOTPLUG, which requires > > EMBEDDED, which wasn't apparently common enough for ppc64 builds). > > > > Suggestions? > > Hi Al. > > __devinitconst were invented to cover this issue. > So use __devinitconst for const data and > __devinitdata for non-const data.
As the example above shows, what is and what is not const data is irrelevant. The data _is_ const. On ppc32 gcc is happy to put it into read-only section. On ppc64 the same version of gcc insists on making the section this data object is going to *writable*. > We recently had breakage in mainline with x86 64 bit > (sis190) for the exact same case. No, this is not exact same case. Unfortunately. > Does this work in your ppc example or do we need > to find another solution? Please, read the posted example. s/.blah/.devinit.rodata/ if you wish - it's not magical. What happens is that * gcc choice of r/o vs. r/w section is not determined by object being const * that choice is actually platform-dependent, even between related platforms (see ppc32 and ppc64 in the example above). -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/