linux/arch/mips/kernel/process.c, branch v4.5

MIPS: Properly disable FPU in start_thread()

2016-02-01T22:36:03Z

start_thread() (called for execve(2)) clears the TIF_USEDFPU flag without atomically disabling the FPU. With a preemptive kernel, an unfortunately timed preemption after this could result in another task (or KVM guest) being scheduled in with the FPU still enabled, since lose_fpu_inatomic() only turns it off if TIF_USEDFPU is set. Use lose_fpu(0) instead of the separate FPU / MSA management, which should do the right thing (drop FPU properly and atomically without saving state) and will be more future proof. Signed-off-by: James Hogan Reviewed-by: Paul Burton Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/12302/ Signed-off-by: Ralf Baechle

Merge tag 'cpumask-next-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux

2015-04-20T17:19:03Z

Pull final removal of deprecated cpus_* cpumask functions from Rusty Russell: "This is the final removal (after several years!) of the obsolete cpus_* functions, prompted by their mis-use in staging. With these function removed, all cpu functions should only iterate to nr_cpu_ids, so we finally only allocate that many bits when cpumasks are allocated offstack" * tag 'cpumask-next-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux: (25 commits) cpumask: remove __first_cpu / __next_cpu cpumask: resurrect CPU_MASK_CPU0 linux/cpumask.h: add typechecking to cpumask_test_cpu cpumask: only allocate nr_cpumask_bits. Fix weird uses of num_online_cpus(). cpumask: remove deprecated functions. mips: fix obsolete cpumask_of_cpu usage. x86: fix more deprecated cpu function usage. ia64: remove deprecated cpus_ usage. powerpc: fix deprecated CPU_MASK_CPU0 usage. CPU_MASK_ALL/CPU_MASK_NONE: remove from deprecated region. staging/lustre/o2iblnd: Don't use cpus_weight staging/lustre/libcfs: replace deprecated cpus_ calls with cpumask_ staging/lustre/ptlrpc: Do not use deprecated cpus_* functions blackfin: fix up obsolete cpu function usage. parisc: fix up obsolete cpu function usage. tile: fix up obsolete cpu function usage. arm64: fix up obsolete cpu function usage. mips: fix up obsolete cpu function usage. x86: fix up obsolete cpu function usage. ...

mips: copy_thread(): rename 'arg' argument to 'kthread_arg'

2015-03-24T14:15:34Z

The 'arg' argument to copy_thread() is only ever used when forking a new kernel thread. Hence, rename it to 'kthread_arg' for clarity (and consistency with do_fork() and other arch-specific implementations of copy_thread()). Signed-off-by: Alex Dowad Cc: linux-kernel@vger.kernel.org Cc: Paul Burton Cc: Alex Smith Cc: Markos Chandras Cc: James Hogan Cc: Eunbong Song Cc: linux-mips@linux-mips.org (open list:MIPS) Patchwork: https://patchwork.linux-mips.org/patch/9546/ Signed-off-by: Ralf Baechle

mips: fix up obsolete cpu function usage.

2015-03-05T04:55:06Z

Thanks to spatch, plus manual removal of "&*". Then a sweep for for_each_cpu_mask => for_each_cpu. Signed-off-by: Rusty Russell Cc: Ralf Baechle Cc: Kevin Cernekee Cc: Florian Fainelli Cc: linux-mips@linux-mips.org

Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus

2015-02-22T03:41:38Z

Pull MIPS updates from Ralf Baechle: "This is the main pull request for MIPS: - a number of fixes that didn't make the 3.19 release. - a number of cleanups. - preliminary support for Cavium's Octeon 3 SOCs which feature up to 48 MIPS64 R3 cores with FPU and hardware virtualization. - support for MIPS R6 processors. Revision 6 of the MIPS architecture is a major revision of the MIPS architecture which does away with many of original sins of the architecture such as branch delay slots. This and other changes in R6 require major changes throughout the entire MIPS core architecture code and make up for the lion share of this pull request. - finally some preparatory work for eXtendend Physical Address support, which allows support of up to 40 bit of physical address space on 32 bit processors" [ Ahh, MIPS can't leave the PAE brain damage alone. It's like every CPU architect has to make that mistake, but pee in the snow by changing the TLA. But whether it's called PAE, LPAE or XPA, it's horrid crud - Linus ] * 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus: (114 commits) MIPS: sead3: Corrected get_c0_perfcount_int MIPS: mm: Remove dead macro definitions MIPS: OCTEON: irq: add CIB and other fixes MIPS: OCTEON: Don't do acknowledge operations for level triggered irqs. MIPS: OCTEON: More OCTEONIII support MIPS: OCTEON: Remove setting of processor specific CVMCTL icache bits. MIPS: OCTEON: Core-15169 Workaround and general CVMSEG cleanup. MIPS: OCTEON: Update octeon-model.h code for new SoCs. MIPS: OCTEON: Implement DCache errata workaround for all CN6XXX MIPS: OCTEON: Add little-endian support to asm/octeon/octeon.h MIPS: OCTEON: Implement the core-16057 workaround MIPS: OCTEON: Delete unused COP2 saving code MIPS: OCTEON: Use correct instruction to read 64-bit COP0 register MIPS: OCTEON: Save and restore CP2 SHA3 state MIPS: OCTEON: Fix FP context save. MIPS: OCTEON: Save/Restore wider multiply registers in OCTEON III CPUs MIPS: boot: Provide more uImage options MIPS: Remove unneeded #ifdef __KERNEL__ from asm/processor.h MIPS: ip22-gio: Remove legacy suspend/resume support mips: pci: Add ifdef around pci_proc_domain ...

