On Tue, May 12, 2015 at 02:28:23PM -0300, Ezequiel Garcia wrote:
>
>
> On 05/12/2015 11:20 AM, Maciej W. Rozycki wrote:
> > Fix "BUG: using smp_processor_id() in preemptible" reported in accesses
> > to thread's FPU defaults: the value to initialise FSCR to at program
> > startup, the FCSR r/w mask and the contents of FIR in full FPU
> > emulation, removing a regression introduced with 9b26616c [MIPS: Respect
> > the ISA level in FCSR handling] and f6843626 [MIPS: math-emu: Set FIR
> > feature flags for full emulation].
> >
> > Use `boot_cpu_data' to obtain the data from, following the approach that
> > `cpu_has_*' macros take and avoiding the call to `smp_processor_id' made
> > in the reference to `current_cpu_data'. The contents of FSCR have to be
> > consistent across processors in an SMP system, the settings there must
> > not change as a thread is migrated across processors. And the contents
> > of FIR are guaranteed to be consistent in FPU emulation, by definition.
> >
> > Signed-off-by: Maciej W. Rozycki <macro@xxxxxxxxxxxxxx>
> > ---
> > Changes from v1:
> >
> > - also fix PTRACE_SETFPREGS (thanks, Paul!).
> >
> > Paul, Ezequiel --
> >
> > Can you verify this change addresses the problems you saw?
> >
>
> Tested-by: Ezequiel Garcia <ezequiel.garcia@xxxxxxxxxx>
Tested-by: Paul Martin <paul.martin@xxxxxxxxxxxxxxx>
>
> > [Ralf, this is another 4.1 material, please push it to Linus ASAP, once
> > this has been confirmed to DTRT.]
> >
> > Thanks,
> >
> > Maciej
> >
> > linux-mips-emu-fcsr-isa-fix.diff
> > Index: linux-org-test/arch/mips/include/asm/elf.h
> > ===================================================================
> > --- linux-org-test.orig/arch/mips/include/asm/elf.h 2015-05-06 23:20:51.946503000 +0100
> > +++ linux-org-test/arch/mips/include/asm/elf.h 2015-05-12 14:37:14.169350000 +0100
> > @@ -304,7 +304,7 @@ do { \
> > \
> > current->thread.abi = &mips_abi; \
> > \
> > - current->thread.fpu.fcr31 = current_cpu_data.fpu_csr31; \
> > + current->thread.fpu.fcr31 = boot_cpu_data.fpu_csr31; \
> > } while (0)
> >
> > #endif /* CONFIG_32BIT */
> > @@ -366,7 +366,7 @@ do { \
> > else \
> > current->thread.abi = &mips_abi; \
> > \
> > - current->thread.fpu.fcr31 = current_cpu_data.fpu_csr31; \
> > + current->thread.fpu.fcr31 = boot_cpu_data.fpu_csr31; \
> > \
> > p = personality(current->personality); \
> > if (p != PER_LINUX32 && p != PER_LINUX) \
> > Index: linux-org-test/arch/mips/kernel/ptrace.c
> > ===================================================================
> > --- linux-org-test.orig/arch/mips/kernel/ptrace.c 2015-04-28 14:52:04.000000000 +0100
> > +++ linux-org-test/arch/mips/kernel/ptrace.c 2015-05-12 15:12:03.511002000 +0100
> > @@ -176,7 +176,7 @@ int ptrace_setfpregs(struct task_struct
> >
> > __get_user(value, data + 64);
> > fcr31 = child->thread.fpu.fcr31;
> > - mask = current_cpu_data.fpu_msk31;
> > + mask = boot_cpu_data.fpu_msk31;
> > child->thread.fpu.fcr31 = (value & ~mask) | (fcr31 & mask);
> >
> > /* FIR may not be written. */
> > Index: linux-org-test/arch/mips/math-emu/cp1emu.c
> > ===================================================================
> > --- linux-org-test.orig/arch/mips/math-emu/cp1emu.c 2015-04-28 14:52:04.000000000 +0100
> > +++ linux-org-test/arch/mips/math-emu/cp1emu.c 2015-05-12 14:41:06.308256000 +0100
> > @@ -889,7 +889,7 @@ static inline void cop1_cfc(struct pt_re
> > break;
> >
> > case FPCREG_RID:
> > - value = current_cpu_data.fpu_id;
> > + value = boot_cpu_data.fpu_id;
> > break;
> >
> > default:
> > @@ -921,7 +921,7 @@ static inline void cop1_ctc(struct pt_re
> > (void *)xcp->cp0_epc, MIPSInst_RT(ir), value);
> >
> > /* Preserve read-only bits. */
> > - mask = current_cpu_data.fpu_msk31;
> > + mask = boot_cpu_data.fpu_msk31;
> > fcr31 = (value & ~mask) | (fcr31 & mask);
> > break;
> >
> >
>
--
Paul Martin http://www.codethink.co.uk/
Senior Software Developer, Codethink Ltd.
