Messages in this thread | | | Date | Thu, 25 Feb 2016 14:52:05 +0100 | From | Torsten Duwe <> | Subject | Re: [PATCH 04/12] powerpc/ftrace: Prepare for -mprofile-kernel |
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On Thu, Feb 25, 2016 at 01:28:27AM +1100, Michael Ellerman wrote: > @@ -450,17 +448,44 @@ static unsigned long stub_for_addr(const Elf64_Shdr *sechdrs, > return (unsigned long)&stubs[i]; > } > > +#ifdef CC_USING_MPROFILE_KERNEL > +static int is_early_mcount_callsite(u32 *instruction) > +{ > + /* -mprofile-kernel sequence starting with > + * mflr r0 and maybe std r0, LRSAVE(r1). > + */ > + if ((instruction[-3] == PPC_INST_MFLR && > + instruction[-2] == PPC_INST_STD_LR) || > + instruction[-2] == PPC_INST_MFLR) { > + /* Nothing to be done here, it's an _mcount > + * call location and r2 will have to be > + * restored in the _mcount function. > + */ > + return 1; > + } > + return 0; > +} > +#else
*You* said this might page fault :)
Did we agree yet whether we insist on a streamlined compiler? (GCC commit e95d0248dace required)?
If not: if (instruction[-2] == PPC_INST_STD_LR) { if (instruction[-3] == PPC_INST_MFLR) return 1; } else if (instruction[-2] == PPC_INST_MFLR) return 1; return 0;
leaves less freedom for the compiler to "optimise".
Signed-off-by: Torsten Duwe <duwe@suse.de>
Torsten
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