MIPS: kernel: process: Do not allow FR=0 on MIPS R6

2015-02-17T15:37:38Z

A prctl() call to set FR=0 for MIPS R6 should not be allowed since FR=1 is the only option for R6 cores. Cc: Paul Burton Cc: Matthew Fortune Signed-off-by: Markos Chandras

MIPS,prctl: add PR_[GS]ET_FP_MODE prctl options for MIPS

2015-02-12T11:30:29Z

Userland code may be built using an ABI which permits linking to objects that have more restrictive floating point requirements. For example, userland code may be built to target the O32 FPXX ABI. Such code may be linked with other FPXX code, or code built for either one of the more restrictive FP32 or FP64. When linking with more restrictive code, the overall requirement of the process becomes that of the more restrictive code. The kernel has no way to know in advance which mode the process will need to be executed in, and indeed it may need to change during execution. The dynamic loader is the only code which will know the overall required mode, and so it needs to have a means to instruct the kernel to switch the FP mode of the process. This patch introduces 2 new options to the prctl syscall which provide such a capability. The FP mode of the process is represented as a simple bitmask combining a number of mode bits mirroring those present in the hardware. Userland can either retrieve the current FP mode of the process: mode = prctl(PR_GET_FP_MODE); or modify the current FP mode of the process: err = prctl(PR_SET_FP_MODE, new_mode); Signed-off-by: Paul Burton Cc: Matthew Fortune Cc: Markos Chandras Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/8899/ Signed-off-by: Ralf Baechle

MIPS: fork: Fix MSA/FPU/DSP context duplication race

2015-01-30T23:44:19Z

There is a race in the MIPS fork code which allows the child to get a stale copy of parent MSA/FPU/DSP state that is active in hardware registers when the fork() is called. This is because copy_thread() saves the live register state into the child context only if the hardware is currently in use, apparently on the assumption that the hardware state cannot have been saved and disabled since the initial duplication of the task_struct. However preemption is certainly possible during this window. An example sequence of events is as follows: 1) The parent userland process puts important data into saved floating point registers ($f20-$f31), which are then dirty compared to the process' stored context. 2) The parent process calls fork() which does a clone system call. 3) In the kernel, do_fork() -> copy_process() -> dup_task_struct() -> arch_dup_task_struct() (which uses the weakly defined default implementation). This duplicates the parent process' task context, which includes a stale version of its FP context from when it was last saved, probably some time before (1). 4) At some point before copy_process() calls copy_thread(), such as when duplicating the memory map, the process is desceduled. Perhaps it is preempted asynchronously, or perhaps it sleeps while blocked on a mutex. The dirty FP state in the FP registers is saved to the parent process' context and the FPU is disabled. 5) When the process is rescheduled again it continues copying state until it gets to copy_thread(), which checks whether the FPU is in use, so that it can copy that dirty state to the child process' task context. Because of the deschedule however the FPU is not in use, so the child process' context is left with stale FP context from the last time the parent saved it (some time before (1)). 6) When the new child process is scheduled it reads the important data from the saved floating point register, and ends up doing a NULL pointer dereference as a result of the stale data. This use of saved floating point registers across function calls can be triggered fairly easily by explicitly using inline asm with a current (MIPS R2) compiler, but is far more likely to happen unintentionally with a MIPS R6 compiler where the FP registers are more likely to get used as scratch registers for storing non-fp data. It is easily fixed, in the same way that other architectures do it, by overriding the implementation of arch_dup_task_struct() to sync the dirty hardware state to the parent process' task context *prior* to duplicating it, rather than copying straight to the child process' task context in copy_thread(). Note, the FPU hardware is not disabled so the parent process may continue executing with the live register context, but now the child process is guaranteed to have an identical copy of it at that point. Signed-off-by: James Hogan Reported-by: Matthew Fortune Tested-by: Markos Chandras Cc: Ralf Baechle Cc: Paul Burton Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/9075/ Signed-off-by: Ralf Baechle

MIPS: Add arch_trigger_all_cpu_backtrace() function

2014-11-24T06:44:49Z

Currently, arch_trigger_all_cpu_backtrace() is defined in only x86 and sparc which have an NMI. But in case of softlockup, it could be possible to dump backtrace of all cpus. and this could be helpful for debugging. for example, if system has 2 cpus. CPU 0 CPU 1 acquire read_lock() try to do write_lock() ,,, missing read_unlock() In this case, softlockup will occur becasuse CPU 0 does not call read_unlock(). And dump_stack() print only backtrace for "CPU 0". If CPU1's backtrace is printed it's very helpful. [ralf@linux-mips.org: Fixed whitespace and formatting issues.] Signed-off-by: Ralf Baechle Cc: linux-mips@linux-mips.org Cc: linux-kernel@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/8200/

MIPS: Remove useless parentheses

2014-11-24T06:44:49Z

Based on the spatch @@ expression e; @@ - return (e); + return e; with heavy hand editing because some of the changes are either whitespace or identation only or result in excessivly long lines. Signed-off-by: Ralf Baechle