linux/arch/arc/kernel/process.c, branch v4.1

Merge tag 'arc-4.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/vgupta/arc

2015-04-24T14:55:54Z

Pull ARC updates from Vineet Gupta: - perf fixes/improvements - misc cleanups * tag 'arc-4.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/vgupta/arc: ARC: perf: don't add code for impossible case ARC: perf: Rename DT binding to not confuse with power mgmt ARC: perf: add user space attribution in callchains ARC: perf: Add kernel callchain support ARC: perf: support cache hit/miss ratio ARC: perf: Add some comments/debug stuff ARC: perf: make @arc_pmu static global ARC: mem init spring cleaning - No functional changes ARC: Fix RTT boot printing ARC: fold __builtin_constant_p() into test_bit() ARC: rename unhandled exception handler ARC: cosmetic: Remove unused ECR bitfield masks ARC: Fix WRITE_BCR ARC: [nsimosci] Update defconfig arc: copy_thread(): rename 'arg' argument to 'kthread_arg'

whack-a-mole: no need to set_fs(USER_DS) in {start,flush}_thread()

2015-04-12T02:24:31Z

flush_old_exec() has already done that. Back on 2011 a bunch of instances like that had been kicked out, but that hadn't taken care of then-out-of-tree architectures, obviously, and they served as reinfection vector... Signed-off-by: Al Viro

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

2015-03-31T05:50:51Z

The 'arg' argument to copy_thread() is only ever used when forking a new kernel thread. Hence, rename it to 'kthread_arg' for clarity. Signed-off-by: Alex Dowad Signed-off-by: Vineet Gupta

ARC: Fix thread_saved_pc()

2015-02-27T05:29:34Z

The old implementation assumed that SP at the time of __switch_to() is right above pt_regs which is almost certainly not the case as there will be some stack build up between entry into kernel and leading up to __switch_to Signed-off-by: Vineet Gupta

ARC: make start_thread() out-of-line

2014-05-05T08:52:12Z

Helps move out ISA specific bits from a arch exported header Signed-off-by: Vineet Gupta

ARC: pt_regs update #5: Use real ECR for pt_regs->event vs. synth values

2013-06-26T08:34:48Z

pt_regs->event was set with artificial values to identify the low level system event (syscall trap / breakpoint trap / exceptions / interrupts) With r8 saving out of the way, the full word can be used to save real ECR (Exception Cause Register) which helps idenify the event naturally, including additional info such as cause code, param. Only for Interrupts, where ECR is not applicable, do we resort to synthetic non ECR values. SAVE_ALL_TRAP/EXCEPTIONS can now be merged as they both use ECR with different runtime values. The ptrace helpers now use the sub-fields of ECR to distinguish the events (e.g. vector 0x25 is trap, param 0 is syscall...) The following benefits will follow: (1) This centralizes the location of where ECR is saved and will allow the cleanup of task->thread.cause_code ECR placeholder which is set in non-uniform way. Then ARC VM code can safely rely on it being there for purpose of finer grained VM_EXEC dcache flush (based on exec fault: I-TLB Miss) (2) Further, ECR being passed around from low level handlers as arg can be eliminated as it is part of standard reg-file in pt_regs Signed-off-by: Vineet Gupta

ARC: pt_regs update #4: r25 saved/restored unconditionally

2013-06-22T13:53:25Z

(This is a VERY IMP change for low level interrupt/exception handling) ----------------------------------------------------------------------- WHAT ----------------------------------------------------------------------- * User 25 now saved in pt_regs->user_r25 (vs. tsk->thread_info.user_r25) * This allows Low level interrupt code to unconditionally save r25 (vs. the prev version which would only do it for U->K transition). Ofcourse for nested interrupts, only the pt_regs->user_r25 of bottom-most frame is useful. * simplifies the interrupt prologue/epilogue * Needed for ARCv2 ISA code and done here to keep design similar with ARCompact event handling ----------------------------------------------------------------------- WHY ------------------------------------------------------------------------- With CONFIG_ARC_CURR_IN_REG, r25 is used to cache "current" task pointer in kernel mode. So when entering kernel mode from User Mode - user r25 is specially safe-kept (it being a callee reg is NOT part of pt_regs which are saved by default on each interrupt/trap/exception) - r25 loaded with current task pointer. Further, if interrupt was taken in kernel mode, this is skipped since we know that r25 already has valid "current" pointer. With 2 level of interrupts in ARCompact ISA, detecting this is difficult but still possible, since we could be in kernel mode but r25 not already saved (in fact the stack itself might not have been switched). A. User mode B. L1 IRQ taken C. L2 IRQ taken (while on 1st line of L1 ISR) So in #C, although in kernel mode, r25 not saved (infact SP not switched at all) Given that ARcompact has manual stack switching, we could use a bit of trickey - The low level code would make sure that SP is only set to kernel mode value at the very end (after saving r25). So a non kernel mode SP, even if in kernel mode, meant r25 was NOT saved. The same paradigm won't work in ARCv2 ISA since SP is auto-switched so it's setting can't be delayed/constrained. Signed-off-by: Vineet Gupta

ARC: Increase readability of entry handlers

2013-06-22T13:53:23Z

* use artificial PUSH/POP contructs for CORE Reg save/restore to stack * use artificial PUSHAX/POPAX contructs for Auxiliary Space regs * macro'ize multiple copies of callee-reg-save/restore (SAVE_R13_TO_R24) * use BIC insn for inverse-and operation Signed-off-by: Vineet Gupta

ARC: pt_regs update #3: Remove unused gutter at start of callee_regs

2013-06-22T13:53:22Z

This is trickier than prev two: * context switching code saves kernel mode callee regs in the format of struct callee_regs thus needs adjustment. This also reduces the height of topmost kernel stack frame by 1 word. * Since kernel stack unwinder is sensitive to height of topmost kernel stack frame, that needs a word of adjustment too. ptrace needs a bit of updating since pt_regs now diverges from user_regs_struct. Signed-off-by: Vineet Gupta

ARC: pt_regs update #1: Align pt_regs end with end of kernel stack page

2013-06-22T13:53:21Z

Historically, pt_regs would end at offset of 1 word from end of stack page. ----------------- -> START of page (task->stack) | | | thread_info | ----------------- | | ^ ~ ~ | ~ ~ | | | | | | <---- pt_regs used to END here ----------------- | 1 word GUTTER | ----------------- -> End of page (START of kernel stack) This required special "one-off" considerations in low level code. The root cause is very likely assumption of "empty" SP by the original ARC kernel hackers, despite ARC700 always been "full" SP. So finally RIP one word gutter ! Signed-off-by: Vineet Gupta