[Aboriginal] Sparc-32 doesn't work in 3.1.
eric.dumazet at gmail.com
Wed Dec 14 09:49:55 PST 2011
Le mercredi 14 décembre 2011 à 20:42 +0300, Sergei Trofimovich a écrit :
> [ CCed Jakub ]
> >>> Boot time fixup v1.6. 4/Mar/98 Jakub Jelinek (jj at ultra.linux.cz).
> >>> Patching kernel for srmmu[Fujitsu TurboSparc]/iommu
> >>> Fixup i f029ddfc doesn't refer to a valid instruction at
> >>> f00de648[95eea000]
> >>> halt, power off
> > I put the broken image up at http://landley.net/sparc-image for the
> > moment, but if you build 3.1 with the attached .config and the toolchain
> > mentioned last time, it should reproduce for you. It's 100% reliable
> > for me...
> Nice! With this config it breaks for me on your and mine toolchains.
> The offending function is ext4_kvmalloc (and similar ext4_kvzalloc).
> The usual relocation in sparc looks like a pair of instructions loading
> two pats of address in 2 instructions:
> Like that:
> > sethi %hi(ext4_fill_super), %o4 !, tmp113
> > or %o4, %lo(ext4_fill_super), %o4 ! tmp113,, tmp28
> In our case relocatable symbol sits in tail call, so %lo part is in "unusual"
> RESTORE instruction:
> > ext4_kvmalloc:
> > sethi %hi(___i_page_kernel), %i2 !, tmp112
> > call __vmalloc, 0 !
> > restore %i2, %lo(___i_page_kernel), %o2 ! tmp112,,
> David: is this code correct? Or it's a compiler bug? I am sparc32 newbie.
> (C source and asm sources of function are in )
> I think this kind of code is generated only in -Os.
> So to workaround it I tried this hack:
> > --- a/fs/ext4/super.c
> > +++ b/fs/ext4/super.c
> > ret = kmalloc(size, flags);
> > if (!ret)
> > ret = __vmalloc(size, flags, PAGE_KERNEL);
> > +
> > + asm __volatile__("nop":::"memory");
> > +
> > return ret;
> > }
> (for both ext4_kvmalloc / ext4_kvzalloc. Attached workaround as a patch.)
> It forces compiler to geterate "usual" pattern for relocation.
> I think of 2 solutions:
> 1. trying to fix sparc/boot/btfixupprep.c and arch/sparc/mm/btfixup.c
> to distinct HI22 and LO10 relocations as different ones.
> Right now they are merged into one 'i' type and rely on instruction heuristics to fix it.
> 2. Add a hack to arch/sparc/mm/btfixup.c to recognize restore instruction as well
> Any others?
3) Adding a memset() in ext4_kvmalloc() and ext4_kvzalloc() to prefault
4) (Unrelated) : add __GFP_HIGHMEM to __vmalloc() flags, so that high
memory pages can be used for large allocations.
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