Messages in this thread | | | Subject | Re: [tip:perf/core] perf/x86: Fix USER/KERNEL tagging of samples | From | Peter Zijlstra <> | Date | Tue, 10 Jul 2012 09:54:08 +0200 |
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On Mon, 2012-07-09 at 20:41 +0200, Ingo Molnar wrote: > > +static unsigned long get_segment_base(unsigned int segment) > > +{ > > + struct desc_struct *desc; > > + int idx = segment >> 3; > > + > > + if ((segment & SEGMENT_TI_MASK) == SEGMENT_LDT) { > > + if (idx > LDT_ENTRIES) > > + return 0; > > + > > + desc = current->active_mm->context.ldt; > > + } else { > > + if (idx > GDT_ENTRIES) > > + return 0; > > + > > + desc = __this_cpu_ptr(&gdt_page.gdt[0]); > > + } > > + > > + return get_desc_base(desc + idx); > > Shouldn't idx be checked against active_mm->context.ldt.size, > not LDT_ENTRIES (which is really just an upper limit)?
Ah indeed, fixed that.
> > +static unsigned long code_segment_base(struct pt_regs *regs) > > +{ > > +#ifdef CONFIG_32BIT > > + if (user_mode(regs) && regs->cs != __USER_CS) > > + return get_segment_base(regs->cs); > > +#else > > + if (test_thread_flag(TIF_IA32)) { > > + if (user_mode(regs) && regs->cs != __USER32_CS) > > + return get_segment_base(regs->cs); > > + } > > +#endif > > + return 0; > > +} > > Will this do the right thing for x32 mode?
hpa? It looks like x32 has TIF_X32, but from the kernel's POV its really just another 64bit process, so as long as we don't trigger the TIF_IA32 case we'll just return 0.
set_personality_ia32() looks like TIF_IA32 and TIF_X32 are mutually exclusive, so I think we do the right thing.
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