On Thu, 2016-02-25 at 14:17 +0100, Torsten Duwe wrote: > On Thu, Feb 25, 2016 at 01:28:25AM +1100, Michael Ellerman wrote: > > > > We can make that process easier by marking the generated stubs with a > > magic value, and then looking for that magic value. Altough this is not > > as rigorous as the current method, I believe it is sufficient in > > practice. > > The actual magic value is sort of debatable; it should be "improbable" > enough. But this can be changed easily, for each kernel compile, even.
Yeah. Given the locations we're trying to patch are computed in the first place from the mcount call sites, I feel like we don't need to be super paranoid here. The only time I've heard of this code (the current version) tripping up is when folks are hacking on ftrace. > > Signed-off-by: Michael Ellerman <m...@ellerman.id.au> > Reviewed-by: Torsten Duwe <d...@suse.de> > > [for reference:] > > +#define STUB_MAGIC 0x73747562 /* stub */ Which is one of: ori r21,r19,29811 andi. r20,r27,30050 Both of which are pretty improbable. They don't appear in any kernel I have around here. I have more plans for this code, which would hopefully mean we can get rid of the magic checking entirely. But I think this is OK for now. cheers _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
